Science.gov

Sample records for field-induced continuum lowering

  1. Continuum lowering - A new perspective

    NASA Astrophysics Data System (ADS)

    Crowley, B. J. B.

    2014-12-01

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

  2. Direct extraction of intense-field-induced polarization in the continuum on the attosecond time scale from transient absorption

    NASA Astrophysics Data System (ADS)

    Li, X.; Haxton, D. J.; Gaarde, M. B.; Schafer, K. J.; McCurdy, C. W.

    2016-02-01

    A procedure is suggested for using transient absorption spectroscopy above the ionization threshold to measure the polarization of the continuum induced by an intense optical pulse. In this way transient absorption measurement can be used to probe subfemtosecond intense field dynamics in atoms and molecules. The method is based on an approximation to the dependence of these spectra on time delay between an attosecond XUV probe pulse and an intense pump pulse that is tested over a wide range of intensities and time delays by all-electrons-active calculations using the multiconfiguration time-dependent Hartree-Fock method in the case of neon.

  3. Proposal for direct measurement of intense-field induced polarization in the continuum on the attosecond time scale using transient absorption

    NASA Astrophysics Data System (ADS)

    McCurdy, C. William; Haxton, Daniel; Li, Xuan

    2015-05-01

    A procedure is proposed for using transient absorption spectroscopy above the ionization threshold to measure the polarization of the continuum induced by an intense optical pulse. In this way transient absorption measurement can be used to probe sub-femtosecond intense field dynamics in atoms and molecules and extract the high frequency polarization that plays a central role in high harmonic generation. The method is based on a robust approximation to the dependence of these spectra on time-delay between an attosecond XUV probe pulse and an intense pump pulse that is verified over a wide range of intensities and time delays by all-electrons-active calculations using the Multiconfiguration Time-Dependent Hartree Fock method. To demonstrate the extraction of the field-induced polarization, we study the transient absorption spectrum of atomic Neon. Work at LBNL supported by USDOE, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, and work at UC Davis supported by USDOE grant No. DESC0007182.

  4. Measurements of continuum lowering in solid-density plasmas created from elements and compounds

    NASA Astrophysics Data System (ADS)

    Ciricosta, O.; Vinko, S. M.; Barbrel, B.; Rackstraw, D. S.; Preston, T. R.; Burian, T.; Chalupský, J.; Cho, B. I.; Chung, H.-K.; Dakovski, G. L.; Engelhorn, K.; Hájková, V.; Heimann, P.; Holmes, M.; Juha, L.; Krzywinski, J.; Lee, R. W.; Toleikis, S.; Turner, J. J.; Zastrau, U.; Wark, J. S.

    2016-05-01

    The effect of a dense plasma environment on the energy levels of an embedded ion is usually described in terms of the lowering of its continuum level. For strongly coupled plasmas, the phenomenon is intimately related to the equation of state; hence, an accurate treatment is crucial for most astrophysical and inertial-fusion applications, where the case of plasma mixtures is of particular interest. Here we present an experiment showing that the standard density-dependent analytical models are inadequate to describe solid-density plasmas at the temperatures studied, where the reduction of the binding energies for a given species is unaffected by the different plasma environment (ion density) in either the element or compounds of that species, and can be accurately estimated by calculations only involving the energy levels of an isolated neutral atom. The results have implications for the standard approaches to the equation of state calculations.

  5. Measurements of continuum lowering in solid-density plasmas created from elements and compounds.

    PubMed

    Ciricosta, O; Vinko, S M; Barbrel, B; Rackstraw, D S; Preston, T R; Burian, T; Chalupský, J; Cho, B I; Chung, H-K; Dakovski, G L; Engelhorn, K; Hájková, V; Heimann, P; Holmes, M; Juha, L; Krzywinski, J; Lee, R W; Toleikis, S; Turner, J J; Zastrau, U; Wark, J S

    2016-01-01

    The effect of a dense plasma environment on the energy levels of an embedded ion is usually described in terms of the lowering of its continuum level. For strongly coupled plasmas, the phenomenon is intimately related to the equation of state; hence, an accurate treatment is crucial for most astrophysical and inertial-fusion applications, where the case of plasma mixtures is of particular interest. Here we present an experiment showing that the standard density-dependent analytical models are inadequate to describe solid-density plasmas at the temperatures studied, where the reduction of the binding energies for a given species is unaffected by the different plasma environment (ion density) in either the element or compounds of that species, and can be accurately estimated by calculations only involving the energy levels of an isolated neutral atom. The results have implications for the standard approaches to the equation of state calculations. PMID:27210741

  6. Measurements of continuum lowering in solid-density plasmas created from elements and compounds

    PubMed Central

    Ciricosta, O.; Vinko, S. M.; Barbrel, B.; Rackstraw, D. S.; Preston, T. R.; Burian, T.; Chalupský, J.; Cho, B. I.; Chung, H. -K.; Dakovski, G. L.; Engelhorn, K.; Hájková, V.; Heimann, P.; Holmes, M.; Juha, L.; Krzywinski, J.; Lee, R. W.; Toleikis, S.; Turner, J. J.; Zastrau, U.; Wark, J. S.

    2016-01-01

    The effect of a dense plasma environment on the energy levels of an embedded ion is usually described in terms of the lowering of its continuum level. For strongly coupled plasmas, the phenomenon is intimately related to the equation of state; hence, an accurate treatment is crucial for most astrophysical and inertial-fusion applications, where the case of plasma mixtures is of particular interest. Here we present an experiment showing that the standard density-dependent analytical models are inadequate to describe solid-density plasmas at the temperatures studied, where the reduction of the binding energies for a given species is unaffected by the different plasma environment (ion density) in either the element or compounds of that species, and can be accurately estimated by calculations only involving the energy levels of an isolated neutral atom. The results have implications for the standard approaches to the equation of state calculations. PMID:27210741

  7. Measurements of continuum lowering in solid-density plasmas created from elements and compounds

    DOE PAGESBeta

    Ciricosta, O.; Vinko, S. M.; Barbrel, B.; Rackstraw, D. S.; Preston, T. R.; Burian, T.; Chalupský, J.; Cho, B. I.; Chung, H. -K.; Dakovski, G. L.; et al

    2016-05-23

    The effect of a dense plasma environment on the energy levels of an embedded ion is usually described in terms of the lowering of its continuum level. For strongly coupled plasmas, the phenomenon is intimately related to the equation of state; hence, an accurate treatment is crucial for most astrophysical and inertial-fusion applications, where the case of plasma mixtures is of particular interest. In this study, we present an experiment showing that the standard density-dependent analytical models are inadequate to describe solid-density plasmas at the temperatures studied, where the reduction of the binding energies for a given species is unaffectedmore » by the different plasma environment (ion density) in either the element or compounds of that species, and can be accurately estimated by calculations only involving the energy levels of an isolated neutral atom. Lastly, the results have implications for the standard approaches to the equation of state calculations.« less

  8. Experimental Measurements and Density Functional Theory Calculations of Continuum Lowering in Strongly Coupled Plasmas

    NASA Astrophysics Data System (ADS)

    Vinko, Sam

    2014-10-01

    An accurate description of the ionization potential depression (IPD) of ions in plasmas due to their interaction with the environment is a fundamental problem in plasma physics, playing a key role in determining the ionization balance, charge state distribution, opacity and plasma equation of state. Here I present the first experimental investigation of the IPD as a function of ionic charge state in a range of dense Mg, Al and Si plasmas, using the Linac Coherent Light Source X-ray free-electron laser. The measurements show significantly larger IPDs than are predicted by the most commonly used models, such as that of Stewart-Pyatt, or the ion-sphere model of Zimmerman-More. Instead, plasma simulations using finite-temperature density functional theory with excited-state projector augmented-wave potentials show excellent agreement with the experimental results and explain the stronger-than-expected continuum lowering through the electronic structure of the valence states in these strong-coupling conditions, which retain much of their atomic characteristics close to the ion core regions. These results have a profound impact on the understanding and modelling of plasmas over a wide range of warm- and hot-dense matter conditions.

  9. Ionization channel of continuum lowering in plasmas: effects of plasma screening, electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Kryukov, N.; Oks, E.

    2013-12-01

    Calculations of continuum lowering (CL) in plasmas evolved from ion sphere models to dicentre models of the plasma state. One of such theories—a percolation theory—calculated CL defined as an absolute value of energy at which an electron becomes bound to a macroscopic portion of plasma ions (a quasi-ionization). Previously one of us derived analytically the value of CL in the ionization channel which was disregarded in the percolation theory. In the present paper we study how the value of CL in the ionization channel is affected by plasma screening, electric and magnetic fields. We show that the screening and the magnetic field decrease the value of CL, inhibiting the ionization, while the electric field increases the value of CL, promoting the ionization. These results should be important for inertial fusion, x-ray lasers, powerful Z-pinches, astrophysics and other applications of high-density plasmas. We also show that the screening stabilizes the nuclear motion of the corresponding Rydberg quasimolecules in some cases and destabilizes it in other cases.

  10. Doing Away with Occupation Probability: A New Way to Model Continuum Lowering at White Dwarf Photosphere Conditions

    NASA Astrophysics Data System (ADS)

    Gomez, Thomas A.; Winget, Donald E.; Montgomery, Michael H.; Kilcrease, Dave; Nagayama, Taisuke

    2016-01-01

    White dwarfs are interesting for a number of applications including studying equations of state, stellar pulsations, and determining the age of the universe.These interesting applications require accurate determination of surface conditions: temperatures and surface gravity (or mass).The most common technique to estimate the temperature and gravity is to find the model spectrun that best fits the observed spectra of a star (known as the spectroscopic method); however, this model rests on our ability to accurately model the hydrogen spectrum at high densities.There are currently disagreements between the spectroscopic method and other techniques to determine mass.We seek to resolve this issue by exploring the continuum lowering (or disappearance of states) of the hydrogen atom.The current formalism, called "occupation probability," defines some criteria for the isolated atom's bound state to be ionized, then extrapolates the continuous spectrum to the same energy threshold.The two are then combined to create the final cross-section.I introduce a new way of calculating the atomic spectrum by doing some averaging of the plasma interaction potential energy (previously used in the physics community) and directly integrating the Schrodinger equation.This technique is a major improvement over the Taylor expansion used to describe the ion-emitter interaction and removes the need of the occupation probability and treats continuum states and discrete states on the same footing in the spectrum calculation.The resulting energy spectrum is in fact many discrete states that when averaged over the electric field distribution in the plasma appears to be a continuum.In the low density limit, the two methods are in agreement, but show some differences at high densities (above 10$^{17} e/cc$) including line shifts near the ``continuum'' edge.

  11. The evolution of organic matter along the lower Amazon River continuum - Óbidos to the ocean

    NASA Astrophysics Data System (ADS)

    Ward, N. D.; Keil, R. G.; Medeiros, P. M.; Brito, D.; Cunha, A.; Sawakuchi, H. O.; Moura, J. S.; Yager, P. L.; Krusche, A. V.; Richey, J. E.

    2013-12-01

    The influence of the Amazon River on global hydrologic and biogeochemical cycling is well recognized. The Amazon River provides roughly 16% of the global freshwater supply to the ocean and is a significant source of CO2 to the atmosphere, outgassing 0.5 Pg C y-1 to the atmosphere--a flux roughly equivalent to the amount of carbon 'sequestered' by the Amazon rainforest (Field et al, 1998; Richey et al., 2002; Malhi et al., 2008). However, much of our understanding of the flux of matter from the Amazon River into the Atlantic Ocean (and atmosphere) is limited to measurements made at and upstream of Óbidos, 900 km upstream from the actual river mouth. Further, there are few to no observations documenting the transformation of organic matter in a parcel of water as it travels downstream of Óbidos into the ocean. Here we explore the hydrological and biogeochemical evolution of the lower Amazon River continuum, from Óbidos to the Atlantic Ocean. A suite of dissolved and particulate organic matter (OM) parameters were measured during a series of five river expeditions with stations at Óbidos, the Tapajós tributary, the mouth of the Lago Grande de Curuai floodplain lake, both the north and south channels of the Amazon River mouth near Macapá, and the confluence of the Amazon and Tocantins Rivers near Belém. In addition to bulk carbon isotopic signatures, a suite of biomarkers including dissolved and particulate lignin-derived phenols were measured to trace the sources and degradation history of terrestrial vascular plant derived OM throughout the continuum. Dissolved and particulate lignin phenol concentrations both correlated positively with river discharge in the Amazon River mainstem, with variable export patterns from the tributaries and floodplains. As organic matter travels along the continuum it is degraded by microbial composition, fuelling gross respiration and CO2 outgassing. The flux of organic carbon to the ocean is chemically recalcitrant as a result of

  12. Flood management along the Lower Mississippi and Rhine Rivers (The Netherlands) and the continuum of geomorphic adjustment

    NASA Astrophysics Data System (ADS)

    Hudson, Paul F.; Middelkoop, Hans; Stouthamer, Esther

    2008-10-01

    the 1928 Mississippi River & Tributaries Act have rapidly infilled, with 67% of the lake area converted to wetlands. In comparison, older oxbow lakes located outside of the embanked floodplain have undergone much lower amounts of infilling, averaging 37% of oxbow lake area converted to wetlands. The floodplain geomorphology is further modified by numerous large floodplain borrow pits and the selective removal of fine-grained deposits, primarily created for dike (levee) construction and maintenance. The Dutch Rhine has been managed for flooding for over eight centuries and exhibits specific types of humanized embanked floodplain geomorphology that require a greater period of adjustment. Dike breaches create ponds (wielen) and sandy splay-like deposits, which represent distinctive anthro-geomorphic environments along the margins of embanked floodplains. Channel stabilization by groynes and dikes has resulted in the formation of new floodplains along Rhine distributaries. The trapping of flood sediments within the embanked floodplain has resulted in aggradation that has reduced the inundation capacity of the embanked floodplain. This geomorphic alteration reduced the effectiveness of the existing flood management infrastructure and has stimulated a change towards a new flood management approach designed to "work with the river". The major conclusions are placed within a conceptual model, and illustrate that; 1. in many instances specific flood management options were constrained by the type of floodplain deposit; 2. geomorphic adjustment to flood management occurs along a time-space continuum; 3. flood management initiates positive feedbacks with unintended geomorphic consequences that require further management options to minimize flood risk.

  13. Magnetic field induced dynamical chaos

    SciTech Connect

    Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra

    2013-12-15

    In this article, we have studied the dynamics of a particle having charge in the presence of a magnetic field. The motion of the particle is confined in the x–y plane under a two dimensional nonlinear potential. We have shown that constant magnetic field induced dynamical chaos is possible even for a force which is derived from a simple potential. For a given strength of the magnetic field, initial position, and velocity of the particle, the dynamics may be regular, but it may become chaotic when the field is time dependent. Chaotic dynamics is very often if the field is time dependent. Origin of chaos has been explored using the Hamiltonian function of the dynamics in terms of action and angle variables. Applicability of the present study has been discussed with a few examples.

  14. Static-field-induced states

    NASA Astrophysics Data System (ADS)

    Gets, Artem V.; Tolstikhin, Oleg I.

    2013-01-01

    Considering an electron interacting with an atomic or molecular potential and an external static electric field, one usually focuses on narrow resonances at negative energies originating from the bound states in the absence of the field; we call them tunneling states (TSs). Meanwhile, there also exist relatively broad resonances at positive energies having no counterparts in the absence of the field; we call them static-field-induced states (SFISs). In this paper, the recently developed weak-field asymptotic theory of TSs [O. I. Tolstikhin , Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.84.053423 84, 053423 (2011)] is extended to SFISs. An asymptotic quantization condition defining the energies of SFISs in an arbitrary potential in the three-dimensional case is derived. The parabolic scattering amplitudes appearing in this quantization condition are defined. The theory is illustrated by calculations for the zero-range and Coulomb potentials. The SFISs in these potentials are found and their energies are shown to be in good agreement with the asymptotic results over a wide interval of the values of the field.

  15. Field induced gap infrared detector

    NASA Technical Reports Server (NTRS)

    Elliott, C. Thomas (Inventor)

    1990-01-01

    A tunable infrared detector which employs a vanishing band gap semimetal material provided with an induced band gap by a magnetic field to allow intrinsic semiconductor type infrared detection capabilities is disclosed. The semimetal material may thus operate as a semiconductor type detector with a wavelength sensitivity corresponding to the induced band gap in a preferred embodiment of a diode structure. Preferred semimetal materials include Hg(1-x)Cd(x)Te, x is less than 0.15, HgCdSe, BiSb, alpha-Sn, HgMgTe, HgMnTe, HgZnTe, HgMnSe, HgMgSe, and HgZnSe. The magnetic field induces a band gap in the semimetal material proportional to the strength of the magnetic field allowing tunable detection cutoff wavelengths. For an applied magnetic field from 5 to 10 tesla, the wavelength detection cutoff will be in the range of 20 to 50 micrometers for Hg(1-x)Cd(x)Te alloys with x about 0.15. A similar approach may also be employed to generate infrared energy in a desired band gap and then operating the structure in a light emitting diode or semiconductor laser type of configuration.

  16. Continuum Nanofluidics.

    PubMed

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

    2015-12-15

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

  17. Field-induced confined states in graphene

    SciTech Connect

    Moriyama, Satoshi; Morita, Yoshifumi; Watanabe, Eiichiro; Tsuya, Daiju

    2014-02-03

    We report an approach to confine the carriers in single-layer graphene, which leads to quantum devices with field-induced quantum confinement. We demonstrated that the Coulomb-blockade effect evolves under a uniform magnetic field perpendicular to the graphene device. Our experimental results show that field-induced quantum dots are realized in graphene, and a quantum confinement-deconfinement transition is switched by the magnetic field.

  18. Electric field-induced softening of alkali silicate glasses

    NASA Astrophysics Data System (ADS)

    McLaren, C.; Heffner, W.; Tessarollo, R.; Raj, R.; Jain, H.

    2015-11-01

    Motivated by the advantages of two-electrode flash sintering over normal sintering, we have investigated the effect of an external electric field on the viscosity of glass. The results show remarkable electric field-induced softening (EFIS), as application of DC field significantly lowers the softening temperature of glass. To establish the origin of EFIS, the effect is compared for single vs. mixed-alkali silicate glasses with fixed mole percentage of the alkali ions such that the mobility of alkali ions is greatly reduced while the basic network structure does not change much. The sodium silicate and lithium-sodium mixed alkali silicate glasses were tested mechanically in situ under compression in external electric field ranging from 0 to 250 V/cm in specially designed equipment. A comparison of data for different compositions indicates a complex mechanical response, which is observed as field-induced viscous flow due to a combination of Joule heating, electrolysis and dielectric breakdown.

  19. Electric field-induced softening of alkali silicate glasses

    SciTech Connect

    McLaren, C.; Heffner, W.; Jain, H.; Tessarollo, R.; Raj, R.

    2015-11-02

    Motivated by the advantages of two-electrode flash sintering over normal sintering, we have investigated the effect of an external electric field on the viscosity of glass. The results show remarkable electric field-induced softening (EFIS), as application of DC field significantly lowers the softening temperature of glass. To establish the origin of EFIS, the effect is compared for single vs. mixed-alkali silicate glasses with fixed mole percentage of the alkali ions such that the mobility of alkali ions is greatly reduced while the basic network structure does not change much. The sodium silicate and lithium-sodium mixed alkali silicate glasses were tested mechanically in situ under compression in external electric field ranging from 0 to 250 V/cm in specially designed equipment. A comparison of data for different compositions indicates a complex mechanical response, which is observed as field-induced viscous flow due to a combination of Joule heating, electrolysis and dielectric breakdown.

  20. Effects of hole doping by neutron irradiation of magnetic field induced electronic phase transitions in graphite

    SciTech Connect

    Singleton, John; Yaguchi, Hiroshi

    2008-01-01

    We have investigated effects of hole doping by fast-neutron irradiation on the magnetic-field induced phase transitions in graphite using specimens irradiated with fast neutrons. Resistance measurements have been done in magnetic fields of up to above 50 T and at temperatures down to about 1.5 K. The neutron irradiation creates lattice defects acting as acceptors, affecting the imbalance of the electron and hole densities and the Fermi level. We have found that the reentrant field from the field induced state back to the normal state shifts towards a lower field with hole doping, suggestive of the participation of electron subbands in the magnetic-field induced state.

  1. Kilometric Continuum Radiation

    NASA Technical Reports Server (NTRS)

    Green, James L.; Boardsen, Scott

    2006-01-01

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

  2. Electric field induced spin-polarized current

    DOEpatents

    Murakami, Shuichi; Nagaosa, Naoto; Zhang, Shoucheng

    2006-05-02

    A device and a method for generating an electric-field-induced spin current are disclosed. A highly spin-polarized electric current is generated using a semiconductor structure and an applied electric field across the semiconductor structure. The semiconductor structure can be a hole-doped semiconductor having finite or zero bandgap or an undoped semiconductor of zero bandgap. In one embodiment, a device for injecting spin-polarized current into a current output terminal includes a semiconductor structure including first and second electrodes, along a first axis, receiving an applied electric field and a third electrode, along a direction perpendicular to the first axis, providing the spin-polarized current. The semiconductor structure includes a semiconductor material whose spin orbit coupling energy is greater than room temperature (300 Kelvin) times the Boltzmann constant. In one embodiment, the semiconductor structure is a hole-doped semiconductor structure, such as a p-type GaAs semiconductor layer.

  3. The Suicide Prevention Continuum

    PubMed Central

    Caldwell, Dawn

    2010-01-01

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

  4. Surface modifications by field induced diffusion.

    PubMed

    Olsen, Martin; Hummelgård, Magnus; Olin, Håkan

    2012-01-01

    By applying a voltage pulse to a scanning tunneling microscope tip the surface under the tip will be modified. We have in this paper taken a closer look at the model of electric field induced surface diffusion of adatoms including the van der Waals force as a contribution in formations of a mound on a surface. The dipole moment of an adatom is the sum of the surface induced dipole moment (which is constant) and the dipole moment due to electric field polarisation which depends on the strength and polarity of the electric field. The electric field is analytically modelled by a point charge over an infinite conducting flat surface. From this we calculate the force that cause adatoms to migrate. The calculated force is small for voltage used, typical 1 pN, but due to thermal vibration adatoms are hopping on the surface and even a small net force can be significant in the drift of adatoms. In this way we obtain a novel formula for a polarity dependent threshold voltage for mound formation on the surface for positive tip. Knowing the voltage of the pulse we then can calculate the radius of the formed mound. A threshold electric field for mound formation of about 2 V/nm is calculated. In addition, we found that van der Waals force is of importance for shorter distances and its contribution to the radial force on the adatoms has to be considered for distances smaller than 1.5 nm for commonly used voltages. PMID:22253894

  5. Surface Modifications by Field Induced Diffusion

    PubMed Central

    Olsen, Martin; Hummelgård, Magnus; Olin, Håkan

    2012-01-01

    By applying a voltage pulse to a scanning tunneling microscope tip the surface under the tip will be modified. We have in this paper taken a closer look at the model of electric field induced surface diffusion of adatoms including the van der Waals force as a contribution in formations of a mound on a surface. The dipole moment of an adatom is the sum of the surface induced dipole moment (which is constant) and the dipole moment due to electric field polarisation which depends on the strength and polarity of the electric field. The electric field is analytically modelled by a point charge over an infinite conducting flat surface. From this we calculate the force that cause adatoms to migrate. The calculated force is small for voltage used, typical 1 pN, but due to thermal vibration adatoms are hopping on the surface and even a small net force can be significant in the drift of adatoms. In this way we obtain a novel formula for a polarity dependent threshold voltage for mound formation on the surface for positive tip. Knowing the voltage of the pulse we then can calculate the radius of the formed mound. A threshold electric field for mound formation of about 2 V/nm is calculated. In addition, we found that van der Waals force is of importance for shorter distances and its contribution to the radial force on the adatoms has to be considered for distances smaller than 1.5 nm for commonly used voltages. PMID:22253894

  6. Field-induced superdiffusion and dynamical heterogeneity.

    PubMed

    Gradenigo, Giacomo; Bertin, Eric; Biroli, Giulio

    2016-06-01

    By analyzing two kinetically constrained models of supercooled liquids we show that the anomalous transport of a driven tracer observed in supercooled liquids is another facet of the phenomenon of dynamical heterogeneity. We focus on the Fredrickson-Andersen and the Bertin-Bouchaud-Lequeux models. By numerical simulations and analytical arguments we demonstrate that the violation of the Stokes-Einstein relation and the field-induced superdiffusion observed during a long preasymptotic regime have the same physical origin: while a fraction of probes do not move, others jump repeatedly because they are close to local mobile regions. The anomalous fluctuations observed out of equilibrium in the presence of a pulling force ε,σ_{x}^{2}(t)=〈x_{ε}^{2}(t)〉-〈x_{ε}(t)〉^{2}∼t^{3/2}, which are accompanied by the asymptotic decay α_{ε}(t)∼t^{-1/2} of the non-Gaussian parameter from nontrivial values to zero, are due to the splitting of the probes population in the two (mobile and immobile) groups and to dynamical correlations, a mechanism expected to happen generically in supercooled liquids. PMID:27415189

  7. "Caught in the Continuum"

    ERIC Educational Resources Information Center

    Nisbet, Jan

    2004-01-01

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

  8. Continuum radiation at Uranus

    SciTech Connect

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

    1990-02-01

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

  9. Kernel Continuum Regression.

    PubMed

    Lee, Myung Hee; Liu, Yufeng

    2013-12-01

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

  10. The Aquatic Systems Continuum

    NASA Astrophysics Data System (ADS)

    Winter, T. C.

    2004-12-01

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

  11. Field-induced dynamical properties of the XXZ model on a honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Maksimov, Pavel; Chernyshev, Alexander

    We present a comprehensive 1 / S study of the field-induced dynamical properties of the nearest-neighbor XXZ antiferromagnet on a honeycomb lattice using the formalism of the nonlinear spin-wave theory developed for this model. External magnetic field controls spin frustration in the system and induces non-collinearity of the spin structure, which is essential for the two-magnon decay processes. Our results include an intriguing field-evolution of the regions of the Brillouin zone where decays of spin excitations are prominent, a thorough analysis of the singularities in the magnon spectra due to coupling to the two-magnon continuum, the asymptotic behavior of the decay rates near high-symmetry points, and inelastic neutron-scattering spin-spin structure factor obtained in the leading 1 / S order. Supported by DOE.

  12. Electric-Field Induced Activation of Dark Excitonic States in Carbon Nanotubes.

    PubMed

    Uda, T; Yoshida, M; Ishii, A; Kato, Y K

    2016-04-13

    Electrical activation of optical transitions to parity-forbidden dark excitonic states in individual carbon nanotubes is reported. We examine electric-field effects on various excitonic states by simultaneously measuring photocurrent and photoluminescence. As the applied field increases, we observe an emergence of new absorption peaks in the excitation spectra. From the diameter dependence of the energy separation between the new peaks and the ground state of E11 excitons, we attribute the peaks to the dark excited states which became optically active due to the applied field. Field-induced exciton dissociation can explain the photocurrent threshold field, and the edge of the E11 continuum states has been identified by extrapolating to zero threshold. PMID:26999284

  13. Examining the Psychosis Continuum

    PubMed Central

    DeRosse, Pamela; Karlsgodt, Katherine H.

    2015-01-01

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

  14. Teacher Education: A Continuum.

    ERIC Educational Resources Information Center

    Momentum, 1990

    1990-01-01

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

  15. The Creativity Continuum

    ERIC Educational Resources Information Center

    Walling, Donovan R.

    2009-01-01

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

  16. The Continuum of Listening

    ERIC Educational Resources Information Center

    Rud, A. G.; Garrison, Jim

    2007-01-01

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

  17. Extragalactic continuum sources.

    NASA Astrophysics Data System (ADS)

    Valtaoja, E.

    1989-09-01

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

  18. Electric-field Induced Microdynamics of Charged Rods

    NASA Astrophysics Data System (ADS)

    Kang, Kyongok

    2014-12-01

    Electric-field induced phase/state transitions are observed in AC electric fields with small amplitudes and low frequencies in suspensions of charged fibrous viruses (fd), which are model systems for highly charged rod-like colloids. Texture- and particle-dynamics in these field-induced states, and on crossing transition lines, are explored by image time-correlation and dynamic light scattering, respectively. At relatively low frequencies, starting from a system within the isotropic-nematic coexistence region, a transition from a nematic to a chiral nematic is observed, as well as a dynamical state where nematic domains melt and reform. These transitions are preliminary due to field-induced dissociation/association of condensed ions. At higher frequencies a uniform state is formed that is stabilized by hydrodynamic interactions through field-induced electro-osmotic flow where the rods align along the field direction. There is a point in the field-amplitude versus frequency plane where various transition lines meet. This point can be identified as a “non-equilibrium critical point”, in the sense that a length scale and a time scale diverge on approach of that point. The microscopic dynamics exhibits discontinuities on crossing transition lines that were identified independently by means of image and signal correlation spectroscopy.

  19. A study of discrete and continuum joint modeling techniques

    SciTech Connect

    Jung, J.; Brown, S.R.

    1992-05-01

    This paper presents the results of a numerical and experimental study in which finite element and discrete element techniques were used to analyze a layered polycarbonate plate model subjected to uniaxial compression. Also, the two analysis techniques were used to compute the response of an eight meter diameter drift in jointed-rock. The drift was subjected to in-situ and far-field induced thermal stresses. The finite element analyses used a continuum rock model to represent the jointed-rock. A comparison of the analyses showed that the finite element continuum joint model consistently predicted less joint slippage than did the discrete element analyses, although far-field displacements compared well.

  20. The Response Continuum

    SciTech Connect

    Caltagirone, Sergio; Frincke, Deborah A.

    2005-06-17

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

  1. Field-induced dynamical properties of the XXZ model on a honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Maksimov, P. A.; Chernyshev, A. L.

    2016-01-01

    We present a comprehensive 1 /S study of the field-induced dynamical properties of the nearest-neighbor XXZ antiferromagnet on a honeycomb lattice using the formalism of nonlinear spin-wave theory developed for this model. The external magnetic field controls spin frustration in the system and induces noncollinearity of the spin structure, which is essential for the two-magnon decay processes. Our results include an intriguing field-evolution of the regions of the Brillouin zone wherein decays of spin excitations are prominent, a detailed classification of the decay channels involving magnons from both excitation branches, and a thorough analysis of the singularities in the magnon spectra due to coupling to the two-magnon continuum, all of which are illustrated for several field and anisotropy values. We highlight a number of features related to either the non-Bravais nature of the lattice or the existence of the Dirac-like points in the spectrum. In addition, the asymptotic behavior of the decay rates near high-symmetry points is analyzed in detail. The inelastic neutron-scattering spin-spin structure factor is obtained in the leading 1 /S order and is shown to exhibit qualitatively distinct fingerprints of the decay-induced magnon dynamics such as quasiparticle peaks broadened by decays and strong spectral weight redistribution.

  2. Deuterium NMR investigations of field-induced director alignment in nematic liquid crystals.

    PubMed

    Sugimura, Akihiko; Luckhurst, Geoffrey R

    2016-05-01

    There have been many investigations of the alignment of nematic liquid crystals by either a magnetic and/or an electric field. The basic features of the important hydrodynamic processes for low molar mass nematics have been characterized for the systems in their equilibrium and non-equilibrium states. These have been created using electric and magnetic fields to align the director and deuterium nuclear magnetic resonance ((2)H NMR) spectroscopy has been used to explore this alignment. Theoretical models based on continuum theory have been developed to complement the experiments and found to describe successfully the static and the dynamic phenomena observed. Such macroscopic behaviour has been investigated with (2)H NMR spectroscopy, in which an electric field in addition to the magnetic field of the spectrometer is used to rotate the director and produce a non-equilibrium state. This powerful technique has proved to be especially valuable for the investigation of nematic liquid crystals. Since the quadrupolar splitting for deuterons observed in the liquid crystal phase is determined by the angle between the director and the magnetic field, time-resolved and time-averaged (2)H NMR spectroscopies can be employed to investigate the dynamic director alignment process in a thin nematic film following the application or removal of an electric field. In this article, we describe some seminal studies to illustrate the field-induced static and dynamic director alignment for low molar mass nematics. PMID:27247284

  3. Magnetic field induced differential neutron phase contrast imaging

    SciTech Connect

    Strobl, M.; Treimer, W.; Walter, P.; Keil, S.; Manke, I.

    2007-12-17

    Besides the attenuation of a neutron beam penetrating an object, induced phase changes have been utilized to provide contrast in neutron and x-ray imaging. In analogy to differential phase contrast imaging of bulk samples, the refraction of neutrons by magnetic fields yields image contrast. Here, it will be reported how double crystal setups can provide quantitative tomographic images of magnetic fields. The use of magnetic air prisms adequate to split the neutron spin states enables a distinction of field induced phase shifts and these introduced by interaction with matter.

  4. Field induced spin chirality and chirality switching in magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Tartakovskaya, Elena V.

    2015-05-01

    The physical origin of the field-induced spin chirality experimentally observed in rare earth multilayers is determined. It is shown that the effect is possible due to the interplay between solid-state exchange interactions (the Ruderman-Kittel-Kasuya-Yosida and the Dsyaloshinsky-Moriya interactions), the external magnetic field and a special confinement of magnetic constituents. The presented model describes a certain temperature dependence of the chirality factor in agreement with experimental data and opens a new way to design nanostructured objects with predicted handedness.

  5. Relativistic Continuum Shell Model

    NASA Astrophysics Data System (ADS)

    Grineviciute, Janina; Halderson, Dean

    2011-04-01

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

  6. Signatures of field-induced intramolecular quantum interference in high-order harmonic generation by laser-irradiated homonuclear diatomics

    NASA Astrophysics Data System (ADS)

    Usachenko, Vladimir; Kim, Vyacheslav; Pyak, Pavel

    2015-05-01

    We report about the results of our theoretical study of the strong-field phenomenon of high-order harmonic generation (HHG) in homonuclear diatomics H2+ andH2 irradiated by a high-intensity laser field of mid-infrared wavelengths corresponding to intermediate values of the so-called Keldysh parameter (γ <= 1). The problem is addressed within the length-gauge (LG) formulation of strong-field approximation (SFA) additionally exploiting the density-functional-theory (DFT) method for numerical composition of initial (laser-free) molecular state using the routines of GAUSSIAN-03 code. The results of our present LG-VGA calculation well reproduce a pronounced interference-related minimum arising in high-frequency region of respective molecular HHG spectra and suggesting clear signatures of the field-induced intramolecular interference corresponding to photoelectron emission to intermediate continuum states from different atomic centers.

  7. Magnetic-field-induced liquid metal droplet manipulation

    NASA Astrophysics Data System (ADS)

    Kim, Daeyoung; Lee, Jeong-Bong

    2015-01-01

    We report magnetic-field-induced liquid metal droplet on-demand manipulation by coating a liquid metal with ferromagnetic materials. The gallium-based liquid metal alloy has a challenging drawback that it is instantly oxidized in ambient air, resulting in surface wetting on most surfaces. When the oxidized surface of the droplet is coated with ferromagnetic materials, it is non-wettable and can be controlled by applying an external magnetic field. We coated the surface of a liquid metal droplet with either an electroplated CoNiMnP layer or an iron (Fe) particle by simply rolling the liquid metal droplet on an Fe particle bed. For a paper towel, the minimum required magnetic flux density to initiate movement of the ~8 μL Fe-particle-coated liquid metal droplet was 50 gauss. Magnetic-field-induced liquid metal droplet manipulation was investigated under both horizontal and vertical magnetic fields. Compared to the CoNiMnP-electroplated liquid metal droplet, the Fe-particle-coated droplet could be well controlled because Fe particles were uniformly coated on the surface of the droplet. With a maximum applied magnetic flux density of ~1,600 gauss, the CoNiMnP layer on the liquid metal broke down, resulting in fragmentation of three smaller droplets, and the Fe particle was detached from the liquid metal surface and was re-coated after the magnetic field had been removed.

  8. Calibration of Electric Field Induced Energy Level Shifts in Argon

    NASA Astrophysics Data System (ADS)

    Hebner, Greg

    1999-10-01

    Argon is a commonly used gas in a number of discharges. As such it is an ideal candidate for spectroscopic based electric field measurements within the sheath and bulk discharge regions. Recently, measurements demonstrated the use of the Stark induced shifts of high lying energy levels in Argon to make spatially and temporally resolved electric field measurements [1]. However, that method relied on the cross calibration of known and calculable shifts in helium discharges to calibrate, in-situ, the energy level shifts in Argon. This poster shows the use of an atomic beam system to calibrate the electric field induced shift of high lying energy levels directly. In addition, data on very high lying argon levels, up to the 20 F manifold, were obtained. Comparison of our electric field induced energy level shift calibration curves with previous work will be shown. The possibility of using this system to calibrate energy level shifts in other gases of technological interest to the microelectronics and lighting industry will be discussed. [1]. J. B. Kim, K. Kawamura, Y. W. Choi, M. D. Bowden, K. Muraoka and V. Helbig, IEEE Transactions on Plasma Science, 26(5), 1556 (1998). This work was performed at Sandia National Laboratories and supported by the United States Department of Energy (DE-AC04-94AL85000).

  9. The Paranoid-Depressive Continuum

    ERIC Educational Resources Information Center

    Johnson, Betty J.

    1977-01-01

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

  10. The Intraprofessional Continuum and Cleft.

    PubMed

    Jensen, Clyde B

    2016-08-01

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

  11. Field-Induced Negative Differential Spin Lifetime in Silicon

    NASA Astrophysics Data System (ADS)

    Li, Jing; Qing, Lan; Dery, Hanan; Appelbaum, Ian

    2012-04-01

    We show that the electric-field-induced thermal asymmetry between the electron and lattice systems in pure silicon substantially impacts the identity of the dominant spin relaxation mechanism. Comparison of empirical results from long-distance spin transport devices with detailed Monte Carlo simulations confirms a strong spin depolarization beyond what is expected from the standard Elliott-Yafet theory even at low temperatures. The enhanced spin-flip mechanism is attributed to phonon emission processes during which electrons are scattered between conduction band valleys that reside on different crystal axes. This leads to anomalous behavior, where (beyond a critical field) reduction of the transit time between spin-injector and spin-detector is accompanied by a counterintuitive reduction in spin polarization and an apparent negative spin lifetime.

  12. Electric field induced second harmonic generation with and without fringes

    NASA Astrophysics Data System (ADS)

    Meshulam, G.; Berkovic, G.; Kotler, Z.; Sa'ar, A.

    2000-09-01

    Electric field induced second harmonic generation (EFISH) is a well-known technique to measure the first hyperpolarizability (β) of organic molecules in solution. The characteristic experimental output is observation of oscillatory fringes of second harmonic radiation as the solution path length is changed and evaluation of β from the fringe amplitude. We present two different cases where even in the absence of these characteristic fringes β may still be evaluated: first, when using absorbing materials, and second, when using broadband laser sources. The ability to determine β by EFISH under these conditions greatly enhances the ability of this technique to measure β values over a wide range of laser frequencies. Measurements of the same molecule's β values at different frequencies are reported, verifying the two-level model for the dispersion of β.

  13. Magnetic-Field Induced Diffraction Patterns from Ferrofluids

    NASA Astrophysics Data System (ADS)

    Rablau, Corneliu; Vaishnava, Prem; Lawes, Gavin; Naik, Ratna

    2011-04-01

    Ferrofluids are stable colloidal suspensions of superparamagnetic nanoparticles in a carrier liquid. We report studies of magneto-optic properties of two ferrofluid systems consisting of tetramethyl-ammonium-hydroxide (TMAH)-coated and of dextran-coated Fe3O4 nanoparticles of nominal sizes of 6 nm and 12 nm respectively suspended in water. Both samples showed superparamagnetic behavior. The static and time-dependent DC-magnetic-field-induced light scattering patterns produced by two orthogonal He-Ne laser beams passing through the ferrofluid samples revealed significant different optical signatures for the two surfactants. Notably, in contrast to the linear diffraction pattern produced by TMAH-coated nanoparticles, a circular diffraction pattern is reported -- for the first time -- in the dextran-coated ferrofluid.

  14. Direct observations of field-induced assemblies in magnetite ferrofluids

    SciTech Connect

    Mousavi, N. S. Susan; Khapli, Sachin D.; Kumar, Sunil

    2015-03-14

    Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ≤ 10 nm) is studied with an emphasis on examining the effects of particle concentration (ϕ) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ϕ = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05–0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity.

  15. Direct observations of field-induced assemblies in magnetite ferrofluids

    PubMed Central

    Mousavi, N. S. Susan

    2015-01-01

    Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ≤ 10 nm) is studied with an emphasis on examining the effects of particle concentration (ϕ) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ϕ = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05–0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity. PMID:25829566

  16. Direct observations of field-induced assemblies in magnetite ferrofluids

    NASA Astrophysics Data System (ADS)

    Mousavi, N. S. Susan; Khapli, Sachin D.; Kumar, Sunil

    2015-03-01

    Evolution of microstructures in magnetite-based ferrofluids with weak dipolar moments (particle size ≤ 10 nm) is studied with an emphasis on examining the effects of particle concentration (ϕ) and magnetic field strength (H) on the structures. Nanoparticles are dispersed in water at three different concentrations, ϕ = 0.15%, 0.48%, and 0.59% (w/v) [g/ml%] and exposed to uniform magnetic fields in the range of H = 0.05-0.42 T. Cryogenic transmission electron microscopy is employed to provide in-situ observations of the field-induced assemblies in such systems. As the magnetic field increases, the Brownian colloids are observed to form randomly distributed chains aligned in the field direction, followed by head-to-tail chain aggregation and then lateral aggregation of chains termed as zippering. By increasing the field in low concentration samples, the number of chains increases, though their length does not change dramatically. Increasing concentration increases the length of the linear particle assemblies in the presence of a fixed external magnetic field. Thickening of the chains due to zippering is observed at relatively high fields. Through a systematic variation of concentration and magnetic field strength, this study shows that both magnetic field strength and change in concentration can strongly influence formation of microstructures even in weak dipolar systems. Additionally, the results of two commonly used support films on electron microscopy grids, continuous carbon and holey carbon films, are compared. Holey carbon film allows us to create local regions of high concentrations that further assist the development of field-induced assemblies. The experimental observations provide a validation of the zippering effect and can be utilized in the development of models for thermophysical properties such as thermal conductivity.

  17. Field-induced periodic distortions in a nematic liquid crystal: deuterium NMR study and theoretical analysis.

    PubMed

    Sugimura, A; Zakharov, A V

    2011-08-01

    The peculiarities in the dynamic of the director reorientation in a liquid crystal (LC) film under the influence of the electric E field directed at an angle α to the magnetic B field have been investigated both experimentally and theoretically. Time-resolved deuterium NMR spectroscopy is employed to investigate the field-induced director dynamics. Analysis of the experimental results, based on the predictions of hydrodynamic theory including both the director motion and fluid flow, provides an evidence for the appearance of the spatially periodic patterns in 4-n-pentyl-4'-cyanobiphenyl LC film, at the angles α>60∘, in response to the suddenly applied E. These periodic distortions produce a lower effective rotational viscosity. This gives a faster response of the director rotation than for a uniform mode, as observed in our NMR experiment. PMID:21929001

  18. Thermodynamically consistent continuum dislocation dynamics

    NASA Astrophysics Data System (ADS)

    Hochrainer, Thomas

    2016-03-01

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

  19. Submillimeter Continuum Observations of Comets

    NASA Technical Reports Server (NTRS)

    Jewitt, David

    1998-01-01

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

  20. Lagrangian continuum dynamics in ALEGRA.

    SciTech Connect

    Wong, Michael K. W.; Love, Edward

    2007-12-01

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

  1. Magnetic field induced motion behavior of gas bubbles in liquid

    PubMed Central

    Wang, Keliang; Pei, Pucheng; Pei, Yu; Ma, Ze; Xu, Huachi; Chen, Dongfang

    2016-01-01

    The oxygen evolution reaction generally exists in electrochemical reactions. It is a ubiquitous problem about how to control the motion of oxygen bubbles released by the reaction. Here we show that oxygen bubbles during oxygen evolution reaction exhibit a variety of movement patterns in the magnetic field, including directional migration and rotational motion of oxygen bubbles when the magnet in parallel with the electrode, and exclusion movement of oxygen bubbles when the magnet perpendicular to the electrode. The results demonstrate that the direction of oxygen bubbles movement is dependent upon the magnet pole near the electrode, and the kinetics of oxygen bubbles is mainly proportional to intensity of the electromagnetic field. The magnetic-field induced rotational motion of oxygen bubbles in a square electrolyzer can increase liquid hydrodynamics, thus solve the problems of oxygen bubbles coalescence, and uneven distribution of electrolyte composition and temperature. These types of oxygen bubbles movement will not only improve energy saving and metal deposition for energy storage and metal refinery, but also propel object motion in application to medical and martial fields. PMID:26867515

  2. Field-induced negative differential spin lifetime in silicon

    NASA Astrophysics Data System (ADS)

    Li, Jing; Qing, Lan; Dery, Hanan; Appelbaum, Ian

    2012-02-01

    Using experimental measurements of spin transport in undoped silicon, we show that the electric field-induced thermal asymmetry between the electron and lattice systems substantially impacts the identity of the dominant spin relaxation mechanism. In contrast to the Elliott-Yafet theory where intraband phonon absorption leads to spin relaxation, here we induce phonon emission during which electrons are scattered between conduction band valleys that reside on different crystal axes. This leads to anomalous behavior, where reduction of the transit time between spin-injector and spin-detector with larger electric field is accompanied by a counterintuitive reduction in spin polarization and an apparent negative spin lifetime.[4pt] Work at UMD is supported by the Office of Naval Research and the National Science Foundation. We acknowledge the support of the Center for Nanophysics and Advanced Materials and Maryland NanoCenter and its FabLab. Work at UR is supported by AFOSR and NSF (No. FA9550-09-1-0493 and No. DMR 1124601).

  3. Impurities in magnetic-field-induced Luttinger liquid

    NASA Astrophysics Data System (ADS)

    Tsai, Shan-Wen; Maslov, Dmitrii L.; Glazman, Leonid I.

    2001-03-01

    It has been shown recently(C. Biagini, D. L. Maslov, M. Yu. Reizer and L. I. Glazman, `` Magnetic-field-induced Luttinger liquid''), cond-mat/0006407. that a strong magnetic field applied to a bulk metal may induce a Luttinger liquid phase. This is a consequence of the reduced effective dimensionality of charge carriers from 3D to 1D, an effect which is most pronounced in the ultra-quantum limit, when only the lowest Landau level remains populated. We study the effect of impurities in this system. For the case of a point impurity, the calculation of the scattering cross section at a single impurity can be mapped exactly to a 1D problem of tunneling conductance through a barrier for interacting electrons, solved by Yue et al.(D. Yue, L. I. Glazman and K. A. Matveev, Phys. Rev. B 49) (1994) 1966.. Using this mapping, we find that the longitudinal (ɛ=+1) and transverse (ɛ=-1) Drude conductivities exhibit the scaling laws σ_ɛ∝ T^ɛα, where α=2e^2|lnκl_B|/π v_F, and vF and κ are the B-dependent Fermi velocity and screening wavevector, respectively; lB is the magnetic length. The physical reason for such a behavior of the conductivity is the almost 1D form of the Friedel oscillation around a single point impurity in the strong magnetic field.

  4. Kinetics of Field-Induced Surface Patterns on PMMA.

    PubMed

    Peng, Jyun-Siang; Yang, Fuqian; Chiang, Donyau; Lee, Sanboh

    2016-05-10

    A simple model was developed to analyze the growth of a liquid pillar under the action of an electric field between two parallel electrodes. A quadratic relationship between time and the diameter of the pillar was obtained. The diameter of the pillar increases with time. Large electric field assists the growth of the liquid pillar, while a liquid with a large viscosity hinders the growth of the liquid pillar. The field-induced formation and growth of PMMA pillars on PMMA films were observed using the configuration of a parallel capacitor. Pillars of larger sizes and smaller densities were formed on thicker PMMA films than on thinner PMMA films. The root-mean-square ( https://en.wikipedia.org/wiki/Root_mean_square ) diameter of the pillars increases with the increase of the annealing time and annealing temperature. The growth behavior of the pillars can be described by an Arrhenius relation with an activation energy of 24.4 kJ/mol, suggesting that the growth of the pillars is controlled by a thermal activation process. PMID:27094160

  5. Magnetic field induced motion behavior of gas bubbles in liquid

    NASA Astrophysics Data System (ADS)

    Wang, Keliang; Pei, Pucheng; Pei, Yu; Ma, Ze; Xu, Huachi; Chen, Dongfang

    2016-02-01

    The oxygen evolution reaction generally exists in electrochemical reactions. It is a ubiquitous problem about how to control the motion of oxygen bubbles released by the reaction. Here we show that oxygen bubbles during oxygen evolution reaction exhibit a variety of movement patterns in the magnetic field, including directional migration and rotational motion of oxygen bubbles when the magnet in parallel with the electrode, and exclusion movement of oxygen bubbles when the magnet perpendicular to the electrode. The results demonstrate that the direction of oxygen bubbles movement is dependent upon the magnet pole near the electrode, and the kinetics of oxygen bubbles is mainly proportional to intensity of the electromagnetic field. The magnetic-field induced rotational motion of oxygen bubbles in a square electrolyzer can increase liquid hydrodynamics, thus solve the problems of oxygen bubbles coalescence, and uneven distribution of electrolyte composition and temperature. These types of oxygen bubbles movement will not only improve energy saving and metal deposition for energy storage and metal refinery, but also propel object motion in application to medical and martial fields.

  6. Field-Induced Magnetic Phenomena in Molecule-Based Magnets

    NASA Astrophysics Data System (ADS)

    Kmety, Carmen R.

    2001-03-01

    Understanding the relationship between the crystal structure and magnetic ordering is crucial for the design of three-dimensional molecule-based magnets with high ordering temperatures. In this talk, we introduce a novel series of molecule-based magnets consisting of transition metal ions (Mn, Fe, Co, Ni or Cu) coordinated with the organic ligand dicyanamide [N(CN)_2]^-.(J.L. Manson et al. al.), Chem. Mater. 10, 2552 (1998); S.R. Batten et al. al., Chem. Commun. (Cambridge) 1998, 439; M. Kurmoo et al. al., New J. Chem. 22, 1515 (1998). The crystal structures for all compounds are isomorphous in the paramagnetic regime as well as in the ordered state. However, the compounds with transition metal ions having six or less electrons in the 3d orbitals order as canted antiferromagnets (AFM) while the ones with seven or more electrons order as ferromagnets (FM). The spin orientation is nearly in perpendicular directions for the AFM versus FM systems.(C.R. Kmety et al. al.), Phys. Rev. B 60, 60 (1999).^,(C.R. Kmety et al. al.), Phys. Rev. B 62, 5576 (2000). An external magnetic field induces a spin rotation transition in the Mn compound and an energy-level crossing for the Fe compound.(C.R. Kmety and A.J. Epstein, National High Magnetic Field Laboratory 2000 Annual Research Review.) The possible origins of the variability of the magnetic structure for the first row transition metal ions compounds will be discussed.

  7. Deconstructing field-induced ketene isomerization through Lagrangian descriptors.

    PubMed

    Craven, Galen T; Hernandez, Rigoberto

    2016-02-01

    The time-dependent geometrical separatrices governing state transitions in field-induced ketene isomerization are constructed using the method of Lagrangian descriptors. We obtain the stable and unstable manifolds of time-varying transition states as dynamic phase space objects governing configurational changes when the ketene molecule is subjected to an oscillating electric field. The dynamics of the isomerization reaction are modeled through classical trajectory studies on the Gezelter-Miller potential energy surface and an approximate dipole moment model which is coupled to a time-dependent electric field. We obtain a representation of the reaction geometry, over varying field strengths and oscillation frequencies, by partitioning an initial phase space into basins labeled according to which product state is reached at a given time. The borders between these basins are in agreement with those obtained using Lagrangian descriptors, even in regimes exhibiting chaotic dynamics. Major outcomes of this work are: validation and extension of a transition state theory framework built from Lagrangian descriptors, elaboration of the applicability for this theory to periodically- and aperiodically-driven molecular systems, and prediction of regimes in which isomerization of ketene and its derivatives may be controlled using an external field. PMID:26778728

  8. Time-resolved electric-field-induced second harmonic

    NASA Astrophysics Data System (ADS)

    Meshulam, Guilia; Berkovic, Garry; Kotler, Zvi

    2001-12-01

    One limitation of using electric field induced second harmonic (EFISH) to determine the molecular first hyperpolarizability (beta) of nonlinear optical molecules lies in the fact that part of the second harmonic signal comes from the second hyperpolarizability (gamma) produced by mixing two optical fields with the DC field. In analyzing EFISH results, the second hyperpolarizability contribution of the studied molecules is generally neglected. We present a modified time resolved EFISH technique that allows us, in a single experiment, to determine separately the beta and the gamma contributions. We study para-nitro aniline dissolved in Glycerol, a highly viscous solvent, and apply the DC field via a high voltage pulse with a fast rise time of approximately 40 nsec. As a result, the orientation of the molecules under the applied electric field is slow relative to the build-up of the field, enabling us to directly measure only the DC induced second harmonic (gamma contribution), at the beginning of the HV pulse. The pure beta contribution is determined from the difference between this signal and the conventional EFISH signal at the plateau of the HV pulse. Our result confirm that the gamma contribution is indeed less than 10% of the total.

  9. Magnetic field induced motion behavior of gas bubbles in liquid.

    PubMed

    Wang, Keliang; Pei, Pucheng; Pei, Yu; Ma, Ze; Xu, Huachi; Chen, Dongfang

    2016-01-01

    The oxygen evolution reaction generally exists in electrochemical reactions. It is a ubiquitous problem about how to control the motion of oxygen bubbles released by the reaction. Here we show that oxygen bubbles during oxygen evolution reaction exhibit a variety of movement patterns in the magnetic field, including directional migration and rotational motion of oxygen bubbles when the magnet in parallel with the electrode, and exclusion movement of oxygen bubbles when the magnet perpendicular to the electrode. The results demonstrate that the direction of oxygen bubbles movement is dependent upon the magnet pole near the electrode, and the kinetics of oxygen bubbles is mainly proportional to intensity of the electromagnetic field. The magnetic-field induced rotational motion of oxygen bubbles in a square electrolyzer can increase liquid hydrodynamics, thus solve the problems of oxygen bubbles coalescence, and uneven distribution of electrolyte composition and temperature. These types of oxygen bubbles movement will not only improve energy saving and metal deposition for energy storage and metal refinery, but also propel object motion in application to medical and martial fields. PMID:26867515

  10. Possible Electric-Field-Induced Superconducting States in Doped Silicene

    PubMed Central

    Zhang, Li-Da; Yang, Fan; Yao, Yugui

    2015-01-01

    Silicene has been synthesized recently, with experimental evidence showing possible superconductivity in the doped case. The noncoplanar low-buckled structure of this material inspires us to study the pairing symmetry of the doped system under a perpendicular external electric field. Our study reveals that the electric field induces an interesting quantum phase transition from the singlet chiral d + id′-wave superconducting phase to the triplet f-wave one. The emergence of the f-wave pairing results from the sublattice-symmetry-breaking caused by the electric field and the ferromagnetic-like intra-sublattice spin correlations at low dopings. Due to the enhanced density of states, the superconducting critical temperature of the system is enhanced by the electric field remarkably. Furthermore, we design a particular dc SQUID experiment to detect the quantum phase transition predicted here. Our results, if confirmed, will inject a new vitality to the familiar Si-based industry through adopting doped silicene as a tunable platform to study different types of exotic unconventional superconductivities. PMID:25644143

  11. PAD in women: the ischemic continuum.

    PubMed

    Pollak, Amy West

    2015-06-01

    Lower extremity peripheral arterial disease (PAD) is part of the ischemic continuum of atherosclerotic vascular disease and is associated with an increased risk of myocardial infarction, stroke, and cardiovascular death. Compared to men, women with PAD are more likely to have asymptomatic disease or atypical symptoms. PAD in women is associated with decreased exercise capacity, reduced quality of life, increased risk of depression, as well as a greater risk of acute cardiovascular events and cardiovascular mortality than male counterparts. Ensuring an appropriate diagnosis of women with PAD offers an opportunity to begin risk factor modification therapy, improve walking capacity and make a timely referral for revascularization if needed. It is critical to highlight the sex-based disparities in lower extremity PAD so that we may work to improve outcomes for women with PAD. PMID:25939674

  12. Calorimetric Study of Magnetic Field-Induced Phase Transitions in - Fulvalenium) -

    NASA Astrophysics Data System (ADS)

    Fortune, Nathanael Alexander

    The particular class of organic conductors known as the Bechgaard salts exhibit a variety of highly anisotropic magnetic, thermal, and electrical phenomena. At low temperatures (below 10 kelvin), the application of a strong magnetic field establishes an effectively lower-dimensional anisotropic Fermi surface, as manifested in a variety of quasi one dimensional and quasi two dimensional thermodynamic and transport properties. Most dramatically, an increasing magnetic field--after suppression of superconductivity, induces a second order phase transition from a metallic to a spin density wave semimetal, followed by a series of first order phase transitions between density wave semimetallic states. This thesis concerns the thermodynamic nature of the low temperature magnetic field induced phase transitions in the Bechgaard charge-transfer salt (TMTSF)2-Cl(O)4. Presented here are the first measurements of the specific heat in magnetic fields up to 30 tesla, as well as the design and construction of a small sample calorimeter capable of operating at dilution refrigerator temperatures in the challenging environment of the high field resistive Bitter magnets. From transport measurements, the existence of a magnetic field induced reentrance into the metallic state has previously been inferred. In this thesis, the unambiguous bulk thermodynamic character of the reentrance is calorimetrically demonstrated. The behavior of the electronic specific heat at the reentrant transition is shown to be consistent with magnetic field enhanced localization. Additionally, quantum oscillations in the high field semimetallic state and the presence of additional structure above the reentrant field are observed. Although these oscillations have also been observed in magnetoresistance and magnetization, the magnitude of the oscillations in the specific heat calls into question all known models for the physical origin of these oscillations.

