Topological states in partially-PT-symmetric azimuthal potentials
Kartashov, Yaroslav V; Torner, Lluis
2015-01-01
We introduce partially-parity-time-symmetric (pPT-symmetric) azimuthal potentials composed from individual PT-symmetric cells located on a ring, where two azimuthal directions are nonequivalent in a sense that in such potentials excitations carrying topological dislo-cations exhibit different dynamics for different directions of energy circulation in the initial field distribution. Such non-conservative ratchet-like structures support rich families of stable vortex solitons in cubic nonlinear media, whose properties depend on the sign of the topological charge due to the nonequivalence of azimuthal directions. In contrast, oppositely charged vortex solitons remain equivalent in similar fully PT-symmetric potentials. The vortex solitons in the pPT- and PT-symmetric potentials are shown to feature qualitatively different internal current distributions, which are described by different discrete rotation symmetries of the intensity profiles.
Scattering off PT-symmetric upside-down potentials
Bender, Carl M
2016-01-01
The upside-down $-x^4$, $-x^6$, and $-x^8$ potentials with appropriate PT-symmetric boundary conditions have real, positive, and discrete quantum-mechanical spectra. This paper proposes a straightforward macroscopic quantum-mechanical scattering experiment in which one can observe and measure these bound-state energies directly.
Controlling electric, magnetic, and chiral dipolar emission with PT-symmetric potentials
Energy Technology Data Exchange (ETDEWEB)
Alaeian, Hadiseh; Dionne, Jennifer A.
2015-06-01
We investigate the effect of parity-time (PT) symmetric optical potentials on the radiation of achiral and chiral dipole sources. Two properties unique to PT-symmetric potentials are observed. First, the dipole can be tuned to behave as a strong optical emitter or absorber based on the non-Hermiticity parameter and the dipole location. Second, exceptional points give rise to new system resonances that lead to orders-of-magnitude enhancements in the dipolar emitted or absorbed power. Utilizing these properties, we show that enantiomers of chiral molecules near PT-symmetric metamaterials exhibit a 4.5-fold difference in their emitted power and decay rate. The results of this work could enable new atom-cavity interactions for quantum optics, as well as all-optical enantioselective separation.
Spectral Singularity in confined PT symmetric optical potential
Sinha, Anjana
2013-01-01
We present an analytical study for the scattering amplitudes (Reflection |R| and Transmission |T|), of the periodic PT symmetric optical potential V(x) = W_0 cos^2 x + i W_0 V_0 sin 2x confined within the region 0 0.5) scattering is found to be anomalous (|T|^2, |R|^2 not necessarily \\leq 1). Additionally, in this parameter regime of V_0, one observes infinite number of spectral singularities E_{SS} at different values of V_0. Furthermore, for L = 2n \\pi, the transition point V_0 = 0.5 shows unidirectional invisibility with zero reflection when the beam is incident from the absorptive side (Im[V(x)] 0), transmission being identically unity in both cases.
Scarcity of real discrete eigenvalues in non-analytic complex $\\mathcal{PT}$-symmetric potentials
Indian Academy of Sciences (India)
Zafar Ahmed
2009-08-01
We find that a non-differentiability occurring whether in real or imaginary part of a complex $\\mathcal{PT}$-symmetric potential causes a scarcity of the real discrete eigenvalues despite the real part alone possessing an infinite spectrum. We demonstrate this by perturbing the real potentials 2 and || by imaginary $\\mathcal{PT}$ -symmetric potentials || and , respectively.
Green's Function of a General PT-Symmetric Non-Hermitian Non-central Potential
Mourya, Brijesh Kumar
2016-01-01
We study the path integral solution of a system of particle moving in certain class of PT symmetric non-Hermitian and non-central potential. The Hamil- tonian of the system is converted to a separable Hamiltonian of Liouville type in parabolic coordinates and is further mapped into a Hamiltonian corresponding to two 2-dimensional simple harmonic oscillators (SHOs). Thus the explicit Green's functions for a general non-central PT symmetric non hermitian potential are cal- culated in terms of that of 2d SHOs. The entire spectrum for this three dimensional system is shown to be always real leading to the fact that the system remains in unbroken PT phase all the time.
Spectral singularity in confined PT symmetric optical potential
Energy Technology Data Exchange (ETDEWEB)
Sinha, Anjana [Department of Instrumentation Science, Jadavpur University, Kolkata - 700 032 (India); Roychoudhury, R. [Department of Mathematics, Bethune College, Kolkata - 700 006, India and Advanced Centre for Nonlinear and Complex Phenomena, 1175 Survey Park, Kolkata - 700075 (India)
2013-11-15
We present an analytical study for the scattering amplitudes (Reflection ‖R‖ and Transmission ‖T‖), of the periodic PT symmetric optical potential V(x)=W{sub 0}cos{sup 2}x+iV{sub 0}sin2x confined within the region 0 ⩽x⩽L, embedded in a homogeneous medium having uniform potential W{sub 0}. The confining length L is considered to be some integral multiple of the period π. We give some new and interesting results. Scattering is observed to be normal (‖T‖{sup 2}⩽ 1, ‖R‖{sup 2}⩽ 1) for V{sub 0}⩽ 0.5, when the above potential can be mapped to a Hermitian potential by a similarity transformation. Beyond this point (V{sub 0} > 0.5) scattering is found to be anomalous (‖T‖{sup 2}, ‖R‖{sup 2} not necessarily ⩽1). Additionally, in this parameter regime of V{sub 0}, one observes infinite number of spectral singularities E{sub SS} at different values of V{sub 0}. Furthermore, for L= 2nπ, the transition point V{sub 0}= 0.5 shows unidirectional invisibility with zero reflection when the beam is incident from the absorptive side (Im[V(x)] < 0) but with finite reflection when the beam is incident from the emissive side (Im[V(x)] > 0), transmission being identically unity in both cases. Finally, the scattering coefficients ‖R‖{sup 2} and ‖T‖{sup 2} always obey the generalized unitarity relation : ‖T|{sup 2}−1|=√(|R{sub R}|{sup 2}|R{sub L}|{sup 2}), where subscripts R and L stand for right and left incidence, respectively.
Controlling electric, magnetic, and chiral dipolar emission with PT-symmetric potentials
Alaeian, Hadiseh
2014-01-01
We investigate the effect of parity-time (PT)-symmetric optical potentials on the radiation of achiral and chiral emitters. Mode coalescence and the appearance of exceptional points lead to orders-of-magnitude enhancements in the emitted dipole power. Further, the emitter can be tuned to behave as a strong optical source or absorber based on the non-Hermiticity parameter. Chiral enantiomers radiating near PT metamaterials exhibit a 4.5-fold difference in their decay rate. The results of this work could enable new atom-cavity interactions for quantum optics, as well as all- optical enantio-specific separation.
On PT-Symmetric Periodic Potential, Quark Confinement, and Other Impossible Pursuits
Directory of Open Access Journals (Sweden)
Christianto V.
2009-01-01
Full Text Available As we know, it has been quite common nowadays for particle physicists to think of six impossible things before breakfast, just like what their cosmology fellows used to do. In the present paper, we discuss a number of those impossible things, including PT-symmetric periodic potential, its link with condensed matter nuclear science, and possible neat link with Quark confinement theory. In recent years, the PT-symmetry and its related periodic potential have gained considerable interests among physicists. We begin with a review of some results from a preceding paper discussing derivation of PT-symmetric periodic potential from biquaternion Klein-Gordon equation and proceed further with the remaining issues. Further observation is of course recommended in order to refute or verify this proposition.
Eigenvalue spectra of a $\\mathcal{PT}$ -symmetric coupled quartic potential in two dimensions
Indian Academy of Sciences (India)
Fakir Chand; Savita; S C Mishra
2010-10-01
The Schrödinger equation was solved for a generalized $\\mathcal{PT}$-symmetric quartic potential in two dimensions. It was found that, under a suitable ansatz for the wave function, the system possessed real and discrete energy eigenvalues. Analytic expressions for the energy eigenvalues and the eigenfunctions for the first four states were obtained. Some constraining relations among the wave function parameters rendered the problem quasi-solvable.
Classical irregular blocks, Hill's equation and PT-symmetric periodic complex potentials
Piatek, Marcin; Pietrykowski, Artur R.
2016-07-01
The Schrödinger eigenvalue problems for the Whittaker-Hill potential {Q}_2(x) = 1/2{h}^2 cos 4x + 4hμ cos 2x and the periodic complex potential {Q}_1(x)=1/4{h}^2{e}^{-} 4ix} + 2{h}^2 cos 2x are studied using their realizations in two-dimensional conformal field theory (2dCFT). It is shown that for the weak coupling (small) h ∈ ℝ and non-integer Floquet parameter ν ∉ ℤ spectra of hamiltonians ℋi = - d2/d x 2 + Q i( x), i = 1, 2 and corresponding two linearly independent eigenfunctions are given by the classical limit of the "single flavor" and "two flavors" ( N f = 1 , 2) irregular conformal blocks. It is known that complex nonhermitian hamiltonians which are PT-symmetric (= invariant under simultaneous parity P and time reversal T transformations) can have real eigenvalues. The hamiltonian ℋ1 is PT-symmetric for h, x ∈ ℝ. It is found that ℋ1 has a real spectrum in the weak coupling region for ν ∈ ℝ ℤ. This fact in an elementary way follows from a definition of the N f = 1 classical irregular block. Thus, ℋ1 can serve as yet another new model for testing postulates of PT-symmetric quantum mechanics.
Various scattering properties of a new PT-symmetric non-Hermitian potential
Energy Technology Data Exchange (ETDEWEB)
Ghatak, Ananya, E-mail: gananya04@gmail.com [Department of Physics, Banaras Hindu University, Varanasi-221005 (India); Mandal, Raka Dona Ray, E-mail: rakad.ray@gmail.com [Department of Physics, Rajghat Besant School, Varanasi-221001 (India); Mandal, Bhabani Prasad, E-mail: bhabani.mandal@gmail.com [Department of Physics, Banaras Hindu University, Varanasi-221005 (India)
2013-09-15
We complexify a 1-d potential V(x)=V{sub 0}cosh{sup 2}μ(tanh[(x−μd)/d]+tanh(μ)){sup 2} which exhibits bound, reflecting and free states to study various properties of a non-Hermitian system. This potential turns out a PT-symmetric non-Hermitian potential when one of the parameters (μ,d) becomes imaginary. For the case of μ→iμ, we have an entire real bound state spectrum. Explicit scattering states are constructed to show reciprocity at certain discrete values of energy even though the potential is not parity symmetric. Coexistence of deep energy minima of transmissivity with the multiple spectral singularities (MSS) is observed. We further show that this potential becomes invisible from the left (or right) at certain discrete energies. The penetrating states in the other case (d→id) are always reciprocal even though it is PT-invariant and no spectral singularity (SS) is present in this case. The presence of MSS and reflectionlessness is also discussed for the free states in the later case. -- Highlights: •Existence of multiple spectral singularities (MSS) in PT-symmetric non-Hermitian system is shown. •Reciprocity is restored at discrete positive energies even for parity non-invariant complex system. •Co-existence of MSS with deep energy minima of transitivity is obtained. •Possibilities of both unidirectional and bidirectional invisibility are explored for a non-Hermitian system. •Penetrating states are shown to be reciprocal for all energies for PT-symmetric system.
Nonlinear localized modes in PT-symmetric Rosen-Morse potential well
Midya, Bikashkali
2013-01-01
We report the existence and properties of localized modes described by nonlinear Schroedinger equation with complex PT-symmetric Rosen-Morse potential well. Exact analytical expressions of the localized modes are found in both one dimensional and two-dimensional geometry with self-focusing and self-defocusing Kerr nonlinearity. Linear stability analysis reveals that these localized modes are unstable for all real values of the potential parameters although corresponding linear Schroedinger eigenvalue problem possesses unbroken PT-symmetry. This result has been verified by the direct numerical simulation of the governing equation. The transverse power flow density associated with these localized modes has also been examined.
Quantum mechanics of $PT$ and non-$PT$ -symmetric potentials in three dimensions
Indian Academy of Sciences (India)
BHARDWAJ S B; SINGH RAM MEHAR; MISHRA S C
2016-07-01
With a view of exploring new vistas with regard to the nature of complex eigenspectra of a non-Hermitian Hamiltonian, the quasi-exact solutions of the Schrödinger equation are investigated for a shifted harmonic potential under the framework of extended complex phase-space approach. Analyticity property ofthe eigenfunction alone is found sufficient to throw light on the nature of the eigenvalues and eigenfunctions of a system. Explicit expressions of eigenvalues and eigenfunctions for the ground state as well as excited state including their $PT$-symmetric version are worked out.
Zero width resonance (spectral singularity) in a complex PT-symmetric potential
Ahmed, Zafar
2009-01-01
We show that the complex PT-Symmetric potential, $V(x)=-V_1 {sech}^2x + iV_2 {sech}x ~\\tanh x, $, entails a single zero-width resonance (spectral singularity) when $V_1+|V_2|=4n^2+4n+{3\\over 4}(n=1,2,3.., |V_2|>|V_1|+ {{sgn}(V_1) \\over 4})$ and the positive resonant energy is given as $E_*={1 \\over 4}[|V_2|-(1/4+V_1)]$.
Nonlinear wave dynamics near phase transition in $\\mathcal{PT}$-symmetric localized potentials
Nixon, Sean
2015-01-01
Nonlinear wave propagation in parity-time ($\\mathcal{PT}$) symmetric localized potentials is investigated analytically near a phase-transition point where a pair of real eigenvalues of the potential coalesce and bifurcate into the complex plane. Necessary conditions for phase transition to occur are derived based on a generalization of the Krein signature. Using multi-scale perturbation analysis, a reduced nonlinear ODE model is derived for the amplitude of localized solutions near phase transition. Above phase transition, this ODE model predicts a family of stable solitons not bifurcating from linear (infinitesimal) modes under a certain sign of nonlinearity. In addition, it predicts periodically-oscillating nonlinear modes away from solitons. Under the opposite sign of nonlinearity, it predicts unbounded growth of solutions. Below phase transition, solution dynamics is predicted as well. All analytical results are compared to direct computations of the full system and good agreement is observed.
STABILITY OF BOSE-EINSTEIN CONDENSATES IN A PT-SYMMETRIC DOUBLE-δ POTENTIAL CLOSE TO BRANCH POINTS
Directory of Open Access Journals (Sweden)
Andreas Löhle
2014-04-01
Full Text Available A Bose-Einstein condensate trapped in a double-well potential, where atoms are incoupled to one side and extracted from the other, can in the mean-field limit be described by the nonlinear Gross-Pitaevskii equation (GPE with a PT symmetric external potential. If the strength of the in- and outcoupling is increased two PT broken states bifurcate from the PT symmetric ground state. At this bifurcation point a stability change of the ground state is expected. However, it is observed that this stability change does not occur exactly at the bifurcation but at a slightly different strength of the in-/outcoupling effect. We investigate a Bose-Einstein condensate in a PT symmetric double-δ potential and calculate the stationary states. The ground state’s stability is analysed by means of the Bogoliubov-de Gennes equations and it is shown that the difference in the strength of the in-/outcoupling between the bifurcation and the stability change can be completely explained by the norm-dependency of the nonlinear term in the Gross-Pitaevskii equation.
Indian Academy of Sciences (India)
Fakir Chand; S C Mishra; Ram Mehar Singh
2009-08-01
We investigate the quasi-exact solutions of an analogous Schrödinger wave equation for two-dimensional non-Hermitian complex Hamiltonian systems within the framework of an extended complex phase space characterized by = 1 + 3, = 2 + 4, = 1 + 3, = 2 + 4. Explicit expressions for the energy eigenvalues and eigenfunctions for ground and first excited states of a two-dimensional $\\mathcal{PT}$-symmetric sextic potential and some of its variants are obtained. The eigenvalue spectra are found to be real within some parametric domains.
Hang, Chao; Gabadadze, Gregory; Huang, Guoxiang
2017-02-01
We present a physical setup for realizing all-real-spectrum optical potentials with arbitrary gain-and-loss distributions in a coherent medium consisting of a cold three-level atomic gas driven by control and probe laser fields. We show that by the interference of Raman resonances and the Stark shift induced by a far-detuned laser field, tunable, non-parity-time (non-PT )-symmetric optical potentials with all-real spectra proposed recently by Nixon and Yang [Phys. Rev. A 93, 031802(R) (2016), 10.1103/PhysRevA.93.031802] can be actualized physically. We also show that when the real parts of the non-PT -symmetric optical potentials are tuned cross certain thresholds, phase transitions—where the eigenspectrum of the system changes from all real to complex—may occur and hence the stability of the probe-field propagation is altered. Our scheme can also be extended to high dimensions and to a nonlinear propagation regime, where stable optical solitons with power of the order of nano-Watts may be generated in the system.
Joglekar, Yogesh N
2010-01-01
We study the properties of a parity- and time-reversal- (PT) symmetric tight-binding chain of size N with position-dependent hopping amplitude. In contrast to the fragile PT-symmetric phase of a chain with constant hopping and imaginary impurity potentials, we show that, under very general conditions, our model is {\\it always} in the PT-symmetric phase. We numerically obtain the energy spectrum and the density of states of such a chain, and show that they are widely tunable. By studying the size-dependence of inverse participation ratios, we show that although the chain is not translationally invariant, most of its eigenstates are extended. Our results indicate that tight-binding models with non-Hermitian PT-symmetric hopping have a robust PT-symmetric phase and rich dynamics.
Bender, Carl M.
2015-07-01
The average quantum physicist on the street would say that a quantum-mechanical Hamiltonian must be Dirac Hermitian (invariant under combined matrix transposition and complex conjugation) in order to guarantee that the energy eigenvalues are real and that time evolution is unitary. However, the Hamiltonian H = p2 + ix3, which is obviously not Dirac Hermitian, has a positive real discrete spectrum and generates unitary time evolution, and thus it defines a fully consistent and physical quantum theory. Evidently, the axiom of Dirac Hermiticity is too restrictive. While H = p2 + ix3 is not Dirac Hermitian, it is PT symmetric; that is, invariant under combined parity P (space reflection) and time reversal T. The quantum mechanics defined by a PT-symmetric Hamiltonian is a complex generalization of ordinary quantum mechanics. When quantum mechanics is extended into the complex domain, new kinds of theories having strange and remarkable properties emerge. In the past few years, some of these properties have been verified in laboratory experiments. A particularly interesting PT-symmetric Hamiltonian is H = p2 - x4, which contains an upside-down potential. This potential is discussed in detail, and it is explained in intuitive as well as in rigorous terms why the energy levels of this potential are real, positive, and discrete. Applications of PT-symmetry in quantum field theory are also discussed.
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo, E-mail: paolo.amore@gmail.com [Facultad de Ciencias, CUICBAS, Universidad de Colima, Bernal Díaz del Castillo 340, Colima, Colima (Mexico); Fernández, Francisco M., E-mail: fernande@quimica.unlp.edu.ar [INIFTA (UNLP, CCT La Plata-CONICET), División Química Teórica, Diag. 113 y 64 (S/N), Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina); Garcia, Javier [INIFTA (UNLP, CCT La Plata-CONICET), División Química Teórica, Diag. 113 y 64 (S/N), Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina); Gutierrez, German [Facultad de Ciencias, CUICBAS, Universidad de Colima, Bernal Díaz del Castillo 340, Colima, Colima (Mexico)
2014-04-15
We study both analytically and numerically the spectrum of inhomogeneous strings with PT-symmetric density. We discuss an exactly solvable model of PT-symmetric string which is isospectral to the uniform string; for more general strings, we calculate exactly the sum rules Z(p)≡∑{sub n=1}{sup ∞}1/E{sub n}{sup p}, with p=1,2,… and find explicit expressions which can be used to obtain bounds on the lowest eigenvalue. A detailed numerical calculation is carried out for two non-solvable models depending on a parameter, obtaining precise estimates of the critical values where pair of real eigenvalues become complex. -- Highlights: •PT-symmetric Hamiltonians exhibit real eigenvalues when PT symmetry is unbroken. •We study PT-symmetric strings with complex density. •They exhibit regions of unbroken PT symmetry. •We calculate the critical parameters at the boundaries of those regions. •There are exact real sum rules for some particular complex densities.
Classical irregular blocks, Hill's equation and PT-symmetric periodic complex potentials
Piatek, Marcin
2016-01-01
The Schroedinger eigenvalue problems for the Whittaker-Hill potential $Q_{2}(x)=\\tfrac{1}{2} h^2\\cos4x+4h\\mu\\cos2x$ and the periodic complex potential $Q_{1}(x)=\\tfrac{1}{4}h^2{\\rm e}^{-4ix}+2h^2\\cos2x$ are studied using their realizations in two-dimensional conformal field theory (2dCFT). It is shown that for the weak coupling (small) $h\\in\\mathbb{R}$ and non-integer Floquet parameter $\
Nonlinear wave dynamics near phase transition in PT-symmetric localized potentials
Nixon, Sean; Yang, Jianke
2016-09-01
Nonlinear wave propagation in parity-time symmetric localized potentials is investigated analytically near a phase-transition point where a pair of real eigenvalues of the potential coalesce and bifurcate into the complex plane. Necessary conditions for a phase transition to occur are derived based on a generalization of the Krein signature. Using the multi-scale perturbation analysis, a reduced nonlinear ordinary differential equation (ODE) is derived for the amplitude of localized solutions near phase transition. Above the phase transition, this ODE predicts a family of stable solitons not bifurcating from linear (infinitesimal) modes under a certain sign of nonlinearity. In addition, it predicts periodically-oscillating nonlinear modes away from solitons. Under the opposite sign of nonlinearity, it predicts unbounded growth of solutions. Below the phase transition, solution dynamics is predicted as well. All analytical results are compared to direct computations of the full system and good agreement is observed.
Directory of Open Access Journals (Sweden)
Yi-Xiang Chen
Full Text Available Two families of Gaussian-type soliton solutions of the (n+1-dimensional Schrödinger equation with cubic and power-law nonlinearities in PT-symmetric potentials are analytically derived. As an example, we discuss some dynamical behaviors of two dimensional soliton solutions. Their phase switches, powers and transverse power-flow densities are discussed. Results imply that the powers flow and exchange from the gain toward the loss regions in the PT cell. Moreover, the linear stability analysis and the direct numerical simulation are carried out, which indicates that spatial Gaussian-type soliton solutions are stable below some thresholds for the imaginary part of PT-symmetric potentials in the defocusing cubic and focusing power-law nonlinear medium, while they are always unstable for all parameters in other media.
PT-Symmetric Quantum Electrodynamics
Bender, C M; Milton, K A; Shajesh, K V; Bender, Carl M.; Cavero-Pelaez, Ines; Milton, Kimball A.
2005-01-01
The Hamiltonian for quantum electrodynamics becomes non-Hermitian if the unrenormalized electric charge $e$ is taken to be imaginary. However, if one also specifies that the potential $A^\\mu$ in such a theory transforms as a pseudovector rather than a vector, then the Hamiltonian becomes PT symmetric. The resulting non-Hermitian theory of electrodynamics is the analog of a spinless quantum field theory in which a pseudoscalar field $\\phi$ has a cubic self-interaction of the form $i\\phi^3$. The Hamiltonian for this cubic scalar field theory has a positive spectrum, and it has recently been demonstrated that the time evolution of this theory is unitary. The proof of unitarity requires the construction of a new operator called C, which is then used to define an inner product with respect to which the Hamiltonian is self-adjoint. In this paper the corresponding C operator for non-Hermitian quantum electrodynamics is constructed perturbatively. This construction demonstrates the unitarity of the theory. Non-Hermit...
Anomalous doublets of states in a PT symmetric quantum model
Znojil, M; Roy, P; Roychoudhury, R; Znojil, Miloslav; Levai, Geza; Roy, Pinaki; Roychoudhury, Rajkumar
2001-01-01
A PT symmetric complexification of a conditionally exactly solvable potential in one dimension leads to a paradox. The set of its normalizable solutions proves larger than one would expect on the basis of its point canonical transformation analysis.
Nonlinear waves in $\\cal PT$-symmetric systems
Konotop, Vladimir V.; Yang, Jianke; Zezyulin, Dmitry A.
2016-01-01
Recent progress on nonlinear properties of parity-time ($\\cal PT$-) symmetric systems is comprehensively reviewed in this article. $\\cal PT$ symmetry started out in non-Hermitian quantum mechanics, where complex potentials obeying $\\cal PT$ symmetry could exhibit all-real spectra. This concept later spread out to optics, Bose-Einstein condensates, electronic circuits, and many other physical fields, where a judicious balancing of gain and loss constitutes a $\\cal PT$-symmetric system. The nat...
Dirichlet spectra of the paradigm model of complex PT-symmetric potential: V(x) = -(ix) N
Ahmed, Zafar; Kumar, Sachin; Sharma, Dhruv
2017-08-01
So far the spectra En(N) of the paradigm model of complex PT(Parity-Time)-symmetric potential VBB(x , N) = -(ix) N is known to be analytically continued for N > 4. Consequently, the well known eigenvalues of the Hermitian cases (N = 6 , 10) cannot be recovered. Here, we illustrate Kato's theorem that even if a Hamiltonian H(λ) is an analytic function of a real parameter λ, its eigenvalues En(λ) may not be analytic at finite number of Isolated Points (IPs). In this light, we present the Dirichlet spectra En(N) of VBB(x , N) for 2 ≤ N < 12 using the numerical integration of Schrödinger equation with ψ(x = ± ∞) = 0 and the diagonalization of H =p2 / 2 μ +VBB(x , N) in the harmonic oscillator basis. We show that these real discrete spectra are consistent with the most simple two-turning point CWKB (C refers to complex turning points) method provided we choose the maximal turning points (MxTP) [ - a + ib , a + ib , a , b ∈ R] such that | a | is the largest for a given energy among all (multiple) turning points. We find that En(N) are continuous function of N but non-analytic (their first derivative is discontinuous) at IPs N = 4 , 8; where the Dirichlet spectrum is null (as VBB becomes a Hermitian flat-top potential barrier). At N = 6 and 10, VBB(x , N) becomes a Hermitian well and we recover its well known eigenvalues.
On the integrability of PT-symmetric dimers
Pickton, J
2013-01-01
The coupled discrete linear and Kerr nonlinear Schrodinger equations with gain and loss describing transport on dimers with parity-time (PT) symmetric potentials are considered. The model is relevant among others to experiments in optical couplers and proposals on Bose-Einstein condensates in PT symmetric double-well potentials. It is shown that the models are integrable. A pendulum equation with a linear potential and a constant force for the phase-difference between the fields is obtained, which explains the presence of unbounded solutions above a critical threshold parameter.
Nonlinear waves in $\\cal PT$-symmetric systems
Konotop, Vladimir V; Zezyulin, Dmitry A
2016-01-01
Recent progress on nonlinear properties of parity-time ($\\cal PT$-) symmetric systems is comprehensively reviewed in this article. $\\cal PT$ symmetry started out in non-Hermitian quantum mechanics, where complex potentials obeying $\\cal PT$ symmetry could exhibit all-real spectra. This concept later spread out to optics, Bose-Einstein condensates, electronic circuits, and many other physical fields, where a judicious balancing of gain and loss constitutes a $\\cal PT$-symmetric system. The natural inclusion of nonlinearity into these $\\cal PT$ systems then gave rise to a wide array of new phenomena which have no counterparts in traditional dissipative systems. Examples include the existence of continuous families of nonlinear modes and integrals of motion, stabilization of nonlinear modes above $\\cal PT$-symmetry phase transition, symmetry breaking of nonlinear modes, distinctive soliton dynamics, and many others. In this article, nonlinear $\\cal PT$-symmetric systems arising from various physical disciplines ...
Invisibility in PT-symmetric complex crystals
Energy Technology Data Exchange (ETDEWEB)
Longhi, Stefano, E-mail: longhi@fisi.polimi.it [Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano (Italy)
2011-12-02
Bragg scattering in sinusoidal PT-symmetric complex crystals of finite thickness is theoretically investigated by the derivation of exact analytical expressions for reflection and transmission coefficients in terms of modified Bessel functions of first kind. The analytical results indicate that unidirectional invisibility, recently predicted for such crystals by coupled-mode theory (Z Lin et al 2011 Phys. Rev. Lett. http://dx.doi.org/10.1103/PhysRevLett.106.213901), breaks down for crystals containing a large number of unit cells. In particular, for a given modulation depth in a shallow sinusoidal potential, three regimes are encountered as the crystal thickness is increased. At short lengths the crystal is reflectionless and invisible when probed from one side (unidirectional invisibility), whereas at intermediate lengths the crystal remains reflectionless but not invisible; for longer crystals both unidirectional reflectionless and invisibility properties are broken. (paper)
PT-Symmetric Quantum Field Theory
Milton, K A
2003-01-01
In the context of the PT-symmetric version of quantum electrodynamics, it is argued that the C operator introduced in order to define a unitary inner product has nothing to do with charge conjugation.
Scattering properties of PT-symmetric objects
Miri, Mohammad-Ali; Facao, Margarida; Abouraddy, Ayman F; Bakry, Ahmed; Razvi, Mir A N; Alshahrie, Ahmed; Alù, Andrea; Christodoulides, Demetrios N
2016-01-01
We investigate the scattering response of parity-time (PT) symmetric structures. We show that, due to the local flow of energy between gain and loss regions, such systems can deflect light in unusual ways, as a function of the gain/loss contrast. Such structures are highly anisotropic and their scattering patterns can drastically change as a function of the angle of incidence. In addition, we derive a modified optical theorem for PT-symmetric scattering systems, and discuss its ramifications.
Robust PT-symmetric chain and properties of its Hermitian counterpart
Joglekar, Yogesh N.; Saxena, Avadh
2011-05-01
We study the properties of a parity- and time-reversal- (PT) symmetric tight-binding chain of size N with position-dependent hopping amplitude. In contrast to the fragile PT-symmetric phase of a chain with constant hopping and imaginary impurity potentials, we show that, under very general conditions, our model is always in the PT-symmetric phase. We numerically obtain the energy spectrum and the density of states of such a chain, and show that they are widely tunable. By studying the size dependence of inverse participation ratios, we show that although the chain is not translationally invariant, most of its eigenstates are extended. Our results indicate that tight-binding models with non-Hermitian, PT-symmetric hopping have a robust PT-symmetric phase and rich dynamics which may be explored in coupled waveguides.