  13. Population transfer through the continuum

    SciTech Connect

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

    1994-08-01

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

  14. Parameter identification in continuum models

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  15. A Math Continuum, Part D.

    ERIC Educational Resources Information Center

    Zander, Del; And Others

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

  16. Learner Continuums and Speech Communities.

    ERIC Educational Resources Information Center

    Amastae, Jon

    1981-01-01

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

  17. High magnetic field induced changes of gene expression in arabidopsis

    PubMed Central

    Paul, Anna-Lisa; Ferl, Robert J; Meisel, Mark W

    2006-01-01

    Background High magnetic fields are becoming increasingly prevalent components of non-invasive, biomedical imaging tools (such as MRI), thus, an understanding of the molecular impacts associated with these field strengths in biological systems is of central importance. The biological impact of magnetic field strengths up to 30 Tesla were investigated in this study through the use of transgenic Arabidopsis plants engineered with a stress response gene consisting of the alcohol dehydrogenase (Adh) gene promoter driving the β-glucuronidase (GUS) gene reporter. Methods Magnetic field induced Adh/GUS activity was evaluated with histochemical staining to assess tissue specific expression and distribution, and with quantitative, spectrofluometric assays to measure degree of activation. The evaluation of global changes in the Arabidopsis genome in response to exposure to high magnetic fields was facilitated with Affymetrix Gene Chip microarrays. Quantitative analyses of gene expression were performed with quantitative real-time polymerase-chain-reaction (qRT-PCR). Results Field strengths in excess of about 15 Tesla induce expression of the Adh/GUS transgene in the roots and leaves. From the microarray analyses that surveyed 8000 genes, 114 genes were differentially expressed to a degree greater than 2.5 fold over the control. These results were quantitatively corroborated by qRT-PCR examination of 4 of the 114 genes. Conclusion The data suggest that magnetic fields in excess of 15 Tesla have far-reaching effect on the genome. The wide-spread induction of stress-related genes and transcription factors, and a depression of genes associated with cell wall metabolism, are prominent examples. The roles of magnetic field orientation of macromolecules and magnetophoretic effects are discussed as possible factors that contribute to the mounting of this response. PMID:17187667

  18. Continuum descriptions of cytoskeletal dynamics

    PubMed Central

    2013-01-01

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

  19. Differential Complexes in Continuum Mechanics

    NASA Astrophysics Data System (ADS)

    Angoshtari, Arzhang; Yavari, Arash

    2015-04-01

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

  20. Continuum representations of cellular solids

    SciTech Connect

    Neilsen, M.K.

    1993-09-01

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

  1. Continuum radiation in planetary magnetospheres

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.

    1991-01-01

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

  2. 77 FR 45367 - Continuum of Care Homeless Assistance Grant Application; Continuum of Care Application

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-31

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

  3. The impact of a Continuum of Care Resident Pharmacist on heart failure readmissions and discharge instructions at a community hospital

    PubMed Central

    Backes, Andrea C

    2015-01-01

    Purpose: To examine the impact of a Continuum of Care Resident Pharmacist on (1) heart failure 30-day hospital readmissions and (2) compliance with Joint Commission Heart Failure core measure 1 at a community hospital. Methods: The Continuum of Care Network led by a Continuum of Care Resident Pharmacist was established in August 2011. The Continuum of Care Resident Pharmacist followed Continuum of Care Network patients and retrospectively collected data from August 2011 to December 2012. Thirty-day readmission rates for Continuum of Care Network heart failure patients versus non-Continuum of Care Network heart failure patients were compared and analyzed. Joint Commission Heart Failure core measure 1 compliance rates were retrospectively collected from January 2011 and compared to data after establishment of the Continuum of Care Network. Results: In all, 162 Continuum of Care Network patients and 470 non-Continuum of Care Network patients were discharged with a diagnosis of heart failure from August 2011 to December 2012. Continuum of Care Network heart failure patients had a lower 30-day all-cause readmission rate compared to non-Continuum of Care Network heart failure patients (12% versus 24%, respectively; p = 0.005). In addition, Heart Failure core measure 1 compliance rates improved from the 80th percentile to the 90th percentile after implementation of the Continuum of Care Network (p = 0.004). The top three interventions performed by the Continuum of Care Resident Pharmacist were discharge counseling (74.1%), providing a MedActionPlan™ (68.5%), and resolving medication reconciliation discrepancies (64.8%). Conclusion: The study findings suggest that a Continuum of Care Resident Pharmacist contributed to lowered heart failure readmission rates and improved Heart Failure core measure 1 compliance rates. Future randomized, controlled trials are needed to confirm these findings. PMID:26770775

  4. Continuum Theory of Retroviral Capsids

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

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

  5. Magnetic field induced minigap in double quantum wells

    SciTech Connect

    Simmons, J.A.; Lyo, S.K.; Klem, J.F.; Harff, N.E. |

    1994-07-01

    We report discovery of a partial energy gap, or minigap, in strongly coupled double quantum wells (QWs), due to an anticrossing of the two QW dispersion curves. The anticrossing and minigap are induced by an in-plane magnetic field B{sub {parallel}}, and give rise to large distortions in the Fermi surface and density of states, including a Van Hove singularity. Sweeping B{sub {parallel}} moves the minigap through the Fermi level, with the upper and lower gap edges producing a sharp maximum and minimum in the low-temperature in-plane conductance, in agreement with theoretical calculations. The gap energy may be directly determined from the data.

  6. Buckling of graded coatings: A continuum model

    NASA Astrophysics Data System (ADS)

    Chiu, Tz-Cheng

    2000-12-01

    Requirements for the protection of hot section components in many high temperature applications such as earth-to-orbit winged planes and advanced turbine systems have led to the application of thermal barrier coatings (TBCs) that utilize ceramic coatings on metal substrates. An alternative concept to homogeneous ceramic coatings is the functionally graded materials (FGM) in which the composition of the coating is intentionally graded to improve the bonding strength and to reduce the magnitude of the residual and thermal stresses. A widely observed failure mode in such layered systems is known to be interface cracking that leads to spallation fracture. In most cases, the final stage of the failure process for a thin coating appears to be due to buckling instability under thermally or mechanically induced compressive stress. The objective of this study is to develop a solution to the buckling instability problem by using continuum elasticity rather than a structural mechanics approach. The emphasis in the solution will be on the investigation of the effect of material inhomogeneity in graded coatings on the instability load, the postbuckling behavior, and fracture mechanics parameters such as the stress intensity factors and strain energy release rate. In this analysis, a nonlinear continuum theory is employed to examine the interface crack problem. The analytical solution of the instability problem permits the study of the effect of material inhomogeneity upon the inception of buckling and establishes benchmark results for the numerical solutions of related problems. To study the postbuckling behavior and to calculate the stress intensity factors and strain energy release rate a geometrically nonlinear finite element procedure with enriched crack-tip element is developed. Both plane strain and axisymmetric interface crack problems in TBCs with either homogeneous or graded coating are then considered by using the finite element procedure. It is assumed that the

  7. Rosuvastatin along the cardiovascular continuum: from JUPITER to AURORA.

    PubMed

    Barrios, Vivencio; Escobar, Carlos

    2009-11-01

    Dyslipidemia is one of the major causes of atherosclerosis, although in the last few years an increase in cholesterol control rates has been reported. However, results from the European Action on Secondary and Primary Prevention by Intervention to Reduce Events (EUROASPIRE) surveys indicate that approximately 50% of the patients with ischemic heart disease still do not attain LDL-cholesterol goals despite the use of lipid-lowering therapy (including statins). Rosuvastatin is a new and potent statin that produces greater reductions of LDL-cholesterol when compared with other agents in this class. Furthermore, rosuvastatin provides additional benefits in the lipid profile such as increased HDL-cholesterol, and decreased triglycerides, total cholesterol, apolipoprotein B and apolipoprotein B:A-1 ratio. Cardiovascular disease is a continuum: from risk factors to subclinical organ damage and finally to overt clinical cardiovascular disease. Several trials have investigated the effects of rosuvastatin along this cardiovascular continuum. The results provided by the GALAXY program emphasize the importance of the early treatment with rosuvastatin in the cardiovascular continuum to achieve the greatest benefit. In this paper, the efficacy and safety of rosuvastatin along the cardiovascular continuum is reviewed. PMID:19900015

  8. Conductivity of continuum percolating systems

    NASA Astrophysics Data System (ADS)

    Stenull, Olaf; Janssen, Hans-Karl

    2001-11-01

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

  9. Micropolar continuum in spatial description

    NASA Astrophysics Data System (ADS)

    Ivanova, Elena A.; Vilchevskaya, Elena N.

    2016-06-01

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

  10. Continuum Fitting HST QSO Spectra

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  11. Field-Induced Rheology in Uniaxial and Biaxial Fields

    SciTech Connect

    MARTIN, JAMES E.

    1999-10-22

    Steady and oscillatory shear 3-D simulations of electro- and magnetorheology in uniaxial and biaxial fields are presented, and compared to the predictions of the chain model. These large scale simulations are three dimensional, and include the effect of Brownian motion. In the absence of thermal fluctuations, the expected shear thinning viscosity is observed in steady shear, and a striped phase is seen to rapidly form in a uniaxial field, with a shear slip zone in each sheet. However, as the influence of Brownian motion increases, the fluid stress decreases, especially at lower Mason numbers, and the striped phase eventually disappears, even when the fluid stress is still high. In a biaxial field, an opposite trend is seen, where Brownian motion decreases the stress most significantly at higher Mason numbers. to account for the uniaxial steady shear data they propose a microscopic chain model of the role played by thermal fluctuations on the rheology of ER and MR fluids that delineates the regimes where an applied field can impact the fluid viscosity, and gives an analytical prediction for the thermal effect. In oscillatory shear, a striped phase again appears in uniaxial field, at strain amplitudes greater than {approx} 0.15, and the presence of a shear slip zone creates strong stress nonlinearities at low strain amplitudes. In a biaxial field, a shear slip zone is not created, and so the stress nonlinearities develop only at expected strain amplitudes. The nonlinear dynamics of these systems is shown to be in good agreement with the Kinetic Chain Model.

  12. Turbulent fluid motion 3: Basic continuum equations

    NASA Technical Reports Server (NTRS)

    Deissler, Robert G.

    1991-01-01

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

  13. A continuum model for interconnected lattice trusses

    NASA Technical Reports Server (NTRS)

    Balakrishnan, A. V.

    1992-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Guberman, Steven L.

    1993-01-01

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

  15. Electric-field-induced interfacial instabilities of a soft elastic membrane confined between viscous layers

    NASA Astrophysics Data System (ADS)

    Dey, Mohar; Bandyopadhyay, Dipankar; Sharma, Ashutosh; Qian, Shizhi; Joo, Sang Woo

    2012-10-01

    We explore the electric-field-induced interfacial instabilities of a trilayer composed of a thin elastic film confined between two viscous layers. A linear stability analysis (LSA) is performed to uncover the growth rate and length scale of the different unstable modes. Application of a normal external electric field on such a configuration can deform the two coupled elastic-viscous interfaces either by an in-phase bending or an antiphase squeezing mode. The bending mode has a long-wave nature, and is present even at a vanishingly small destabilizing field. In contrast, the squeezing mode has finite wave-number characteristics and originates only beyond a threshold strength of the electric field. This is in contrast to the instabilities of the viscous films with multiple interfaces where both modes are found to possess long-wave characteristics. The elastic film is unstable by bending mode when the stabilizing forces due to the in-plane curvature and the elastic stiffness are strong and the destabilizing electric field is relatively weak. In comparison, as the electric field increases, a subdominant squeezing mode can also appear beyond a threshold destabilizing field. A dominant squeezing mode is observed when the destabilizing field is significantly strong and the elastic films are relatively softer with lower elastic modulus. In the absence of liquid layers, a free elastic film is also found to be unstable by long-wave bending and finite wave-number squeezing modes. The LSA asymptotically recovers the results obtained by the previous formulations where the membrane bending elasticity is approximately incorporated as a correction term in the normal stress boundary condition. Interestingly, the presence of a very weak stabilizing influence due to a smaller interfacial tension at the elastic-viscous interfaces opens up the possibility of fabricating submicron patterns exploiting the instabilities of a trilayer.

  16. Electric-field-induced weakly chaotic transients in ferroelectric liquid crystals.

    PubMed

    Śliwa, I; Jeżewski, W; Kuczyński, W

    2016-01-01

    Nonlinear dynamics induced in surface stabilized ferroelectric liquid crystals by strong alternating external electric fields is studied both theoretically and experimentally. As has already been shown, molecular reorientations induced by sufficiently strong fields of high-enough frequencies can reveal a long transient behavior that has a weakly chaotic character. The resulting complex dynamics of ferroelectric liquid crystals can be considered not only as a consequence of irregular motions of particular molecules but also as a repercussion of a surface-enforced partial decorrelation of nonlinear molecular motions within smectic layers. To achieve more insight into the nature of this phenomenon and to show that the underlying complex field-induced behavior of smectic liquid crystals is not exceptional, ranges of system parameters for which the chaotic behavior occurs are determined. It is proved that there exists a large enough set of initial phase trajectory points, for which weakly chaotic long-time transitory phenomena occur, and, thereby, it is demonstrated that such a chaotic behavior can be regarded as being typical for strongly field-driven thin liquid crystal systems. Additionally, the influence of low-amplitude random noise on the duration of the transient processes is numerically studied. The strongly nonlinear contribution to the electro-optic response, experimentally determined for liquid crystal samples at frequencies lower than the actual field frequency, is also analyzed for long-time signal sequences. Using a statistical approach to distinguish numerically response signals of samples from noise generated by measuring devices, it is shown that the distribution of sample signals distinctly differs from the device noise. This evidently corroborates the occurrence of the nonlinear low-frequency effect, found earlier for different surface stabilized liquid crystal samples. PMID:26871130

  17. Effective long-range interlayer interactions and electric-field-induced subphases in ferrielectric liquid crystals

    NASA Astrophysics Data System (ADS)

    Chandani, A. D. L.; Fukuda, Atsuo; Vij, Jagdish K.; Takanishi, Yoichi; Iida, Atsuo

    2016-04-01

    Microbeam resonant x-ray scattering experiments recently revealed the sequential emergence of electric-field-induced subphases (stable states) with exceptionally large unit cells consisting of 12 and 15 smectic layers. We explain the emergence of the field-induced subphases by the quasimolecular model based on the Emelyanenko-Osipov long-range interlayer interactions (LRILIs) together with our primitive way of understanding the frustration in clinicity using the qE number defined as qE=|[R ] -[L ] | /([R ] +[L ] ) ; here [R ] and [L ] refer to the numbers of smectic layers with directors tilted to the right and to the left, respectively, in the unit cell of a field-induced subphase. We show that the model actually stabilizes the field-induced subphases with characteristic composite unit cells consisting of several blocks, each of which is originally a ferrielectric three-layer unit cell stabilized by the LRILIs, but some of which would be modified to become ferroelectric by an applied electric field. In a similar line of thought, we also try to understand the puzzling electric-field-induced birefringence data in terms of the LRILIs.

  18. Field-induced activation of metal oxide semiconductor for low temperature flexible transparent electronic device applications

    NASA Astrophysics Data System (ADS)

    Pudasaini, Pushpa Raj; Noh, Joo Hyon; Wong, Anthony; Haglund, Amada; Ward, Thomas Zac; Mandrus, David; Rack, Philip

    Amorphous metal-oxide semiconductors have been extensively studied as an active channel material in thin film transistors due to their high carrier mobility, and excellent large-area uniformity. Here, we report the athermal activation of amorphous indium gallium zinc oxide semiconductor channels by an electric field-induced oxygen migration via gating through an ionic liquid. Using field-induced activation, a transparent flexible thin film transistor is demonstrated on a polyamide substrate with transistor characteristics having a current ON-OFF ratio exceeding 108, and saturation field effect mobility of 8.32 cm2/(V.s) without a post-deposition thermal treatment. This study demonstrates the potential of field-induced activation as an athermal alternative to traditional post-deposition thermal annealing for metal oxide electronic devices suitable for transparent and flexible polymer substrates. Materials Science and Technology Division, ORBL, Oak Ridge, TN 37831, USA.

  19. Ultrasonic propagation: a technique to reveal field induced structures in magnetic nanofluids.

    PubMed

    Parekh, Kinnari; Patel, Jaykumar; Upadhyay, R V

    2015-07-01

    The paper reports the study of magnetic field induced structures in magnetic nanofluid investigated through ultrasonic wave propagation. Modified Tarapov's theory is used to study variation in velocity anisotropy with magnetic field. The types of field induced structures depend upon the chemical structure of the carrier in which magnetic nanoparticles are dispersed. Our study indicates formation of fractals and chain respectively, in transformer oil and kerosene based fluid. This difference is explained on the basis of particle-particle interaction and particle-medium interaction. PMID:25791205

  20. MIRO Continuum Calibration for Asteroid Mode

    NASA Technical Reports Server (NTRS)

    Lee, Seungwon

    2011-01-01

    MIRO (Microwave Instrument for the Rosetta Orbiter) is a lightweight, uncooled, dual-frequency heterodyne radiometer. The MIRO encountered asteroid Steins in 2008, and during the flyby, MIRO used the Asteroid Mode to measure the emission spectrum of Steins. The Asteroid Mode is one of the seven modes of the MIRO operation, and is designed to increase the length of time that a spectral line is in the MIRO pass-band during a flyby of an object. This software is used to calibrate the continuum measurement of Steins emission power during the asteroid flyby. The MIRO raw measurement data need to be calibrated in order to obtain physically meaningful data. This software calibrates the MIRO raw measurements in digital units to the brightness temperature in Kelvin. The software uses two calibration sequences that are included in the Asteroid Mode. One sequence is at the beginning of the mode, and the other at the end. The first six frames contain the measurement of a cold calibration target, while the last six frames measure a warm calibration target. The targets have known temperatures and are used to provide reference power and gain, which can be used to convert MIRO measurements into brightness temperature. The software was developed to calibrate MIRO continuum measurements from Asteroid Mode. The software determines the relationship between the raw digital unit measured by MIRO and the equivalent brightness temperature by analyzing data from calibration frames. The found relationship is applied to non-calibration frames, which are the measurements of an object of interest such as asteroids and other planetary objects that MIRO encounters during its operation. This software characterizes the gain fluctuations statistically and determines which method to estimate gain between calibration frames. For example, if the fluctuation is lower than a statistically significant level, the averaging method is used to estimate the gain between the calibration frames. If the

  1. Continuum methods in lattice perturbation theory

    SciTech Connect

    Becher, Thomas G

    2002-11-15

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

  2. Electro-optic contribution to field-induced Raman scattering in alkali halides

    SciTech Connect

    Subbaswamy, K.R.; Mahan, G.D.

    1985-10-15

    The electro-optic contribution to the field-induced first-order Raman scattering cross section in alkali halide crystals is calculated using measured values for hyperpolarizabilities. The electro-optic contribution is much larger than the previously reported atomic displacement contribution. The results cast some doubt on the accuracy of the reported hyperpolarizability values.

  3. Periodic amplitude variations in Jovian continuum radiation

    NASA Astrophysics Data System (ADS)

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

    1986-12-01

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

  4. Commitment to Quality throughout the Continuum.

    ERIC Educational Resources Information Center

    Gillet, Pamela

    1995-01-01

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

  5. Application of continuum- and hybrid models in karst spring catchments

    NASA Astrophysics Data System (ADS)

    Rehrl, Christoph; Birk, Steffen

    2010-05-01

    further implies that inferences of aquifer properties from spring hydrographs are potentially impaired by ignoring turbulent flow effects. Thus, the adequate representation of turbulent flow in karst models might deserve equal or even more attention than the general pros and cons of continuum and hybrid models discussed in the literature. Moreover this study focuses on the applicability of the single-continuum approach (CFP mode 2) regarding the typical discharge dynamics of spring catchments. The continuum model is currently tested using the well investigated Gallusquelle catchment (Schwäbische Alb, Germany). The Gallusquelle hydrograph show significant variations in the spring discharge while the hydraulic head within the catchment changes only moderately. This strong variability within the hydrograph was already modelled using a double-continuum model but poses a serious challenge when using the lower-parameterised single-continuum approach.

  6. Noise scaling in continuum percolating films

    NASA Astrophysics Data System (ADS)

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

    1985-07-01

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

  7. Geometric continuum regularization of quantum field theory

    SciTech Connect

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

    1989-11-08

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

  8. Continuum absorption in the vicinity of the toroidicity-induced Alfvén gap

    NASA Astrophysics Data System (ADS)

    Li, Meng; Breizman, Boris; Zheng, Linjin

    2015-11-01

    This work examines the resonant dissipative response of the Alfvén continuum to an oscillating driving current when the driving frequency is slightly outside the edges of the toroidicity-induced spectral gap. The problem is motivated by the need to the describe the continuum absorption in the frequency chirping events for energetic-particle-driven modes. A key element of this problem is the negative interference of the two closely spaced continuum crossing points. We explain why the continuum absorption can have very different features. This difference is closely related to the Toroidicity-induced Alfvén Eigenmode(TAE) theory that the eigenmode frequency can be arbitrarily close to the upper edge of the gap, whereas the lower edge of the gap is always a finite distance away from the closest eigenmode. This work was supported by the U.S. Department of Energy Contracts DE-FG02-04ER-54742.

  9. Polarizable Atomic Multipole Solutes in a Poisson-Boltzmann Continuum

    PubMed Central

    Schnieders, Michael J.; Baker, Nathan A.; Ren, Pengyu; Ponder, Jay W.

    2008-01-01

    Modeling the change in the electrostatics of organic molecules upon moving from vacuum into solvent, due to polarization, has long been an interesting problem. In vacuum, experimental values for the dipole moments and polarizabilities of small, rigid molecules are known to high accuracy; however, it has generally been difficult to determine these quantities for a polar molecule in water. A theoretical approach introduced by Onsager used vacuum properties of small molecules, including polarizability, dipole moment and size, to predict experimentally known permittivities of neat liquids via the Poisson equation. Since this important advance in understanding the condensed phase, a large number of computational methods have been developed to study solutes embedded in a continuum via numerical solutions to the Poisson-Boltzmann equation (PBE). Only recently have the classical force fields used for studying biomolecules begun to include explicit polarization in their functional forms. Here we describe the theory underlying a newly developed Polarizable Multipole Poisson-Boltzmann (PMPB) continuum electrostatics model, which builds on the Atomic Multipole Optimized Energetics for Biomolecular Applications (AMOEBA) force field. As an application of the PMPB methodology, results are presented for several small folded proteins studied by molecular dynamics in explicit water as well as embedded in the PMPB continuum. The dipole moment of each protein increased on average by a factor of 1.27 in explicit water and 1.26 in continuum solvent. The essentially identical electrostatic response in both models suggests that PMPB electrostatics offers an efficient alternative to sampling explicit solvent molecules for a variety of interesting applications, including binding energies, conformational analysis, and pKa prediction. Introduction of 150 mM salt lowered the electrostatic solvation energy between 2–13 kcal/mole, depending on the formal charge of the protein, but had only a

  10. 34 CFR 300.115 - Continuum of alternative placements.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

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

  11. Influence of thermal agitation on the electric field induced precessional magnetization reversal with perpendicular easy axis

    SciTech Connect

    Cheng, Hongguang Deng, Ning

    2013-12-15

    We investigated the influence of thermal agitation on the electric field induced precessional magnetization switching probability with perpendicular easy axis by solving the Fokker-Planck equation numerically with finite difference method. The calculated results show that the thermal agitation during the reversal process crucially influences the switching probability. The switching probability can be achieved is only determined by the thermal stability factor Δ of the free layer, it is independent on the device dimension, which is important for the high density device application. Ultra-low error rate down to the order of 10{sup −9} can be achieved for the device of thermal stability factor Δ of 40. Low damping factor α material should be used for the free layer for high reliability device applications. These results exhibit potential of electric field induced precessional magnetization switching with perpendicular easy axis for ultra-low power, high speed and high density magnetic random access memory (MRAM) applications.

  12. Fields induced by three-dimensional dislocation loops in anisotropic magneto-electro-elastic bimaterials

    NASA Astrophysics Data System (ADS)

    Han, Xueli; Pan, Ernie; Sangghaleh, Ali

    2013-08-01

    The coupled elastic, electric and magnetic fields produced by an arbitrarily shaped three-dimensional dislocation loop in general anisotropic magneto-electro-elastic (MEE) bimaterials are derived. First, we develop line-integral expressions for the fields induced by a general dislocation loop. Then, we obtain analytical solutions for the fields, including the extended Peach-Koehler force, due to some useful dislocation segments such as straight line and elliptic arc. The present solutions contain the piezoelectric, piezomagnetic and purely elastic solutions as special cases. As numerical examples, the fields induced by a square and an elliptic dislocation loop in MEE bimaterials are studied. Our numerical results show the coupling effects among different fields, along with various interesting features associated with the dislocation and interface.

  13. In situ imaging of field-induced hexagonal columns in magnetite ferrofluids.

    PubMed

    Klokkenburg, Mark; Erné, Ben H; Meeldijk, Johannes D; Wiedenmann, Albrecht; Petukhov, Andrei V; Dullens, Roel P A; Philipse, Albert P

    2006-11-01

    Field-induced structures in a ferrofluid with well-defined magnetite nanoparticles with a permanent magnetic dipole moment are analyzed on a single-particle level by in situ cryogenic transmission electron microscopy (2D). The field-induced columnar phase locally exhibits hexagonal symmetry and confirms the structures observed in simulations for ferromagnetic dipolar fluids in 2D. The columns are distorted by lens-shaped voids, due to the weak interchain attraction relative to field-directed dipole-dipole attraction. Both dipolar coupling and the dipole concentration determine the dimensions and the spatial arrangement of the columns. Their regular spacing manifests long-range end-pole repulsions that eventually dominate the fluctuation-induced attractions between dipole chains that initiate the columnar transition. PMID:17155554

  14. Electric field induced by collective vortex creep in superconductors with fractal clusters of normal phase

    NASA Astrophysics Data System (ADS)

    Kuzmin, Yu. I.; Pleshakov, I. V.

    2016-02-01

    The influence of the collective creep of magnetic flux on the electric field induced in a superconducting composite with fractal cluster structure is considered. Current-voltage ( I- V) characteristics of these superconductors are determined with allowance for the influence of the fractal dimensionality of boundaries of the normal phase clusters and the height of pinning barriers on the nonlinearity of I- V characteristics at small transport currents. A relationship is established between the collective pinning and vortex glass state that is formed in superconductors with a fractal cluster structure. It is shown that the intensity of an electric field induced in the case of collective creep is smaller than that for Anderson-Kim creep.

  15. Control of magnetic relaxation by electric-field-induced ferroelectric phase transition and inhomogeneous domain switching

    NASA Astrophysics Data System (ADS)

    Nan, Tianxiang; Emori, Satoru; Peng, Bin; Wang, Xinjun; Hu, Zhongqiang; Xie, Li; Gao, Yuan; Lin, Hwaider; Jiao, Jie; Luo, Haosu; Budil, David; Jones, John G.; Howe, Brandon M.; Brown, Gail J.; Liu, Ming; Sun, Nian

    2016-01-01

    Electric-field modulation of magnetism in strain-mediated multiferroic heterostructures is considered a promising scheme for enabling memory and magnetic microwave devices with ultralow power consumption. However, it is not well understood how electric-field-induced strain influences magnetic relaxation, an important physical process for device applications. Here, we investigate resonant magnetization dynamics in ferromagnet/ferroelectric multiferroic heterostructures, FeGaB/PMN-PT and NiFe/PMN-PT, in two distinct strain states provided by electric-field-induced ferroelectric phase transition. The strain not only modifies magnetic anisotropy but also magnetic relaxation. In FeGaB/PMN-PT, we observe a nearly two-fold change in intrinsic Gilbert damping by electric field, which is attributed to strain-induced tuning of spin-orbit coupling. By contrast, a small but measurable change in extrinsic linewidth broadening is attributed to inhomogeneous ferroelastic domain switching during the phase transition of the PMN-PT substrate.

  16. Direct measurements of the magnetic field induced by optically polarized sup 3 He atoms

    SciTech Connect

    Gudoshnikov, S.A.; Snigirev, O.V. ); Kozlov, A.N.; Maslennikov, Y.V.; Serebrjakov, A.Y. )

    1991-03-01

    This paper reports on an alternative magnetic field induced by the standard cell of the optically pumped {sup 3}He magnetometer directly measured by the SQUID-based second-order gradiometer with signal-to-noise ratio higher than 6. The magnitude of the measured field equal to 5 {times} 10{sup {minus}13} T at the 5-cm distance from the cell axis and transverse relaxation time T{sub 2} equal to 7 minutes have been found.

  17. Electron correlations in semiconductors: Bulk cohesive properties and magnetic-field-induced Wigner crystal at heterojunctions

    SciTech Connect

    Louie, S.G.; Zhu, X.

    1992-08-01

    A correlated wavefunction variational quantum Monte Carlo approach to the studies of electron exchange and correlation effects in semiconductors is presented. Applications discussed include the cohesive and structural properties of bulk semiconductors, and the magnetic-field-induced Wigner electron crystal in two dimensions. Landau level mixing is shown to be important in determining the transition between the quantum Hall liquid and the Wigner crystal states in the regime of relevant experimental parameters.

  18. A luminescent heptanuclear DyIr6 complex showing field-induced slow magnetization relaxation.

    PubMed

    Zeng, Dai; Ren, Min; Bao, Song-Song; Li, Li; Zheng, Li-Min

    2014-08-01

    The first example of iridium/lanthanide phosphonates, i.e. [DyIr6(ppy)12(bpp)2(bppH)4](CF3SO3)·8H2O (1) (ppy(-) = 2-phenylpyridine, bpp(2-) = 2-pyridylphosphonate) is reported. It shows dual functions with the photoluminescence and field-induced slow magnetization relaxation originating from the Ir and Dy moieties, respectively. PMID:24942060

  19. Microstructural and continuum evolution modeling of sintering.

    SciTech Connect

    Braginsky, Michael V.; Olevsky, Eugene A.; Johnson, D. Lynn; Tikare, Veena; Garino, Terry J.; Arguello, Jose Guadalupe, Jr.

    2003-12-01

    deformation during. The continuum portion is based on a finite element formulation that allows 3D components to be modeled using SNL's nonlinear large-deformation finite element code, JAS3D. This tool provides a capability to model sintering of complex three-dimensional components. The model was verified by comparing to simulations results published in the literature. The model was validated using experimental results from various laboratory experiments performed by Garino. In addition, the mesoscale simulations were used to study anisotropic shrinkage in aligned, elongated powder compacts. Anisotropic shrinkage occurred in all compacts with aligned, elongated particles. However, the direction of higher shrinkage was in some cases along the direction of elongation and in other cases in the perpendicular direction depending on the details of the powder compact. In compacts of simple-packed, mono-sized, elongated particles, shrinkage was higher in the direction of elongation. In compacts of close-packed, mono-sized, elongated particles and of elongated particles with a size and shape distribution, the shrinkage was lower in the direction of elongation. We also explored the concept of a sintering stress tensor rather than the traditional sintering stress scalar concept for the case of anisotropic shrinkage. A thermodynamic treatment of this is presented. A method to calculate the sintering stress tensor is also presented. A user-friendly code that can simulate microstructural evolution during sintering in 2D and in 3D was developed. This code can run on most UNIX platforms and has a motif-based GUI. The microstructural evolution is shown as the code is running and many of the microstructural features, such as grain size, pore size, the average grain boundary length (in 2D) and area (in 3D), etc. are measured and recorded as a function of time. The overall density as the function of time is also recorded.

  20. Continuum Absorption Coefficient of Atoms and Ions

    NASA Technical Reports Server (NTRS)

    Armaly, B. F.

    1979-01-01

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

  1. Defining and testing a granular continuum element

    SciTech Connect

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

    2007-12-03

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

  2. A Radio Continuum Study of Dwarf Galaxies: 6 cm imaging of LITTLE THINGS

    NASA Astrophysics Data System (ADS)

    Kitchener, Ben; Brinks, Elias; Heesen, Volker; Hunter, Deidre Ann; Zhang, Hongxin; Rau, Urvashi; Rupen, Michael P.; Little Things Collaboration

    2015-01-01

    To bypass uncertainties introduced by extinction caused by dust at optical wavelengths, we examine to what extent the radio continuum can probe star formation (SF) in dwarf galaxies. We provide VLA 6-cm C-array (4 to 8 GHz) radio continuum images with integrated flux densities for 40 dwarf galaxies taken from LITTLE THINGS. We find 27 harbor significant emission coincident with SF tracers; 17 are new detections. We infer the average thermal fraction to be 39 +- 25%. The LITTLE THINGS galaxies follow the Condon radio continuum - star formation rate (SFR) relation down to an SFR of 0.1 Msol/yr. At lower rates they follow a power-law characterized by a slope of 1.2 +- 0.1 with a scatter of 0.2 dex . We interpret this as an underproduction of the non-thermal radio continuum component. When considering the non-thermal radio continuum to star formation rate slope on its own, we find the slope to be 1.2. The magnetic field strength we find is typically 9.4 +- 3.8 muG in and around star forming regions which is similar to that in spiral galaxies. In a few dwarfs, the magnetic field strength can reach as high as 30 muG in localized 100 pc star forming regions. The underproduction of non-thermal radio continuum is likely due to the escape of Cosmic Ray electrons from the galaxy. The LITTLE THINGS galaxies are consistent with the radio continuum - far infrared luminosity relation. We observe a power-law slope of 1.06 +- 0.08 with a scatter of 0.24 dex which suggests that the 'conspiracy' of the radio continuum - far infrared relation continues to hold even for dwarf galaxies.

  3. Continuum damping of ideal toroidal Alfven eigenmodes

    SciTech Connect

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

    1993-08-01

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

  4. Stratospheric infrared continuum absorptions observed by the ATMOS instrument

    NASA Technical Reports Server (NTRS)

    Rinsland, C. P.; Zander, R.; Namkung, J. S.; Farmer, C. B.; Norton, R. H.

    1989-01-01

    A quantitative analysis of infrared continuum absorption features observed in ATMOS/Spacelab 3 (1985) spectra of the lower stratosphere is reported. Continuous absorption produced primarily by the collision-induced fundamental vibration-rotation band of O2 and to a lesser extent by the superposition of H2O far line wings has been observed in the 1400 to 1800/cm interval below tangent heights of about 25 km. Continuum optical depths measured in microwindows nearly free of atmospheric line absorption are 0.78 + or - 0.06 times those calculated with the O2 absorption coefficients of Timofeyev and Tonkov (1978). Transmittance measurements in microwindows between 2395 and 2535/cm have been used to study continuous absorption from the collision induced fundamental vibration-rotation band of N2 and the far wings of strong CO2 lines. The measured transmittances have been analyzed to derive best fit absorption coefficients for the N2 pressure-induced band at lower stratospheric temperatures (about 210 K).

  5. Understanding the Continuum Spectra of Short Soft Gamma Repeater Bursts

    NASA Technical Reports Server (NTRS)

    Gogus, Ersin; Woods, Peter M.; Kouveliotou, Chryssa; Finger, Mark H.; Lenter, Geoffrey; Patel, Sandeep K.; Swank, Jean

    2006-01-01

    The spectra of short soft gamma repeater (SGR) bursts at photon energies above -15 keV are often well described by an optically thin thermal bremsstrahlung model (i.e., F(E) - E^-1 * exp(-E/kT) ) with kT=20-40 keV. However, the spectral shape burst continuum at lower photon energies (down to -2 keV) is not well established. It is important to better understand the SGR burst spectral properties at lower energies since inadequate description of the burst spectral continuum could lead to incorrect conclusions, such as existence of spectral lines. Here, we present detailed spectral investigations (in 2-200 keV) of 163 bursts from SGR 1806-20, all detected with Rossi X-ray Timing Explorer during the 2004 active episode that included the giant flare on 27 December 2004. We find that the great majority of burst spectra are well represented by the combination of a blackbody plus a OTTB models.

  6. Continuum absorption in the vicinity of the toroidicity-induced Alfvén gap

    NASA Astrophysics Data System (ADS)

    Li, M.; Breizman, B. N.; Zheng, L. J.; Chen, Eugene Y.

    2015-12-01

    Excitation of Alfvén modes is commonly viewed as a concern for energetic particle confinement in burning plasmas. The 3.5 MeV alpha particles produced by fusion may be affected as well as other fast ions in both present and future devices. Continuum damping of such modes is one of the key factors that determine their excitation thresholds and saturation levels. This work examines the resonant dissipative response of the Alfvén continuum to an oscillating driving current when the driving frequency is slightly outside the edges of the toroidicity-induced spectral gap. The problem is largely motivated by the need to describe the continuum absorption in the frequency sweeping events. A key element of this problem is the negative interference of the two closely spaced continuum crossing points. We explain why the lower and upper edges of the gap can have very different continuum absorption features. The difference is associated with an eigenmode whose frequency can be arbitrarily close to the upper edge of the gap whereas the lower edge of the gap is always a finite distance away from the closest eigenmode.

  7. Continuum absorption in the vicinity of the toroidicity-induced Alfvén gap

    SciTech Connect

    Li, M.; Breizman, B. N.; Zheng, L. J.; Chen, Eugene Y.

    2015-12-04

    Excitation of Alfvén modes is commonly viewed as a concern for energetic particle confinement in burning plasmas. The 3.5 MeValpha particles produced by fusion may be affected as well as other fast ions in both present and future devices. Continuum damping of such modes is one of the key factors that determine their excitation thresholds and saturation levels. This work examines the resonant dissipative response of the Alfvén continuum to an oscillating driving current when the driving frequency is slightly outside the edges of the toroidicity-induced spectral gap. The problem is largely motivated by the need to describe the continuum absorption in the frequency sweeping events. Akey element of this problem is the negative interference of the two closely spaced continuum crossing points.Weexplain why the lower and upper edges of the gap can have very different continuum absorption features. Lastly, the difference is associated with an eigenmode whose frequency can be arbitrarily close to the upper edge of the gap whereas the lower edge of the gap is always a finite distance away from the closest eigenmode.

  8. Modal kinematics for multisection continuum arms.

    PubMed

    Godage, Isuru S; Medrano-Cerda, Gustavo A; Branson, David T; Guglielmino, Emanuele; Caldwell, Darwin G

    2015-06-01

    This paper presents a novel spatial kinematic model for multisection continuum arms based on mode shape functions (MSF). Modal methods have been used in many disciplines from finite element methods to structural analysis to approximate complex and nonlinear parametric variations with simple mathematical functions. Given certain constraints and required accuracy, this helps to simplify complex phenomena with numerically efficient implementations leading to fast computations. A successful application of the modal approximation techniques to develop a new modal kinematic model for general variable length multisection continuum arms is discussed. The proposed method solves the limitations associated with previous models and introduces a new approach for readily deriving exact, singularity-free and unique MSF's that simplifies the approach and avoids mode switching. The model is able to simulate spatial bending as well as straight arm motions (i.e., pure elongation/contraction), and introduces inverse position and orientation kinematics for multisection continuum arms. A kinematic decoupling feature, splitting position and orientation inverse kinematics is introduced. This type of decoupling has not been presented for these types of robotic arms before. The model also carefully accounts for physical constraints in the joint space to provide enhanced insight into practical mechanics and impose actuator mechanical limitations onto the kinematics thus generating fully realizable results. The proposed method is easily applicable to a broad spectrum of continuum arm designs. PMID:25969947

  9. An oculomotor continuum from exploration to fixation

    PubMed Central

    Otero-Millan, Jorge; Macknik, Stephen L.; Langston, Rachel E.; Martinez-Conde, Susana

    2013-01-01

    During visual exploration, saccadic eye movements scan the scene for objects of interest. During attempted fixation, the eyes are relatively still but often produce microsaccades. Saccadic rates during exploration are higher than those of microsaccades during fixation, reinforcing the classic view that exploration and fixation are two distinct oculomotor behaviors. An alternative model is that fixation and exploration are not dichotomous, but are instead two extremes of a functional continuum. Here, we measured the eye movements of human observers as they either fixed their gaze on a small spot or scanned natural scenes of varying sizes. As scene size diminished, so did saccade rates, until they were continuous with microsaccadic rates during fixation. Other saccadic properties varied as function of image size as well, forming a continuum with microsaccadic parameters during fixation. This saccadic continuum extended to nonrestrictive, ecological viewing conditions that allowed all types of saccades and fixation positions. Eye movement simulations moreover showed that a single model of oculomotor behavior can explain the saccadic continuum from exploration to fixation, for images of all sizes. These findings challenge the view that exploration and fixation are dichotomous, suggesting instead that visual fixation is functionally equivalent to visual exploration on a spatially focused scale. PMID:23533278

  10. Clinical Integration Managing across the care continuum.

    PubMed

    Karash, Julius A; Larson, Laurie

    2016-06-01

    In the changing world of health care, the traditional boundaries are vanishing and hospitals and others must integrate care within their own organizations, as well as externally, across the care continuum. Here are three approaches to accomplishing just that. PMID:27468454

  11. Parental Involvement to Parental Engagement: A Continuum

    ERIC Educational Resources Information Center

    Goodall, Janet; Montgomery, Caroline

    2014-01-01

    Based on the literature of the field, this article traces a continuum between parental involvement with schools, and parental engagement with children's learning. The article seeks to shed light on an area of confusion; previous research has shown that different stakeholder groups understand "parental engagement" in different ways.…

  12. Continuum treatment of electronic polarization effect.

    PubMed

    Tan, Yu-Hong; Luo, Ray

    2007-03-01

    A continuum treatment of electronic polarization has been explored for in molecular mechanics simulations in implicit solvents. The dielectric constant for molecule interior is the only parameter in the continuum polarizable model. A value of 4 is found to yield optimal agreement with high-level ab initio quantum mechanical calculations for the tested molecular systems. Interestingly, its performance is not sensitive to the definition of molecular volume, in which the continuum electronic polarization is defined. In this model, quantum mechanical electrostatic field in different dielectric environments from vacuum, low-dielectric organic solvent, and water can be used simultaneously in atomic charge fitting to achieve consistent treatment of electrostatic interactions. The tests show that a single set of atomic charges can be used consistently in different dielectric environments and different molecular conformations, and the atomic charges transfer well from training monomers to tested dimers. The preliminary study gives us the hope of developing a continuum polarizable force field for more consistent simulations of proteins and nucleic acids in implicit solvents. PMID:17362100

  13. Continuum treatment of electronic polarization effect

    NASA Astrophysics Data System (ADS)

    Tan, Yu-Hong; Luo, Ray

    2007-03-01

    A continuum treatment of electronic polarization has been explored for in molecular mechanics simulations in implicit solvents. The dielectric constant for molecule interior is the only parameter in the continuum polarizable model. A value of 4 is found to yield optimal agreement with high-level ab initio quantum mechanical calculations for the tested molecular systems. Interestingly, its performance is not sensitive to the definition of molecular volume, in which the continuum electronic polarization is defined. In this model, quantum mechanical electrostatic field in different dielectric environments from vacuum, low-dielectric organic solvent, and water can be used simultaneously in atomic charge fitting to achieve consistent treatment of electrostatic interactions. The tests show that a single set of atomic charges can be used consistently in different dielectric environments and different molecular conformations, and the atomic charges transfer well from training monomers to tested dimers. The preliminary study gives us the hope of developing a continuum polarizable force field for more consistent simulations of proteins and nucleic acids in implicit solvents.

  14. A Multiscale Morphing Continuum Description for Turbulence

    NASA Astrophysics Data System (ADS)

    Chen, James; Wonnell, Louis

    2015-11-01

    Turbulence is a flow physics phenomena invlolving multiple length scales. The popular Navier- Stokes equations only possess one length/time scale. Therefore, extremely fine mesh is needed for DNS attempting to resolve the small scale motion, which comes with a burden of excessive computational cost. For practical application with complex geometries, the research society rely on RANS and LES, which requre turbulence model or subgrid scale (SGS) model for closure problems. Different models not only lead to different results but usually are invalidated on solid physical grounds, such as objectivity and entropy principle.The Morphing Continuum Theory (MCT) is a high-order continuum theory formulated under the framework of thermalmechanics for physics phenomena involving microstructure. In this study, a theoretical perspective for the multiscale nature of the Morphing Continuum Theory is connected with the multiscale nature of turbulence physics. The kinematics, balance laws, constitutive equations and a Morphing Continuum description of turbulence are introduced. The equations were numerically implemented for a zero pressure gradient flat plate. The simulations are compate with the laminar, transitional and turbulence cases.

  15. Aims, Modes, and the Continuum of Discourse.

    ERIC Educational Resources Information Center

    Beale, Walter H.

    A framework for the study of discourse, based on the analysis of three superordinate features of discourse (asymmetry, hierarchy, and continuum), is proposed in this paper. The paper begins by noting the confusion in terminology that exists in the world of composition pedagogy and theory; pointing to the need for a framework for testing,…

  16. 3D holography: from discretum to continuum

    NASA Astrophysics Data System (ADS)

    Bonzom, Valentin; Dittrich, Bianca

    2016-03-01

    We study the one-loop partition function of 3D gravity without cosmological constant on the solid torus with arbitrary metric fluctuations on the boundary. To this end we employ the discrete approach of (quantum) Regge calculus. In contrast with similar calculations performed directly in the continuum, we work with a boundary at finite distance from the torus axis. We show that after taking the continuum limit on the boundary — but still keeping finite distance from the torus axis — the one-loop correction is the same as the one recently found in the continuum in Barnich et al. for an asymptotically flat boundary. The discrete approach taken here allows to identify the boundary degrees of freedom which are responsible for the non-trivial structure of the one-loop correction. We therefore calculate also the Hamilton-Jacobi function to quadratic order in the boundary fluctuations both in the discrete set-up and directly in the continuum theory. We identify a dual boundary field theory with a Liouville type coupling to the boundary metric. The discrete set-up allows again to identify the dual field with degrees of freedom associated to radial bulk edges attached to the boundary. Integrating out this dual field reproduces the (boundary diffeomorphism invariant part of the) quadratic order of the Hamilton-Jacobi functional. The considerations here show that bulk boundary dualities might also emerge at finite boundaries and moreover that discrete approaches are helpful in identifying such dualities.

  17. Structured photoionization continuum of superheated cesium vapor

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  18. Structured photoionization continuum of cesium vapor

    NASA Astrophysics Data System (ADS)

    Pichler, Goran; Makdisi, Yacoub; Kokaj, Jahja; Thomas, Nicky; Mathew, Joseph; AMIP Team

    2015-05-01

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

  19. Some Continuum Aspects of Data Assimilation

    NASA Technical Reports Server (NTRS)

    Cohn, Stephen E.; Menard, Richard

    1999-01-01

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

  20. Continuum modeling of large lattice structures: Status and projections

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.; Mikulas, Martin M., Jr.

    1988-01-01

    The status and some recent developments of continuum modeling for large repetitive lattice structures are summarized. Discussion focuses on a number of aspects including definition of an effective substitute continuum; characterization of the continuum model; and the different approaches for generating the properties of the continuum, namely, the constitutive matrix, the matrix of mass densities, and the matrix of thermal coefficients. Also, a simple approach is presented for generating the continuum properties. The approach can be used to generate analytic and/or numerical values of the continuum properties.

  1. Block versus continuum deformation in the Western United States

    USGS Publications Warehouse

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

    1994-01-01

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

  2. Magnetic field induced suppression of the forward bias current in Bi2Se3/Si Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Jin, Haoming; Hebard, Arthur

    Schottky diodes formed by van der Waals bonding between freshly cleaved flakes of the topological insulator Bi2Se3 and doped silicon substrates show electrical characteristics in good agreement with thermionic emission theory. The motivation is to use magnetic fields to modulate the conductance of the topologically protected conducting surface state. This surface state in close proximity to the semiconductor surface may play an important role in determining the nature of the Schottky barrier. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics were obtained for temperatures in the range 50-300 K and magnetic fields, both perpendicular and parallel to the interface, as high as 7 T. The I-V curve shows more than 6 decades linearity on semi-logarithmic plots, allowing extraction of parameters such as ideality (η), zero-voltage Schottky barrier height (SBH), and series resistance (Rs). In forward bias we observe a field-induced decrease in current which becomes increasingly more pronounced at higher voltages and lower temperature, and is found to be correlated with changes in Rs rather than other barrier parameters. A comparison of changes in Rs in both field direction will be made with magnetoresistance in Bi2Se3 transport measurement. The work is supported by NSF through DMR 1305783.

  3. Dipolar field-induced spin-wave waveguides for spin-torque magnonics

    NASA Astrophysics Data System (ADS)

    Demidov, V. E.; Urazhdin, S.; Zholud, A.; Sadovnikov, A. V.; Demokritov, S. O.

    2015-01-01

    We use high-resolution imaging to study the propagation of spin waves in magnonic waveguides created by the dipolar magnetic fields of microscopic patterns. We show that the characteristics of spin-wave modes in such waveguides depend strongly on their geometry. In particular, by tuning the geometrical parameters, field-induced confinement for both the edge and the center waveguide modes can be achieved, enabling control over the spin-wave transmission characteristics. The studied waveguiding structures are particularly promising for the implementation of magnonic devices utilizing spin-torque phenomena.

  4. A field induced guide-antiguide modulator of GaAs-AlGaAs

    NASA Technical Reports Server (NTRS)

    Huang, T. C.; Chung, Y.; Young, D. B.; Dagli, N.; Coldren, L. A.

    1991-01-01

    A guide-antiguide modulator of GaAs-AlGaAs using the electric-field-induced waveguide concept was demonstrated. The device was formed with a central waveguide electrode sandwiched between two antiguide electrodes on the surface of a p-i-n multiple quantum well (MQW). Switching between lateral guiding and antiguiding was accomplished by reverse biasing either the central electrode or the adjacent electrodes to increase the index beneath these respective regions. The on-off ratio was measured to be 20:1 with a propagation loss of the on-state of about 5 dB/mm.

  5. Magnetic-Field-Induced Rotation of Polarized Light Emission from Monolayer WS2

    NASA Astrophysics Data System (ADS)

    Schmidt, Robert; Arora, Ashish; Plechinger, Gerd; Nagler, Philipp; Granados del Águila, Andrés; Ballottin, Mariana V.; Christianen, Peter C. M.; Michaelis de Vasconcellos, Steffen; Schüller, Christian; Korn, Tobias; Bratschitsch, Rudolf

    2016-08-01

    We control the linear polarization of emission from the coherently emitting K+ and K- valleys (valley coherence) in monolayer WS2 with an out-of-plane magnetic field of up to 25 T. The magnetic-field-induced valley Zeeman splitting causes a rotation of the emission polarization with respect to the excitation by up to 35° and reduces the polarization degree by up to 16%. We explain both of these phenomena with a model based on two noninteracting coherent two-level systems. We deduce that the coherent light emission from the valleys decays with a time constant of τc=260 fs .

  6. Magnetic-field-induced microwave losses in epitaxial Bi-Sr-Ca-Cu-O films

    SciTech Connect

    Silva, E.; Giura, M.; Marcon, R.; Fastampa, R. ); Balestrino, G.; Marinelli, M.; Milani, E. )

    1992-06-01

    Magnetic-field-induced microwave losses in epitaxial {ital c}-axis-oriented Bi-Sr-Ca-Cu-O films have been observed. At low magnetic field, the behavior of the absorption is qualitatively analogous to that already observed in granular samples. The dominant part is attributed to the dephasing of a network of Josephson junctions. A structural analysis shows evidence of such a network. The dependence of the absorption on the angle between the magnetic field and the {ital a}-{ital b} plane is consistent with this model.

  7. Rectifying the Optical-Field-Induced Current in Dielectrics: Petahertz Diode

    NASA Astrophysics Data System (ADS)

    Lee, J. D.; Yun, Won Seok; Park, Noejung

    2016-02-01

    Investigating a theoretical model of the optical-field-induced current in dielectrics driven by strong few-cycle laser pulses, we propose an asymmetric conducting of the current by forming a heterojunction made of two distinct dielectrics with a low hole mass (mh*≪me*) and low electron mass (me*≪mh* ), respectively. This proposition introduces the novel concept of a petahertz (1015 Hz ) diode to rectify the current in the petahertz domain, which should be a key ingredient for the electric signal manipulation of future light-wave electronics. Further, we suggest the candidate dielectrics for the heterojunction.

  8. Electric field induced localization phenomena in a ladder network with superlattice configuration: Effect of backbone environment

    NASA Astrophysics Data System (ADS)

    Dutta, Paramita; Maiti, Santanu K.; Karmakar, S. N.

    2014-09-01

    Electric field induced localization properties of a tight-binding ladder network in presence of backbone sites are investigated. Based on Green's function formalism we numerically calculate two-terminal transport together with density of states for different arrangements of atomic sites in the ladder and its backbone. Our results lead to a possibility of getting multiple mobility edges which essentially plays a switching action between a completely opaque to fully or partly conducting region upon the variation of system Fermi energy, and thus, support in fabricating mesoscopic or DNA-based switching devices.

  9. Field induced polarization and magnetization behaviour of Gd-doped lead magnesium niobate ceramics

    NASA Astrophysics Data System (ADS)

    Pandey, Adityanarayan; Gupta, Surya Mohan; Nigam, Arun Kumar

    2016-05-01

    Both superparaelectric and superparamagnetic behaviour has been observed in rare earth magnetic ion Gd3+ doped Lead Magnesium Niobate (Gd-PMN). Field induced polarization and magnetization studies reveal hystresis loss free P-E and M-H loop at 300K and 5K, respectively. Temperature dependence of inverse susceptibility plot shows deviation at a temperature "td" when fitted with the Curie-Weiss law. This deviation has been attributed to transition from paramagnetic to superparamagnetic behaviour as reported in amorphous Pd-Ni-Fe-P alloys.

  10. Field-induced macroscopic barrier model for persistent photoconductivity in nanocrystalline oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Choi, Hyun-Sik; Jeon, Sanghun

    2014-03-01

    Persistent photoconductivity (PPC) in nanocrystalline InZnO thin-film transistors (TFTs) was studied using carrier fluctuation measurements and transient analysis. Low-frequency noise measurements and decay kinetics indicate that the band bending by the external field together with the ionized oxygen vacancy (Vo++) generated during the light exposure is the main cause of the PPC phenomenon. Based on these observations, a field-induced macroscopic barrier model is proposed as the origin of PPC for InZnO TFTs. In particular, this model explains that the carrier separation between e and Vo++ is induced by the external field applied to the three electrodes inside the transistor.

  11. Homochiral mononuclear Dy-Schiff base complexes showing field-induced double magnetic relaxation processes.

    PubMed

    Ren, Min; Xu, Zhong-Li; Wang, Ting-Ting; Bao, Song-Song; Zheng, Ze-Hua; Zhang, Zai-Chao; Zheng, Li-Min

    2016-01-14

    A pair of enantiopure mononuclear dysprosium/salen-type complexes (Et3NH)[Dy((R,R)/(S,S)-3-NO2salcy)2] (/), where 3-NO2salcyH2 represents N,N'-(1,2-cyclohexanediylethylene)bis(3-nitrosalicylideneiminato), are reported. The enantiomer contains two crystallographically independent dysprosium(iii) ions, each chelated by two enantiopure 3-NO2salcy(2-) ligands forming a [DyN4O4] core. Detailed magnetic studies on compound reveal a field-induced dual magnetic relaxation behavior, originating from single ion anisotropy and intermolecular interactions, respectively. PMID:26621766

  12. Field-Induced Lifshitz Transition without Metamagnetism in CeIrIn5

    NASA Astrophysics Data System (ADS)

    Aoki, D.; Seyfarth, G.; Pourret, A.; Gourgout, A.; McCollam, A.; Bruin, J. A. N.; Krupko, Y.; Sheikin, I.

    2016-01-01

    We report high magnetic field measurements of magnetic torque, thermoelectric power, magnetization, and the de Haas-van Alphen effect in CeIrIn5 across 28 T, where a metamagnetic transition was suggested in previous studies. The thermoelectric power displays two maxima at 28 and 32 T. Above 28 T, a new, low de Haas-van Alphen frequency with a strongly enhanced effective mass emerges, while the highest frequency observed at low field disappears entirely. This suggests a field-induced Lifshitz transition. However, longitudinal magnetization does not show any anomaly up to 33 T, thus ruling out a metamagnetic transition at 28 T.

  13. Analysis and design of nonlocal spin devices with electric-field-induced spin-transport acceleration

    SciTech Connect

    Takamura, Yota; Akushichi, Taiju; Shuto, Yusuke; Sugahara, Satoshi

    2015-05-07

    We apply electric-field-induced acceleration for spin transport to a four-terminal nonlocal device and theoretically analyze its Hanle-effect signals. The effect of the ferromagnetic contact widths of the spin injector and detector on the signals is carefully discussed. Although Hanle-effect signals are randomized owing to the effect of the contact widths, this can be excluded by selecting an appropriate electric field for acceleration of spin transport. Spin lifetime can be correctly extracted by nonlocal devices with electric-field acceleration even using the spin injector and detector with finite contact widths.

  14. Dipolar field-induced spin-wave waveguides for spin-torque magnonics

    SciTech Connect

    Demidov, V. E.; Urazhdin, S.; Zholud, A.; Sadovnikov, A. V.; Demokritov, S. O.

    2015-01-12

    We use high-resolution imaging to study the propagation of spin waves in magnonic waveguides created by the dipolar magnetic fields of microscopic patterns. We show that the characteristics of spin-wave modes in such waveguides depend strongly on their geometry. In particular, by tuning the geometrical parameters, field-induced confinement for both the edge and the center waveguide modes can be achieved, enabling control over the spin-wave transmission characteristics. The studied waveguiding structures are particularly promising for the implementation of magnonic devices utilizing spin-torque phenomena.

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

    PubMed

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

    2014-04-11

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

  16. Emission Lines and the High Energy Continuum

    NASA Technical Reports Server (NTRS)

    Green, Paul

    1998-01-01

    Quasars show many striking relationships between line and continuum radiation whose origins remain a mystery. FeII, [OIII], Hbeta, and HeII emission line properties correlate with high energy continuum properties such as the relative strength of X-ray emission, and X-ray continuum slope. At the same time, the shape of the high energy continuum may vary with luminosity. An important tool for studying global properties of Quasi Stellar Objects (QSOs) is the co-addition of data for samples of QSOS. We use this to show that X-ray bright (XB) QSOs show stronger emission lines in general, but particularly from the narrow line region. The difference in the [OIII]/Hbeta ratio is particularly striking, and even more so when blended FeII emission is properly subtracted. Weaker narrow forbidden lines ([OII] and NeV) are enhanced by factors of 2 to 3 in both UV and optical XB composite spectra. The physical origin of these diverse and interrelated correlations has yet to be determined. Unfortunately, many physically informative trends intrinsic to QSOs may be masked by dispersion in the data due to either low signal-to-noise or variability. An important tool for studying global properties of QSOs is the co-addition of data for samples of QSOS. We use this to show that X-ray bright (XB) QSOs show stronger emission lines in general, but particularly from the narrow line region. The difference in the [OIII]/Hbeta ratio is particularly striking, and even more so when blended Fell emission is properly subtracted. Weaker narrow forbidden lines ([OII] and NeV) are enhanced by factors of 2 to 3 in both UV and optical XB composite spectra. We describe a large-scale effort now underway to probe these effects in large samples, using both data and analysis as homogeneous as possible. Using an HST FOS Atlas of QSO spectra, with primary comparison to ROSAT PSPC spectral constraints, we will model the Big Blue Bump, its relationship to luminosity and QSO type, and we will analyze and

  17. Continuum emission in the 1980 July 1 solar flare

    NASA Technical Reports Server (NTRS)

    Zirin, H.; Neidig, D. F.

    1981-01-01

    Comparison of continuum measurements of the July 1, 1980 flare at Big Bear Solar Observatory and Sacramento Peak Observatory show strong blue emission kernels with the ratio of Balmer continuum (Bac):3862 A continuum:continuum above 4275 A to be about 10:5:1. The blue continuum at 3862 A is too strong to be explained by unresolved lines. The Bac intensity was 2.5 times the photosphere and the strongest 3826 A continuum was 2 times the photosphere. The brightest continuum kernel occurred late in the flare, after the hard X-ray peak and related in time to an isolated peak in the 2.2 MeV line, suggesting that that continuum was excited by protons above 20 MeV.

  18. Continuum Damping of Free-boundary TAE with AEGIS

    NASA Astrophysics Data System (ADS)

    Chen, Eugene; Berk, Herb; Breizman, Boris; Zheng, Linjin

    2010-11-01

    An extension has been added to the ideal MHD code AEGIS (Adaptive EiGenfunction Independent Solutions) to estimate continuum damping of an Alfvenic mode. In our scheme we analyze the determinant arising from attempting to match solutions at the surface of the plasma vacuum interface. A zero of the determinant corresponds to an eigenvalue of the system. When continuum damping exists in a stable system, the eigenmode cannot be calculated by an integration along the real axis (in principle integration in deformed regions of the complex plane is required). The approach we take here is to scan the value of the determinant as a function of complex frequency where the imaginary part of the frequency is positive. The analytic continuation of the determinant gives an estimate of the root in the lower half plane, from which the damping rate is extracted. A complicating factor in our procedure is that the positions of a pole and zero of a determinant is frequently comparable to the damping rate. Hence, the search procedure must account for both the zero and pole structure of the determinant. It is interesting to note that the root of the pole corresponds to the eigenvalue of the problem where an ideal conducting wall is placed on the plasma vacuum interface. We are attempting to apply our new subroutine to realistic equilibria, such as C-Mod.

  19. Capillary effects in drainage in heterogeneous porous media: Continuum modeling, experiments and pore network simulations

    SciTech Connect

    Xu, Baomin; Yortsos, Y.C.

    1993-04-01

    We investigate effects of capillary heterogeneity induced by variations in permeability in the direction of displacement in heterogeneous porous media under drainage conditions. The investigation is three-pronged and uses macroscopic simulation, based on the standard continuum equations, experiments with the use of an acoustic technique and pore network numerical models. It is found that heterogeneity affects significantly the saturation profiles, the effect being stronger at lower rates. A good agreement is found between the continuum model predictions and the experimental results based on which it can be concluded that capillary heterogeneity effects in the direction of displacement act much like a body force (e.g. gravity). A qualitative agreement is also found between the continuum approach and the pore network numerical models, which is expected to improve when finite size effects in the pore network simulations diminish. The results are interpreted with the use of invasion percolation concepts.

  20. Variability of Lyman-alpha and the ultraviolet continuum of 3C 446

    NASA Technical Reports Server (NTRS)

    Bregman, J. N.; Glassgold, A. E.; Huggins, P. J.; Kinney, A. L.

    1986-01-01

    IUE observations have been conducted over the 1230-3175 A range for the violently variable quasar 3C 446, beginning in June 1980, at intervals of 1.2, 2.2, 0.5, and 0.4 yr. Strong absorption of the continuum was found below 1830 A, probably corresponding to a Lyman edge at z of 1.00 + or - 0.01. The absence of Mg II 2798 A absorption implies that the column density is in the lower end of the range, unless the gas is metal-poor. The Lyman-alpha emission line was detected in five spectra; relative to the number of ionizing protons, the line strengths are the same as in normal quasars, and line equivalent widths are small due to the continuum's rise redward of 912 A, which is much steeper than in normal quasars. The Lyman-alpha line and the nearby continuum vary so as to maintain constant equivalent width.

  1. Probing of field-induced structures and their dynamics in ferrofluids using oscillatory rheology.

    PubMed

    Felicia, Leona J; Philip, John

    2014-10-21

    We probe field-induced structures and their dynamics in ferrofluids using oscillatory rheology. The magnetic field dependence of the relaxation time and crossover modulus showed two distinct regions, indicating the different microstructures in those regions. The observed relaxation at various magnetic field strengths indicates that side chains are attached to the pinned single-sphere-width chains between the rheometer plates. Our results suggest that the ferrofluid under a magnetic field exhibits a soft solidlike behavior whose relaxation is governed by the imposed strain rate and the magnetic field. Using the scaling factors obtained from the frequency and modulus at the crossover point in the oscillatory rheological measurements, the constant strain-rate frequency sweep data is superimposed onto a single master curve. The frequency scaling factor increases with the strain rate as a power law with an exponent close to unity, whereas the amplitude scaling factor is almost strain-rate-independent at high magnetic field strengths. These findings are useful for a better understanding of field-induced ordering of nanoparticles in fluids and their optimization for practical applications. PMID:25268053

  2. Fabrication of Crystals and Devices for Studies of Field Induced Superconductivity

    NASA Astrophysics Data System (ADS)

    Kloc, Christian

    2002-03-01

    It was demonstrated that injection of electrons or holes into materials using field effect transistor can transform the surface layer into a metal or at low enough temperatures even into a superconductor. Which substances could exhibit electric field induced superconductivity is currently not well know. Superconductivity has been successfully induced in single crystals of arenes, (pentacene Tc = 2 K, tetracene Tc = 2.7K, anthracene Tc = 4 K) oligophenylenevinylenes (trimer Tc =4.2K , tetramer Tc=2.9 K and pentamer, Tc= 2 K) sexithiophene, polymer thin film (regioregular polythiophene, Tc = 2.35 K) and single crystals of pure and intercalated fullerenes (hole and electron doped C60 Tc = 52 and 11K, C70, Tc = 7K and substituted C60, Tc = up to 117 K). Additional, Schon et al. have reported the observation of field induced superconductivity in copper oxide compounds. Despite of relative simple device structures, they consist of semiconducting single crystals or well oriented thin films, metal source and drain electrodes, an aluminum oxide dielectric layer and a conducting gate electrode, the fabrication is onerous and the significance of particular technological steps to functionality of a whole device is not well explored. In this presentation I would like to discuss these technological procedures leading to superconducting devices and further developments in search for high temperature superconducting organics.

  3. Spin-dependent masses and field-induced quantum critical points

    NASA Astrophysics Data System (ADS)

    McCollam, A.; Daou, R.; Julian, S. R.; Bergemann, C.; Flouquet, J.; Aoki, D.

    2005-04-01

    We discuss spin-dependent mass enhancements associated with field-induced quantum critical points in heavy-fermion systems. We have recently observed this phenomenon on a branch of the Fermi surface of CeRu2Si2 above its metamagnetic transition, complementing earlier work. In CeCoIn5, at high fields above a field-induced quantum critical point, we see a strong spin-dependence of the effective mass on the thermodynamically dominant sheets of the Fermi surface. These observations reinforce the suggestion that ‘missing mass’ in some cerium-based heavy-fermion systems will be found on heavy spin-polarised branches of the Fermi surface. In all cases where this phenomenon is observed the linear coefficient of specific heat is field dependent; however, CeCoIn5 seems to be the first such heavy-fermion system in which the f-electrons are definitely contributing to the Fermi volume, which puts it beyond the existing theory intended for metamagnetic systems.

  4. Field-induced phase transitions in an antiferroelectric liquid crystal using the pyroelectric effect

    PubMed

    Shtykov; Vij; Lewis; Hird; Goodby

    2000-08-01

    The antiferroelectric liquid crystal (AFLC) under investigation possesses different helical polar phases. Measurements of pyroelectric response of these phases as a function of temperature and bias field have elucidated the ability of this method for investigating the nature of antiferroelectric phases and phase transitions under the bias field. The pyroelectric signal as a function of the bias field at fixed temperatures and as a function of temperature for fixed bias fields was measured for different phases of the investigated AFLC material. A theoretical model describing the pyroelectric response in different phases of AFLC is given, and the experimental results are interpreted. The threshold fields for field induced phase transitions are determined. The type of field induced phase transition from the AF phase in particular is found to be dependent on the temperature within its range. The properties of an unusual ferrielectric phase existing between ferrielectric chiral smectic-C (SmC*) and antiferroelectric AF phases are studied in a great detail. The results confirm that this phase is one of the incommensurate phases, predicted by the axial next-nearest neighbor Ising model and Landau model for this temperature region. PMID:11088695

  5. Spectral and polarization structure of field-induced photonic bands in cholesteric liquid crystals

    NASA Astrophysics Data System (ADS)

    Palto, S. P.; Barnik, M. I.; Geivandov, A. R.; Kasyanova, I. V.; Palto, V. S.

    2015-09-01

    Transmission of planar layers of cholesteric liquid crystals is studied in pulsed electric fields perpendicular to the helix axis at normal incidence of both linearly polarized and unpolarized light. Spectral and light polarization properties of the primary photonic band and the field-induced bands up to fourth order of Bragg selective reflection are studied in detail. In our experiments we have achieved an electric field strength several times higher than the theoretical values corresponding to the critical field of full helix unwinding. However, the experiments show that despite the high strength of the electric field applied the helix does not unwind, but strongly deforms, keeping its initial spatial period. Strong helix deformation results in distinct spectral band splitting, as well as very high field-induced selective reflectance that can be applied in lasers and other optoelectronic devices. Peculiarities of inducing and splitting the bands are discussed in terms of the scattering coefficient approach. All observed effects are confirmed by numerical simulations. The simulations also show that liquid crystal surface anchoring is not the factor that prevents the helix unwinding. Thus, the currently acknowledged concept of continuous helix unwinding in the electric field should be reconsidered.

  6. Spontaneous and field-induced magnetic transitions in YBaCo2O5.5

    SciTech Connect

    Bobrovskii, Vladimir; Kazantsev, Vadim; Mirmelstein, Aleksey; Mushnikov, Nikolai; Proskurnina, Natalia; Voronin, Vladimir; Pomjakushina, Ekaterina; Conder, Kazimierz; Podlesnyak, Andrey A

    2009-01-01

    A detailed study of magnetic properties of cobaltite YBaCo{sub 2}O{sub 5.5} has been performed in high (up to 35 T) magnetic fields and under hydrostatic pressure up to 0.8 GPa. The temperatures of paramagnet-ferromagnet (PM-FM) and ferromagnet-antiferromagnet (FM-AF) phase transitions and their pressure derivatives have been determined. It has been revealed that in the compound with yttrium, in contrast to those with magnetic rare earth atoms, the AF-FM field-induced magnetic phase transition is accompanied by a considerable field hysteresis below 240 K, and the magnetic field of 35 T is not sufficient to complete this transition at low temperatures. The hysteresis value depends on the magnetic field sweep rate, which considered as an evidence of magnetic viscosity that is especially strong in the region of coexistence of the FM and AF phases. High values of susceptibility for the field-induced FM phase show that Co spin state in these compounds changes in strong magnetic field.

  7. Magnetic-field-induced orientational order in the isotropic phase of hard colloidal platelets

    SciTech Connect

    Beek, D. van der; Petukhov, A.V.; Vroege, G.J.; Lekkerkerker, H.N.W.; Davidson, P.; Ferre, J.; Jamet, J.P.; Wensink, H.H.; Bras, W.

    2006-04-15

    The magnetic-field-induced orientational order in the isotropic phase of colloidal gibbsite [Al(OH){sub 3}] platelets is studied by means of optical birefringence and small-angle x-ray scattering (SAXS) techniques. The suspensions display field-induced ordering at moderate field strengths (a few Tesla), which increases with increasing particle concentration. The gibbsite particles align their normals perpendicular to the magnetic field and hence possess a negative anisotropy of their diamagnetic susceptibility {delta}{chi}. The results can be described following a simple, Onsager-like approach. A simplified model is derived that allows one to obtain the orientational distribution function directly from the scattering data. However, it leads to an underestimate of the diamagnetic susceptibility anisotropy {delta}{chi}. This accounts for the difference between the {delta}{chi} values provided by the two experimental techniques (SAXS and magneto-optics). The order of magnitude {delta}{chi}{approx}10{sup -22} J/T{sup 2} lies in between that of goethite suspensions and that of suspensions of organic particles.

  8. Decomposition of field-induced transmembrane potential responses of single cardiac cells.

    PubMed

    Sharma, Vinod; Lu, Steven N; Tung, Leslie

    2002-09-01

    In this study, we used a multi-site optical mapping system to record field-induced responses of single cells isolated from guinea pig hearts. The cells were stained with voltage sensitive dye di-8-ANEPPS and stimulated with two uniform field (S1-S2) pulses along their longitudinal axes. The first pulse (S1 = 5 ms, <10 V/cm) was applied during rest and elicited an action potential. The second pulse (S2 = 10 ms, 4-50 V/cm) was applied 15 ms after the break of the S1 pulse (during the action potential plateau). The transmembrane potential responses, Vm(F)s, were optically recorded from up to 12 sites along the cell length using a fiber optic based optical mapping system at a resolution of 17 or 25 microm. The field-induced Vm(F)s had a complex spatio-temporal pattern. We show that these responses can be decomposed into simpler components. The first component, termed the differential-mode component (Vmd(F)), is like the response of a passive cell. The second component, termed the common-mode component (Vmc(F)), is identical all along the cell and adds a constant offset to the differential mode response of various sites along the cell length, to produce the total Vm(F) responses of the cell. PMID:12214875

  9. SYSTEMATIC CONTINUUM ERRORS IN THE Ly{alpha} FOREST AND THE MEASURED TEMPERATURE-DENSITY RELATION

    SciTech Connect

    Lee, Khee-Gan

    2012-07-10

    Continuum fitting uncertainties are a major source of error in estimates of the temperature-density relation (usually parameterized as a power-law, T {proportional_to} {Delta}{sup {gamma}-1}) of the intergalactic medium through the flux probability distribution function (PDF) of the Ly{alpha} forest. Using a simple order-of-magnitude calculation, we show that few percent-level systematic errors in the placement of the quasar continuum due to, e.g., a uniform low-absorption Gunn-Peterson component could lead to errors in {gamma} of the order of unity. This is quantified further using a simple semi-analytic model of the Ly{alpha} forest flux PDF. We find that under(over)estimates in the continuum level can lead to a lower (higher) measured value of {gamma}. By fitting models to mock data realizations generated with current observational errors, we find that continuum errors can cause a systematic bias in the estimated temperature-density relation of ({delta}({gamma})) Almost-Equal-To -0.1, while the error is increased to {sigma}{sub {gamma}} Almost-Equal-To 0.2 compared to {sigma}{sub {gamma}} Almost-Equal-To 0.1 in the absence of continuum errors.

  10. Optimizing commensality of radio continuum and spectral line observations in the era of the SKA

    NASA Astrophysics Data System (ADS)

    Maddox, Natasha; Jarvis, M. J.; Oosterloo, T. A.

    2016-08-01

    The substantial decrease in star formation density from z=1 to the present day is curious given the relatively constant neutral gas density over the same epoch. Future radio astronomy facilities, including the SKA and pathfinder telescopes, will provide pioneering measures of both the gas content of galaxies and star formation activity over cosmological timescales. Here we investigate the commensalities between neutral atomic gas (HI) and radio continuum observations, as well as the complementarity of the data products. We start with the proposed HI and continuum surveys to be undertaken with the SKA precursor telescope MeerKAT, and building on this, explore optimal combinations of survey area coverage and depth of proposed HI and continuum surveys to be undertaken with the SKA1-MID instrument. Intelligent adjustment of these observational parameters results in a tiered strategy that minimises observation time while maximising the value of the dataset, both for HI and continuum science goals. We also find great complementarity between the HI and continuum datasets, with the spectral line HI data providing redshift measurements for gas-rich, star-forming galaxies with stellar masses Mstellar~10^9 Msun to z~0.3, a factor of three lower in stellar mass than would be feasible to reach with large optical spectroscopic campaigns.

  11. Optimizing commensality of radio continuum and spectral line observations in the era of the SKA

    NASA Astrophysics Data System (ADS)

    Maddox, Natasha; Jarvis, M. J.; Oosterloo, T. A.

    2016-08-01

    The substantial decrease in star formation density from z = 1 to the present day is curious given the relatively constant neutral gas density over the same epoch. Future radio astronomy facilities, including the Square Kilometre Array (SKA) and pathfinder telescopes, will provide pioneering measures of both the gas content of galaxies and star formation activity over cosmological time-scales. Here we investigate the commensalities between neutral atomic gas (H I) and radio continuum observations, as well as the complementarity of the data products. We start with the proposed H I and continuum surveys to be undertaken with the SKA precursor telescope MeerKAT, and building on this, explore optimal combinations of survey area coverage and depth of proposed H I and continuum surveys to be undertaken with the SKA1-MID instrument. Intelligent adjustment of these observational parameters results in a tiered strategy that minimizes observation time while maximizing the value of the data set, both for H I and continuum science goals. We also find great complementarity between the H I and continuum data sets, with the spectral line H I data providing redshift measurements for gas-rich, star-forming galaxies with stellar masses M* ˜ 109 M⊙ to z ˜ 0.3, a factor of 3 lower in stellar mass than would be feasible to reach with large optical spectroscopic campaigns.

  12. FAR-ULTRAVIOLET CONTINUUM EMISSION: APPLYING THIS DIAGNOSTIC TO THE CHROMOSPHERES OF SOLAR-MASS STARS

    SciTech Connect

    Linsky, Jeffrey L.; Bushinsky, Rachel; Ayres, Tom; France, Kevin; Fontenla, Juan

    2012-01-20

    The far-ultraviolet (FUV) continuum flux is recognized as a very sensitive diagnostic of the temperature structure of the Sun's lower chromosphere. Until now analysis of the available stellar FUV data has shown that solar-type stars must also have chromospheres, but quantitative analyses of stellar FUV continua require far higher quality spectra and comparison with new non-LTE chromosphere models. We present accurate far-ultraviolet (FUV, 1150-1500 A) continuum flux measurements for solar-mass stars, made feasible by the high throughput and very low detector background of the Cosmic Origins Spectrograph on the Hubbble Space Telescope. We show that the continuum flux can be measured above the detector background even for the faintest star in our sample. We find a clear trend of increasing continuum brightness temperature at all FUV wavelengths with decreasing rotational period, which provides an important measure of magnetic heating rates in stellar chromospheres. Comparison with semiempirical solar flux models shows that the most rapidly rotating solar-mass stars have FUV continuum brightness temperatures similar to the brightest faculae seen on the Sun. The thermal structure of the brightest solar faculae therefore provides a first-order estimate of the thermal structure and heating rate for the most rapidly rotating solar-mass stars in our sample.

  13. A continuum model of transcriptional bursting

    PubMed Central

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

    2016-01-01

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

  14. Mesoscopic and continuum modelling of angiogenesis.

    PubMed

    Spill, F; Guerrero, P; Alarcon, T; Maini, P K; Byrne, H M

    2015-02-01

    Angiogenesis is the formation of new blood vessels from pre-existing ones in response to chemical signals secreted by, for example, a wound or a tumour. In this paper, we propose a mesoscopic lattice-based model of angiogenesis, in which processes that include proliferation and cell movement are considered as stochastic events. By studying the dependence of the model on the lattice spacing and the number of cells involved, we are able to derive the deterministic continuum limit of our equations and compare it to similar existing models of angiogenesis. We further identify conditions under which the use of continuum models is justified, and others for which stochastic or discrete effects dominate. We also compare different stochastic models for the movement of endothelial tip cells which have the same macroscopic, deterministic behaviour, but lead to markedly different behaviour in terms of production of new vessel cells. PMID:24615007

  15. Models of Uranium continuum radio emission

    NASA Technical Reports Server (NTRS)

    Romig, Joseph H.; Evans, David R.; Sawyer, Constance B.; Schweitzer, Andrea E.; Warwick, James W.

    1987-01-01

    Uranium continuum radio emission detected by the Voyager 2 Planetary Radio Astronomy experiment during the January 1986 encounter is considered. The continuum emissions comprised four components (equatorial emissions, anomaly emissions, strong nightside emissions, and weak nightside emissions) associated with different sources. The equatorial emissions appeared most prominently during the days before closest approach and extended from 40 kHz or below to about 120 kHz. The anomaly emissions were seen about 12 hours before closest approach and extended to about 250 kHz. The agreement found between Miranda's phase and strong radio emission at 20.4 kHz, just after closest approach, suggests intense dynamic activity on the Miranda L shell.

  16. Continuum of Collaboration: Little Steps for Little Feet

    ERIC Educational Resources Information Center

    Powell, Gwynn M.

    2013-01-01

    This mini-article outlines a continuum of collaboration for faculty within a department of the same discipline. The goal of illustrating this continuum is showcase different stages of collaboration so that faculty members can assess where they are as a collective and consider steps to collaborate more. The separate points along a continuum of…

  17. Spatiotemporal dynamics of continuum neural fields

    NASA Astrophysics Data System (ADS)

    Bressloff, Paul C.

    2012-01-01

    We survey recent analytical approaches to studying the spatiotemporal dynamics of continuum neural fields. Neural fields model the large-scale dynamics of spatially structured biological neural networks in terms of nonlinear integrodifferential equations whose associated integral kernels represent the spatial distribution of neuronal synaptic connections. They provide an important example of spatially extended excitable systems with nonlocal interactions and exhibit a wide range of spatially coherent dynamics including traveling waves oscillations and Turing-like patterns.

  18. The emission line - continuum connection in galaxies

    NASA Astrophysics Data System (ADS)

    Sodre, Laerte; Albernaz-Sirico, Ana Carolina

    2015-08-01

    Star-forming galaxies with a blue continuum tend to present prominent emission lines, whereas in red galaxies emission lines are associated mostly to nuclear activity or to certain stellar populations, like post-AGB stars. In this work we have used tools of machine learning to investigate how theemission line equivalent widths of galaxies are related to their optical continuum. From the analysis of a sample of high S/N spectra of SDSS/DR9 we show that indeed it is possible to estimate with good accuracy the equivalent width of the most intense emission lines from galaxy continuum information only for star-forming galaxies and AGNs (LINERS and Seyfer 2 emitters) by using simple relationships (linear and/or polynomial models) between the EWs and the relative flux at certain wavelengths. An important motivation for this work is to produce realistic spectra to test the data reduction pipelines of the new generation of galaxy surveys, like J-PAS and PFS/SuMIRe.

  19. Lattice Boltzmann algorithm for continuum multicomponent flow.

    PubMed

    Halliday, I; Hollis, A P; Care, C M

    2007-08-01

    We present a multicomponent lattice Boltzmann simulation for continuum fluid mechanics, paying particular attention to the component segregation part of the underlying algorithm. In the principal result of this paper, the dynamics of a component index, or phase field, is obtained for a segregation method after U. D'Ortona [Phys. Rev. E 51, 3718 (1995)], due to Latva-Kokko and Rothman [Phys. Rev. E 71 056702 (2005)]. The said dynamics accord with a simulation designed to address multicomponent flow in the continuum approximation and underwrite improved simulation performance in two main ways: (i) by reducing the interfacial microcurrent activity considerably and (ii) by facilitating simulational access to regimes of flow with a low capillary number and drop Reynolds number [I. Halliday, R. Law, C. M. Care, and A. Hollis, Phys. Rev. E 73, 056708 (2006)]. The component segregation method studied, used in conjunction with Lishchuk's method [S. V. Lishchuk, C. M. Care, and I. Halliday, Phys. Rev. E 67, 036701 (2003)], produces an interface, which is distributed in terms of its component index; however, the hydrodynamic boundary conditions which emerge are shown to support the notion of a sharp, unstructured, continuum interface. PMID:17930175

  20. A Continuum Theory of Thermal Transpiration

    NASA Astrophysics Data System (ADS)

    Bielenberg, James; Brenner, Howard

    2003-11-01

    A rational, continuum mechanical description is given for the pressure drop that develops in a closed capillary tube subject to an imposed temperature gradient. This phenomenon, termed thermal transpiration, has been experimentally demonstrated in systems at vanishing Knudsen numbers, yet no purely continuum mechanical description has, until now, been given. Previous hybrid solutions (dating back to Maxwell in 1879) have utilized the classical, incompressible flow equations along with molecularly derived slip boundary conditions. This solution approach will be briefly discussed and shown to be dynamically consistent yet energetically flawed. Subsequently, we will apply a novel reformulation of continuum-mechanics and -thermodynamics, which clearly distinguishes between the Lagrangian (tracer) and the barycentric velocities, to generate a solution for the thermal pressure drop developed in a closed system. Explicitly, the phenomena at hand will be shown to be entirely analogous to Poiseuille flow in tube, albeit with the tacit recognition that the ``flow'' we are speaking of is defined in a dynamic sense rather than in the more traditional, kinematic mass-flux based sense. This solution will be show to be free of ad hoc parameters, consistent with experimental results, and in accordance with classical macroscopic thermodynamics. Beyond its purely scientific importance, this phenomenon may find applications in the emerging area of micro-fluidic pumping.

  1. Bipotential continuum models for granular mechanics

    NASA Astrophysics Data System (ADS)

    Goddard, Joe

    2014-03-01

    Most currently popular continuum models for granular media are special cases of a generalized Maxwell fluid model, which describes the evolution of stress and internal variables such as granular particle fraction and fabric,in terms of imposed strain rate. It is shown how such models can be obtained from two scalar potentials, a standard elastic free energy and a ``dissipation potential'' given rigorously by the mathematical theory of Edelen. This allows for a relatively easy derivation of properly invariant continuum models for granular media and fluid-particle suspensions within a thermodynamically consistent framework. The resulting continuum models encompass all the prominent regimes of granular flow, ranging from the quasi-static to rapidly sheared, and are readily extended to include higher-gradient or Cosserat effects. Models involving stress diffusion, such as that proposed recently by Kamrin and Koval (PRL 108 178301), provide an alternative approach that is mentioned in passing. This paper provides a brief overview of a forthcoming review articles by the speaker (The Princeton Companion to Applied Mathematics, and Appl. Mech. Rev.,in the press, 2013).

  2. Polymer Fluid Dynamics: Continuum and Molecular Approaches.

    PubMed

    Bird, R B; Giacomin, A J

    2016-06-01

    To solve problems in polymer fluid dynamics, one needs the equations of continuity, motion, and energy. The last two equations contain the stress tensor and the heat-flux vector for the material. There are two ways to formulate the stress tensor: (a) One can write a continuum expression for the stress tensor in terms of kinematic tensors, or (b) one can select a molecular model that represents the polymer molecule and then develop an expression for the stress tensor from kinetic theory. The advantage of the kinetic theory approach is that one gets information about the relation between the molecular structure of the polymers and the rheological properties. We restrict the discussion primarily to the simplest stress tensor expressions or constitutive equations containing from two to four adjustable parameters, although we do indicate how these formulations may be extended to give more complicated expressions. We also explore how these simplest expressions are recovered as special cases of a more general framework, the Oldroyd 8-constant model. Studying the simplest models allows us to discover which types of empiricisms or molecular models seem to be worth investigating further. We also explore equivalences between continuum and molecular approaches. We restrict the discussion to several types of simple flows, such as shearing flows and extensional flows, which are of greatest importance in industrial operations. Furthermore, if these simple flows cannot be well described by continuum or molecular models, then it is not necessary to lavish time and energy to apply them to more complex flow problems. PMID:27276553

  3. Improvements in continuum modeling for biomolecular systems

    NASA Astrophysics Data System (ADS)

    Yu, Qiao; Ben-Zhuo, Lu

    2016-01-01

    Modeling of biomolecular systems plays an essential role in understanding biological processes, such as ionic flow across channels, protein modification or interaction, and cell signaling. The continuum model described by the Poisson- Boltzmann (PB)/Poisson-Nernst-Planck (PNP) equations has made great contributions towards simulation of these processes. However, the model has shortcomings in its commonly used form and cannot capture (or cannot accurately capture) some important physical properties of the biological systems. Considerable efforts have been made to improve the continuum model to account for discrete particle interactions and to make progress in numerical methods to provide accurate and efficient simulations. This review will summarize recent main improvements in continuum modeling for biomolecular systems, with focus on the size-modified models, the coupling of the classical density functional theory and the PNP equations, the coupling of polar and nonpolar interactions, and numerical progress. Project supported by the National Natural Science Foundation of China (Grant No. 91230106) and the Chinese Academy of Sciences Program for Cross & Cooperative Team of the Science & Technology Innovation.

  4. Electronic continuum model for molecular dynamics simulations.

    PubMed

    Leontyev, I V; Stuchebrukhov, A A

    2009-02-28

    A simple model for accounting for electronic polarization in molecular dynamics (MD) simulations is discussed. In this model, called molecular dynamics electronic continuum (MDEC), the electronic polarization is treated explicitly in terms of the electronic continuum (EC) approximation, while the nuclear dynamics is described with a fixed-charge force field. In such a force-field all atomic charges are scaled to reflect the screening effect by the electronic continuum. The MDEC model is rather similar but not equivalent to the standard nonpolarizable force-fields; the differences are discussed. Of our particular interest is the calculation of the electrostatic part of solvation energy using standard nonpolarizable MD simulations. In a low-dielectric environment, such as protein, the standard MD approach produces qualitatively wrong results. The difficulty is in mistreatment of the electronic polarizability. We show how the results can be much improved using the MDEC approach. We also show how the dielectric constant of the medium obtained in a MD simulation with nonpolarizable force-field is related to the static (total) dielectric constant, which includes both the nuclear and electronic relaxation effects. Using the MDEC model, we discuss recent calculations of dielectric constants of alcohols and alkanes, and show that the MDEC results are comparable with those obtained with the polarizable Drude oscillator model. The applicability of the method to calculations of dielectric properties of proteins is discussed. PMID:19256627

  5. Field-Induced Crystalline-to-Amorphous Phase Transformation on the Si Nano-Apex and the Achieving of Highly Reliable Si Nano-Cathodes.

    PubMed

    Huang, Yifeng; Deng, Zexiang; Wang, Weiliang; Liang, Chaolun; She, Juncong; Deng, Shaozhi; Xu, Ningsheng

    2015-01-01

    Nano-scale vacuum channel transistors possess merits of higher cutoff frequency and greater gain power as compared with the conventional solid-state transistors. The improvement in cathode reliability is one of the major challenges to obtain high performance vacuum channel transistors. We report the experimental findings and the physical insight into the field induced crystalline-to-amorphous phase transformation on the surface of the Si nano-cathode. The crystalline Si tip apex deformed to amorphous structure at a low macroscopic field (0.6~1.65 V/nm) with an ultra-low emission current (1~10 pA). First-principle calculation suggests that the strong electrostatic force exerting on the electrons in the surface lattices would take the account for the field-induced atomic migration that result in an amorphization. The arsenic-dopant in the Si surface lattice would increase the inner stress as well as the electron density, leading to a lower amorphization field. Highly reliable Si nano-cathodes were obtained by employing diamond like carbon coating to enhance the electron emission and thus decrease the surface charge accumulation. The findings are crucial for developing highly reliable Si-based nano-scale vacuum channel transistors and have the significance for future Si nano-electronic devices with narrow separation. PMID:25994377

  6. Field-Induced Crystalline-to-Amorphous Phase Transformation on the Si Nano-Apex and the Achieving of Highly Reliable Si Nano-Cathodes

    NASA Astrophysics Data System (ADS)

    Huang, Yifeng; Deng, Zexiang; Wang, Weiliang; Liang, Chaolun; She, Juncong; Deng, Shaozhi; Xu, Ningsheng

    2015-05-01

    Nano-scale vacuum channel transistors possess merits of higher cutoff frequency and greater gain power as compared with the conventional solid-state transistors. The improvement in cathode reliability is one of the major challenges to obtain high performance vacuum channel transistors. We report the experimental findings and the physical insight into the field induced crystalline-to-amorphous phase transformation on the surface of the Si nano-cathode. The crystalline Si tip apex deformed to amorphous structure at a low macroscopic field (0.6~1.65 V/nm) with an ultra-low emission current (1~10 pA). First-principle calculation suggests that the strong electrostatic force exerting on the electrons in the surface lattices would take the account for the field-induced atomic migration that result in an amorphization. The arsenic-dopant in the Si surface lattice would increase the inner stress as well as the electron density, leading to a lower amorphization field. Highly reliable Si nano-cathodes were obtained by employing diamond like carbon coating to enhance the electron emission and thus decrease the surface charge accumulation. The findings are crucial for developing highly reliable Si-based nano-scale vacuum channel transistors and have the significance for future Si nano-electronic devices with narrow separation.

  7. Field-Induced Crystalline-to-Amorphous Phase Transformation on the Si Nano-Apex and the Achieving of Highly Reliable Si Nano-Cathodes

    PubMed Central

    Huang, Yifeng; Deng, Zexiang; Wang, Weiliang; Liang, Chaolun; She, Juncong; Deng, Shaozhi; Xu, Ningsheng

    2015-01-01

    Nano-scale vacuum channel transistors possess merits of higher cutoff frequency and greater gain power as compared with the conventional solid-state transistors. The improvement in cathode reliability is one of the major challenges to obtain high performance vacuum channel transistors. We report the experimental findings and the physical insight into the field induced crystalline-to-amorphous phase transformation on the surface of the Si nano-cathode. The crystalline Si tip apex deformed to amorphous structure at a low macroscopic field (0.6~1.65 V/nm) with an ultra-low emission current (1~10 pA). First-principle calculation suggests that the strong electrostatic force exerting on the electrons in the surface lattices would take the account for the field-induced atomic migration that result in an amorphization. The arsenic-dopant in the Si surface lattice would increase the inner stress as well as the electron density, leading to a lower amorphization field. Highly reliable Si nano-cathodes were obtained by employing diamond like carbon coating to enhance the electron emission and thus decrease the surface charge accumulation. The findings are crucial for developing highly reliable Si-based nano-scale vacuum channel transistors and have the significance for future Si nano-electronic devices with narrow separation. PMID:25994377

  8. T-wave sources, slopes, rough bottoms and continuum

    NASA Astrophysics Data System (ADS)

    Odom, Robert I.; Soukup, Darin J.

    2002-05-01

    Bathymetry plays a strong role in the excitation of T-waves by breaking strict mode orthogonality and permitting energy from higher order modes to couple to the lower order modes comprising the T-phase. Observationally (Dziak, 2001) earthquakes with a strong strike-slip component are more efficient at generating T-waves than normal fault mechanisms with the same moment magnitude. It is shown that fault type and orientation correlates strongly with T-wave excitation efficiency. For shallow sources, the discrete modes contribute to the majority of the seismic source field, which is then scattered into the acoustic modes by irregular bathymetry. However, the deeper the earthquake source, the more important the continuum component of the spectrum becomes for the excitation. Deterministic bathymetry and random roughness enter the modal scattering theory as separate terms, and allow the relative contributions from the slope conversion mechanism and bottom roughness to be directly compared. [Work supported by the National Ocean Partnership Program.

  9. QCD thermodynamics with continuum extrapolated Wilson fermions. II.

    NASA Astrophysics Data System (ADS)

    Borsanyi, Szabolcs; Hoelbling, Christian; Toth, Balint C.; Durr, Stephan; Krieg, Stefan; Szabo, Kalman K.; Fodor, Zoltan; Katz, Sandor D.; Nogradi, Daniel; Trombitas, Norbert

    2015-07-01

    We continue our investigation of 2 +1 flavor QCD thermodynamics using dynamical Wilson fermions in the fixed scale approach. Two additional pion masses, approximately 440 MeV and 285 MeV, are added to our previous work at 545 MeV. The simulations were performed at 3 or 4 lattice spacings at each pion mass. The renormalized chiral condensate, strange quark number susceptibility and Polyakov loop is obtained as a function of the temperature and we observe a decrease in the light chiral pseudocritical temperature as the pion mass is lowered while the pseudocritical temperature associated with the strange quark number susceptibility or the Polyakov loop is only mildly sensitive to the pion mass. These findings are in agreement with previous continuum results obtained in the staggered formulation.

  10. A robust, coupled approach for atomistic-continuum simulation.

    SciTech Connect

    Aubry, Sylvie; Webb, Edmund Blackburn, III; Wagner, Gregory John; Klein, Patrick A.; Jones, Reese E.; Zimmerman, Jonathan A.; Bammann, Douglas J.; Hoyt, Jeffrey John; Kimmer, Christopher J.

    2004-09-01

    This report is a collection of documents written by the group members of the Engineering Sciences Research Foundation (ESRF), Laboratory Directed Research and Development (LDRD) project titled 'A Robust, Coupled Approach to Atomistic-Continuum Simulation'. Presented in this document is the development of a formulation for performing quasistatic, coupled, atomistic-continuum simulation that includes cross terms in the equilibrium equations that arise due to kinematic coupling and corrections used for the calculation of system potential energy to account for continuum elements that overlap regions containing atomic bonds, evaluations of thermo-mechanical continuum quantities calculated within atomistic simulations including measures of stress, temperature and heat flux, calculation used to determine the appropriate spatial and time averaging necessary to enable these atomistically-defined expressions to have the same physical meaning as their continuum counterparts, and a formulation to quantify a continuum 'temperature field', the first step towards constructing a coupled atomistic-continuum approach capable of finite temperature and dynamic analyses.

  11. Continuum absorption in the vicinity of the toroidicity-induced Alfvén gap

    DOE PAGESBeta

    Li, M.; Breizman, B. N.; Zheng, L. J.; Chen, Eugene Y.

    2015-12-04

    Excitation of Alfvén modes is commonly viewed as a concern for energetic particle confinement in burning plasmas. The 3.5 MeValpha particles produced by fusion may be affected as well as other fast ions in both present and future devices. Continuum damping of such modes is one of the key factors that determine their excitation thresholds and saturation levels. This work examines the resonant dissipative response of the Alfvén continuum to an oscillating driving current when the driving frequency is slightly outside the edges of the toroidicity-induced spectral gap. The problem is largely motivated by the need to describe the continuummore » absorption in the frequency sweeping events. Akey element of this problem is the negative interference of the two closely spaced continuum crossing points.Weexplain why the lower and upper edges of the gap can have very different continuum absorption features. Lastly, the difference is associated with an eigenmode whose frequency can be arbitrarily close to the upper edge of the gap whereas the lower edge of the gap is always a finite distance away from the closest eigenmode.« less

  12. Field-induced exciton condensation in LaCoO3.

    PubMed

    Sotnikov, A; Kuneš, J

    2016-01-01

    Motivated by recent observation of magnetic field induced transition in LaCoO3 we study the effect of external field in systems close to instabilities towards spin-state ordering and exciton condensation. We show that, while in both cases the transition can be induced by an external field, temperature dependencies of the critical field have opposite slopes. Based on this result we argue that the experimental observations select the exciton condensation scenario. We show that such condensation is possible due to high mobility of the intermediate spin excitations. The estimated width of the corresponding dispersion is large enough to overrule the order of atomic multiplets and to make the intermediate spin excitation propagating with a specific wave vector the lowest excitation of the system. PMID:27461512

  13. Field-induced magnetostructural transition in Gd5ge4 studied by pulsed magnetic fields

    SciTech Connect

    Ouyang, Z.W.; Nojiri, H.; Yoshii, S.; Rao, G.H.; Wang, Y.C.; Pecharsky, V.K.; Gschneidner Jr., K.A.

    2008-05-22

    The field-induced magnetostructural transformation in Gd{sub 5}Ge{sub 4} was examined by magnetization measurements in pulsed magnetic fields. The low-temperature irreversibility of the transition can be destroyed by the magnetocaloric effect, and depending on the heat exchange between the sample and its surroundings, the irreversibility (or kinetic arrest) can also be retained. Measurements by using various magnetic-field sweep rates were conducted to examine the dynamic response of the system in the transition region. The critical fields for the magnetostructural transition below 20 K are field sweep rate dependent--the larger the field sweep rate, the higher the critical field. However, this rate dependence is readily suppressed with increasing temperature.

  14. Field-induced growth of self-annealing suspended colloidal monolayers

    NASA Astrophysics Data System (ADS)

    Han, Ming; Luijten, Erik; Luijten Research Group Team

    2015-03-01

    Due to their reduced dimensionality, flexible sheet-like materials have numerous applications, e.g. offering the potential to serve as functional coatings or as a system for encapsulation, akin to biologic membranes. Here we report the ability to generate large ordered, flexible, and suspended monolayers via field-induced self-assembly. We employ anisotropic polarizable colloidal particles and stimulate their reversible aggregation by applying a static external electric field. Through molecular dynamics simulations with a self-consistent calculation of the induced dipole moments, we demonstrate that such particles form monolayers capable of eliminating defects and dislocations, and even self-healing. Potential applications, such as tube formation, are also discussed.

  15. Electric-Field-Induced Dissociation of Heavy Rydberg Ion-Pair States

    SciTech Connect

    Reinhold, Carlos O; Yoshida, S.; Dunning, F. B.

    2011-01-01

    A classical trajectory Monte Carlo approach is used to simulate the dissociation of H+..F and K+..Cl heavy Rydberg ion pairs induced by a ramped electric-field, a technique used experimentally to detect and probe ion-pair states. The simulations include the effects of the strong short-range repulsive interaction associated with ion-pair scattering and provide results in good agreement with experimental data for Stark wavepackets probed by a ramped field, demonstrating that many of the characteristics of field-induced dissociation can be well described using a purely classical model. The data also show that states with a given value of principal quantum number (i.e., binding energy) can dissociate over a broad range of applied fields, the exact field being governed by the initial orbital angular momentum and orientation of the state.

  16. Field-induced exciton condensation in LaCoO3

    PubMed Central

    Sotnikov, A.; Kuneš, J.

    2016-01-01

    Motivated by recent observation of magnetic field induced transition in LaCoO3 we study the effect of external field in systems close to instabilities towards spin-state ordering and exciton condensation. We show that, while in both cases the transition can be induced by an external field, temperature dependencies of the critical field have opposite slopes. Based on this result we argue that the experimental observations select the exciton condensation scenario. We show that such condensation is possible due to high mobility of the intermediate spin excitations. The estimated width of the corresponding dispersion is large enough to overrule the order of atomic multiplets and to make the intermediate spin excitation propagating with a specific wave vector the lowest excitation of the system. PMID:27461512

  17. Hysteretic DC electrowetting by field-induced nano-structurations on polystyrene films.

    PubMed

    Sawane, Yogesh B; Datar, Suwarna; Ogale, Satishchandra B; Banpurkar, Arun G

    2015-04-01

    Electrowetting (EW) offers executive wetting control of conductive liquids on several polymer surfaces. We report a peculiar electrowetting response for aqueous drops on a polystyrene (PS) dielectric surface in the presence of silicone oil. After the first direct current (DC) voltage cycle, the droplet failed to regain Young's angle, yielding contact angle hysteresis, which is close to a value found in ambient air. We conjecture that the hysteretic EW response appears from in situ surface modification using electric field induced water-ion contact with PS surface inducing nano-structuration by electro-hydrodynamic (EHD) instability. Atomic force microscopy confirms the formation of nano-structuration on the electrowetted surface. The effects of molecular weight, applied electric field, water conductivity and pH on nano-structuration are studied. Finally, the EW based nano-structuration on PS surface is used for the enhanced loading of aqueous dyes on hydrophobic surfaces. PMID:25690856

  18. Giant electric-field-induced strain in lead-free piezoelectric materials.

    PubMed

    Chen, Lan; Yang, Yurong; Meng, X K

    2016-01-01

    First-principles calculations are performed to investigate the structures, electrical, and magnetic properties of compressive BiFeO3 films under electric-field and pressure perpendicular to the films. A reversible electric-field-induced strain up 10% is achieved in the compressive BiFeO3 films. The giant strain originates from rhombohedral-tetragonal (R-T) phase transition under electric-filed, and is recoverable from tetragonal-rhombohedral (T-R) phase transition by compressive stress. Additionally, the weak ferromagnetism in BiFeO3 films is largely changed in R-T phase transition under electric-filed and T-R phase transition under pressure - reminiscent of magnetoelectric effect and magnetoelastic effect. These results suggest exciting device opportunities arising from the giant filed-induced strain, large magnetoelectric effect and magnetoelastic effect. PMID:27139526

  19. Dispersion of Electric-Field-Induced Faraday Effect in Magnetoelectric Cr2O3

    NASA Astrophysics Data System (ADS)

    Wang, Junlei; Binek, Christian

    2016-03-01

    The frequency dependence of the electric-field-induced magneto-optical Faraday effect is investigated in the magnetoelectric antiferromagnet chromia. Two electrically induced Faraday signals superimpose in proportion to the linear magnetoelectric susceptibility α and the antiferromagnetic order parameter η . The relative strength of these contributions is determined by the frequency of the probing light and can be tuned between extreme characteristics following the temperature dependence of α or η . The frequency dependence is analyzed in terms of electric dipole transitions of perturbed Cr3 + crystal-field states. The results allow us to measure voltage-controlled selection, isothermal switching, and temperature dependence of η in a tabletop setup. The voltage-specific Faraday rotation is independent of the sample thickness, making the method scalable and versatile down to the limit of dielectric breakdown.

  20. Giant Magnetic Field-induced Phase Transitions in Dimeric Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Salili, Seyyed Muhammad; Salamonczyk, Miroslaw; Tamba, Maria-Gabriela; Sprunt, Samuel; Mehl, Georg; Jakli, Antal; Gleeson, James; Kent Group Collaboration; Hull Group Collaboration

    Liquid crystals are responsive to external fields such as electric, magnetic fields. The first experimental observation of dependence of isotropic to nematic phase transition on the applied magnetic field was done using a strong magnetic field on bent-core nematogens and the phase transition temperature exhibited an upshift of 0.7 C at B =30 T. We report on measurements of giant magnetic field-induced isotropic-nematic transition of chainsticks (nunchuks) type dimeric liquid crystals. Upon using the B =25 T split-helix resistive solenoid magnet at NHMFL, we have observed up to 18 C upshift of the isotropic to nematic phase transition temperature at B =22T. We discuss the results within the context of differential thermodynamic potential and the two basic mean-field theories. To our knowledge, this is the first observation of such huge shifts in the phase transitions of thermotropic liquid ctystals

  1. Electric field-induced reversible trapping of microtubules along metallic glass microwire electrodes

    NASA Astrophysics Data System (ADS)

    Kim, Kyongwan; Sikora, Aurélien; Nakayama, Koji S.; Umetsu, Mitsuo; Hwang, Wonmuk; Teizer, Winfried

    2015-04-01

    Microtubules are among bio-polymers providing vital functions in dynamic cellular processes. Artificial organization of these bio-polymers is a requirement for transferring their native functions into device applications. Using electrophoresis, we achieve an accumulation of microtubules along a metallic glass (Pd42.5Cu30Ni7.5P20) microwire in solution. According to an estimate based on migration velocities of microtubules approaching the wire, the electrophoretic mobility of microtubules is around 10-12 m2/Vs. This value is four orders of magnitude smaller than the typical mobility reported previously. Fluorescence microscopy at the individual-microtubule level shows microtubules aligning along the wire axis during the electric field-induced migration. Casein-treated electrodes are effective to reversibly release trapped microtubules upon removal of the external field. An additional result is the condensation of secondary filamentous structures from oriented microtubules.

  2. Field-Induced Lifshitz Transition without Metamagnetism in CeIrIn(5).

    PubMed

    Aoki, D; Seyfarth, G; Pourret, A; Gourgout, A; McCollam, A; Bruin, J A N; Krupko, Y; Sheikin, I

    2016-01-22

    We report high magnetic field measurements of magnetic torque, thermoelectric power, magnetization, and the de Haas-van Alphen effect in CeIrIn_{5} across 28 T, where a metamagnetic transition was suggested in previous studies. The thermoelectric power displays two maxima at 28 and 32 T. Above 28 T, a new, low de Haas-van Alphen frequency with a strongly enhanced effective mass emerges, while the highest frequency observed at low field disappears entirely. This suggests a field-induced Lifshitz transition. However, longitudinal magnetization does not show any anomaly up to 33 T, thus ruling out a metamagnetic transition at 28 T. PMID:26849611

  3. Field-induced exciton condensation in LaCoO3

    NASA Astrophysics Data System (ADS)

    Sotnikov, A.; Kuneš, J.

    2016-07-01

    Motivated by recent observation of magnetic field induced transition in LaCoO3 we study the effect of external field in systems close to instabilities towards spin-state ordering and exciton condensation. We show that, while in both cases the transition can be induced by an external field, temperature dependencies of the critical field have opposite slopes. Based on this result we argue that the experimental observations select the exciton condensation scenario. We show that such condensation is possible due to high mobility of the intermediate spin excitations. The estimated width of the corresponding dispersion is large enough to overrule the order of atomic multiplets and to make the intermediate spin excitation propagating with a specific wave vector the lowest excitation of the system.

  4. Magnetic-field-induced diameter-selective synthesis of single-walled carbon nanotubes.

    PubMed

    Su, Yanjie; Zhang, Yaozhong; Wei, Hao; Zhang, Liling; Zhao, Jiang; Yang, Zhi; Zhang, Yafei

    2012-03-01

    We report a facile and scalable approach to synthesize single-walled carbon nanotubes (SWNTs) with selected diameter distribution by applying a magnetic field perpendicular to the electric field in the arc plasma region. It is found that this magnetic field-induced diameter-selectivity strategy enables the control of the SWNTs with different diameter distributions in different regions, and the diameter-selective efficiency could be enhanced by modifying the direction of magnetic field. Our results indicate that the motions of the catalysts with different particle sizes, positive carbon ions and electrons are significantly influenced by the magnetic field and electromagnetic force, resulting in the different nucleation and growth processes of SWNTs due to the collective interactions between the magnetic field and arc plasma. This approach would enable a viable route towards the synthesis of SWNTs with desired diameter through the tuning of arc parameters in the arc discharge process. PMID:22301844

  5. Picosecond Electric-Field-Induced Threshold Switching in Phase-Change Materials.

    PubMed

    Zalden, Peter; Shu, Michael J; Chen, Frank; Wu, Xiaoxi; Zhu, Yi; Wen, Haidan; Johnston, Scott; Shen, Zhi-Xun; Landreman, Patrick; Brongersma, Mark; Fong, Scott W; Wong, H-S Philip; Sher, Meng-Ju; Jost, Peter; Kaes, Matthias; Salinga, Martin; von Hoegen, Alexander; Wuttig, Matthias; Lindenberg, Aaron M

    2016-08-01

    Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag_{4}In_{3}Sb_{67}Te_{26}. Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on subpicosecond time scales-faster than crystals can nucleate. This supports purely electronic models of threshold switching and reveals potential applications as an ultrafast electronic switch. PMID:27541475

  6. Picosecond Electric-Field-Induced Threshold Switching in Phase-Change Materials

    NASA Astrophysics Data System (ADS)

    Zalden, Peter; Shu, Michael J.; Chen, Frank; Wu, Xiaoxi; Zhu, Yi; Wen, Haidan; Johnston, Scott; Shen, Zhi-Xun; Landreman, Patrick; Brongersma, Mark; Fong, Scott W.; Wong, H.-S. Philip; Sher, Meng-Ju; Jost, Peter; Kaes, Matthias; Salinga, Martin; von Hoegen, Alexander; Wuttig, Matthias; Lindenberg, Aaron M.