PT-Symmetric Optomechanically-Induced Transparency
Jing, H; Özdemir, S K; Zhang, J; Lü, X -Y; Peng, B; Yang, L; Nori, F
2014-01-01
Optomechanically-induced transparency (OMIT) and the associated slow-light propagation provide the basis for storing photons in nanofabricated phononic devices. Here we study OMIT in parity-time (PT)-symmetric microresonators with a tunable gain-to-loss ratio. This system features a reversed, non-amplifying transparency: inverted-OMIT. When the gain-to-loss ratio is steered, the system exhibits a transition from the PT-symmetric phase to the broken-PT-symmetric phase. We show that by tuning the pump power at fixed gain-to-loss ratio or the gain-to-loss ratio at fixed pump power, one can switch from slow to fast light and vice versa. Moreover, the presence of PT-phase transition results in the reversal of the pump and gain dependence of transmission rates. These features provide new tools for controlling light propagation using optomechanical devices.
Non-Hermitian supersymmetry and singular PT symmetrized oscillators
Znojil, M
2002-01-01
SUSY partnership between singular potentials often breaks down. Via regularization it can be restored on certain ad hoc subspaces of Hilbert space [Das and Pernice, Nucl. Phys. B 561 (1999) 357]. Within the naturally complexified (so called PT symmetric) quantum mechanics we show how SUSY between strongly singular harmonic oscillators can completely be re-established. Our recipe leads to a new form of the bosonic creation and annihilation operators and proves continuous near the usual regular (i.e., linear harmonic) limit.
PT -symmetric model of immune response
Bender, Carl M.; Ghatak, Ananya; Gianfreda, Mariagiovanna
2017-01-01
The study of PT -symmetric physical systems began in 1998 as a complex generalization of conventional quantum mechanics, but beginning in 2007 experiments began to be published in which the predicted PT phase transition was clearly observed in classical rather than in quantum-mechanical systems. This paper examines the classical PT phase transition in dynamical-system models that are moderately accurate representations of antigen-antibody systems. A surprising conclusion that can be drawn from these models is that it might be possible treat a serious disease in which the antigen concentration grows out of bounds (and the host dies) by injecting a small dose of a second (different) antigen. In this case a PT -symmetric analysis shows there are two possible favorable outcomes. In the unbroken-PT -symmetric phase the disease becomes chronic and is no longer lethal, while in the appropriate broken-PT -symmetric phase the concentration of lethal antigen goes to zero and the disease is completely cured.
Revisiting the Optical PT-Symmetric Dimer
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José Delfino Huerta Morales
2016-08-01
Full Text Available Optics has proved a fertile ground for the experimental simulation of quantum mechanics. Most recently, optical realizations of PT -symmetric quantum mechanics have been shown, both theoretically and experimentally, opening the door to international efforts aiming at the design of practical optical devices exploiting this symmetry. Here, we focus on the optical PT -symmetric dimer, a two-waveguide coupler where the materials show symmetric effective gain and loss, and provide a review of the linear and nonlinear optical realizations from a symmetry-based point of view. We go beyond a simple review of the literature and show that the dimer is just the smallest of a class of planar N-waveguide couplers that are the optical realization of the Lorentz group in 2 + 1 dimensions. Furthermore, we provide a formulation to describe light propagation through waveguide couplers described by non-Hermitian mode coupling matrices based on a non-Hermitian generalization of the Ehrenfest theorem.
Revisiting the optical $PT$-symmetric dimer
Morales, J D Huerta; López-Aguayo, S; Rodríguez-Lara, B M
2016-01-01
Optics has proved a fertile ground for the experimental simulation of quantum mechanics. Most recently, optical realizations of $\\mathcal{PT}$-symmetric quantum mechanics have been shown, both theoretically and experimentally, opening the door to international efforts aiming at the design of practical optical devices exploiting this symmetry. Here, we focus on the optical $\\mathcal{PT}$-symmetric dimer, a two-waveguide coupler were the materials show symmetric effective gain and loss, and provide a review of the linear and nonlinear optical realizations from a symmetry based point of view. We go beyond a simple review of the literature and show that the dimer is just the smallest of a class of planar $N$-waveguide couplers that are the optical realization of Lorentz group in 2+1 dimensions. Furthermore, we provide a formulation to describe light propagation through waveguide couplers described by non-Hermitian mode coupling matrices based on a non-Hermitian generalization of Ehrenfest theorem.
Experimental demonstration of PT-symmetric stripe lasers
Gu, Zhiyuan; Lyu, Quan; Li, Meng; Xiao, Shumin; Song, Qinghai
2015-01-01
Recently, the coexistence of parity-time (PT) symmetric laser and absorber has gained tremendous research attention. While the PT symmetric absorber has been observed in microwave metamaterials, the experimental demonstration of PT symmetric laser is still absent. Here we experimentally study PT-symmetric laser absorber in stripe waveguide. Using the concept of PT symmetry to exploit the light amplification and absorption, PT-symmetric laser absorbers have been successfully obtained. Different from the single-mode PT symmetric lasers, the PT-symmetric stripe lasers have been experimentally confirmed by comparing the relative wavelength positions and mode spacing under different pumping conditions. When the waveguide is half pumped, the mode spacing is doubled and the lasing wavelengths shift to the center of every two initial lasing modes. All these observations are consistent with the theoretical predictions and confirm the PT-symmetry breaking well.
PT-symmetric deformations of integrable models.
Fring, Andreas
2013-04-28
We review recent results on new physical models constructed as PT-symmetrical deformations or extensions of different types of integrable models. We present non-Hermitian versions of quantum spin chains, multi-particle systems of Calogero-Moser-Sutherland type and nonlinear integrable field equations of Korteweg-de Vries type. The quantum spin chain discussed is related to the first example in the series of the non-unitary models of minimal conformal field theories. For the Calogero-Moser-Sutherland models, we provide three alternative deformations: a complex extension for models related to all types of Coxeter/Weyl groups; models describing the evolution of poles in constrained real-valued field equations of nonlinear integrable systems; and genuine deformations based on antilinearly invariant deformed root systems. Deformations of complex nonlinear integrable field equations of Korteweg-de Vries type are studied with regard to different kinds of PT-symmetrical scenarios. A reduction to simple complex quantum mechanical models currently under discussion is presented.
Scattering properties of PT- symmetric layered periodic structures
Shramkova, O. V.; Tsironis, G. P.
2016-10-01
The optical properties of PT-symmetric periodic stacks of the layers with balanced loss and gain are examined. We demonstrate that the tunnelling phenomenon in periodic structures is connected with excitation of surface waves at the boundaries separating gain and loss regions within each unit cell and tunnelling conditions for periodic stacks can be reduced to the conditions for one period. Alternatively, it is shown that coherent perfect absorber laser states are mediated by excitation of surface modes localised at all internal boundaries of the structure. The effects of structure parameters, angles, direction of incidence on the resonant phenomena and spontaneous symmetry breaking transition are determined. It is shown that structural periodicity significantly increases the number of resonant phenomena, especially in stacks with high real and imaginary parts of dielectric permittivity of the layers.
Stability analysis for solitons in PT-symmetric optical lattices
Nixon, Sean; Yang, Jianke
2012-01-01
Stability of solitons in parity-time (PT)-symmetric periodic potentials (optical lattices) is analyzed in both one- and two-dimensional systems. First we show analytically that when the strength of the gain-loss component in the PT lattice rises above a certain threshold (phase-transition point), an infinite number of linear Bloch bands turn complex simultaneously. Second, we show that while stable families of solitons can exist in PT lattices, increasing the gain-loss component has an overall destabilizing effect on soliton propagation. Specifically, when the gain-loss component increases, the parameter range of stable solitons shrinks as new regions of instability appear. Thirdly, we investigate the nonlinear evolution of unstable PT solitons under perturbations, and show that the energy of perturbed solitons can grow unbounded even though the PT lattice is below the phase transition point.
Jamming anomaly in $\\mathcal{PT}$-symmetric systems
Barashenkov, I V; Konotop, Vladimir V
2016-01-01
The Schr\\"odinger equation with a $\\mathcal{PT}$-symmetric potential is used to model an optical structure consisting of an element with gain coupled to an element with loss. At low gain-loss amplitudes $\\gamma$, raising the amplitude results in the energy flux from the active to the leaky element being boosted. We study the anomalous behaviour occurring for larger $\\gamma$, where the increase of the amplitude produces a drop of the flux across the gain-loss interface. We show that this jamming anomaly is either a precursor of the exceptional point, where two real eigenvalues coalesce and acquire imaginary parts, or precedes the eigenvalue's immersion in the continuous spectrum.
PT-symmetric $\\varphi^4$ theory in d=0 dimensions
Bender, Carl M; Messina, Emanuele
2015-01-01
A detailed study of a PT-symmetric zero-dimensional quartic theory is presented and a comparison between the properties of this theory and those of a conventional quartic theory is given. It is shown that the PT-symmetric quartic theory evades the consequences of the Mermin-Wagner-Coleman theorem regarding the absence of symmetry breaking in d<2 dimensions. Furthermore, the PT-symmetric theory does not satisfy the usual Bogoliubov limit for the construction of the Green's functions because one obtains different results for the $h\\to0^-$ and the $h\\to0^+$ limits.
Cliffordized NAC supersymmetry and PT-symmetric Hamiltonians
Energy Technology Data Exchange (ETDEWEB)
Toppan, Francesco [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]. E-mail: toppan@cbpf.br
2007-07-01
It is shown that non-anti commutative supersymmetry can be described through a Cliffordization of the superspace fermionic coordinates. A NAC supersymmetric quantum mechanical model is shown to be a PT-symmetric Hamiltonian. (author)
Analytic Results for a PT-symmetric Optical Structure
Jones, H F
2011-01-01
Propagation of light through media with a complex refractive index in which gain and loss are engineered to be $PT$ symmetric has many remarkable features. In particular the usual unitarity relations are not satisfied, so that the reflection coefficients can be greater than one, and in general are not the same for left or right incidence. Within the class of optical potentials of the form $v(x)=v_1\\cos(2\\beta x)+iv_2\\sin(2\\beta x)$ the case $v_2=v_1$ is of particular interest, as it lies on the boundary of $PT$-symmetry breaking. It has been shown in a recent paper by Lin et al. that in this case one has the property of "unidirectional invisibility", while for propagation in the other direction there is a greatly enhanced reflection coefficient proportional to $L^2$, where $L$ is the length of the medium in the direction of propagation. For this potential we show how analytic expressions can be obtained for the various transmission and reflection coefficients, which are expressed in a very succinct form in te...
Nonlinear switching and solitons in PT-symmetric photonic systems
Suchkov, Sergey V; Huang, Jiahao; Dmitriev, Sergey V; Lee, Chaohong; Kivshar, Yuri S
2015-01-01
One of the challenges of the modern photonics is to develop all-optical devices enabling increased speed and energy efficiency for transmitting and processing information on an optical chip. It is believed that the recently suggested Parity-Time (PT) symmetric photonic systems with alternating regions of gain and loss can bring novel functionalities. In such systems, losses are as important as gain and, depending on the structural parameters, gain compensates losses. Generally, PT systems demonstrate nontrivial non-conservative wave interactions and phase transitions, which can be employed for signal filtering and switching, opening new prospects for active control of light. In this review, we discuss a broad range of problems involving nonlinear PT-symmetric photonic systems with an intensity-dependent refractive index. Nonlinearity in such PT symmetric systems provides a basis for many effects such as the formation of localized modes, nonlinearly-induced PT-symmetry breaking, and all-optical switching. Nonl...
IS PT -SYMMETRIC QUANTUM THEORY FALSE AS A FUNDAMENTAL THEORY?
Directory of Open Access Journals (Sweden)
Miloslav Znojil
2016-06-01
Full Text Available Yi-Chan Lee et al. claim (cf. Phys. Rev. Lett. 112, 130404 (2014 that the “recent extension of quantum theory to non-Hermitian Hamiltonians” (which is widely known under the nickname of “PT-symmetric quantum theory” is “likely false as a fundamental theory”. By their opinion their results “essentially kill any hope of PT-symmetric quantum theory as a fundamental theory of nature”. In our present text we explain that their toy-model-based considerations are misleading and that they do not imply any similar conclusions.
Nonreciprocal Scattering by PT-symmetric stack of the layers
Shramkova, Oksana
2015-01-01
The nonreciprocal wave propagation in PT-symmetric periodic stack of binary dielectric layers characterised by balances loss and gain is analysed. The main mechanisms and resonant properties of the scattered plane waves are illustrated by the simulation results, and the effects of the periodicity and individual layer parameters on the stack nonreciprocal response are discussed. Gaussian beam dynamics in this type of structure is examined. The beam splitting in PT-symmetric periodic structure is observed. It is demonstrated that for slant beam incidence the break of the symmetry of field distribution takes place.
Three-dimensional topological solitons in PT-symmetric optical lattices
Kartashov, Yaroslav V; Huang, Guoxiang; Torner, Lluis
2016-01-01
We address the properties of fully three-dimensional solitons in complex parity-time (PT)-symmetric periodic lattices with focusing Kerr nonlinearity, and uncover that such lattices can stabilize both, fundamental and vortex-carrying soliton states. The imaginary part of the lattice induces internal currents in the solitons that strongly affect their domains of existence and stability. The domain of stability for fundamental solitons can extend nearly up to the PT-symmetry breaking point, where the linear lattice spectrum becomes complex. Vortex solitons feature spatially asymmetric profiles in the PT-symmetric lattices, but they are found to still exist as stable states within narrow regions. Our results provide the first example of continuous families of stable three-dimensional propagating solitons supported by complex potentials.
Controlling of blow-up responses by nonlinear PT -symmetric coupling
Karthiga, S.; Chandrasekar, V. K.; Senthilvelan, M.; Lakshmanan, M.
2017-03-01
We investigate the dynamics of a coupled waveguide system with competing linear and nonlinear loss-gain profiles which can facilitate power saturation. We show the usefulness of the model in achieving unidirectional beam propagation. In this regard, the considered type of coupled waveguide system has two drawbacks: (i) difficulty in achieving perfect isolation of light in a waveguide and (ii) existence of blow-up-type behavior for certain input power situations. We here show a nonlinear PT -symmetric coupling that helps to overcome these two drawbacks. Such a nonlinear coupling has close connection with the phenomenon of stimulated Raman scattering. In particular, we have elucidated the role of this nonlinear coupling using an integrable PT -symmetric situation. In particular, using the integrals of motion, we have reduced this coupled waveguide problem to the problem of dynamics of a particle in a potential. With the latter picture, we have clearly illustrated the role of the considered nonlinear coupling. The above PT -symmetric case corresponds to a limiting form of a general equation describing the phenomenon of stimulated Raman scattering. We also point out the ability to transport light unidirectionally even in this general case.
PT-symmetric ladders with a scattering core
Energy Technology Data Exchange (ETDEWEB)
D' Ambroise, J. [Department of Mathematics, Amherst College, Amherst, MA 01002-5000 (United States); Lepri, S. [CNR – Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi, via Madonna del piano 10, I-50019 Sesto Fiorentino (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Firenze, via G. Sansone 1, I-50019 Sesto Fiorentino (Italy); Malomed, B.A. [Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel); Kevrekidis, P.G. [Department of Mathematics and Statistics, University of Massachusetts, Amherst, MA 01003-9305 (United States)
2014-08-01
We consider a PT-symmetric chain (ladder-shaped) system governed by the discrete nonlinear Schrödinger equation where the cubic nonlinearity is carried solely by two central “rungs” of the ladder. Two branches of scattering solutions for incident plane waves are found. We systematically construct these solutions, analyze their stability, and discuss non-reciprocity of the transmission associated with them. To relate the results to finite-size wavepacket dynamics, we also perform direct simulations of the evolution of the wavepackets, which confirm that the transmission is indeed asymmetric in this nonlinear system with the mutually balanced gain and loss. - Highlights: • We model a PT-symmetric ladder system with cubic nonlinearity on two central rungs. • We examine non-reciprocity and stability of incident plane waves. • Simulations of wavepackets confirm our results.
PT-symmetric phase in kagome photonic lattices
Chern, Gia-Wei
2015-01-01
Kagome lattice is a two-dimensional network of corner-sharing triangles and is often associated with geometrical frustration. In particular, the frustrated coupling between waveguide modes in a kagome array leads to a dispersionless flat band consisting of spatially localized modes. Here we propose a complex photonic lattice by placing $\\mathcal{PT}$-symmetric dimers at the kagome lattice points. Each dimer corresponds to a pair of strongly coupled waveguides. With balanced arrangement of gain and loss on individual dimers, the system exhibits a $\\mathcal{PT}$-symmetric phase for finite gain/loss parameter up to a critical value. The beam evolution in this complex kagome waveguide array exhibits a novel oscillatory rotation of optical power along the propagation distance. Long-lived local chiral structures originating from the nearly flat bands of the kagome structure are observed when the lattice is subject to a narrow beam excitation.
PT-symmetric phase in kagome-based photonic lattices.
Chern, Gia-Wei; Saxena, Avadh
2015-12-15
The kagome lattice is a two-dimensional network of corner-sharing triangles and is often associated with geometrical frustration. In particular, the frustrated coupling between waveguide modes in a kagome array leads to a dispersionless flat band consisting of spatially localized modes. Here we propose a complex photonic lattice by placing PT-symmetric dimers at the kagome lattice points. Each dimer corresponds to a pair of strongly coupled waveguides. With balanced arrangement of gain and loss on individual dimers, the system exhibits a PT-symmetric phase for finite gain/loss parameter up to a critical value. The beam evolution in this complex kagome waveguide array exhibits a novel oscillatory rotation of optical power along the propagation distance. Long-lived local chiral structures originating from the nearly flat bands of the kagome structure are observed when the lattice is subject to a narrow beam excitation.
PT-Symmetric Cubic Anharmonic Oscillator as a Physical Model
Mostafazadeh, A
2004-01-01
We perform a perturbative calculation of the physical observables, in particular pseudo-Hermitian position and momentum operators, the equivalent Hermitian Hamiltonian operator, and the classical Hamiltonian for the PT-symmetric cubic anharmonic oscillator, $ H=p^1/(2m)+\\mu^2x^2/2+i\\epsilon x^3 $. Ignoring terms of order $ \\epsilon^4 $ and higher, we show that this system describes an ordinary quartic anharmonic oscillator with a position-dependent mass and real and positive coupling constants. This observation elucidates the classical origin of the reality and positivity of the energy spectrum. We also discuss the quantum-classical correspondence for this PT-symmetric system, compute the associated conserved probability density, and comment on the issue of factor-ordering in the pseudo-Hermitian canonical quantization of the underlying classical system.
EXCEPTIONAL POINTS IN OPEN AND PT-SYMMETRIC SYSTEMS
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Hichem Eleuch
2014-04-01
Full Text Available Exceptional points (EPs determine the dynamics of open quantum systems and cause also PT symmetry breaking in PT symmetric systems. From a mathematical point of view, this is caused by the fact that the phases of the wavefunctions (eigenfunctions of a non-Hermitian Hamiltonian relative to one another are not rigid when an EP is approached. The system is therefore able to align with the environment to which it is coupled and, consequently, rigorous changes of the system properties may occur. We compare analytically as well as numerically the eigenvalues and eigenfunctions of a 2 × 2 matrix that is characteristic either of open quantum systems at high level density or of PT symmetric optical lattices. In both cases, the results show clearly the influence of the environment on the system in the neighborhood of EPs. Although the systems are very different from one another, the eigenvalues and eigenfunctions indicate the same characteristic features.
Anomalies in PT-Symmetric Quantum Field Theory
Milton, K A
2004-01-01
It is shown that a version of PT-symmetric electrodynamics based on an axial-vector current coupling massless fermions to the photon possesses anomalies and so is rendered nonrenormalizable. An alternative theory is proposed based on the conventional vector current constructed from massive Dirac fields, but in which the PT transformation properties of electromagnetic fields are reversed. Such a theory seems to possess many attractive features.
Unidirectional invisibility induced by PT-symmetric periodic structures.
Lin, Zin; Ramezani, Hamidreza; Eichelkraut, Toni; Kottos, Tsampikos; Cao, Hui; Christodoulides, Demetrios N
2011-05-27
Parity-time (PT) symmetric periodic structures, near the spontaneous PT-symmetry breaking point, can act as unidirectional invisible media. In this regime, the reflection from one end is diminished while it is enhanced from the other. Furthermore, the transmission coefficient and phase are indistinguishable from those expected in the absence of a grating. The phenomenon is robust even in the presence of Kerr nonlinearities, and it can also effectively suppress optical bistabilities. © 2011 American Physical Society
PT-symmetric phase in kagome photonic lattices
Chern, Gia-Wei; Saxena, Avadh
2015-01-01
Kagome lattice is a two-dimensional network of corner-sharing triangles and is often associated with geometrical frustration. In particular, the frustrated coupling between waveguide modes in a kagome array leads to a dispersionless flat band consisting of spatially localized modes. Here we propose a complex photonic lattice by placing $\\mathcal{PT}$-symmetric dimers at the kagome lattice points. Each dimer corresponds to a pair of strongly coupled waveguides. With balanced arrangement of gai...
Engineering wavefront caustics trajectories in ${\\cal PT}$-symmetric lattices
Bender, Nicholas; Kottos, Tsampikos
2015-01-01
We utilize caustic theory in ${\\cal PT}-$symmetric lattices to design focusing and curved beam dynamics. We show that the gain and loss parameter in these systems provides an addition degree of freedom which allows for the design of the same caustics trajectories with different intensity distribution in the individual waveguides. Moreover we can create aberration-free focal points at any paraxial distance $z_f$, with anomalously large focal intensity.
Super Bloch Oscillation in a PT symmetric system
Turker, Z
2016-01-01
Wannier-Stark ladder in a PT symmetric system is generally complex that leads to amplified/damped Bloch oscillation. We show that a non-amplified wave packet oscillation with very large amplitude can be realized in a non-Hermitian tight binding lattice if certain conditions are satisfied. We show that pseudo PT symmetry guarantees the reality of the quasi energy spectrum in our system.
Bounded dynamics in finite PT-symmetric magnetic metamaterials.
Molina, Mario I
2014-03-01
We examine the PT-symmetry-breaking transition for a magnetic metamaterial of a finite extent, modeled as an array of coupled split-ring resonators in the equivalent circuit model approximation. Small-size arrays are solved completely in closed form, while for arrays larger than N=5 results were computed numerically for several gain and loss spatial distributions. In all cases, it is found that the parameter stability window decreases rapidly with the size of the array, until at N=20 approximately it is not possible to support a stable PT-symmetric phase.
PT-symmetric quantum oscillator in an optical cavity
Longhi, Stefano
2016-01-01
The quantum harmonic oscillator with parity-time ($\\mathcal{PT}$) symmetry, obtained from the ordinary (Hermitian) quantum harmonic oscillator by an imaginary displacement of the spatial coordinate, provides an important and exactly-solvable model to investigate non-Hermitian extension of the Ehrenfest theorem. Here it is shown that transverse light dynamics in an optical resonator with off-axis longitudinal pumping can emulate a $\\mathcal{PT}$-symmetric quantum harmonic oscillator, providing an experimentally accessible system to investigate non-Hermitian coherent state propagation.
$\\mathcal{PT}$-symmetric microring laser-absorber
Longhi, Stefano
2014-01-01
The lasing and coherent perfect absorption (CPA) properties of $\\mathcal{PT}$-symmetric microrings with mixed index and gain gratings, externally coupled to a bus waveguide, are theoretically investigated. For a complex grating at the $\\mathcal{PT}$ symmetry breaking point, perfect unidirectional (either clockwise or counterclockwise) laser emission can be realized, however the grating does not discriminate longitudinal modes and CPA can not be simultaneously achieved. Above the grating $\\mathcal{PT}$ symmetry breaking point, single mode emission and simultaneous CPA can be obtained, with unbalanced and controllable excitation of clockwise and counterclockwise modes in the ring.
Stability of solitons in PT-symmetric couplers
Driben, Rodislav
2011-01-01
Families of analytical solutions are found for symmetric and antisymmetric solitons in the dual-core system with the Kerr nonlinearity and PT-balanced gain and loss. The crucial issue is stability of the solitons. A stability region is obtained in an analytical form, and verified by simulations, for the PT-symmetric solitons. For the antisymmetric ones, the stability border is found in a numerical form. Moving solitons of both types collide elastically. The two soliton species merge into one in the "supersymmetric" case, with equal coefficients of the gain, loss and inter-core coupling. These solitons feature a subexponential instability, which may be suppressed by periodic switching ("management").
Metrology with PT-Symmetric Cavities: Enhanced Sensitivity near the PT-Phase Transition.
Liu, Zhong-Peng; Zhang, Jing; Özdemir, Şahin Kaya; Peng, Bo; Jing, Hui; Lü, Xin-You; Li, Chun-Wen; Yang, Lan; Nori, Franco; Liu, Yu-Xi
2016-09-09
We propose and analyze a new approach based on parity-time (PT) symmetric microcavities with balanced gain and loss to enhance the performance of cavity-assisted metrology. We identify the conditions under which PT-symmetric microcavities allow us to improve sensitivity beyond what is achievable in loss-only systems. We discuss the application of PT-symmetric microcavities to the detection of mechanical motion, and show that the sensitivity is significantly enhanced near the transition point from unbroken- to broken-PT regimes. Our results open a new direction for PT-symmetric physical systems and it may find use in ultrahigh precision metrology and sensing.
Phase transition in PT symmetric active plasmonic systems
Mattheakis, M; Molina, M I; Tsironis, G P
2015-01-01
Surface plasmon polaritons (SPPs) are coherent electromagnetic surface waves trapped on an insulator-conductor interface. The SPPs decay exponentially along the propagation due to conductor losses, restricting the SPPs propagation length to few microns. Gain materials can be used to counterbalance the aforementioned losses. We provide an exact expression for the gain, in terms of the optical properties of the interface, for which the losses are eliminated. In addition, we show that systems characterized by lossless SPP propagation are related to PT symmetric systems. Furthermore, we derive an analytical critical value of the gain describing a phase transition between lossless and prohibited SPPs propagation. The regime of the aforementioned propagation can be directed by the optical properties of the system under scrutiny. Finally, we perform COMSOL simulations verifying the theoretical findings.
PT -symmetric spectral singularity and negative-frequency resonance
Pendharker, Sarang; Guo, Yu; Khosravi, Farhad; Jacob, Zubin
2017-03-01
Vacuum consists of a bath of balanced and symmetric positive- and negative-frequency fluctuations. Media in relative motion or accelerated observers can break this symmetry and preferentially amplify negative-frequency modes as in quantum Cherenkov radiation and Unruh radiation. Here, we show the existence of a universal negative-frequency-momentum mirror symmetry in the relativistic Lorentzian transformation for electromagnetic waves. We show the connection of our discovered symmetry to parity-time (PT ) symmetry in moving media and the resulting spectral singularity in vacuum fluctuation-related effects. We prove that this spectral singularity can occur in the case of two metallic plates in relative motion interacting through positive- and negative-frequency plasmonic fluctuations (negative-frequency resonance). Our work paves the way for understanding the role of PT -symmetric spectral singularities in amplifying fluctuations and motivates the search for PT symmetry in novel photonic systems.
Bright solitons in a PT-symmetric chain of dimers
Kirikchi, Omar B; Susanto, Hadi
2016-01-01
We study the existence and stability of fundamental bright discrete solitons in a parity-time (PT)-symmetric coupler composed by a chain of dimers, that is modelled by linearly coupled discrete nonlinear Schrodinger equations with gain and loss terms. We use a perturbation theory for small coupling between the lattices to perform the analysis, which is then confirmed by numerical calculations. Such analysis is based on the concept of the so-called anti-continuum limit approach. We consider the fundamental onsite and intersite bright solitons. Each solution has symmetric and antisymmetric configurations between the arms. The stability of the solutions is then determined by solving the corresponding eigenvalue problem. We obtain that both symmetric and antisymmetric onsite mode can be stable for small coupling, on the contrary of the reported continuum limit where the antisymmetric solutions are always unstable. The instability is either due to the internal modes crossing the origin or the appearance of a quart...
Ge, Li
2016-01-01
The CPA-laser is a coexisting state of coherent perfect absorption and lasing that was proposed in parity-time ($\\cal PT$) symmetric photonic systems. In this work we show that the spectral signature of a CPA-laser displayed by the singular value spectrum of the scattering matrix ($S$) can be orders of magnitude wider than that displayed by the eigenvalue spectrum of $S$. Since the former reflects how strongly light can be absorbed or amplified and the latter announces the spontaneous symmetry breaking of $S$, these contrasting spectral signatures indicate that near perfect absorption and extremely strong amplification can be achieved even in the $\\cal PT$-symmetric phase of $S$, which is known for and defined by its flux-conserving eigenstates. We also show that these contrasting spectral signatures are accompanied by strikingly different sensitivities to disorder and imperfection, suggesting that the eigenvalue spectrum is potentially suitable for sensing and the singular value spectrum for robust switching...
Tailoring Spectral Properties of Binary PT-Symmetric Gratings by Duty-Cycle Methods
DEFF Research Database (Denmark)
Lupu, Anatole T.; Benisty, Henri; Lavrinenko, Andrei
2016-01-01
We explore the frequency selective functionalities of a nonuniform PT-symmetric Bragg grating with modulated complex index profile. We start by assessing the possibility to achieve an efficient apodization of the PT-symmetric Bragg grating spectral response by using direct adaptations of the conv...