    2016-08-01

    Many chalcogenide glasses undergo a breakdown in electronic resistance above a critical field strength. Known as threshold switching, this mechanism enables field-induced crystallization in emerging phase-change memory. Purely electronic as well as crystal nucleation assisted models have been employed to explain the electronic breakdown. Here, picosecond electric pulses are used to excite amorphous Ag4In3Sb67Te26 . Field-dependent reversible changes in conductivity and pulse-driven crystallization are observed. The present results show that threshold switching can take place within the electric pulse on subpicosecond time scales—faster than crystals can nucleate. This supports purely electronic models of threshold switching and reveals potential applications as an ultrafast electronic switch.

  7. Magnetic-Field-Induced Insulator-Conductor Transition in SU(2) Quenched Lattice Gauge Theory

    SciTech Connect

    Buividovich, P.V.; Kharzeev, D.; Chernodub, M.N., Kalaydzhyan, T., Luschevskaya, E.V., and M.I. Polikarpov

    2010-09-24

    We study the correlator of two vector currents in quenched SU(2) lattice gauge theory with a chirally invariant lattice Dirac operator with a constant external magnetic field. It is found that in the confinement phase the correlator of the components of the current parallel to the magnetic field decays much slower than in the absence of a magnetic field, while for other components the correlation length slightly decreases. We apply the maximal entropy method to extract the corresponding spectral function. In the limit of zero frequency this spectral function yields the electric conductivity of quenched theory. We find that in the confinement phase the external magnetic field induces nonzero electric conductivity along the direction of the field, transforming the system from an insulator into an anisotropic conductor. In the deconfinement phase the conductivity does not exhibit any sizable dependence on the magnetic field.

  8. Raman thermometry: Effective temperature of the nonuniform temperature field induced by a Gaussian laser

    SciTech Connect

    Očenášek, Jan Voldřich, Josef

    2015-12-21

    Raman spectroscopy is a widely applied analytical technique with numerous applications that is based on inelastic scattering of monochromatic light, which is typically provided by a laser. Irradiation of a sample by a laser beam is always accompanied by an increase in the sample temperature, which may be unwanted or may be beneficial for studying temperature-related effects and determining thermal parameters. This work reports analyses of the temperature field induced by a Gaussian laser to calculate the Raman scattered intensity related to each temperature value of the nonuniform field present on the sample. The effective temperature of the probed field, calculated as an average weighted by the laser intensity, is demonstrated to be about 70% of the maximum temperature irrespective of the absorption coefficient or the laser focus. Finally, using crystalline silicon as a model material, it is shown that this effective value closely approximates the temperature value identified from the thermally related peak shift.

  9. Magnetic-field-induced ferroelectric polarization reversal in magnetoelectric composites revealed by piezoresponse force microscopy

    NASA Astrophysics Data System (ADS)

    Miao, Hongchen; Zhou, Xilong; Dong, Shuxiang; Luo, Haosu; Li, Faxin

    2014-07-01

    Controlling electric polarization (or magnetization) in multiferroic materials with external magnetic fields (or electric fields) is very important for fundamental physics and spintronic devices. Although there has been some progress on magnetic-field-induced polarization reversal in single-phase multiferroics, such behavior has so far never been realized in composites. Here we show that it is possible to reverse ferroelectric polarization using magnetic fields in a bilayer Terfenol-D/PMN-33%PT composite. We realized this by ferroelectric domain imaging using piezoresponse force microscopy (PFM) under applied magnetic field loading. The internal electric field caused by the magnetoelectric (ME) effect in the PMN-PT crystal is considered as the driving force for the 180° polarization switching, and its existence is verified by switching spectroscopy PFM testing under a series of external magnetic fields. A quantitative method is further suggested to estimate the local ME coefficient based on the switching spectroscopy PFM testing results.

  10. Magnetic-field-induced ferroelectric polarization reversal in magnetoelectric composites revealed by piezoresponse force microscopy.

    PubMed

    Miao, Hongchen; Zhou, Xilong; Dong, Shuxiang; Luo, Haosu; Li, Faxin

    2014-08-01

    Controlling electric polarization (or magnetization) in multiferroic materials with external magnetic fields (or electric fields) is very important for fundamental physics and spintronic devices. Although there has been some progress on magnetic-field-induced polarization reversal in single-phase multiferroics, such behavior has so far never been realized in composites. Here we show that it is possible to reverse ferroelectric polarization using magnetic fields in a bilayer Terfenol-D/PMN-33%PT composite. We realized this by ferroelectric domain imaging using piezoresponse force microscopy (PFM) under applied magnetic field loading. The internal electric field caused by the magnetoelectric (ME) effect in the PMN-PT crystal is considered as the driving force for the 180° polarization switching, and its existence is verified by switching spectroscopy PFM testing under a series of external magnetic fields. A quantitative method is further suggested to estimate the local ME coefficient based on the switching spectroscopy PFM testing results. PMID:24953042

  11. Electric field-induced magnetic switching in Mn:ZnO film

    SciTech Connect

    Ren, S. X.; Sun, G. W.; Zhao, J.; Dong, J. Y.; Zhao, X.; Chen, W.; Wei, Y.; Ma, Z. C.

    2014-06-09

    A large magnetic modulation, accompanied by stable bipolar resistive switching (RS) behavior, was observed in a Mn:ZnO film by applying a reversible electric field. A significant enhancement of the ferromagnetism of the film, to about five times larger than that in the initial (as-grown) state (IS), was obtained by switching the film into the low resistance state. X-ray photoelectron spectroscopy demonstrated the existence of abundant oxygen vacancies in the IS of the film. We suggest that this electric field-induced magnetic switching effect originates with the migration and redistribution of oxygen vacancies during RS. Our work indicates that electric switching is an effective and simple method to increase the ferromagnetism of diluted magnetic oxide films. This provides a promising direction for research in spintronic devices.

  12. Dynamics of magnetic particles near a surface: model and experiments on field-induced disaggregation.

    PubMed

    van Reenen, A; Gao, Y; de Jong, A M; Hulsen, M A; den Toonder, J M J; Prins, M W J

    2014-04-01

    Magnetic particles are widely used in biological research and bioanalytical applications. As the corresponding tools are progressively being miniaturized and integrated, the understanding of particle dynamics and the control of particles down to the level of single particles become important. Here, we describe a numerical model to simulate the dynamic behavior of ensembles of magnetic particles, taking account of magnetic interparticle interactions, interactions with the liquid medium and solid surfaces, as well as thermal diffusive motion of the particles. The model is verified using experimental data of magnetic field-induced disaggregation of magnetic particle clusters near a physical surface, wherein the magnetic field properties, particle size, cluster size, and cluster geometry were varied. Furthermore, the model clarifies how the cluster configuration, cluster alignment, magnitude of the field gradient, and the field repetition rate play a role in the particle disaggregation process. The simulation model will be very useful for further in silico studies on magnetic particle dynamics in biotechnological tools. PMID:24827250

  13. Theory of magnetic-field-induced polarization flop in spin-spiral multiferroics

    NASA Astrophysics Data System (ADS)

    Mochizuki, Masahito

    2015-12-01

    The magnetic-field-induced 90∘ flop of ferroelectric polarization P in a spin-spiral multiferroic material TbMnO3 is theoretically studied based on a microscopic spin model. I find that the direction of the P flop or the choice of +Pa or -Pa after the flop is governed by magnetic torques produced by the applied magnetic field H acting on the Mn spins and thus is selected in a deterministic way, in contradistinction to the naively anticipated probabilistic flop. This mechanism resolves a puzzle of the previously reported memory effect in the P direction depending on the history of the magnetic-field sweep, and enables controlled switching of multiferroic domains by externally applied magnetic fields. My Monte-Carlo analysis also uncovers that the magnetic structure in the P ∥a phase under H ∥b is not a previously anticipated simple a b -plane spin cycloid but a conical spin structure.

  14. Giant electric-field-induced strain in lead-free piezoelectric materials

    PubMed Central

    Chen, Lan; Yang, Yurong; Meng, X. K.

    2016-01-01

    First-principles calculations are performed to investigate the structures, electrical, and magnetic properties of compressive BiFeO3 films under electric-field and pressure perpendicular to the films. A reversible electric-field-induced strain up 10% is achieved in the compressive BiFeO3 films. The giant strain originates from rhombohedral-tetragonal (R-T) phase transition under electric-filed, and is recoverable from tetragonal-rhombohedral (T-R) phase transition by compressive stress. Additionally, the weak ferromagnetism in BiFeO3 films is largely changed in R-T phase transition under electric-filed and T-R phase transition under pressure – reminiscent of magnetoelectric effect and magnetoelastic effect. These results suggest exciting device opportunities arising from the giant filed-induced strain, large magnetoelectric effect and magnetoelastic effect. PMID:27139526

  15. Effect of dimerization on the field-induced birefringence in ferrofluids.

    PubMed

    Szczytko, Jacek; Vaupotič, Nataša; Osipov, Mihail A; Madrak, Karolina; Górecka, Ewa

    2013-06-01

    The magnetic-field-induced birefringence in a ferrofluid composed of spherical cobalt nanoparticles has been studied both experimentally and theoretically. The considerable induced birefringence determined experimentally has been attributed to the formation of chains of nanoparticles. The birefringence has been measured as a function of the external magnetic field and the volume fraction (f) of nanoparticles. It is quadratic in f as opposed to the Faraday effect, which is linear in f. Experimental results agree well with the theoretical model based on a simple density functional approach. For dilute solutions the experimental results can be explained by assuming that only dimers of nanoparticles are formed while the concentration of longer chains is negligible. PMID:23848690

  16. Giant electric-field-induced strain in lead-free piezoelectric materials

    NASA Astrophysics Data System (ADS)

    Chen, Lan; Yang, Yurong; Meng, X. K.

    2016-05-01

    First-principles calculations are performed to investigate the structures, electrical, and magnetic properties of compressive BiFeO3 films under electric-field and pressure perpendicular to the films. A reversible electric-field-induced strain up 10% is achieved in the compressive BiFeO3 films. The giant strain originates from rhombohedral-tetragonal (R-T) phase transition under electric-filed, and is recoverable from tetragonal-rhombohedral (T-R) phase transition by compressive stress. Additionally, the weak ferromagnetism in BiFeO3 films is largely changed in R-T phase transition under electric-filed and T-R phase transition under pressure – reminiscent of magnetoelectric effect and magnetoelastic effect. These results suggest exciting device opportunities arising from the giant filed-induced strain, large magnetoelectric effect and magnetoelastic effect.

  17. X-ray microtomography of field-induced macro-structures in a ferrofluid.

    SciTech Connect

    Lee, W.; X-Ray Science Division

    2010-09-01

    X-ray microtomography is used to visualize, in-situ, the three-dimensional nature of the magnetic field induced macro-structures (>1 ?m) inside a bulk (not, vert, similar1 mm diameter) magnetite-particle-mineral oil ferrofluid sample. Columnar structures of not, vert, similar10 ?m diameter were seen under a 0.35 kG applied magnetic field, while labyrinth type structures not, vert, similar4 ?m in width were seen at 0.55 kG. The structures have height/width aspect ratios >100. The results show that the magnetite volume fraction is not constant within the structures and on average is considerably less than a random sphere packing model.

  18. Magnetic-field-induced rotation of light with orbital angular momentum

    SciTech Connect

    Shi, Shuai; Ding, Dong-Sheng Zhou, Zhi-Yuan; Li, Yan; Zhang, Wei; Shi, Bao-Sen

    2015-06-29

    Light carrying orbital angular momentum (OAM) has attractive applications in the fields of precise optical measurements and high capacity optical communications. We study the rotation of a light beam propagating in warm {sup 87}Rb atomic vapor using a method based on magnetic-field-induced circular birefringence. The dependence of the rotation angle on the magnetic field makes it appropriate for weak magnetic field measurements. We quote a detailed theoretical description that agrees well with the experimental observations. The experiment shown here provides a method to measure the magnetic field intensity precisely and expands the application of OAM-carrying light. This technique has advantage in measurement of magnetic field weaker than 0.5 G, and the precision we achieved is 0.8 mG.

  19. Magnetic-Field-Induced Rotation of Polarized Light Emission from Monolayer WS_{2}.

    PubMed

    Schmidt, Robert; Arora, Ashish; Plechinger, Gerd; Nagler, Philipp; Granados Del Águila, Andrés; Ballottin, Mariana V; Christianen, Peter C M; Michaelis de Vasconcellos, Steffen; Schüller, Christian; Korn, Tobias; Bratschitsch, Rudolf

    2016-08-12

    We control the linear polarization of emission from the coherently emitting K^{+} and K^{-} valleys (valley coherence) in monolayer WS_{2} with an out-of-plane magnetic field of up to 25 T. The magnetic-field-induced valley Zeeman splitting causes a rotation of the emission polarization with respect to the excitation by up to 35° and reduces the polarization degree by up to 16%. We explain both of these phenomena with a model based on two noninteracting coherent two-level systems. We deduce that the coherent light emission from the valleys decays with a time constant of τ_{c}=260  fs. PMID:27563997

  20. Interpreting angina: symptoms along a gender continuum

    PubMed Central

    Crea-Arsenio, Mary; Shannon, Harry S; Velianou, James L; Giacomini, Mita

    2016-01-01

    Background ‘Typical’ angina is often used to describe symptoms common among men, while ‘atypical’ angina is used to describe symptoms common among women, despite a higher prevalence of angina among women. This discrepancy is a source of controversy in cardiac care among women. Objectives To redefine angina by (1) qualitatively comparing angina symptoms and experiences in women and men and (2) to propose a more meaningful construct of angina that integrates a more gender-centred approach. Methods Patients were recruited between July and December 2010 from a tertiary cardiac care centre and interviewed immediately prior to their first angiogram. Symptoms were explored through in-depth semi-structured interviews, transcribed verbatim and analysed concurrently using a modified grounded theory approach. Angiographically significant disease was assessed at ≥70% stenosis of a major epicardial vessel. Results Among 31 total patients, 13 men and 14 women had angiograpically significant CAD. Patients describe angina symptoms according to 6 symptomatic subthemes that array along a ‘gender continuum’. Gender-specific symptoms are anchored at each end of the continuum. At the centre of the continuum, are a remarkably large number of symptoms commonly expressed by both men and women. Conclusions The ‘gender continuum’ offers new insights into angina experiences of angiography candidates. Notably, there is more overlap of shared experiences between men and women than conventionally thought. The gender continuum can help researchers and clinicians contextualise patient symptom reports, avoiding the conventional ‘typical’ versus ‘atypical’ distinction that can misrepresent gendered angina experiences. PMID:27158523

  1. Continuum description of avalanches in granular media.

    SciTech Connect

    Aranson, I. S.; Tsimring, L. S.

    2000-12-05

    A continuum theory of partially fluidized granular flows is proposed. The theory is based on a combination of the mass and momentum conservation equations with the order parameter equation which describes the transition between flowing and static components of the granular system. We apply this model to the dynamics of avalanches in chutes. The theory provides a quantitative description of recent observations of granular flows on rough inclined planes (Daerr and Douady 1999): layer bistability, and the transition from triangular avalanches propagating downhill at small inclination angles to balloon-shaped avalanches also propagating uphill for larger angles.

  2. Dust continuum spectra from model HII regions

    NASA Technical Reports Server (NTRS)

    Aannestad, P. A.; Emery, R. J.

    1989-01-01

    The infrared spectrum emitted by nebular dust, heated by the ionizing stars in H II blisters and spherical H II regions, is calculated for various model parameters. Absorption of the non-ionizing radiation in a neutral layer is included. Heating by the Lyman alpha photon field is taken into account. The dust is composed of silicate and graphite grains, and evaporation of the grains in the inner region is considered. The models are presented with a view to interpretation of infrared observations of dusty H II regions and can be applied directly to the infrared astronomy satellite survey data. The continuum emission is compared with calculated fine structure line emission.

  3. Continuum modeling of clustering of myxobacteria

    PubMed Central

    Harvey, Cameron W.; Alber, Mark; Tsimring, Lev S.; Aranson, Igor S.

    2013-01-01

    In this paper we develop a continuum theory of clustering in ensembles of self-propelled inelastically colliding rods with applications to collective dynamics of common gliding bacteria Myxococcus Xanthus. A multiphase hydrodynamic model that couples densities of oriented and isotropic phases is described. This model is used for the analysis of an instability that leads to spontaneous formation of directionally moving dense clusters within initially dilute isotropic “gas” of myxobacteria. Numerical simulations of this model confirm the existence of stationary dense moving clusters and also elucidate the properties of their collisions. The results are shown to be in a qualitative agreement with experiments. PMID:23712128

  4. Continuum regularization of gauge theory with fermions

    SciTech Connect

    Chan, H.S.

    1987-03-01

    The continuum regularization program is discussed in the case of d-dimensional gauge theory coupled to fermions in an arbitrary representation. Two physically equivalent formulations are given. First, a Grassmann formulation is presented, which is based on the two-noise Langevin equations of Sakita, Ishikawa and Alfaro and Gavela. Second, a non-Grassmann formulation is obtained by regularized integration of the matter fields within the regularized Grassmann system. Explicit perturbation expansions are studied in both formulations, and considerable simplification is found in the integrated non-Grassmann formalism.

  5. Radiation from charges in the continuum limit

    SciTech Connect

    Ianconescu, Reuven

    2013-06-15

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

  6. The role of Rydberg and continuum levels in computing high harmonic generation spectra of the hydrogen atom using time-dependent configuration interaction

    SciTech Connect

    Luppi, Eleonora; Head-Gordon, Martin

    2013-10-28

    We study the role of Rydberg bound-states and continuum levels in the field-induced electronic dynamics associated with the High-Harmonic Generation (HHG) spectroscopy of the hydrogen atom. Time-dependent configuration-interaction (TD-CI) is used with very large atomic orbital (AO) expansions (up to L= 4 with sextuple augmentation and off-center functions) to describe the bound Rydberg levels, and some continuum levels. To address the lack of ionization losses in TD-CI with finite AO basis sets, we employed a heuristic lifetime for energy levels above the ionization potential. The heuristic lifetime model is compared against the conventional atomic orbital treatment (infinite lifetimes), and a third approximation which is TD-CI using only the bound levels (continuum lifetimes go to zero). The results suggest that spectra calculated using conventional TD-CI do not converge with increasing AO basis set size, while the zero lifetime and heuristic lifetime models converge to qualitatively similar spectra, with implications for how best to apply bound state electronic structure methods to simulate HHG. The origin of HHG spectral features including the cutoff and extent of interference between peaks is uncovered by separating field-induced coupling between different types of levels (ground state, bound Rydberg levels, and continuum) in the simulated electronic dynamics. Thus the origin of deviations between the predictions of the semi-classical three step model and the full simulation can be associated with particular physical contributions, which helps to explain both the successes and the limitations of the three step model.

  7. The Luminosity Dependence of Quasar UV Continuum Slope: Dust Extinction Scenario

    NASA Astrophysics Data System (ADS)

    Xie, Xiaoyi; Shao, Zhengyi; Shen, Shiyin; Liu, Hui; Li, Linlin

    2016-06-01

    We investigate the UV continuum slope α of a large quasar sample from SDSS DR7. By using specific continuum windows, we build two samples at lower (0.71\\lt z\\lt 1.19) and higher (1.90\\lt z\\lt 3.15) redshifts, which correspond to the continuum slopes at longer (near-UV) and shorter (far-UV) rest wavelength ranges, respectively. Overall, the average continuum slopes are ‑0.36 and ‑0.51 for {α }{{NUV}} and {α }{{FUV}} with similar dispersions {σ }α ∼ 0.5. For both samples, we confirm the luminosity dependence of the continuum slope, i.e., fainter quasars have redder spectra. We further find that both {α }{{NUV}} and {α }{{FUV}} have a common upper limit (∼ 1/3), which is almost independent of the quasar luminosity {L}{{bol}}. This finding implies that the intrinsic quasar continuum (or the bluest quasar), at any luminosity, obeys the standard thin-disk model. We propose that the other quasars with redder α are caused by the reddening from the dust locally. With this assumption, we employ the dust extinction scenario to model the observed {L}{{bol}}{--}α relation. We find that a typical value of E(B-V)∼ 0.1{--}0.3 {mag} (depending on the types of extinction curve) of the quasar local dust is enough to explain the discrepancy of α between the observation (∼ -0.5) and the standard accretion disk model prediction (∼ 1/3).

  8. Discovery of a complex linearly polarized spectrum of Betelgeuse dominated by depolarization of the continuum

    NASA Astrophysics Data System (ADS)

    Aurière, M.; López Ariste, A.; Mathias, P.; Lèbre, A.; Josselin, E.; Montargès, M.; Petit, P.; Chiavassa, A.; Paletou, F.; Fabas, N.; Konstantinova-Antova, R.; Donati, J.-F.; Grunhut, J. H.; Wade, G. A.; Herpin, F.; Kervella, P.; Perrin, G.; Tessore, B.

    2016-06-01

    Context. Betelgeuse is an M supergiant that harbors spots and giant granules at its surface and presents linear polarization of its continuum. Aims: We have previously discovered linear polarization signatures associated with individual lines in the spectra of cool and evolved stars. Here, we investigate whether a similar linearly polarized spectrum exists for Betelgeuse. Methods: We used the spectropolarimeter Narval, combining multiple polarimetric sequences to obtain high signal-to-noise ratio spectra of individual lines, as well as the least-squares deconvolution (LSD) approach, to investigate the presence of an averaged linearly polarized profile for the photospheric lines. Results: We have discovered the existence of a linearly polarized spectrum for Betelgeuse, detecting a rather strong signal (at a few times 10-4 of the continuum intensity level), both in individual lines and in the LSD profiles. Studying its properties and the signal observed for the resonant Na i D lines, we conclude that we are mainly observing depolarization of the continuum by the absorption lines. The linear polarization of the Betelgeuse continuum is due to the anisotropy of the radiation field induced by brightness spots at the surface and Rayleigh scattering in the atmosphere. We have developed a geometrical model to interpret the observed polarization, from which we infer the presence of two brightness spots and their positions on the surface of Betelgeuse. We show that applying the model to each velocity bin along the Stokes Q and U profiles allows the derivation of a map of the bright spots. We use the Narval linear polarization observations of Betelgeuse obtained over a period of 1.4 yr to study the evolution of the spots and of the atmosphere. Conclusions: Our study of the linearly polarized spectrum of Betelgeuse provides a novel method for studying the evolution of brightness spots at its surface and complements quasi-simultaneous observations obtained with PIONIER at the

  9. Continuum robot arms inspired by cephalopods

    NASA Astrophysics Data System (ADS)

    Walker, Ian D.; Dawson, Darren M.; Flash, Tamar; Grasso, Frank W.; Hanlon, Roger T.; Hochner, Binyamin; Kier, William M.; Pagano, Christopher C.; Rahn, Christopher D.; Zhang, Qiming M.

    2005-05-01

    In this paper, we describe our recent results in the development of a new class of soft, continuous backbone ("continuum") robot manipulators. Our work is strongly motivated by the dexterous appendages found in cephalopods, particularly the arms and suckers of octopus, and the arms and tentacles of squid. Our ongoing investigation of these animals reveals interesting and unexpected functional aspects of their structure and behavior. The arrangement and dynamic operation of muscles and connective tissue observed in the arms of a variety of octopus species motivate the underlying design approach for our soft manipulators. These artificial manipulators feature biomimetic actuators, including artificial muscles based on both electro-active polymers (EAP) and pneumatic (McKibben) muscles. They feature a "clean" continuous backbone design, redundant degrees of freedom, and exhibit significant compliance that provides novel operational capacities during environmental interaction and object manipulation. The unusual compliance and redundant degrees of freedom provide strong potential for application to delicate tasks in cluttered and/or unstructured environments. Our aim is to endow these compliant robotic mechanisms with the diverse and dexterous grasping behavior observed in octopuses. To this end, we are conducting fundamental research into the manipulation tactics, sensory biology, and neural control of octopuses. This work in turn leads to novel approaches to motion planning and operator interfaces for the robots. The paper describes the above efforts, along with the results of our development of a series of continuum tentacle-like robots, demonstrating the unique abilities of biologically-inspired design.

  10. Polarized Continuum Radiation from Stellar Atmospheres

    NASA Astrophysics Data System (ADS)

    Harrington, J. Patrick

    2015-10-01

    Continuum scattering by free electrons can be significant in early type stars, while in late type stars Rayleigh scattering by hydrogen atoms or molecules may be important. Computer programs used to construct models of stellar atmospheres generally treat the scattering of the continuum radiation as isotropic and unpolarized, but this scattering has a dipole angular dependence and will produce polarization. We review an accurate method for evaluating the polarization and limb darkening of the radiation from model stellar atmospheres. We use this method to obtain results for: (i) Late type stars, based on the MARCS code models (Gustafsson et al. 2008), and (ii) Early type stars, based on the NLTE code TLUSTY (Lanz and Hubeny 2003). These results are tabulated at http://www.astro.umd.edu/~jph/Stellar_Polarization.html. While the net polarization vanishes for an unresolved spherical star, this symmetry is broken by rapid rotation or by the masking of part of the star by a binary companion or during the transit of an exoplanet. We give some numerical results for these last cases.

  11. Mid-IR super-continuum generation

    NASA Astrophysics Data System (ADS)

    Islam, Mohammed N.; Xia, Chenan; Freeman, Mike J.; Mauricio, Jeremiah; Zakel, Andy; Ke, Kevin; Xu, Zhao; Terry, Fred L., Jr.

    2009-02-01

    A Mid-InfraRed FIber Laser (MIRFIL) has been developed that generates super-continuum covering the spectral range from 0.8 to 4.5 microns with a time-averaged power as high as 10.5W. The MIRFIL is an all-fiber integrated laser with no moving parts and no mode-locked lasers that uses commercial off-the-shelf parts and leverages the mature telecom/fiber optics platform. The MIRFIL power can be easily scaled by changing the repetition rate and modifying the erbium-doped fiber amplifier. Some of the applications using the super-continuum laser will be described in defense, homeland security and healthcare. For example, the MIRFIL is being applied to a catheter-based medical diagnostic system to detect vulnerable plaque, which is responsible for most heart attacks resulting from hardening-of-the-arteries or atherosclerosis. More generally, the MIRFIL can be a platform for selective ablation of lipids without damaging normal protein or smooth muscle tissue.

  12. The Urban Watershed Continuum: Biogeochemistry of Carbon

    NASA Astrophysics Data System (ADS)

    Kaushal, S.; Belt, K.; Smith, C.; Newcomb, K.; Newcomer, T. A.; Smith, R.; Duan, S.; Findlay, S.; Groffman, P. M.; Mayer, P. M.

    2012-12-01

    Urban ecosystems are constantly evolving, and they are expected to change in both space and time. We explore the relationship between infrastructure and ecosystem function relevant to the inorganic and organic carbon cycle along urban watersheds across spatial and temporal dimensions. We provide examples from watersheds of the Baltimore Ecosystem Study Long-Term Ecological (LTER) and Washington D.C. Urban Long-Term Research Area (ULTRA EX) sites with varying land use and contrasting sanitary sewer systems. At a stream and river network scale, there are distinct longitudinal patterns in dissolved inorganic carbon, dissolved organic carbon, and particulate carbon concentrations from suburban headwaters to progressively urbanized receiving waters. There are also distinct changes in stable isotopic signatures of organic carbon and inorganic carbon suggesting shifts in carbon sources and processing throughout urban stream and river networks. Longitudinal patterns appear to be related to in-stream transformations, as suggested by high frequency sensor measurements, mass balances, and diurnal sampling. We suggest that stream and river networks act as "transformers" of watershed nitrogen and phosphorus pollution to increasingly generate carbon throughout the urban watershed continuum via biological processes. Additionally, sources and quality of carbon may vary with watershed inputs from suburban headwaters to progressively urbanized downstream reaches. The role of the urban watershed continuum as a "transporter" and "transformer" of organic matter has important implications for anticipating changes in the forms and reactivity of carbon delivered to receiving waters and coastal zones.

  13. Atomistic to continuum modeling of solidification microstructures

    SciTech Connect

    Karma, Alain; Tourret, Damien

    2015-09-26

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

  14. Atomistic to continuum modeling of solidification microstructures

    DOE PAGESBeta

    Karma, Alain; Tourret, Damien

    2015-09-26

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

  15. Accurate Molecular Polarizabilities Based on Continuum Electrostatics

    PubMed Central

    Truchon, Jean-François; Nicholls, Anthony; Iftimie, Radu I.; Roux, Benoît; Bayly, Christopher I.

    2013-01-01

    A novel approach for representing the intramolecular polarizability as a continuum dielectric is introduced to account for molecular electronic polarization. It is shown, using a finite-difference solution to the Poisson equation, that the Electronic Polarization from Internal Continuum (EPIC) model yields accurate gas-phase molecular polarizability tensors for a test set of 98 challenging molecules composed of heteroaromatics, alkanes and diatomics. The electronic polarization originates from a high intramolecular dielectric that produces polarizabilities consistent with B3LYP/aug-cc-pVTZ and experimental values when surrounded by vacuum dielectric. In contrast to other approaches to model electronic polarization, this simple model avoids the polarizability catastrophe and accurately calculates molecular anisotropy with the use of very few fitted parameters and without resorting to auxiliary sites or anisotropic atomic centers. On average, the unsigned error in the average polarizability and anisotropy compared to B3LYP are 2% and 5%, respectively. The correlation between the polarizability components from B3LYP and this approach lead to a R2 of 0.990 and a slope of 0.999. Even the F2 anisotropy, shown to be a difficult case for existing polarizability models, can be reproduced within 2% error. In addition to providing new parameters for a rapid method directly applicable to the calculation of polarizabilities, this work extends the widely used Poisson equation to areas where accurate molecular polarizabilities matter. PMID:23646034

  16. Three-dimensional electric field visualization utilizing electric-field-induced second-harmonic generation in nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Chen, I.-Hsiu; Chu, Shi-Wei; Bresson, Francois; Tien, Ming-Chun; Shi, Jin-Wei; Sun, Chi-Kuang

    2003-08-01

    An electric-field-induced second-harmonic-generation signal in a nematic liquid crystal is used to map the electric field in an integrated-circuit-like sample. Since the electric-field-induced second-harmonic-generation signal intensity exhibits a strong dependence on the polarization of the incident laser beam, both the amplitude and the orientation of the electric field vectors can be measured. Combined with scanning second-harmonic-generation microscopy, three-dimensional electric field distribution can be easily visualized with high spatial resolution of the order of 1 μm.

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

    SciTech Connect

    Braginsky, A. Ya.

    2007-07-15

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

  18. Non-coherent continuum scattering as a line polarization mechanism

    SciTech Connect

    Del Pino Alemán, T.; Manso Sainz, R.; Trujillo Bueno, J. E-mail: rsainz@iac.es

    2014-03-20

    Line scattering polarization can be strongly affected by Rayleigh scattering at neutral hydrogen and Thomson scattering at free electrons. Often a depolarization of the continuum results, but the Doppler redistribution produced by the continuum scatterers, which are light (hence, fast), induces more complex interactions between the polarization in spectral lines and in the continuum. Here we formulate and solve the radiative transfer problem of scattering line polarization with non-coherent continuum scattering consistently. The problem is formulated within the spherical tensor representation of atomic and light polarization. The numerical method of solution is a generalization of the Accelerated Lambda Iteration that is applied to both the atomic system and the radiation field. We show that the redistribution of the spectral line radiation due to the non-coherence of the continuum scattering may modify the shape of the emergent fractional linear polarization patterns significantly, even yielding polarization signals above the continuum level in intrinsically unpolarizable lines.

  19. Continuum capture in the three-body problem

    SciTech Connect

    Sellin, I A

    1980-01-01

    The three-body problem, especially the problem of electron capture to the continuum in heavy particle collisions is reviewed. Major topics covered include: second born-induced asymmetry in electron capture to the continuum; historical context, links to other tests of atomic scattering theory; experiments characterizing the velocity distribution of ECC electrons; other atomic physics tests of high velocity Born expansions; atom capture; capture by positrons; and pion capture to the continuum. (GHT)

  20. Radio continuum and far-infrared emission of spiral galaxies: Implications of correlations

    NASA Technical Reports Server (NTRS)

    Rengarajan, T. N.; Iyengar, K. V. K.

    1990-01-01

    Researchers present a study extending the correlation seen between radio continuum and far-infrared emissions from spiral galaxies to a lower frequency of 408 MHz and also as a function of radio spectral index. The tight correlation seen between the two luminosities is then used to constrain several parameters governing the emissions such as the changes in star formation rate and mass function, frequency of supernovae that are parents of the interstellar electrons and factors governing synchrotron radio emission.

  1. Continuum Fatigue Damage Modeling for Use in Life Extending Control

    NASA Technical Reports Server (NTRS)

    Lorenzo, Carl F.

    1994-01-01

    This paper develops a simplified continuum (continuous wrp to time, stress, etc.) fatigue damage model for use in Life Extending Controls (LEC) studies. The work is based on zero mean stress local strain cyclic damage modeling. New nonlinear explicit equation forms of cyclic damage in terms of stress amplitude are derived to facilitate the continuum modeling. Stress based continuum models are derived. Extension to plastic strain-strain rate models are also presented. Application of these models to LEC applications is considered. Progress toward a nonzero mean stress based continuum model is presented. Also, new nonlinear explicit equation forms in terms of stress amplitude are also derived for this case.

  2. Broadly continuously tunable slot waveguide quantum cascade lasers based on a continuum-to-continuum active region design

    SciTech Connect

    Meng, Bo; Zeng, Yong Quan; Liang, Guozhen; Hu, Xiao Nan; Rodriguez, Etienne; Wang, Qi Jie

    2015-09-14

    We report our progress in the development of broadly tunable single-mode slot waveguide quantum cascade lasers based on a continuum-to-continuum active region design. The electroluminescence spectrum of the continuum-to-continuum active region design has a full width at half maximum of 440 cm{sup −1} at center wavelength ∼10 μm at room temperature (300 K). Devices using the optimized slot waveguide structure and the continuum-to-continuum design can be tuned continuously with a lasing emission over 42 cm{sup −1}, from 9.74 to 10.16 μm, at room temperature by using only current tuning scheme, together with a side mode suppression ratio of above 15 dB within the whole tuning range.

  3. Three-dimensionality of field-induced magnetism in a high-temperature superconductor.

    PubMed

    Lake, B; Lefmann, K; Christensen, N B; Aeppli, G; McMorrow, D F; Ronnow, H M; Vorderwisch, P; Smeibidl, P; Mangkorntong, N; Sasagawa, T; Nohara, M; Takagi, H

    2005-09-01

    Many physical properties of high-temperature superconductors are two-dimensional phenomena derived from their square-planar CuO2 building blocks. This is especially true of the magnetism from the copper ions. As mobile charge carriers enter the CuO2 layers, the antiferromagnetism of the parent insulators, where each copper spin is antiparallel to its nearest neighbours, evolves into a fluctuating state where the spins show tendencies towards magnetic order of a longer periodicity. For certain charge-carrier densities, quantum fluctuations are sufficiently suppressed to yield static long-period order, and external magnetic fields also induce such order. Here we show that, in contrast to the chemically controlled order in superconducting samples, the field-induced order in these same samples is actually three-dimensional, implying significant magnetic linkage between the CuO2 planes. The results are important because they show that there are three-dimensional magnetic couplings that survive into the superconducting state, and coexist with the crucial inter-layer couplings responsible for three-dimensional superconductivity. Both types of coupling will straighten the vortex lines, implying that we have finally established a direct link between technical superconductivity, which requires zero electrical resistance in an applied magnetic field and depends on vortex dynamics, and the underlying antiferromagnetism of the cuprates. PMID:16100515

  4. Probing of field-induced structures and tunable rheological properties of surfactant capped magnetically polarizable nanofluids.

    PubMed

    Felicia, Leona J; Philip, John

    2013-01-01

    Oil-based nanofluid containing surfactant-capped magnetite nanoparticles are synthesized by a simple coprecipitation approach, and their magnetorheological properties are studied for different magnetic field strengths and volume fractions. We observe a distinct "plateau-like region" in the shear thinning viscosity curve, under an external magnetic field, possibly due to a peculiar alignment of the chains with respect to the field direction where the structure is stable against fragmentation. The observed plateau regime is reminiscent to that of kinetically arrested gel networks. Interestingly, such a plateau regime has been observed only above certain critical magnetic field when the dipolar interaction strength is much greater than the thermal energy where the aggregation becomes a nonequilibrium transport-limited process. The good collapse of specific viscosity data against Mason number for different magnetic field strengths onto a single curve suggests the dominance of hydrodynamic and magnetic forces on thermal force above a certain magnetic field strength. The observed increase in both static and dynamic yield stresses under the magnetic field confirms the formation of columnar structures that hinder the flow behavior. The hysteresis observed in the magnetic sweep experiments shows the inability of the chains to relax within the measurement time. The dynamic measurements confirm that the field-induced structures impart elastic behavior to the dispersion, which is found to increase with magnetic field and saturates at higher field strengths. PMID:23210900

  5. Electric-field-induced local and mesoscale structural changes in polycrystalline dielectrics and ferroelectrics

    DOE PAGESBeta

    Usher, Tedi -Marie; Levin, Igor; Daniels, John E.; Jones, Jacob L.

    2015-10-01

    In this study, the atomic-scale response of dielectrics/ferroelectrics to electric fields is central to their functionality. Here we introduce an in situ characterization method that reveals changes in the local atomic structure in polycrystalline materials under fields. The method employs atomic pair distribution functions (PDFs), determined from X-ray total scattering that depends on orientation relative to the applied field, to probe structural changes over length scales from sub-Ångstrom to several nanometres. The PDF is sensitive to local ionic displacements and their short-range order, a key uniqueness relative to other techniques. The method is applied to representative ferroelectrics, BaTiO3 and Na½Bi½TiO3,more » and dielectric SrTiO3. For Na½Bi½TiO3, the results reveal an abrupt field-induced monoclinic to rhombohedral phase transition, accompanied by ordering of the local Bi displacements and reorientation of the nanoscale ferroelectric domains. For BaTiO3 and SrTiO3, the local/nanoscale structural changes observed in the PDFs are dominated by piezoelectric lattice strain and ionic polarizability, respectively.« less

  6. Electric-field-induced local and mesoscale structural changes in polycrystalline dielectrics and ferroelectrics

    SciTech Connect

    Usher, Tedi -Marie; Levin, Igor; Daniels, John E.; Jones, Jacob L.

    2015-10-01

    In this study, the atomic-scale response of dielectrics/ferroelectrics to electric fields is central to their functionality. Here we introduce an in situ characterization method that reveals changes in the local atomic structure in polycrystalline materials under fields. The method employs atomic pair distribution functions (PDFs), determined from X-ray total scattering that depends on orientation relative to the applied field, to probe structural changes over length scales from sub-Ångstrom to several nanometres. The PDF is sensitive to local ionic displacements and their short-range order, a key uniqueness relative to other techniques. The method is applied to representative ferroelectrics, BaTiO3 and Na½Bi½TiO3, and dielectric SrTiO3. For Na½Bi½TiO3, the results reveal an abrupt field-induced monoclinic to rhombohedral phase transition, accompanied by ordering of the local Bi displacements and reorientation of the nanoscale ferroelectric domains. For BaTiO3 and SrTiO3, the local/nanoscale structural changes observed in the PDFs are dominated by piezoelectric lattice strain and ionic polarizability, respectively.

  7. Electric field induced Lyman-α emission of a hydrogen beam for electric field measurements.

    PubMed

    Chérigier-Kovacic, L; Ström, P; Lejeune, A; Doveil, F

    2015-06-01

    Electric field induced Lyman-α emission is a new way of measuring weak electric fields in vacuum and in a plasma. It is based on the emission of Lyman-α radiation (121.6 nm) by a low-energy metastable H atom beam due to Stark-quenching of the 2s level induced by the field. In this paper, we describe the technique in detail. Test measurements have been performed in vacuum between two plates polarized at a controlled voltage. The intensity of emitted radiation, proportional to the square of the field modulus, has been recorded by a lock-in technique, which gives an excellent signal to noise ratio. These measurements provide an in situ calibration that can be used to obtain the absolute value of the electric field. A diagnostic of this type can help to address a long standing challenge in plasma physics, namely, the problem of measuring electric fields without disturbing the equilibrium of the system that is being studied. PMID:26133836

  8. Electric field induced birefringence in non-aqueous dispersions of mineral nanorods.

    PubMed

    de la Cotte, Alexis; Merzeau, Pascal; Kim, Jong Wook; Lahlil, Khalid; Boilot, Jean-Pierre; Gacoin, Thierry; Grelet, Eric

    2015-09-01

    Lanthanum phosphate (LaPO4) nanorods dispersed in the non-aqueous solvent of ethylene glycol form a system exhibiting large intrinsic birefringence, high colloidal stability and the ability to self-organize into liquid crystalline phases. In order to probe the electro-optical response of these rod dispersions we study here the electric-field-induced birefringence, also called Kerr effect, for a concentrated isotropic liquid state with an in-plane a.c. sinusoidal electric field, in conditions of directly applied (electrodes in contact with the sample) or externally applied (electrodes outside the sample cell) fields. Performing an analysis of the electric polarizability of our rod-like particles in the framework of Maxwell-Wagner-O'Konski theory, we account quantitatively for the coupling between the induced steady-state birefringence and the electric field as a function of the voltage frequency for both sample geometries. The switching time of this non-aqueous transparent system has been measured, and combined with its high Kerr coefficients and its features of optically isotropic "off-state" and athermal phase behavior, this represents a promising proof-of-concept for the integration of anisotropic nanoparticle suspensions into a new generation of electro-optical devices. PMID:26189711

  9. Magnetic field induced 1st order transitions: Recent studies, and some new concepts

    NASA Astrophysics Data System (ADS)

    Chaddah, P.

    2015-05-01

    Phase transitions are caused by varying temperature, or pressure, or magnetic field. The observation of 1st order magneto-structural transitions has created application possibilities based on magnetoresistance, magnetocaloric effect, magnetic shape memory effect, and magneto-dielectric effect. Magnetic field induced transitions, and phase coexistence of competing magnetic phases down to the lowest temperature, gained prominence over a decade ago with theoretical models suggesting that the ground state is not homogeneous. Researchers at Indore pushed an alternative view that this phase coexistence could be due to glasslike "kinetic arrest" of a disorder-broadened first-order magnetic transition between two states with long-range magnetic order, resulting in phase coexistence down to the lowest temperatures. The CHUF (cooling and heating in unequal field) protocol created at Indore allows the observation of `devitrification', followed by `melting'. I show examples of measurements establishing kinetic arrest in various materials, emphasizing that glasslike arrest of 1st order magnetic transitions may be as ubiquitous as glass formation following the arrest of 1st order structural transitions.

  10. The influence of sulcus width on simulated electric fields induced by transcranial magnetic stimulation

    NASA Astrophysics Data System (ADS)

    Janssen, A. M.; Rampersad, S. M.; Lucka, F.; Lanfer, B.; Lew, S.; Aydin, Ü.; Wolters, C. H.; Stegeman, D. F.; Oostendorp, T. F.

    2013-07-01

    Volume conduction models can help in acquiring knowledge about the distribution of the electric field induced by transcranial magnetic stimulation. One aspect of a detailed model is an accurate description of the cortical surface geometry. Since its estimation is difficult, it is important to know how accurate the geometry has to be represented. Previous studies only looked at the differences caused by neglecting the complete boundary between cerebrospinal fluid (CSF) and grey matter (Thielscher et al 2011 NeuroImage 54 234-43, Bijsterbosch et al 2012 Med. Biol. Eng. Comput. 50 671-81), or by resizing the whole brain (Wagner et al 2008 Exp. Brain Res. 186 539-50). However, due to the high conductive properties of the CSF, it can be expected that alterations in sulcus width can already have a significant effect on the distribution of the electric field. To answer this question, the sulcus width of a highly realistic head model, based on T1-, T2- and diffusion-weighted magnetic resonance images, was altered systematically. This study shows that alterations in the sulcus width do not cause large differences in the majority of the electric field values. However, considerable overestimation of sulcus width produces an overestimation of the calculated field strength, also at locations distant from the target location.

  11. Magnetic field-induced helical mode and topological transitions in a topological insulator nanoribbon.

    PubMed

    Jauregui, Luis A; Pettes, Michael T; Rokhinson, Leonid P; Shi, Li; Chen, Yong P

    2016-04-01

    The spin-helical Dirac fermion topological surface states in a topological insulator nanowire or nanoribbon promise novel topological devices and exotic physics such as Majorana fermions. Here, we report local and non-local transport measurements in Bi2Te3 topological insulator nanoribbons that exhibit quasi-ballistic transport over ∼2 μm. The conductance versus axial magnetic flux Φ exhibits Aharonov-Bohm oscillations with maxima occurring alternately at half-integer or integer flux quanta (Φ0 = h/e, where h is Planck's constant and e is the electron charge) depending periodically on the gate-tuned Fermi wavevector (kF) with period 2π/C (where C is the nanoribbon circumference). The conductance versus gate voltage also exhibits kF-periodic oscillations, anti-correlated between Φ = 0 and Φ0/2. These oscillations enable us to probe the Bi2Te3 band structure, and are consistent with the circumferentially quantized topological surface states forming a series of one-dimensional subbands, which undergo periodic magnetic field-induced topological transitions with the disappearance/appearance of the gapless Dirac point with a one-dimensional spin helical mode. PMID:26780658

  12. Electric-field-induced local and mesoscale structural changes in polycrystalline dielectrics and ferroelectrics

    PubMed Central

    Usher, Tedi-Marie; Levin, Igor; Daniels, John E.; Jones, Jacob L.

    2015-01-01

    The atomic-scale response of dielectrics/ferroelectrics to electric fields is central to their functionality. Here we introduce an in situ characterization method that reveals changes in the local atomic structure in polycrystalline materials under fields. The method employs atomic pair distribution functions (PDFs), determined from X-ray total scattering that depends on orientation relative to the applied field, to probe structural changes over length scales from sub-Ångstrom to several nanometres. The PDF is sensitive to local ionic displacements and their short-range order, a key uniqueness relative to other techniques. The method is applied to representative ferroelectrics, BaTiO3 and Na½Bi½TiO3, and dielectric SrTiO3. For Na½Bi½TiO3, the results reveal an abrupt field-induced monoclinic to rhombohedral phase transition, accompanied by ordering of the local Bi displacements and reorientation of the nanoscale ferroelectric domains. For BaTiO3 and SrTiO3, the local/nanoscale structural changes observed in the PDFs are dominated by piezoelectric lattice strain and ionic polarizability, respectively. PMID:26424360

  13. SEM technique for imaging and measuring electronic transport in nanocomposites based on electric field induced contrast

    DOEpatents

    Jesse, Stephen [Knoxville, TN; Geohegan, David B [Knoxville, TN; Guillorn, Michael [Brooktondale, NY

    2009-02-17

    Methods and apparatus are described for SEM imaging and measuring electronic transport in nanocomposites based on electric field induced contrast. A method includes mounting a sample onto a sample holder, the sample including a sample material; wire bonding leads from the sample holder onto the sample; placing the sample holder in a vacuum chamber of a scanning electron microscope; connecting leads from the sample holder to a power source located outside the vacuum chamber; controlling secondary electron emission from the sample by applying a predetermined voltage to the sample through the leads; and generating an image of the secondary electron emission from the sample. An apparatus includes a sample holder for a scanning electron microscope having an electrical interconnect and leads on top of the sample holder electrically connected to the electrical interconnect; a power source and a controller connected to the electrical interconnect for applying voltage to the sample holder to control the secondary electron emission from a sample mounted on the sample holder; and a computer coupled to a secondary electron detector to generate images of the secondary electron emission from the sample.

  14. Observatory geoelectric fields induced in a two-layer lithosphere during magnetic storms

    USGS Publications Warehouse

    Love, Jeffrey J.; Swidinsky, Andrei

    2015-01-01

    We report on the development and validation of an algorithm for estimating geoelectric fields induced in the lithosphere beneath an observatory during a magnetic storm. To accommodate induction in three-dimensional lithospheric electrical conductivity, we analyze a simple nine-parameter model: two horizontal layers, each with uniform electrical conductivity properties given by independent distortion tensors. With Laplace transformation of the induction equations into the complex frequency domain, we obtain a transfer function describing induction of observatory geoelectric fields having frequency-dependent polarization. Upon inverse transformation back to the time domain, the convolution of the corresponding impulse-response function with a geomagnetic time series yields an estimated geoelectric time series. We obtain an optimized set of conductivity parameters using 1-s resolution geomagnetic and geoelectric field data collected at the Kakioka, Japan, observatory for five different intense magnetic storms, including the October 2003 Halloween storm; our estimated geoelectric field accounts for 93% of that measured during the Halloween storm. This work demonstrates the need for detailed modeling of the Earth’s lithospheric conductivity structure and the utility of co-located geomagnetic and geoelectric monitoring.

  15. Revival of oscillation from mean-field-induced death: Theory and experiment.

    PubMed

    Ghosh, Debarati; Banerjee, Tanmoy; Kurths, Jürgen

    2015-11-01

    The revival of oscillation and maintaining rhythmicity in a network of coupled oscillators offer an open challenge to researchers as the cessation of oscillation often leads to a fatal system degradation and an irrecoverable malfunctioning in many physical, biological, and physiological systems. Recently a general technique of restoration of rhythmicity in diffusively coupled networks of nonlinear oscillators has been proposed in Zou et al. [Nat. Commun. 6, 7709 (2015)], where it is shown that a proper feedback parameter that controls the rate of diffusion can effectively revive oscillation from an oscillation suppressed state. In this paper we show that the mean-field diffusive coupling, which can suppress oscillation even in a network of identical oscillators, can be modified in order to revoke the cessation of oscillation induced by it. Using a rigorous bifurcation analysis we show that, unlike other diffusive coupling schemes, here one has two control parameters, namely the density of the mean-field and the feedback parameter that can be controlled to revive oscillation from a death state. We demonstrate that an appropriate choice of density of the mean field is capable of inducing rhythmicity even in the presence of complete diffusion, which is a unique feature of this mean-field coupling that is not available in other coupling schemes. Finally, we report the experimental observation of revival of oscillation from the mean-field-induced oscillation suppression state that supports our theoretical results. PMID:26651763

  16. Giant low field magnetocaloric effect and field-induced metamagnetic transition in TmZn

    NASA Astrophysics Data System (ADS)

    Li, Lingwei; Yuan, Ye; Zhang, Yikun; Namiki, Takahiro; Nishimura, Katsuhiko; Pöttgen, Rainer; Zhou, Shengqiang

    2015-09-01

    The magnetic properties and the magnetocaloric effect (MCE) in TmZn have been studied by magnetization and heat capacity measurements. The TmZn compound exhibits a ferromagnetic state below a Curie temperature of TC = 8.4 K and processes a field-induced metamagnetic phase transition around and above TC. A giant reversible MCE was observed in TmZn. For a field change of 0-5 T, the maximum values of magnetic entropy change (-ΔSMmax) and adiabatic temperature change (ΔTadmax) are 26.9 J/kg K and 8.6 K, the corresponding values of relative cooling power and refrigerant capacity are 269 and 214 J/kg, respectively. Particularly, the values of -ΔSMmax reach 11.8 and 19.6 J/kg K for a low field change of 0-1 and 0-2 T, respectively. The present results indicate that TmZn could be a promising candidate for low temperature and low field magnetic refrigeration.

  17. Electric-field-induced Spontaneous Magnetization and Phase Transitions in Zigzag Boron Nitride Nanotubes

    PubMed Central

    Bai, Lang; Gu, Gangxu; Xiang, Gang; Zhang, Xi

    2015-01-01

    We demonstrate an alternative scheme for realizing spin polarizations in semiconductor nanostructures by an all-electric way. The electronic and magnetic properties of the model system, zigzag pristine boron nitride nanotubes (BNNTs), are investigated under a transverse electric field (E) through spin-polarized density functional theory calculations. As E increases, the band gap of BNNTs is reduced due to charge redistribution induced by the asymmetry of electrostatic potential energy, and BNNTs experience rich phase transitions, such as semiconductor-metal transition and nonmagnetic (NM) metal-ferromagnetic (FM) metal transitions. Electric-field-induced magnetization occurs when a sufficiently high density of states at the Fermi level in the vicinity of metal-insulator transition is reached due to the redistribution of electronic bands and charge transferring across the BNNTs. Further analysis show that the spontaneous magnetization is derived from the localized nature of the 2p states of B and N, and the ferromagnetic coupling is stabilized by Zener’s double-exchange mechanism. Our results may provide a viable way to realize spintronic devices for applications. PMID:26206393

  18. Surface mapping of field-induced piezoelectric strain at elevated temperature employing full-field interferometry.

    PubMed

    Stevenson, Tim; Quast, Tatjana; Bartl, Guido; Schmitz-Kempen, Thorsten; Weaver, Paul M

    2015-01-01

    Piezoelectric actuators and sensors are widely used for flow control valves, including diesel injectors, ultrasound generation, optical positioning, printing, pumps, and locks. Degradation and failure of material and electrical properties at high temperature typically limits these applications to operating temperatures below 200°C, based on the ubiquitous Pb(Zr,Ti)O3 ceramic. There are, however, many applications in sectors such as automotive, aerospace, energy and process control, and oil and gas, where the ability to operate at higher temperatures would open up new markets for piezoelectric actuation. Presented here is a review of recent progress and initial results toward a European effort to develop measurement techniques to characterize high-temperature materials. Full-field, multi-wavelength absolute length interferometry has, for the first time, been used to map the electric-field-induced piezoelectric strain across the surface of a PZT ceramic. The recorded variation as a function of temperature has been evaluated against a newly developed commercial single-beam system. Conventional interferometry allows measurement of the converse piezoelectric effect with high precision and resolution, but is often limited to a single point, average measurement and to limited sample environments because of optical aberrations in varying atmospheres. Here, the full-field technique allows the entire surface to be analyzed for strain and, in a bespoke sample chamber, for elevated temperatures. PMID:25585393

  19. Electric field induced Lyman-α emission of a hydrogen beam for electric field measurements

    SciTech Connect

    Chérigier-Kovacic, L. Doveil, F.; Ström, P.; Lejeune, A.

    2015-06-15

    Electric field induced Lyman-α emission is a new way of measuring weak electric fields in vacuum and in a plasma. It is based on the emission of Lyman-α radiation (121.6 nm) by a low-energy metastable H atom beam due to Stark-quenching of the 2s level induced by the field. In this paper, we describe the technique in detail. Test measurements have been performed in vacuum between two plates polarized at a controlled voltage. The intensity of emitted radiation, proportional to the square of the field modulus, has been recorded by a lock-in technique, which gives an excellent signal to noise ratio. These measurements provide an in situ calibration that can be used to obtain the absolute value of the electric field. A diagnostic of this type can help to address a long standing challenge in plasma physics, namely, the problem of measuring electric fields without disturbing the equilibrium of the system that is being studied.

  20. Background-free electric field-induced second harmonic generation with interdigitated combs of electrodes.

    PubMed

    Jašinskas, Vidmantas; Gedvilas, Mindaugas; Račiukaitis, Gediminas; Gulbinas, Vidmantas

    2016-06-15

    The electric field-induced second harmonic (EFISH) generation is a powerful tool for the investigation of optical nonlinearities, material polarization, internal electric fields, and other properties of photonic materials and devices. A conventional generation of the second harmonics (SH) in materials with the disturbed centrosymmetry causes a field-independent background to EFISH and limits its applications. Here we suggest and analyze the application of the interdigitated combs of electrodes for EFISH generation in thin films. Interdigitated electrodes form an optical transmission amplitude diffraction grating. Phase matching of the EFISH radiation creates unusual diffraction fringes with the zero intensity along the zeroth order direction and with the diffraction angles different from diffraction angles of incident fundamental laser radiation and its second harmonics. It enables a simple geometrical separation of the EFISH signal from a conventional SH background, simplifies the sample preparation, and provides additional experimental possibilities. We demonstrate applicability of the suggested technique for characterization of submicrometer thickness organic films of transparent and resonantly interacting polymers and of their mixtures. PMID:27304282

  1. Magnetic field-induced helical mode and topological transitions in a topological insulator nanoribbon

    NASA Astrophysics Data System (ADS)

    Jauregui, Luis A.; Pettes, Michael T.; Rokhinson, Leonid P.; Shi, Li; Chen, Yong P.