Sublattice signatures of transitions in a $\\mathcal{PT}$-symmetric dimer lattice
Harter, Andrew K
2016-01-01
Lattice models with non-hermitian, parity and time-reversal ($\\mathcal{PT}$) symmetric Hamiltonians, realized most readily in coupled optical systems, have been intensely studied in the past few years. A $\\mathcal{PT}$-symmetric dimer lattice consists of dimers with intra-dimer coupling $\
Singular Mapping for a $PT$-Symmetric Sinusoidal Optical Lattice at the Symmetry-Breaking Threshold
Jones, H F
2014-01-01
A popular $PT$-symmetric optical potential (variation of the refractive index) that supports a variety of interesting and unusual phenomena is the imaginary exponential, the limiting case of the potential $V_0[\\cos(2\\pi x/a)+i\\lambda\\sin(2\\pi x/a)]$ as $\\lambda \\to 1$, the symmetry-breaking point. For $\\lambda<1$, when the spectrum is entirely real, there is a well-known mapping by a similarity transformation to an equivalent Hermitian potential. However, as $\\lambda \\to 1$, the spectrum, while remaining real, contains Jordan blocks in which eigenvalues and the corresponding eigenfunctions coincide. In this limit the similarity transformation becomes singular. Nonetheless, we show that the mapping from the original potential to its Hermitian counterpart can still be implemented; however, the inverse mapping breaks down. We also illuminate the role of Jordan associated functions in the original problem, showing that they map onto eigenfunctions in the associated Hermitian problem.
Kartashov, Yaroslav V; Konotop, Vladimir V; Torner, Lluis
2016-01-01
We address the propagation of light beams in longitudinally modulated PT-symmetric lattices, built as arrays of couplers with periodically varying separation between their channels, and show a number of possibilities for efficient diffraction control available in such non-conservative structures. The dynamics of light in such lattices crucially depends on the ratio of the switching length for the straight segments of each coupler and the longitudinal lattice period. Depending on the longitudinal period, one can achieve either beam rectification, when the input light propagates at a fixed angle across the structure without diffractive broadening, or dynamic localization, when the initial intensity distribution is periodically restored after each longitudinal period. Importantly, the transition between these two different propagation regimes can be achieved by tuning only gain and losses acting in the system, provided that the PT-symmetry remains unbroken. The impact of Kerr nonlinearity is also discussed.
Optical solitons in PT-symmetric nonlinear couplers with gain and loss
Alexeeva, N. V.; Barashenkov, I. V.; Sukhorukov, Andrey A.; Kivshar, Yuri S.
2012-06-01
We study spatial and temporal solitons in the PT symmetric coupler with gain in one waveguide and loss in the other. Stability properties of the high- and low-frequency solitons are found to be completely determined by a single combination of the soliton's amplitude and the gain-loss coefficient of the waveguides. The unstable perturbations of the high-frequency soliton break the symmetry between its active and lossy components which results in a blowup of the soliton or a formation of a long-lived breather state. The unstable perturbations of the low-frequency soliton separate its two components in space, thereby blocking the power drainage of the active component and cutting the power supply to the lossy one. Eventually this also leads to the blowup or breathing.
Optical solitons in $\\mathcal{PT}$-symmetric nonlinear couplers with gain and loss
Alexeeva, N V; Sukhorukov, Andrey A; Kivshar, Yuri S
2012-01-01
We study spatial and temporal solitons in the $\\mathcal{PT}$ symmetric coupler with gain in one waveguide and loss in the other. Stability properties of the high- and low-frequency solitons are found to be completely determined by a single combination of the soliton's amplitude and the gain/loss coefficient of the waveguides. The unstable perturbations of the high-frequency soliton break the symmetry between its active and lossy components which results in a blowup of the soliton or a formation of a long-lived breather state. The unstable perturbations of the low-frequency soliton separate its two components in space blocking the power drainage of the active component and cutting the power supply to the lossy one. Eventually this also leads to the blowup or breathing.
From particle in a box to PT -symmetric systems via isospectral deformation
Cherian, Philip; Panigrahi, P K
2011-01-01
A family of PT -symmetric complex potentials are obtained which is isospectral to free particle in an infinite complex box in one dimension (1-D). These are generalizations to the cosec2(x) potential, isospectral to particle in a real infinite box. In the complex plane, the infinite box is extended parallel to the real axis having a real width, which is found to be an integral multiple of a constant quantum factor, arising due to boundary conditions necessary for maintaining the PT -symmetry of the superpartner. As the spectra of the particle in a box is still real, it necessarily picks out the unbroken PT -sector of its superpartner, thereby invoking a close relation between PT -symmetry and SUSY for this case.
PT-Symmetric Versus Hermitian Formulations of Quantum Mechanics
Bender, C M; Milton, K A; Bender, Carl M.; Chen, Jun-Hua; Milton, Kimball A.
2006-01-01
A non-Hermitian Hamiltonian that has an unbroken PT symmetry can be converted by means of a similarity transformation to a physically equivalent Hermitian Hamiltonian. This raises the following question: In which form of the quantum theory, the non-Hermitian or the Hermitian one, is it easier to perform calculations? This paper compares both forms of a non-Hermitian $ix^3$ quantum-mechanical Hamiltonian and demonstrates that it is much harder to perform calculations in the Hermitian theory because the perturbation series for the Hermitian Hamiltonian is constructed from divergent Feynman graphs. For the Hermitian version of the theory, dimensional continuation is used to regulate the divergent graphs that contribute to the ground-state energy and the one-point Green's function. The results that are obtained are identical to those found much more simply and without divergences in the non-Hermitian PT-symmetric Hamiltonian. The $\\mathcal{O}(g^4)$ contribution to the ground-state energy of the Hermitian version ...
Bright Solitons in a PT-Symmetric Chain of Dimers
Directory of Open Access Journals (Sweden)
Omar B. Kirikchi
2016-01-01
Full Text Available We study the existence and stability of fundamental bright discrete solitons in a parity-time- (PT- symmetric coupler composed by a chain of dimers that is modelled by linearly coupled discrete nonlinear Schrödinger equations with gain and loss terms. We use a perturbation theory for small coupling between the lattices to perform the analysis, which is then confirmed by numerical calculations. Such analysis is based on the concept of the so-called anticontinuum limit approach. We consider the fundamental onsite and intersite bright solitons. Each solution has symmetric and antisymmetric configurations between the arms. The stability of the solutions is then determined by solving the corresponding eigenvalue problem. We obtain that both symmetric and antisymmetric onsite mode can be stable for small coupling, in contrast to the reported continuum limit where the antisymmetric solutions are always unstable. The instability is either due to the internal modes crossing the origin or the appearance of a quartet of complex eigenvalues. In general, the gain-loss term can be considered parasitic as it reduces the stability region of the onsite solitons. Additionally, we analyse the dynamic behaviour of the onsite and intersite solitons when unstable, where typically it is either in the form of travelling solitons or soliton blow-ups.
PT-Symmetric Nonlinear Metamaterials and Zero-Dimensional Systems
Tsironis, G P
2013-01-01
A one dimensional, parity-time (${\\cal PT}$)-symmetric magnetic metamaterial comprising split-ring resonators having both gain and loss is investigated. In the linear regime, the transition from the exact to the broken ${\\cal PT}$-phase is determined through the calculation of the eigenfrequency spectrum for two different configurations; the one with equidistant split-rings and the other with the split-rings forming a binary pattern (${\\cal PT}$ dimer chain). The latter system features a two-band, gapped spectrum with its shape determined by the gain/loss coefficient as well as the inter-element coupling. In the presense of nonlinearity, the ${\\cal PT}$ dimer chain with balanced gain and loss supports nonlinear localized modes in the form of novel discrete breathers below the lower branch of the linear spectrum. These breathers, that can be excited from a weak applied magnetic field by frequency chirping, can be subsequently driven solely by the gain for very long times. The effect of a small imbalance betwee...
Complex {PT}-symmetric extensions of the nonlinear ultra-short light pulse model
Yan, Zhenya
2012-11-01
The short pulse equation u_{xt}=u+\\frac{1}{2}(u^2u_x)_x is PT symmetric, which arises in nonlinear optics for the ultra-short pulse case. We present a family of new complex PT-symmetric extensions of the short pulse equation, i[(iu_x)^{\\sigma }]_t=au+bu^m+ic[u^n(iu_x)^{\\epsilon }]_x \\,\\, (\\sigma ,\\, \\epsilon ,\\,a,\\,b,\\,c,\\,m,\\,n \\in {R}), based on the complex PT-symmetric extension principle. Some properties of these equations with some chosen parameters are studied including the Hamiltonian structures and exact solutions such as solitary wave solutions, doubly periodic wave solutions and compacton solutions. Our results may be useful to understand complex PT-symmetric nonlinear physical models. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Quantum physics with non-Hermitian operators’.
Compactons in $\\mathcal{PT}$-symmetric generalized Korteweg–de Vries equations
Indian Academy of Sciences (India)
Carl M Bender; Fred Cooper; Avinash Khare; Bogdan Mihaila; Avadh Saxena
2009-08-01
This paper considers the $\\mathcal{PT}$-symmetric extensions of the equations examined by Cooper, Shepard and Sodano. From the scaling properties of the $\\mathcal{PT}$-symmetric equations a general theorem relating the energy, momentum and velocity of any solitary-wave solution of the generalized KdV equation is derived. We also discuss the stability of the compacton solution as a function of the parameters affecting the nonlinearities.
From $\\mathcal{PT}$ -symmetric quantum mechanics to conformal field theory
Indian Academy of Sciences (India)
Patrick Dorey; Clare Dunning; Roberto Tateo
2009-08-01
One of the simplest examples of a $\\mathcal{PT}$-symmetric quantum system is the scaling Yang–Lee model, a quantum field theory with cubic interaction and purely imaginary coupling. We give a historical review of some facts about this model in ≤ 2 dimensions, from its original definition in connection with phase transitions in the Ising model and its relevance to polymer physics, to the role it has played in studies of integrable quantum field theory and $\\mathcal{PT}$-symmetric quantum mechanics. We also discuss some more general results on $\\mathcal{PT}$-symmetric quantum mechanics and the ODE/IM correspondence, and mention applications to magnetic systems and cold atom physics.
Floquet control of the gain and loss in a PT-symmetric optical coupler
Wu, Yi; Zhu, Bo; Hu, Shu-Fang; Zhou, Zheng; Zhong, Hong-Hua
2017-02-01
Controlling the balanced gain and loss in a PT-symmetric system is a rather challenging task. Utilizing Floquet theory, we explore the constructive role of periodic modulation in controlling the gain and loss of a PT-symmetric optical coupler. It is found that the gain and loss of the system can be manipulated by applying a periodic modulation. Further, such an original non-Hermitian system can even be modulated into an effective Hermitian system derived by the high-frequency Floquet method. Therefore, compared with other PT symmetry control schemes, our protocol can modulate the unbroken PT-symmetric range to a wider parameter region. Our results provide a promising approach for controlling the gain and loss of a realistic system.
Modulational instability in a PT-symmetric vector nonlinear Schrödinger system
Cole, J. T.; Makris, K. G.; Musslimani, Z. H.; Christodoulides, D. N.; Rotter, S.
2016-12-01
A class of exact multi-component constant intensity solutions to a vector nonlinear Schrödinger (NLS) system in the presence of an external PT-symmetric complex potential is constructed. This type of uniform wave pattern displays a non-trivial phase whose spatial dependence is induced by the lattice structure. In this regard, light can propagate without scattering while retaining its original form despite the presence of inhomogeneous gain and loss. These constant-intensity continuous waves are then used to perform a modulational instability analysis in the presence of both non-hermitian media and cubic nonlinearity. A linear stability eigenvalue problem is formulated that governs the dynamical evolution of the periodic perturbation and its spectrum is numerically determined using Fourier-Floquet-Bloch theory. In the self-focusing case, we identify an intensity threshold above which the constant-intensity modes are modulationally unstable for any Floquet-Bloch momentum belonging to the first Brillouin zone. The picture in the self-defocusing case is different. Contrary to the bulk vector case, where instability develops only when the waves are strongly coupled, here an instability occurs in the strong and weak coupling regimes. The linear stability results are supplemented with direct (nonlinear) numerical simulations.
Nonlinear localized modes in PT-symmetric optical media with competing gain and loss
Energy Technology Data Exchange (ETDEWEB)
Midya, Bikashkali, E-mail: bikash.midya@gmail.com [Physics and Applied Mathematics Unit, Indian Statistical Institute, Kolkata 700108 (India); Roychoudhury, Rajkumar, E-mail: rroychoudhury123@gmail.com [Advanced Center for Nonlinear and Complex Phenomena, Kolkata 700075 (India)
2014-02-15
The existence and stability of the nonlinear spatial localized modes are investigated in parity-time symmetric optical media characterized by a generic complex hyperbolic refractive index distribution with competing gain and loss profile. The exact analytical expression of the localized modes are found for all values of the competing parameter and in the presence of both the self-focusing and self-defocusing Kerr nonlinearity. The effects of competing gain/loss profile on the stability structure of these localized modes are discussed with the help of linear stability analysis followed by the direct numerical simulation of the governing equation. The spatial localized modes in two-dimensional geometry as well as the transverse power-flow density associated with these localized modes are also examined. -- Highlights: • Existence of localized modes is investigated in PT-symmetric complex potentials. • Exact analytical expression of the localized modes is obtained. • Effect of gain/loss profile on the stability of these localized modes is discussed. • Localized modes in 2D and associated transverse power-flow density are also examined.
Perturbation Theory for PT-Symmetric Sinusoidal Optical Lattices at the Symmetry-Breaking Threshold
Jones, H F
2011-01-01
The $PT$ symmetric potential $V_0[\\cos(2\\pi x/a)+i\\lambda\\sin(2\\pi x/a)]$ has a completely real spectrum for $\\lambda\\le 1$, and begins to develop complex eigenvalues for $\\lambda>1$. At the symmetry-breaking threshold $\\lambda=1$ some of the eigenvectors become degenerate, giving rise to a Jordan-block structure for each degenerate eigenvector. In general this is expected to give rise to a secular growth in the amplitude of the wave. However, it has been shown in a recent paper by Longhi, by numerical simulation and by the use of perturbation theory, that for an initial wave packet this growth is suppressed, giving instead a constant maximum amplitude. We revisit this problem by developing the perturbation theory further. We verify that the results found by Longhi persist to second order, and with different input wave packets we are able to see the seeds in perturbation theory of the phenomenon of birefringence first discovered by El-Ganainy et al.
Compactons in PT-symmetric generalized Korteweg-de Vries equations
Energy Technology Data Exchange (ETDEWEB)
Saxena, Avadh B [Los Alamos National Laboratory; Mihaila, Bogdan [Los Alamos National Laboratory; Bender, Carl M [WASHINGTON UNIV; Cooper, Fred [SANTA FE INSTITUTE; Khare, Avinash [INSTITUTE OF PHYSICS
2008-01-01
In an earlier paper Cooper, Shepard, and Sodano introduced a generalized KdV equation that can exhibit the kinds of compacton solitary waves that were first seen in equations studied by Rosenau and Hyman. This paper considers the PT-symmetric extensions of the equations examined by Cooper, Shepard, and Sodano. From the scaling properties of the PT-symmetric equations a general theorem relating the energy, momentum, and velocity of any solitary-wave solution of the generalized KdV equation is derived, and it is shown that the velocity of the solitons is determined by their amplitude, width, and momentum.
Controllable Akhmediev breather and Kuznetsov-Ma soliton trains in PT-symmetric coupled waveguides.
Dai, Chaoqing; Wang, Yueyue; Zhang, Xiaofei
2014-12-01
The PT-symmetric and PT-antisymmetric Akhmediev breather (AB) and Kuznetsov-Ma (KM) soliton train solutions of a (2+1)-dimensional variable-coefficient coupled nonlinear Schrödinger equation in PT-symmetric coupled waveguides with gain and loss are derived via the Darboux transformation method. From these analytical solutions, we investigate the controllable behaviors of AB and KM soliton trains in a diffraction decreasing system with exponential profile. By adjusting the relation between the maximum Zm of effective propagation distance and the peak locations Zi of AB and KM soliton trains, we can control the restraint, maintenance and postpone excitations of AB and KM soliton trains.
Compactons in PT-symmetric generalized Korteweg-de Vries equations
Energy Technology Data Exchange (ETDEWEB)
Saxena, Avadh B [Los Alamos National Laboratory; Mihaila, Bogdan [Los Alamos National Laboratory; Bender, Carl M [WASHINGTON UNIV; Cooper, Fred [SANTA FE INSTITUTE; Khare, Avinash [INSTITUTE OF PHYSICS
2008-01-01
In an earlier paper Cooper, Shepard, and Sodano introduced a generalized KdV equation that can exhibit the kinds of compacton solitary waves that were first seen in equations studied by Rosenau and Hyman. This paper considers the PT-symmetric extensions of the equations examined by Cooper, Shepard, and Sodano. From the scaling properties of the PT-symmetric equations a general theorem relating the energy, momentum, and velocity of any solitary-wave solution of the generalized KdV equation is derived, and it is shown that the velocity of the solitons is determined by their amplitude, width, and momentum.
Longhi, Stefano
2017-01-01
We consider wave transport phenomena in a PT -symmetric extension of the periodically kicked quantum rotator model and reveal that dynamical localization assists the unbroken PT phase. In the delocalized (quantum resonance) regime, PT symmetry is always in the broken phase and ratchet acceleration arises as a signature of unidirectional non-Hermitian transport. An optical implementation of the periodically kicked PT -symmetric Hamiltonian, based on transverse beam propagation in a passive optical resonator with combined phase and loss gratings, is suggested to visualize acceleration modes in fractional Talbot cavities.
Directory of Open Access Journals (Sweden)
Holger Cartarius
2013-01-01
Full Text Available We investigate the Gross-Pitaevskii equation for a Bose-Einstein condensate in a PT symmetric double-well potential by means of the time-dependent variational principle and numerically exact solutions. A one-dimensional and a fully three-dimensional setup are used. Stationary states are determined and the propagation of wave function is investigated using the time-dependent Gross-Pitaevskii equation. Due to the nonlinearity of the Gross-Pitaevskii equation the potential dependson the wave function and its solutions decide whether or not the Hamiltonian itself is PT symmetric. Stationary solutions with real energy eigenvalues fulfilling exact PT symmetry are found as well as PT broken eigenstates with complex energies. The latter describe decaying or growing probability amplitudes and are not true stationary solutions of the time-dependent Gross-Pitaevskii equation. However, they still provide qualitative information about the time evolution of the wave functions.
Anomalous Light Scattering by Topological ${\\mathcal{PT}}$-symmetric Particle Arrays
Ling, C W; Mok, T C; Zhang, Z Q; Fung, Kin Hung
2016-01-01
Robust topological edge modes may evolve into complex-frequency modes when a physical system becomes non-Hermitian. We show that, while having negligible forward optical extinction cross section, a conjugate pair of such complex topological edge modes in a non-Hermitian $\\mathcal{PT}$-symmetric system can give rise to an anomalous sideway scattering when they are simultaneously excited by a plane wave. We propose a realization of such scattering state in a linear array of subwavelength resonators coated with gain media. The prediction is based on an analytical two-band model and verified by rigorous numerical simulation using multiple-multipole scattering theory. The result suggests an extreme situation where leakage of classical information is unnoticeable to the transmitter and the receiver when such a $\\mathcal{PT}$-symmetric unit is inserted into the communication channel.
Non-Hermitian Neutrino Oscillations in Matter with PT Symmetric Hamiltonians
Ohlsson, Tommy
2015-01-01
We introduce and develop a novel approach to extend the ordinary two-flavor neutrino oscillation formalism in matter using a non-Hermitian PT symmetric effective Hamiltonian. The condition of PT symmetry is weaker and less mathematical than that of Hermicity, but more physical, and such an extension of the formalism can give rise to sub-leading effects in neutrino flavor transitions similar to the effects by so-called non-standard neutrino interactions. We derive the necessary conditions for the spectrum of the effective Hamiltonian to be real as well as the mappings between the fundamental and effective parameters including the corresponding two-flavor neutrino transition probability. We find that the effective leptonic mixing must always be maximal and that the real spectrum of the effective Hamiltonian will depend on all new fundamental parameters introduced in the non-Hermitian PT symmetric extension of the usual neutrino oscillation formalism.
A selection rule for transitions in PT-symmetric quantum theory
Mead, Lawrence R
2016-01-01
Carl Bender and collaborators have developed a quantum theory governed by Hamiltonians that are PT-symmetric rather than Hermitian. To implement this theory, the inner product was redefined to guarantee positive norms of eigenstates of the Hamiltonian. In the general case, which includes arbitrary time-dependence in the Hamiltonian, a modification of the Schrodinger equation is necessary as shown by Gong and Wang to conserve probability. In this paper, we derive the following selection rule: transitions induced by time dependence in a PT-symmetric Hamiltonian cannot occur between normalized states of differing PT-norm. We show three examples of this selection rule in action: two matrix models and one in the continuum.
Nonlinear dynamics of wave packets in PT-symmetric optical lattices near the phase transition point
Nixon, Sean; Yang, Jianke
2012-01-01
Nonlinear dynamics of wave packets in PT-symmetric optical lattices near the phase-transition point are analytically studied. A nonlinear Klein-Gordon equation is derived for the envelope of these wave packets. A variety of novel phenomena known to exist in this envelope equation are shown to also exist in the full equation including wave blowup, periodic bound states and solitary wave solutions.
Modulation theory in PT-Symmetric Magnetic Metamaterial Arrays in the continuum limit
Wang, Danhua
2013-01-01
We present results on the dynamics of split-ring dimers having both gain and loss in one dimensional nonlinear parity-time- (PT-)symmetric magnetic metamaterials. For the longwave (continuum) limit approximation and in the weakly nonlinear limit, we show analytic results on the existence of gap soliton solutions and on symmetry breaking phenomenon at a critical value of the gain/loss term.
Remarks on the PT-pseudo-norm in PT-symmetric quantum mechanics
Energy Technology Data Exchange (ETDEWEB)
Duc Tai Trinh [Department of Mathematics, Teacher Training College of Dalat, 29 Yersin, Dalat (Viet Nam)]|[Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, Trieste 34014 (Italy)
2005-04-22
This paper presents an underlying analytical relationship between the PT-pseudo-norm associated with the PT-symmetric Hamiltonian H = p{sup 2} + V(q) and the Stokes multiplier of the differential equation corresponding to this Hamiltonian. We show that the sign alternation of the PT-pseudo-norm, which has been observed as a generic feature of the PT-inner product, is essentially controlled by the derivative of a Stokes multiplier with respect to the eigenparameter.
Indian Academy of Sciences (India)
E Caliceti; S Graffi
2009-08-01
We generalize some recently established criteria for the reality and non-reality of the spectrum of some classes of $\\mathcal{PT}$-symmetric Schrödinger operators. The criteria include cases of discrete spectra and continuous ones.
The Horizons of Observability in PT-symmetric Four-site Quantum Lattices
Directory of Open Access Journals (Sweden)
M. Znojil
2011-01-01
Full Text Available One of the key merits of PT-symmetric (i.e., parity times time reversal symmetric quantum Hamiltonians H lies in the existence of a horizon of the stability of the system. Mathematically speaking, this horizon is formed by the boundary of the domain D(H ⊂ RD of the (real coupling strengths for which the spectrum of energies is real and non-degenerate, i.e., in principle, observable. It is shown here that even in the elementary circular four-site quantum lattices with D = 2 or D = 3 the domain of hidden Hermiticity D(H proves multiply connected, i.e., topologically nontrivial.
All-optical $\\mathcal{PT}$-symmetric amplitude to phase modulator
Gutiérrez, Oscar Ignacio Zaragoza; Rodríguez-Lara, B M
2015-01-01
We study electromagnetic field propagation through a planar three-waveguide coupler with linear gain and loss, in a configuration that is the optical analog of a quantum $\\mathcal{PT}$-symmetric system, and provide its closed-form analytic propagator. At an specific propagation length, we show that the device provides all-optical amplitude to phase modulation with a $\\pi$ modulation range, if an extra binary phase is allowed in the reference signal, as well as phase to amplitude modulation, with an amplitude modulation range that depends linearly on the gain-to-coupling ratio of the system.
Solitons in PT-symmetric periodic systems with the logarithmically saturable nonlinearity
Zhan, Kaiyun; Tian, Hao; Li, Xin; Xu, Xianfeng; Jiao, Zhiyong; Jia, Yulei
2016-09-01
We report on the formation and stability of induced solitons in parity-time (PT) symmetric periodic systems with the logarithmically saturable nonlinearity. Both on-site and off-site lattice solitons exist for the self-focusing nonlinearity. The most intriguing result is that the above solitons can also be realized inside the several higher-order bands of the band structure, due to the change of nonlinear type with the soliton power. Stability analysis shows that on-site solitons are linearly stably, and off-site solitons are unstable in their existence domain.
Kulishov, Mykola; Kress, Bernard
2015-01-01
We study the diffraction produced by a slab of purely reflective PT-symmetric volume Bragg grating that combines modulations of refractive index and gain/loss of the same periodicity with a quarter-period shift between them. Such a complex grating has a directional coupling between the different diffraction orders, which allows us to find an analytic solution for the first three orders of the full Maxwell equations without resorting to the paraxial approximation. This is important, because only with the full equations can the boundary conditions, allowing for the reflections, be properly implemented. Using our solution we analyze unidirectional invisibility of such a grating in a wide variety of configurations.
Families of particles with different masses in PT-symmetric quantum field theory.
Bender, Carl M; Klevansky, S P
2010-07-16
An elementary field-theoretic mechanism is proposed that allows one Lagrangian to describe a family of particles having different masses but otherwise similar physical properties. The mechanism relies on the observation that the Dyson-Schwinger equations derived from a Lagrangian can have many different but equally valid solutions. Nonunique solutions to the Dyson-Schwinger equations arise when the functional integral for the Green's functions of the quantum field theory converges in different pairs of Stokes' wedges in complex-field space, and the solutions are physically viable if the pairs of Stokes' wedges are PT symmetric.
Floquet Topological Phases Driven by $\\mathcal{PT}$ Symmetric Nonunitary Time Evolution
Kim, Dakyeong; Kawakami, Norio; Obuse, Hideaki
2016-01-01
We study Floquet topological phases driven by $\\mathcal{PT}$ symmetric nonunitary time evolution in one dimension, based on an experimental setup of discrete-time quantum walks. We develop, for nonunitary time-evolution operators, a procedure to calculate topological invariants for Floquet topological phases and find that the bulk-edge correspondence gives correct predictions of the emergent edge states. These edge states make exponential growth of wavefunction amplitudes at specific positions with time controllable. Hereby, we propose that these phenomena inherent in open quantum systems are feasibly observed by present experiments of quantum walks in both classical and quantum regimes.
Non-Hermitian neutrino oscillations in matter with PT symmetric Hamiltonians
Ohlsson, Tommy
2016-03-01
We introduce and develop a novel approach to extend the ordinary two-flavor neutrino oscillation formalism in matter using a non-Hermitian PT symmetric effective Hamiltonian. The condition of PT symmetry is weaker and less mathematical than that of hermicity, but more physical, and such an extension of the formalism can give rise to sub-leading effects in neutrino flavor transitions similar to the effects by so-called non-standard neutrino interactions. We derive the necessary conditions for the spectrum of the effective Hamiltonian to be real as well as the mappings between the fundamental and effective parameters. We find that the real spectrum of the effective Hamiltonian will depend on all new fundamental parameters introduced in the non-Hermitian PT symmetric extension of the usual neutrino oscillation formalism and that either i) the spectrum is exact and the effective leptonic mixing must always be maximal or ii) the spectrum is approximate and all new fundamental parameters must be small.
Dynamics of higher-order solitons in regular and PT-symmetric nonlinear couplers
Driben, R
2012-01-01
Dynamics of symmetric and antisymmetric 2-solitons and 3-solitons is studied in the model of the nonlinear dual-core coupler and its PT-symmetric version. Regions of the convergence of the injected perturbed symmetric and antisymmetric N-solitons into symmetric and asymmetric quasi-solitons are found. In the PT-symmetric system, with the balanced gain and loss acting in the two cores, borders of the stability against the blowup are identified. Notably, in all the cases the stability regions are larger for antisymmetric 2-soliton inputs than for their symmetric counterparts, on the contrary to previously known results for fundamental solitons (N=1). Dynamical regimes (switching) are also studied for the 2-soliton injected into a single core of the coupler. In particular, a region of splitting of the input into a pair of symmetric solitons is found, which is explained as a manifestation of the resonance between the vibrations of the 2-soliton and oscillations of energy between the two cores in the coupler.
Nonlinear modal interactions in parity-time (${\\cal PT}$) symmetric lasers
Ge, Li
2016-01-01
Parity-time ($\\cal PT$) symmetric lasers have attracted considerable attention lately due to their promising applications and intriguing properties, such as free spectral range doubling and single-mode lasing. In this work we discuss nonlinear modal interactions in these laser systems under steady state conditions, and we demonstrate that several gain clamping scenarios can occur for lasing operation in the $\\cal PT$-symmetric and $\\cal PT$-broken phases. In particular, we show that, depending on the system's design and the external pump profile, its operation in the nonlinear regime falls into two different categories: in one the system is frozen in the $\\cal PT$ phase space as the applied gain increases, while in the other the system is pulled towards its exceptional point. These features are first illustrated by a coupled mode formalism and later verified by employing the Steady-state Ab-initio Laser Theory (SALT). Our findings shine light on the robustness of single-mode operation in these lasers against ...
Ge, Li
2016-01-01
The scattering matrix $S$ obeys the unitary relation $S^\\dagger S=1$ in a Hermitian system and the symmetry property ${\\cal PT}S{\\cal PT}=S^{-1}$ in a Parity-Time (${\\cal PT}$) symmetric system. Here we report a different symmetry relation of the $S$ matrix in a one-dimensional heterostructure, which is given by the amplitude ratio of the incident waves in the scattering eigenstates. It originates from the optical reciprocity and holds independent of the Hermiticity or $\\cal PT$ symmetry of the system. Using this symmetry relation, we probe a quasi-transition that is reminiscent of the spontaneous symmetry breaking of a $\\cal PT$-symmetric $S$ matrix, now with unbalanced gain and loss and even in the absence of gain. We show that the additional symmetry relation provides a clear evidence of an exceptional point, even when all other signatures of the $\\cal PT$ symmetry breaking are completely erased. We also discuss the existence of a final exceptional point in this correspondence, which is attributed to asymm...
Non-Hermitian ${\\cal PT}$-symmetric relativistic quantum theory in an intensive magnetic field
Rodionov, V N
2016-01-01
We develop relativistic non-Hermitian quantum theory and its application to neutrino physics in a strong magnetic field. It is well known, that one of the fundamental postulates of quantum theory is the requirement of Hermiticity of physical parameters. This condition not only guarantees the reality of the eigenvalues of Hamiltonian operators, but also implies the preservation of the probabilities of the considered quantum processes. However as it was shown relatively recently (Bender, Boettcher 1998), Hermiticity is a sufficient but it is not a necessary condition. It turned out that among non-Hermitian Hamiltonians it is possible to allocate a number of such which have real energy spectra and can ensure the development of systems over time with preserving unitarity. This type of Hamiltonians includes so-called parity-time (${\\cal PT}$) symmetric models which is already used in various fields of modern physics. The most developed in this respect are models, which used in the field of ${\\cal PT}$-symmetric op...
A possible method for non-Hermitian and Non-PT-symmetric Hamiltonian systems.
Li, Jun-Qing; Miao, Yan-Gang; Xue, Zhao
2014-01-01
A possible method to investigate non-Hermitian Hamiltonians is suggested through finding a Hermitian operator η+ and defining the annihilation and creation operators to be η+ -pseudo-Hermitian adjoint to each other. The operator η+ represents the η+ -pseudo-Hermiticity of Hamiltonians. As an example, a non-Hermitian and non-PT-symmetric Hamiltonian with imaginary linear coordinate and linear momentum terms is constructed and analyzed in detail. The operator η+ is found, based on which, a real spectrum and a positive-definite inner product, together with the probability explanation of wave functions, the orthogonality of eigenstates, and the unitarity of time evolution, are obtained for the non-Hermitian and non-PT-symmetric Hamiltonian. Moreover, this Hamiltonian turns out to be coupled when it is extended to the canonical noncommutative space with noncommutative spatial coordinate operators and noncommutative momentum operators as well. Our method is applicable to the coupled Hamiltonian. Then the first and second order noncommutative corrections of energy levels are calculated, and in particular the reality of energy spectra, the positive-definiteness of inner products, and the related properties (the probability explanation of wave functions, the orthogonality of eigenstates, and the unitarity of time evolution) are found not to be altered by the noncommutativity.
A possible method for non-Hermitian and Non-PT-symmetric Hamiltonian systems.
Directory of Open Access Journals (Sweden)
Jun-Qing Li
Full Text Available A possible method to investigate non-Hermitian Hamiltonians is suggested through finding a Hermitian operator η+ and defining the annihilation and creation operators to be η+ -pseudo-Hermitian adjoint to each other. The operator η+ represents the η+ -pseudo-Hermiticity of Hamiltonians. As an example, a non-Hermitian and non-PT-symmetric Hamiltonian with imaginary linear coordinate and linear momentum terms is constructed and analyzed in detail. The operator η+ is found, based on which, a real spectrum and a positive-definite inner product, together with the probability explanation of wave functions, the orthogonality of eigenstates, and the unitarity of time evolution, are obtained for the non-Hermitian and non-PT-symmetric Hamiltonian. Moreover, this Hamiltonian turns out to be coupled when it is extended to the canonical noncommutative space with noncommutative spatial coordinate operators and noncommutative momentum operators as well. Our method is applicable to the coupled Hamiltonian. Then the first and second order noncommutative corrections of energy levels are calculated, and in particular the reality of energy spectra, the positive-definiteness of inner products, and the related properties (the probability explanation of wave functions, the orthogonality of eigenstates, and the unitarity of time evolution are found not to be altered by the noncommutativity.
Mostafazadeh, Ali
2016-01-01
Among the interesting outcomes of the study of the physical applications of spectral singularities in PT-symmetric optical systems is the discovery of CPA-lasers. These are devices that act both as a threshold laser and a coherent perfect absorber (CPA) for the same values of their physical parameters. Unlike a homogeneous slab that is made to act as a CPA, a slab CPA-laser would absorb the incident waves coming from the left and right of the device provided that they have appropriate intensity and phase contrasts. We provide a comprehensive study of one of the simplest experimentally accessible examples of a CPA-laser, namely a PT-symmetric optical slab system consisting of a balanced pair of adjacent or separated gain and loss components. In particular, we give a closed form expression describing the spectral singularities of the system which correspond to its CPA-laser configurations. We determine the intensity and phase contrasts for the TE and TM waves that are emitted (absorbed) whenever the slab acts a...
Longhi, Stefano
2016-01-01
We consider wave transport phenomena in a $\\mathcal{PT}$-symmetric extension of the periodically-kicked quantum rotator model and reveal that dynamical localization assists the unbroken $\\mathcal{PT}$ phase. In the delocalized (quantum resonance) regime, $\\mathcal{PT}$ symmetry is always in the broken phase and ratchet acceleration arises as a signature of unidirectional non-Hermitian transport. An optical implementation of the periodically-kicked $\\mathcal{PT}$-symmetric Hamiltonian, based on transverse beam propagation in a passive optical resonator with combined phase and loss gratings, is suggested to visualize acceleration modes in fractional Talbot cavities.
Non-reciprocal mu-near-zero mode in PT-symmetric magnetic domains
Wang, Jin; Ling, Chi Wai; Chan, C T; Fung, Kin Hung
2014-01-01
We find that a new type of non-reciprocal modes exist at an interface between two \\emph{parity-time} ($\\mathcal{PT}$) symmetric magnetic domains (MDs) near the frequency of zero effective permeability. The new mode is non-propagating and purely magnetic when the two MDs are semi-infinite while it becomes propagating in the finite case. In particular, two pronounced nonreciprocal responses could be observed via the excitation of this mode: one-way optical tunneling for oblique incidence and unidirectional beam shift at normal incidence. When the two MDs system becomes finite in size, it is found that perfect-transmission mode could be achieved if $\\mathcal{PT}$-symmetry is maintained. The unique properties of such an unusual mode are investigated by analytical modal calculation as well as numerical simulations. The results suggest a new approach to the design of compact optical isolator.
Nonreciprocal μ -near-zero mode in PT -symmetric magnetic domains
Wang, Jin; Dong, Hui Yuan; Ling, Chi Wai; Chan, C. T.; Fung, Kin Hung
2015-06-01
We find that a new type of nonreciprocal modes exists at an interface between two parity-time- (PT -) symmetric magnetic domains (MDs) near the frequency of zero effective permeability. This mode is nonpropagating and purely magnetic when the two MDs are semi-infinite, while it becomes propagating in the finite case. In particular, two pronounced nonreciprocal responses could be observed via the excitation of this mode: one-way optical tunneling for oblique incidence and unidirectional beam shift at normal incidence. When the two MDs system becomes finite in size, it is found that perfect-transmission mode could be achieved if PT symmetry is maintained. The unique properties of such an unusual mode are investigated by analytical modal calculation as well as numerical simulations. The results suggest a different approach to the design of compact optical isolator.
PT-symmetric coupler with a coupling defect: soliton interaction with exceptional point
Bludov, Yuli V; Huang, Guoxiang; Konotop, Vladimir V
2014-01-01
We study interaction of a soliton in a parity-time (PT) symmetric coupler which has local perturbation of the coupling constant. Such a defect does not change the PT-symmetry of the system, but locally can achieve the exceptional point. We found that the symmetric solitons after interaction with the defect either transform into breathers or blow up. The dynamics of anti-symmetric solitons is more complex, showing domains of successive broadening of the beam and of the beam splitting in two outwards propagating solitons, in addition to the single breather generation and blow up. All the effects are preserved when the coupling strength in the center of the defect deviates from the exceptional point. If the coupling is strong enough the only observable outcome of the soliton-defect interaction is the generation of the breather.
PT-symmetric microring lasers: Self-adapting broadband mode-selective resonators
Hodaei, Hossein; Heinrich, Matthias; Christodoulides, Demetrios N; Khajavikhan, Mercedeh
2014-01-01
We demonstrate experimentally that stable single longitudinal mode operation can be readily achieved in PT-symmetric arrangements of coupled microring resonators. Whereas any active resonator is in principle capable of displaying single-wavelength operation, selective breaking of PT-symmetry can be utilized to systematically enhance the maximum achievable gain of this mode, even if a large number of competing longitudinal or transverse resonator modes fall within the amplification bandwidth of the inhomogeneously broadened active medium. This concept is robust with respect to fabrication tolerances, and its mode selectivity is established without the need for additional components or specifically designed filters. Our results may pave the way for a new generation of versatile cavities lasing at a desired longitudinal resonance. Along these lines, traditionally highly multi-moded microring resonator configurations can be fashioned to suppress all but one longitudinal mode.
Mostafazadeh, Ali; Sarısaman, Mustafa
2016-12-01
Among the interesting outcomes of the study of the physical applications of spectral singularities in PT-symmetric optical systems is the discovery of CPA-lasers. These are devices that act both as a threshold laser and a coherent perfect absorber (CPA) for the same values of their physical parameters. Unlike a homogeneous slab that is made to act as a CPA, a slab CPA-laser would absorb the incident waves coming from the left and right of the device provided that they have appropriate intensity and phase contrasts. We provide a comprehensive study of one of the simplest experimentally accessible examples of a CPA-laser, namely a PT-symmetric optical slab system consisting of a balanced pair of adjacent or separated gain and loss components. In particular, we give a closed form expression describing the spectral singularities of the system which correspond to its CPA-laser configurations. We determine the intensity and phase contrasts for the TE and TM waves that are emitted (absorbed) whenever the slab acts as a laser (CPA). We also investigate the behavior of the time-averaged energy density and Poynting vector for these waves. This is necessary for determining the optimal values of the physical parameters of the system that make it act as a CPA-laser. These turn out to correspond to situations where the separation distance s between the gain and loss layers is an odd multiple of a characteristic length scale s0. A curious by-product of our study is that, except for the cases where s is an even integer multiple of s0, there is a critical angle of polarization beyond which the energy of the waves emitted from the lossy layer can be larger than the energy of those emitted from the gain layer.
Generation of families of spectra in PT-symmetric quantum mechanics and scalar bosonic field theory.
Schmidt, Steffen; Klevansky, S P
2013-04-28
This paper explains the systematics of the generation of families of spectra for the -symmetric quantum-mechanical Hamiltonians H=p(2)+x(2)(ix)(ε), H=p(2)+(x(2))(δ) and H=p(2)-(x(2))(μ). In addition, it contrasts the results obtained with those found for a bosonic scalar field theory, in particular in one dimension, highlighting the similarities to and differences from the quantum-mechanical case. It is shown that the number of families of spectra can be deduced from the number of non-contiguous pairs of Stokes wedges that display PT symmetry. To do so, simple arguments that use the Wentzel-Kramers-Brillouin approximation are used, and these imply that the eigenvalues are real. However, definitive results are in most cases presently only obtainable numerically, and not all eigenvalues in each family may be real. Within the approximations used, it is illustrated that the difference between the quantum-mechanical and the field-theoretical cases lies in the number of accessible regions in which the eigenfunctions decay exponentially. This paper reviews and implements well-known techniques in complex analysis and PT-symmetric quantum theory.
Directory of Open Access Journals (Sweden)
Smarandache F.
2010-04-01
Full Text Available In this article, we find out some analytical and numerical solutions to the problem of barrier tunneling for cluster deuterium, in particular using Langevin method to solve the time-independent Schroedinger equation.
Rodionov, V N
2013-01-01
The modified Dirac equations for the massive particles with the replacement of the physical mass $m$ with the help of the relation $m\\rightarrow m_1+ \\gamma_5 m_2$ are investigated. It is shown that for a fermion theory with a $\\gamma_5$-mass term, the limiting of the mass specter by the value $ m_{max}= {m_1}^2/2m_2$ takes place. In this case the different regions of the unbroken $\\cal PT$ symmetry may be expressed by means of the restriction of the physical mass $m\\leq m_{max}$. It should be noted that in the approach which was developed by C.Bender et al. for the $\\cal PT$-symmetric version of the massive Thirring model with $\\gamma_5$-mass term, the region of the unbroken $\\cal PT$-symmetry was found in the form $m_1\\geq m_2$ \\cite{ft12}. However on the basis of the mass limitation $m\\leq m_{max}$ we obtain that the domain $m_1\\geq m_2$ consists of two different parametric sectors: i) $0\\leq m_2 \\leq m_1/\\sqrt{2}$ -this values of mass parameters $m_1,m_2$ correspond to the traditional particles for which ...
One- and two-dimensional solitons in PT-symmetric systems emulating the spin-orbit coupling
Sakaguchi, Hidetsugu
2016-01-01
We introduce a two-dimensional (2D) system, which can be implemented in dual-core planar optical couplers with the Kerr nonlinearity in its cores, making it possible to blend effects of the PT symmetry, represented by the balanced linear gain and loss in the two cores, and spin-orbit coupling (SOC), emulated by a spatially biased coupling between the cores. Families of 1D and 2D solitons and their stability boundaries are identified. In the 1D setting, the addition of the SOC terms leads, at first, to shrinkage of the stability area for PT-symmetric solitons, which is followed by its rapid expansion. 2D solitons have their stability region too, in spite of the simultaneous action of two major destabilizing factors, viz., the collapse driven by the Kerr nonlinearity, and a trend towards spontaneous breakup of the gain-loss balance. In the limit of the SOC terms dominating over the intrinsic diffraction, the 1D system gives rise to a new model for gap solitons, which admits exact analytical solutions.
Stabilizing and destabilizing perturbations of PT-symmetric indefinitely damped systems.
Kirillov, O N
2013-04-28
Eigenvalues of a potential dynamical system with damping forces that are described by an indefinite real symmetric matrix can behave as those of a Hamiltonian system when gain and loss are in a perfect balance. This happens when the indefinitely damped system obeys parity-time ( ) symmetry. How do pure imaginary eigenvalues of a stable -symmetric indefinitely damped system behave when variation in the damping and potential forces destroys the symmetry? We establish that it is essentially the tangent cone to the stability domain at the exceptional point corresponding to the Whitney umbrella singularity on the stability boundary that manages transfer of instability between modes.
Observation of Bloch oscillations in complex PT-symmetric photonic lattices
Wimmer, Martin; Christodoulides, Demetrios; Peschel, Ulf
2016-01-01
Light propagation in periodic environments is often associated with a number of interesting and potentially useful processes. If a crystalline optical potential is also linearly ramped, light can undergo periodic Bloch oscillations, a direct outcome of localized Wannier-Stark states and their equidistant eigenvalue spectrum. Even though these effects have been extensively explored in conservative settings, this is by no means the case in non-Hermitian photonic lattices encompassing both amplification and attenuation. Quite recently, Bloch oscillations have been predicted in parity-time-symmetric structures involving gain and loss in a balanced fashion. While in a complex bulk medium, one intuitively expects that light will typically follow the path of highest amplification, in a periodic system this behavior can be substantially altered by the underlying band structure. Here, we report the first experimental observation of Bloch oscillations in parity-time-symmetric mesh lattices. We show that these revivals ...
Observation of Bloch oscillations in complex PT-symmetric photonic lattices.
Wimmer, Martin; Miri, Mohammed-Ali; Christodoulides, Demetrios; Peschel, Ulf
2015-12-07
Light propagation in periodic environments is often associated with a number of interesting and potentially useful processes. If a crystalline optical potential is also linearly ramped, light can undergo periodic Bloch oscillations, a direct outcome of localized Wannier-Stark states and their equidistant eigenvalue spectrum. Even though these effects have been extensively explored in conservative settings, this is by no means the case in non-Hermitian photonic lattices encompassing both amplification and attenuation. Quite recently, Bloch oscillations have been predicted in parity-time-symmetric structures involving gain and loss in a balanced fashion. While in a complex bulk medium, one intuitively expects that light will typically follow the path of highest amplification, in a periodic system this behavior can be substantially altered by the underlying band structure. Here, we report the first experimental observation of Bloch oscillations in parity-time-symmetric mesh lattices. We show that these revivals exhibit unusual properties like secondary emissions and resonant restoration of PT symmetry. In addition, we present a versatile method for reconstructing the real and imaginary components of the band structure by directly monitoring the light evolution during a cycle of these oscillations.
Asymmetric soliton mobility in competing linear-nonlinear PT-symmetric lattices
Kartashov, Yaroslav V; Torner, Lluis
2016-01-01
We address the transverse mobility of spatial solitons in competing parity-time-symmetric linear and nonlinear lattices. The competition between out-of-phase linear and nonlinear lattices results in a drastic mobility enhancement within a range of soliton energies. We show that within such range, the addition of even a small imaginary part in the linear potential makes soliton mobility strongly asymmetric. The minimal phase tilt required for setting solitons into radiationless motion across the lattice in the direction opposite to that of the internal current drops to nearly zero, while the minimal phase tilt required for motion in the opposite direction notably increases. For a given initial phase tilt, the velocity of soliton motion grows with an increase of the balanced gain/losses. In this regime of enhanced mobility, tilted solitons can efficiently drag other solitons that were initially at rest, to form moving soliton pairs.
Nguyen, Ba Phi
2016-01-01
We study numerically the transport and localization properties of waves in ordered and disordered ladder-shaped lattices with local $\\mathcal{PT}$ symmetry. Using a transfer matrix method, we calculate the transmittance and the reflectance for the individual channels and the Lyapunov exponent for the whole system. In the absence of disorder, we find that when the gain/loss parameter $\\rho$ is smaller than the interchain coupling parameter $t_{v}$, the transmittance and the reflectance are periodic functions of the system size, whereas when $\\rho$ is larger than $t_{v}$, the transmittance is found to be an exponentially-decaying function while the reflectance attains a saturation value in the thermodynamic limit. For a fixed system size, there appear perfect transmission resonances in each individual channel at several values of the gain/loss strength smaller than $t_{v}$. A singular behavior of the transmittance is also found to appear at various values of $\\rho$ for a given system size. When disorder is inse...
Pigmy resonances, transfer, and separable potentials
Bertulani, C A; Kruppa, A; Hao, T V Nhan; Mukhamedzhanov, A M; Shubhchintak,
2016-01-01
In this contribution we make a short review of recent progress on topics of current interest in nuclear physics and nuclear astrophysics. In particular, we discuss a re-analysis of the extraction of the dipole response of the pigmy resonance in $^{68}$Ni based on a continuum discretized coupled-channels calculation in relativistic Coulomb excitation experiments. We also discuss the forthcoming progresses made by our group on the Alt-Sandhas-Grassberber approach to (d,p) reactions and future expectations. The role of separable potentials in solving such equations with a test case based on applications of such potentials to phase-shift analysis is also presented.
Separable Dual Space Gaussian Pseudo-potentials
Gödecker, S; Hutter, J
1995-01-01
We present pseudo-potential coefficients for the first two rows of the periodic table. The pseudo potential is of a novel analytic form, that gives optimal efficiency in numerical calculations using plane waves as basis set. At most 7 coefficients are necessary to specify its analytic form. It is separable and has optimal decay properties in both real and Fourier space. Because of this property, the application of the nonlocal part of the pseudo-potential to a wave-function can be done in an efficient way on a grid in real space. Real space integration is much faster for large systems than ordinary multiplication in Fourier space since it shows only quadratic scaling with respect to the size of the system. We systematically verify the high accuracy of these pseudo-potentials by extensive atomic and molecular test calculations.
Exact Solutions of Klein-Gordon Equation with Scalar and Vector Rosen-Morse-Type Poten-tials
Institute of Scientific and Technical Information of China (English)
A. Soylu; O. Bayrak; I. Boztosun
2008-01-01
@@ We obtain an exact analytical solution of the Klein-Gordon equation for the equal vector and scalar Rosen-Morse and Eckart potentials as well as the parity-time (PT) symmetric version of the these potentials by using the asymptotic iteration method. Although these PT symmetric potentials are non-Hermitian, the corresponding eigenvalues are real as a result of the PT symmetry.
Directory of Open Access Journals (Sweden)
Daniel Haag
2014-04-01
Full Text Available We consider the linear and nonlinear Schrödinger equation for a Bose-Einstein condensate in a harmonic trap with PT-symmetric double-delta function loss and gain terms. We verify that the conditions for the applicability of a recent proposition by Mityagin and Siegl on singular perturbations of harmonic oscillator type self-adjoint operators are fulfilled. In both the linear and nonlinear case we calculate numerically the shifts of the unperturbed levels with quantum numbers n of up to 89 in dependence on the strength of the non-Hermiticity and compare with rigorous estimates derived by those authors. We confirm that the predicted 1/n1/2 estimate provides a valid upper bound on the shrink rate of the numerical eigenvalues. Moreover, we find that a more recent estimate of log(n/n3/2 is in excellent agreement with the numerical results. With nonlinearity the shrink rates are found to be smaller than without nonlinearity, and the rigorous estimates, derived only for the linear case, are no longer applicable.
Znojil, Miloslav
2017-07-01
The phenomenon of the birth of an isolated quantum bound state at the lower edge of the continuum is studied for a particle moving along a discrete real line of coordinates x ∈Z . The motion is controlled by a weakly nonlocal 2 J -parametric external potential V which is non-Hermitian but P T symmetric. The model is found exactly solvable. The bound states are interpreted as Sturmians. Their closed-form definitions are presented and discussed up to J =7 .
Separation of Potentials in the Two-Body Problem
Vasilyev, Andrey
2012-01-01
In contrast to the well-known solution of the two-body problem through the use of the concept of reduced mass, a solution is proposed involving separation of potentials. It is shown that each of the two point bodies moves in its own stationary potential well generated by the other body, and the magnitudes of these potentials are calculated. It is shown also that for each body separately the energy and the angular momentum laws are valid. The knowledge of the potentials in which the bodies are moving permits calculation of the trajectories of each body without resorting to the reduced mass. Key words: mechanics, two-body problem, gravitational potential, virial theorem.
Directory of Open Access Journals (Sweden)
Christianto V.
2010-07-01
Full Text Available In this article, we find out some analytical and numerical solutions to the problem of barrier tunneling for cluster deuterium, in particular using Langevin method to solve the time-independent Schrödinger equation.
Separable representation of energy-dependent optical potentials
Hlophe, L.; Elster, Ch.
2016-03-01
Background: One important ingredient for many applications of nuclear physics to astrophysics, nuclear energy, and stockpile stewardship are cross sections for reactions of neutrons with rare isotopes. Since direct measurements are often not feasible, indirect methods, e.g., (d ,p ) reactions, should be used. Those (d ,p ) reactions may be viewed as three-body reactions and described with Faddeev techniques. Purpose: Faddeev equations in momentum space have a long tradition of utilizing separable interactions in order to arrive at sets of coupled integral equations in one variable. Optical potentials representing the effective interactions in the neutron (proton) nucleus subsystem are usually non-Hermitian as well as energy dependent. Potential matrix elements as well as transition matrix elements calculated with them must fulfill the reciprocity theorem. The purpose of this paper is to introduce a separable, energy-dependent representation of complex, energy-dependent optical potentials that fulfill reciprocity exactly. Methods: Momentum space Lippmann-Schwinger integral equations are solved with standard techniques to obtain the form factors for the separable representation. Results: Starting from a separable, energy-independent representation of global optical potentials based on a generalization of the Ernst-Shakin-Thaler (EST) scheme, a further generalization is needed to take into account the energy dependence. Applications to n +48Ca ,n +208Pb , and p +208Pb are investigated for energies from 0 to 50 MeV with special emphasis on fulfilling reciprocity. Conclusions: We find that the energy-dependent separable representation of complex, energy-dependent phenomenological optical potentials fulfills reciprocity exactly. In addition, taking into account the explicit energy dependence slightly improves the description of the S matrix elements.
Complexification of three potential models – II
Indian Academy of Sciences (India)
Sanjib Meyur; S Dednath
2009-10-01
A new kind of $\\mathcal{PT}$ and non-$\\mathcal{PT}$-symmetric complex potentials are constructed from a group theoretical viewpoint of the sl(2, ) potential algebras. The real eigenvalues and the corresponding regular eigenfunctions are also obtained. The results are compared with the ones obtained before.
Separable Representation of Energy-Dependent Optical Potentials
Hlophe, Linda
2015-01-01
Background. One important ingredient for many applications of nuclear physics to astrophysics, nuclear energy, and stockpile stewardship are cross sections for reactions of neutrons with rare isotopes. Since direct measurements are often not feasible, indirect methods, e.g. (d,p) reactions, should be used. Those (d,p) reactions may be viewed as three-body reactions and described with Faddeev techniques. Purpose. Faddeev equations in momentum space have a long tradition of utilizing separable interactions in order to arrive at sets of coupled integral equations in one variable. Optical potentials representing the effective interactions in the neutron (proton) nucleus subsystem are usually non-Hermitian as well as energy-dependent. Potential matrix elements as well as transition matrix elements calculated with them must fulfill the reciprocity theorem. The purpose of this paper is to introduce a separable, energy-dependent representation of complex, energy-dependent optical potentials that fulfill reciprocity e...
Separable Representation of Multichannel Nucleon-Nucleus Optical Potentials
Hlophe, Linda
2016-01-01
One important ingredient for many applications of nuclear physics to astrophysics, nuclear energy, and stockpile stewardship are cross sections for reactions of neutrons with rare isotopes. Since direct measurements are often not feasible, indirect methods, e.g. (d,p) reactions, should be used. Those (d,p) reactions may be viewed as three-body reactions and described with Faddeev techniques. Faddeev equations in momentum space have a long tradition of utilizing separable interactions in order to arrive at sets of coupled integral equations in one variable. Optical potentials representing the effective interactions in the neutron (proton) nucleus subsystem are usually non-Hermitian as well as energy-dependent. Including excitations of the nucleus in the calculation requires a multichannel optical potential. The purpose of this paper is to introduce a separable, energy-dependent multichannel representation of complex, energy-dependent optical potentials that contain excitations of the nucleus and that fulfill r...
Separable Multichannel Momentum Space Potentials for Nuclear Reactions
Hlophe, Linda; Elster, Charlotte
2016-09-01
Many nuclei are deformed and their properties can be described using a rotational model. This involves defining a deformed surface of the nucleus and constructing the nucleon-nucleus interaction as a function of distance to the surface. Such a potential has non-zero matrix elements between different nuclear rotational states which are characterized by the spin-parity Iπ, leading to channel couplings. For specific reaction calculations, it is advantageous to have separable representations of the interaction matrix elements available. We develop separable representations following a scheme suggested by Ernst, Shakin, and Thaler (EST). Since optical potentials are complex and energy-dependent, the multichannel EST scheme is generalized to complex, energy-dependent separable potentials. In the case of proton-nucleus interactions the EST scheme is further extended to include charged particles. The multichannel EST scheme is applied to nucleon scattering off 12C, where the first two excited states (Iπ =2+ ,4+) are taken into account. Research for this project was supported in part by the US Department of Energy, Office of Science of Nuclear Physics under Contract No. DE-FG02-93ER40756.
Potential Applications of Zeolite Membranes in Reaction Coupling Separation Processes
Directory of Open Access Journals (Sweden)
Tunde V. Ojumu
2012-10-01
Full Text Available Future production of chemicals (e.g., fine and specialty chemicals in industry is faced with the challenge of limited material and energy resources. However, process intensification might play a significant role in alleviating this problem. A vision of process intensification through multifunctional reactors has stimulated research on membrane-based reactive separation processes, in which membrane separation and catalytic reaction occur simultaneously in one unit. These processes are rather attractive applications because they are potentially compact, less capital intensive, and have lower processing costs than traditional processes. Therefore this review discusses the progress and potential applications that have occurred in the field of zeolite membrane reactors during the last few years. The aim of this article is to update researchers in the field of process intensification and also provoke their thoughts on further research efforts to explore and exploit the potential applications of zeolite membrane reactors in industry. Further evaluation of this technology for industrial acceptability is essential in this regard. Therefore, studies such as techno-economical feasibility, optimization and scale-up are of the utmost importance.
Potential Applications of Zeolite Membranes in Reaction Coupling Separation Processes
Daramola, Michael O.; Aransiola, Elizabeth F.; Ojumu, Tunde V.
2012-01-01
Future production of chemicals (e.g., fine and specialty chemicals) in industry is faced with the challenge of limited material and energy resources. However, process intensification might play a significant role in alleviating this problem. A vision of process intensification through multifunctional reactors has stimulated research on membrane-based reactive separation processes, in which membrane separation and catalytic reaction occur simultaneously in one unit. These processes are rather attractive applications because they are potentially compact, less capital intensive, and have lower processing costs than traditional processes. Therefore this review discusses the progress and potential applications that have occurred in the field of zeolite membrane reactors during the last few years. The aim of this article is to update researchers in the field of process intensification and also provoke their thoughts on further research efforts to explore and exploit the potential applications of zeolite membrane reactors in industry. Further evaluation of this technology for industrial acceptability is essential in this regard. Therefore, studies such as techno-economical feasibility, optimization and scale-up are of the utmost importance.
Separable Representation of Proton-Nucleus Optical Potentials
Hlophe, L; Elster, Ch; Nunes, F M; Arbanas, G; Escher, J E; Thompson, I J
2014-01-01
Recently, a new approach for solving the three-body problem for (d,p) reactions in the Coulomb-distorted basis in momentum space was proposed. Important input quantities for such calculations are the scattering matrix elements for proton- and neutron-nucleus scattering. We present a generalization of the Ernst-Shakin-Thaler scheme in which a momentum space separable representation of proton-nucleus scattering matrix elements can be calculated in the Coulomb basis. The viability of this method is demonstrated by comparing S-matrix elements obtained for p$+^{48}$Ca and p$+^{208}$Pb for a phenomenological optical potential with corresponding coordinate space calculations.
Polymeric membrane systems of potential use for battery separators
Philipp, W. H.
1977-01-01
Two membrane systems were investigated that may have potential use as alkaline battery separators. One system comprises two miscible polymers: a support polymer (e.g., polyvinyl formal) and an ion conductor such as polyacrylic acid. The other system involves a film composed of two immiscible polymers: a conducting polymer (e.g., calcium polyacrylate) suspended in an inert polymer support matrix, polyphenylene oxide. Resistivities in 45-percent potassium hydroxide and qualitative mechanical properties are presented for films comprising various proportions of conducting and support polymers. In terms of these parameters, the results are encouraging for optimum ratios of conducting to support polymers.