    2016-04-01

    The spin-helical Dirac fermion topological surface states in a topological insulator nanowire or nanoribbon promise novel topological devices and exotic physics such as Majorana fermions. Here, we report local and non-local transport measurements in Bi2Te3 topological insulator nanoribbons that exhibit quasi-ballistic transport over ∼2 μm. The conductance versus axial magnetic flux Φ exhibits Aharonov–Bohm oscillations with maxima occurring alternately at half-integer or integer flux quanta (Φ0 = h/e, where h is Planck's constant and e is the electron charge) depending periodically on the gate-tuned Fermi wavevector (kF) with period 2π/C (where C is the nanoribbon circumference). The conductance versus gate voltage also exhibits kF-periodic oscillations, anti-correlated between Φ = 0 and Φ0/2. These oscillations enable us to probe the Bi2Te3 band structure, and are consistent with the circumferentially quantized topological surface states forming a series of one-dimensional subbands, which undergo periodic magnetic field-induced topological transitions with the disappearance/appearance of the gapless Dirac point with a one-dimensional spin helical mode.

  2. Field-induced spin density wave and spiral phases in a layered antiferromagnet

    SciTech Connect

    Stone, Matthew B.; Lumsden, Mark D.; Garlea, Vasile O.; Grenier, B.; Ressouche, E.; Samulon, Eric C.; Fisher, Ian R.

    2015-07-28

    Here we determine the low-field ordered magnetic phases of the S=1 dimerized antiferromagnet Ba3Mn2O8 using single crystal neutron diffraction. We find that for magnetic fields between μ0H=8.80 T and 10.56 T applied along the $1\\bar{1}0$ direction the system exhibits spin density wave order with incommensurate wave vectors of type (η,η,ε). For μ0H > 10.56 T, the magnetic order changes to a spiral phase with incommensurate wave vectors only along the [hh0] direction. For both field induced ordered phases, the magnetic moments are lying in the plane perpendicular to the field direction. Finally, the nature of these two transitions is fundamentally different: the low-field transition is a second order transition to a spin-density wave ground state, while the one at higher field, toward the spiral phase, is of first order.

  3. Field-induced alignment of oxygen and nitrogen by intense femtosecond laser pulses.

    PubMed

    Huang, Juan; Wu, Chengyin; Xu, Nan; Liang, Qingqing; Wu, Zhifeng; Yang, Hong; Gong, Qihuang

    2006-08-31

    Field-induced alignment of O2 and N2 was experimentally studied with laser intensities varying from 10(13) to 10(15) W/cm2. When the laser intensity was below the ionization threshold for these molecules, the interaction between the induced dipole moment of molecules and the laser electric field aligned the molecules along the laser polarization direction. After extinction of the exciting laser, the transient alignment revived periodically. Thus macroscopic ensembles of highly aligned O2 and N2 molecules were obtained under field-free conditions. When the laser intensity exceeded the ionization threshold for these molecules, multielectron ionization and Coulomb explosion occurred. Using two linearly polarized laser pulses with crossed polarization, we demonstrated that the rising edge of the laser pulse aligned the molecules along the laser polarization direction prior to ionization, which resulted in strong anisotropic angular distributions of exploding fragments. These results suggest that the degree of alignment should be taken into account when qualitatively comparing the ion yield of these molecules with their companion atoms. PMID:16928105

  4. Field-induced spin density wave and spiral phases in a layered antiferromagnet

    DOE PAGESBeta

    Stone, Matthew B.; Lumsden, Mark D.; Garlea, Vasile O.; Grenier, B.; Ressouche, E.; Samulon, Eric C.; Fisher, Ian R.

    2015-07-28

    Here we determine the low-field ordered magnetic phases of the S=1 dimerized antiferromagnet Ba3Mn2O8 using single crystal neutron diffraction. We find that for magnetic fields between μ0H=8.80 T and 10.56 T applied along themore » $$1\\bar{1}0$$ direction the system exhibits spin density wave order with incommensurate wave vectors of type (η,η,ε). For μ0H > 10.56 T, the magnetic order changes to a spiral phase with incommensurate wave vectors only along the [hh0] direction. For both field induced ordered phases, the magnetic moments are lying in the plane perpendicular to the field direction. Finally, the nature of these two transitions is fundamentally different: the low-field transition is a second order transition to a spin-density wave ground state, while the one at higher field, toward the spiral phase, is of first order.« less

  5. Revival of oscillation from mean-field-induced death: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Ghosh, Debarati; Banerjee, Tanmoy; Kurths, Jürgen

    2015-11-01

    The revival of oscillation and maintaining rhythmicity in a network of coupled oscillators offer an open challenge to researchers as the cessation of oscillation often leads to a fatal system degradation and an irrecoverable malfunctioning in many physical, biological, and physiological systems. Recently a general technique of restoration of rhythmicity in diffusively coupled networks of nonlinear oscillators has been proposed in Zou et al. [Nat. Commun. 6, 7709 (2015), 10.1038/ncomms8709], where it is shown that a proper feedback parameter that controls the rate of diffusion can effectively revive oscillation from an oscillation suppressed state. In this paper we show that the mean-field diffusive coupling, which can suppress oscillation even in a network of identical oscillators, can be modified in order to revoke the cessation of oscillation induced by it. Using a rigorous bifurcation analysis we show that, unlike other diffusive coupling schemes, here one has two control parameters, namely the density of the mean-field and the feedback parameter that can be controlled to revive oscillation from a death state. We demonstrate that an appropriate choice of density of the mean field is capable of inducing rhythmicity even in the presence of complete diffusion, which is a unique feature of this mean-field coupling that is not available in other coupling schemes. Finally, we report the experimental observation of revival of oscillation from the mean-field-induced oscillation suppression state that supports our theoretical results.

  6. High Magnetic Field-Induced Birefringence in Lyotropic Chromonic Liquid Crystals

    NASA Astrophysics Data System (ADS)

    Ostapenko, T.; Nastishin, Yu.; Gleeson, J. T.; Sprunt, S. N.; Lavrentovich, O. D.; Collings, P. J.

    2009-03-01

    We studied the effect of magnetic-field induced birefringence of a 14% solution of disodium cromoglycate (DSCG) in water at temperatures above the nematic-isotropic coexistence region. According to Landau-deGennes mean field theory, we expect to find a linear relationship between the inverse of the induced birefringence, δn, and the quantity (T-T*), where T* is the stability limit of the isotropic phase. Using the 31 T resistive magnet at the National High Magnetic Field Laboratory, we observed that, as we increase the temperature above the coexistence region, we deviate from this linear dependence. Our data shows that δn goes to zero, whereas Landau-deGennes predicts that δn should decrease asymptotically. This may be due to the lack of isodesmic aggregate formation at a finite temperature above the coexistence region.Supported by NSF (DMR-0710544 and DMR-0606160). Work performed at NHMFL, supported by NSF cooperative agreements DMR-0084173, the State of Florida and the DOE.

  7. Spatiotemporal structure of intracranial electric fields induced by transcranial electric stimulation in humans and nonhuman primates.

    PubMed

    Opitz, Alexander; Falchier, Arnaud; Yan, Chao-Gan; Yeagle, Erin M; Linn, Gary S; Megevand, Pierre; Thielscher, Axel; Deborah A, Ross; Milham, Michael P; Mehta, Ashesh D; Schroeder, Charles E

    2016-01-01

    Transcranial electric stimulation (TES) is an emerging technique, developed to non-invasively modulate brain function. However, the spatiotemporal distribution of the intracranial electric fields induced by TES remains poorly understood. In particular, it is unclear how much current actually reaches the brain, and how it distributes across the brain. Lack of this basic information precludes a firm mechanistic understanding of TES effects. In this study we directly measure the spatial and temporal characteristics of the electric field generated by TES using stereotactic EEG (s-EEG) electrode arrays implanted in cebus monkeys and surgical epilepsy patients. We found a small frequency dependent decrease (10%) in magnitudes of TES induced potentials and negligible phase shifts over space. Electric field strengths were strongest in superficial brain regions with maximum values of about 0.5 mV/mm. Our results provide crucial information of the underlying biophysics in TES applications in humans and the optimization and design of TES stimulation protocols. In addition, our findings have broad implications concerning electric field propagation in non-invasive recording techniques such as EEG/MEG. PMID:27535462

  8. Spatiotemporal structure of intracranial electric fields induced by transcranial electric stimulation in humans and nonhuman primates

    PubMed Central

    Opitz, Alexander; Falchier, Arnaud; Yan, Chao-Gan; Yeagle, Erin M.; Linn, Gary S.; Megevand, Pierre; Thielscher, Axel; Deborah A., Ross; Milham, Michael P.; Mehta, Ashesh D.; Schroeder, Charles E.

    2016-01-01

    Transcranial electric stimulation (TES) is an emerging technique, developed to non-invasively modulate brain function. However, the spatiotemporal distribution of the intracranial electric fields induced by TES remains poorly understood. In particular, it is unclear how much current actually reaches the brain, and how it distributes across the brain. Lack of this basic information precludes a firm mechanistic understanding of TES effects. In this study we directly measure the spatial and temporal characteristics of the electric field generated by TES using stereotactic EEG (s-EEG) electrode arrays implanted in cebus monkeys and surgical epilepsy patients. We found a small frequency dependent decrease (10%) in magnitudes of TES induced potentials and negligible phase shifts over space. Electric field strengths were strongest in superficial brain regions with maximum values of about 0.5 mV/mm. Our results provide crucial information of the underlying biophysics in TES applications in humans and the optimization and design of TES stimulation protocols. In addition, our findings have broad implications concerning electric field propagation in non-invasive recording techniques such as EEG/MEG. PMID:27535462

  9. Electric field-induced superconducting transition of insulating FeSe thin film at 35 K

    NASA Astrophysics Data System (ADS)

    Hanzawa, Kota; Sato, Hikaru; Hiramatsu, Hidenori; Kamiya, Toshio; Hosono, Hideo

    2016-04-01

    It is thought that strong electron correlation in an insulating parent phase would enhance a critical temperature (Tc) of superconductivity in a doped phase via enhancement of the binding energy of a Cooper pair as known in high-Tc cuprates. To induce a superconductor transition in an insulating phase, injection of a high density of carriers is needed (e.g., by impurity doping). An electric double-layer transistor (EDLT) with an ionic liquid gate insulator enables such a field-induced transition to be investigated and is expected to result in a high Tc because it is free from deterioration in structure and carrier transport that are in general caused by conventional carrier doping (e.g., chemical substitution). Here, for insulating epitaxial thin films (∼10 nm thick) of FeSe, we report a high Tc of 35 K, which is 4× higher than that of bulk FeSe, using an EDLT under application of a gate bias of +5.5 V. Hall effect measurements under the gate bias suggest that highly accumulated electron carrier in the channel, whose area density is estimated to be 1.4 × 1015 cm-2 (the average volume density of 1.7 × 1021 cm-3), is the origin of the high-Tc superconductivity. This result demonstrates that EDLTs are useful tools to explore the ultimate Tc for insulating parent materials.

  10. Electric field-induced superconducting transition of insulating FeSe thin film at 35 K.

    PubMed

    Hanzawa, Kota; Sato, Hikaru; Hiramatsu, Hidenori; Kamiya, Toshio; Hosono, Hideo

    2016-04-12

    It is thought that strong electron correlation in an insulating parent phase would enhance a critical temperature (Tc) of superconductivity in a doped phase via enhancement of the binding energy of a Cooper pair as known in high-Tc cuprates. To induce a superconductor transition in an insulating phase, injection of a high density of carriers is needed (e.g., by impurity doping). An electric double-layer transistor (EDLT) with an ionic liquid gate insulator enables such a field-induced transition to be investigated and is expected to result in a high Tc because it is free from deterioration in structure and carrier transport that are in general caused by conventional carrier doping (e.g., chemical substitution). Here, for insulating epitaxial thin films (∼10 nm thick) of FeSe, we report a high Tc of 35 K, which is 4× higher than that of bulk FeSe, using an EDLT under application of a gate bias of +5.5 V. Hall effect measurements under the gate bias suggest that highly accumulated electron carrier in the channel, whose area density is estimated to be 1.4 × 10(15) cm(-2) (the average volume density of 1.7 × 10(21) cm(-3)), is the origin of the high-Tc superconductivity. This result demonstrates that EDLTs are useful tools to explore the ultimate Tc for insulating parent materials. PMID:27035956

  11. The evolution of the quasar continuum

    NASA Technical Reports Server (NTRS)

    Elvis, M.

    1992-01-01

    We now have in hand a large data base of Roentgen Satellite (ROSAT), optical, and IR complementary data. We are in the process of obtaining a large amount of the International Ultraviolet Explorer (IUE) data for the same quasar sample. For our complementary sample at high redshifts, where the UV was redshifted into the optical, we have just had approved large amounts of observing time to cover the quasar continuum in the near-IR using the new Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) array spectrographs. Ten micron, optical, and VLA radio, data also have approved time. An ISO US key program was approved to extend this work into the far-IR, and the launch of ASTRO-D (early in 1993) promises to extend it to higher energy X-rays.

  12. The Nuclear Three-Body Continuum

    NASA Astrophysics Data System (ADS)

    Brune, Carl R.

    2001-04-01

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

  13. Continuum Theory of Beta-Sheet Ribbons.

    NASA Astrophysics Data System (ADS)

    Ghafouri, Rouzbeh

    2005-03-01

    We present a continuum description for the β-sheet ribbons encountered in amyloid fibrils, allowing both stretching and bending of the ribbon in response to chiral twist. The theory leads to a non-linear variant of the Worm-Like Chain (WLC). At a critical value of the ratio of the bending and stretching moduli, the Foppl-von K'arm'an Number, we encounter a continuous buckling transition from a straight Helicoid to a Spiral Ribbon. Two of the three persistence lengths of the ribbon become very short at the transition point indicating strong thermal shape fluctuations. The transition becomes discontinuous if the ribbon width is treated as a free thermodynamic variable.

  14. The polarization of escaping terrestrial continuum radiation

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Calvert, W.; Huff, R. L.; Jones, D.; Sugiura, M.

    1988-01-01

    The polarization of an escaping terrestrial continuum radiation event that occurred on March 2, 1982, was determined using plasma wave measurements from the DE-1 spacecraft. The source of the radiation was determined to be located near the magnetic equator on the nightside of the earth at a radial distance of about 2.8-3.5 earth radii. Two meridional beams were detected, one directed north at an angle of about 20-30 deg with respect to the magnetic equator, and the other directed south at a comparable angle. Polarization measurements indicated that the radiation is right-hand polarized with respect to an outward directed E plane normal in the Northern Hemisphere and left-hand polarized in the Southern Hemisphere.

  15. Polymer quantum mechanics and its continuum limit

    SciTech Connect

    Corichi, Alejandro; Vukasinac, Tatjana; Zapata, Jose A.

    2007-08-15

    A rather nonstandard quantum representation of the canonical commutation relations of quantum mechanics systems, known as the polymer representation, has gained some attention in recent years, due to its possible relation with Planck scale physics. In particular, this approach has been followed in a symmetric sector of loop quantum gravity known as loop quantum cosmology. Here we explore different aspects of the relation between the ordinary Schroedinger theory and the polymer description. The paper has two parts. In the first one, we derive the polymer quantum mechanics starting from the ordinary Schroedinger theory and show that the polymer description arises as an appropriate limit. In the second part we consider the continuum limit of this theory, namely, the reverse process in which one starts from the discrete theory and tries to recover back the ordinary Schroedinger quantum mechanics. We consider several examples of interest, including the harmonic oscillator, the free particle, and a simple cosmological model.

  16. Precompound nucleon angular distributions in the continuum

    SciTech Connect

    Blann, M.; Scobel, W.; Plechaty, E.

    1985-08-01

    Angular distributions for nucleon induced reactions (incident energies 14 to 90 MeV) leading to precompound nucleon emission in the continuum (emitted particle energies 9-70 MeV) are calculated based on nucleon-nucleon scattering kinematics for an incident nucleon on a Fermi gas. Analytic expressions due to Kikuchi and Kawai are used for the single scattering kernel. The geometry dependent hybrid model is used to generate the differential cross sections for first, second, etc. order scattering, these weightings being used to fold the single scattering kernel. Results are found to reproduce all experimental angular distributions quite well at angles in the 20/sup 0/ to 90/sup 0/ range. Ad-hoc modifications to approximate quantal effects and Coulomb deflections are explored, but the results do not seem to offer a consistent means of reproducing back angle yields, and give generally poorer results at very forward angles.

  17. Continuum ionization transition probabilities of atomic oxygen

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  18. Continuum modeling of cooperative traffic flow dynamics

    NASA Astrophysics Data System (ADS)

    Ngoduy, D.; Hoogendoorn, S. P.; Liu, R.

    2009-07-01

    This paper presents a continuum approach to model the dynamics of cooperative traffic flow. The cooperation is defined in our model in a way that the equipped vehicle can issue and receive a warning massage when there is downstream congestion. Upon receiving the warning massage, the (up-stream) equipped vehicle will adapt the current desired speed to the speed at the congested area in order to avoid sharp deceleration when approaching the congestion. To model the dynamics of such cooperative systems, a multi-class gas-kinetic theory is extended to capture the adaptation of the desired speed of the equipped vehicle to the speed at the downstream congested traffic. Numerical simulations are carried out to show the influence of the penetration rate of the equipped vehicles on traffic flow stability and capacity in a freeway.

  19. Human Mobility in a Continuum Approach

    PubMed Central

    Simini, Filippo; Maritan, Amos; Néda, Zoltán

    2013-01-01

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

  20. Continuum mechanics, stresses, currents and electrodynamics.

    PubMed

    Segev, Reuven

    2016-04-28

    The Eulerian approach to continuum mechanics does not make use of a body manifold. Rather, all fields considered are defined on the space, or the space-time, manifolds. Sections of some vector bundle represent generalized velocities which need not be associated with the motion of material points. Using the theories of de Rham currents and generalized sections of vector bundles, we formulate a weak theory of forces and stresses represented by vector-valued currents. Considering generalized velocities represented by differential forms and interpreting such a form as a generalized potential field, we present a weak formulation of pre-metric, p-form electrodynamics as a natural example of the foregoing theory. Finally, it is shown that the assumptions leading to p-form electrodynamics may be replaced by the condition that the force functional is continuous with respect to the flat topology of forms. PMID:27002071

  1. Floquet bound states in the continuum

    PubMed Central

    Longhi, Stefano; Valle, Giuseppe Della

    2013-01-01

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

  2. Near infrared Kerr effect and description of field-induced phase transitions in polymer-stabilized blue phase liquid crystals

    NASA Astrophysics Data System (ADS)

    Atorf, B.; Rasouli, H.; Nordendorf, G.; Wilkes, D.; Kitzerow, H.

    2016-02-01

    Studies of the influence of an electric field E on the effective refractive index of a polymer-stabilized blue phase in the near infrared spectral range reveal a considerable field-induced birefringence. At moderate voltages, the birefringence increases linearly with the square of the field strength as expected for the electro-optic Kerr effect, with an effective Kerr constant of K ≈ 6.3 - 6.9 × 10-10 m V-2. However, for E > ≈7.3 V/μm, the slope of the field-induced birefringence versus E2 increases abruptly, before saturation is reached at E > ≈8.5 V/μm. Based on previous observations on blue phases in the visible wavelength range, the discontinuous change can be attributed to a field-induced phase transition. A modification of the extended Kerr model introduced by Wu and coworkers is suggested to take this additional effect into account. In addition to the promising properties of blue phases for improved liquid crystal displays, the observed field-induced birefringence in the infrared region opens interesting perspectives for telecommunication and other non-display applications.

  3. A Threshold Continuum for Aeolian Sand Transport

    NASA Astrophysics Data System (ADS)

    Swann, C.; Ewing, R. C.; Sherman, D. J.

    2015-12-01

    The threshold of motion for aeolian sand transport marks the initial entrainment of sand particles by the force of the wind. This is typically defined and modeled as a singular wind speed for a given grain size and is based on field and laboratory experimental data. However, the definition of threshold varies significantly between these empirical models, largely because the definition is based on visual-observations of initial grain movement. For example, in his seminal experiments, Bagnold defined threshold of motion when he observed that 100% of the bed was in motion. Others have used 50% and lesser values. Differences in threshold models, in turn, result is large errors in predicting the fluxes associated with sand and dust transport. Here we use a wind tunnel and novel sediment trap to capture the fractions of sand in creep, reptation and saltation at Earth and Mars pressures and show that the threshold of motion for aeolian sand transport is best defined as a continuum in which grains progress through stages defined by the proportion of grains in creep and saltation. We propose the use of scale dependent thresholds modeled by distinct probability distribution functions that differentiate the threshold based on micro to macro scale applications. For example, a geologic timescale application corresponds to a threshold when 100% of the bed in motion whereas a sub-second application corresponds to a threshold when a single particle is set in motion. We provide quantitative measurements (number and mode of particle movement) corresponding to visual observations, percent of bed in motion and degrees of transport intermittency for Earth and Mars. Understanding transport as a continuum provides a basis for revaluating sand transport thresholds on Earth, Mars and Titan.

  4. Reconciling lattice and continuum models for polymers at interfaces.

    PubMed

    Fleer, G J; Skvortsov, A M

    2012-04-01

    and strong repulsion, for any chain length, and for any solvency. For adsorption the volume filling dominates. As a result c now reaches a lower limit c ≈ -0.5 (depending slightly on solvency). This limit follows immediately from the condition of a fully occupied train layer. Comparison with numerical SCF calculations corroborates that our analytical result is a good approximation. We suggest some simple methods to determine the interaction parameter (either c or Δχ(s)) from experiments. The relation Δχ(s)(c) provides a quantitative connection between continuum and lattice theories, and enables the use of analytical continuum results to describe the adsorption (and stretching) of lattice chains of any chain length. For example, a fully analytical treatment of mechanical desorption of a polymer chain (including the temperature dependence and the phase transitions) is now feasible. PMID:22482580

  5. Continuum beliefs about psychotic symptoms are a valid, unidimensional construct: Construction and validation of a revised continuum beliefs questionnaire.

    PubMed

    Schlier, Björn; Scheunemann, Jakob; Lincoln, Tania M

    2016-07-30

    Growing evidence supports a continuum model of psychosis, with mild psychotic symptoms being frequently experienced by the general population. Moreover, believing in the continuum model correlates with less stigmatization of schizophrenia. This study explores whether continuum beliefs are a valid construct and develops a continuum beliefs scale. First, expert-generated items were reduced to a candidate scale (study 1, n=95). One-dimensionality was tested using confirmatory factor analysis (study 2, n=363). Convergent validity was tested with a previous continuum beliefs scale, essentialist beliefs, and stigmatization (study 2), while self-reported psychotic experiences (i.e. frequency and conviction) served to test discriminant validity (study 3, n=229). A nine item questionnaire that assesses continuum beliefs about schizophrenia symptoms showed acceptable to good psychometric values, high correlations with a previous continuum beliefs scale and small correlations with essentialist beliefs, stereotypes, and desired social distance. No correlations with psychotic experiences were found. Thus, continuum beliefs can be considered a valid construct. The construed CBQ-R asks about symptoms rather than the abstract category "schizophrenia", which may increase understandability of the scale. Validation confirms previous studies and highlights the difference between continuum beliefs and personal psychotic experiences. PMID:27175910

  6. Functional continuity: did field-induced oriented aperiodic constraints at Life's origin aid its sequence-based evolution?

    NASA Astrophysics Data System (ADS)

    Mitra-Delmotte, G.; Mitra, A. N.

    2014-04-01

    A non-biological analog undergoing Darwinian-like evolution could have enhanced the probability of many crucial independent bottom-up emergent steps, engendered within its premises, and smoothen the inanimate-animate transition. Now, the higher-level environment-mutable DNA sequences influence the lower-level pattern of oriented templates (enzymes, lipid membranes, RNA) in the organized cell matrix and hence their associated substrate-dynamics; note how templates are akin to local fields, kinetically constraining reactant orientations. Since the lowerlevel is likely the more primitive of the two (rather than Cairns-Smith's "readily available" rigid clay crystal sequence-based replicators as a memory-like basis for slowly mutating predecessor-patterns enroute to complex RNA-based Darwinian evolution), a gradual thermodynamic-to-kinetic transition in an isotropic medium, is proposed as driven by some order-parameter --via "available" field-responsive dipolar colloid networks, as apart from bio-organics, mineral colloids also can display liquid crystal (LC) phases (see [1]). An access to solid-like orientational order in a fluid matrix suggests how aperiodic patterns can be influenced and sustained (a la homeostasis) via external inhomogeneous fields (e.g. magnetic rocks); this renders these cooperative networks with potential as confining host-media, whose environment-sensitivity can not only influence their sterically-coupled guest-substrates but also their network properties (the latter can enable 'functions' like spontaneous transport under non-equilibrium suggesting a natural basis for their selection by the environment). In turn LC systems could have been preceded by even simpler anisotropic fluid hosts, viz., external field-induced mineral magnetic nanoparticle (MNP) aggregates. Indeed, the capacity of an MNP to couple its magnetic and rotational d.o.f.s suggests how an environment-sensitive field-influenced network of interacting dipolar colloids close to

  7. Continuum Thinking and the Contexts of Personal Information Management

    ERIC Educational Resources Information Center

    Huvila, Isto; Eriksen, Jon; Häusner, Eva-Maria; Jansson, Ina-Maria

    2014-01-01

    Introduction: Recent personal information management literature has underlined the significance of the contextuality of personal information and its use. The present article discusses the applicability of the records continuum model and its generalisation, continuum thinking, as a theoretical framework for explicating the overlap and evolution of…

  8. Continuum of Counseling Goals: A Framework for Differentiating Counseling Strategies.

    ERIC Educational Resources Information Center

    Bruce, Paul

    1984-01-01

    Presents counseling goals in a developmental continuum similar in concept to Maslow's hierarchy of needs. Discusses ego development goals, socialization goals, developmental goals, self-esteem goals, and self-realization goals and describes characteristics and implications of the continuum. (JAC)

  9. 48 CFR 15.101 - Best value continuum.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Best value continuum. 15.101 Section 15.101 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACTING... Best value continuum. An agency can obtain best value in negotiated acquisitions by using any one or...

  10. 48 CFR 15.101 - Best value continuum.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 1 2013-10-01 2013-10-01 false Best value continuum. 15.101 Section 15.101 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACTING... Best value continuum. An agency can obtain best value in negotiated acquisitions by using any one or...

  11. 48 CFR 15.101 - Best value continuum.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 1 2012-10-01 2012-10-01 false Best value continuum. 15.101 Section 15.101 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACTING... Best value continuum. An agency can obtain best value in negotiated acquisitions by using any one or...

  12. 48 CFR 15.101 - Best value continuum.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 1 2011-10-01 2011-10-01 false Best value continuum. 15.101 Section 15.101 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACTING... Best value continuum. An agency can obtain best value in negotiated acquisitions by using any one or...

  13. 48 CFR 15.101 - Best value continuum.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 1 2014-10-01 2014-10-01 false Best value continuum. 15.101 Section 15.101 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACTING... Best value continuum. An agency can obtain best value in negotiated acquisitions by using any one or...

  14. Teaching Continuum Mechanics in a Mechanical Engineering Program

    ERIC Educational Resources Information Center

    Liu, Yucheng

    2011-01-01

    This paper introduces a graduate course, continuum mechanics, which is designed for and taught to graduate students in a Mechanical Engineering (ME) program. The significance of continuum mechanics in engineering education is demonstrated and the course structure is described. Methods used in teaching this course such as topics, class…

  15. Curriculum Building for the Continuum in Social Welfare Education.

    ERIC Educational Resources Information Center

    Austin, Michael J., Ed.; And Others

    During 1970 Florida's University and Community College Systems held a workshop to discuss the idea of a curriculum continuum that would begin at the community college level and extend through the upper levels of graduate work. It was acknowledged that any continuum involving more than 1 level of education should include flexible opportunities for…

  16. Study of flow fields induced by surface dielectric barrier discharge actuator in low-pressure air

    SciTech Connect

    Che, Xueke E-mail: st@mail.iee.ac.cn; Nie, Wansheng; Tian, Xihui; Hou, Zhiyong; He, Haobo; Zhou, Penghui; Zhou, Siyin; Yang, Chao; Shao, Tao E-mail: st@mail.iee.ac.cn

    2014-04-15

    Surface dielectric barrier discharge (SDBD) is a promising method for a flow control. Flow fields induced by a SDBD actuator driven by the ac voltage in static air at low pressures varying from 1.0 to 27.7 kPa are measured by the particle image velocimetry method. The influence of the applied ac voltage frequency and magnitude on the induced flow fields is studied. The results show that three different classes of flow fields (wall jet flow field, complex flow field, and vortex-shape flow field) can be induced by the SDBD actuator in the low-pressure air. Among them, the wall jet flow field is the same as the tangential jet at atmospheric pressure, which is, together with the vertical jet, the complex flow field. The vortex-shape flow field is composed of one vertical jet which points towards the wall and two opposite tangential jets. The complex and the vortex-shape flow fields can be transformed to the wall jet flow field when the applied ac voltage frequency and magnitude are changed. It is found that the discharge power consumption increases initially, decreases, and then increases again at the same applied ac voltage magnitude when the air pressure decreases. The tangential velocity of the wall jet flow field increases when the air pressure decreases. It is however opposite for the complex flow field. The variation of the applied ac voltage frequency influences differently three different flow fields. When the applied ac voltage magnitude increases at the same applied ac voltage frequency, the maximal jet velocity increases, while the power efficiency increases only initially and then decreases again. The discharge power shows either linear or exponential dependences on the applied ac voltage magnitude.

  17. Field-induced quantum criticality in low-dimensional Heisenberg spin systems

    NASA Astrophysics Data System (ADS)

    Azzouz, Mohamed

    2006-11-01

    We study the quantum critical behavior in the antiferromagnetic Heisenberg chain and two-leg Heisenberg ladder resulting from the application of an external magnetic field. In each of these systems a finite-temperature crossover line between two different ferromagnetic phases ends with a quantum critical point at zero temperature. Using the bond-mean-field theory, we calculate the field dependence of the magnetization and the mean-field spin bond parameters in both systems. For the Heisenberg chain, we recover the existing exact results and show in addition that the saturation of the zero-temperature magnetization at the field hc=2J is accompanied by a quantum phase transition, where the bond parameter vanishes. Here J is the exchange coupling constant along the chain. For the two-leg ladder, we also recover the known results, like the two magnetization plateaus, and show that at the upper critical field, which corresponds to the appearance of the saturation magnetization plateau, the chain and rung spin bond parameters vanish. The identification of the order parameters that govern the field-induced quantum criticality in the systems we study here constitutes an original contribution. Because no long-range order, which breaks symmetry, characterizes the bond order, the latter could be a proposal for the so-called hidden order. We calculate analytically the bond parameters in both systems as functions of the field in the low- and high-field limits at zero temperature. At nonzero temperatures, the calculation of the magnetization and bond parameters is carried out by solving the mean-field equations numerically.

  18. Fast deswelling of nanocomposite polymer hydrogels via magnetic field-induced heating for emerging FO desalination.

    PubMed

    Razmjou, Amir; Barati, Mohammad Reza; Simon, George P; Suzuki, Kiyonori; Wang, Huanting

    2013-06-18

    Freshwater shortage is one of the most pressing global issues. Forward osmosis (FO) desalination technology is emerging for freshwater production from saline water, which is potentially more energy-efficient than the current reverse osmosis process. However, the lack of a suitable draw solute is the major hurdle for commercial implementation of the FO desalination technology. We have previously reported that thermoresponsive hydrogels can be used as the draw agent for a FO process, and this new hydrogel-driven FO process holds promise for further development for practical application. In the present work, magnetic field-induced heating is explored for the purpose of developing a more effective way to recover water from swollen hydrogel draw agents. The composite hydrogel particles are prepared by copolymerization of sodium acrylate and N-isopropylacrylamide in the presence of magnetic nanoparticles (γ-Fe2O3, <50 nm). The results indicate that the magnetic heating is an effective and rapid method for dewatering of hydrogels by generating the heat more uniformly throughout the draw agent particles, and thus, a dense skin layer commonly formed via conventional heating from the outside of the particle is minimized. The FO dewatering performance is affected by the loading of magnetic nanoparticles and magnetic field intensity. Significantly enhanced liquid water recovery (53%) is achieved under magnetic heating, as opposed to only around 7% liquid water recovery obtained via convection heating. Our study shows that the magnetic heating is an attractive alternative stimulus for the extraction of highly desirable liquid water from the draw agent in the polymer hydrogel-driven forward osmosis process. PMID:23663180

  19. Magnetic-field-induced DNA strand breaks in brain cells of the rat.

    PubMed Central

    Lai, Henry; Singh, Narendra P

    2004-01-01

    In previous research, we found that rats acutely (2 hr) exposed to a 60-Hz sinusoidal magnetic field at intensities of 0.1-0.5 millitesla (mT) showed increases in DNA single- and double-strand breaks in their brain cells. Further research showed that these effects could be blocked by pretreating the rats with the free radical scavengers melatonin and N-tert-butyl-alpha-phenylnitrone, suggesting the involvement of free radicals. In the present study, effects of magnetic field exposure on brain cell DNA in the rat were further investigated. Exposure to a 60-Hz magnetic field at 0.01 mT for 24 hr caused a significant increase in DNA single- and double-strand breaks. Prolonging the exposure to 48 hr caused a larger increase. This indicates that the effect is cumulative. In addition, treatment with Trolox (a vitamin E analog) or 7-nitroindazole (a nitric oxide synthase inhibitor) blocked magnetic-field-induced DNA strand breaks. These data further support a role of free radicals on the effects of magnetic fields. Treatment with the iron chelator deferiprone also blocked the effects of magnetic fields on brain cell DNA, suggesting the involvement of iron. Acute magnetic field exposure increased apoptosis and necrosis of brain cells in the rat. We hypothesize that exposure to a 60-Hz magnetic field initiates an iron-mediated process (e.g., the Fenton reaction) that increases free radical formation in brain cells, leading to DNA strand breaks and cell death. This hypothesis could have an important implication for the possible health effects associated with exposure to extremely low-frequency magnetic fields in the public and occupational environments. PMID:15121512

  20. Preparation and properties of alumina composites modified by electric field-induced alignment of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhu, Yue-Feng; Shi, Lei; Zhang, Chan; Yang, Xi-Zhi; Liang, Ji

    2007-11-01

    Catalytic chemical vapor deposition (CVD) grown multi-walled carbon nanotubes (MWNTs) are treated with HF and deionized water and are then placed into alumina ceramics for improvement of both electrical conductivity and mechanical properties. In particular, an alternating current (ac) electric field is applied during the coagulation of the alumina slurries to induce the formation of aligned MWNT networks in the alumina matrix. The coagulated alumina matrix composite bases filled with 2 wt. % ac electric field-induced aligned MWNTs, are then sintered by hot pressing. The electrical conductivities of the prepared composites in directions both parallel and perpendicular to the MWNTs alignment, reach values of 6.2×10-2 S m-1 and 6.8×10-9 S m-1, respectively, compared with that of 4.5×10-15 S m-1 for pristine alumina ceramics. The fracture toughness and flexing strengths of the prepared composites in the two directions are 4.66±0.66 MPa m0.5, 390±70 MPa, and 3.65±0.46 MPa m0.5, 191±5 MPa, respectively, compared with 3.78±0.66 MPa m0.5 and 302±50 MPa for pristine alumina, 4.09±0.15 MPa m0.5 and 334±60 MPa for alumina filled with 2 wt. % MWNTs prepared without the effect of an electric field, respectively. The results indicate that the electric field leads to anisotropic behaviour. The properties of the composites along the direction of the MWNTs alignment are much improved with the addition of a small amount of CVD grown MWNTs.

  1. Research on adaptive temperature control in sound field induced by self-focused concave spherical transducer.

    PubMed

    Hu, Jiwen; Qian, Shengyou; Ding, Yajun

    2010-05-01

    Temperature control of hyperthermia treatments is generally implemented with multipoint feedback system comprised of phased-array transducer, which is complicated and high cost. Our simulations to the acoustic field induced by a self-focused concave spherical transducer (0.5MHz, 9cm aperture width, 8.0cm focal length) show that the distribution of temperature can keep the same "cigar shape" in the focal region during ultrasound insonation. Based on the characteristic of the temperature change, a two-dimensional model of a "cigar shape" tumor is designed and tested through numerical simulation. One single-point on the border of the "cigar shape" tumor is selected as the control target and is controlled at the temperature of 43 degrees C by using a self-tuning regulator (STR). Considering the nonlinear effects of biological medium, an accurate state-space model obtained via the finite Fourier integral transformation to the bioheat equation is presented and used for calculating temperature. Computer simulations were performed with the perfusion rates of 2.0kg/(m(3)s) and 4.5kg/(m(3)s) to the different targets, it was found that the temperatures on the border of the "cigar shape" tumor can achieve the desired temperature of 43 degrees C by control of one single-point. A larger perfusion rate requires a higher power output to obtain the same temperature elevation under the same insonation time and needs a higher cost for compensating the energy loss carried away by blood flow after steady state. The power output increases with the controlled region while achieving the same temperature at the same time. Especially, there is no overshoot during temperature elevation and no oscillation after steady state. The simulation results demonstrate that the proposed approach may offers a way for obtaining a single-point, low-cost hyperthermia system. PMID:20156630

  2. AC electric field induced dielectrophoretic assembly behavior of gold nanoparticles in a wide frequency range

    NASA Astrophysics Data System (ADS)

    Liu, Weiyu; Wang, Chunhui; Ding, Haitao; Shao, Jinyou; Ding, Yucheng

    2016-05-01

    In this work, we focus on frequency-dependence of pearl chain formations (PCF) of gold nanoparticles driven by AC dielectrophoresis (DEP), especially in a low field-frequency range, where induced double-layer charging effect at ideally polarizable surfaces on particle DEP behavior and surrounding liquid motion need not be negligible. As field frequency varies, grown features of DEP assembly structures ranging from low-frequency non-bridged gap to high-frequency single gold nanoparticle-made nanowires bridging the electrodes are demonstrated experimentally. Specifically, at 10 kHz, a kind of novel channel-like structure with parallel opposing banks is formed at the center of interelectrode gap. In stark contrast, at 1 MHz, thin PCF with diameter of 100 nm is created along the shortest distance of the isolation spacing. Moreover, a particular conductive path of nanoparticle chains is produced at 1 MHz in a DEP device embedded with multiple floating electrodes. A theoretical framework taking into account field-induced double-layer polarization at both the particle/electrolyte and electrode/electrolyte interface is developed to correlate these experimental observations with induced-charge electrokinetic (ICEK) phenomenon. And a RC circuit model is helpful in accounting for the formation of this particular non-bridged channel-like structure induced by a low-frequency AC voltage. As compared to thin PCF formed at high field frequency that effectively short circuits the electrode pair, though it is difficult for complete PCF bridging to occur at low frequency, the non-bridged conducting microstructure has potential to further miniaturize the size of electrode gap fabricated by standard micromachining process and may find useful application in biochemical sensing.

  3. Detection of nonthermal continuum radiation in Saturn's magnetosphere

    SciTech Connect

    Kuth, W.S.; Scarf, F.L.; Sullivan, J.D.; Gurnett, D.A.

    1982-08-01

    A detailed analysis of high resolution wideband data from the Voyager 1 and 2 plasma wave receivers has revealed the presence of heretofore undiscovered nonthermal continuum radiation trapped within the Saturnian magnetosphere. The discovery of Saturnian trapped continuum radiation fills a disturbing void in the Saturnian radio spectrum. On the basis of observations at both the Earth and Jupiter it was expected that continuum radiation should be a pervasive signature of planetary magnetospheres in general. Special processing of the Voyager 1 plasma wave data at Saturn has now confirmed the existence of weak emissions that have a spectrum characteristic of trapped continuum radiation. Similar radiation was also detected by Voyager 2; however, in this case it is not certain that Saturn was the only source. Considerable evidence exists which suggests that Saturn may have been immersed in the Jovian tail during the Voyager 2 encounter, so that Jupiter may provide an additional source of the continuum radiation detected by Voyager 2.

  4. An Optimization-based Atomistic-to-Continuum Coupling Method

    DOE PAGESBeta

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

    2014-08-21

    In this paper, we present a new optimization-based method for atomistic-to-continuum (AtC) coupling. The main idea is to cast the latter as a constrained optimization problem with virtual Dirichlet controls on the interfaces between the atomistic and continuum subdomains. The optimization objective is to minimize the error between the atomistic and continuum solutions on the overlap between the two subdomains, while the atomistic and continuum force balance equations provide the constraints. Separation, rather then blending of the atomistic and continuum problems, and their subsequent use as constraints in the optimization problem distinguishes our approach from the existing AtC formulations. Finally,more » we present and analyze the method in the context of a one-dimensional chain of atoms modeled using a linearized two-body potential with next-nearest neighbor interactions.« less

  5. An Optimization-based Atomistic-to-Continuum Coupling Method

    SciTech Connect

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

    2014-08-21

    In this paper, we present a new optimization-based method for atomistic-to-continuum (AtC) coupling. The main idea is to cast the latter as a constrained optimization problem with virtual Dirichlet controls on the interfaces between the atomistic and continuum subdomains. The optimization objective is to minimize the error between the atomistic and continuum solutions on the overlap between the two subdomains, while the atomistic and continuum force balance equations provide the constraints. Separation, rather then blending of the atomistic and continuum problems, and their subsequent use as constraints in the optimization problem distinguishes our approach from the existing AtC formulations. Finally, we present and analyze the method in the context of a one-dimensional chain of atoms modeled using a linearized two-body potential with next-nearest neighbor interactions.

  6. Continuum and molecular-dynamics simulation of nanodroplet collisions

    NASA Astrophysics Data System (ADS)

    Bardia, Raunak; Liang, Zhi; Keblinski, Pawel; Trujillo, Mario F.

    2016-05-01

    The extent to which the continuum treatment holds in binary droplet collisions is examined in the present work by using a continuum-based implicit surface capturing strategy (volume-of-fluid coupled to Navier-Stokes) and a molecular dynamics methodology. The droplet pairs are arranged in a head-on-collision configuration with an initial separation distance of 5.3 nm and a velocity of 3 ms-1. The size of droplets ranges from 10-50 nm. Inspecting the results, the collision process can be described as consisting of two periods: a preimpact phase that ends with the initial contact of both droplets, and a postimpact phase characterized by the merging, deformation, and coalescence of the droplets. The largest difference between the continuum and molecular dynamics (MD) predictions is observed in the preimpact period, where the continuum-based viscous and pressure drag forces significantly overestimate the MD predictions. Due to large value of Knudsen number in the gas (Kngas=1.972 ), this behavior is expected. Besides the differences between continuum and MD, it is also observed that the continuum simulations do not converge for the set of grid sizes considered. This is shown to be directly related to the initial velocity profile and the minute size of the nanodroplets. For instance, for micrometer-size droplets, this numerical sensitivity is not an issue. During the postimpact period, both MD and continuum-based simulations are strikingly similar, with only a moderate difference in the peak kinetic energy recorded during the collision process. With values for the Knudsen number in the liquid (Knliquid=0.01 for D =36 nm ) much closer to the continuum regime, this behavior is expected. The 50 nm droplet case is sufficiently large to be predicted reasonably well with the continuum treatment. However, for droplets smaller than approximately 36 nm, the departure from continuum behavior becomes noticeably pronounced, and becomes drastically different for the 10 nm droplets.

  7. An ALMA continuum survey of circumstellar disks in the upper Scorpius OB association

    SciTech Connect

    Carpenter, John M.; Ricci, Luca; Isella, Andrea

    2014-05-20

    We present ALMA 880 μm continuum observations of 20 K- and M-type stars in the Upper Scorpius OB association (Upper Sco) that are surrounded by protoplanetary disks. These data are used to measure the dust content in disks around low-mass stars (0.1-1.6 M {sub ☉}) at a stellar age of 5-11 Myr. Thirteen sources were detected in the 880 μm dust continuum at ≥3σ with inferred dust masses between 0.3 and 52 M {sub ⊕}. The dust masses tend to be higher around the more massive stars, but the significance is marginal in that the probability of no correlation is p ≈ 0.03. The evolution in the dust content in disks was assessed by comparing the Upper Sco observations with published continuum measurements of disks around ∼1-2 Myr stars in the Class II stage in the Taurus molecular cloud. While the dust masses in the Upper Sco disks are on average lower than in Taurus, any difference in the dust mass distributions is significant at less than 3σ. For stellar masses between 0.49 M {sub ☉} and 1.6 M {sub ☉}, the mean dust mass in disks is lower in Upper Sco relative to Taurus by Δlog M {sub dust} = 0.44 ± 0.26.

  8. Longitudinal Changes in Physical Habitat and Macroinvertebrate Assemblages Along a Neotropical Stream Continuum

    NASA Astrophysics Data System (ADS)

    Colon-Gaud, C.; Whiles, M. R.

    2005-05-01

    Information on the structure and function of upland Neotropical streams is lacking compared to many other regions. We examined habitat characteristics and macroinvertebrate assemblages along an 8-km stretch of a stream originating on the continental divide in central Panama in order to examine patterns along a stream continuum. Wetted width and discharge ranged from 1 m and 18 L/s, respectively in the uppermost headwaters to 12 m and 1,580 L/s, respectively at the lowest reach examined. Percent substrate composition showed a decrease in fine particle sizes from upper headwater reaches (38%) to the lowest reach (10%). A total of 61 macroinvertebrate taxa were identified along the continuum, with more taxa present in lower reaches (45) compared to headwaters (28), but responses of individual groups varied. Trichoptera, Ephemeroptera, and Diptera richness increased from headwaters to the lowest site, whereas Hemiptera and Coleoptera richness decreased along the gradient. Collector-gatherers and predators were the dominant functional groups (~70% of total abundance) and changed little across sites. Shredder abundance was highest in headwaters (15% of total), while scrapers (20%) and collector/filterers (11%) peaked in the lower reaches. These patterns suggest that upland streams in this region follow basic tenets of the River Continuum Concept.

  9. Diagnostic Reasoning across the Medical Education Continuum

    PubMed Central

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

    2014-01-01

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

  10. Optical continuum generation on a silicon chip

    NASA Astrophysics Data System (ADS)

    Jalali, Bahram; Boyraz, Ozdal; Koonath, Prakash; Raghunathan, Varun; Indukuri, Tejaswi; Dimitropoulos, Dimitri

    2005-08-01

    Although the Raman effect is nearly two orders of magnitude stronger than the electronic Kerr nonlinearity in silicon, under pulsed operation regime where the pulse width is shorter than the phonon response time, Raman effect is suppressed and Kerr nonlinearity dominates. Continuum generation, made possible by the non-resonant Kerr nonlinearity, offers a technologically and economically appealing path to WDM communication at the inter-chip or intra-chip levels. We have studied this phenomenon experimentally and theoretically. Experimentally, a 2 fold spectral broadening is obtained by launching ~4ps optical pulses with 2.2GW/cm2 peak power into a conventional silicon waveguide. Theoretical calculations, that include the effect of two-photon-absorption, free carrier absorption and refractive index change indicate that up to >30 times spectral broadening is achievable in an optimized device. The broadening is due to self phase modulation and saturates due to two photon absorption. Additionally, we find that free carrier dynamics also contributes to the spectral broadening and cause the overall spectrum to be asymmetric with respect to the pump wavelength.

  11. The Continuum of Pharmacist Prescriptive Authority.

    PubMed

    Adams, Alex J; Weaver, Krystalyn K

    2016-09-01

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

  12. Continuum source tungsten coil atomic fluorescence spectrometry.

    PubMed

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

    2011-04-01

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

  13. Compact continuum brain model for human electroencephalogram

    NASA Astrophysics Data System (ADS)

    Kim, J. W.; Shin, H.-B.; Robinson, P. A.

    2007-12-01

    A low-dimensional, compact brain model has recently been developed based on physiologically based mean-field continuum formulation of electric activity of the brain. The essential feature of the new compact model is a second order time-delayed differential equation that has physiologically plausible terms, such as rapid corticocortical feedback and delayed feedback via extracortical pathways. Due to its compact form, the model facilitates insight into complex brain dynamics via standard linear and nonlinear techniques. The model successfully reproduces many features of previous models and experiments. For example, experimentally observed typical rhythms of electroencephalogram (EEG) signals are reproduced in a physiologically plausible parameter region. In the nonlinear regime, onsets of seizures, which often develop into limit cycles, are illustrated by modulating model parameters. It is also shown that a hysteresis can occur when the system has multiple attractors. As a further illustration of this approach, power spectra of the model are fitted to those of sleep EEGs of two subjects (one with apnea, the other with narcolepsy). The model parameters obtained from the fittings show good matches with previous literature. Our results suggest that the compact model can provide a theoretical basis for analyzing complex EEG signals.

  14. Detection of radio continuum emission from Procyon

    NASA Technical Reports Server (NTRS)

    Drake, Stephen A.; Simon, Theodore; Brown, Alexander

    1993-01-01

    We have detected the F5 IV-V star Procyon as a weak and variable 3.6 cm radio continuum source using the VLA. The inferred radio luminosity is similar to, though some-what higher than, the X-band luminosity of the active and flaring sun. The 33 micro-Jy flux density level at which we detected Procyon on four of five occasions is close to the 36 micro-Jy radio flux density expected from a model in which the radio emission consists of two components: optically thick 'stellar disk' emission with a 3.6 cm brightness temperature of 20,000 K that is 50 percent larger than the solar value, and optically thin coronal emission with an emission measure the same as that indicated by Einstein and EXOSAT X-ray flux measurements in 1981 and 1983. The maximum mass-loss rate of a warm stellar wind is less than 2 x 10 exp -11 solar mass/yr. An elevated flux density of 115 micro-Jy observed on a single occasion provides circumstantial evidence for the existence of highly localized magnetic fields on the surface of Procyon.

  15. Controllable infrared continuum source for multiphoton imaging

    NASA Astrophysics Data System (ADS)

    de Mauro, C.; Alfieri, D.; Arrigoni, M.; Armstrong, D.; Pavone, F. S.

    2010-02-01

    We report on multiphoton imaging of biological samples performed with continuum infrared source generated in photonic crystal fibers (PCFs). We studied the spectra generated in PCFs with dispersion profiles designed to maximize the power density in the 700-1000 nm region, where the two-photon absorption cross sections of the most common dyes lie. Pumping in normal dispersion region, with <140 femtosecond pulses delivered by a tunable Ti:Sa laser (Chameleon Ultra II by Coherent Inc.), results in a limitation of nonlinear broadening up to a mean power density above 2 mW/nm. Axial and lateral resolution obtained with a scanning multiphoton system has been measureed to be near the theoretical limit. The possibility of simultaneous two-photon excitation of different dyes in the same sample and high image resolution are demonstrated at tens of microns in depth. Signal-to-noise ratio and general performances are found to be comparable with those of a single wavelength system, used for comparison.

  16. Modeling continuum of epithelial mesenchymal transition plasticity.

    PubMed

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

    2016-02-01

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

  17. Second law violations, continuum mechanics, and permeability

    NASA Astrophysics Data System (ADS)

    Ostoja-Starzewski, Martin

    2016-03-01

    The violations of the second law are relevant as the length and/or time scales become very small. The second law then needs to be replaced by the fluctuation theorem and mathematically, the irreversible entropy is a submartingale. First, we discuss the consequences of these results for the axioms of continuum mechanics, arguing in favor of a framework relying on stochastic functionals of energy and entropy. We next determine a Lyapunov function for diffusion-type problems governed by stochastic rather than deterministic functionals of internal energy and entropy, where the random field coefficients of diffusion are not required to satisfy the positive definiteness everywhere. Next, a formulation of micropolar fluid mechanics is developed, accounting for the lack of symmetry of stress tensor on molecular scales. This framework is then applied to employed to show that spontaneous random fluctuations of the microrotation field will arise in Couette—and Poiseuille-type flows in the absence of random (turbulence-like) fluctuations of the classical velocity field. Finally, while the permeability is classically modeled by the Darcy law or its modifications, besides considering the violations of the second law, one also needs to account for the spatial randomness of the channel network, implying a modification of the hierarchy of scale-dependent bounds on the macroscopic property of the network.

  18. Identity of Particles and Continuum Hypothesis

    NASA Astrophysics Data System (ADS)

    Berezin, Alexander A.

    2001-04-01

    Why all electrons are the same? Unlike other objects, particles and atoms (same isotopes) are forbidden to have individuality or personal history (or reveal their hidden variables, even if they do have them). Or at least, what we commonly call physics so far was unable to disprove particle's sameness (Berezin and Nakhmanson, Physics Essays, 1990). Consider two opposing hypotheses: (A) particles are indeed absolutely same, or (B) they do have individuality, but it is beyond our capacity to demonstrate. This dilemma sounds akin to undecidability of Continuum Hypothesis of existence (or not) of intermediate cardinalities between integers and reals (P.Cohen). Both yes and no of it are true. Thus, (alleged) sameness of electrons and atoms may be a physical translation (embodiment) of this fundamental Goedelian undecidability. Experiments unlikely to help: even if we find that all electrons are same within 30 decimal digits, could their masses (or charges) still differ in100-th digit? Within (B) personalized informationally rich (infinitely rich?) digital tails (starting at, say, 100-th decimal) may carry individual record of each particle history. Within (A) parameters (m, q) are indeed exactly same in all digits and their sameness is based on some inherent (meta)physical principle akin to Platonism or Eddington-type numerology.

  19. Continuum regularization of quantum field theory

    SciTech Connect

    Bern, Z.

    1986-04-01

    Possible nonperturbative continuum regularization schemes for quantum field theory are discussed which are based upon the Langevin equation of Parisi and Wu. Breit, Gupta and Zaks made the first proposal for new gauge invariant nonperturbative regularization. The scheme is based on smearing in the ''fifth-time'' of the Langevin equation. An analysis of their stochastic regularization scheme for the case of scalar electrodynamics with the standard covariant gauge fixing is given. Their scheme is shown to preserve the masslessness of the photon and the tensor structure of the photon vacuum polarization at the one-loop level. Although stochastic regularization is viable in one-loop electrodynamics, two difficulties arise which, in general, ruins the scheme. One problem is that the superficial quadratic divergences force a bottomless action for the noise. Another difficulty is that stochastic regularization by fifth-time smearing is incompatible with Zwanziger's gauge fixing, which is the only known nonperturbaive covariant gauge fixing for nonabelian gauge theories. Finally, a successful covariant derivative scheme is discussed which avoids the difficulties encountered with the earlier stochastic regularization by fifth-time smearing. For QCD the regularized formulation is manifestly Lorentz invariant, gauge invariant, ghost free and finite to all orders. A vanishing gluon mass is explicitly verified at one loop. The method is designed to respect relevant symmetries, and is expected to provide suitable regularization for any theory of interest. Hopefully, the scheme will lend itself to nonperturbative analysis. 44 refs., 16 figs.

  20. Selective spectral detection of continuum terahertz radiation

    NASA Astrophysics Data System (ADS)

    Kaufmann, P.; Marcon, R.; Marun, A.; Kudaka, A. S.; Bortolucci, E.; Zakia, M. B.; Diniz, J. A.; Cassiano, M. M.; Pereyra, P.; Godoy, R.; Timofeevsky, A. V.; Nikolaev, V. A.; Pereira Alves da Silva, A. M.; Fernandes, L. O. T.

    2010-07-01

    The knowledge of THz continuum spectra is essential to investigate the emission mechanisms by high energy particle acceleration processes. Technical challenges appear for obtaining selective spectral sensing in the far infrared range to diagnose radiation produced by solar flare burst emissions measured from space as well as radiation produced by high energy electrons in laboratory accelerators. Efforts are been carried out intended for the development of solar flare high cadence radiometers at two THz frequencies to operate outside the terrestrial atmosphere (i.e. at 3 and 7 THz). One essential requirement is the efficient suppression of radiation in the visible and near infrared. Experimental setups have been assembled for testing (a) THz transmission of "low-pass" filters: rough surface mirrors; membranes Zitex G110G and TydexBlack; (b) a fabricated 2.4 THz resonant grid band-pass filter transmission response for polarization and angle of incidence; (c) radiation response from distinct detectors: adapted commercial microbolometer array using HRFZ-Si window, pyroelectric module and Golay cell; qualitative detection of solar radiation at a sub-THz frequency has been tested with a microbolometer array placed at the focus of the 1.5 m reflector for submillimeter waves (SST) at El Leoncito, Argentina Andes.