Nonlocal separable potential in the one-dimensional Dirac equation
Energy Technology Data Exchange (ETDEWEB)
Calkin, M.G.; Kiang, D.; Nogami, Y.
1988-08-01
The one-dimensional Dirac equation is solved for a separable potential of the form of Lorentz scalar plus vector, (..beta..g+h)v(x)v(x'). Exact analytic solutions are obtained for bound and scattering states for arbitrary v(x). For a particular combination of the values of g and h, degeneracy of the bound state occurs, and total reflection also takes place for a certain incident energy. The limiting case, in which v(x) becomes a delta function, is discussed in detail.
Separable Potentials for (d,p) Reaction Calculations
Elster, Ch; Eremenko, V; Nunes, F M; Thompson, I J; Arbanas, G; Escher, J E
2015-01-01
An important ingredient for applications of nuclear physics to e.g. astrophysics or nuclear energy are the cross sections for reactions of neutrons with rare isotopes. Since direct measurements are often not possible, indirect methods like $(d,p)$ reactions must be used instead. Those $(d,p)$ reactions may be viewed as effective three-body reactions and described with Faddeev techniques. An additional challenge posed by $(d,p)$ reactions involving heavier nuclei is the treatment of the Coulomb force. To avoid numerical complications in dealing with the screening of the Coulomb force, recently a new approach using the Coulomb distorted basis in momentum space was suggested. In order to implement this suggestion, one needs to derive a separable representation of neutron- and proton-nucleus optical potentials and compute their matrix elements in this basis.
Separable Optical Potentials for (d,p) Reactions
Elster, Ch; Eremenko, V; Nunes, F M; Arbanas, G; Escher, J E; Thompson, I J
2014-01-01
An important ingredient for applications of nuclear physics to e.g. astrophysics or nuclear energy are the cross sections for reactions of neutrons with rare isotopes. Since direct measurements are often not possible, indirect methods like (d,p) reactions must be used instead. Those (d,p) reactions may be viewed as effective three-body reactions and described with Faddeev techniques. An additional challenge posed by (d,p) reactions involving heavier nuclei is the treatment of the Coulomb force. To avoid numerical complications in dealing with the screening of the Coulomb force, recently a new approach using the Coulomb distorted basis in momentum space was suggested. In order to implement this suggestion, one needs not only to derive a separable representation of neutron- and proton-nucleus optical potentials, but also compute the Coulomb distorted form factors in this basis.
Yang, Jianke
2016-01-01
Stability of soliton families in one-dimensional nonlinear Schroedinger equations with non-parity-time (PT)-symmetric complex potentials is investigated numerically. It is shown that these solitons can be linearly stable in a wide range of parameter values both below and above phase transition. In addition, a pseudo-Hamiltonian-Hopf bifurcation is revealed, where pairs of purely-imaginary eigenvalues in the linear-stability spectra of solitons collide and bifurcate off the imaginary axis, creating oscillatory instability, which resembles Hamiltonian-Hopf bifurcations of solitons in Hamiltonian systems even though the present system is dissipative and non-Hamiltonian. The most important numerical finding is that, eigenvalues of linear-stability operators of these solitons appear in quartets $(\\lambda, -\\lambda, \\lambda^*, -\\lambda^*)$, similar to conservative systems and PT-symmetric systems. This quartet eigenvalue symmetry is very surprising for non-PT-symmetric systems, and it has far-reaching consequences ...
Wheat aleurone: separation, composition, health aspects, and potential food use.
Brouns, Fred; Hemery, Youna; Price, Ruth; Anson, Nuria Mateo
2012-01-01
Over the last three decades substantial attention has been given to the role of dietary fiber in health and disease, in particular diabetes, cardiovascular disease, intestinal health, and some types of cancer. As a result the food industry started to add back fiber to refined foods and develop fiber rich foods. Scientists suggested that whole grain foods are superior to foods enriched with fibers obtained/synthesized using enzyme treatment, and thermal or chemical processing because the content of bioactive components and micronutrients in whole grain is more abundant. This triggered interest in how to isolate the micronutrient rich aleurone fiber fraction from wheat. Aleurone is a single cell layer at the inner site of the bran. It contains most of the minerals, vitamins, phenolic antioxidants, and lignans of the wheat grain. Novel milling and dry-fractionation techniques have recently allowed for full-scale separation of aleurone cells from the other layers of wheat bran, yielding a fiber rich concentrate which potentially contains many of the "whole grain kernel bioactives," which recently have been used in a variety of studies. The present review highlights available data on aleurone isolation, composition, intestinal physiology, and its metabolism and potential health benefits as well as its use in food.
Chen, Yong; Yan, Zhenya; Mihalache, Dumitru; Malomed, Boris A
2017-04-28
Since the parity-time-([Formula: see text]-) symmetric quantum mechanics was put forward, fundamental properties of some linear and nonlinear models with [Formula: see text]-symmetric potentials have been investigated. However, previous studies of [Formula: see text]-symmetric waves were limited to constant diffraction coefficients in the ambient medium. Here we address effects of variable diffraction coefficient on the beam dynamics in nonlinear media with generalized [Formula: see text]-symmetric Scarf-II potentials. The broken linear [Formula: see text] symmetry phase may enjoy a restoration with the growing diffraction parameter. Continuous families of one- and two-dimensional solitons are found to be stable. Particularly, some stable solitons are analytically found. The existence range and propagation dynamics of the solitons are identified. Transformation of the solitons by means of adiabatically varying parameters, and collisions between solitons are studied too. We also explore the evolution of constant-intensity waves in a model combining the variable diffraction coefficient and complex potentials with globally balanced gain and loss, which are more general than [Formula: see text]-symmetric ones, but feature similar properties. Our results may suggest new experiments for [Formula: see text]-symmetric nonlinear waves in nonlinear nonuniform optical media.
PT-Symmetric Quantum Electrodynamics and Unitarity
Milton, Kimball A; Parashar, Prachi; Pourtolami, Nima; Wagner, J
2012-01-01
More than 15 years ago, a new approach to quantum mechanics was suggested, in which Hermiticity of the Hamiltonian was to be replaced by invariance under a discrete symmetry, the product of parity and time-reversal symmetry, $\\mathcal{PT}$. It was shown that if $\\mathcal{PT}$ is unbroken, energies were, in fact, positive, and unitarity was satisifed. Since quantum mechanics is quantum field theory in 1 dimension, time, it was natural to extend this idea to higher-dimensional field theory, and in fact an apparently viable version of $\\mathcal{PT}$-invariant quantum electrodynamics was proposed. However, it has proved difficult to establish that the unitarity of the scattering matrix, for example, the K\\"all\\'en spectral representation for the photon propagator, can be maintained in this theory. This has led to questions of whether, in fact, even quantum mechanical systems are consistent with probability conservation when Green's functions are examined, since the latter have to possess physical requirements of ...
PT-symmetric quantum electrodynamics and unitarity.
Milton, Kimball A; Abalo, E K; Parashar, Prachi; Pourtolami, Nima; Wagner, J
2013-04-28
More than 15 years ago, a new approach to quantum mechanics was suggested, in which Hermiticity of the Hamiltonian was to be replaced by invariance under a discrete symmetry, the product of parity and time-reversal symmetry, PT. It was shown that, if PT is unbroken, energies were, in fact, positive, and unitarity was satisfied. Since quantum mechanics is quantum field theory in one dimension--time--it was natural to extend this idea to higher-dimensional field theory, and in fact an apparently viable version of PT-invariant quantum electrodynamics (QED) was proposed. However, it has proved difficult to establish that the unitarity of the scattering matrix, for example, the Källén spectral representation for the photon propagator, can be maintained in this theory. This has led to questions of whether, in fact, even quantum mechanical systems are consistent with probability conservation when Green's functions are examined, since the latter have to possess physical requirements of analyticity. The status of PT QED will be reviewed in this paper, as well as the general issue of unitarity.
$\\mathcal{PT}$-symmetric mode-locking
Longhi, Stefano
2016-01-01
Parity-time ($\\mathcal{PT}$) symmetry is one of the most important accomplishments in optics over the past decade. Here the concept of $\\mathcal{PT}$ mode-locking of a laser is introduced, in which active phase locking of cavity axial modes is realized by asymmetric mode coupling in a complex time crystal. $\\mathcal{PT}$ mode-locking shows a transition from single to double pulse emission as the $\\mathcal{PT}$ symmetry breaking point is crossed. The transition can show a turbulent behavior, depending on a dimensionless modulation parameter that plays the same role as the Reynolds number in hydrodynamic flows.
Potential risk and its influencing factors for separated bicycle paths.
Xu, Cheng; Yang, Ying; Jin, Sheng; Qu, Zhaowei; Hou, Lei
2016-02-01
In this paper, we propose two potential risk indicators to define and evaluate the safety of bicycle path at the microscopic level. Field bicycle data were collected from three survey sites under different traffic conditions. These two risk indicators based on speed dispersion were proposed and calculated during each 5-min interval. The risk influences of various widths of bicycle path and traffic conditions were analyzed by using one-way ANOVA. We further proposed a generalized linear model (GLM) for modeling and analyzing the relationships between bicycle risks and v/c ratio and percentages of electric bicycles, male cyclists, young cyclists, and loaded cyclists. The stepwise regression models were applied for determination of coefficients. The results show that the influences of gender and age of cyclists on potential risks are not significant. The risks increase with the width of bicycle path and percentage of electric bicycles, while only for wider bicycle path (4-lane case in this study), the risks are associated with whether or not cyclists are loaded. The findings could contribute for analysis and evaluation of the safety for bicycle path. Copyright © 2015 Elsevier Ltd. All rights reserved.
Level crossings in complex two-dimensional potentials
Indian Academy of Sciences (India)
Qing-Hai Wang
2009-08-01
Two-dimensional $\\mathcal{PT}$-symmetric quantum-mechanical systems with the complex cubic potential 12 = 2 + 2 + 2 and the complex Hénon–Heiles potential HH = 2 + 2 + (2 − 3/3) are investigated. Using numerical and perturbative methods, energy spectra are obtained to high levels. Although both potentials respect the $\\mathcal{PT}$ symmetry, the complex energy eigenvalues appear when level crossing happens between same parity eigenstates.
Separable Representation of Phenomenological Optical Potentials of Woods-Saxon Type
Hlophe, L; Johnson, R C; Upadhyay, N J; Nunes, F M; Arbanas, G; Eremenko, V; Escher, J E; Thompson, I J
2013-01-01
Background: One important ingredient for many applications of nuclear physics to astrophysics, nuclear energy, and stockpile stewardship are cross sections for reactions of neutrons with rare isotopes. Since direct measurements are often not feasible, indirect methods, e.g. (d,p) reactions, should be used.} Those (d,p) reactions may be viewed as three-body reactions and described with Faddeev techniques. Purpose: Faddeev equations in momentum space have a long tradition of utilizing separable interactions in order to arrive at sets of coupled integral equations in one variable. While there exist several separable representations for the nucleon-nucleon interaction, the optical potential between a neutron (proton) and a nucleus is not readily available in separable form. The purpose of this paper is to introduce a separable representation for complex phenomenological optical potentials of Woods-Saxon type. Results: Starting from a global optical potential, a separable representation thereof is introduced based...
Institute of Scientific and Technical Information of China (English)
Lee Teck-Ghee; Wong Cheuk-Yin; Wang Lee-Shien
2008-01-01
This paper evaluates the interaction potential between a hydrogen and an antihydrogen using the second-order perturbation theory within the framework of the four-body system in a separable two-body basis. It finds that the H-H interaction potential possesses the peculiar features of a shallow local minimum located around interatomic separations of r ～ 6a.u. and a barrier rising at r<～ 5a.u.
Indian Academy of Sciences (India)
XIE QIONGTAO; YAN LINA; WANG LINMAO; FU JUN
2016-05-01
We investigate both the non-Hermitian parity–time-(PT-)symmetric and Hermitianasymmetric volcano potentials, and present the analytical solution in terms of the confluent Heun function. Under certain special conditions, the confluent Heun function can be terminated as a polynomial, thereby leading to certain exact analytical results. It is found that the non-Hermitian PTsymmetric volcano potentials support the normalizable and non-normalizable reflectionless stateswith real energies. The Hermitian asymmetric volcano potentials allow normalizable reflectionless states with complex energies.
Development of alkaline solution separations for potential partitioning of used nuclear fuels
Energy Technology Data Exchange (ETDEWEB)
Jarvinen, Gordon D [Los Alamos National Laboratory; Runde, Wolfgang H [Los Alamos National Laboratory; Goff, George S [Los Alamos National Laboratory
2009-01-01
The processing of used nuclear fuel in alkaline solution provides potentially useful new selectivity for separating the actinides from each other and f rom the fission products. Over the ast decade, several research teams around the world have considered dissolution of used fuel in alkaline solution and further partitioning in this medium as an alternative to acid dissolution. The chemistry of the actinides and fission products in alkaline soilltion requires extensive investigation to more carefully evaluate its potential for developing useful separation methods for used nuclear fueI.
The 2H Electric Dipole Moment in a Separable Potential Approach
Directory of Open Access Journals (Sweden)
Afnan I.R.
2010-04-01
Full Text Available Measurement of the electric dipole moment (EDM of 2H or of 3He may well come prior to the coveted measurement of the neutron EDM. Exact model calculations for the deuteron are feasible, and we explore here the model dependence of such deuteron EDM calculations. We investigate in a separable potential approach the relationship of the full model calculation to the plane wave approximation, correct an error in an early potential model result, and examine the tensor force aspects of the model results as well as the eﬀect of the short range repulsion found in the realistic, contemporary potential model calculations of Liu and Timmermans. We conclude that, because one-pion exchange dominates the EDM calculation, separable potential model calculations should provide an adequate picture of the 2H EDM until better than 10% measurements are achieved.
The 2H Electric Dipole Moment in a Separable Potential Approach
Gibson, B. F.; Afnan, I. R.
2010-04-01
Measurement of the electric dipole moment (EDM) of 2H or of 3He may well come prior to the coveted measurement of the neutron EDM. Exact model calculations for the deuteron are feasible, and we explore here the model dependence of such deuteron EDM calculations. We investigate in a separable potential approach the relationship of the full model calculation to the plane wave approximation, correct an error in an early potential model result, and examine the tensor force aspects of the model results as well as the effect of the short range repulsion found in the realistic, contemporary potential model calculations of Liu and Timmermans. We conclude that, because one-pion exchange dominates the EDM calculation, separable potential model calculations should provide an adequate picture of the 2H EDM until better than 10% measurements are achieved.
Spontaneous breakdown of $\\mathcal{PT}$ symmetry in the complex Coulomb potential
Indian Academy of Sciences (India)
G Lévai
2009-08-01
The $\\mathcal{PT}$ symmetry of the Coulomb potential and its solutions are studied along trajectories satisfying the $\\mathcal{PT}$ symmetry requirement. It is shown that with appropriate normalization constant the general solutions can be chosen $\\mathcal{PT}$ -symmetric if the parameter that corresponds to angular momentum in the Hermitian case is real. $\\mathcal{PT}$ symmetry is spontaneously broken, however, for complex values of the form $L = − \\dfrac{1}{2} + i$. In this case the potential remains $\\mathcal{PT}$ -symmetric, while the two independent solutions are transformed to each other by the $\\mathcal{PT}$ operation and at the same time, the two series of discrete energy eigenvalues turn into each other’s complex conjugate.
Exactly separable Bohr Hamiltonian with the Killingbeck potential for triaxial nuclei
Neyazi, H.; Rajabi, A. A.; Hassanabadi, H.
2016-01-01
After pioneering work by Bohr, Mottelson and their numerous colleagues, the essential framework for understanding collective model is introduced. One of the applications of this framework is the study of shape phase transition, vibrational and rotational energy spectrum of nuclei. We consider the Bohr Hamiltonian and solve the beta and gamma part equation of it, by considering that reduced potential and wave function are exactly separable. In the beta part equation we consider the Killingbeck potential and derive the wave function and energy spectrum of it.
Liu, Weifeng; Sun, Baiqi; Zhang, Duchao; Chen, Lin; Yang, Tianzu
2017-08-01
A new process of sulfide precipitation under controlled potential was proposed to separate selectively similar metals in a Bis(2-ethylhexyl) phosphoric acid (P204) stripping solution of the Co extraction system. Theoretical calculations revealed that Cu2+, Co2+, Zn2+, and Mn2+ could be separated by fractional precipitation with sulfide by controlling the solution potential and pH value simultaneously. The results demonstrated a Cu precipitation ratio reaching 99.9% during sulfide precipitation of Cu at the potential of 330 mV; the Cu/Co mass ratio in the Cu precipitate was 224. The Co precipitation ratio in the xanthate precipitation of Co, at a potential of 170 mV, was 99.9%, and the Co/Zn mass ratio in the Co precipitate was 28.0. The Zn precipitation ratio reached 99.9% for sulfide precipitation of Zn at the potential of 30 mV, and the Zn/Mn mass ratio in the Zn precipitate was 1.41. The Mn precipitation ratio reached 99.9% after neutralization.
[Experimental study on methane potentials of source-separated BMW and individual waste materials].
Feng, Lei; Li, Run-dong; Li, Yan-ji; Ke, Xin; Wei, Li-hong; Luo, Xiao-song
2008-08-01
A laboratory procedure is described for measuring methane potentials of source-separated bio-organic municipal waste (BMW). Triplicate reactors with about 20 grams fresh material were incubated at 37 degrees C with 300 mL inoculum from Shenyang wastewater treatment plant and the methane production was followed over a 50 d period by regular measurement of methane on a gas chromatograph. At 37 degrees C, the methane production efficiency of source-separated BMW and individual waste materials was: starch > BMW > protein > food oil > fat > paper. For the source-separated BMW,starch,protein,food oil,fat and paper, the methane potential (CH4/VS) of 218.15, 209.11, 194.20, 238.86, 257.82 and 131.41 mL/g were found,and ultimate biodegradability of 6 difference materials were 67.73%, 72.88%, 65.84%, 78.38%, 74.11% and 47.98%, respectively.
Energy Technology Data Exchange (ETDEWEB)
Laplace, A.; Peron, F.; Marrot, F.; Lacquement, J. [DRCP/SCPS/LPP - CEA/CEN Valrho - BP 17171 - 30207 Bagnols/Ceze (France)
2008-07-01
The objective of this paper is the comparison of molten fluoride and chloride salts potentialities for Am/Nd separation by electrodeposition on inert cathode, on a purely thermodynamic point of view. The molten LiF-CaF{sub 2} eutectic (77-23 mol.%, at 780 deg. C) was considered for this study. Cyclic voltammetry showed a one step Am(III)/Am reduction at a potential of {approx_equal}+0.5 V vs. Li{sup +}/Li. A potential difference of 290 mV between Am and Nd metallic deposition was estimated by square-wave voltammetry. This Am/Nd potential difference is more important than in molten chlorides (220 mV in the LiCl-KCl eutectic at 500 deg. C). Moreover in molten fluoride salt, the americium and neodymium (+II) oxidation state is not stable contrary to the molten chloride one where corrosion of deposited Am would be potential. However this larger potential difference in molten fluorides is quite balanced by the higher working temperature. (authors)
Scaling functions of two-neutron separation energies of $^{20}C$ with finite range potentials
Shalchi, M A; Yamashita, M T; Tomio, Lauro; Frederico, T
2015-01-01
The behaviour of an Efimov excited state is studied within a three-body Faddeev formalism for a general neutron-neutron-core system, where neutron-core is bound and neutron-neutron is unbound, by considering zero-ranged as well as finite-ranged two-body interactions. For the finite-ranged interactions we have considered a one-term separable Yamaguchi potential. The main objective is to study range corrections in a scaling approach, with focus in the exotic carbon halo nucleus $^{20}C$.
Scaling functions of two-neutron separation energies of 20C with finite range potentials
Shalchi, M. A.; Hadizadeh, M. R.; Yamashita, M. T.; Tomio, Lauro; Frederico, T.
2016-03-01
The behaviour of an Efimov excited state is studied within a three-body Faddeev formalism for a general neutron-neutron-core system, where neutron-core is bound and neutron-neutron is unbound, by considering zero-ranged as well as finite-ranged two-body interactions. For the finite-ranged interactions we have considered a one-term separable Yamaguchi potential. The main objective is to study range corrections in a scaling approach, with focus in the exotic carbon halo nucleus 20C.
Scaling functions of two-neutron separation energies of 20C with finite range potentials
Directory of Open Access Journals (Sweden)
Shalchi M. A.
2016-01-01
Full Text Available The behaviour of an Efimov excited state is studied within a three-body Faddeev formalism for a general neutron-neutron-core system, where neutron-core is bound and neutron-neutron is unbound, by considering zero-ranged as well as finite-ranged two-body interactions. For the finite-ranged interactions we have considered a one-term separable Yamaguchi potential. The main objective is to study range corrections in a scaling approach, with focus in the exotic carbon halo nucleus 20C.
Suparmi, A.; Cari, C.; Deta, U. A.; Handhika, J.
2016-11-01
The non-relativistic energies and wave functions of extended hyperbolic Scarf I plus separable non-central shape invariant potential in four dimensions are investigated using Supersymmetric Quantum Mechanics (SUSY QM) Approach. The three dimensional separable non-central shape invariant angular potential consists of trigonometric Scarf II, Manning Rosen and Poschl-Teller potentials. The four dimensional Schrodinger equation with separable shape invariant non-central potential is reduced into four one dimensional Schrodinger equations through variable separation method. By using SUSY QM, the non-relativistic energies and radial wave functions are obtained from radial Schrodinger equation, the orbital quantum numbers and angular wave functions are obtained from angular Schrodinger equations. The extended potential means there is perturbation terms in potential and cause the decrease in energy spectra of Scarf I potential.
Regional-residual separation of potential field: An example from Tunisia
Gabtni, Hakim; Jallouli, Chokri
2017-02-01
We present a regional-residual separation procedure for potential field data (gravity or magnetic) based on the integration of least-squares polynomial, power density spectrum and Upward continuation techniques. The proposed procedure is composed by 6 fundamental steps: 1) gridding of the total potential field; 2) least-squares polynomial approximation to calculate polynomial regionals; 3) applying power density spectrum technique to estimate the depth of the deepest source; 4) upward continuation to attenuate the effect of shallower sources; 5) comparing the produced polynomial regional approximations and upward continuation to choose the suitable regional and finally 6) computation of the residual. The proposed procedure was applied to synthetic case and real gravity data from Tunisia.
Energy Technology Data Exchange (ETDEWEB)
Chester, R.O.; Kirkscey, K.A.; Randolph, M.L.
1979-09-01
Hazards of chemical potentially associated with the advanced isotope separation processes are estimated based on open literature references. The tentative quantity of each chemical associated with the processes and the toxicity of the chemical are used to estimate this hazard. The chemicals thus estimated to be the most potentially hazardous to health are fluorine, nitric acid, uranium metal, uranium hexafluoride, and uranium dust. The estimated next most hazardous chemicals are bromine, hydrobromic acid, hydrochloric acid, and hydrofluoric acid. For each of these chemicals and for a number of other process-associated chemicals the following information is presented: (1) any applicable standards, recommended standards and their basis; (2) a brief discussion to toxic effects including short exposure tolerance, atmospheric concentration immediately hazardous to life, evaluation of exposures, recommended control procedures, chemical properties, and a list of any toxicology reviews; and (3) recommendations for future research.
Xue, Jinkai
2011-07-01
The major limitation, which hinders the wider application of membrane technology and increases the operating costs of membranes involved in wastewater treatment plants, is membrane fouling induced by organic matter. Extracellular polymeric products (EPS) and soluble microbial products (SMP) are the two most mentioned major foulants in publications, for which the debate on precise definitions seems to be endless. Therefore, a concept of sludge water, which conceptually covers both EPS and SMP, has been developed in this research. A standard procedure of sludge water separation, which is centrifugation at 4000g for 15 min followed by 1.2μm glass fiber filter filtration, was established based on separation experiments with membrane tank sludge from the KAUST MBR wastewater treatment plant. Afterwards, sludge waters from the KAUST MBR WWTP anoxic tank, aerobic tank and membrane tank as well as sludge waters from the Jeddah WWTP anoxic tank, aerobic tank and secondary effluent were produced through the previously developed standard procedure. The obtained sludge water samples were thereafter characterized with TOC/COD, LC-‐OCD and F-‐EEM, which showed that KAUST anoxic/ aerobic /membrane tank sludge waters had similar characteristics for all investigated parameters, yet the influent naturally had a higher DOC and biopolymer concentration. Moreover, lower TOC/COD, negligible biopolymers and low levels of humics were found in KAUST effluent. Compared with the KAUST MBR WWTP, the Jeddah WWTP’s sludge waters generally had higher DOC and biopolymer concentrations. To investigate sludge water fouling potential, the KAUST membrane tank sludge water as well as the Jeddah secondary effluent were filtrated through a membrane array consisting of an ultrafiltration (UF) Millipore RC10kDa at the first step followed by a nanofiltration (NF) KOCH Acid/Base stable NF200 at the second step. It was found that cake layer and standard blocking occurred simultaneously during both
Mass, charge, and energy separation by selective acceleration with a traveling potential hill
Tung, L. Schwager; Barr, W. L.; Lowder, R. S.; Post, R. F.
1996-10-01
A traveling electric potential hill has been used to generate an ion beam with an energy distribution that is mass dependent from a monoenergetic ion beam of mixed masses. This effect can be utilized as a novel method for mass separation applied to identification or enrichment of ions (e.g., of elements, isotopes, or molecules). This theory for mass-selective acceleration is presented here and is shown to be confirmed by experiment and by a time-dependent particle-in-cell computer simulation. Results show that monoenergetic ions with the particular mass of choice are accelerated by controlling the hill potential and the hill velocity. The hill velocity is typically 20%-30% faster than the ions to be accelerated. The ability of the hill to pickup a particular mass uses the fact that small kinetic energy differences in the lab frame appear much larger in the moving hill frame. Ions will gain energy from the approaching hill if their relative energy in the moving hill frame is less than the peak potential of the hill. The final energy of these accelerated ions can be several times the source energy, which facilitates energy filtering for mass purification or identification. If the hill potential is chosen to accelerate multiple masses, the heaviest mass will have the greatest final energy. Hence, choosing the appropriate hill potential and collector retarding voltage will isolate ions with the lightest, heaviest, or intermediate mass. In the experimental device, called a Solitron, purified 20Ne and 22Ne are extracted from a ribbon beam of neon that is originally composed of 20Ne:22Ne in the natural ratio of 91:9. The isotopic content of the processed beam is determined by measuring the energy distribution of the detected current. These results agree with the theory. In addition to mass selectivity, our theory can also be applied to the filtration of an ion beam according to charge state or energy. Because of this variety of properties, the Solitron is envisioned to
PT-symmetric dimer of coupled nonlinear oscillators
Indian Academy of Sciences (India)
Avinash Khare
2015-11-01
We provide a systematic analysis of a prototypical nonlinear oscillator system respecting PT-symmetry, i.e., one of them has gain and the other an equal and opposite amount of loss. We first discuss various symmetries of the model. We show that both the linear system as well as a special case of the nonlinear system can be derived from a Hamiltonian, whose structure is similar to the Pais–Uhlenbeck Hamiltonian. Exact solutions are obtained in a few special cases. We show that the system is a superintegrable system within the rotating wave approximation (RWA). We also obtain several exact solutions of these RWA equations. Further, we point out a novel superposition in the context of periodic solutions in terms of Jacobi elliptic functions that we obtain in this problem. Finally, we briefly mention numerical results about the stability of some of the solutions.
Anomalous Light Scattering by Topological PT-symmetric Particle Arrays
Ling, C. W.; Choi, Ka Hei; Mok, T. C.; Zhang, Zhao-Qing; Fung, Kin Hung
2016-12-01
Robust topological edge modes may evolve into complex-frequency modes when a physical system becomes non-Hermitian. We show that, while having negligible forward optical extinction cross section, a conjugate pair of such complex topological edge modes in a non-Hermitian -symmetric system can give rise to an anomalous sideway scattering when they are simultaneously excited by a plane wave. We propose a realization of such scattering state in a linear array of subwavelength resonators coated with gain media. The prediction is based on an analytical two-band model and verified by rigorous numerical simulation using multiple-multipole scattering theory. The result suggests an extreme situation where leakage of classical information is unnoticeable to the transmitter and the receiver when such a -symmetric unit is inserted into the communication channel.
Twofold Transition in PT-symmetric Coupled Oscillators
2013-12-26
2Dipartimento di Matematica e Fisica Ennio De Giorgi, Università del Salento and I. N. F. N. Sezione di Lecce, Via Arnesano, I-73100 Lecce, Italy...supermode, as shown in Fig. 6, instead of two pairs of real frequencies. B. Unbalanced loss and gain Let us consider the general case (2) in which μ = ν...correspond to the eigenfunctions ψm,n(x,y). The eigenfunctions have the general form ψm,n(x,y) = e−(2axy+bx2+cy2)/2Pm,n(x,y), (12) where b = c∗ = 2(a
Phase-coupled optical diode based on PT symmetric system
Gao, Yong-Pan; Cao, Cong; Zhang, Yong; Wang, Tie-Jun; Wang, Chuan
2017-01-01
Here we investigate a phase-coupled parity-time symmetric plasmonic system, and theoretically achieved the all optical on-chip plasmonic diode using the coupled mode theory. The proposed symmetrical system consists of one loss cavity and one gain cavity each coupled with the waveguide, and we find that the controllable amplification of the input field can be achieved by changing the power coupling fraction between the resonators and the waveguide. Moreover, this loss-gain symmetric system could work as a frequency comb filter, and the operation on the device could be controlled by tuning the coupling strength between the two plasmonic cavities by tuning the coupling distance between the cavities and the waveguide.
Light propagation through a PT-symmetric photonic-crystal.
Konotop, Vladimir V; Mantsyzov, Boris I
2016-11-14
Light propagation through a finite-width periodically modulated layer obeying parity-time (PT) symmetry is considered. We consider the configuration when the resonant conditions of mode coupling by the grating are satisfied. It is shown that the dependence of the transmission and reflection coefficients on the slab width has resonant character featuring strong amplification of reflected and transmitted waves with negative angles. The dependence of the scattering data on the gain-and-loss intensity also feature strong resonances near the PT-symmetry breaking point, when the slab strongly amplifies waves reflected and transmitted with negative angles, provided the incident wave has a positive angle of incidence.
Institute of Scientific and Technical Information of China (English)
Jordan; Hristov; Ludmil; Fachikov
2007-01-01
This article deals with problems relevant to implementation of magnetically stabilized beds (MSB) as separation devices. The main issues discussed are: bed mechanics, bed structure, possibilities to create controllable filter media, etc. As examples several separation techniques are discussed: dust filtration-magnetic and non-magnetic, ion-exchange, copper cementation, yeast filtration from biological liquids, particle separation by density and magnetic properties, dangerous wastes removal. Only key publications will be quoted that provide a basis for further reading and study and relevant information.
DEFF Research Database (Denmark)
Hansen, Trine Lund; Svärd, Å; Angelidaki, Irini
2003-01-01
A research project has investigated the biogas potential of pre-screened source-separated organic waste. Wastes from five Danish cities have been pre-treated by three methods: screw press; disc screen; and shredder and magnet. This paper outlines the sampling procedure used, the chemical composit......A research project has investigated the biogas potential of pre-screened source-separated organic waste. Wastes from five Danish cities have been pre-treated by three methods: screw press; disc screen; and shredder and magnet. This paper outlines the sampling procedure used, the chemical...
Energy Technology Data Exchange (ETDEWEB)
Huff, D.D.
1999-01-01
Streamflow data are more useful for evaluating hydrologic model results and studying water quality once baseflow and storm runoff have been separated. However, it is important to select an appropriate hydrograph separation method. They examined tow methods and evaluated their conceptual basis, ease of application, cost of data processing, and acceptability of results. they chose the quick flow hydrograph separation method, which is in use at the Coweeta Hydrologic Laboratory, because it gives acceptable results and is easy and inexpensive to use. For regional assessment, they anticipate that the Coweeta program will be useful as an aid in developing general quantitative relationships between changes in land use and the associated changes in surface runoff yield and water quality degradation.
Clough, Geraldine; Chipperfield, Andrew; Byrne, Christopher; de Mul, Frits; Gush, Rodney
2009-01-01
Objective: To compare the output from a novel high power, wide separation laser Doppler flow probe (DP1-V2-HP, 4 mm, with IRLD20) with that of a standard flow probe (DP1-V2, 0.5 mm, with DRT4) (Moor UK) and to explore its potential for use in the noninvasive measurement of blood flow in deeper tissu
Bachar, Eytan; Stein, Daniel; Canetti, Laura; Gur, Eitan
2008-11-01
Due to the susceptibility of eating disorders (ED) to stressful life events, we wanted to examine longitudinally whether two childhood adversities: (1) surgery and (2) parental separation, will affect abnormal eating attitudes in adolescents. Consecutively for 4 years, the eating attitude test (EAT-26) and the eating disorder inventory-2 (EDI-2) questionnaires were administered to students from grades 7th through 10th and 8th through 11th. Multilevel analysis revealed that parental separation and oral or cosmetic dermatologic surgeries were significantly correlated with EAT-26 and EDI-2 scores throughout the 4 years of the study. Post-hoc interpretation suggests a connection between (A) chirurgic intervention in the oral cavity and problematic eating attitudes, and (B) cosmetic dermatologic surgery and greater awareness to body appearance-a feature which might characterize adolescents who are prone to develop ED.
Energy Technology Data Exchange (ETDEWEB)
Tang, Xiao-yan, E-mail: xytang@sjtu.edu.cn [Institute of System Science, School of Information Science Technology, East China Normal University, Shanghai 200241 (China); Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Faculty of Science, Ningbo University, Ningbo 315211 (China); Li, Jing [Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Liang, Zu-feng [Department of Physics, Hangzhou Normal University, Hangzhou 310036 (China); Wang, Jian-yong [Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China)
2014-04-01
The multilinear variable separation approach (MLVSA) is applied to a coupled modified Korteweg–de Vries and potential Boiti–Leon–Manna–Pempinelli equations, as a result, the potential fields u{sub y} and v{sub y} are exactly the universal quantity applicable to all multilinear variable separable systems. The generalized MLVSA is also applied, and it is found that u{sub y} (v{sub y}) is rightly the subtraction (addition) of two universal quantities with different parameters. Then interactions between periodic waves are discussed, for instance, the elastic interaction between two semi-periodic waves and non-elastic interaction between two periodic instantons. An attractive phenomenon is observed that a dromion moves along a semi-periodic wave.
Barnwell, R. W.
1981-01-01
The development of a potential-flow/boundary-layer method for calculating subsonic and transonic turbulent flow past airfoils with trailing-edge separation is reported. A moment-of-momentum integral boundary-layer method is used which employs the law-of-the-wall/law-of-the-wake velocity profile and a two-layer eddy-viscosity model and ignores the laminar sublayer. All integrals across the boundary layer are obtained in closed form. Separation is assumed to occur when the shearing-stress velocity vanishes. A closed-form solution is derived for separated-flow regions where the shearing stress is negligible. In the potential-flow method, the exact form of the airfoil boundary condition is used, but it is applied at the chord line rather than the airfoil surface. This allows the accurate computation of flow about airfoils at large angles of attack but permits the use of body-oriented Cartesian computational grids. The governing equation for the perturbation velocity potential contains several terms in addition to the classical small-disturbance terms.
Woodman, Keryn G; Coles, Chantal A; Lamandé, Shireen R; White, Jason D
2016-11-09
In recent years, complementary and alternative medicine has become increasingly popular. This trend has not escaped the Duchenne Muscular Dystrophy community with one study showing that 80% of caregivers have provided their Duchenne patients with complementary and alternative medicine in conjunction with their traditional treatments. These statistics are concerning given that many supplements are taken based on purely "anecdotal" evidence. Many nutraceuticals are thought to have anti-inflammatory or anti-oxidant effects. Given that dystrophic pathology is exacerbated by inflammation and oxidative stress these nutraceuticals could have some therapeutic benefit for Duchenne Muscular Dystrophy (DMD). This review gathers and evaluates the peer-reviewed scientific studies that have used nutraceuticals in clinical or pre-clinical trials for DMD and thus separates the credible from the conjecture.
Potential of metal-organic frameworks for separation of xenon and krypton.
Banerjee, Debasis; Cairns, Amy J; Liu, Jian; Motkuri, Radha K; Nune, Satish K; Fernandez, Carlos A; Krishna, Rajamani; Strachan, Denis M; Thallapally, Praveen K
2015-02-17
CONSPECTUS: The total world energy demand is predicted to rise significantly over the next few decades, primarily driven by the continuous growth of the developing world. With rapid depletion of nonrenewable traditional fossil fuels, which currently account for almost 86% of the worldwide energy output, the search for viable alternative energy resources is becoming more important from a national security and economic development standpoint. Nuclear energy, an emission-free, high-energy-density source produced by means of controlled nuclear fission, is often considered as a clean, affordable alternative to fossil fuel. However, the successful installation of an efficient and economically viable industrial-scale process to properly sequester and mitigate the nuclear-fission-related, highly radioactive waste (e.g., used nuclear fuel (UNF)) is a prerequisite for any further development of nuclear energy in the near future. Reprocessing of UNF is often considered to be a logical way to minimize the volume of high-level radioactive waste, though the generation of volatile radionuclides during reprocessing raises a significant engineering challenge for its successful implementation. The volatile radionuclides include but are not limited to noble gases (predominately isotopes of Xe and Kr) and must be captured during the process to avoid being released into the environment. Currently, energy-intensive cryogenic distillation is the primary means to capture and separate radioactive noble gas isotopes during UNF reprocessing. A similar cryogenic process is implemented during commercial production of noble gases though removal from air. In light of their high commercial values, particularly in lighting and medical industries, and associated high production costs, alternate approaches for Xe/Kr capture and storage are of contemporary research interest. The proposed pathways for Xe/Kr removal and capture can essentially be divided in two categories: selective absorption by
Directory of Open Access Journals (Sweden)
Keryn G. Woodman
2016-11-01
Full Text Available In recent years, complementary and alternative medicine has become increasingly popular. This trend has not escaped the Duchenne Muscular Dystrophy community with one study showing that 80% of caregivers have provided their Duchenne patients with complementary and alternative medicine in conjunction with their traditional treatments. These statistics are concerning given that many supplements are taken based on purely “anecdotal” evidence. Many nutraceuticals are thought to have anti-inflammatory or anti-oxidant effects. Given that dystrophic pathology is exacerbated by inflammation and oxidative stress these nutraceuticals could have some therapeutic benefit for Duchenne Muscular Dystrophy (DMD. This review gathers and evaluates the peer-reviewed scientific studies that have used nutraceuticals in clinical or pre-clinical trials for DMD and thus separates the credible from the conjecture.
Comparison of the pattern reversal visual evoked potential mediated by separate cone systems
DEFF Research Database (Denmark)
Johnsen, B; Frederiksen, J.L.; Larsson, H.B.
1995-01-01
With the purpose of recording responses mediated by the 3 cone systems visual evoked potentials (VEPs) were elicited by the reversal of monochromatic checkerboards superimposed upon strong monochromatic backgrounds (yellow, purple and blue-green). The sensitivity to light of various wave lengths...
Wiese, Holger; Altmann, Carolin S; Schweinberger, Stefan R
2014-04-01
The present study examined effects of attractiveness on behavioral and event-related potential (ERP) correlates of face memory. Extending previous reports, we controlled for potential moderating effects of distinctiveness, a variable known to affect memory. Attractive and unattractive faces were selected on the basis of a rating study, and were matched for distinctiveness. In a subsequent recognition memory experiment, we found more accurate memory for unattractive relative to attractive faces. Additionally, an attractiveness effect in the early posterior negativity (EPN) during learning, with larger amplitudes for attractive than unattractive faces, correlated significantly with the magnitude of the memory advantage for unattractive faces at test. These findings establish a contribution of attractiveness to face memory over and above the well-known effect of distinctiveness. Additionally, as the EPN is typically enhanced for affective stimuli, our ERP results imply that the processing of emotionally relevant attractive faces during learning may hamper their encoding into memory. Copyright © 2014 Elsevier Ltd. All rights reserved.
Action potential waveform variability limits multi-unit separation in freely behaving rats.
Directory of Open Access Journals (Sweden)
Peter Stratton
Full Text Available Extracellular multi-unit recording is a widely used technique to study spontaneous and evoked neuronal activity in awake behaving animals. These recordings are done using either single-wire or multiwire electrodes such as tetrodes. In this study we have tested the ability of single-wire electrodes to discriminate activity from multiple neurons under conditions of varying noise and neuronal cell density. Using extracellular single-unit recording, coupled with iontophoresis to drive cell activity across a wide dynamic range, we studied spike waveform variability, and explored systematic differences in single-unit spike waveform within and between brain regions as well as the influence of signal-to-noise ratio (SNR on the similarity of spike waveforms. We also modelled spike misclassification for a range of cell densities based on neuronal recordings obtained at different SNRs. Modelling predictions were confirmed by classifying spike waveforms from multiple cells with various SNRs using a leading commercial spike-sorting system. Our results show that for single-wire recordings, multiple units can only be reliably distinguished under conditions of high recording SNR (≥ 4 and low neuronal density (≈ 20,000/ mm(3. Physiological and behavioural changes, as well as technical limitations typical of awake animal preparations, reduce the accuracy of single-channel spike classification, resulting in serious classification errors. For SNR <4, the probability of misclassifying spikes approaches 100% in many cases. Our results suggest that in studies where the SNR is low or neuronal density is high, separation of distinct units needs to be evaluated with great caution.
Energy Technology Data Exchange (ETDEWEB)
Luca, V. [Programa Nacional de Gestion de Residuos Radiactivos, Comision Nacional de Energia Atomica, Centro Atomico Constituyentes, Av. General, Paz 1499, 1650 San Martin, Provincia de Buenos Aires (Argentina)
2013-07-01
Functionalized meso-porous materials are a class of hybrid organic-inorganic material in which a meso-porous metal oxide framework is functionalized with multifunctional organic molecules. These molecules may contain one or more anchor groups that form strong bonds to the pore surfaces of the metal oxide framework and free functional groups that can impart and or modify the functionality of the material such as for binding metal ions in solution. Such materials have been extensively studied over the past decade and are of particular interest in absorption applications because of the tremendous versatility in choosing the composition and architecture of the metal oxide framework and the nature of the functional organic molecule as well as the efficient mass transfer that can occur through a well-designed hierarchically porous network. A sorbent for nuclear applications would have to be highly selective for particular radio nuclides, it would need to be hydrolytically and radiolytically stable, and it would have to possess reasonable capacity and fast kinetics. The sorbent would also have to be available in a form suitable for use in a column. Finally, it would also be desirable if once saturated with radio nuclides, the sorbent could be recycled or converted directly into a ceramic or glass waste form suitable for direct repository disposal or even converted directly into a material that could be used as a transmutation target. Such a cradle-to- grave strategy could have many benefits in so far as process efficiency and the generation of secondary wastes are concerned.This paper will provide an overview of work done on all of the above mentioned aspects of the development of functionalized meso-porous adsorbent materials for the selective separation of lanthanides and actinides and discuss the prospects for future implementation of a cradle-to-grave strategy with such materials. (author)
Comparison of the pattern reversal visual evoked potential mediated by separate cone systems
DEFF Research Database (Denmark)
Johnsen, B; Frederiksen, J.L.; Larsson, H.B.
1995-01-01
With the purpose of recording responses mediated by the 3 cone systems visual evoked potentials (VEPs) were elicited by the reversal of monochromatic checkerboards superimposed upon strong monochromatic backgrounds (yellow, purple and blue-green). The sensitivity to light of various wave lengths...... were measured as the reciprocal of the intensity necessary to elicit a VEP amplitude of 3 microV. The spectral sensitivity curves based on this VEP amplitude criterion in the presence of blue-green, purple and yellow adaptation showed peak sensitivities in the red, the green and the blue part...
Indian Academy of Sciences (India)
Malay Rana; Amalendu Chandra
2008-06-01
We have performed a series of molecular dynamics simulations of water containing two nanoscopic hydrophobic plates to investigate the modifications of the density and hydrogen bond distributions of water in the vicinity of the surfaces. Our primary goal is to look at the effects of plate thickness, solute–solvent interaction and also interplate separation on the solvent structure in the confined region between two graphite-like plates and also near the outer surfaces of the plates. The thickness of the plates is varied by considering single and triple-layer graphite plates and the interaction potential is varied by tuning the attractive strength of the 12–6 pair interaction potential between a carbon atom of the graphite plates and a water molecule. The calculations are done for four different values of the tuning parameter ranging from fully Lennard–Jones to pure repulsive pair interactions. It is found that both the solvation characteristics and hydrogen bond distributions can depend rather strongly on the strength of the attractive part of the solute–water interaction potential. The thickness of the plates, however, is found to have only minor effects on the density profiles and hydrogen bond network. This indicates that the long range electrostatic interactions between water molecules on the two opposite sides of the same plate do not make any significant contribution to the overall solvation structure of these hydrophobic plates. The solvation characteristics are primarily determined by the balance between the loss of energy due to hydrogen bond network disruption, cavity repulsion potential and offset of the same by attractive component of the solute–water interactions. Our studies with different system sizes show that the essential features of solvation properties, e.g. wetting and dewetting characteristics for different interplate separations and interaction potentials, are also present in relatively smaller systems consisting of a few hundred
Franciò, Giancarlo; Hintermair, Ulrich; Leitner, Walter
2015-12-28
Solution-phase catalysis using molecular transition metal complexes is an extremely powerful tool for chemical synthesis and a key technology for sustainable manufacturing. However, as the reaction complexity and thermal sensitivity of the catalytic system increase, engineering challenges associated with product separation and catalyst recovery can override the value of the product. This persistent downstream issue often renders industrial exploitation of homogeneous catalysis uneconomical despite impressive batch performance of the catalyst. In this regard, continuous-flow systems that allow steady-state homogeneous turnover in a stationary liquid phase while at the same time effecting integrated product separation at mild process temperatures represent a particularly attractive scenario. While continuous-flow processing is a standard procedure for large volume manufacturing, capitalizing on its potential in the realm of the molecular complexity of organic synthesis is still an emerging area that requires innovative solutions. Here we highlight some recent developments which have succeeded in realizing such systems by the combination of near- and supercritical fluids with homogeneous catalysts in supported liquid phases. The cases discussed exemplify how all three levels of continuous-flow homogeneous catalysis (catalyst system, separation strategy, process scheme) must be matched to locate viable process conditions.
Directory of Open Access Journals (Sweden)
Altuğ Arda
2017-01-01
Full Text Available We find the exact bound state solutions and normalization constant for the Dirac equation with scalar-vector-pseudoscalar interaction terms for the generalized Hulthén potential in the case where we have a particular mass function m(x. We also search the solutions for the constant mass where the obtained results correspond to the ones when the Dirac equation has spin and pseudospin symmetry, respectively. After giving the obtained results for the nonrelativistic case, we search then the energy spectra and corresponding upper and lower components of Dirac spinor for the case of PT-symmetric forms of the present potential.
A note on the PT-invariant periodic potential V(x)=4 cos^2 x + 4 i V_0 sin 2x
Midya, Bikashkali; Roychoudhury, Rajkumar
2010-01-01
It is shown that the PT symmetric Hamiltonian with the periodic potential V(x) = 4 cos^2 x + 4 i V_0 sin 2x can be mapped into a Hermitian Hamiltonian for $V_0<0.5$, by a similarity transformation. It is also shown that there exist a second critical point of the potential V(x), apart from the known critical point $V_0=0.5$, for $V_0^c ~ .888437$ after which no part of the eigenvalues and the band structure remains real. Relevant physical consequence of this finding has been pointed out.
DEFF Research Database (Denmark)
Naroznova, Irina; Møller, Jacob; Scheutz, Charlotte
2016-01-01
This study is dedicated to characterising the chemical composition and biochemical methane potential (BMP) of individual material fractions in untreated Danish source-separated organic household waste (SSOHW). First, data on SSOHW in different countries, available in the literature, were evaluated...... and then, secondly, laboratory analyses for eight organic material fractions comprising Danish SSOHW were conducted. No data were found in the literature that fully covered the objectives of the present study. Based on laboratory analyses, all fractions were assigned according to their specific properties...... in Denmark (untreated) was calculated, and the BMP contribution of the individual material fractions was then evaluated. Material fractions of the two general waste types, defined as "food waste" and "fibre-rich waste," were found to be anaerobically degradable with considerable BMP. Material degradability...
DEFF Research Database (Denmark)
Naroznova, Irina; Møller, Jacob; Scheutz, Charlotte
2016-01-01
This study compared the environmental profiles of anaerobic digestion (AD) and incineration, in relation to global warming potential (GWP), for treating individual material fractions that may occur in source-separated organic household waste (SSOHW). Different framework conditions representative...
Jiang, Chun-Sheng; Yang, Mengjin; Zhou, Yuanyuan; To, Bobby; Nanayakkara, Sanjini U; Luther, Joseph M; Zhou, Weilie; Berry, Joseph J; van de Lagemaat, Jao; Padture, Nitin P; Zhu, Kai; Al-Jassim, Mowafak M
2015-09-28
Organometal-halide perovskite solar cells have greatly improved in just a few years to a power conversion efficiency exceeding 20%. This technology shows unprecedented promise for terawatt-scale deployment of solar energy because of its low-cost, solution-based processing and earth-abundant materials. We have studied charge separation and transport in perovskite solar cells-which are the fundamental mechanisms of device operation and critical factors for power output-by determining the junction structure across the device using the nanoelectrical characterization technique of Kelvin probe force microscopy. The distribution of electrical potential across both planar and porous devices demonstrates p-n junction structure at the TiO2/perovskite interfaces and minority-carrier diffusion/drift operation of the devices, rather than the operation mechanism of either an excitonic cell or a p-i-n structure. Combining the potential profiling results with solar cell performance parameters measured on optimized and thickened devices, we find that carrier mobility is a main factor that needs to be improved for further gains in efficiency of the perovskite solar cells.
Jiang, Chun-Sheng; Yang, Mengjin; Zhou, Yuanyuan; To, Bobby; Nanayakkara, Sanjini U.; Luther, Joseph M.; Zhou, Weilie; Berry, Joseph J.; van de Lagemaat, Jao; Padture, Nitin P.; Zhu, Kai; Al-Jassim, Mowafak M.
2015-09-01
Organometal-halide perovskite solar cells have greatly improved in just a few years to a power conversion efficiency exceeding 20%. This technology shows unprecedented promise for terawatt-scale deployment of solar energy because of its low-cost, solution-based processing and earth-abundant materials. We have studied charge separation and transport in perovskite solar cells--which are the fundamental mechanisms of device operation and critical factors for power output--by determining the junction structure across the device using the nanoelectrical characterization technique of Kelvin probe force microscopy. The distribution of electrical potential across both planar and porous devices demonstrates p-n junction structure at the TiO2/perovskite interfaces and minority-carrier diffusion/drift operation of the devices, rather than the operation mechanism of either an excitonic cell or a p-i-n structure. Combining the potential profiling results with solar cell performance parameters measured on optimized and thickened devices, we find that carrier mobility is a main factor that needs to be improved for further gains in efficiency of the perovskite solar cells.
Quasi-point separation of variables for the Hénon-Heiles system and a system with quartic potential
Rauch-Wojciechowski, S
1996-01-01
We examine the problem of integrability of two-dimensional Hamiltonian systems by means of separation of variables. The systematic approach to construction of the special non-pure coordinate separation of variables for certain natural two-dimensional Hamiltonians is presented. The relations with SUSY quantum mechanics are discussed.
Naroznova, Irina; Møller, Jacob; Scheutz, Charlotte
2016-04-01
This study is dedicated to characterising the chemical composition and biochemical methane potential (BMP) of individual material fractions in untreated Danish source-separated organic household waste (SSOHW). First, data on SSOHW in different countries, available in the literature, were evaluated and then, secondly, laboratory analyses for eight organic material fractions comprising Danish SSOHW were conducted. No data were found in the literature that fully covered the objectives of the present study. Based on laboratory analyses, all fractions were assigned according to their specific properties in relation to BMP, protein content, lipids, lignocellulose biofibres and easily degradable carbohydrates (carbohydrates other than lignocellulose biofibres). The three components in lignocellulose biofibres, i.e. lignin, cellulose and hemicellulose, were differentiated, and theoretical BMP (TBMP) and material degradability (BMP from laboratory incubation tests divided by TBMP) were expressed. Moreover, the degradability of lignocellulose biofibres (the share of volatile lignocellulose biofibre solids degraded in laboratory incubation tests) was calculated. Finally, BMP for average SSOHW composition in Denmark (untreated) was calculated, and the BMP contribution of the individual material fractions was then evaluated. Material fractions of the two general waste types, defined as "food waste" and "fibre-rich waste," were found to be anaerobically degradable with considerable BMP. Material degradability of material fractions such as vegetation waste, moulded fibres, animal straw, dirty paper and dirty cardboard, however, was constrained by lignin content. BMP for overall SSOHW (untreated) was 404 mL CH4 per g VS, which might increase if the relative content of material fractions, such as animal and vegetable food waste, kitchen tissue and dirty paper in the waste, becomes larger.
Energy Technology Data Exchange (ETDEWEB)
Levy, Salomon, E-mail: slevy112@aol.com
2009-10-15
Interim, centralized, engineered (dry cask) storage facilities for USA light water power reactor spent nuclear fuel (SNF) should be implemented to complement and to offer much needed flexibility while the Nuclear Regulatory Commission is funded to complete its evaluation of the Yucca Mountain License and to subject it to public hearings. The interim sites should use the credo reproduced in Table 1 [Bunn, M., 2001. Interim Storage of Spent Nuclear Fuel. Harvard University and University of Tokyo] and involve both the industry and government. The sites will help settle the 50 pending lawsuits against the government and the $11 billion of potential additional liabilities for SNF delay damages if Yucca Mountain does not being operation in 2020 [DOE, 2008a. Report to Congress on the Demonstration of the Interim Storage of Spent Nuclear Fuel from Decommissioned Nuclear Power Stations (December)]. Under the developing consensus to proceed with closed fuel cycles, it will be necessary to develop SNF separation facilities with stringent requirements upon separation processes and upon generation of only highly resistant waste forms. The location of such facilities at the interim storage sites would offer great benefits to those sites and assure their long term viability by returning them to their original status. The switch from once-through to closed fuel cycle will require extensive time and development work as illustrated in 'The Path to Sustainable Nuclear Energy' [DOE, 2005. The Path to Sustainable Nuclear Energy. Basic and Applied Research Opportunities for Advanced Fuel Cycles. DOE (September)]. A carefully crafted long term program, funded for at least 5 years, managed by a strong joint government-industry team, and subjected to regular independent reviews should be considered to assure the program stability and success. The new uncertainty about Yucca Mountain role raises two key issues: (a) what to do with the weapons and other high level government
Bloomfield, John; Ward, Rob; Garcia-Bajo, Marieta; Hart, Alwyn
2014-05-01
A number of potential pathways can be identified for the migration of methane and contaminants associated with the shale gas extraction process to aquifers. These include the possible movement of contaminants from shale gas reservoirs that have been hydraulically fractured to overlying aquifers. The risk of contamination of an overlying aquifer is a function of i.) the separation of the potential shale gas source rock and the aquifer, ii.) the hydraulic characteristics (e.g. hydraulic conductivity, storage and hydrogeochemistry) of the rocks in the intervening interval, and iii.) regional and local physio-chemical gradients. Here we report on a national-scale study from the UK to assess the former, i.e. the vertical separation between potential shale gas source rocks and major aquifers, as a contribution to more informed management of the risks associated with shale gas development if and when it takes place in the UK. Eleven aquifers are considered in the study. These are aquifers that have been designated by the environment agencies of England (Environment Agency) and Wales (Natural Resources Wales) under the EU Water Framework Directive as being nationally important (Principal Aquifers). The shale gas source rocks have been defined on best publically available evidence for potential gas productivity and include both shales and clay formations. Based on a national geological fence diagram consisting of ~80 geological sections, totalling ~12,000km in length, down to >5km in depth, and with a typical spacing of 30km, the lower surfaces of each aquifer unit and upper surfaces of each shale/clay unit have been estimated at a spatial resolution of 3x3km. These surfaces have then been used to estimate vertical separations between pairs of shale/clay and aquifer units. The modelling process will be described and the aquifer, shale and separation maps presented and discussed. The aquifers are defined by geological units and since these geological units may be found at
Mamouri, Rodanthi-Elisavet; Ansmann, Albert
2017-09-01
We applied the recently introduced polarization lidar-photometer networking (POLIPHON) technique for the first time to triple-wavelength polarization lidar measurements at 355, 532, and 1064 nm. The lidar observations were performed at Barbados during the Saharan Aerosol Long-Range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in the summer of 2014. The POLIPHON method comprises the traditional lidar technique to separate mineral dust and non-dust backscatter contributions and the new, extended approach to separate even the fine and coarse dust backscatter fractions. We show that the traditional and the advanced method are compatible and lead to a consistent set of dust and non-dust profiles at simplified, less complex aerosol layering and mixing conditions as is the case over the remote tropical Atlantic. To derive dust mass concentration profiles from the lidar observations, trustworthy extinction-to-volume conversion factors for fine, coarse, and total dust are needed and obtained from an updated, extended Aerosol Robotic Network sun photometer data analysis of the correlation between the fine, coarse and total dust volume concentration and the respective fine, coarse, and total dust extinction coefficient for all three laser wavelengths. Conversion factors (total volume to extinction) for pure marine aerosol conditions and continental anthropogenic aerosol situations are presented in addition. As a new feature of the POLIPHON data analysis, the Raman lidar method for particle extinction profiling is used to identify the aerosol type (marine or anthropogenic) of the non-dust aerosol fraction. The full POLIPHON methodology was successfully applied to a SALTRACE case and the results are discussed. We conclude that the 532 nm polarization lidar technique has many advantages in comparison to 355 and 1064 nm polarization lidar approaches and leads to the most robust and accurate POLIPHON products.
On solving the Schrödinger equation for a complex deictic potential in one dimension
Indian Academy of Sciences (India)
Ram Mehar Singh
2014-09-01
Making use of an ansatz for the eigenfunction, we investigate closed-form solutions of the Schrödinger equation for an even power complex deictic potential and its variant in one dimension. For this purpose, extended complex phase-space approach is utilized and nature of the eigenvalue and the corresponding eigenfunction is determined by the analyticity property of the eigenfunction. The imaginary part of the energy eigenvalue exists only if the potential parameters are complex, whereas it reduces to zero for real coupling parameters and the result coincides with those derived from the invariance of Hamiltonian under $\\mathcal{PT}$ operations. Thus, a non-Hermitian Hamiltonian possesses real eigenvalue, if it is $\\mathcal{PT}$-symmetric.
PT-symmetry breaking with divergent potentials: lattice and continuum cases
Joglekar, Yogesh N; Saxena, Avadh
2014-01-01
We investigate the parity- and time-reversal ($\\mathcal{PT}$)-symmetry breaking in lattice models in the presence of long-ranged, non-hermitian, $\\mathcal{PT}$-symmetric potentials that remain finite or become divergent in the continuum limit. By scaling analysis of the fragile $\\mathcal{PT}$ threshold for an open finite lattice, we show that continuum loss-gain potentials $V_\\alpha(x)\\propto i |x|^\\alpha \\mathrm{sign}(x)$ have a positive $\\mathcal{PT}$-breaking threshold for $\\alpha>-2$, and a zero threshold for $\\alpha\\leq -2$. When $\\alpha<0$ localized states with complex (conjugate) energies in the continuum energy-band occur at higher loss-gain strengths. We investigate the signatures of $\\mathcal{PT}$-symmetry breaking in coupled waveguides, and show that the emergence of localized states dramatically shortens the relevant time-scale in the $\\mathcal{PT}$-symmetry broken region.