  1. Edge gyrokinetic theory and continuum simulations

    NASA Astrophysics Data System (ADS)

    Xu, X. Q.; Xiong, Z.; Dorr, M. R.; Hittinger, J. A.; Bodi, K.; Candy, J.; Cohen, B. I.; Cohen, R. H.; Colella, P.; Kerbel, G. D.; Krasheninnikov, S.; Nevins, W. M.; Qin, H.; Rognlien, T. D.; Snyder, P. B.; Umansky, M. V.

    2007-08-01

    The following results are presented from the development and application of TEMPEST, a fully nonlinear (full-f) five-dimensional (3d2v) gyrokinetic continuum edge-plasma code. (1) As a test of the interaction of collisions and parallel streaming, TEMPEST is compared with published analytic and numerical results for endloss of particles confined by combined electrostatic and magnetic wells. Good agreement is found over a wide range of collisionality, confining potential and mirror ratio, and the required velocity space resolution is modest. (2) In a large-aspect-ratio circular geometry, excellent agreement is found for a neoclassical equilibrium with parallel ion flow in the banana regime with zero temperature gradient and radial electric field. (3) The four-dimensional (2d2v) version of the code produces the first self-consistent simulation results of collisionless damping of geodesic acoustic modes and zonal flow (Rosenbluth-Hinton residual) with Boltzmann electrons using a full-f code. The electric field is also found to agree with the standard neoclassical expression for steep density and ion temperature gradients in the plateau regime. In divertor geometry, it is found that the endloss of particles and energy induces parallel flow stronger than the core neoclassical predictions in the SOL.

  2. Continuum Edge Gyrokinetic Theory and Simulations

    SciTech Connect

    Xu, X Q; Xiong, Z; Dorr, M R; Hittinger, J A; Bodi, K; Candy, J; Cohen, B I; Cohen, R H; Colella, P; Kerbel, G D; Krasheninnikov, S; Nevins, W M; Qin, H; Rognlien, T D; Snyder, P B; Umansky, M V

    2007-01-09

    The following results are presented from the development and application of TEMPEST, a fully nonlinear (full-f) five dimensional (3d2v) gyrokinetic continuum edge-plasma code. (1) As a test of the interaction of collisions and parallel streaming, TEMPEST is compared with published analytic and numerical results for endloss of particles confined by combined electrostatic and magnetic wells. Good agreement is found over a wide range of collisionality, confining potential, and mirror ratio; and the required velocity space resolution is modest. (2) In a large-aspect-ratio circular geometry, excellent agreement is found for a neoclassical equilibrium with parallel ion flow in the banana regime with zero temperature gradient and radial electric field. (3) The four-dimensional (2d2v) version of the code produces the first self-consistent simulation results of collisionless damping of geodesic acoustic modes and zonal flow (Rosenbluth-Hinton residual) with Boltzmann electrons using a full-f code. The electric field is also found to agree with the standard neoclassical expression for steep density and ion temperature gradients in the banana regime. In divertor geometry, it is found that the endloss of particles and energy induces parallel flow stronger than the core neoclassical predictions in the SOL. (5) Our 5D gyrokinetic formulation yields a set of nonlinear electrostatic gyrokinetic equations that are for both neoclassical and turbulence simulations.

  3. Magnetic interactions, weak ferromagnetism, and field-induced transitions in Nd2NiO4

    NASA Astrophysics Data System (ADS)

    Batlle, X.; Obradors, X.; Martnez, B.

    1992-02-01

    The magnetic properties of stoichiometric Nd2NiO4 have been investigated by means of dc- and ac-magnetic-susceptibility and isothermal-magnetization measurements. Five different magnetic phase transitions have been identified and characterized. A collinear antiferromagnetic ordering of Ni2+ magnetic moments exists between TN1~=320 K and Tc1~=130 K (gx mode) where an orthorhombic-to-tetragonal (Bmab to P42/ncm) structural phase transition occurs. In this temperature range, the Nd3+ ions behave as a paramagnet being polarized by the effect of an internal magnetic field associated with the Ni-Nd antiferromagnetic superexchange interaction. A weak ferromagnetic component appears below 130 K, which is consistent with the gxcyfz and gx+cyfz magnetic modes for Ni2+ proposed from a neutron-powder-diffraction experiment. An additional out-of-plane component of the internal magnetic field on the Nd3+ ions develops with this structural phase transition and strongly polarizes these ions. Two additional transitions are observed at Tc2~=68 K (very prominent) and Tc3~=45 K (very smooth), which are characterized by a sudden increase in the internal magnetic field acting on the Nd ions. This internal magnetic field is evaluated and an antiparallel ordering between the Ni and Nd weak ferromagnetic spin components is inferred. A field-induced transition has been identified. A peak on both the differential susceptibility and the real part of the ac susceptibility at TN2~=11 K marks a long-range antiferromagnetic ordering of the Nd3+ ions. The out-of-plane component of the Ni2+ magnetic moments is attributed to the antisymmetric interaction DNi-Ni, which turns out to be quite important (DNi-Ni~=-16.0 meV) as compared to La2NiO4 and La2CuO4, probably because of a greater tilting angle of the octahedra. Finally, the magnetocrystalline anisotropy associated with Nd ions is found to be high below 20 K.

  4. Quantum Hall effect in field-induced spin density wave systems

    NASA Astrophysics Data System (ADS)

    Tevosyan, Kahren

    The research work described in this thesis is motivated by recent theoretical and experimental studies of the Quantum Hall Effect (QHE) in the quasi-one-dimensional conductors such as organic metals of the (TMTSF)sb2X family. These materials consist of weakly coupled parallel conducting chains that lie in the same plane. They exhibit very interesting behavior in the presence of a strong magnetic field which is perpendicular to the plane. At low temperatures a series of phase transitions from the metallic state to spin density wave states occur with increasing magnetic field. The latter are called the Field-Induced Spin Density Wave (FISDW) states. Within each FISDW phase, the value of the Hall resistance is quantized, signalling the presence of the Quantum Hall Effect. In contrast with the conventional QHE in isotropic two-dimensional systems, finite-width Landau bands appear naturally in the disorder-free (TMTSF)sb2X materials. In fact, the theory of the QHE in quasi-one-dimensiona1 organic conductors has so far been developed without any consideration of the effect of the disorder required to broaden Landau bands in isotropic systems. Here we address for the first time the localization properties of the quantum states in FISDW Landau bands. We employ the Thouless approach which uses the sensitivity of the eigenvalues to the choice of boundary conditions to study localization. Our results show that the localization properties of the states are very different from those of the conventional QHE systems. We find that the Thouless numbers do not decrease exponentially with the system size, indicating that states are not localized on the scales we can study. Another aspect of the dissertation deals with the edge state picture of the QHE which states that gapless excitations localized at the system edge are present whenever the quantum Hall effect occurs. We examine these properties of edge states for the FISDW systems by performing computer simulations to model the

  5. Magnetic-field-induced quadrupole coupling in the nuclear magnetic resonance of noble-gas atoms and molecules

    SciTech Connect

    Manninen, Pekka; Vaara, Juha; Pyykkoe, Pekka

    2004-10-01

    An analytic response theory formulation for the leading-order magnetic field-induced and field-dependent quadrupole splitting in nuclear magnetic resonance spectra is presented and demonstrated with first-principles calculations for {sup 21}Ne, {sup 36}Ar, and {sup 83}Kr in noble gas atoms. The case of molecules was studied for {sup 33}S in the sulphur hexafluoride molecule, as well as for {sup 47/49}Ti, {sup 91}Zr, and {sup 177,179}Hf in group(IV) tetrahalides. According to our calculations, the hitherto experimentally unknown field-induced quadrupole splitting in molecules rises to 10{sup 2} Hz for {sup 177,179}Hf nuclei in HfF{sub 4} and 10{sup 1} Hz for {sup 47/49}Ti in TiCl{sub 4}, and is hence of observable magnitude.

  6. Chiral-index resolved length mapping of carbon nanotubes in solution using electric-field induced differential absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Wenshan; Hennrich, Frank; Flavel, Benjamin S.; Kappes, Manfred M.; Krupke, Ralph

    2016-09-01

    The length of single-walled carbon nanotubes (SWCNTs) is an important metric for the integration of SWCNTs into devices and for the performance of SWCNT-based electronic or optoelectronic applications. In this work we propose a rather simple method based on electric-field induced differential absorption spectroscopy to measure the chiral-index-resolved average length of SWCNTs in dispersions. The method takes advantage of the electric-field induced length-dependent dipole moment of nanotubes and has been verified and calibrated by atomic force microscopy. This method not only provides a low cost, in situ approach for length measurements of SWCNTs in dispersion, but due to the sensitivity of the method to the SWCNT chiral index, the chiral index dependent average length of fractions obtained by chromatographic sorting can also be derived. Also, the determination of the chiral-index resolved length distribution seems to be possible using this method.

  7. Field-induced magnetic instability and quantum criticality in the antiferromagnet CeCu2Ge2

    PubMed Central

    Liu, Yi; Xie, Donghua; Wang, Xiaoying; Zhu, Kangwei; Yang, Ruilong

    2016-01-01

    The magnetic quantum criticality in strongly correlated electron systems has been considered to be closely related with the occurrence of unconventional superconductivity. Control parameters such as magnetic field, pressure or chemical doping are frequently used to externally tune the quantum phase transition for a deeper understanding. Here we report the research of a field-induced quantum phase transition using conventional bulk physical property measurements in the archetypal antiferromagnet CeCu2Ge2, which becomes superconductive under a pressure of about 10 GPa with Tc ~ 0.64 K. We offer strong evidence that short-range dynamic correlations start appearing above a magnetic field of about 5 T. Our demonstrations of the magnetic instability and the field-induced quantum phase transition are crucial for the quantum criticality, which may open a new route in experimental investigations of the quantum phase transition in heavy-fermion systems. PMID:26758347

  8. Field-induced magnetic instability and quantum criticality in the antiferromagnet CeCu2Ge2.

    PubMed

    Liu, Yi; Xie, Donghua; Wang, Xiaoying; Zhu, Kangwei; Yang, Ruilong

    2016-01-01

    The magnetic quantum criticality in strongly correlated electron systems has been considered to be closely related with the occurrence of unconventional superconductivity. Control parameters such as magnetic field, pressure or chemical doping are frequently used to externally tune the quantum phase transition for a deeper understanding. Here we report the research of a field-induced quantum phase transition using conventional bulk physical property measurements in the archetypal antiferromagnet CeCu2Ge2, which becomes superconductive under a pressure of about 10 GPa with Tc ~ 0.64 K. We offer strong evidence that short-range dynamic correlations start appearing above a magnetic field of about 5 T. Our demonstrations of the magnetic instability and the field-induced quantum phase transition are crucial for the quantum criticality, which may open a new route in experimental investigations of the quantum phase transition in heavy-fermion systems. PMID:26758347

  9. Shear dependence of field-induced contributions to the viscosity of magnetic fluids at low shear rates

    NASA Astrophysics Data System (ADS)

    Odenbach, S.; Störk, H.

    1998-03-01

    Viscoelastic properties of ferrofluids are an upcoming field of scientific interest, since the magnetic control of the related fluid behavior would give rise to new applications as well as for new possibilities in basic research concerning viscoelasticity. We have constructed a specialized rheometer for the investigation of fluids under the influence of magnetic fields, to examine such effects in stable suspensions of magnetic particles. In particular we will report the change of field-induced increase of viscosity due to variation of the shear rate applied to the fluid. The results show that the available theoretical approach, namely the concept of rotational viscosity, is not valid for the description of the field-induced increase of viscosity in concentrated fluids at low shear rates.

  10. Local Electrical Imaging of Tetragonal Domains and Field-Induced Ferroelectric Twin Walls in Conducting SrTiO3

    NASA Astrophysics Data System (ADS)

    Ma, H. J. Harsan; Scharinger, S.; Zeng, S. W.; Kohlberger, D.; Lange, M.; Stöhr, A.; Wang, X. Renshaw; Venkatesan, T.; Kleiner, R.; Scott, J. F.; Coey, J. M. D.; Koelle, D.; Ariando

    2016-06-01

    We demonstrate electrical mapping of tetragonal domains and electric field-induced twin walls in SrTiO3 as a function of temperature and gate bias utilizing the conducting LaAlO3/SrTiO3 interface and low-temperature scanning electron microscopy. Conducting twin walls appear below 105 K, and new twin patterns are observed after thermal cycling through the transition or on electric field gating. The nature of the twin walls is confirmed by calculating their intersection angles for different substrate orientations. Numerous walls formed when a large side- or back-gate voltage is applied are identified as field-induced ferroelectric twin walls in the paraelectric tetragonal matrix. The walls persist after switching off the electric field and on thermal cycling below 105 K. These observations point to a new type of ferroelectric functionality in SrTiO3 , which could be exploited together with magnetism and superconductivity in a multifunctional context.

  11. Field-induced magnetic instability and quantum criticality in the antiferromagnet CeCu2Ge2

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Xie, Donghua; Wang, Xiaoying; Zhu, Kangwei; Yang, Ruilong

    2016-01-01

    The magnetic quantum criticality in strongly correlated electron systems has been considered to be closely related with the occurrence of unconventional superconductivity. Control parameters such as magnetic field, pressure or chemical doping are frequently used to externally tune the quantum phase transition for a deeper understanding. Here we report the research of a field-induced quantum phase transition using conventional bulk physical property measurements in the archetypal antiferromagnet CeCu2Ge2, which becomes superconductive under a pressure of about 10 GPa with Tc ~ 0.64 K. We offer strong evidence that short-range dynamic correlations start appearing above a magnetic field of about 5 T. Our demonstrations of the magnetic instability and the field-induced quantum phase transition are crucial for the quantum criticality, which may open a new route in experimental investigations of the quantum phase transition in heavy-fermion systems.

  12. Hybrid continuum-atomistic approach to model electrokinetics in nanofluidics.

    PubMed

    Amani, Ehsan; Movahed, Saeid

    2016-06-01

    In this study, for the first time, a hybrid continuum-atomistic based model is proposed for electrokinetics, electroosmosis and electrophoresis, through nanochannels. Although continuum based methods are accurate enough to model fluid flow and electric potential in nanofluidics (in dimensions larger than 4 nm), ionic concentration is too low in nanochannels for the continuum assumption to be valid. On the other hand, the non-continuum based approaches are too time-consuming and therefore is limited to simple geometries, in practice. Here, to propose an efficient hybrid continuum-atomistic method of modelling the electrokinetics in nanochannels; the fluid flow and electric potential are computed based on continuum hypothesis coupled with an atomistic Lagrangian approach for the ionic transport. The results of the model are compared to and validated by the results of the molecular dynamics technique for a couple of case studies. Then, the influences of bulk ionic concentration, external electric field, size of nanochannel, and surface electric charge on the electrokinetic flow and ionic mass transfer are investigated, carefully. The hybrid continuum-atomistic method is a promising approach to model more complicated geometries and investigate more details of the electrokinetics in nanofluidics. PMID:27155300

  13. Equivalent-Continuum Modeling With Application to Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Gates, Thomas S.; Nicholson, Lee M.; Wise, Kristopher E.

    2002-01-01

    A method has been proposed for developing structure-property relationships of nano-structured materials. This method serves as a link between computational chemistry and solid mechanics by substituting discrete molecular structures with equivalent-continuum models. It has been shown that this substitution may be accomplished by equating the vibrational potential energy of a nano-structured material with the strain energy of representative truss and continuum models. As important examples with direct application to the development and characterization of single-walled carbon nanotubes and the design of nanotube-based devices, the modeling technique has been applied to determine the effective-continuum geometry and bending rigidity of a graphene sheet. A representative volume element of the chemical structure of graphene has been substituted with equivalent-truss and equivalent continuum models. As a result, an effective thickness of the continuum model has been determined. This effective thickness has been shown to be significantly larger than the interatomic spacing of graphite. The effective thickness has been shown to be significantly larger than the inter-planar spacing of graphite. The effective bending rigidity of the equivalent-continuum model of a graphene sheet was determined by equating the vibrational potential energy of the molecular model of a graphene sheet subjected to cylindrical bending with the strain energy of an equivalent continuum plate subjected to cylindrical bending.

  14. A Population of Dark Clouds Detected in Radio Continuum Images

    NASA Astrophysics Data System (ADS)

    Yusef-Zadeh, Farhad

    2013-01-01

    Using the VLA and GBT, radio continuum images of the inner Galaxy reveal the presence of numerous dark features. These dark features coincide with dense molecular and dust clouds. Unlike infrared dark clouds or extinction clouds at optical wavelengths, these features which we call ``radio dark clouds'' are produced by a deficiency in radio continuum emission from molecular clouds that are embedded in a bath of UV radiation field or synchrotron emitting cosmic ray particles. The contribution of the continuum emission along different pathlengths results in dark features that trace embedded molecular clouds. The new technique of identifying cold clouds can place constraints on the depth and the strength of diffuse magnetic field of molecular clouds. We present several examples of radio dark clouds and demonstrate an anti-correlation between the distributions of radio continuum and molecular line and dust emission. The level at which the continuum flux is suppressed in these sources suggests that the depth of the molecular cloud is similar to the size of the continuum emission within a factor of two. These examples suggest that radio continuum survey images can be powerful probes of interacting molecular clouds with massive stars and supernova remnants in the Galaxy as well as in the nuclei of active galaxies.

  15. 77 FR 23491 - Notice of Submission of Proposed Information Collection to OMB; Continuum of Care Homeless...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-19

    ... URBAN DEVELOPMENT Notice of Submission of Proposed Information Collection to OMB; Continuum of Care Homeless Assistance Grant Application--Continuum of Care Registration AGENCY: Office of the Chief... reporting burden associated with registration requirements that Continuum of Care Homeless Assistance...

  16. 77 FR 44653 - Continuum of Care Homeless Assistance Grant Application-Technical Submission

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-30

    ... URBAN DEVELOPMENT Continuum of Care Homeless Assistance Grant Application-- Technical Submission AGENCY... the original Continuum of Care Homeless Assistance Grant Application. DATES: Comments Due Date: August... lists the following information: Title of Proposal: Continuum of Care Homeless Assistance...

  17. 77 FR 24214 - Notice of Proposed Information Collection for Public Comment: Continuum of Care Homeless...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-23

    ... URBAN DEVELOPMENT Notice of Proposed Information Collection for Public Comment: Continuum of Care... following information: Title of Proposal: Continuum of Care Homeless Assistance--Technical Submission... technical information not contained in the original Continuum of Care Homeless Assistance Grant...

  18. Effect of residual strain in Fe-based amorphous alloys on field induced magnetic anisotropy and domain structure

    NASA Astrophysics Data System (ADS)

    Azuma, Daichi; Hasegawa, Ryusuke; Saito, Shin; Takahashi, Migaku

    2013-05-01

    Field induced magnetic anisotropy in two Fe-based amorphous alloys with different saturation induction levels (1.56 T and 1.64 T) was investigated by varying magnetic field strength and annealing temperature and domain images were taken on these samples. Residual strain was evaluated by measuring coercivities of the materials after stress-relief annealing. These results are discussed, clarifying the difference between the two Fe-based amorphous alloys.

  19. The electric field induced in the human body when exposed to electromagnetic fields at 1-30 MHz on shipboard.

    PubMed

    King, R W

    1999-06-01

    The electric field induced in the body of a man standing on the metal deck of a ship near a vertical antenna is determined analytically. Typical antennas for radio communication in the 1-30 MHz band are described and their near fields are calculated. The current induced in the man is determined by solving the relevant integral equation. Explicit formulas are obtained for the total axial current and the associated current densities and electric fields. PMID:10356881

  20. Electrostimulation of the magnetoplastic effect in LiF crystals by an "internal" electric field induced during indentation

    NASA Astrophysics Data System (ADS)

    Galustashvili, M. V.; Driaev, D. G.; Akopov, F. Kh.; Tsakadze, S. D.

    2013-08-01

    Indented LiF crystals demonstrate a change in the length of the dislocation rosette rays during their exposure to jointly acting dc magnetic and electric fields. It is shown that magnetic field with induction B = 1 T causes the electrostimulation or electrosuppression depending on the magnitude and direction of the external electric field with respect to the "internal" electric field induced by the charge transfer due to dislocations moving during the indentation.

  1. Magnetic field induced controllable self-assembly of maghemite nanocrystals: From 3D arrays to 1D nanochains

    NASA Astrophysics Data System (ADS)

    Tang, Yan; Chen, Qianwang; Chen, Rongsheng

    2015-08-01

    A hydrothermal process has been used to synthesize walnut-like maghemite superstructures which can be further self-assembled in a controllable manner into ordered three-dimensional (3D) architectures and one-dimensional (1D) nanochains in the presence of different external magnetic field. The assembly behavior of the maghemite nanoparticles isclosely related to the van der Waals interactions and external-field-induced magnetic dipole interactions. The magnetic properties of these nanostructures are also investigated.

  2. The Continuum and Dynamics of Northern Hemisphere Teleconnection Patterns.

    NASA Astrophysics Data System (ADS)

    Franzke, Christian; Feldstein, Steven B.

    2005-09-01

    This study presents an alternative interpretation for Northern Hemisphere teleconnection patterns. Rather than comprising several different recurrent regimes, this study suggests that there is a continuum of teleconnection patterns. This interpretation indicates either that 1) all members of the continuum can be expressed in terms of a linear combination of a small number of real physical modes that correspond to basis functions or 2) that most low-frequency patterns within the continuum are real physical patterns, each having its own spatial structure and frequency of occurrence.Daily NCEP-NCAR reanalysis data are used that cover the boreal winters of 1958-97. A set of nonorthogonal basis functions that span the continuum is derived. The leading basis functions correspond to well-known patterns such as the Pacific-North American teleconnection and North Atlantic Oscillation. Evidence for the continuum perspective is based on the finding that 1) most members of the continuum tend to have similar variance and autocorrelation time scales and 2) that members of the continuum show dynamical characteristics that are intermediate between those of the surrounding basis functions. The latter finding is obtained by examining the streamfunction tendency equation both for the basis functions and some members of the continuum.The streamfunction tendency equation analysis suggests that North Pacific patterns (basis functions and continuum) are primarily driven by their interaction with the climatological stationary eddies and that North Atlantic patterns are primarily driven by transient eddy vorticity fluxes. The decay mechanism for all patterns is similar, being due to the impact of low-frequency (period greater than 10 days) transient eddies and horizontal divergence. Analysis with outgoing longwave radiation shows that tropical convection is found to play a much greater role in exciting North Pacific patterns. A plausible explanation for these differences between the North

  3. Large magnetoresistance in LaBi: origin of field-induced resistivity upturn and plateau in compensated semimetals

    NASA Astrophysics Data System (ADS)

    Sun, Shanshan; Wang, Qi; Guo, Peng-Jie; Liu, Kai; Lei, Hechang

    2016-08-01

    The discovery of non-magnetic extreme magnetoresistance (XMR) materials has induced great interest because the XMR phenomenon challenges our understanding of how a magnetic field can alter electron transport in semimetals. Among XMR materials, the LaSb shows XMR and field-induced exotic behaviors but it seems to lack the essentials for these properties. Here, we study the magnetotransport properties and electronic structure of LaBi, isostructural to LaSb. LaBi exhibits large MR as in LaSb, which can be ascribed to the nearly compensated electron and hole with rather high mobilities. More importantly, our analysis suggests that the XMR as well as field-induced resistivity upturn and plateau observed in LaSb and LaBi can be well explained by the two-band model with the compensation situation. We present the critical conditions leading to these field-induced properties. It will contribute to the understanding of the XMR phenomenon and explore novel XMR materials.

  4. Field induced fluctuations in percolation in granular-heterogeneous La-Ag-Mn-O/ MnO

    NASA Astrophysics Data System (ADS)

    Zhang, Ning

    2005-03-01

    Several materials in the granular form, such as transition metals and manganese perovskites, show a giant magnetoresistance (GMR) that is attributed to field induced percolation effects [1]. We discuss here the observation of GMR in the solid solution La1-xAgxMnO3 (x = 0.05 - 0.50), possibly due to magnetic field induced fluctuation in percolation (MFP). Samples with x in steps of 0.05 were fabricated by the sol-gel method. We found Ag disassociation and run-off when the sample sintering temperature exceeded 800^o, resulting in a composite of La-Ag-Mn-O and manganese oxide. Analysis of x=0.35, for example, revealed a composite composition of (La0.926Ag0.074MnO3)0.698(MnO2)0..302. Studies on such samples showed GMR that could be attributed to field-induced enhancement in percolation [1]. [1] Ning Zhang, Weiping Ding, and Wei Zhong et al., Phys Rev B 56, 8139 (1997). -Work supported by the National Science Foundation (DMR-0302254)

  5. Influence of Interfacial Energy on Electric-Field-Induced Sphere-to-Cylinder Transition in Block Copolymer Thin Films

    SciTech Connect

    Wang, J.; Chen, W; Russell, T

    2008-01-01

    The effect of the interfacial energy on the electric-field-induced sphere-to-cylinder (S-to-C) transition in polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) copolymer thin films was studied as a function of the difference in the interfacial interactions of the PS and PMMA blocks with the substrate, d. It was found that the interfacial energies altered both the critical electric field strength and the time scales of kinetics. A very strong preferential interfacial interaction suppressed the electric-field-induced S-to-C transition even though such a transition occurred on a neutralized surface where the interfacial interactions were balanced. For a moderate interfacial interaction, the S-to-C transition can be induced by an applied electric field, but the time scale of the morphology change is much longer. Furthermore, the formation of ionic complexes in the BCP was found to enhance the electric-field-induced S-to-C transition even on a native Si substrate without any surface modification, providing a simple route to generate ordered arrays of high-aspect-ratio cylinders oriented normal to a film surface.

  6. Thermodynamics of the magnetic-field-induced "normal" state in an underdoped high Tc superconductor

    NASA Astrophysics Data System (ADS)

    Riggs, Scott Chandler

    High magnetic fields are used to kill superconductivity and probe what happens to system when it cannot reach the ideal ground state, i.e. what is the normal-state ground state? Early work in High-Tc, where the application of magnetic field destroyed the zero resistance state and recovered a resistivity value that connected continuously with the zero field curve, lead people to believe this magnetic-field-induced-state had fully driven the system normal, revealing the true underlying ground state, without any vestige of superconductivity. Many experiments done in this region of phase space have results interpreted as coming from the low energy ground state excitations. With the emergence of ultra-clean crystals in a unique family of hole doped high-Tc superconductors, YBa2Cu3O 7-delta, YBCO, a new and highly unexpected phenomena of quantum oscillations were discovered, and they followed the standard Liftshitz-Kosevich (LK) theory for a normal metal. The results suddenly made the problem of high-T c appear to be analogous to superconductivity in the organics, which is brought about by a wave-vector nesting and Fermi surface reconstruction. The only problem, it appeared, that needed to be reconciled was with Angle Resolved Photo-Emission Spectroscopy (ARPES) and Scanning Tunneling Microscopy (STM) data that claimed to see no such Fermi surface, instead only "arcs", a set of disconnected segments in the Brillouin zone which quasiparticle peaks are observed at the Fermi energy, which in a mean field description does not allow for a continuous Fermi surface contour. These two discrepancies led to the "arc vs pocket" debate, which is still unresolved. The other kink in the quantum oscillation armor is that, to this date, quantum oscillations in the hole-doped cuprates have only been seen in YBCO, the only cuprate structure to have CuO chains, which conduct and are located in between two CuO2 superconducting planes in the unit cell. In an attempt to reconcile the "arc vs

  7. SEACAS Theory Manuals: Part II. Nonlinear Continuum Mechanics

    SciTech Connect

    Attaway, S.W.; Laursen, T.A.; Zadoks, R.I.

    1998-09-01

    This report summarizes the key continuum mechanics concepts required for the systematic prescription and numerical solution of finite deformation solid mechanics problems. Topics surveyed include measures of deformation appropriate for media undergoing large deformations, stress measures appropriate for such problems, balance laws and their role in nonlinear continuum mechanics, the role of frame indifference in description of large deformation response, and the extension of these theories to encompass two dimensional idealizations, structural idealizations, and rigid body behavior. There are three companion reports that describe the problem formulation, constitutive modeling, and finite element technology for nonlinear continuum mechanics systems.

  8. The submillimeter radio continuum of Comet P/Brorsen-Metcalf

    SciTech Connect

    Jewitt, D.; Luu, J. MIT, Cambridge, MA )

    1990-12-01

    Observations of Comet P/Brorsen-Metcalf in the submillimeter radio continuum are presented. The observations were taken using the James Clerk Maxwell Telescope on Mauna Kea, and include the first truly submillimeter detection of a comet, and the first submillimeter continuum spectrum. The submillimeter radiation is attributed to thermal emission from a transient population of large grains with a total mass of (1-10) x 10 to the 9th kg. The large grains may be produced by catastrophic failure of part of the refractory mantle on the surface of the cometary nucleus. Models of the submillimeter continuum are discussed. 49 refs.

  9. Semianalytic continuum spectra of Type 2 supernovae

    NASA Technical Reports Server (NTRS)

    Montes, Marcos J.; Wagoner, Robert V.

    1995-01-01

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

  10. Continuum physics: Correlation and fluctuation analysis

    SciTech Connect

    Herskind, B.

    1993-10-01

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

  11. The Hurricane-Flood-Landslide Continuum

    NASA Technical Reports Server (NTRS)

    Negri, Andrew J.; Burkardt, Nina; Golden, Joseph H.; Halverson, Jeffrey B.; Huffman, George J.; Larsen, Matthew C.; McGinley, John A.; Updike, Randall G.; Verdin, James P.; Wieczorek, Gerald F.

    2005-01-01

    In August 2004, representatives from NOAA, NASA, the USGS, and other government agencies convened in San Juan, Puerto Rim for a workshop to discuss a proposed research project called the Hurricane-Flood-Landslide Continuum (HFLC). The essence of the HFLC is to develop and integrate tools across disciplines to enable the issuance of regional guidance products for floods and landslides associated with major tropical rain systems, with sufficient lead time that local emergency managers can protect vulnerable populations and infrastructure. All three lead agencies are independently developing precipitation-flood-debris flow forecasting technologies, and all have a history of work on natural hazards both domestically and overseas. NOM has the capability to provide tracking and prediction of storm rainfall, trajectory and landfall and is developing flood probability and magnTtude capabilities. The USGS has the capability to evaluate the ambient stability of natural and man-made landforms, to assess landslide susceptibilities for those landforms, and to establish probabilities for initiation of landslides and debris flows. Additionally, the USGS has well-developed operational capacity for real-time monitoring and reporting of streamflow across distributed networks of automated gaging stations (http://water.usgs.gov/waterwatch/). NASA has the capability to provide sophisticated algorithms for satellite remote sensing of precipitation, land use, and in the future, soil moisture. The Workshop sought to initiate discussion among three agencies regarding their specific and highly complimentary capabilities. The fundamental goal of the Workshop was to establish a framework that will leverage the strengths of each agency. Once a prototype system is developed for example, in relatively data-rich Puerto Rim, it could be adapted for use in data-poor, low-infrastructure regions such as the Dominican Republic or Haiti. This paper provides an overview of the Workshop s goals

  12. Mentorship: The Education-Research Continuum

    SciTech Connect

    Correll, D

    2008-05-29

    Mentoring of science students stems naturally from the intertwined link between science education and science research. In fact, the mentoring relationship between a student and a scientist may be thought of analogically as a type of double helix forming the 'DNA' that defines the blueprint for the next generation of scientists. Although this analogy would not meet the rigorous tests commonly used for exploring the natural laws of the universe, the image depicted does capture how creating and sustaining the future science workforce benefits greatly from the continuum between education and research. The path science students pursue from their education careers to their research careers often involves training under an experienced and trusted advisor, i.e., a mentor. For many undergraduate science students, a summer research internship at a DOE National Laboratory is one of the many steps they will take in their Education-Research Continuum. Scientists who choose to be mentors share a commitment for both science education and science research. This commitment is especially evident within the research staff found throughout the Department of Energy's National Laboratories. Research-based internship opportunities within science, technology, engineering and mathematics (STEM) exist at most, if not all, of the Laboratories. Such opportunities for students are helping to create the next generation of highly trained professionals devoted to the task of keeping America at the forefront of scientific innovation. 'The Journal of Undergraduate Research' (JUR) provides undergraduate interns the opportunity to publish their scientific innovation and to share their passion for education and research with fellow students and scientists. The theme of this issue of the JUR (Vol. 8, 2008) is 'Science for All'. Almost 20 years have passed since the American Association for the Advancement of Science published its 1989 report, 'Science for All Americans-Project 2061'. The first

  13. Failure of brittle heterogeneous materials: Intermittency or continuum regime

    NASA Astrophysics Data System (ADS)

    Barés, Jonathan; Bonamy, Daniel; Barbier, Luc

    2014-03-01

    The problem of the solid fracture has occupied scientists and engineers for centuries. This phenomenon is classically addressed within the framework of continuum mechanics. Still, stress enhancement at crack tips makes the failure behavior observed at the continuum-level scale extremely dependent on the presence of microstructure inhomogeneities down to very small scales. This yields statistical aspects which, by essence, cannot be addressed using the conventional engineering continuum approaches. We addressed the problem numerically. The simulations invoke a recent statistical model mapping heterogeneous fracture with the depinning transition of an elastic manifold in a random potential. The numerical exploration of the parameter space allowed us to unravel when (i.e. which loading conditions, microstructure material parameters, material constants...) regular dynamics compatible with continuum approaches are expected to be observed, and when crackling dynamics calling for statistical approaches are observed. In this latter case, we have characterized quantitatively the dynamics statistic and its variations as a function of the input parameters.

  14. Equivalent-Continuum Modeling of Nano-Structured Materials

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Gates, Thomas S.; Nicholson, Lee M.; Wise, Kristopher E.

    2001-01-01

    A method has been developed for modeling structure-property relationships of nano-structured materials. This method serves as a link between computational chemistry and solid mechanics by substituting discrete molecular structures with an equivalent-continuum model. It has been shown that this substitution may be accomplished by equating the vibrational potential energy of a nano-structured material with the strain energy of representative truss and continuum models. As an important example with direct application to the development and characterization of single-walled carbon nanotubes, the model has been applied to determine the effective continuum geometry of a graphene sheet. A representative volume element of the equivalent-continuum model has been developed with an effective thickness. This effective thickness has been shown to be similar to, but slightly smaller than, the interatomic spacing of graphite.

  15. Propagation of continuum damage in a viscoelastic ice bar

    SciTech Connect

    Shin, J.G. . Dept. of Naval Architecture and Ocean Engineering); Karr, D.G. . Dept. of Naval Architecture and Marine Engineering)

    1994-05-01

    An initial value problem of a semi-infinite nonlinear viscoelastic bar is solved with continuum damage evolution. The evolution law of the continuum damage for a viscoelastic material is used in order to explore the propagation of two crushing mechanisms: grain boundary cracking and transgranular cracking. Using the method of characteristics, the speed of propagation is found to be dependent on the continuum damage. On the wave front, the delayed elastic strain is zero, and only the continuum damage due to the transgranular cracking evolves. A finite difference method is developed to solve the governing equations on the obtained characteristic lines, and gives a stable solution for the propagation of the stress, strain, and damage. Numerical results are obtained and discussed using the material properties of polycrystalline ice.

  16. Continuum discretised BCS approach for weakly bound nuclei

    NASA Astrophysics Data System (ADS)

    Lay, J. A.; Alonso, C. E.; Fortunato, L.; Vitturi, A.

    2016-08-01

    The Bardeen–Cooper–Schrieffer (BCS) formalism is extended by including the single-particle continuum in order to analyse the evolution of pairing in an isotopic chain from stability up to the drip-line. We propose a continuum discretised generalised BCS based on single-particle pseudostates (PS). These PS are generated from the diagonalisation of the single-particle Hamiltonian within a transformed harmonic oscillator basis. The consistency of the results versus the size of the basis is studied. The method is applied to neutron rich oxygen and carbon isotopes and compared with similar previous works and available experimental data. We make use of the flexibility of the proposed model in order to study the evolution of the occupation of the low-energy continuum when the system becomes weakly bound. We find an increasing influence of the non-resonant continuum as long as the Fermi level approaches the neutron separation threshold.

  17. The continuum intensity as a function of magnetic field. II. Local magnetic flux and convective flows

    NASA Astrophysics Data System (ADS)

    Kobel, P.; Solanki, S. K.; Borrero, J. M.

    2012-06-01

    the larger and stronger magnetic patches. This, together with the known presence of larger magnetic features, could explain the previously found lower contrasts of the brightest magnetic elements in ARs compared to the QS. The inhibition of convection also affects the average continuum brightness of a photospheric region, so that at disk center, an area of photosphere in strong network or plage appears darker than a purely quiet one. This is qualitatively consistent with the predictions of 3D MHD simulations.

  18. An extended Coleman-Noll procedure for generalized continuum theories

    NASA Astrophysics Data System (ADS)

    Hütter, Geralf

    2016-05-01

    Within rational continuum mechanics, the Coleman-Noll procedure is established to derive requirements to constitutive equations. Aiming in particular at generalized continuum theories, the present contribution demonstrates how this procedure can be extended to yield additionally the underlying balance equations of stress-type quantities. This is demonstrated for micromorphic and strain gradient media as well as for the microforce theory. The relation between the extended Coleman-Noll procedure and the method of virtual powers is pointed out.

  19. Uses of continuum radiation in the AXAF calibration

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  20. Negative-continuum dielectronic recombination for heavy ions

    SciTech Connect

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

    2003-05-01

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

  1. Uses of Continuum Radiation in the AXAF Calibration

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  2. Progress in Using Continuum radiation for AXAF Calibration

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

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

  3. THE UV-CONTINUUM PROPERTIES OF Ly{alpha}-SELECTED GALAXIES AT z = 6.5

    SciTech Connect

    Cowie, Lennox L.; Hu, Esther M.; Songaila, Antoinette E-mail: acowie@ifa.hawaii.edu

    2011-07-10

    We report the first space-based very deep near-infrared continuum observations of a uniform sample of z = 6.5 galaxies with log(L(Ly{alpha})) = 42.5-43 erg s{sup -1} selected from narrowband line searches and with spectroscopically confirmed Ly{alpha} emission. The 1.4 {mu}m Hubble Space Telescope WFC3 observations are deep enough (AB(1{sigma}) = 28.75) to measure individual continuum magnitudes at this redshift for all of the objects. We compare the results with continuum-selected samples at the same redshift and find that Ly{alpha} emission is present in 24% of all galaxies with M{sub AB}(1350 A) < -20 at z = 6.5. The error in this quantity is dominated by systematic uncertainties, which could be as large as multiplicative factors of three. The Ly{alpha} galaxies are extended but small (size <1 kpc), and have star formation rates of approximately 10 M{sub sun} yr{sup -1}. We find a mean L(Ly{alpha})/{nu}L{sub {nu}} at 1400 A to be 0.08, with the seven objects showing a range from 0.026 to 0.26, implying that there is little sign of destruction of the Ly{alpha} line. All of the properties of the z = 6.5 sample appear to be very similar to those of Ly{alpha} emitters at lower redshifts.

  4. Continuum Spectrum and Radiation Pattern Contributions to T-Wave Excitation

    NASA Astrophysics Data System (ADS)

    Soukup, D. J.; Odom, R. I.

    2001-12-01

    Modal scattering along the seafloor bottom provides us with important insight into the excitation of T-waves, linking seafloor scattering with sloping seafloors. A modal representation of the seismic source field reveals how energy can transfer from seismic source modes to T-wave contributing acoustic modes. The key to the T-wave excitation is found in any boundary roughness or non-planar bathymetry which promotes energy conversion from crustal and ocean crustal/acoustic modes into low order T-wave acoustic modes. We compute seismic, acoustic and ocean crustal/acoustic hybrid modes for oceanic models with sediment covered bottoms. Various source depths are considered to determine the impact on the resulting T-wave excitation. We use the locked mode approach to determine the continuum modes as source depth increases. We also consider radiation pattern effects on T-wave excitation from a seismic source. Included in our investigation are the effects of sediment cover on T-wave excitation. At shallow source depths, the discrete modes contribute to the majority of the T-wave excitation. The continuum spectrum becomes more important with increasing source depth. While the lower order modes still contribute significantly to the T-wave excitation, the continuum spectrum cannot be neglected at large source depths. Preliminary results reveal radiation pattern effects and source type effects may be distinguishable in T-wave data.

  5. Spectral structure and stability studies on microstructure-fiber continuum

    NASA Astrophysics Data System (ADS)

    Gu, Xun; Kimmel, Mark; Zeek, Erik; Shreenath, Aparna P.; Trebino, Rick P.; Windeler, Robert S.

    2003-07-01

    Although previous direct measurements of the microstructure-fiber continuum have all showed a smooth and stable spectrum, our cross-correlation frequency-resolved optical gating (XFROG) full-intensity-and-phase characterization of the continuum pulse, utilizing sum-frequency-generation with a pre-characterized reference pulse and the angle-dithered-crystal technique, indicates that fine-scale spectral structure exists on a single-shot basis, contrary to previous observations. In particular, deep and fine oscillations are found in the retrieved spectrum, and the retrieved trace contains a "measles" pattern, whereas the measured trace and the independently-measured spectrum are rather smooth. The discrepancy is shown to be the result of unstable single-shot spectral structure. Although the XFROG measurement is not able to directly measure the single-shot fine structure in the trace, the redundancy of information in FROG traces enables the retrieval algorithm to correctly recognize the existence of the spectral fine structure, and restore the structure in the retrieved trace and spectrum. Numerical simulations have supported our hypothesis, and we directly observed the fine spectral structure in single-shot measurements of the continuum spectrum and the structure was seen to be highly unstable, the continuum spectrum appearing smooth only when many shots are averaged. Despite the structure and instability in the continuum spectrum, coherence experiments also reveal that the spectral phase is rather stable, being able to produce well-defined spectral fringes across the entire continuum bandwidth.

  6. Relativistic corrections and non-Gaussianity in radio continuum surveys

    SciTech Connect

    Maartens, Roy; Zhao, Gong-Bo; Bacon, David; Koyama, Kazuya; Raccanelli, Alvise E-mail: Gong-bo.Zhao@port.ac.uk E-mail: Kazuya.Koyama@port.ac.uk

    2013-02-01

    Forthcoming radio continuum surveys will cover large volumes of the observable Universe and will reach to high redshifts, making them potentially powerful probes of dark energy, modified gravity and non-Gaussianity. We consider the continuum surveys with LOFAR, WSRT and ASKAP, and examples of continuum surveys with the SKA. We extend recent work on these surveys by including redshift space distortions and lensing convergence in the radio source auto-correlation. In addition we compute the general relativistic (GR) corrections to the angular power spectrum. These GR corrections to the standard Newtonian analysis of the power spectrum become significant on scales near and beyond the Hubble scale at each redshift. We find that the GR corrections are at most percent-level in LOFAR, WODAN and EMU surveys, but they can produce O(10%) changes for high enough sensitivity SKA continuum surveys. The signal is however dominated by cosmic variance, and multiple-tracer techniques will be needed to overcome this problem. The GR corrections are suppressed in continuum surveys because of the integration over redshift — we expect that GR corrections will be enhanced for future SKA HI surveys in which the source redshifts will be known. We also provide predictions for the angular power spectra in the case where the primordial perturbations have local non-Gaussianity. We find that non-Gaussianity dominates over GR corrections, and rises above cosmic variance when f{sub NL}∼>5 for SKA continuum surveys.

  7. Integrated Radio Continuum Spectra of Galaxies

    NASA Astrophysics Data System (ADS)

    Marvil, Joshua; Owen, Frazer; Eilek, Jean

    2015-01-01

    We investigate the spectral shape of the total continuum radiation, between 74 MHz and 5 GHz (400-6 cm in wavelength), for a large sample of bright galaxies. We take advantage of the overlapping survey coverage of the VLA Low-Frequency Sky Survey, the Westerbork Northern Sky Survey, the NRAO VLA Sky Survey, and the Green Bank 6 cm Survey to achieve significantly better resolution, sensitivity, and sample size compared to prior efforts of this nature. For our sample of 250 bright galaxies we measure a mean spectral index, α, of -0.69 between 1.4 and 4.85 GHz, -0.55 between 325 MHz and 1.4 GHz, and -0.45 between 74 and 325 MHz, which amounts to a detection of curvature in the mean spectrum. The magnitude of this curvature is approximately Δα = -0.2 per logarithmic frequency decade when fit with a generalized function having constant curvature. No trend in low-frequency spectral flattening versus galaxy inclination is evident in our data, suggesting that free-free absorption is not a satisfying explanation for the observed curvature. The ratio of thermal to non-thermal emission is estimated through two independent methods: (1) using the IRAS far-IR fluxes and (2) with the value of the total spectral index. Method (1) results in a distribution of 1.4 GHz thermal fractions of 9% ± 3%, which is consistent with previous studies, while method (2) produces a mean 1.4 GHz thermal fraction of 51% with dispersion 26%. The highly implausible values produced by method (2) indicate that the sum of typical power-law thermal and non-thermal components is not a viable model for the total spectral index between 325 and 1.4 GHz. An investigation into relationships between spectral index, infrared-derived quantities, and additional source properties reveals that galaxies with high radio luminosity in our sample are found to have, on average, a flatter radio spectral index, and early types tend to have excess radio emission when compared to the radio-infrared ratio of later types

  8. Integrated radio continuum spectra of galaxies

    SciTech Connect

    Marvil, Joshua; Owen, Frazer; Eilek, Jean

    2015-01-01

    We investigate the spectral shape of the total continuum radiation, between 74 MHz and 5 GHz (400-6 cm in wavelength), for a large sample of bright galaxies. We take advantage of the overlapping survey coverage of the VLA Low-Frequency Sky Survey, the Westerbork Northern Sky Survey, the NRAO VLA Sky Survey, and the Green Bank 6 cm Survey to achieve significantly better resolution, sensitivity, and sample size compared to prior efforts of this nature. For our sample of 250 bright galaxies we measure a mean spectral index, α, of –0.69 between 1.4 and 4.85 GHz, –0.55 between 325 MHz and 1.4 GHz, and –0.45 between 74 and 325 MHz, which amounts to a detection of curvature in the mean spectrum. The magnitude of this curvature is approximately Δα = –0.2 per logarithmic frequency decade when fit with a generalized function having constant curvature. No trend in low-frequency spectral flattening versus galaxy inclination is evident in our data, suggesting that free-free absorption is not a satisfying explanation for the observed curvature. The ratio of thermal to non-thermal emission is estimated through two independent methods: (1) using the IRAS far-IR fluxes and (2) with the value of the total spectral index. Method (1) results in a distribution of 1.4 GHz thermal fractions of 9% ± 3%, which is consistent with previous studies, while method (2) produces a mean 1.4 GHz thermal fraction of 51% with dispersion 26%. The highly implausible values produced by method (2) indicate that the sum of typical power-law thermal and non-thermal components is not a viable model for the total spectral index between 325 and 1.4 GHz. An investigation into relationships between spectral index, infrared-derived quantities, and additional source properties reveals that galaxies with high radio luminosity in our sample are found to have, on average, a flatter radio spectral index, and early types tend to have excess radio emission when compared to the radio-infrared ratio of later

  9. Energy absorption due to spatial resonance of Alfven waves at continuum tip

    NASA Astrophysics Data System (ADS)

    Chen, Eugene; Berk, Herb; Breizman, Boris; Zheng, Linjin

    2011-10-01

    We investigate the response of tokamak plasma to an external driving source. An impedance-like function depending on the driving frequency that is growing at a small rate, is calculated and interpreted with different source profiles. Special attention is devoted to the case where driving frequency approaches that of the TAE continuum tip. The calculation can be applied to the estimation of TAE damping rate by analytically continuing the inverse of the impedance function to the lower half plane. The root of the analytic continuation corresponds to the existence of a quasi-mode, from which the damping rate can be found.

  10. NMR investigation of field-induced magnetic order in barium manganese oxide

    NASA Astrophysics Data System (ADS)

    Suh, Steve

    As early as 1956, Matsubara and Matsuda found an exact correspondence between a lattice gas model and a quantum antiferromagnet model[1]. They paved the way for the language of integer spin boson particles to be used interchangeably with quantum magnetic insulator systems in a general manner. For example, an analogy of density of bosons is found in magnetization, and analogy of chemical potential is found in external field. Just as there exist corresponding parameters between these two seemingly unrelated systems, quantum magnets can also exhibit consequences of Boson particle systems. In particular, spin-ordering transition in quantum magnets can be interpreted as Bose-Einstein condensate (BEC) transition in Boson particle framework. Direct observation of BEC in Boson particles has been realized in 4He's superfluid transition and in dilute atomic gas clouds cooled to very low temperatures[2]. In this thesis, we try to realize and analyze BEC transition through field-induced spin-ordering transition in the S = 1 antiferromagnetic dimer system, Ba3Mn2O8. We perform NMR measurements with 135,137Ba nucleus as a local probe. Although S = 1 spin properties of Ba 3Mn2O8 come from electronic spins on Mn atoms, hyperfine coupling between Mn electronic spins and Ba nuclear spins allow us to infer Mn electrons' spin information. Since there are 2 inequivalent Ba sites, Ba(1) and Ba(2), in Ba3Mn2O8, we essentially have two probes that provide a detailed picture of structure and nature of magnetism in this material. There are many antiferromagnetic BEC candidates, but there is a significant advantage of studying Ba3Mn 2O8. Unlike the other popular antiferromagnetic BEC candidates such as TlCuCl3[3] or BaCuSi2O6[4], we find no evidence of lattice deformation in Ba3Mn2O8 . This allows us an unprecedented clean look at magnetic properties. Aside from the aforementioned simple technical advantage, there are new physics that we can learn from Ba3Mn2O 8. The geometric frustration of

  11. Giant effective mass deviations near the magnetic field-induced minigap in double quantum wells

    SciTech Connect

    Harff, N.E. |; Simmons, J.A.; Lyo, S.K.; Klem, J.F.; Goodnick, S.M.

    1994-09-01

    The authors report major deviations in the electron effective mass m* near the partial energy gap, or minigap, formed in strongly coupled double quantum wells (QWs) by an anticrossing of the two QW dispersion curves. The anticrossing and minigap are induced by an in-plane magnetic field B{sub {parallel}} and give rise to large distortions in the Fermi surface and density of states, including a Van Hove singularity. Sweeping B{sub {parallel}} moves the minigap through the Fermi level, with the upper and lower gap edges producing a sharp maximum and minimum in the low-temperature in-plane conductance, in agreement with theoretical calculations. The temperature dependence of Shubnikov-de Haas (SdH) oscillations appearing in a tilted magnetic field yield a decreased m* {le} 1/3 m*{sub GaAs} near the upper gap edge, and indicate an increase in m* near the lower gap edge.

  12. Genomic Study of Cardiovascular Continuum Comorbidity

    PubMed Central

    Makeeva, O. A.; Sleptsov, A. A.; Kulish, E. V.; Barbarash, O. L.; Mazur, A. M.; Prokhorchuk, E. B.; Chekanov, N. N.; Stepanov, V. A.; Puzyrev, V. P.

    2015-01-01

    Comorbidity or a combination of several diseases in the same individual is a common and widely investigated phenomenon. However, the genetic background for non–random disease combinations is not fully understood. Modern technologies and approaches to genomic data analysis enable the investigation of the genetic profile of patients burdened with several diseases (polypathia, disease conglomerates) and its comparison with the profiles of patients with single diseases. An association study featuring three groups of patients with various combinations of cardiovascular disorders and a control group of relatively healthy individuals was conducted. Patients were selected as follows: presence of only one disease, ischemic heart disease (IHD); a combination of two diseases, IHD and arterial hypertension (AH); and a combination of several diseases, including IHD, AH, type 2 diabetes mellitus (T2DM), and hypercholesterolemia (HC). Genotyping was performed using the “My Gene” genomic service (www.i–gene.ru). An analysis of 1,400 polymorphic genetic variants and their associations with the studied phenotypes are presented. A total of 14 polymorphic variants were associated with the phenotype “IHD only,” including those in the APOB, CD226, NKX2–5, TLR2, DPP6, KLRB1, VDR, SCARB1, NEDD4L, and SREBF2 genes, and intragenic variants rs12487066, rs7807268, rs10896449, and rs944289. A total of 13 genetic markers were associated with the “IHD and AH” phenotype, including variants in the BTNL2, EGFR, CNTNAP2, SCARB1, and HNF1A genes, and intragenic polymorphisms rs801114, rs10499194, rs13207033, rs2398162, rs6501455, and rs1160312. A total of 14 genetic variants were associated with a combination of several diseases of cardiovascular continuum (CVC), including those in the TAS2R38, SEZ6L, APOA2, KLF7, CETP, ITGA4, RAD54B, LDLR, and MTAP genes, along with intragenic variants rs1333048, rs1333049, and rs6501455. One common genetic marker was identified for the

  13. Electric-field-induced semiconductor-semiconductor transition in V2O5

    NASA Astrophysics Data System (ADS)

    Fisher, B.; Genossar, J.; Patlagan, L.; Chashka, K. B.; Reisner, G. M.

    2015-08-01

    We report on DC I- V characteristics of two crystalline V2O5 fibers measured at room temperature over a range of currents of more than four orders of magnitude. At low currents, the resistances of the samples decrease exponentially with voltage, a behavior that can be attributed to field-enhanced tunneling. At higher currents, self-heating induces hysteretic nonlinear conductivity and small jumps toward lower resistances. In the highest range of currents, the I- V characteristics exhibit dramatic switching toward a new state with much lower resistance and memory. At first, switching could be repeated several times by cycling the sample between lower and higher currents. Eventually, a final state stabilized with smooth nonlinear I- V characteristics. The temperature dependence of the resistance of both the initial and final states is activated with similar activation energies; the voltage dependence of the resistance at low currents is also similar except for the large ratio of the pre-exponents. The final state of the samples was identified by the X-ray diffraction pattern of one of them, as the stable α-V2O5 phase. An interpretation of these results based on switching between metastable and stable phases of V2O5 is proposed.

  14. Magnetic-field-induced ferroelectric polarization reversal in the multiferroic Ge(1-x)Mn(x)Te semiconductor.

    PubMed

    Przybylińska, H; Springholz, G; Lechner, R T; Hassan, M; Wegscheider, M; Jantsch, W; Bauer, G

    2014-01-31

    Ge(1-x)Mn(x)Te is shown to be a multiferroic semiconductor, exhibiting both ferromagnetic and ferroelectric properties. By ferromagnetic resonance we demonstrate that both types of order are coupled to each other. As a result, magnetic-field-induced ferroelectric polarization reversal is achieved. Switching of the spontaneous electric dipole moment is monitored by changes in the magnetocrystalline anisotropy. This also reveals that the ferroelectric polarization reversal is accompanied by a reorientation of the hard and easy magnetization axes. By tuning the GeMnTe composition, the interplay between ferromagnetism and ferroelectricity can be controlled. PMID:24580486

  15. The magnetic-field-induced transition from an expanding plasma to a double layer containing expanding plasma

    SciTech Connect

    Charles, C.; Boswell, R. W.

    2007-11-12

    The magnetic-field-induced transition from a simple expansion to a double layer is experimentally investigated in an argon low pressure radio frequency helicon source plasma. When the magnetic field is increased from 30 to 140 G in the plasma source, an abrupt increase in the plasma density and upstream potential is measured at 50 G. In the downstream plasma, the plasma density and potential show a small decrease with increasing magnetic field and no abrupt change. When the upstream jump is measured, simultaneous measurements in the downstream plasma show an ion beam characteristic of a double layer near the source exit.

  16. In situ study of electric field-induced magnetization in multiferroic BiFeO(3) nanowires.

    PubMed

    Prashanthi, K; Thundat, T

    2014-01-01

    In this work, we have studied electric field-induced magnetization effect of multiferroic BiFeO3 (BFO) nanowires in situ using magnetic force microscopy (MFM). Changes in magnetic domain contrast have been observed in the MFM phase images under applied electric potential, which indicate local magnetoelectric (ME) coupling in the nanowires. The values of saturation and magnetization at different applied electric fields were evaluated. These results suggest that one-dimensional multiferroic BFO nanowires are potential candidates for realizing multiferroic devices at nanoscale with unique functionalities. PMID:23637049

  17. Electric field induced biaxiality and the electro-optic effect in a bent-core nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Nagaraj, Mamatha; Panarin, Y. P.; Manna, U.; Vij, J. K.; Keith, C.; Tschierske, C.

    2010-01-01

    We report the observation of a biaxial nematic phase in a bent-core molecular system using polarizing microscopy, electro-optics, and dielectric spectroscopy, where we find that the biaxiality exists on a microscopic scale. An application of electric field induces a macroscopic biaxiality and in consequence gives rise to electro-optic switching. This electro-optic effect shows significant potential in applications for displays due to its fast high-contrast response. The observed electro-optic switching is explained in terms of the interaction of the ferroelectric clusters with the electric field.

  18. An atomistic-continuum Cosserat rod model of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Chandraseker, Karthick; Mukherjee, Subrata; Paci, Jeffrey T.; Schatz, George C.

    2009-06-01

    The focus of the present work is an atomistic-continuum model of single-walled carbon nanotubes (CNTs) based on an elastic rod theory which can exhibit geometric as well as material nonlinearity [Healey, T.J., 2002. Material symmetry and chirality in nonlinearly elastic rods. Mathematics and Mechanics of Solids 7, 405-420]. In particular, the single-walled carbon nanotube (SWNT) is modeled as a one-dimensional elastic continuum with some finite thickness bounded by the lateral surface. Exploitation of certain symmetries in the underlying atomic structure leads to suitable representations of the continuum elastic strain energy density in terms of strain measures that capture extension, twist, bending, and shear deformations [Healey, T.J., 2002. Material symmetry and chirality in nonlinearly elastic rods. Mathematics and Mechanics of Solids 7, 405-420]. Bridging between the atomic scale and the effective continuum is carried out by parameterization of the continuum elastic energy and determination of the parameters using unit cell atomistic simulations over a range of deformation magnitudes and types. Specifically, the proposed model takes into account (a) bending, (b) twist, (c) shear, (d) extension, (e) coupled extension and twist, and (f) coupled bending and shear deformations. The extracted parameters reveal benefits of accounting for important anisotropic and large-strain effects as improvements over employing traditional, linearly elastic, isotropic, small-strain, continuum models to simulate deformations of atomic systems such as SWNTs. It is envisioned that the proposed approach and the extracted model parameters can serve as a useful input to simulations of SWNT deformations using existing nonlinearly elastic continuum codes based, for example, on the finite element method (FEM).

  19. Imprints of Molecular Clouds in Radio Continuum Images

    NASA Astrophysics Data System (ADS)

    Yusef-Zadeh, F.

    2012-11-01

    We show radio continuum images of several molecular complexes in the inner Galaxy and report the presence of dark features that coincide with dense molecular clouds. Unlike infrared dark clouds, these features which we call "radio dark clouds" are produced by a deficiency in radio continuum emission from molecular clouds that are embedded in a bath of UV radiation field or synchrotron emitting cosmic-ray particles. The contribution of the continuum emission along different path lengths results in dark features that trace embedded molecular clouds. The new technique of identifying cold clouds can place constraints on the depth and the magnetic field of molecular clouds when compared to those of the surrounding hot plasma radiating at radio wavelengths. The study of five molecular complexes in the inner Galaxy, Sgr A, Sgr B2, radio Arc, the Snake filament, and G359.75-0.13 demonstrates an anti-correlation between the distributions of radio continuum and molecular line and dust emission. Radio dark clouds are identified in Green Bank Telescope maps and Very Large Array images taken with uniform sampling of uv coverage. The level at which the continuum flux is suppressed in these sources suggests that the depth of the molecular cloud is similar to the size of the continuum emission within a factor of two. These examples suggest that high-resolution, high-dynamic-range continuum images can be powerful probes of interacting molecular clouds with massive stars and supernova remnants in regions where the kinematic distance estimates are ambiguous as well as in the nuclei of active galaxies.

  20. A Description of the Continuum of Eating Disorders: Implications for Intervention and Research.

    ERIC Educational Resources Information Center

    Scarano, Gina M.; Kalodner-Martin, Cynthia R.

    1994-01-01

    Presents an eating disorders continuum. Describes groups on the continuum by highlighting behavioral, cognitive-attitudinal, and self-esteem differences. Discusses relationship between continuum and developmental course of eating disorders. Presents prevention, early intervention, and treatment programs for various continuum groups. Offers…

  1. Theoretical Calculation and Validation of the Water Vapor Continuum Absorption

    NASA Technical Reports Server (NTRS)

    Ma, Qiancheng; Tipping, Richard H.

    1998-01-01

    The primary objective of this investigation is the development of an improved parameterization of the water vapor continuum absorption through the refinement and validation of our existing theoretical formalism. The chief advantage of our approach is the self-consistent, first principles, basis of the formalism which allows us to predict the frequency, temperature and pressure dependence of the continuum absorption as well as provide insights into the physical mechanisms responsible for the continuum absorption. Moreover, our approach is such that the calculated continuum absorption can be easily incorporated into satellite retrieval algorithms and climate models. Accurate determination of the water vapor continuum is essential for the next generation of retrieval algorithms which propose to use the combined constraints of multi-spectral measurements such as those under development for EOS data analysis (e.g., retrieval algorithms based on MODIS and AIRS measurements); current Pathfinder activities which seek to use the combined constraints of infrared and microwave (e.g., HIRS and MSU) measurements to improve temperature and water profile retrievals, and field campaigns which seek to reconcile spectrally-resolved and broad-band measurements such as those obtained as part of FIRE. Current widely used continuum treatments have been shown to produce spectrally dependent errors, with the magnitude of the error dependent on temperature and abundance which produces errors with a seasonal and latitude dependence. Translated into flux, current water vapor continuum parameterizations produce flux errors of order 10 W/ml, which compared to the 4 W/m' magnitude of the greenhouse gas forcing and the 1-2 W/m' estimated aerosol forcing is certainly climatologically significant and unacceptably large. While it is possible to tune the empirical formalisms, the paucity of laboratory measurements, especially at temperatures of interest for atmospheric applications, preclude tuning

  2. Theoretical Calculation and Validation of the Water Vapor Continuum Absorption

    NASA Technical Reports Server (NTRS)

    Ma, Qiancheng; Tipping, Richard H.

    1998-01-01

    The primary objective of this investigation is the development of an improved parameterization of the water vapor continuum absorption through the refinement and validation of our existing theoretical formalism. The chief advantage of our approach is the self-consistent, first principles, basis of the formalism which allows us to predict the frequency, temperature and pressure dependence of the continuum absorption as well as provide insights into the physical mechanisms responsible for the continuum absorption. Moreover, our approach is such that the calculated continuum absorption can be easily incorporated into satellite retrieval algorithms and climate models. Accurate determination of the water vapor continuum is essential for the next generation of retrieval algorithms which propose to use the combined constraints of multispectral measurements such as those under development for EOS data analysis (e.g., retrieval algorithms based on MODIS and AIRS measurements); current Pathfinder activities which seek to use the combined constraints of infrared and microwave (e.g., HIRS and MSU) measurements to improve temperature and water profile retrievals, and field campaigns which seek to reconcile spectrally-resolved and broad-band measurements such as those obtained as part of FIRE. Current widely used continuum treatments have been shown to produce spectrally dependent errors, with the magnitude of the error dependent on temperature and abundance which produces errors with a seasonal and latitude dependence. Translated into flux, current water vapor continuum parameterizations produce flux errors of order 10 W/sq m, which compared to the 4 W/sq m magnitude of the greenhouse gas forcing and the 1-2 W/sq m estimated aerosol forcing is certainly climatologically significant and unacceptably large. While it is possible to tune the empirical formalisms, the paucity of laboratory measurements, especially at temperatures of interest for atmospheric applications, preclude

  3. Predicted electric-field-induced hexatic structure in an ionomer membrane

    NASA Astrophysics Data System (ADS)

    Allahyarov, Elshad; Taylor, Philip L.

    2009-08-01

    Coarse-grained molecular-dynamics simulations were used to study the morphological changes induced in a Nafion®-like ionomer by the imposition of a strong electric field. We observe the formation of structures aligned along the direction of the applied field. The polar head groups of the ionomer sidechains aggregate into clusters, which then form rodlike formations which assemble into a hexatic array aligned with the direction of the field. Occasionally these lines of sulfonates and protons form a helical structure. Upon removal of the electric field, the hexatic array of rodlike structures persists and has a lower calculated free energy than the original isotropic morphology.

  4. Electric-Field-Induced Alignment of Block Copolymer/Nanoparticle Blends

    SciTech Connect

    Liedel, Clemens; Schindler, Kerstin; Pavan, Mariela J.; Lewin, Christian; Pester, Christian W; Ruppel, Markus A; Urban, Volker S; Shenhar, Roy; Boker, Alexander

    2013-01-01

    External electric fi elds readily align birefringent block-copolymer mesophases. In this study the effect of gold nanoparticles on the electric-fi eld-induced alignment of a lamellae-forming polystyrene- block -poly(2-vinylpyridine) copolymer is assessed. Nanoparticles are homogeneously dispersed in the styrenic phase and promote the quantitative alignment of lamellar domains by substantially lowering the critical field strength above which alignment proceeds. The results suggest that the electric-fi eldassisted alignment of nanostructured block copolymer/nanoparticle composites may offer a simple way to greatly mitigate structural and orientational defects of such fi lms under benign experimental conditions.

  5. Do subglacial bedforms comprise a size and shape continuum?

    NASA Astrophysics Data System (ADS)

    Ely, Jeremy C.; Clark, Chris D.; Spagnolo, Matteo; Stokes, Chris R.; Greenwood, Sarah L.; Hughes, Anna L. C.; Dunlop, Paul; Hess, Dale

    2016-03-01

    Understanding the evolution of the ice-bed interface is fundamentally important for gaining insight into the dynamics of ice masses and how subglacial landforms are created. However, the formation of the suite of landforms generated at this boundary - subglacial bedforms - is a contentious issue that is yet to be fully resolved. Bedforms formed in aeolian, fluvial, and marine environments either belong to separate morphological populations or are thought to represent a continuum of forms generated by the same governing processes. For subglacial bedforms, a size and shape continuum has been hypothesised, yet it has not been fully tested. Here we analyse the largest data set of subglacial bedform size and shape measurements ever collated (96,900 bedforms). Our results show that flutes form a distinct population of narrow bedforms. However, no clear distinction was found between drumlins and megascale glacial lineations (MSGLs), which form a continuum of subglacial lineations. A continuum of subglacial ribs also exists, with no clear size or shape distinctions indicating separate populations. Furthermore, an underreported class of bedform with no clear orientation to ice flow (quasi-circular bedforms) overlaps with the ribbed and lineation continua and typically occurs in spatial transition zones between the two, potentially merging these three bedform types into a larger continuum.

  6. Measuring the continuum polarization with ESPaDOnS

    NASA Astrophysics Data System (ADS)

    Pereyra, A.; Rodrigues, C. V.; Martioli, E.

    2015-01-01

    Aims: Our goal is to test the feasibility of obtaining accurate measurements of the continuum polarization from high-resolution spectra using the spectropolarimetric mode of ESPaDOnS. Methods: We used the new pipeline OPERA to reduce recent and archived ESPaDOnS data. Several polarization standard stars and science objects were tested for the linear mode. In addition, the circular mode was tested using several objects from the archive with expected null polarization. Synthetic broad-band polarization was computed from the ESPaDOnS continuum polarization spectra and compared with published values (when available) to quantify the accuracy of the instrument. Results: The continuum linear polarization measured by ESPaDOnS is consistent with broad-band polarimetry measurements available in the literature. The accuracy in the degree of linear polarization is around 0.2-0.3% considering the full sample. The accuracy in polarization position angle using the most polarized objects is better than 5°. Consistent with this, the instrumental polarization computed for the circular continuum polarization is also between 0.2-0.3%. Our results suggest that measurements of the continuum polarization using ESPaDOnS are viable and can be used to study many astrophysical objects. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientique of France, and the University of Hawaii.

  7. Empirical water vapor continuum models for infrared propagation

    NASA Astrophysics Data System (ADS)

    Thomas, Michael E.

    1995-06-01

    The characterization of the water vapor continuum remains an important problem concerning infrared propagation in the atmosphere. Radiometric imaging within the atmosphere in the 8 to 12 micrometers and 3 - 5 micrometers regions, and eye safe lidar in the 2 micrometers and 1.6 micrometers window regions require accurate knowledge of the water vapor continuum. Although the physical nature of the continuum is a complex problem, the observed frequency, pressure and temperature dependence can be represented reasonably well by simple mathematical functions consistent with far wing theories. This approach is the basis for current models used in LOWTRAN/MODTRAN and for the models listed in the SPIE/ERIM EO/IR Systems Handbook (Volume 2 Chapter 1). However, these models are based solely on a limited, but high quality, data set collected by a spectrometer and White cell. Additional information on oxygen broadening and temperature dependence is available from numerous laser measurements of the water vapor continuum. A survey of relevant experimental data is made to determine the best available measurements of the water vapor continuum in various atmospheric window regions. Then the data are fit to an empirical model over the entire window region. A good fit is obtained for typical atmospheric conditions covering the 8 to 12 micrometers and 3 to 5 micrometers regions. No experimental data, covering atmospheric conditions, exist in the 2 micrometers and 1.6 micrometers regions. However, models can be proposed based on far wing extrapolations of the bordering vibrational water vapor bands.

  8. Local Electrical Imaging of Tetragonal Domains and Field-Induced Ferroelectric Twin Walls in Conducting SrTiO_{3}.

    PubMed

    Ma, H J Harsan; Scharinger, S; Zeng, S W; Kohlberger, D; Lange, M; Stöhr, A; Wang, X Renshaw; Venkatesan, T; Kleiner, R; Scott, J F; Coey, J M D; Koelle, D; Ariando

    2016-06-24

    We demonstrate electrical mapping of tetragonal domains and electric field-induced twin walls in SrTiO_{3} as a function of temperature and gate bias utilizing the conducting LaAlO_{3}/SrTiO_{3} interface and low-temperature scanning electron microscopy. Conducting twin walls appear below 105 K, and new twin patterns are observed after thermal cycling through the transition or on electric field gating. The nature of the twin walls is confirmed by calculating their intersection angles for different substrate orientations. Numerous walls formed when a large side- or back-gate voltage is applied are identified as field-induced ferroelectric twin walls in the paraelectric tetragonal matrix. The walls persist after switching off the electric field and on thermal cycling below 105 K. These observations point to a new type of ferroelectric functionality in SrTiO_{3}, which could be exploited together with magnetism and superconductivity in a multifunctional context. PMID:27391752

  9. Field induced phase transition in layered honeycomb spin system α-RuCl3 studied by thermal conductivity

    NASA Astrophysics Data System (ADS)

    Leahy, Ian; Bornstein, Alex; Choi, Kwang-Yong; Lee, Minhyea

    α -RuCl3, a quasi -two-dimensional honeycomb lattice is known to be a candidate material to realize the Heisenberg-Kitaev spin model of a highly anisotropic bond-dependent exchange interaction. We investigate in-plane thermal conductivity (κ) as a function of temperature (T) and in-plane applied field (H). At H = 0 , the onset of a strong increase in κ marks the spontaneous long range ordering temperature, Tc = 6 . 5 K , corresponding to ``zigzag'' antiferromagnetic ordering. A broad peak appearing below Tc in κ was found to be suppressed significantly as H increases up to ~ 7 T , implying the system undergoes a field-induced transition from ordered to a new spin-disordered state analogous to the transverse-field Ising model. Further increasing H above 7 . 1 T , the large field seems to begin polarizing spins thus increasing the phonon mean free path, resulting in a significant rise in κ. This tendency is clearly shown in the field dependence of κ below Tc, which has a pronounced minimum at Hmin = 7 . 1 T . We will discuss our scaling analysis to characterize this field-induced phase transition and compare to the transverse-field Ising spin system. Work at the University of Colorado was supported by the US DOE Basic Energy Sciences under Award No. DE-SC0006888.

  10. Field-induced wooden-tip electrospray ionization mass spectrometry for high-throughput analysis of herbal medicines.

    PubMed

    Yang, Yunyun; Deng, Jiewei; Yao, Zhong-Ping

    2015-08-01

    This study demonstrates the first application of field-induced wooden-tip electrospray ionization (ESI) mass spectrometry (MS) for high-throughput analysis of herbal medicines. By application of an opposite and sample-contactless high voltage on the MS inlet rather than wooden tips, a high-throughput analysis device is easily set up, and a relatively fast analysis speed of 6 s per sample was successfully achieved. In addition, fast polarity switching between positive and negative ion detection mode is readily accomplished, which provides more complete chemical information for quality assessment and control of herbal medicines. By using the proposed method, various active ingredients present in different herbal medicines were rapidly detected, and the obtained mass spectra were served as the samples' fingerprints for tracing the origins, establishing the authenticity, and assessing the quality consistency and stability of herbal medicines. Our experimental results demonstrated that field-induced wooden-tip ESI-MS is a desirable method for high-throughput analysis of herbal medicines, with promising prospects for rapidly differentiating the origin, determining the authenticity, and assessing the overall quality of pharmaceuticals. PMID:26320794

  11. Rapid evaluation of a protein-based voltage probe using a field-induced membrane potential change.

    PubMed

    Tsutsui, Hidekazu; Jinno, Yuka; Tomita, Akiko; Okamura, Yasushi

    2014-07-01

    The development of a high performance protein probe for the measurement of membrane potential will allow elucidation of spatiotemporal regulation of electrical signals within a network of excitable cells. Engineering such a probe requires a functional screen of many candidates. Although the glass-microelectrode technique generally provides an accurate measure of a given test probe, throughputs are limited. In this study, we focused on an approach that uses the membrane potential changes induced by an external electric field in a geometrically simple mammalian cell. For quantitative evaluation of membrane voltage probes that rely on the structural transition of the S1-S4 voltage sensor domain and hence have non-linear voltage dependencies, it was crucial to introduce exogenous inwardly rectifying potassium conductance to reduce cell-to-cell variability in resting membrane potentials. Importantly, the addition of the exogenous conductance drastically altered the profile of the field-induced potential. Following a site-directed random mutagenesis and the rapid screen, we identified a mutant of a voltage probe Mermaid, exhibiting positively shifted voltage sensitivity. Due to its simplicity, the current approach will be applicable under a microfluidic configuration to carry out an efficient screen. Additionally, we demonstrate another interesting aspect of the field-induced optical signals, ability to visualize electrical couplings between cells. PMID:24642225

  12. Extreme sensitivity of the electric-field-induced band gap to the electronic topological transition in sliding bilayer graphene

    PubMed Central

    Lee, Kyu Won; Lee, Cheol Eui

    2015-01-01

    We have investigated the effect of electronic topological transition on the electric field-induced band gap in sliding bilayer graphene by using the density functional theory calculations. The electric field-induced band gap was found to be extremely sensitive to the electronic topological transition. At the electronic topological transition induced by layer sliding, four Dirac cones in the Bernal-stacked bilayer graphene reduces to two Dirac cones with equal or unequal Dirac energies depending on the sliding direction. While the critical electric field required for the band gap opening increases with increasing lateral shift for the two Dirac cones with unequal Dirac energies, the critical field is essentially zero with or without a lateral shift for the two Dirac cones with equal Dirac energies. The critical field is determined by the Dirac energy difference and the electronic screening effect. The electronic screening effect was also found to be enhanced with increasing lateral shift, apparently indicating that the massless helical and massive chiral fermions are responsible for the perfect and imperfect electronic screening, respectively. PMID:26635178

  13. Electric-field-induced paraelectric to ferroelectric phase transformation in prototypical polycrystalline BaTiO{sub 3}

    SciTech Connect

    Wang, Zhiyang; Hinterstein, Manuel; Daniels, John E.; Webber, Kyle G.; Hudspeth, Jessica M.

    2014-10-20

    An electric-field-induced paraelectric cubic to ferroelectric tetragonal phase transformation has been directly observed in prototypical polycrystalline BaTiO{sub 3} at temperatures above the Curie point (T{sub C}) using in situ high-energy synchrotron X-ray diffraction. The transformation persisted to a maximum temperature of 4 °C above T{sub C}. The nature of the observed field-induced transformation and the resulting development of domain texture within the induced phase were dependent on the proximity to the transition temperature, corresponding well to previous macroscopic measurements. The transition electric field increased with increasing temperature above T{sub C}, while the magnitude of the resultant tetragonal domain texture at the maximum electric field (4 kV mm{sup −1}) decreased at higher temperatures. These results provide insights into the phase transformation behavior of a prototypical ferroelectric and have important implications for the development of future large-strain phase-change actuator materials.

  14. Electric-field-induced AFE-FE transitions and associated strain/preferred orientation in antiferroelectric PLZST

    PubMed Central

    Lu, Teng; Studer, Andrew J.; Noren, Lasse; Hu, Wanbiao; Yu, Dehong; McBride, Bethany; Feng, Yujun; Withers, Ray L.; Chen, Hua; Xu, Zhuo; Liu, Yun

    2016-01-01

    Electric-field-induced, antiferroelectric-ferroelectric (AFE-FE) phase transitions are common for AFE materials. To date, the strain and preferred orientation evolution as well as the role of the intermediate FE state during the successive AFE-FE-AFE phase transitions has not been clear. To this end, we have herein studied a typical AFE Pb0.97La0.02(Zr0.56Sn0.33Ti0.11)O3 (PLZST) material using in-situ neutron diffraction. It is striking that the AFE-FE phase transition is not fully reversible: in the electric-field-induced FE state, the induced strain exhibits an elliptical distribution, which in turn leads to significant preferred orientation in the final AFE state after withdrawal of the applied electric-field. The ω-dependent neutron diffraction patterns show clear evidence of the induced strain distribution and associated preferred orientation arising from the AFE-FE phase transition. The current work also provides an explanation for several temperature and electric-field dependent dielectric anomalies as well as unrecovered strain change which appear in AFE materials after exposure to sufficiently high electric fields. PMID:27025685

  15. Nanoscale magnetization reversal caused by electric field-induced ion migration and redistribution in cobalt ferrite thin films.

    PubMed

    Chen, Xinxin; Zhu, Xiaojian; Xiao, Wen; Liu, Gang; Feng, Yuan Ping; Ding, Jun; Li, Run-Wei

    2015-04-28

    Reversible nanoscale magnetization reversal controlled merely by electric fields is still challenging at the moment. In this report, first-principles calculation indicates that electric field-induced magnetization reversal can be achieved by the appearance of unidirectional magnetic anisotropy along the (110) direction in Fe-deficient cobalt ferrite (CoFe(2-x)O4, CFO), as a result of the migration and local redistribution of the Co(2+) ions adjacent to the B-site Fe vacancies. In good agreement with the theoretical model, we experimentally observed that in the CFO thin films the nanoscale magnetization can be reversibly and nonvolatilely reversed at room temperature via an electrical ion-manipulation approach, wherein the application of electric fields with appropriate polarity and amplitude can modulate the size of magnetic domains with different magnetizations up to 70%. With the low power consumption (subpicojoule) characteristics and the elimination of external magnetic field, the observed electric field-induced magnetization reversal can be used for the construction of energy-efficient spintronic devices, e.g., low-power electric-write and magnetic-read memories. PMID:25794422

  16. Electric-field-induced AFE-FE transitions and associated strain/preferred orientation in antiferroelectric PLZST.

    PubMed

    Lu, Teng; Studer, Andrew J; Noren, Lasse; Hu, Wanbiao; Yu, Dehong; McBride, Bethany; Feng, Yujun; Withers, Ray L; Chen, Hua; Xu, Zhuo; Liu, Yun

    2016-01-01

    Electric-field-induced, antiferroelectric-ferroelectric (AFE-FE) phase transitions are common for AFE materials. To date, the strain and preferred orientation evolution as well as the role of the intermediate FE state during the successive AFE-FE-AFE phase transitions has not been clear. To this end, we have herein studied a typical AFE Pb0.97La0.02(Zr0.56Sn0.33Ti0.11)O3 (PLZST) material using in-situ neutron diffraction. It is striking that the AFE-FE phase transition is not fully reversible: in the electric-field-induced FE state, the induced strain exhibits an elliptical distribution, which in turn leads to significant preferred orientation in the final AFE state after withdrawal of the applied electric-field. The ω-dependent neutron diffraction patterns show clear evidence of the induced strain distribution and associated preferred orientation arising from the AFE-FE phase transition. The current work also provides an explanation for several temperature and electric-field dependent dielectric anomalies as well as unrecovered strain change which appear in AFE materials after exposure to sufficiently high electric fields. PMID:27025685

  17. Magnetic-field-induced effects in the electronic structure of itinerant d- and f-metal systems

    NASA Astrophysics Data System (ADS)

    Grechnev, G. E.

    2009-08-01

    A paramagnetic response of transition metals and itinerant d- and f-metal compounds in an external magnetic field is studied by employing ab initio full-potential LMTO method in the framework of the local spin density approximation. Within this method the anisotropy of the magnetic susceptibility in hexagonal close-packed transition metals is evaluated for the first time. This anisotropy is owing to the orbital Van Vleck-like paramagnetic susceptibility, which is revealed to be substantial in transition-metal systems due to hybridization effects in the electronic structure. It is demonstrated that compounds TiCo, Ni3Al, YCo2, CeCo2, YNi5, LaNi5, and CeNi5 are strong paramagnets close to the quantum critical point. For these systems the Stoner approximation underestimates the spin susceptibility, whereas the calculated field-induced spin moments provide a good description of the large paramagnetic susceptibilities and magnetovolume effects. It is revealed that an itinerant description of hybridized f electrons produces magnetic properties of the compounds CeCo2, CeNi5, UAl3, UGa3, USi3, and UGe3 in close agreement with experiment. In the uranium compounds UX3 the strong spin-orbit coupling together with hybridization effects give rise to peculiar magnetic states in which the field-induced spin moments are antiparallel to the external field, and the magnetic response is dominated by the orbital contribution.

  18. A HIGH SPATIAL RESOLUTION STUDY OF THE {lambda} = 3 mm CONTINUUM OF ORION-KL

    SciTech Connect

    Friedel, D. N.; Widicus Weaver, S. L. E-mail: susanna.widicus.weaver@emory.edu

    2011-12-01

    Recent interferometric observations have called into question the traditional view of the Orion-KL region, which displays one of the most well-defined cases of chemical differentiation in a star-forming region. Previous lower-resolution images of Orion-KL show emission signatures for oxygen-bearing organic molecules toward the Orion Compact Ridge and emission for nitrogen-bearing organic molecules toward the Orion Hot Core. However, more recent observations at higher spatial resolution indicate that the bulk of the molecular emission arises from many smaller, compact clumps that are spatially distinct from the traditional Hot Core and Compact Ridge sources. It is this type of observational information that is critical for guiding astrochemical models, as the spatial distribution of molecules and their relation to energetic sources will govern the chemical mechanisms at play in star-forming regions. We have conducted millimeter-imaging studies of Orion-KL with various beam sizes using the Combined Array for Research in Millimeter-Wave Astronomy in order to investigate the continuum structure. These {lambda} = 3 mm observations have synthesized beam sizes of {approx}0.''5-5.''0. These observations reveal the complex continuum structure of this region, which stands in sharp contrast to the previous structural models assumed for Orion-KL based on lower spatial resolution images. The new results indicate that the spatial scaling previously used in determination of molecular abundances for this region are in need of complete revision. Here we present the results of the continuum observations, discuss the sizes and structures of the detected sources, and suggest an observational strategy for determining the proper spatial scaling to accurately determine molecular abundances in the Orion-KL region.

  19. PACCE: Perl Algorithm to Compute Continuum and Equivalent Widths

    NASA Astrophysics Data System (ADS)

    Riffel, Rogério; Borges Vale, Tibério

    2011-05-01

    We present Perl Algorithm to Compute continuum and Equivalent Widths (pacce). We describe the methods used in the computations and the requirements for its usage. We compare the measurements made with pacce and "manual" ones made using iraf splot task. These tests show that for SSP models the equivalent widths strengths are very similar (differences <0.2A) for both measurements. In real stellar spectra, the correlation between both values is still very good, but with differences of up to 0.5A. pacce is also able to determine mean continuum and continuum at line center values, which are helpful in stellar population studies. In addition, it is also able to compute the uncertainties in the equivalent widths using photon statistics.

  20. Quasiparticle-continuum level repulsion in a quantum magnet

    DOE PAGESBeta

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

    2015-11-30

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

  1. Water vapor continuum: Whether collision-induced absorption is involved?

    NASA Astrophysics Data System (ADS)

    Vigasin, A. A.

    2014-11-01

    In a series of recent publications, the idea is pursued to shed a new light on the theory of the water vapor continuum absorption invoking the mechanism of collision-induced absorption. In the opinion of the present author, a portion of theoretical suggestions on this subject is biased and may thus lead to untenable conclusions about the nature of the continuum. The most typical drawback consists of improper consideration of statistics in the ensemble of interacting monomers that lead to embedding incorrect statistical weights to various types of molecular pairs which can form. The current note aims at clarifying the term “collision-induced absorption” in order to avoid incongruity in understanding the nature of the water vapor continuum.

  2. The wetland continuum: a conceptual framework for interpreting biological studies

    USGS Publications Warehouse

    Euliss, N.H., Jr.; LaBaugh, J.W.; Fredrickson, L.H.; Mushet, D.M.; Swanson, G.A.; Winter, T.C.; Rosenberry, D.O.; Nelson, R.D.

    2004-01-01

    We describe a conceptual model, the wetland continuum, which allows wetland managers, scientists, and ecologists to consider simultaneously the influence of climate and hydrologic setting on wetland biological communities. Although multidimensional, the wetland continuum is most easily represented as a two-dimensional gradient, with ground water and atmospheric water constituting the horizontal and vertical axis, respectively. By locating the position of a wetland on both axes of the continuum, the potential biological expression of the wetland can be predicted at any point in time. The model provides a framework useful in the organization and interpretation of biological data from wetlands by incorporating the dynamic changes these systems undergo as a result of normal climatic variation rather than placing them into static categories common to many wetland classification systems. While we developed this model from the literature available for depressional wetlands in the prairie pothole region of North America, we believe the concept has application to wetlands in many other geographic locations.

  3. Quasiparticle-continuum level repulsion in a quantum magnet

    SciTech Connect

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

    2015-11-30

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

  4. A polarizable continuum model for molecules at spherical diffuse interfaces

    NASA Astrophysics Data System (ADS)

    Di Remigio, Roberto; Mozgawa, Krzysztof; Cao, Hui; Weijo, Ville; Frediani, Luca

    2016-03-01

    We present an extension of the Polarizable Continuum Model (PCM) to simulate solvent effects at diffuse interfaces with spherical symmetry, such as nanodroplets and micelles. We derive the form of the Green's function for a spatially varying dielectric permittivity with spherical symmetry and exploit the integral equation formalism of the PCM for general dielectric environments to recast the solvation problem into a continuum solvation framework. This allows the investigation of the solvation of ions and molecules in nonuniform dielectric environments, such as liquid droplets, micelles or membranes, while maintaining the computationally appealing characteristics of continuum solvation models. We describe in detail our implementation, both for the calculation of the Green's function and for its subsequent use in the PCM electrostatic problem. The model is then applied on a few test systems, mainly to analyze the effect of interface curvature on solvation energetics.

  5. Quasiparticle-continuum level repulsion in a quantum magnet

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  6. Micropolar continuum modelling of bi-dimensional tetrachiral lattices

    PubMed Central

    Chen, Y.; Liu, X. N.; Hu, G. K.; Sun, Q. P.; Zheng, Q. S.

    2014-01-01

    The in-plane behaviour of tetrachiral lattices should be characterized by bi-dimensional orthotropic material owing to the existence of two orthogonal axes of rotational symmetry. Moreover, the constitutive model must also represent the chirality inherent in the lattices. To this end, a bi-dimensional orthotropic chiral micropolar model is developed based on the theory of irreducible orthogonal tensor decomposition. The obtained constitutive tensors display a hierarchy structure depending on the symmetry of the underlying microstructure. Eight additional material constants, in addition to five for the hemitropic case, are introduced to characterize the anisotropy under Z2 invariance. The developed continuum model is then applied to a tetrachiral lattice, and the material constants of the continuum model are analytically derived by a homogenization process. By comparing with numerical simulations for the discrete lattice, it is found that the proposed continuum model can correctly characterize the static and wave properties of the tetrachiral lattice. PMID:24808754

  7. Quantum state transfer by time reversal in the continuum

    NASA Astrophysics Data System (ADS)

    Longhi, S.

    2016-03-01

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

  8. Mechanosensitive Channels: Insights from Continuum-Based Simulations

    PubMed Central

    Tang, Yuye; Yoo, Jejoong; Yethiraj, Arun; Cui, Qiang; Chen, Xi

    2009-01-01

    Mechanotransduction plays an important role in regulating cell functions and it is an active topic of research in biophysics. Despite recent advances in experimental and numerical techniques, the intrinsic multiscale nature imposes tremendous challenges for revealing the working mechanisms of mechanosensitive channels. Recently, a continuum-mechanics based hierarchical modeling and simulation framework has been established and applied to study the mechanical responses and gating behaviors of a prototypical mechanosensitive channel, the mechanosensitive channel of large conductance (MscL) in bacteria Escherichia coli (E. coli), from which several putative gating mechanisms have been tested and new insights deduced. This article reviews these latest findings using the continuum mechanics framework and suggests possible improvements for future simulation studies. This computationally efficient and versatile continuum-mechanics based protocol is poised to make contributions to the study of a variety of mechanobiology problems. PMID:18787764

  9. A polarizable continuum model for molecules at spherical diffuse interfaces.

    PubMed

    Di Remigio, Roberto; Mozgawa, Krzysztof; Cao, Hui; Weijo, Ville; Frediani, Luca

    2016-03-28

    We present an extension of the Polarizable Continuum Model (PCM) to simulate solvent effects at diffuse interfaces with spherical symmetry, such as nanodroplets and micelles. We derive the form of the Green's function for a spatially varying dielectric permittivity with spherical symmetry and exploit the integral equation formalism of the PCM for general dielectric environments to recast the solvation problem into a continuum solvation framework. This allows the investigation of the solvation of ions and molecules in nonuniform dielectric environments, such as liquid droplets, micelles or membranes, while maintaining the computationally appealing characteristics of continuum solvation models. We describe in detail our implementation, both for the calculation of the Green's function and for its subsequent use in the PCM electrostatic problem. The model is then applied on a few test systems, mainly to analyze the effect of interface curvature on solvation energetics. PMID:27036423

  10. External magnetic field-induced selective biodistribution of magnetoliposomes in mice

    NASA Astrophysics Data System (ADS)

    García-Jimeno, Sonia; Escribano, Elvira; Queralt, Josep; Estelrich, Joan

    2012-08-01

    This study looked at the effect of an external magnet on the biodistribution of magnetoliposomes intravenously administrated in mice (8 mg iron/kg) with and without induced acute inflammation. Our results showed that due to enhanced vascular permeability, magnetoliposomes accumulated at the site of inflammation in the absence of an external magnetic field, but the amount of iron present increased under the effect of a magnet located at the inflammation zone. This increase was dependent on the time (20 or 60 min) of exposure of the external magnetic field. It was also observed that the presence of the magnet was associated with lower amounts of iron in the liver, spleen, and plasma than was found in mice in which a magnet had not been applied. The results of this study confirm that it is possible to target drugs encapsulated in magnetic particles by means of an external magnet.

  11. External magnetic field-induced selective biodistribution of magnetoliposomes in mice

    PubMed Central

    2012-01-01

    This study looked at the effect of an external magnet on the biodistribution of magnetoliposomes intravenously administrated in mice (8 mg iron/kg) with and without induced acute inflammation. Our results showed that due to enhanced vascular permeability, magnetoliposomes accumulated at the site of inflammation in the absence of an external magnetic field, but the amount of iron present increased under the effect of a magnet located at the inflammation zone. This increase was dependent on the time (20 or 60 min) of exposure of the external magnetic field. It was also observed that the presence of the magnet was associated with lower amounts of iron in the liver, spleen, and plasma than was found in mice in which a magnet had not been applied. The results of this study confirm that it is possible to target drugs encapsulated in magnetic particles by means of an external magnet. PMID:22883385

  12. Magnetic Field Induced Shear Flow in a Strongly Coupled Complex Plasma

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, P.; Konopka, U.; Jiang, K.; Morfill, G.

    2011-11-01

    We address an experimental observation of shear flow of micron sized dust particles in a strongly coupled complex plasma in presence of a homogeneous magnetic field. Two concentric Aluminum rings of different size are placed on the lower electrode of a radio frequency (rf) parallel plate discharge. The modified local sheath electric field is pointing outward/inward close to the inner/outher ring, respectively. The microparticles, confined by the rings and subject to an ion wind that driven by the local sheath electric field and deflected by an externally applied magnetic field, start flowing in azimuthal direction. Depending upon the rf amplitudes on the electrodes, the dust layers show rotation in opposite direction at the edges of the ring-shaped cloud resulting a strong shear in its center. MD simulations shows a good agreement with the experimental results.

  13. Field-induced dielectric response saturation in o-TaS3.

    PubMed

    Ma, Yongchang; Lu, Cuimin; Wang, Xuewei; Du, Xueli; Li, Lijun; Petrovic, Cedomir

    2016-10-01

    We investigated dependence of the dielectric properties on temperature and electric field below 50 K along the chain direction of o-TaS3. With external electric field increase, two threshold features could be identified. For electric fields somewhat larger than the lower threshold [Formula: see text], the dielectric constant starts to decrease whereas the conductivity increases due to the tunnelling of solitons. For higher external electric field we observe a saturation of dielectric response and analyze that the possible reasons may be related to the polarization behavior of charged solitons. With a decrease in temperature, the effect of external field on the dielectric response of the system weakens gradually and at 13 K it diminishes due to soliton freezing. PMID:27485146

  14. Fringing field-induced monodomain of a polymer-stabilized blue phase liquid crystal

    NASA Astrophysics Data System (ADS)

    Li, Wei-Huan; Hu, De-Chun; Li, Yan; Chen, Chao Ping; Lee, Yung-Jui; Lien, Alan; Lu, Jian-Gang; Su, Yikai

    2015-12-01

    The influence of fringe electric field applied during photopolymerization on the electro-optic properties of polymer-stabilized blue phase liquid crystals (PS-BPLCs) was investigated. It has been found that the thermal stability would not degrade if the electric field was less than a critical value. The contrast ratio of PS-BPLC can be improved significantly because the uniformity of blue phase liquid crystal domain was enhanced by the electric fields, which were applied during photopolymerization. Meanwhile, with the electric filed, the potential energy of the BPLC molecules may lower the anchoring energy of the polymer network resulting in the improvement of electro-optic response properties. With optimized electric field during polymerization, the contrast ratio and the Kerr constant of PS-BPLC can be improved by 4.1 times and 15%, respectively, and the hysteresis can be decreased by 10%, while the response time and residual birefringence have no degradation.

  15. Temperature and Field Induced Strain Measurements in Single Crystal Gd5Si2Ge2

    NASA Astrophysics Data System (ADS)

    McCall, S. K.; Nersessian, N.; Carman, G. P.; Pecharsky, V. K.; Schlagel, D. L.; Radousky, H. B.

    2016-06-01

    The first-order magneto-structural transformation that occurs in Gd5Si2Ge2 near room temperature makes it a strong candidate for many energy harvesting applications. Understanding the single crystal properties is crucial for allowing simulations of device performance. In this study, magnetically and thermally induced transformation strains were measured in a single crystal of Gd5Si2.05Ge1.95 as it transforms from a high-temperature monoclinic paramagnet to a lower-temperature orthorhombic ferromagnet. Thermally induced transformation strains of -8500 ppm, +960 ppm and +1800 ppm, and magnetically induced transformation strains of -8500 ppm, +900 ppm and +2300 ppm were measured along the a, b and c axes, respectively. Using experimental data coupled with general thermodynamic considerations, a universal phase diagram was constructed showing the transition from the monoclinic to the orthorhombic phase as a function of temperature and magnetic field.

  16. Continuum Polarizable Force Field within the Poisson-Boltzmann Framework

    PubMed Central

    Tan, Yu-Hong; Tan, Chunhu; Wang, Junmei; Luo, Ray

    2008-01-01

    We have developed and tested a complete set of nonbonded parameters for a continuum polarizable force field. Our analysis shows that the new continuum polarizable model is consistent with B3LYP/cc-pVTZ in modeling electronic response upon variation of dielectric environment. Comparison with experiment also shows that the new continuum polarizable model is reasonable, with similar accuracy as B3LYP/cc-pVTZ in reproduction of dipole moments of selected organic molecules in the gas phase. We have further tested the validity to interchange the Amber van der Waals parameters between the explicit and continuum polarizable force fields with a series of dimers. It can be found that the continuum polarizable model agrees well with MP2/cc-pVTZ, with deviations in dimer binding energies less than 0.9 kcal/mol in the aqueous dielectric environment. Finally we have optimized atomic cavity radii with respect to experimental solvation free energies of 177 training molecules. To validate the optimized cavity radii, we have tested these parameters against 176 test molecules. It is found that the optimized PB atomic cavity radii transfer well from the training set to the test set, with an overall root-mean-squared deviation of 1.30 kcal/mol, unsigned average error of 1.07 kacl/mol, and correlation coefficient of 92% for all 353 molecules in both the training and test sets. Given the development documented here, the next natural step is the construction of a full protein/nucleic acid force field within the new continuum polarization framework. PMID:18507452

  17. FUV Continuum in Flare Kernels Observed by IRIS

    NASA Astrophysics Data System (ADS)

    Daw, Adrian N.; Kowalski, Adam; Allred, Joel C.; Cauzzi, Gianna

    2016-05-01

    Fits to Interface Region Imaging Spectrograph (IRIS) spectra observed from bright kernels during the impulsive phase of solar flares are providing long-sought constraints on the UV/white-light continuum emission. Results of fits of continua plus numerous atomic and molecular emission lines to IRIS far ultraviolet (FUV) spectra of bright kernels are presented. Constraints on beam energy and cross sectional area are provided by cotemporaneous RHESSI, FERMI, ROSA/DST, IRIS slit-jaw and SDO/AIA observations, allowing for comparison of the observed IRIS continuum to calculations of non-thermal electron beam heating using the RADYN radiative-hydrodynamic loop model.

  18. Diffuse Galactic low energy gamma ray continuum emission

    NASA Technical Reports Server (NTRS)

    Skibo, J. G.; Ramaty, R.

    1993-01-01

    We investigate the origin of diffuse low-energy Galactic gamma-ray continuum down to about 30 keV. We calculate gamma-ray emission via bremsstrahlung and inverse Compton scattering by propagating an unbroken electron power law injection spectrum and employing a Galactic emmissivity model derived from COSB observations. To maintain the low energy electron population capable of producing the observed continuum via bremsstrahlung, a total power input of 4 x 10 exp 41 erg/s is required. This exceeds the total power supplied to the nuclear cosmic rays by about an order of magnitude.

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  20. Improving the Capabilities of a Continuum Laser Plasma Interaction Code

    SciTech Connect

    Hittinger, J F; Dorr, M R

    2006-06-15

    The numerical simulation of plasmas is a critical tool for inertial confinement fusion (ICF). We have been working to improve the predictive capability of a continuum laser plasma interaction code pF3d, which couples a continuum hydrodynamic model of an unmagnetized plasma to paraxial wave equations modeling the laser light. Advanced numerical techniques such as local mesh refinement, multigrid, and multifluid Godunov methods have been adapted and applied to nonlinear heat conduction and to multifluid plasma models. We describe these algorithms and briefly demonstrate their capabilities.

  1. Manipulability, force, and compliance analysis for planar continuum manipulators.

    PubMed

    Gravagne, Ian A; Walker, Ian D

    2002-06-01

    Continuum manipulators, inspired by the natural capabilities of elephant trunks and octopus tentacles, may find niche applications in areas like human-robot interaction, multiarm manipulation, and unknown environment exploration. However, their true capabilities will remain largely inaccessible without proper analytical tools to evaluate their unique properties. Ellipsoids have long served as one of the foremost analytical tools available to the robotics researcher, and the purpose of this paper is to first formulate, and then to examine, three types of ellipsoids for continuum robots: manipulability, force, and compliance. PMID:12492083

  2. Coherent Detector Arrays for Continuum and Spectral Line Applications

    NASA Technical Reports Server (NTRS)

    Gaier, Todd C.

    2006-01-01

    This viewgraph presentation reviews the requirements for improved coherent detector arrays for use in continuum and spectral line applications. With detectors approaching fundamental limits, large arrays offer the only path to sensitivity improvement. Monolithic Microwave Integrated Circuit (MMIC) technology offers a straightforward path to massive focal plane millimeter wave arrays: The technology will readily support continuum imagers, polarimeters and spectral line receivers from 30-110 GHz. Science programs, particularly large field blind surveys will benefit from simultaneous observations of hundreds or thousands of pixels 1000 element array is competitive with a cost less than $2M.

  3. Manipulability, force, and compliance analysis for planar continuum manipulators

    NASA Technical Reports Server (NTRS)

    Gravagne, Ian A.; Walker, Ian D.

    2002-01-01

    Continuum manipulators, inspired by the natural capabilities of elephant trunks and octopus tentacles, may find niche applications in areas like human-robot interaction, multiarm manipulation, and unknown environment exploration. However, their true capabilities will remain largely inaccessible without proper analytical tools to evaluate their unique properties. Ellipsoids have long served as one of the foremost analytical tools available to the robotics researcher, and the purpose of this paper is to first formulate, and then to examine, three types of ellipsoids for continuum robots: manipulability, force, and compliance.

  4. Lower Eyelid Reconstruction.

    PubMed

    Holds, John B

    2016-05-01

    Lower eyelid defects are common, and a systematic approach to reconstruction of the lower eyelid is required. Attention to the bilaminar eyelid anatomy and canthal support structures, with efforts to maintain functionally important structures, such as the lacrimal canalicular system, is vital to appropriate lower eyelid reconstruction. Techniques of advancement and rotation flaps and grafting of skin and mucosa are mainstays of lower eyelid reconstruction. An appropriate armamentarium of techniques allows for optimal surgical results. PMID:27105804

  5. Velocity profiles of electric-field-induced backflows in liquid crystals confined between parallel plates

    NASA Astrophysics Data System (ADS)

    Tsuji, Tomohiro; Chono, Shigeomi; Matsumi, Takanori

    2015-02-01

    For the purpose of developing liquid crystalline microactuators, we visualize backflows induced between two parallel plates for various parameters such as the twist angle, cell gap, applied voltage, and molecular configuration mode. We use 4-cyano-4'-pentyl biphenyl, a typical low-molar-mass nematic liquid crystal. By increasing the twist angle from 0° to 180°, the velocity component parallel to the anchoring direction of the lower plate changes from an S-shaped profile to a distorted S-shaped profile before finally becoming unidirectional. In contrast, the velocity component perpendicular to the anchoring direction evolves from a flat profile at 0° into an S-shaped profile at 180°. Because both an increase in the applied voltage and a decrease in the cell gap increase the electric field intensity, the backflow becomes large. The hybrid molecular configuration mode induces a larger backflow than that for the planar aligned mode. The backflow develops in two stages: an early stage with a microsecond time scale and a later stage with a millisecond time scale. The numerical predictions are in qualitative agreement with the measurements, but not quantitative agreement because our computation ignores the plate edge effect of surface tension.

  6. Localized electric field induced transition and miniaturization of two-phase flow patterns inside microchannels.

    PubMed

    Sharma, Abhinav; Tiwari, Vijeet; Kumar, Vineet; Mandal, Tapas Kumar; Bandyopadhyay, Dipankar

    2014-10-01

    Strategic application of external electrostatic field on a pressure-driven two-phase flow inside a microchannel can transform the stratified or slug flow patterns into droplets. The localized electrohydrodynamic stress at the interface of the immiscible liquids can engender a liquid-dielectrophoretic deformation, which disrupts the balance of the viscous, capillary, and inertial forces of a pressure-driven flow to engender such flow morphologies. Interestingly, the size, shape, and frequency of the droplets can be tuned by varying the field intensity, location of the electric field, surface properties of the channel or fluids, viscosity ratio of the fluids, and the flow ratio of the phases. Higher field intensity with lower interfacial tension is found to facilitate the oil droplet formation with a higher throughput inside the hydrophilic microchannels. The method is successful in breaking down the regular pressure-driven flow patterns even when the fluid inlets are exchanged in the microchannel. The simulations identify the conditions to develop interesting flow morphologies, such as (i) an array of miniaturized spherical or hemispherical or elongated oil drops in continuous water phase, (ii) "oil-in-water" microemulsion with varying size and shape of oil droplets. The results reported can be of significance in improving the efficiency of multiphase microreactors where the flow patterns composed of droplets are preferred because of the availability of higher interfacial area for reactions or heat and mass exchange. PMID:25044128

  7. Temperature and field induced strain measurements in single crystal Gd5Si2Ge2

    DOE PAGESBeta

    McCall, S. K.; Nersessian, N.; Carman, G. P.; Pecharsky, V. K.; Schlagel, D. L.; Radousky, H. B.

    2016-03-29

    The first-order magneto-structural transformation that occurs in Gd5Si2Ge2 near room temperature makes it a strong candidate for many energy harvesting applications. Understanding the single crystal properties is crucial for allowing simulations of device performance. In this study, magnetically and thermally induced transformation strains were measured in a single crystal of Gd5Si2.05Ge1.95 as it transforms from a high-temperature monoclinic paramagnet to a lower-temperature orthorhombic ferromagnet. Thermally induced transformation strains of –8500 ppm, +960 ppm and +1800 ppm, and magnetically induced transformation strains of –8500 ppm, +900 ppm and +2300 ppm were measured along the a, b and c axes, respectively. Furthermore,more » using experimental data coupled with general thermodynamic considerations, a universal phase diagram was constructed showing the transition from the monoclinic to the orthorhombic phase as a function of temperature and magnetic field.« less

  8. High Magnetic Field-Induced Formation of Banded Microstructures in Lamellar Eutectic Alloys During Directional Solidification

    NASA Astrophysics Data System (ADS)

    Li, Xi; Fautrelle, Yves; Gagnoud, Annie; Ren, Zhongming; Moreau, Rene

    2016-06-01

    The influences of high magnetic field (up to 12 T) on the morphology of Pb-Sn and Al-Al2Cu lamellar eutectics during directional solidification were investigated. The experimental results indicate that, along with a decrease in eutectic spacing, the banded structure forms at lower growth speeds under high magnetic field and the band spacing decreases as the magnetic field increases. Moreover, the application of a magnetic field enriches the Cu solute in the liquid ahead of the liquid/solid interface during directional solidification of an Al-Al2Cu eutectic alloy. The effects of high magnetic field on the eutectic points of non-ferromagnetic alloys and the stress acting on the eutectic lamellae during directional solidification have been studied. Both thermodynamic evaluation and DTA measurements reveal that the high magnetic field has a negligible effect on the eutectic points of non-ferromagnetic alloys. However, the high magnetic field caused an increase of the nucleation temperature and undercooling. The numerical results indicate that a considerable stress is produced on the eutectic lamellae during directional solidification under high magnetic field. The formation of a banded structure in a lamellar eutectic during directional solidification under high magnetic field may be attributed to both the buildup of the solute in the liquid ahead of the liquid/solid interface and the stress acting on the eutectic lamellae.

  9. High Magnetic Field-Induced Formation of Banded Microstructures in Lamellar Eutectic Alloys During Directional Solidification

    NASA Astrophysics Data System (ADS)

    Li, Xi; Fautrelle, Yves; Gagnoud, Annie; Ren, Zhongming; Moreau, Rene

    2016-08-01

    The influences of high magnetic field (up to 12 T) on the morphology of Pb-Sn and Al-Al2Cu lamellar eutectics during directional solidification were investigated. The experimental results indicate that, along with a decrease in eutectic spacing, the banded structure forms at lower growth speeds under high magnetic field and the band spacing decreases as the magnetic field increases. Moreover, the application of a magnetic field enriches the Cu solute in the liquid ahead of the liquid/solid interface during directional solidification of an Al-Al2Cu eutectic alloy. The effects of high magnetic field on the eutectic points of non-ferromagnetic alloys and the stress acting on the eutectic lamellae during directional solidification have been studied. Both thermodynamic evaluation and DTA measurements reveal that the high magnetic field has a negligible effect on the eutectic points of non-ferromagnetic alloys. However, the high magnetic field caused an increase of the nucleation temperature and undercooling. The numerical results indicate that a considerable stress is produced on the eutectic lamellae during directional solidification under high magnetic field. The formation of a banded structure in a lamellar eutectic during directional solidification under high magnetic field may be attributed to both the buildup of the solute in the liquid ahead of the liquid/solid interface and the stress acting on the eutectic lamellae.

  10. Instability Resistance Training Across the Exercise Continuum

    PubMed Central

    Behm, David G.; Colado Sanchez, Juan Carlos

    2013-01-01

    Context: Instability resistance training (IRT; unstable surfaces and devices to strengthen the core or trunk muscles) is popular in fitness training facilities. Objective: To examine contradictory IRT recommendations for health enthusiasts and rehabilitation. Data Sources: A literature search was performed using MEDLINE, SPORT Discus, ScienceDirect, Web of Science, and Google Scholar databases from 1990 to 2012. Study Selection: Databases were searched using key terms, including “balance,” “stability,” “instability,” “resistance training,” “core,” “trunk,” and “functional performance.” Additionally, relevant articles were extracted from reference lists. Data Extraction: To be included, research questions addressed the effect of balance or IRT on performance, healthy and active participants, and physiologic or performance outcome measures and had to be published in English in a peer-reviewed journal. Results: There is a dichotomy of opinions on the effectiveness and application of instability devices and conditions for health and performance training. Balance training without resistance has been shown to improve not only balance but functional performance as well. IRT studies document similar training adaptations as stable resistance training programs with recreationally active individuals. Similar progressions with lower resistance may improve balance and stability, increase core activation, and improve motor control. Conclusion: IRT is highly recommended for youth, elderly, recreationally active individuals, and highly trained enthusiasts. PMID:24427423

  11. A matrix lower bound

    SciTech Connect

    Grcar, Joseph F.

    2002-02-04

    A matrix lower bound is defined that generalizes ideas apparently due to S. Banach and J. von Neumann. The matrix lower bound has a natural interpretation in functional analysis, and it satisfies many of the properties that von Neumann stated for it in a restricted case. Applications for the matrix lower bound are demonstrated in several areas. In linear algebra, the matrix lower bound of a full rank matrix equals the distance to the set of rank-deficient matrices. In numerical analysis, the ratio of the matrix norm to the matrix lower bound is a condition number for all consistent systems of linear equations. In optimization theory, the matrix lower bound suggests an identity for a class of min-max problems. In real analysis, a recursive construction that depends on the matrix lower bound shows that the level sets of continuously differential functions lie asymptotically near those of their tangents.

  12. Field-induced detrapping in doped organic semiconductors with Gaussian disorder and different carrier localizations on host and guest sites

    NASA Astrophysics Data System (ADS)

    Scheb, M.; Zimmermann, C.; Jungemann, C.

    2015-09-01

    For organic host-guest systems with a low fraction of guest sites, i.e., the trap-limited case, field-induced detrapping of charge carriers is studied via master equation calculations under the assumption of Miller-Abrahams rates and two Gaussian distributions of uncorrelated energy levels. Among existing descriptions of carrier redistributions in the presence of an electric field, the effective temperature derived by F. Jansson, S. D. Baranovskii, F. Gebhard, and R. Österbacka [Phys. Rev. B 77, 195211 (2008), 10.1103/PhysRevB.77.195211] for pure host materials shows the best agreement with the simulation results. The detrapping description based on carrier heating is extended to the case that the two material-specific hopping rate parameters ν0 (attempt frequency) and α (decay constant or inverse localization length of charge carriers) are different for host and guest sites.