Institute of Scientific and Technical Information of China (English)
WANGRong-chang; DUSi-dan; GAODun-tang
2004-01-01
Event-related potentials (ERP) is an important type of brain dynamics in human cognition research. However, ERP is often submerged by the spontaneous brain activity EEG, for its relatively tiny scale. Further more, the brain activities collected from scalp electrodes are often inevitably contaminated by several kinds of artifacts, such as blinks, eye movements, muscle noise and power line interference. A new approach to correct these disturbances is presented using independent component analysis (ICA). This technique can effectively detect and extract ERP components from the measured electrodes recordings even if they are heavily contaminated. The results compare favorably to those obtained by parametric modeling. Besides, auto--adaptive projection of decomposed results to ERP components was also given. Through experiments, ICA proves to be highly capable of ERP extraction and S/N ratio improving.
Directory of Open Access Journals (Sweden)
Elena V Kushnerenko
2013-09-01
Full Text Available Orienting to salient events in the environment is a first step in the development of attention in young infants. Electrophysiological studies have indicated that in newborns and young infants, sounds with widely distributed spectral energy, such as noise and various environmental sounds, as well as sounds widely deviating from their context elicit an event related potential (ERP similar to the adult P3a response. We discuss how the maturation of event-related potentials parallels the process of the development of passive auditory attention during the first year of life. Behavioural studies have indicated that the neonatal orientation to high energy stimuli gradually changes to attending to genuine novelty and other significant events by approximately 9 months of age. In accordance with these changes, in newborns, the ERP response to large acoustic deviance is dramatically larger than that to small and moderate deviations. This ERP difference, however, rapidly decreases within first months of life and the differentiation of the ERP response to genuine novelty from that to spectrally rich but repeatedly presented sounds commences during the same period. The relative decrease of the response amplitudes elicited by high energy stimuli may reflect development of an inhibitory brain network suppressing the processing of uninformative stimuli. Based on data obtained from healthy full term and pre term infants as well as from infants at risk for various developmental problems, we suggest that the electrophysiological indices of the processing of acoustic and contextual deviance may be indicative of the functioning of auditory attention, a crucial prerequisite of learning and language development.
DEFF Research Database (Denmark)
Olsen, Stig Irving; Bonou, Alexandra
2012-01-01
The core of the EU FP7 funded project W2Plastic is development of a magnetic density separation (MDS) of polyolefines in order to improve the sorting efficiency of these polymer types in different waste fractions. As part of the project a life cycle assessment is performed in order to firstly...... identify eco-design criteria for the development and secondly to document the potential environmental improvement of polyolefin recycling using the MDS technology. A preliminary study focusing solely on the carbon footprint benefits of recycling plastic waste compared to virgin production of polymers...
Song, Young-Joo; Lee, Donghun; Jin, Ho; Kim, Bang-Yeop
2017-01-01
Potential impact trajectories for a lunar CubeSat impactor mission are designed and analyzed under the condition that only a small delta-V from the mechanical separation mechanism from the mother-ship is available. The orbit of the mother-ship from which the CubeSat is deployed is assumed to be a Highly Elliptical Polar Orbit (HEPO) around the Moon, and candidate peri- and aposelene altitudes are investigated. The resultant trajectory parameters for the CubeSat impactor are also analyzed. The impact footprint dispersion characteristics are roughly estimated considering the uncertainties that may arise at the moment of CubeSat deployment. As a result, a set of HEPO shapes that can successfully impact the lunar surface using a deployment delta-V of only 2 m/s is discovered. The delta-V required to separate the CubeSat, which is up to tens of m/s, can be greatly reduced depending on the geometry between the Earth and the orientation of the HEPO of the mother-ship at the moment of deployment. The dispersion characteristics of the impact footprint are more sensitive to the uncertainties in the velocity than in the position at the time of separation. From the point of view of the current proposed trajectory design, an uncertainty of less than several tens of cm/s in the velocity should be guaranteed for successful impact within a radius of several tens of kilometers of the target.
Directory of Open Access Journals (Sweden)
Matthew Sykes
2016-10-01
Full Text Available Repetitive transcranial magnetic stimulation (rTMS is primarily used in humans to change the state of corticospinal excitability. To assess the efficacy of different rTMS stimulation protocols, motor evoked potentials (MEPs are used as a readout due to their non-invasive nature. Stimulation of the motor cortex produces a response in a targeted muscle, and the amplitude of this twitch provides an indirect measure of the current state of the cortex. When applied to the motor cortex, rTMS can alter MEP amplitude, however results are variable between participants and across studies. In addition, the mechanisms underlying any change and its locus are poorly understood. In order to better understand these effects, MEPs have been investigated in vivo in animal models, primarily in rats. One major difference in protocols between rats and humans is the use of general anesthesia in animal experiments. Anesthetics are known to affect plasticity-like mechanisms and so may contaminate the effects of an rTMS protocol. In the present study, we explored the effect of anesthetic on MEP amplitude, recorded before and after intermittent theta burst stimulation (iTBS, a patterned rTMS protocol with reported facilitatory effects. MEPs were assessed in the brachioradialis muscle of the upper forelimb under two anesthetics: a xylazine/zoletil combination and urethane. We found MEPs could be induced under both anesthetics, with no differences in the resting motor threshold or the average baseline amplitudes. However, MEPs were highly variable between animals under both anesthetics, with the xylazine/zoletil combination showing higher variability and most prominently a rise in amplitude across the baseline recording period. Interestingly, application of iTBS did not facilitate MEP amplitude under either anesthetic condition. Although it is important to underpin human application of TMS with mechanistic examination of effects in animals, caution must be taken when
Das, Sushanta K; Mahler, Andrew; Wilson, Angela K; D'Souza, Francis
2014-08-25
High oxidation potential perfluorinated zinc phthalocyanines (ZnF(n)Pcs) are synthesised and their spectroscopic, redox, and light-induced electron-transfer properties investigated systematically by forming donor-acceptor dyads through metal-ligand axial coordination of fullerene (C60) derivatives. Absorption and fluorescence spectral studies reveal efficient binding of the pyridine- (Py) and phenylimidazole-functionalised fullerene (C60Im) derivatives to the zinc centre of the F(n)Pcs. The determined binding constants, K, in o-dichlorobenzene for the 1:1 complexes are in the order of 10(4) to 10(5) M(-1); nearly an order of magnitude higher than that observed for the dyad formed from zinc phthalocyanine (ZnPc) lacking fluorine substituents. The geometry and electronic structure of the dyads are determined by using the B3LYP/6-31G* method. The HOMO and LUMO levels are located on the Pc and C60 entities, respectively; this suggests the formation of ZnF(n)Pc(.+)-C60Im(.-) and ZnF(n)Pc(.+)-C60Py(.-) (n=0, 8 or 16) intra-supramolecular charge-separated states during electron transfer. Electrochemical studies on the ZnPc-C60 dyads enable accurate determination of their oxidation and reduction potentials and the energy of the charge-separated states. The energy of the charge-separated state for dyads composed of ZnF(n)Pc is higher than that of normal ZnPc-C60 dyads and reveals their significance in harvesting higher amounts of light energy. Evidence for charge separation in the dyads is secured from femtosecond transient absorption studies in nonpolar toluene. Kinetic evaluation of the cation and anion radical ion peaks reveals ultrafast charge separation and charge recombination in dyads composed of perfluorinated phthalocyanine and fullerene; this implies their significance in solar-energy harvesting and optoelectronic device building applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Energy Technology Data Exchange (ETDEWEB)
Kieffer, F.
1994-02-01
Geraghty & Miller, Inc. of Midland, Texas conducted geologic and hydrologic feasibility studies of the potential applicability of Jack McIntyre`s patented process for the recovery of natural gas from coalbed/sand formations in the Piceance Basin through literature surveys. Jack McIntyre`s tool separates produced water from gas and disposes of the water downhole into aquifers unused because of poor water quality, uneconomic lifting costs or poor aquifer deliverability. The beneficial aspects of this technology are two fold. The process increases the potential for recovering previously uneconomic gas resources by reducing produced water lifting, treatment and disposal costs. Of greater importance is the advantage of lessening the environmental impact of produced water by downhole disposal. Results from the survey indicate that research in the Piceance Basin includes studies of the geologic, hydrogeologic, conventional and unconventional recovery oil and gas technologies. Available information is mostly found centered upon the geology and hydrology for the Paleozoic and Mesozoic sediments. Lesser information is available on production technology because of the limited number of wells currently producing in the basin. Limited information is available on the baseline geochemistry of the coal/sand formation waters and that of the potential disposal zones. No determination was made of the compatibility of these waters. The study also indicates that water is often produced in variable quantities with gas from several gas productive formations which would indicate that there are potential applications for Jack McIntyre`s patented tool in the Piceance Basin.
Fangueiro, David; Pereira, José; Bichana, André; Surgy, Sónia; Cabral, Fernanda; Coutinho, João
2015-10-01
Cattle-slurry (liquid manure) application to soil is a common practice to provide nutrients and organic matter for crop growth but it also strongly impacts the environment. The objective of the present study was to assess the efficiency of cattle-slurry treatment by solid-liquid separation and/or acidification on nitrogen dynamics and global warming potential (GWP) following application to an acidic soil. An aerobic laboratory incubation was performed over 92 days with a Dystric Cambisol amended with raw cattle-slurry or separated liquid fraction (LF) treated or not by acidification to pH 5.5 by addition of sulphuric acid. Soil mineral N contents and NH3, N2O, CH4 and CO2 emissions were measured. Results obtained suggest that the acidification of raw cattle-slurry reduced significantly NH3 emissions (-88%) but also the GWP (-28%) while increased the N availability relative to raw cattle-slurry (15% of organic N applied mineralised against negative mineralisation in raw slurry). However, similar NH3 emissions and GWP were observed in acidified LF and non-acidified LF treatments. On the other hand, soil application of acidified cattle-slurry rather than non-acidified LF should be preferred attending the lower costs associated to acidification compared to solid-liquid separation. It can then be concluded that cattle-slurry acidification is a solution to minimise NH3 emissions from amended soil and an efficient strategy to decrease the GWP associated with slurry application to soil. Furthermore, the more intense N mineralisation observed with acidified slurry should lead to a higher amount of plant available N and consequently to higher crop yields.
Rine, J.M.; Berg, R.C.; Shafer, J.M.; Covington, E.R.; Reed, J.K.; Bennett, C.B.; Trudnak, J.E.
1998-01-01
A methodology was developed to evaluate and map the contamination potential or aquifer sensitivity of the upper groundwater flow system of a portion of the General Separations Area (GSA) at the Department of Energy's Savannah River Site (SRS) in South Carolina. A Geographic Information System (GIS) was used to integrate diverse subsurface geologic data, soils data, and hydrology utilizing a stack-unit mapping approach to construct mapping layers. This is the first time that such an approach has been used to delineate the hydrogeology of a coastal plain environment. Unit surface elevation maps were constructed for the tops of six Tertiary units derived from over 200 boring logs. Thickness or isopach maps were created for five hydrogeologic units by differencing top and basal surface elevations. The geologic stack-unit map was created by stacking the five isopach maps and adding codes for each stack-unit polygon. Stacked-units were rated according to their hydrogeologic properties and ranked using a logarithmic approach (utility theory) to establish a contamination potential index. Colors were assigned to help display relative importance of stacked-units in preventing or promoting transport of contaminants. The sensitivity assessment included the effects of surface soils on contaminants which are particularly important for evaluating potential effects from surface spills. Hydrogeologic/hydrologic factors did not exhibit sufficient spatial variation to warrant incorporation into contamination potential assessment. Development of this contamination potential mapping system provides a useful tool for site planners, environmental scientists, and regulatory agencies.A methodology was developed to evaluate and map the contamination potential or aquifer sensitivity of the upper groundwater flow system of a portion of the General Separations Area (GSA) at the Department of Energy's Savannah River Site (SRS) in South Carolina. A Geographic Information System (GIS) was used to
Sousa, Vasco C; Vital, Joana; Costenla, Ana Rita; Batalha, Vânia L; Sebastião, Ana M; Ribeiro, Joaquim A; Lopes, Luísa V
2014-07-01
Exposure to chronic stress during the neonatal period is known to induce permanent long-term changes in the central nervous system and hipothalamic-pituitary-adrenal axis reactivity that are associated with increased levels of depression, anxiety, and cognitive impairments. In rodents, a validated model of early life stress is the maternal separation (MS) paradigm, which has been shown to have long-term consequences for the pups that span to adulthood. We hypothesized that the early life stress-associated effects could be exacerbated with aging, because it is often accompanied by cognitive decline. Using a MS model in which rat pups were separated from their mothers for 3 hours daily, during postnatal days 2-14, we evaluated the long-term functional consequences to aged animals (70-week-old), by measuring synaptic plasticity and cognitive performance. The baseline behavioral deficits of aged control rats were further exacerbated in MS animals, indicating that early-life stress induces sustained changes in anxiety-like behavior and hippocampal-dependent memory that are maintained much later in life. We then investigated whether these differences are linked to impaired function of hippocampal neurons by recording hippocampal long-term potentiation from Schaffer collaterals/CA1 synapses. The magnitude of the hippocampal long-term potentiation induced by high-frequency stimulation was significantly lower in aged MS animals than in age-matched controls. These results substantiate the hypothesis that the neuronal and endocrine alterations induced by early-life stress are long lasting, and are able to exacerbate the mild age-associated deficits. Copyright © 2014 Elsevier Inc. All rights reserved.
Particles versus fields in $\\mathcal{PT}$-symmetrically deformed integrable systems
Indian Academy of Sciences (India)
Andreas Fring
2009-08-01
We review some recent results on how $\\mathcal{PT}$ symmetry, that is a simultaneous time-reversal and parity transformation, can be used to construct new integrable models. Some complex valued multi-particle systems, such as deformations of the Calogero–Moser– Sutherland models, are shown to arise naturally from real valued field equations of non-linear integrable systems. Deformations of complex non-linear integrable field equations, some of them even allowing for compacton solutions, are also investigated. The integrabilty of various systems is established by means of the Painlevé test.
Problem of the coexistence of several non-Hermitian observables in PT -symmetric quantum mechanics
Znojil, Miloslav; Semorádová, Iveta; RÅ¯žička, František; Moulla, Hafida; Leghrib, Ilhem
2017-04-01
During recent developments in quantum theory it has been clarified that observable quantities (such as energy and position) may be represented by operators Λ (with real spectra) that are manifestly non-Hermitian in a preselected friendly Hilbert space H(F ). The consistency of these models is known to require an upgrade of the inner product, i.e., mathematically speaking, a transition H(F )→H(S ) to another, standard, Hilbert space. We prove that whenever we are given more than one candidate for an observable (i.e., say, two operators Λ0 and Λ1) in advance, such an upgrade need not exist in general.
Four-wave mixing in a parity-time (PT)-symmetric coupler.
Wasak, T; Szańkowski, P; Konotop, V V; Trippenbach, M
2015-11-15
Parity-time (PT) symmetry allows for implementing controllable matching conditions for the four-wave mixing in 1D coupled waveguides. Different types of the process involving energy transition between slow and fast modes are established. In the case of defocusing Kerr media, the degenerated four-wave mixing is studied in detail. It is shown that unbroken PT symmetry supports the process existing in the conservative limit and, at the same time, originates new types of matching conditions, which cannot exist in the conservative system. In the former case, a slow beam splits into two fast beams, with nearly conserved total power, while in the latter case, one slow beam and one fast beam are generated. In the last process, the energy of the input primary slow beam is not changed and growth of the energy of the generated slow beam varies due to gain and loss of the medium. The appreciable generation of the fifth mode, i.e., the effect of the secondary resonant interactions, is observed.
Nonlinear localized modes in PT-symmetric optical media with competing gain and loss
Midya, Bikashkali
2014-01-01
The existence and stability of the nonlinear spatial localized modes are investigated in parity-time symmetric optical media characterized by a generic complex hyperbolic refractive index distribution with competing gain and loss profile. The exact analytical expressions of the localized modes are found for all values of the competing parameter and in the presence of both the self-focusing and self-defocusing Kerr nonlinearity. The effect of competing gain/loss profile on the stability structure of these localized modes are discussed with the help of linear stability analysis followed by the direct numerical simulation of the governing equation. The spatial localized modes in two-dimensional geometry as well as the transverse power-flow density associated with these localized modes are also examined.
Discrete solitons in self-defocusing systems with $\\mathcal{PT}$-symmetric defects
Chen, Zhiqiang; Chai, Jinglei; Zhang, Xiangyu; Li, Yongyao; Malomed, Boris A
2015-01-01
We construct families of discrete solitons (DSs) in an array of self-defocusing waveguides with an embedded $\\mathcal{PT}$ (parity-time)-symmetric dimer, which is represented by a pair of waveguides carrying mutually balanced gain and loss. Four types of states attached to the embedded defect are found, namely, staggered and unstaggered bright localized modes and gray or anti-gray DSs. Their existence and stability regions expand with the increase of the strength of the coupling between the dimer-forming sites. The existence of the gray and staggered bright DSs is qualitatively explained by dint of the continuum limit. All the gray and anti-gray DSs are stable (some of them are unstable if the dimer carries the nonlinear $\\mathcal{PT}$ symmetry, represented by balanced nonlinear gain and loss; in that case, the instability does not lead to a blowup, but rather creates oscillatory dynamical states). The boundary between the gray and anti-gray DSs is predicted in an approximate analytical form.
Eberhardt, Thomas L; Lebow, Stan; Reed, Karen G
2012-02-01
A cellulose solvent system based on lithium chloride (LiCl) in N-methyl-2-pyrrolidinone (NMP) was used to assess the merits of partial dissolutions of coarsely ground wood samples. Alkaline Copper Quaternary (ACQ)-treated pine wood was of particular interest for treatment given the potential to generate a copper-rich stream apart from solid and/or liquid lignocellulosic feedstocks. Treatment with NMP alone gave yields of soluble materials that were higher than typical extractives contents thereby suggesting a limited degree of wood dissolution. Inclusion of LiCl, which disrupts hydrogen bonding, gave lower wood residue recoveries (i.e., higher dissolution) with higher LiCl concentration. Lower wood residue recoveries coincided with lower Klason lignin and hemicellulose-derived sugar contents in the wood residues. After treatment with 8% LiCl in NMP, subsequent filtration afforded 34% of the ACQ-treated sapwood as a wood residue retaining only 2% of the original copper. Pouring the filtrate over an excess of water resulted in the recovery of 30% of the solids and 50% of the copper together as a copper-enriched lignocellulosic precipitate. Results demonstrate a solvent system showing potential as a means to separate heavy metals from preservative-treated wood and to recover lignocellulosic feedstocks that may be suitable for use in a biorefinery. Published by Elsevier Ltd.
Energy Technology Data Exchange (ETDEWEB)
Kaspar, Tiffany C. [Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99354 USA; Schreiber, Daniel K. [Energy and Environment Directorate, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99354 USA; Spurgeon, Steven R. [Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99354 USA; McBriarty, Martin E. [Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99354 USA; Carroll, Gerard M. [Department of Chemistry, University of Washington, P.O. Box 1700 Seattle WA 98195-1700 USA; Gamelin, Daniel R. [Department of Chemistry, University of Washington, P.O. Box 1700 Seattle WA 98195-1700 USA; Chambers, Scott A. [Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999 Richland WA 99354 USA
2015-12-17
We demonstrate that the different surface terminations exhibited by α-Fe2O3 (hematite) and α-Cr2O3 (eskolaite) in superlattices (SL) of these materials, synthesized with exquisite control by molecular beam epitaxy, determine the heterojunction interface structure and result in controllable, non-commutative band offset values. Precise atomic control of the interface structure allowed us to vary the valence band offset from 0.35 eV to 0.79 eV. This controllable band alignment can be harnessed to generate a built-in potential in Fe2O3-Cr2O3 SLs. For instance, in a 2.5-period SL, a built-in potential of 0.8 eV was realized as measured by x-ray photoelectron spectroscopy of Ti dopants as probe species. The high quality of the SL structure was confirmed by atom probe tomography and scanning transmission electron microscopy. Enhanced photocurrents were measured for a thick Fe2O3 epitaxial film capped with an (Fe2O3)3-(Cr2O3)3 SL; this enhancement was attributed to efficient electron-hole separation in the SL as a result of the band alignment. The Fe-O-Cr bonds at the SL interfaces also red-shifted the onset of photoconductivity to ~1.6 eV. Exploiting the band alignment and photoabsorption properties of Fe2O3-Cr2O3 SLs has the potential to increase the efficiency of hematite-based photoelectrochemical water splitting.
Jarret, Guillaume; Martinez, José; Dourmad, Jean-Yves
2011-11-01
In the guideline for the determination of methane (CH 4) emission from animal manure (IPCC) the amount of CH 4 emitted is generally calculated according to an equation combining the amount of organic matter (OM) or volatile solids excreted, the ultimate CH 4 potential ( B0) of excreta and a system-specific methane conversion factor (MCF, %) that reflects the portion of B0 that is really converted into CH 4. The objective of the present study was to investigate the effect of the modification of dietary crude protein and fibre levels on B0 of pig slurry and on subsequent MCF according to different strategies of slurry management. Five experimental diets differing mainly in their crude protein and fibre content were compared. Two types of measurement of CH 4 emission were performed. The first was the measurement of B0 of slurry using biomethanogene potential (BMP) test. The second consisted in a storage simulation, which was performed on different kinds of effluents: fresh slurry (FSl), stored slurry (SSl), and faeces mixed with water (FaW). The type of diet and the type of effluent affected ( P dietary treatments whereas it differed for storage simulation studies with significant effects of dietary CP and fibre contents. The results from this study indicate that the type of diet has a significant but rather limited effect on B0 value of effluent. The effect of diet is much more marked on MCF, with lower values for high protein diets, and higher values for high fibre diets. MCF is also affected by manure management, the values measured on separated faeces from urine being much higher than for slurry.
Naroznova, Irina; Møller, Jacob; Scheutz, Charlotte
2016-12-01
This study compared the environmental profiles of anaerobic digestion (AD) and incineration, in relation to global warming potential (GWP), for treating individual material fractions that may occur in source-separated organic household waste (SSOHW). Different framework conditions representative for the European Union member countries were considered. For AD, biogas utilisation with a biogas engine was considered and two potential situations investigated - biogas combustion with (1) combined heat and power production (CHP) and (2) electricity production only. For incineration, four technology options currently available in Europe were covered: (1) an average incinerator with CHP production, (2) an average incinerator with mainly electricity production, (3) an average incinerator with mainly heat production and (4) a state-of-the art incinerator with CHP working at high energy recovery efficiencies. The study was performed using a life cycle assessment in its consequential approach. Furthermore, the role of waste-sorting guidelines (defined by the material fractions allowed for SSOHW) in relation to GWP of treating overall SSOHW with AD was investigated. A case-study of treating 1tonne of SSOHW under framework conditions in Denmark was conducted. Under the given assumptions, vegetable food waste was the only material fraction which was always better for AD compared to incineration. For animal food waste, kitchen tissue, vegetation waste and dirty paper, AD utilisation was better unless it was compared to a highly efficient incinerator. Material fractions such as moulded fibres and dirty cardboard were attractive for AD, albeit only when AD with CHP and incineration with mainly heat production were compared. Animal straw, in contrast, was always better to incinerate. Considering the total amounts of individual material fractions in waste generated within households in Denmark, food waste (both animal and vegetable derived) and kitchen tissue are the main material
Shin, S Y; Han, S H; Woo, R-S; Jang, S H; Min, S S
2016-03-01
Exposure to maternal separation (MS) during early life is an identified risk factor for emotional disorders such as anxiety and depression later in life. This study investigated the effects of neonatal MS on the behavior and long-term potentiation (LTP) as well as basic synaptic transmission at hippocampal CA3-CA1 and mossy fiber (MF)-CA3 synapses in adolescent mice for 19days. When mice were adolescents, we measured depression, learning, memory, anxious and aggressive behavior using the forced swimming test (FST), Y-maze, Morris water maze (MWM), elevated plus maze (EPM), three consecutive days of the open field test, the social interaction test, the tube-dominance test and the resident-intruder test. The results showed that there was no difference in FST, Y-maze, and MWM performance. However, MS mice showed more anxiety-like behavior in the EPM test and aggressive-like behavior in the tube-dominance and resident-intruder tests. In addition, the magnitude of LTP and release probability in the MF-CA3 synapses was reduced in the MS group but not in the CA3-CA1 synapse. Our results indicate that early life stress due to MS may induce anxiety- and aggressive-like behavior during adolescence, and these effects are associated with synaptic plasticity at the hippocampal MF-CA3 synapses.
de Oliveira Moraes, Anelize; Ramirez, Ninoska Isabel Bojorge; Pereira, Nei
2016-12-01
Lactic acid is widely used in chemical, pharmaceutical, cosmetic, and food industries, besides it is the building block to produce polylactic acid, which is a sustainable alternative biopolymer to synthetic plastic due to its biodegradability. Aiming at producing an optically pure isomer, the present work evaluated the potential of pulp mill residue as feedstock to produce D(-)-lactic acid by a strain of the bacterium Lactobacillus coryniformis subsp. torquens using separate hydrolysis and fermentation process. Enzymatic hydrolysis, optimized through response surface methodology for 1 g:4 mL solid/liquid ratio and 24.8 FPU/gcellulose enzyme loading, resulted in 140 g L(-1) total reducing sugar and 110 g L(-1) glucose after 48 h, leading to 61 % of efficiency. In instrumented bioreactor, 57 g L(-1) of D(-)-lactic acid was achieved in 20 h of fermentation, while only 0.5 g L(-1) of L(+)-lactic acid was generated. Furthermore, product yield of 0.97 g/g and volumetric productivity of 2.8 g L(-1) h(-1) were obtained.
Hesse, Michael; Birn, Joachim; Schindler, Karl
1990-01-01
A self-consistent two-fluid theory that includes the magnetic field and shear patterns is developed to model stationary electrostatic structures with field-aligned potential drops. Shear flow is also included in the theory since this seems to be a prominent feature of the structures of interest. In addition, Ohmic dissipation, a Hall term, and pressure gradients in a generalized Ohm's law, modified for cases without quasi-neutrality, are included. In the analytic theory, the electrostatic force is balanced by field-aligned pressure gradients (i.e., thermal effects in the direction of the magnetic field) and by pressure gradients and magnetic stresses in the perpendicular direction. Within this theory, simple examples of applications are presented to demonstrate the kind of solutions resulting from the model. The results show how the effects of charge separation and shear in the magnetic field and the velocity can be combined to form self-consistent structures such as are found to exist above the aurora, suggested also in association with solar flares.
DEFF Research Database (Denmark)
Reynolds, John C.
2002-01-01
expressions) for accessing and modifying shared structures, and for explicit allocation and deallocation of storage. Assertions are extended by introducing a "separating conjunction" that asserts that its sub-formulas hold for disjoint parts of the heap, and a closely related "separating implication". Coupled......, dynamically allocated arrays, and recursive procedures. We will also discuss promising future directions....
Chen, Yong; Yan, Zhenya
2017-01-01
The effect of derivative nonlinearity and parity-time-symmetric (PT -symmetric) potentials on the wave propagation dynamics is explored in the derivative nonlinear Schrödinger equation, where the physically interesting Scarf-II and harmonic-Hermite-Gaussian potentials are chosen. We study numerically the regions of unbroken and broken linear PT -symmetric phases and find some stable bright solitons of this model in a wide range of potential parameters even though the corresponding linear PT -symmetric phases are broken. The semielastic interactions between particular bright solitons and exotic incident waves are illustrated such that we find that particular nonlinear modes almost keep their shapes after interactions even if the exotic incident waves have evidently been changed. Moreover, we exert the adiabatic switching on PT -symmetric potential parameters such that a stable nonlinear mode with the unbroken linear PT -symmetric phase can be excited to another stable nonlinear mode belonging to the broken linear PT -symmetric phase.
Laux, Patrick; Nguyen, Phuong N. B.; Cullmann, Johannes; Kunstmann, Harald
2016-04-01
Regional climate models (RCMs) comprise both terrestrial and atmospheric compartments and thereby allowing to study land atmosphere feedbacks, and in particular the land-use and climate change impacts. In this study, a methodological framework is developed to separate the land use change induced signals in RCM simulations from noise caused by perturbed initial boundary conditions. The framework is applied for two different case studies in SE Asia, i.e. an urbanization and a deforestation scenario, which are implemented into the Weather Research and Forecasting (WRF) model. The urbanization scenario is produced for Da Nang, one of the fastest growing cities in Central Vietnam, by converting the land-use in a 20 km, 14 km, and 9 km radius around the Da Nang meteorological station systematically from cropland to urban. Likewise, three deforestation scenarios are derived for Nong Son (Central Vietnam). Based on WRF ensemble simulations with perturbed initial conditions for 2010, the signal to-noise ratio (SNR) is calculated to identify areas with pronounced signals induced by LULCC. While clear and significant signals are found for air temperature, latent and sensible heat flux in the urbanization scenario (SNR values up to 24), the signals are not pronounced for deforestation (SNR values < 1). Albeit statistically significant signals are found for precipitation, low SNR values hinder scientifically sound inferences for climate change adaptation options. It is demonstrated that ensemble simulations with more than at least 5 ensemble members are required to derive robust LULCC adaptation strategies, particularly if precipitation is considered. This is rarely done in practice, thus potentially leading to erroneous estimates of the LULCC induced signals of water and energy fluxes, which are propagated through the regional climate - hydrological model modeling chains, and finally leading to unfavorable decision support.