  13. Chiral mononuclear lanthanide complexes and the field-induced single-ion magnet behaviour of a Dy analogue.

    PubMed

    Lin, Shuang-Yan; Wang, Chao; Zhao, Lang; Wu, Jianfeng; Tang, Jinkui

    2015-01-01

    Three pairs of homochiral mononuclear lanthanide complexes, with the general formula [LnH4LRRRRRR/SSSSSS(SCN)2](SCN)2·xCH3OH·yH2O(Ln = Dy (R/S-Dy1), Ho (R/S-Ho1) and Er (R/S-Er1)), have been obtained via self-assembly between chiral macrocyclic ligands and the respective thiocyanates, all of which show a saddle-type conformation with seven-coordinated metal ions. Magnetic measurements revealed that the Dy complex shows field-induced single-ion magnet behaviour, which is rarely reported in a seven-coordinated lanthanide-based SIM encapsulated in a macrocyclic ligand. The absolute configuration of all enantiomers was determined by single crystal X-ray crystallography and confirmed by electronic CD and VCD spectra. PMID:25369972

  14. Two field-induced slow magnetic relaxation processes in a mononuclear Co(ii) complex with a distorted octahedral geometry.

    PubMed

    Li, Jing; Han, Yuan; Cao, Fan; Wei, Rong-Min; Zhang, Yi-Quan; Song, You

    2016-05-31

    A distorted octahedral Co(II) complex is reported with homoscorpionate ligands. This complex comprised a field-induced single-molecule magnet, showing two slow relaxation processes under a low dc field (<800 Oe) and only one process under a high dc field (≥800 Oe), which was an unusually discovery for 3d metal ions. On the basis of the ac magnetic data, we show for the first time that one of the slow relaxation processes in the low dc field originates from intermolecular dipolar interactions. Interestingly, the Raman process is predominant in the spin reversal relaxation process. The origin of the behaviours of the complex was elucidated by ab initio calculations. PMID:27180637

  15. Electric-field-induced magnetization switching in CoFeB/MgO magnetic tunnel junctions with high junction resistance

    NASA Astrophysics Data System (ADS)

    Kanai, S.; Matsukura, F.; Ohno, H.

    2016-05-01

    We show the electric-field induced magnetization switching for CoFeB/MgO magnetic tunnel junctions with thick MgO barrier layer of 2.8 nm, whose resistance-area product is 176 kΩ μm2, and achieve the small switching energy of 6.3 fJ/bit. The increase of the junction resistance is expected to suppress the energy consumption due to the Joule heating during the switching; however, the energy is still dominated by the Joule energy rather than the charging energy. This is because the junction resistance decreases more rapidly for junctions with thicker MgO as bias voltage increases.

  16. Large magnetic field-induced work output in a NiMnGa seven-layered modulated martensite

    NASA Astrophysics Data System (ADS)

    Pagounis, E.; Szczerba, M. J.; Chulist, R.; Laufenberg, M.

    2015-10-01

    We report the performance of a Ni-Mn-Ga single crystal with a seven-layered lattice modulation (14M martensite), demonstrating large actuation work output driven by an external magnetic field. A magnetic field-induced strain of 11.2%, a twinning stress of 0.64 MPa, and a magneto-crystalline anisotropy energy of 195 kJ/m3 are measured at room temperature, which exceed the best results reported in Ni-Mn-Ga 14M martensites. The produced magnetically induced work output of about 70 kJ/m3 makes the material attractive for actuator applications. Detailed XRD investigation reveals that the studied 14M martensite is stress-induced. With increasing compression stress, the stress-induced intermartensitic transformation sequence 10M → 14M → NM was demonstrated.

  17. Enantiopure phosphonic acids as chiral inducers: homochiral crystallization of cobalt coordination polymers showing field-induced slow magnetization relaxation.

    PubMed

    Feng, Jian-Shen; Ren, Min; Cai, Zhong-Sheng; Fan, Kun; Bao, Song-Song; Zheng, Li-Min

    2016-05-25

    This Communication reports, for the first time, that enantiopure phosphonic acids can serve as chirality-inducing agents towards homochiral coordination polymers. Hence homochiral chain compounds (M)- or (P)-Co(SO4)(1,3-bbix)(H2O)3 (1M or 1P) are obtained successfully using an achiral precursor of 1,3-bis((1H-benzo[d]imidazol-1-yl)methyl)benzene (1,3-bbix) in the presence of a catalytic amount of (S)- or (R)-3-phenyl-2-((phosphonomethyl)amino)propanoic acid [(S)- or (R)-2-ppapH3]. Furthermore, compound 1M provides the first example of homochiral cobalt compounds showing field-induced single ion magnet behavior. PMID:27108929

  18. Effect of the redox state of QB on electric field-induced charge recombination in Photosystem II.

    PubMed

    Hemelrijk, P W; van Gorkom, H J

    1996-05-01

    Electric field-induced charge recombination in Photosystem II (PS II) was studied in osmotically swollen spinach chloroplasts ('blebs') by measurement of the concomitant chlorophyll luminescence emission (electroluminescence). A pronounced dependence on the redox state of the two-electron gate QB was observed and the earlier failure to detect it is explained. The influence of the QB/QB (-) oscillation on electroluminescence was dependent on the redox state of the oxygen evolving complex; at times around one millisecond after flash illumination a large effect was observed in the states S2 and S3, but not in the state 'S4' (actually Z(+)S3). The presence of the oxidized secondary electron donor, tyrosine Z(+), appeared to prevent expression of the QB/QB (-) effect on electroluminescence, possibly because this effect is primarily due to a shift of the redox equilibrium between Z/Z(+) and the oxygen evolving complex. PMID:24271299

  19. Electric-field-induced spin resonance in antiferromagnetic insulators: Inverse process of the dynamical chiral magnetic effect

    NASA Astrophysics Data System (ADS)

    Sekine, Akihiko; Chiba, Takahiro

    2016-06-01

    We propose a realization of the electric-field-induced antiferromagnetic resonance. We consider three-dimensional antiferromagnetic insulators with spin-orbit coupling characterized by the existence of a topological term called the θ term. By solving the Landau-Lifshitz-Gilbert equation in the presence of the θ term, we show that, in contrast to conventional methods using ac magnetic fields, the antiferromagnetic resonance state is realized by ac electric fields along with static magnetic fields. This mechanism can be understood as the inverse process of the dynamical chiral magnetic effect, an alternating current generation by magnetic fields. In other words, we propose a way to electrically induce the dynamical axion field in condensed matter. We discuss a possible experiment to observe our proposal, which utilizes the spin pumping from the antiferromagnetic insulator into a heavy metal contact.

  20. Electric tuning of magnetization dynamics and electric field-induced negative magnetic permeability in nanoscale composite multiferroics

    NASA Astrophysics Data System (ADS)

    Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng

    2015-06-01

    Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with novel functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. A charge-mediated ME effect is believed to be generally weak and active in only a few angstroms. Here we present an experimental evidence uncovering a new magnon-driven, strong ME effect acting on the nanometer range. For Co92Zr8 (20 nm) film deposited on ferroelectric PMN-PT we show via ferromagnetic resonance (FMR) that this type of linear ME allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The experiments unravel further an electric-field-induced negative magnetic permeability effect.

  1. Electric tuning of magnetization dynamics and electric field-induced negative magnetic permeability in nanoscale composite multiferroics.

    PubMed

    Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng

    2015-01-01

    Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with novel functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. A charge-mediated ME effect is believed to be generally weak and active in only a few angstroms. Here we present an experimental evidence uncovering a new magnon-driven, strong ME effect acting on the nanometer range. For Co92Zr8 (20 nm) film deposited on ferroelectric PMN-PT we show via ferromagnetic resonance (FMR) that this type of linear ME allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The experiments unravel further an electric-field-induced negative magnetic permeability effect. PMID:26058060

  2. Electric tuning of magnetization dynamics and electric field-induced negative magnetic permeability in nanoscale composite multiferroics

    PubMed Central

    Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng

    2015-01-01

    Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with novel functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. A charge-mediated ME effect is believed to be generally weak and active in only a few angstroms. Here we present an experimental evidence uncovering a new magnon-driven, strong ME effect acting on the nanometer range. For Co92Zr8 (20 nm) film deposited on ferroelectric PMN-PT we show via ferromagnetic resonance (FMR) that this type of linear ME allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The experiments unravel further an electric-field-induced negative magnetic permeability effect. PMID:26058060

  3. Time-resolved electric-field-induced second harmonic: simultaneous measurement of first and second molecular hyperpolarizabilities

    NASA Astrophysics Data System (ADS)

    Meshulam, G.; Kotler, Z.; Berkovic, G.

    2002-07-01

    The standard electric-field-induced second-harmonic (EFISH) technique for measurement of the first hyperpolarizability (bgr;) of nonlinear optical molecules is limited by the fact that the second hyperpolarizability (gamma) also contributes to the second-harmonic signal from which beta is deduced. We present a modified time-resolved EFISH in which the first and the second hyperpolarizabilities can be determined separately and accurately in the same experiment. We studied para-nitro aniline dissolved in a highly viscous solvent, glycerol, under conditions whereby the electric field was applied faster than the characteristic time for molecular rotation. This technique enabled the gamma contribution to the signal to be resolved separately from the beta contribution. The results confirm that for this molecule gamma contributes only approx10% of the total EFISH hyperpolarizability.

  4. Nuclear spin-lattice relaxation at field-induced level crossings in a Cr8F8 pivalate single crystal

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shoji

    2016-01-01

    We construct a microscopic theory for the proton spin-lattice relaxation-rate 1 / T1 measurements around field-induced level crossings in a single crystal of the trivalent chromium ion wheel complex [Cr8F8(OOCtBu)16] at sufficiently low temperatures [E. Micotti et al., Phys. Rev. B 72 (2005) 020405(R)]. Exactly diagonalizing a well-equipped spin Hamiltonian for the individual clusters and giving further consideration to their possible interactions, we reveal the mechanism of 1 / T1 being single-peaked normally at the first level crossing but double-peaked intriguingly around the second level crossing. We wipe out the doubt about poor crystallization and find out a solution-intramolecular alternating Dzyaloshinsky-Moriya interaction combined with intermolecular coupling of antiferromagnetic character, each of which is so weak as several tens of mK in magnitude.

  5. Electric-field-induced metal maintained by current of the Mott insulator Ca2RuO4

    PubMed Central

    Nakamura, Fumihiko; Sakaki, Mariko; Yamanaka, Yuya; Tamaru, Sho; Suzuki, Takashi; Maeno, Yoshiteru

    2013-01-01

    Recently, “application of electric field (E-field)” has received considerable attention as a new method to induce novel quantum phenomena since application of E-field can tune the electronic states directly with obvious scientific and industrial advantages over other turning methods. However, E-field-induced Mott transitions are rare and typically require high E-field and low temperature. Here we report that the multiband Mott insulator Ca2RuO4 shows unique insulator-metal switching induced by applying a dry-battery level voltage at room temperature. The threshold field Eth ~40 V/cm is much weaker than the Mott gap energy. Moreover, the switching is accompanied by a bulk structural transition. Perhaps the most peculiar of the present findings is that the induced metal can be maintained to low temperature by a weak current. PMID:23985626

  6. Levels of Mental Health Continuum and Personality Traits

    ERIC Educational Resources Information Center

    Joshanloo, Mohsen; Nosratabadi, Masoud

    2009-01-01

    Empirically, mental health and mental illness are not opposite ends of a single measurement continuum. In view of this fact, Keyes ("J Health Soc Behav," 43:207-202, 2002) operationalizes mental health as a syndrome of symptoms of both positive feelings (emotional well-being) and positive functioning (psychological and social well-being) in life.…

  7. Online Learning Interaction Continuum (OLIC): A Qualitative Case Study

    ERIC Educational Resources Information Center

    Hashim, Mohamad Hisyam Mohd.; Hashim, Yusup; Esa, Ahmad

    2011-01-01

    The purpose of this research project is to explore the use of Blackboard Learning System (BLS) in enhancing interaction in online teaching and learning enviornment. This paper discusses the conceptual framework of Online Learning Interaction Continuum (OLIC) which explains the five levels of interactions. The OLIC was conceptualized as a result of…

  8. Predicting Eating Disorder Continuum Groups: Hardiness and College Adjustment.

    ERIC Educational Resources Information Center

    Simon-Boyd, Gail D.; Bieschke, Kathleen J.

    This study examined relationships between hardiness, college adjustment (academic adjustment, social adjustment, personal-emotional adjustment, institutional attachment) and eating disorder (ED) continuum categories in 122 female and 20 male college students. Students who exhibited a higher level of personal-emotional adjustment (PEA) to college…

  9. Characterizing the radio continuum emission from intense starburst galaxies

    NASA Astrophysics Data System (ADS)

    Galvin, T. J.; Seymour, N.; Filipović, M. D.; Tothill, N. F. H.; Marvil, J.; Drouart, G.; Symeonidis, M.; Huynh, M. T.

    2016-09-01

    The intrinsic thermal (free-free) and non-thermal (synchrotron) emission components that comprise the radio continuum of galaxies represent unique, dust-free measures of star formation rates (SFR). Such high SFR galaxies will dominate the deepest current and future radio surveys. We disentangle the thermal and non-thermal emission components of the radio continuum of six ultraluminous infrared galaxies (LFIR > 1012.5 L⊙) at redshifts of 0.2 ≤ z ≤ 0.5 and 22 IR selected galaxies. Radio data over a wide frequency range (0.8 < ν < 10 GHz) are fitted with a star-forming galaxy model comprising of thermal and non-thermal components. The luminosities of both radio continuum components are strongly correlated to the 60 μm luminosity across many orders of magnitude (consistent with the far-IR to radio correlation). We demonstrate that the spectral index of the radio continuum spectral energy distribution is a useful proxy for the thermal fraction. We also find that there is an increase in mean and scatter of the thermal fraction with FIR to radio luminosity ratio which could be influenced by different time-scales of the thermal and non-thermal emission mechanisms.

  10. Searching for the Center on the Mathematics-Science Continuum.

    ERIC Educational Resources Information Center

    Roebuck, Kay I.; Warden, Melissa A.

    1998-01-01

    The history of mathematics and science integration in American schools is a continuum which runs from math for math's sake to science for science's sake. While examples of the integration of process skills are common, integration of content is not. Presents two lessons developed around radioactive decay and efficiency. Suggests that changes in…

  11. Assessing continuum postulates in simulations of granular flow

    SciTech Connect

    Rycroft, Chris; Kamrin, Ken; Bazant, Martin

    2008-08-26

    Continuum mechanics relies on the fundamental notion of a mesoscopic volume"element" in which properties averaged over discrete particles obey deterministic relationships. Recent work on granular materials suggests a continuum law may be inapplicable, revealing inhomogeneities at the particle level, such as force chains and slow cage breaking. Here, we analyze large-scale three-dimensional Discrete-Element Method (DEM) simulations of different granular flows and show that an approximate"granular element" defined at the scale of observed dynamical correlations (roughly three to five particle diameters) has a reasonable continuum interpretation. By viewing all the simulations as an ensemble of granular elements which deform and move with the flow, we can track material evolution at a local level. Our results confirm some of the hypotheses of classical plasticity theory while contradicting others and suggest a subtle physical picture of granular failure, combining liquid-like dependence on deformation rate and solid-like dependence on strain. Our computational methods and results can be used to guide the development of more realistic continuum models, based on observed local relationships betweenaverage variables.

  12. JCMT COADD: UKT14 continuum and photometry data reduction

    NASA Astrophysics Data System (ADS)

    Hughes, David; Oliveira, Firmin J.; Tilanus, Remo P. J.; Jenness, Tim

    2014-11-01

    COADD was used to reduce photometry and continuum data from the UKT14 instrument on the James Clerk Maxwell Telescope in the 1990s. The software can co-add multiple observations and perform sigma clipping and Kolmogorov-Smirnov statistical analysis. Additional information on the software is available in the JCMT Spring 1993 newsletter (large PDF).

  13. JCMTDR: Applications for reducing JCMT continuum data in GSD format

    NASA Astrophysics Data System (ADS)

    Lightfoot, John F.; Harrison, Paul A.; Meyerdierks, Horst; Jenness, Tim

    2014-06-01

    JCMTDR reduces continuum on-the-fly mapping data obtained with UKT14 or the heterodyne instruments using the IFD on the James Clerk Maxwell Telescope. This program reduces archive data and heterodyne beam maps and was distributed as part of the Starlink software collection (ascl:1110.012).

  14. Comment on the conductivity exponent in continuum percolation

    NASA Astrophysics Data System (ADS)

    Machta, J.

    1988-05-01

    The field theory introduced by Lubensky and Tremblay [Phys. Rev. B 34, 3408 (1986)] for continuum percolation is reanalyzed. Dynamical exponents are found which agree with those found by Straley [J. Phys. C 15, 2343 (1982)] and Machta et al. [Phys. Rev. B 33, 4818 (1986)] using a nodes-links-blobs approach.

  15. 48 CFR 215.101 - Best value continuum.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 3 2014-10-01 2014-10-01 false Best value continuum. 215.101 Section 215.101 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM, DEPARTMENT OF DEFENSE CONTRACTING METHODS AND CONTRACT TYPES CONTRACTING BY NEGOTIATION 215.101 Best...

  16. 48 CFR 215.101 - Best value continuum.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 3 2013-10-01 2013-10-01 false Best value continuum. 215.101 Section 215.101 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM, DEPARTMENT OF DEFENSE CONTRACTING METHODS AND CONTRACT TYPES CONTRACTING BY NEGOTIATION 215.101 Best...

  17. Continuum of Medical Education in Obstetrics and Gynecology.

    ERIC Educational Resources Information Center

    Dohner, Charles W.; Hunter, Charles A., Jr.

    1980-01-01

    Over the past eight years the obstetric and gynecology specialty has applied a system model of instructional planning to the continuum of medical education. The systems model of needs identification, preassessment, instructional objectives, instructional materials, learning experiences; and evaluation techniques directly related to objectives was…

  18. The Eating Disorders Continuum, Self-Esteem, and Perfectionism

    ERIC Educational Resources Information Center

    Peck, Lisa D.; Lightsey, Owen Richard

    2008-01-01

    Among 261 undergraduate women, increased severity of eating disorders along a continuum was associated with decreased self-esteem, increased perfectionism, and increased scores on 7 subscales of the Eating Disorders Inventory-2. Women with eating disorders differed from both symptomatic women and asymptomatic women on all variables, whereas…

  19. Written Language Developmental Continuum: Preschool-Second Grade.

    ERIC Educational Resources Information Center

    North Carolina State Dept. of Public Instruction, Raleigh.

    The purpose of this "Written Language Developmental Continuum" brochure for preschool-second grade is to provide helpful information for parents, teachers, and other adults as they work with young children to advance and refine written language (writing) competence. The brochure is intended to be a useful tool for assessing children's development…

  20. Continuum modeling of dense granular flow down heaps

    NASA Astrophysics Data System (ADS)

    Henann, David; Liu, Daren

    Dense, dry granular flows display many manifestations of grain-size dependence, or nonlocality, in which the finite-size of grains has an observable impact on flow phenomenology. Such behaviors make the formulation of an accurate continuum model for dense granular flow particularly difficult, since local continuum models are not equipped to describe size-effects. One example of grain-size dependence is seen when avalanches occur on a granular heap - a situation which is frequently encountered in industry, as in rotating drums, as well as in nature, such as in landslides. In this case, flow separates into a thin, quickly flowing surface layer and a slowly creeping bulk. While existing local granular flow models are capable of capturing aspects of the flowing surface layer, they fail to even predict the existence of creeping flow beneath, much less being able to quantitatively describe the flow fields. Recently, we have proposed a new, scale-dependent continuum model - the nonlocal granular fluidity (NGF) model - that successfully predicted steady, slow granular flow fields, including grain-size-dependent shear-band widths in a variety of flow configurations. In this talk, we extend our model to the rapid flow regime and show that the model is capable of quantitatively predicting all aspects of gravity-driven heap flow. In particular, the model predicts the coexistence of a rapidly flowing, rate-dependent top surface layer and a rate-independent, slowly creeping bulk - a feature which is beyond local continuum approaches.

  1. Space shuttle ram glow: Implication of NO2 recombination continuum

    NASA Technical Reports Server (NTRS)

    Swenson, G. R.; Mende, S. B.; Clifton, S.

    1985-01-01

    The ram glow data gathered to data from imaging experiments on space shuttle suggest the glow is a continuum (within 34 angstrom resolution); the continuum shape is such that the peak is near 7000 angstroms decreasing to the blue and red, and the average molecular travel leading to emission after leaving the surface is 20 cm (assuming isotropic scattering from the surface). Emission continuum is rare in molecular systems but the measured spectrum does resemble the laboratory spectrum of NO2 (B) recombination continuum. The thickness of the observed emission is consistent with the NO2 hypothesis given an exit velocity of approx. 2.5 km/sec (1.3 eV) which leaves approx. 3.7 eV of ramming OI energy available for unbonding the recombined NO2 from the surface. The NO2 is formed in a 3-body recombination of OI + NO + m = NO2 + m where OI originates from the atmosphere and NO is chemically formed on the surface from atmospheric NI and OI. The spacecraft surface then acts as the n for the reaction: Evidence exists from orbital mass spectrometer data that the NO and NO2 chemistry described in this process does occur on surfaces of spectrometer orifices in orbit. Surface temperature effects are likely a factor in the NO sticking efficiency and, therefore, glow intensities.

  2. Space shuttle Ram glow: Implication of NO2 recombination continuum

    NASA Astrophysics Data System (ADS)

    Swenson, G. R.; Mende, S. B.; Clifton, S.

    1985-09-01

    The ram glow data gathered to data from imaging experiments on space shuttle suggest the glow is a continuum (within 34 angstrom resolution); the continuum shape is such that the peak is near 7000 angstroms decreasing to the blue and red, and the average molecular travel leading to emission after leaving the surface is 20 cm (assuming isotropic scattering from the surface). Emission continuum is rare in molecular systems but the measured spectrum does resemble the laboratory spectrum of NO2 (B) recombination continuum. The thickness of the observed emission is consistent with the NO2 hypothesis given an exit velocity of approx. 2.5 km/sec (1.3 eV) which leaves approx. 3.7 eV of ramming OI energy available for unbonding the recombined NO2 from the surface. The NO2 is formed in a 3-body recombination of OI + NO + m = NO2 + m where OI originates from the atmosphere and NO is chemically formed on the surface from atmospheric NI and OI. The spacecraft surface then acts as the n for the reaction: Evidence exists from orbital mass spectrometer data that the NO and NO2 chemistry described in this process does occur on surfaces of spectrometer orifices in orbit. Surface temperature effects are likely a factor in the NO sticking efficiency and, therefore, glow intensities.

  3. Continuum estimates of rotational dielectric friction and polar solvation

    SciTech Connect

    Maroncelli, M.

    1997-01-01

    Dynamical solvation data recently obtained with the probe solute coumarin 153 are used to test the reliability of dielectric continuum models for estimating dielectric friction effects. In particular, the predictions of the Nee{endash}Zwanzig theory of rotational dielectric friction are examined in some detail. The analysis undertaken here uncovers an error made in virtually all previous applications of the Nee{endash}Zwanzig formalism. The error involves neglect of the solvent{close_quote}s electronic polarizability when calculating dielectric friction constants. In highly polar solvents the effect of this neglect is shown to be minor, so that the results of past studies should not be appreciably altered. However, in weakly polar and especially in nondipolar solvents, the proper inclusion of electronic polarizability terms is essential. The equivalence between the Nee{endash}Zwanzig theory of dielectric friction and more general continuum treatments of polar solvation dynamics is also demonstrated. This equivalence enables the use of solvation data to test the reliability of the Nee{endash}Zwanzig description of electrical interactions between a solute and solvent that form the core of this and related continuum theories of dielectric friction. Comparisons to experimental data show that, with the important exception of nondipolar solvents, such continuum treatments provide reasonably accurate ({plus_minus}40{percent}) predictors of time-dependent solvation and/or dielectric friction. {copyright} {ital 1997 American Institute of Physics.}

  4. RADMC: A 2-D Continuum Radiative Transfer Tool

    NASA Astrophysics Data System (ADS)

    Dullemond, C. P.

    2011-08-01

    RADMC is a 2-D Monte-Carlo code for dust continuum radiative transfer circumstellar disks and envelopes. It is based on the method of Bjorkman & Wood (ApJ 2001, 554, 615), but with several modifications to produce smoother results with fewer photon packages.

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

    NASA Astrophysics Data System (ADS)

    Berns, Christoph; Kondratiev, Yuri; Kutoviy, Oleksandr

    2013-06-01

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

  6. Continuum Response and Reaction in Neutron-Rich Be Nuclei

    SciTech Connect

    Nakatsukasa, Takashi; Ueda, Manabu; Yabana, Kazuhiro

    2004-02-27

    We study E1 resonances, breakup and fusion reactions for weakly bound Be nuclei. The absorbing-boundary condition (ABC) is used to describe both the outgoing and incoming boundary conditions. The neutron continuum plays important roles in response and reaction of neutron drip-line nuclei.

  7. Rape nitrogen nutrition diagnosis using continuum-removed hyperspectral reflectance

    NASA Astrophysics Data System (ADS)

    Zhang, Xuehong; Tian, Qingjiu

    2008-12-01

    The hyperspectral reflectance for rape fresh leaves and data of chlorophyll and total nitrogen content were acquired in primary growth stages under different nitrogen levels in order to monitor rape status and diagnose nitrogen using remote sensing method. A new method was developed for estimating the nitrogen nutrition of rape using continuum-removed method, which generally used in spectral analysis on rock and mineral. Based on the continuum-removed treatment and the correlation between absorption feature parameters and total nitrogen content of fresh leaves, results show that reflectance at the visible region decreased with increasing in the nitrogen fertilization, and continuum-removed operation can magnify the subtle difference in spectral absorption characteristics arose from the nitrogen stress on rape. During the seeding stage, bud-emerging stage and flowering stage of rape, total area of absorption peak, area left of the absorption peak and area right of the absorption peak in 550-750 nm region increased with increasing in the nitrogen fertilization, but it was opposite for the area-normalized maximal absorption depth. The correlation analysis indicated that it is at seeding stage that the relation between absorption characteristics parameters and leaf total nitrogen was best close. The research demonstrated that continuum-removed method is a feasible method for quantificational evaluation of rape nitrogen nutrition, and the seeding stage of rape is the best stage for assessment of rape nitrogen nutrition based on absorption characteristics of fresh leaves.

  8. Adaptive resolution refinement for high-fidelity continuum parameterizations

    SciTech Connect

    Anderson, J.W.; Khamayseh, A.; Jean, B.A.

    1996-10-01

    This paper describes an algorithm the adaptively samples a parametric continuum so that a fidelity metric is satisfied. Using the divide-and-conquer strategy of adaptive sampling eliminates the guesswork of traditional uniform parameterization techniques. The space and time complexity of parameterization are increased in a controllable manner so that a desired fidelity is obtained.

  9. Isospin Mixing and the Continuum Coupling in Weakly Bound Nuclei

    SciTech Connect

    Michel, N.; Nazarewicz, Witold; Ploszajczak, M.

    2010-01-01

    We investigate the near-threshold behavior of one-nucleon spectroscopic factors in mirror nuclei using the Gamow Shell Model, which simultaneously takes into account many-body correlations and continuum effects. We demonstrate that for weakly bound or unbound systems, the mirror symmetry-breaking effects are appreciable, and they manifest in large differences of spectroscopic factors in a mirror pair.

  10. 24 CFR 578.39 - Continuum of Care planning activities.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 24 Housing and Urban Development 3 2013-04-01 2013-04-01 false Continuum of Care planning activities. 578.39 Section 578.39 Housing and Urban Development Regulations Relating to Housing and Urban Development (Continued) OFFICE OF ASSISTANT SECRETARY FOR COMMUNITY PLANNING AND DEVELOPMENT, DEPARTMENT...

  11. 24 CFR 578.39 - Continuum of Care planning activities.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 24 Housing and Urban Development 3 2014-04-01 2013-04-01 true Continuum of Care planning activities. 578.39 Section 578.39 Housing and Urban Development Regulations Relating to Housing and Urban Development (Continued) OFFICE OF ASSISTANT SECRETARY FOR COMMUNITY PLANNING AND DEVELOPMENT, DEPARTMENT...

  12. Single attosecond pulse generation via continuum wave packet interference

    NASA Astrophysics Data System (ADS)

    Zhou, Shengpeng; Yang, Yujun; Ding, Dajun

    2016-07-01

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

  13. Scaffolding the Inquiry Continuum and the Constitution of Identity

    ERIC Educational Resources Information Center

    Melville, Wayne; Bartley, Anthony; Fazio, Xavier

    2013-01-01

    This article considers the impact of scaffolding on pre-service science teachers' constitution of identities as teachers of inquiry. This scaffolding has consisted of 2 major components, a unit on current electricity which encompasses the inquiry continuum and an open inquiry which is situated in context of classroom practice. Our analysis…

  14. Modes of interconnected lattice trusses using continuum models, part 1

    NASA Technical Reports Server (NTRS)

    Balakrishnan, A. V.

    1991-01-01

    This represents a continuing systematic attempt to explore the use of continuum models--in contrast to the Finite Element Models currently universally in use--to develop feedback control laws for stability enhancement of structures, particularly large structures, for deployment in space. We shall show that for the control objective, continuum models do offer unique advantages. It must be admitted of course that developing continuum models for arbitrary structures is no easy task. In this paper we take advantage of the special nature of current Large Space Structures--typified by the NASA-LaRC Evolutionary Model which will be our main concern--which consists of interconnected orthogonal lattice trusses each with identical bays. Using an equivalent one-dimensional Timoshenko beam model, we develop an almost complete continuum model for the evolutionary structure. We do this in stages, beginning only with the main bus as flexible and then going on to make all the appendages also flexible-except for the antenna structure. Based on these models we proceed to develop formulas for mode frequencies and shapes. These are shown to be the roots of the determinant of a matrix of small dimension compared with mode calculations using Finite Element Models, even though the matrix involves transcendental functions. The formulas allow us to study asymptotic properties of the modes and how they evolve as we increase the number of bodies which are treated as flexible. The asymptotics, in fact, become simpler.

  15. The Continuum and Current Controversies in the USA.

    ERIC Educational Resources Information Center

    Taylor, Steven J.

    2001-01-01

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

  16. Two Analyses of the ASL to English Continuum.

    ERIC Educational Resources Information Center

    Woodward, James; Allen, Thomas

    A study examined English grammatical characteristics used in the signing of teachers of hearing-impaired students, using a diglossic continuum between American Sign Language (ASL) and English. Scalogram analysis or implicational scaling, a traditional tool in variation theory useful for analyzing samples where there are a small number of tokens…

  17. Dynamics of glass-forming liquids. XIX. Rise and decay of field induced anisotropy in the non-linear regime.

    PubMed

    Young-Gonzales, Amanda R; Samanta, Subarna; Richert, Ranko

    2015-09-14

    For glycerol and three monohydroxy alcohols, we have measured the non-linear dielectric effects resulting from the application and removal of a high dc bias electric field. The field effects are detected by virtue of a small amplitude harmonic field, from which time resolved changes in the dielectric loss are derived. The changes in permittivity are dominated by modifications of the time constants (rather than amplitudes) which display two contributions: a heating-like decrease of relaxation times that originates from the time dependent field when the bias is switched on and off and a slowing down of the dynamics resulting from the field induced reduction of configurational entropy. As observed for the electro-optical Kerr effect, the rise of the entropy change is slower than its decay, a feature that we rationalize on the basis of the quadratic dependence of the entropy change on polarization. For glycerol, the observed steady state level of the field induced shift of the glass transition temperature (+84 mK) matches the expectation based on the entropy change and its impact on dynamics via the Adam-Gibbs relation (+88 mK). For the alcohols, these non-linear effects rise and decay on the time scales of the prominent dielectric Debye process, underscoring the relation of these features to polarization anisotropy, opposed to mechanical or enthalpy relaxation which are orders of magnitude faster in these systems. A model is discussed which captures the observed magnitudes as well as time dependences in a near quantitative fashion. It is demonstrated that the high bias field modifies the response of polarization to the ac field, including a temporary change in the low field susceptibility. PMID:26374047

  18. An electric field induced in the retina and brain at threshold magnetic flux density causing magnetophosphenes

    NASA Astrophysics Data System (ADS)

    Hirata, Akimasa; Takano, Yukinori; Fujiwara, Osamu; Dovan, Thanh; Kavet, Robert

    2011-07-01

    For magnetic field exposures at extremely low frequencies, the electrostimulatory response with the lowest threshold is the magnetophosphene, a response that corresponds to an adult exposed to a 20 Hz magnetic field of nominally 8.14 mT. In the IEEE standard C95.6 (2002), the corresponding in situ field in the retinal locus of an adult-sized ellipsoidal was calculated to be 53 mV m-1. However, the associated dose in the retina and brain at a high level of resolution in anatomically correct human models is incompletely characterized. Furthermore, the dose maxima in tissue computed with voxel human models are prone to staircasing errors, particularly for the low-frequency dosimetry. In the analyses presented in this paper, analytical and quasi-static finite-difference time-domain (FDTD) solutions were first compared for a three-layer sphere exposed to a uniform 50 Hz magnetic field. Staircasing errors in the FDTD results were observed at the tissue interface, and were greatest at the skin-air boundary. The 99th percentile value was within 3% of the analytic maximum, depending on model resolution, and thus may be considered a close approximation of the analytic maximum. For the adult anatomical model, TARO, exposed to a uniform magnetic field, the differences in the 99th percentile value of in situ electric fields for 2 mm and 1 mm voxel models were at most several per cent. For various human models exposed at the magnetophosphene threshold at three orthogonal field orientations, the in situ electric field in the brain was between 10% and 70% greater than the analytical IEEE threshold of 53 mV m-1, and in the retina was lower by roughly 50% for two horizontal orientations (anterior-posterior and lateral), and greater by about 15% for a vertically oriented field. Considering a reduction factor or safety factors of several folds applied to electrostimulatory thresholds, the 99th percentile dose to a tissue calculated with voxel human models may be used as an estimate of

  19. Mechanics of low-dimensional carbon nanostructures: Atomistic, continuum, and multi-scale approaches

    NASA Astrophysics Data System (ADS)

    Mahdavi, Arash

    nanotubes and carbon nanocones subject to different loadings and boundary conditions. This finite element technique is also used to study the natural frequencies of low-dimensional carbon nanostructures and comparing the results with those of a homogenized isotropic continuum shell. Conclusion is that, replacing the atomic lattice with an isotropic continuum shell for a graphene sheet does not significantly affect the vibration frequencies while in the case of carbon nanotubes and carbon nanocones there is a significant difference between the natural frequencies of the atomistic model and its continuum counterpart. In the case of the carbon nanotube, continuum model successfully captures the beam bending vibration modes while overestimating frequencies of the modes in which the cross-section undergoes significant deformation. Furthermore, in the case of carbon nanotubes, the continuum shell exhibits a torsional mode which appears to be an artifact resulting from the small nominal thickness typically used in the continuum shell approximation of these nanostructures. Results of this study indicate that isotropic continuum shell models, while simple and useful in static analysis, cannot accurately predict the vibration frequencies of these nanostructures. We have studied the bistable nature of single-walled carbon nanotubes by investigating the change in the tube's energy as it is compressed between flat rigid indenters of various widths. Assuming the nanotube deformed uniformly along its length and modeling the cross-section as an inextensible, non-linear beam we found that tubes with a radius greater than 12 A are bistable and that tubes with a radius greater than 25 A have a lower energy in the collapsed state than in the inflated state. The difference in energy between the collapsed and inflated states decreases nearly linearly with increasing tube radius. While the inflated state remains stable for tubes of all diameters, the energy barrier keeping the tube from

  20. The High-energy Continuum Emission of the Gamma-Ray Blazar PKS 0528+134

    NASA Technical Reports Server (NTRS)

    Sambruna, Rita M.; Urry, C. Megan; Maraschi, L.; Ghisellini, G.; Mukherjee, R.; Pesce, Joseph E.; Wagner, S. J.; Wehrle, A. E.; Hartman, R. C.; Lin, Y. C.; VonMintigny, C.

    1997-01-01

    We present Advanced Satellite for Cosmology and Astrophysics (ASCA) observations of the gamma-ray blazar PKS 0528 + 134, obtained at two separate epochs in 1994 August and 1995 March. These data represent the first measurement of the X-ray continuum emission of this source in the medium-hard X-ray band. Both ASCA spectra are consistent with a single power law with photon index GAMMA approx. = 1.7-1.8 and column density N(sub H) approx. = 5 x 10(exp 21)/ sq cm, higher than Galactic. The X-ray flux increased by a factor of 4 in approx. 7 months without appreciable change of the spectral shape. During the lower state of 1994 August, PKS 0528 + 134 was observed simultaneously in the optical, X-rays, and at gamma-ray energies with Energetic Gamma Ray Experiment Telescope (EGRET). The gamma-ray intensity is the faintest detected thus far in the source, with a steep spectrum (GAMMA approx. = 2.7). The extrapolation of the X-ray continuum to the gamma-ray range requires a sharp spectral break at approx. 10(exp 22) Hz. We discuss the radio through gamma-ray spectral energy distribution of PKS 0528 + 134, comparing the low state of 1994 August with the flare state of 1993 March. We show that in PKS 0528 + 134, a non-negligible contribution from the external radiation field is present and that, although synchrotron self-Compton scenarios cannot be ruled out, inverse Compton upscattering of thermal seed photons may be the dominant cooling process for the production of the high-energy continuum in this blazar.

  1. The High-Energy Continuum Emission of the Gamma-Ray Blazar PKS 0528+134

    NASA Technical Reports Server (NTRS)

    Sambruna, Rita M.; Urry, C. Megan; Maraschi, L.; Ghisellini, G.; Mukherjee, R.; Pesce, Joseph E.; Wagner, S. J.; Wehrle, A. E.; Hartman, R. C.; Lin, Y. C.

    1997-01-01

    We present Advanced Satellite for Cosmology and Astrophysics (ASCA) observations of the gamma-ray blazar PKS 0528 + 134, obtained at two separate epochs in 1994 August and 1995 March. These data represent the first measurement of the X-ray continuum emission of this source in the medium-hard X-ray band. Both ASCA spectra are consistent with a single power law with photon index GAMMA approximate 1.7-1.8 and column density N(sub H) approximately 5 x 10(exp 21) /sq cm, higher than Galactic. The X-ray flux increased by a factor of 4 in approximately 7 months without appreciable change of the spectral shape. During the lower state of 1994 August, PKS 0528 + 134 was observed simultaneously in the optical, X-rays, and at gamma-ray energies with EGRET. The gamma-ray intensity is the faintest detected thus far in the source, with a steep spectrum (GAMMA approximately 2.7). The extrapolation of the X-ray continuum to the gamma-ray range requires a sharp spectral break at approximately 10(exp 22) Hz. We discuss the radio through gamma-ray spectral energy distribution of PKS 0528 + 134, comparing the low state of 1994 August with the flare state of 1993 March. We show that in PKS 0528 + 134, a non-negligible contribution from the external radiation field is present and that, although synchrotron self-Compton scenarios cannot be ruled out, inverse Compton upscattering of thermal seed photons may be the dominant cooling process for the production of the high-energy continuum in this blazar.

  2. Lower Eyelid Blepharoplasty.

    PubMed

    Branham, Gregory H

    2016-05-01

    The goal of lower eyelid blepharoplasty is to rejuvenate the lower lid while maintaining a natural, unoperated appearance. Successful lower eyelid blepharoplasty depends on knowledge of the anatomy and surgical techniques, accurate preoperative analysis, and attention to detail. Common issues of the lower eyelid such as malar descent, tear trough deformity, pseudoherniated fat, lid laxity, and skin texture changes as well as dermatochalasis and festoons must be recognized. Specific techniques to address these include transcutaneous and transconjunctival approaches, fat excision, fat transposition, orbicularis suspension, lateral canthal tightening, malar suspension, and skin excision/resurfacing. PMID:27105798

  3. Aliovalent cation ordering, coexisting ferroelectric structures, and electric field induced phase transformation in lead-free ferroelectric Na0.5Bi0.5TiO3

    NASA Astrophysics Data System (ADS)

    Pan, Jaysree; Niranjan, Manish K.; Waghmare, Umesh V.

    2016-03-01

    Using first-principles calculations, we show that a specific chemical ordering of Na and Bi in Na0.5Bi0.5TiO3 is responsible for the co-existence of its ferroelectric phases with rhombohedral R3c and monoclinic Cc structures, which are relevant to its morphotropic phase boundary and large piezoelectric response. We identify the signatures of chemical ordering in the calculated phonon spectra and establish the prevalence of A-type ordering through comparison with experiment. We uncover a mechanism of the observed electric field induced Cc to lower energy R3c structural transformation promoted by a hybrid soft mode involving a combination of TiO6 rotations and a polar component.

  4. Field induced phase transition in Sm{sub 0.5}(Ca{sub 1−x}Sr{sub x}){sub 0.5}MnO{sub 3}

    SciTech Connect

    Sabyasachi, Sk. Majumdar, S. Giri, S.

    2014-04-24

    We demonstrate a fascinating consequence of A-site disorder at x = 0.5 in a new series Sm{sub 0.5}(Ca{sub 1−x}Sr{sub x}){sub 0.5}MnO{sub 3}. An unusual magnetic field-induced ultra-sharp transition to ferromagnetic metallic (FMM) state and collapse of charge ordering are observed both in magnetization and magnetoresistance curves at much lower field compared to end compounds. When magnetic field is applied above a critical field, FMM state appears and it retains the high-field state, although magnetic field decreases to zero. With decreasing field sweep rate the transition shifts to higher field indicating a meta-magnetic transition. The atomic-scale local inhomogeneity/distortion arising from the difference in ionic radii and/or the random Coulomb potential from ion mixture is supposed to be critical behind such striking phenomena.

  5. On the continuum intensity distribution of the solar photosphere

    NASA Astrophysics Data System (ADS)

    Wedemeyer-Böhm, S.; Rouppe van der Voort, L.

    2009-08-01

    Context: For many years, there seemed to be significant differences between the continuum intensity distributions derived from observations and simulations of the solar photosphere. Aims: In order to settle the discussion on these apparent discrepancies, we present a detailed comparison between simulations and seeing-free observations that takes into account the crucial influence of instrumental image degradation. Methods: We use a set of images of quiet Sun granulation taken in the blue, green and red continuum bands of the Broadband Filter Imager of the Solar Optical Telescope (SOT) onboard Hinode. The images are deconvolved with point spread functions (PSF) that account for non-ideal contributions due to instrumental stray-light and imperfections. In addition, synthetic intensity images are degraded with the corresponding PSFs. The results are compared with respect to spatial power spectra, intensity histograms, and the centre-to-limb variation of the intensity contrast. Results: The intensity distribution of SOT granulation images is broadest for the blue continuum at disc-centre and narrows towards the limb and for longer wavelengths. The distributions are relatively symmetric close to the limb but exhibit a growing asymmetry towards disc-centre. The intensity contrast, which is connected to the width of the distribution, is found to be (12.8 ± 0.5)%, (8.3 ± 0.4)%, and (6.2 ± 0.2)% at disc-centre for blue, green, and red continuum, respectively. Removing the influence of the PSF unveils much broader intensity distributions with a secondary component that is otherwise only visible as an asymmetry between the darker and brighter than average part of the distribution. The contrast values increase to (26.7 ± 1.3)%, (19.4 ± 1.4)%, and (16.6 ± 0.7)% for blue, green, and red continuum, respectively. The power spectral density of the images exhibits a pronounced peak at spatial scales characteristic for the granulation pattern and a steep decrease towards

  6. RHESSI LINE AND CONTINUUM OBSERVATIONS OF SUPER-HOT FLARE PLASMA

    SciTech Connect

    Caspi, A.; Lin, R. P.

    2010-12-20

    We use RHESSI high-resolution imaging and spectroscopy observations from {approx}5 to 100 keV to characterize the hot thermal plasma during the 2002 July 23 X4.8 flare. These measurements of the steeply falling thermal X-ray continuum are well fit throughout the flare by two distinct isothermal components: a super-hot (T{sub e} > 30 MK) component that peaks at {approx}44 MK and a lower-altitude hot (T{sub e} {approx}< 25 MK) component whose temperature and emission measure closely track those derived from GOES measurements. The two components appear to be spatially distinct, and their evolution suggests that the super-hot plasma originates in the corona, while the GOES plasma results from chromospheric evaporation. Throughout the flare, the measured fluxes and ratio of the Fe and Fe-Ni excitation line complexes at {approx}6.7 and {approx}8 keV show a close dependence on the super-hot continuum temperature. During the pre-impulsive phase, when the coronal thermal and non-thermal continua overlap both spectrally and spatially, we use this relationship to obtain limits on the thermal and non-thermal emission.

  7. Wide-Area Mapping of 155 Micron Continuum Emission from the Orion Molecular Cloud Complex

    NASA Astrophysics Data System (ADS)

    Arimura, Seikoh; Shibai, Hiroshi; Teshima, Takafumi; Nakagawa, Takao; Narita, Masanao; Makiuti, Shin'itirou; Doi, Yasuo; Verma, Ram Prakash; Ghosh, Swarna Kanti; Rengarajan, Thinnian Naganathan; Tanaka, Makoto; Okuda, Haruyuki

    2004-02-01

    We present the results of a wide-area mapping of the far-infrared continuum emission toward the Orion complex by using a Japanese balloon-borne telescope. The 155-μm continuum emission was detected over a region of 1.5 deg2 around the KL nebula with 3‧ resolution similar to that of the IRAS 100-μm map. Assuming a single-temperature model of the thermal equilibrium dust, maps of the temperature and the optical thickness were derived from the 155-μm intensity and the IRAS 100-μm intensity. The derived dust temperature is 5-15K lower and the derived dust optical depth is 5-300 times larger than those derived from the IRAS 60 and 100-μm intensities due to the significant contribution of the statistically heated very small grains to the IRAS 60-μm intensity. The optical-thickness distribution shows a filamentary dust ridge that has a 1°.5 extent in the north-south direction and well resembles the Integral-Shaped Filament (ISF) molecular gas distribution. The gas-to-dust ratio derived from the CO molecular gas distribution along the ISF is in the range 30-200, which may be interpreted as being an effect of CO depletion due to the photodissociation and/or the freezing on dust grains.

  8. The likelihood ratio as a tool for radio continuum surveys with Square Kilometre Array precursor telescopes

    NASA Astrophysics Data System (ADS)

    McAlpine, K.; Smith, D. J. B.; Jarvis, M. J.; Bonfield, D. G.; Fleuren, S.

    2012-06-01

    In this paper we investigate the performance of the likelihood ratio method as a tool for identifying optical and infrared counterparts to proposed radio continuum surveys with Square Kilometre Array (SKA) precursor and pathfinder telescopes. We present a comparison of the infrared counterparts identified by the likelihood ratio in the VISTA Deep Extragalactic Observations (VIDEO) survey to radio observations with 6, 10 and 15 arcsec resolution. We cross-match a deep radio catalogue consisting of radio sources with peak flux density >60 ?Jy with deep near-infrared data limited to Ks≲ 22.6. Comparing the infrared counterparts from this procedure to those obtained when cross-matching a set of simulated lower resolution radio catalogues indicates that degrading the resolution from 6 arcsec to 10 and 15 arcsec decreases the completeness of the cross-matched catalogue by approximately 3 and 7 per cent respectively. When matching against shallower infrared data, comparable to that achieved by the VISTA Hemisphere Survey, the fraction of radio sources with reliably identified counterparts drops from ˜89 per cent, at Ks≲ 22.6, to 47 per cent with Ks≲ 20.0. Decreasing the resolution at this shallower infrared limit does not result in any further decrease in the completeness produced by the likelihood ratio matching procedure. However, we note that radio continuum surveys with the MeerKAT and eventually the SKA, will require long baselines in order to ensure that the resulting maps are not limited by instrumental confusion noise.

  9. Elucidating a Goal-Setting Continuum in Brain Injury Rehabilitation.

    PubMed

    Hunt, Anne W; Le Dorze, Guylaine; Trentham, Barry; Polatajko, Helene J; Dawson, Deirdre R

    2015-08-01

    For individuals with brain injury, active participation in goal setting is associated with better rehabilitation outcomes. However, clinicians report difficulty engaging these clients in goal setting due to perceived or real deficits (e.g., lack of awareness). We conducted a study using grounded theory methods to understand how clinicians from occupational therapy facilitate client engagement and manage challenges inherent in goal setting with this population. Through constant comparative analysis, a goal-setting continuum emerged. At one end of the continuum, therapists embrace client-determined goals and enable clients to decide their own goals. At the other, therapists accept preset organization-determined goals (e.g., "the goal is discharge") and pay little attention to client input. Although all participants aspired to embrace client-determined goal setting, most felt powerless to do so within perceived organizational constraints. Views of advocacy and empowerment help to explain our findings and inform more inclusive practice. PMID:26187534

  10. Theoretical quasar emission-line ratios. V - Balmer continuum emission

    NASA Technical Reports Server (NTRS)

    Puetter, R. C.; Levan, P. D.

    1982-01-01

    Isothermal, isobaric models of quasar emission line regions are presented which include an improved treatment of radiative transfer in the bound-free continua, based on a generalization of frequency-integrated line transfer techniques and on the use of a probabilistic radiative transfer equation which explicitly distinguishes between the flux divergence coefficient and the photon escape probability. It is found that Balmer continuum emission can be obtained without compromising observed line ratios. It is also established that optically thin or thick Balmer continuum emission models with blended Fe II line are consistent with 4000-2000 A 'blue bump' observations, and that the improved radiative transfer treatment makes order-of-magnitude corrections to level populations and local cooling rates calculated with past techniques.

  11. A nonlinear generalized continuum approach for electro-mechanical coupling

    NASA Astrophysics Data System (ADS)

    Skatulla, S.; Arockiarajan, A.; Sansour, C.

    2008-07-01

    Electro-active polymers (EAP) are "smart materials" whose mechanical properties may be changed significantly by the application of electric field. Hence, these materials can serve as actuators in electro-mechanical systems, artificial muscles, etc. In this paper, we provide a generalized continuum framework basis for the characterization of the nonlinear electroelastic properties of these materials. This approach introduces new strain and stress measures which lead to the formulation of a corresponding generalized variational principle. The theory is then completed by Dirichlet boundary conditions for the displacement field and the electric potential and then derivatives normal to the boundary. The basic idea behind this generalized continuum framework is the consideration of a micro- and a macro-space which together span the generalized space. All quantities including the constitutive law for the electro-mechanically coupled nonlinear hyperelasticity are defined in the generalized space. Numerical examples are presented to demonstrate the numerical accuracy of the implemented formulation using the mesh free method.

  12. Capillarity-driven flows at the continuum limit.

    PubMed

    Vincent, Olivier; Szenicer, Alexandre; Stroock, Abraham D

    2016-08-21

    We experimentally investigate the dynamics of capillary-driven flows at the nanoscale, using an original platform that combines nanoscale pores (⋍3 nm in diameter) and microfluidic features. In particular, we show that drying involves a fine coupling between thermodynamics and fluid mechanics that can be used to generate precisely controlled nanoflows driven by extreme stresses - up to 100 MPa of tension. We exploit these tunable flows to provide quantitative tests of continuum theories (e.g. Kelvin-Laplace equation and Poiseuille flow) across an unprecedented range and we isolate the breakdown of continuum as a negative slip length of molecular dimension. Our results show a coherent picture across multiple experiments including drying-induced permeation flows, imbibition and poroelastic transients. PMID:27444407

  13. Hybrid discrete/continuum algorithms for stochastic reaction networks

    SciTech Connect

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

    2015-01-15

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

  14. Continuum mechanical and computational aspects of material behavior

    SciTech Connect

    Fried, Eliot; Gurtin, Morton E.

    2000-02-10

    The focus of the work is the application of continuum mechanics to materials science, specifically to the macroscopic characterization of material behavior at small length scales. The long-term goals are a continuum-mechanical framework for the study of materials that provides a basis for general theories and leads to boundary-value problems of physical relevance, and computational methods appropriate to these problems supplemented by physically meaningful regularizations to aid in their solution. Specific studies include the following: the development of a theory of polycrystalline plasticity that incorporates free energy associated with lattice mismatch between grains; the development of a theory of geometrically necessary dislocations within the context of finite-strain plasticity; the development of a gradient theory for single-crystal plasticity with geometrically necessary dislocations; simulations of dynamical fracture using a theory that allows for the kinking and branching of cracks; computation of segregation and compaction in flowing granular materials.

  15. Non compact continuum limit of two coupled Potts models

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  16. Continuum models of focused electron beam induced processing

    PubMed Central

    Lobo, Charlene; Friedli, Vinzenz; Szkudlarek, Aleksandra; Utke, Ivo

    2015-01-01

    Summary Focused electron beam induced processing (FEBIP) is a suite of direct-write, high resolution techniques that enable fabrication and editing of nanostructured materials inside scanning electron microscopes and other focused electron beam (FEB) systems. Here we detail continuum techniques that are used to model FEBIP, and release software that can be used to simulate a wide range of processes reported in the FEBIP literature. These include: (i) etching and deposition performed using precursors that interact with a surface through physisorption and activated chemisorption, (ii) gas mixtures used to perform simultaneous focused electron beam induced etching and deposition (FEBIE and FEBID), and (iii) etch processes that proceed through multiple reaction pathways and generate a number of reaction products at the substrate surface. We also review and release software for Monte Carlo modeling of the precursor gas flux which is needed as an input parameter for continuum FEBIP models. PMID:26425405

  17. Wave propagation in equivalent continuums representing truss lattice materials

    SciTech Connect

    Messner, Mark C.; Barham, Matthew I.; Kumar, Mukul; Barton, Nathan R.

    2015-07-29

    Stiffness scales linearly with density in stretch-dominated lattice meta-materials offering the possibility of very light yet very stiff structures. Current additive manufacturing techniques can assemble structures consisting of these lattice materials, but the design of such structures will require accurate, efficient simulation techniques. Equivalent continuum models have several advantages over discrete truss models of stretch dominated lattices, including computational efficiency and ease of model construction. However, the development an equivalent model suitable for representing the dynamic response of a periodic truss is complicated by microinertial effects. This paper derives a dynamic equivalent continuum model for periodic truss structures and verifies it against detailed finite element simulations. The model must incorporate microinertial effects to accurately reproduce long-wavelength characteristics of the response such as anisotropic elastic soundspeeds. The formulation presented here also improves upon previous work by preserving equilibrium at truss joints for affine lattice deformation and by improving numerical stability by eliminating vertices in the effective yield surface.

  18. 1.4 GHz continuum sources in the Cancer cluster

    NASA Technical Reports Server (NTRS)

    Salpeter, E. E.; Dickey, J. M.

    1987-01-01

    Results of 1.4-GHz continuum observations are presented for 11 VLA fields, using the D-configuration, which contain the A group of the Cnc cluster (CC). Sixteen Zwicky spiral galaxies in the CC were detected, but no ellipticals, confirming the finding that spiral galaxies with close companions tend to have enhanced radio emission. Over 200 continuum sources beyond the CC are tabulated. The spectral index (relative to 610 MHz) is given for many of the sources, including some of the Zwicky galaxies. There is a suggestion for a nonuniform number surface-density distribution of the sources, not correlated with the CC. Possible predictions of such nonuniformities, from assumptions on 'super-superclusters', are discussed.

  19. The virial theorem for the polarizable continuum model

    SciTech Connect

    Cammi, R.

    2014-02-28

    The electronic virial theorem is extended to molecular systems within the framework of the Polarizable Continuum Model (PCM) to describe solvation effects. The theorem is given in the form of a relation involving the components of the energy (kinetic and potential) of a molecular solute and its electrostatic properties (potential and field) at the boundary of the cavity in the continuum medium. The virial theorem is also derived in the presence of the Pauli repulsion component of the solute-solvent interaction. Furthermore, it is shown that these forms of the PCM virial theorem may be related to the virial theorem of more simple systems as a molecule in the presence of fixed point charges, and as an atom in a spherical box with confining potential.

  20. Bound States in the Continuum in double layer structures

    PubMed Central

    Li, LiangSheng; Yin, Hongcheng

    2016-01-01

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