Energy Technology Data Exchange (ETDEWEB)
Jeong, Hyun-Seok; Choi, Eun-Sun [Department of Chemical Engineering, Kangwon National University, Chuncheon, Kangwondo, 200-701 (Korea, Republic of); Kim, Jong Hun [Batteries R and D, LG Chem, Yusong-gu, Daejon, 305-380 (Korea, Republic of); Lee, Sang-Young, E-mail: syleek@kangwon.ac.kr [Department of Chemical Engineering, Kangwon National University, Chuncheon, Kangwondo, 200-701 (Korea, Republic of)
2011-05-30
Highlights: > Microporous-structured PVdF-HFP/PET composite nonwoven separators for Li-batteries. > Well-developed microporous structure and liquid electrolyte wettability. > Provision of facile ion transport and suppressed growth of cell impedance. > Superior cell performance at high-voltages/high-current densities. - Abstract: We demonstrate potential application of a new composite non-woven separator, which is comprised of a phase inversion-controlled, microporous polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) gel polymer electrolyte and a polyethylene terephthalate (PET) non-woven support, to high-voltage and high-power lithium-ion batteries. In comparison to a commercialized polyethylene (PE) separator, the composite non-woven separator exhibits distinct improvements in microporous structure and liquid electrolyte wettability. Based on the understanding of the composite non-woven separator, cell performances of the separator at challenging charge/discharge conditions are investigated and discussed in terms of ion transport of the separator and AC impedance of the cell. The aforementioned advantageous features of the composite non-woven separator play a key role in providing facile ion transport and suppressing growth of cell impedance during cycling, which in turn contribute to superior cell performances at harsh charge/discharge conditions such as high voltages and high current densities.
Skarstrom, C.
1959-03-10
A centrifugal separator is described for separating gaseous mixtures where the temperature gradients both longitudinally and radially of the centrifuge may be controlled effectively to produce a maximum separation of the process gases flowing through. Tbe invention provides for the balancing of increases and decreases in temperature in various zones of the centrifuge chamber as the result of compression and expansions respectively, of process gases and may be employed effectively both to neutralize harmful temperature gradients and to utilize beneficial temperaturc gradients within the centrifuge.
Spiral microfluidic nanoparticle separators
Bhagat, Ali Asgar S.; Kuntaegowdanahalli, Sathyakumar S.; Dionysiou, Dionysios D.; Papautsky, Ian
2008-02-01
Nanoparticles have potential applications in many areas such as consumer products, health care, electronics, energy and other industries. As the use of nanoparticles in manufacturing increases, we anticipate a growing need to detect and measure particles of nanometer scale dimensions in fluids to control emissions of possible toxic nanoparticles. At present most particle separation techniques are based on membrane assisted filtering schemes. Unfortunately their efficiency is limited by the membrane pore size, making them inefficient for separating a wide range of sizes. In this paper, we propose a passive spiral microfluidic geometry for momentum-based particle separations. The proposed design is versatile and is capable of separating particulate mixtures over a wide dynamic range and we expect it will enable a variety of environmental, medical, or manufacturing applications that involve rapid separation of nanoparticles in real-world samples with a wide range of particle components.
Ploegmakers, J.; Jelsma, A.R.T.; Ham, van der A.G.J.; Nijmeijer, D.C.
2013-01-01
Since ethylene/ethane separation by cryogenic distillation is one of the most energy intensive processes, it can be economically interesting to combine it with energy efficient membrane technology. The effect on the viability of different process configurations in relation to the ethylene permeance
DEFF Research Database (Denmark)
Olsen, Stig Irving; Bonou, Alexandra
2012-01-01
The core of the EU FP7 funded project W2Plastic is development of a magnetic density separation (MDS) of polyolefines in order to improve the sorting efficiency of these polymer types in different waste fractions. As part of the project a life cycle assessment is performed in order to firstly...
2016-01-01
Footage of the 70 degree ISOLDE GPS separator magnet MAG70 as well as the switchyard for the Central Mass and GLM (GPS Low Mass) and GHM (GPS High Mass) beamlines in the GPS separator zone. In the GPS20 vacuum sector equipment such as the long GPS scanner 482 / 483 unit, faraday cup FC 490, vacuum valves and wiregrid piston WG210 and WG475 and radiation monitors can also be seen. Also the RILIS laser guidance and trajectory can be seen, the GPS main beamgate switch box and the actual GLM, GHM and Central Beamline beamgates in the beamlines as well as the first electrostatic quadrupoles for the GPS lines. Close up of the GHM deflector plates motor and connections and the inspection glass at the GHM side of the switchyard.
2016-01-01
Footage of the 90 and 60 degree ISOLDE HRS separator magnets in the HRS separator zone. In the two vacuum sectors HRS20 and HRS30 equipment such as the HRS slits SL240, the HRS faraday cup FC300 and wiregrid WG210 can be spotted. Vacuum valves, turbo pumps, beamlines, quadrupoles, water and compressed air connections, DC and signal cabling can be seen throughout the video. The HRS main and user beamgate in the beamline between MAG90 and MAG60 and its switchboxes as well as all vacuum bellows and flanges are shown. Instrumentation such as the HRS scanner unit 482 / 483, the HRS WG470 wiregrid and slits piston can be seen. The different quadrupoles and supports are shown as well as the RILIS guidance tubes and installation at the magnets and the different radiation monitors.
Szilágyi, Petra Ágota; Lutz, Martin; Gascon, Jorge; Juan-Alcaniz, Jana; van Esch, Jan; Kapteijn, Freek; Geerlings, Hans; Dam, Bernard; van de Krol, Roel
2013-01-01
The effect of strain on core–shell MOFcore@MOFshell particles is discussed and compared with that observed for analogous Janus particles. Whereas Janus particles do not display any effect of strain, the core of fully coated core–shell particles collapsed upon the formation of the outer shell, leaving the core inaccessible for guest adsorption. This suggests that Janus particles might become ideal candidates for gas separation, while core–shell particles could play a key role in sequestration ...
Sewvandi, Galhenage A.; Hu, Dengwei; Chen, Changdong; Ma, Hao; Kusunose, Takafumi; Tanaka, Yasuhiro; Nakanishi, Shunsuke; Feng, Qi
2016-08-01
Perovskite solar cells (PSCs) often suffer from large performance variations which impede to define a clear charge-transfer mechanism. Ferroelectric polarization is measured numerically using CH3NH3PbI3 (M A PbI3 ) pellets to overcome the measurement issues such as pinholes and low uniformity of thickness, etc., with M A PbI3 thin films. M A PbI3 perovskite is an antiferroelectric semiconductor which is different from typical semiconducting materials and ferroelectric materials. The effect of polarization carrier separation on the charge-transfer mechanism in the PSCs is elucidated by using the results of ferroelectric and structural studies on the perovskite. The ferroelectric polarization contributes to an inherent carrier-separation effect and the I - V hysteresis. The ferroelectric and semiconducting synergistic charge-separation effect gives an alternative category of solar cells, ferroelectric semiconductor solar cells. Our findings identify the ferroelectric semiconducting behavior of the perovskite absorber as being significant to the improvement of the ferroelectric PSCs performances in future developments.
Plasma separation: physical separation at the molecular level
Gueroult, Renaud; Rax, Jean-Marcel; Fisch, Nathaniel J.
2016-09-01
Separation techniques are usually divided in two categories depending on the nature of the discriminating property: chemical or physical. Further to this difference, physical and chemical techniques differ in that chemical separation typically occurs at the molecular level, while physical separation techniques commonly operate at the macroscopic scale. Separation based on physical properties can in principle be realized at the molecular or even atomic scale by ionizing the mixture. This is in essence plasma based separation. Due to this fundamental difference, plasma based separation stands out from other separation techniques, and features unique properties. In particular, plasma separation allows separating different elements or chemical compounds based on physical properties. This could prove extremely valuable to separate macroscopically homogeneous mixtures made of substances of similar chemical formulation. Yet, the realization of plasma separation techniques' full potential requires identifying and controlling basic mechanisms in complex plasmas which exhibit suitable separation properties. In this paper, we uncover the potential of plasma separation for various applications, and identify the key physics mechanisms upon which hinges the development of these techniques.
Energy Technology Data Exchange (ETDEWEB)
Kroeger, Rhena; Hothan, Andreas; Theuvsen, Ludwig; Broll, Gabriele; Brauckmann, Hans-Joerg; Bronsema, Hauke [Goettingen Univ. (Germany). Dept. fuer Agraroekonomie und Rurale Entwicklung, Betriebswirtschaftslehre des Agribusiness
2013-10-01
The increasing regional concentration of dairy farming requires alternatives for the use of the accruing slurry to defuse the nutrient problem. One possibility is to separate the manure and use the solid fraction for an energetic use in biogas plants in nutrient undersupplied regions. First practical tests on dairy slurry separation have shown that separators are able to achieve a performance 1.3 to 16.6 tons of mass flow per hour. The nutrients are disproportionately deposited in the solid fraction. Furthermore, the solid fractions show a methane building potential that is double as high as the raw slurry methane yield. An energetic use of the solid fraction allows the reduction of other substrates. Thus, it is possible to decrease the land requirements and the costs for other substrates. (orig.)
Pray, A J; Shanker, B
2011-01-01
The state of art of time domain integral equation (TDIE) solvers has grown by leaps and bounds over the past decade. During this time, advances have been made in (i) the development of accelerators that can be retrofitted with these solvers and (ii) understanding the stability properties of the electric field integral equation. As is well known, time domain electric field integral equation solvers have been notoriously difficult to stabilize. Research into methods for understanding and prescribing remedies have been on the uptick. The most recent of these efforts are (i) Lubich quadrature and (ii) exact integration. In this paper, we re-examine the solution to this equation using (i) the undifferentiated form of the TD-EFIE and (ii) a separable approximation to the spatio-temporal convolution. The proposed scheme can be constructed such that the spatial integrand over the source and observer domains is smooth and integrable. As several numerical results will demonstrate, the proposed scheme yields stable resu...
Energy Technology Data Exchange (ETDEWEB)
Rogers, Robin D
2007-06-25
Through the current DoE-BES funding, we have extended our fundamental understanding of the critical phase separation of aqueous polymer solutions at the molecular level, and have developed a similar understanding of their application as novel solvent systems. Our principal aims included mode of delivery of the aqueous biphasic system (ABS) solvent system and the application of this system to problems of reactive extraction. In the former case we have developed novel solid phase analogues, in the form of cross-linked polyethylene glycol hydrogels, and in the latter case we have examined the role that ABS might play in reaction engineering, with a view to greener, simpler, and safer processes. We have also developed a new salt/salt ABS and have extended our understanding of this system as well. The major outcomes are as follows: (1) Through the use of variable temperature phase diagrams, coupled with differential scanning calorimetry (DSC) measurements of the phases, a better understanding of the thermodynamics of phase formation was obtained. Evidence to the existence and role of an upper critical solution temperature (UCST) or lower critical solution temperature (LCST) (or both) in these systems was gained. With variable temperature solute partitioning, thermodynamic parameters were calculated, and inter-system comparisons were made. Through the use of Abraham's linear solvation energy regression (LSER) the solvent-solute properties of liquid/liquid ABS were examined. We have shown that ABS are indeed very tunable and LSERs have been used as a tool to compare these systems to traditional organic/water and other liquid/liquid systems. (2) We have successfully shown the development of novel reaction media for chemical synthesis and reaction; Aqueous Biphasic Reactive Extraction (ABRE). As a proof of concept, we have shown the synthesis of adipic acid from cyclohexene in an ABS, which represents an important development in the exploitation of this technology
Parr, Maria Kristina; Blokland, Marco H.; Liebetrau, Franz; Schmidt, Alexander H.; Meijer, Thijs; Stanic, Mijo; Kwiatkowska, Dorota; Waraksa, Emilia; Sterk, Saskia S.
2017-01-01
The differentiation of clenbuterol abuse and unintentional ingestion from contaminated meat is crucial with respect to the valuation of an adverse analytical finding in human sports doping control. The proportion of the two enantiomers of clenbuterol may serve as potential discriminating parameter.
Han, Tian; Cao, Xueli; Xu, Jing; Pei, Hairun; Zhang, Hong; Tang, Yalin
2017-07-21
G-quadruplex DNA structure is considered to be a very attractive target for antitumor drug design due to its unique role in maintaining telomerase activities. Therefore, discovering ligands with high stability of G-quadruplex structure is of great interest. In this paper, pH-zone refining counter current chromatography (CCC) and preparative high performance liquid chromatography (HPLC) were employed for the separation of potent G-quadruplex ligands from the n-butanol fraction of the crude extract of Zanthoxylum ailanthoides, which is a traditional Chinese medicine recently found to display high inhibitory activity against several human cancer cells. The 75% aqueous ethanol extract of the stem bark of Z. ailanthoides and its fractions with petroleum ether, ethyl acetate and n-butanol displayed almost the same G-quadruplex stabilization ability. Here, pH-zone refining CCC was used for the separation of the alkaloids from the n-butanol fraction by a seldom used solvent system composed of dichloromethane-methanol-water (4:1:2.5) with 10mM TEA in the organic stationary phase as retainer and 10mM HCl in the aqueous mobile phase as eluter. Compounds I, II and III were obtained, with purity greater than 95%, in the quantities of 31.2, 94.0, and 26.4mg respectively from 300mg of lipophilic fraction within 80min, which were identified as three tetrahydroprotoberberines isolated for the first time in this plant. In addition, a phenylpropanoid glycoside compound IV (Syringin), an isoquinoline (Magnoflorine, V), and two lignin isomers (+)-lyoniresiol-3α-O-β-d-glucopyranoside (VI) and (-)-lyoniresinol -3α-O-β-D -glucopyranoside (VII) were isolated by traditional CCC together with preparative HPLC. Compounds IV, V, VI and VII were obtained, with purity greater than 95%, in the quantities of 4.0, 13.2, 6.7, and 6.5mg respectively from 960mg of hydrophilic fraction. Among the seven isolated compounds, tetrahydroprotoberberine I, II and III were found to display remarkable
Sengupta, Arijit; Kadam, R. M.
2017-02-01
A systematic photoluminescence based investigation was carried out to understand the complexation of Eu3 + with different ligands (TBP: tri-n-butyl phosphate, DHOA: di-n-hexyl octanamide, Cyanex 923: tri-n-alkyl phosphine oxide and Cyanex 272: Bis (2,4,4 trimethyl) pentyl phosphinic acid) used for preferential separation of lanthanides and actinides in various stages of nuclear fuel cycle. In case of TBP and DHOA complexes, 3 ligand molecules coordinated in monodentate fashion and 3 nitrate ion in bidentate fashion to Eu3 + to satisfy the 9 coordination of Eu. In case of Cyanex 923 and Cyanex 272 complexes, 3 ligand molecules, 3 nitrate ion and 3 water molecules coordinated to Eu3 + in monodentate fashion. The Eu complexes of TBP and DHOA were found to have D3h local symmetry while that for Cyanex 923 and Cyanex 272 were C3h. Judd-Ofelt analysis of these systems revealed that the covalency of Eusbnd O bond followed the trend DHOA > TBP > Cyanex 272 > Cyanex 923. Different photophysical properties like radiative and non-radiative life time, branching ratio for different transitions, magnetic and electric dipole moment transition probabilities and quantum efficiency were also evaluated and compared for these systems. The magnetic dipole transition probability was found to be almost independent of ligand field perturbation while electric dipole transition probability for 5D0-7F2 transition was found to be hypersensitive with ligand field with a trend DHOA > TBP > Cyanex 272 > Cyanex 923. Supplementary Table 2: Determination of inner sphere water molecules from the different empirical formulae reported in the literature.
Pavan, Márcio G.; Mesquita, Rafael D.; Lawrence, Gena G.; Lazoski, Cristiano; Dotson, Ellen M.; Abubucker, Sahar; Mitreva, Makedonka; Randall-Maher, Jennifer; Monteiro, Fernando A.
2013-01-01
The design and application of rational strategies that rely on accurate species identification are pivotal for effective vector control. When morphological identification of the target vector species is impractical, the use of molecular markers is required. Here we describe a non-coding, single-copy nuclear DNA fragment that contains a single-nucleotide polymorphism (SNP) with the potential to distinguish the important domestic Chagas disease vector, Rhodnius prolixus, from members of the four sylvatic Rhodnius robustus cryptic species complex. A total of 96 primer pairs obtained from whole genome shotgun sequencing of the R. prolixus genome (12,626 random reads) were tested on 43 R. prolixus and R. robustus s.l. samples. One of the seven amplicons selected (AmpG) presented a SNP, potentially diagnostic for R. prolixus, on the 280th site. The diagnostic nature of this SNP was then performed on 154 R. prolixus and R. robustus s.l. samples aimed at achieving the widest possible geographic coverage. The results of a 60% majority rule Bayesian consensus tree and a median-joining network constructed based on the genetic variability observed reveal the paraphyletic nature of the R. robustus species complex, with respect to R. prolixus. AmpG region is located in the fourth intron of the Transmembrane protein 165 gene, which seems to be in the R. prolixus X chromosome. Other possible chromosomal locations of the AmpG region in the R. prolixus genome are also presented and discussed. PMID:23219914
Organic Separation Test Results
Energy Technology Data Exchange (ETDEWEB)
Russell, Renee L.; Rinehart, Donald E.; Peterson, Reid A.
2014-09-22
Separable organics have been defined as “those organic compounds of very limited solubility in the bulk waste and that can form a separate liquid phase or layer” (Smalley and Nguyen 2013), and result from three main solvent extraction processes: U Plant Uranium Recovery Process, B Plant Waste Fractionation Process, and Plutonium Uranium Extraction (PUREX) Process. The primary organic solvents associated with tank solids are TBP, D2EHPA, and NPH. There is concern that, while this organic material is bound to the sludge particles as it is stored in the tanks, waste feed delivery activities, specifically transfer pump and mixer pump operations, could cause the organics to form a separated layer in the tank farms feed tank. Therefore, Washington River Protection Solutions (WRPS) is experimentally evaluating the potential of organic solvents separating from the tank solids (sludge) during waste feed delivery activities, specifically the waste mixing and transfer processes. Given the Hanford Tank Waste Treatment and Immobilization Plant (WTP) waste acceptance criteria per the Waste Feed Acceptance Criteria document (24590-WTP-RPT-MGT-11-014) that there is to be “no visible layer” of separable organics in the waste feed, this would result in the batch being unacceptable to transfer to WTP. This study is of particular importance to WRPS because of these WTP requirements.
Chubykalo, A E; Chubykalo, Andrew E; Smirnov-Rueda, Roman
1995-01-01
The inadequacy of Li\\'{e}nard-Wiechert potentials is demonstrated as one of the examples related to the nonconsistence of the conventional classical electrodynamics. The insufficiency of the Faraday-Maxwell concept to describe the whole electromagnetic phenomena and the incompleteness of a set of solutions of Maxwell equations are discussed and mathematically proved. Reasons of the introduction of the so-called ``electrodynamics dualism concept" (simultaneous coexistence of instantaneous Newton long-range and Faraday-Maxwell short-range interactions) have been displayed. It is strictly shown that the new concept presents itself as the direct consequence of the complete set of Maxwell equations and makes it possible to consider classical electrodynamics as a self-consistent and complete theory, devoid of inward contradictions. In the framework of the new approach, all main concepts of classical electrodynamics are reconsidered. In particular, a limited class of motion is revealed when accelerated charges do no...
Parr, Maria Kristina; Blokland, Marco H; Liebetrau, Franz; Schmidt, Alexander H; Meijer, Thijs; Stanic, Mijo; Kwiatkowska, Dorota; Waraksa, Emilia; Sterk, Saskia S
2017-04-01
The differentiation of clenbuterol abuse and unintentional ingestion from contaminated meat is crucial with respect to the valuation of an adverse analytical finding in human sports doping control. The proportion of the two enantiomers of clenbuterol may serve as potential discriminating parameter. For the determination of the individual enantiomers, specific methods were developed and validated for the different matrices under investigation based on chiral chromatography coupled to tandem mass spectrometry. Data are presented from the administration to humans of clenbuterol from a pharmaceutical preparation, and from cattle meat and liver containing residues. A shift in the proportion of the enantiomers in cattle meat is detected and this signature is also found in human urine after ingestion. Thus, an altered enantiomeric composition of clenbuterol may be used to substantiate athletes' claims following adverse analytical findings in doping control. However, in meat, the enantiomeric composition was found to be highly variable. Species as well as tissue dependent variances need to be considered in interpreting enantiomer discrimination. Analysis of post administration urines from a controlled experiment comparing the administration of racemic clenbuterol from a registered pharmaceutical preparation and the administration of residue-containing meat and liver (nonracemic mixture) from treated animals is reported. Furthermore doping control samples from Mexican U17 World Championship 2011 of the Fédération Internationale de Football Association (FIFA), with adverse analytical findings for clenbuterol, were re-analysed.
Jaimes-Nájera, Alfonso; Rosas-Ortiz, Oscar
2017-01-01
Some general properties of the wave functions of complex-valued potentials with real spectrum are studied. The main results are presented in a series of lemmas, corollaries and theorems that are satisfied by the zeros of the real and imaginary parts of the wave functions on the real line. In particular, it is shown that such zeros interlace so that the corresponding probability densities ρ(x) are never null. We find that the profile of the imaginary part VI(x) of a given complex-valued potential determines the number and distribution of the maxima and minima of the related probability densities. Our conjecture is that VI(x) must be continuous in R, and that its integral over all the real line must be equal to zero in order to get control on the distribution of the maxima and minima of ρ(x) . The applicability of these results is shown by solving the eigenvalue equation of different complex potentials, these last being either PT-symmetric or not invariant under the PT-transformation.
PT symmetry breaking in the presence of random, periodic, long-range hopping
Harter, Andrew K.; Onanga, Franck Assogba; Joglekar, Yogesh N.
2016-09-01
Over the past five years, open systems with balanced gain and loss have been investigated for extraordinary properties that are not shared by their closed counterparts. Non-Hermitian, Parity-Time (PT ) symmetric Hamiltonians faithfully model such systems. Such a Hamiltonian typically consists of a reflection-symmetric, Hermitian, nearest-neighbor hopping profile and a PT-symmetric, non-Hermitian, gain and loss potential, and has a robust PT -symmetric phase. Here we investigate the robustness of this phase in the presence of long-range hopping disorder that is not PT-symmetric, but is periodic. We find that the PT-symmetric phase remains robust in the presence of such disorder, and characterize the configurations where that happens. Our results are found using a tight-binding model, and we validate our predictions through the beam-propagation method.
DEFF Research Database (Denmark)
Jensen, Jonas Buhrkal; Birkedal, Lars
2012-01-01
, separation means physical separation. In this paper, we introduce \\emph{fictional separation logic}, which includes more general forms of fictional separating conjunctions P * Q, where "*" does not require physical separation, but may also be used in situations where the memory resources described by P and Q...
Virus separation using membranes.
Grein, Tanja A; Michalsky, Ronald; Czermak, Peter
2014-01-01
Industrial manufacturing of cell culture-derived viruses or virus-like particles for gene therapy or vaccine production are complex multistep processes. In addition to the bioreactor, such processes require a multitude of downstream unit operations for product separation, concentration, or purification. Similarly, before a biopharmaceutical product can enter the market, removal or inactivation of potential viral contamination has to be demonstrated. Given the complexity of biological solutions and the high standards on composition and purity of biopharmaceuticals, downstream processing is the bottleneck in many biotechnological production trains. Membrane-based filtration can be an economically attractive and efficient technology for virus separation. Viral clearance, for instance, of up to seven orders of magnitude has been reported for state of the art polymeric membranes under best conditions.This chapter summarizes the fundamentals of virus ultrafiltration, diafiltration, or purification with adsorptive membranes. In lieu of an impractical universally applicable protocol for virus filtration, application of these principles is demonstrated with two examples. The chapter provides detailed methods for production, concentration, purification, and removal of a rod-shaped baculovirus (Autographa californica M nucleopolyhedrovirus, about 40 × 300 nm in size, a potential vector for gene therapy, and an industrially important protein expression system) or a spherical parvovirus (minute virus of mice, 22-26 nm in size, a model virus for virus clearance validation studies).
Separation Anxiety (For Parents)
... Kids to Be Smart About Social Media Separation Anxiety KidsHealth > For Parents > Separation Anxiety Print A A ... both of you get through it. About Separation Anxiety Babies adapt pretty well to other caregivers. Parents ...
Separation Anxiety (For Parents)
... Feeding Your 1- to 2-Year-Old Separation Anxiety KidsHealth > For Parents > Separation Anxiety A A A ... both of you get through it. About Separation Anxiety Babies adapt pretty well to other caregivers. Parents ...
Controlling Separation in Turbomachines
Evans, Simon; Himmel, Christoph; Power, Bronwyn; Wakelam, Christian; Xu, Liping; Hynes, Tom; Hodson, Howard
2010-01-01
Four examples of flow control: 1) Passive control of LP turbine blades (Laminar separation control). 2) Aspiration of a conventional axial compressor blade (Turbulent separation control). 3) Compressor blade designed for aspiration (Turbulent separation control). 4.Control of intakes in crosswinds (Turbulent separation control).
Printed Spacecraft Separation System
Energy Technology Data Exchange (ETDEWEB)
Holmans, Walter [Planetary Systems Corporation, Silver Springs, MD (United States); Dehoff, Ryan [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2016-10-01
In this project Planetary Systems Corporation proposed utilizing additive manufacturing (3D printing) to manufacture a titanium spacecraft separation system for commercial and US government customers to realize a 90% reduction in the cost and energy. These savings were demonstrated via “printing-in” many of the parts and sub-assemblies into one part, thus greatly reducing the labor associated with design, procurement, assembly and calibration of mechanisms. Planetary Systems Corporation redesigned several of the components of the separation system based on additive manufacturing principles including geometric flexibility and the ability to fabricate complex designs, ability to combine multiple parts of an assembly into a single component, and the ability to optimize design for specific mechanical property targets. Shock absorption was specifically targeted and requirements were established to attenuate damage to the Lightband system from shock of initiation. Planetary Systems Corporation redesigned components based on these requirements and sent the designs to Oak Ridge National Laboratory to be printed. ORNL printed the parts using the Arcam electron beam melting technology based on the desire for the parts to be fabricated from Ti-6Al-4V based on the weight and mechanical performance of the material. A second set of components was fabricated from stainless steel material on the Renishaw laser powder bed technology due to the improved geometric accuracy, surface finish, and wear resistance of the material. Planetary Systems Corporation evaluated these components and determined that 3D printing is potentially a viable method for achieving significant cost and savings metrics.
Separation anxiety in children
... page: //medlineplus.gov/ency/article/001542.htm Separation anxiety in children To use the sharing features on this page, please enable JavaScript. Separation anxiety in children is a developmental stage in which ...
Ionene membrane battery separator
Moacanin, J.; Tom, H. Y.
1969-01-01
Ionic transport characteristics of ionenes, insoluble membranes from soluble polyelectrolyte compositions, are studied for possible application in a battery separator. Effectiveness of the thin film of separator membrane essentially determines battery lifetime.
Energy Technology Data Exchange (ETDEWEB)
Nath, Pulak; Twary, Scott N.
2016-04-26
Described herein are methods and systems for harvesting, collecting, separating and/or dewatering algae using iron based salts combined with a magnetic field gradient to separate algae from an aqueous solution.
Van Kooy, L.; Mooij, M.; Rem, P.
2004-01-01
Separations by density, such as the separation of non-ferrous scrap into light and heavy alloys, are often realized by means of heavy media. In principle, kinetic gravity separations in water can be faster and cheaper, because they do not rely on suspensions or salt solutions of which the density
Burke, Kenneth Alan; Fisher, Caleb; Newman, Paul
2010-01-01
The main product of a typical fuel cell is water, and many fuel-cell configurations use the flow of excess gases (i.e., gases not consumed by the reaction) to drive the resultant water out of the cell. This two-phase mixture then exits through an exhaust port where the two fluids must again be separated to prevent the fuel cell from flooding and to facilitate the reutilization of both fluids. The Glenn Research Center (GRC) has designed, built, and tested an innovative fuel-cell water separator that not only removes liquid water from a fuel cell s exhaust ports, but does so with no moving parts or other power-consuming components. Instead it employs the potential and kinetic energies already present in the moving exhaust flow. In addition, the geometry of the separator is explicitly intended to be integrated into a fuel-cell stack, providing a direct mate with the fuel cell s existing flow ports. The separator is also fully scalable, allowing it to accommodate a wide range of water removal requirements. Multiple separators can simply be "stacked" in series or parallel to adapt to the water production/removal rate. GRC s separator accomplishes the task of water removal by coupling a high aspect- ratio flow chamber with a highly hydrophilic, polyethersulfone membrane. The hydrophilic membrane readily absorbs and transports the liquid water away from the mixture while simultaneously resisting gas penetration. The expansive flow path maximizes the interaction of the water particles with the membrane while minimizing the overall gas flow restriction. In essence, each fluid takes its corresponding path of least resistance, and the two fluids are effectively separated. The GRC fuel-cell water separator has a broad range of applications, including commercial hydrogen-air fuel cells currently being considered for power generation in automobiles.
Separable metrics and radiating stars
Indian Academy of Sciences (India)
G Z ABEBE; S D MAHARAJ
2017-01-01
We study the junction condition relating the pressure to heat flux at the boundary of an accelerating and expanding spherically symmetric radiating star. We transform the junction condition to an ordinary differential equation by making a separability assumption on the metric functions in the space–time variables. The condition of separability on the metric functions yields several new exact solutions. A class of shear-free models is found which contains a linear equation of state and generalizes a previously obtained model. Four new shearing models are obtained; all the gravitational potentials can be written explicitly. A brief physical analysis indicates that the matter variables are well behaved.
SOFC and Gas Separation Membranes
DEFF Research Database (Denmark)
Hagen, Anke; Hendriksen, Peter Vang; Søgaard, Martin
2009-01-01
from air. Subsequent separation and sequestration of CO2 is therefore easier on a SOFC plant than on conventional power plants based on combustion. Oxide ion conducting materials may be used for gas separation purposes with close to 100 % selectivity. They typically work in the same temperature range...... as SOFCs. Such membranes can potentially be used in Oxyfuel processes as well as in IGCC (Integrated Gasification Combined Cycle) power plants for supply of process oxygen, which may reduce cost of carbon capture and storage as dilution of the flue gas with nitrogen is avoided. Both technologies are very...
Madkour, Tarek M.
2013-08-01
Nano-porous polymers of intrinsic microporosity, PIM, have exhibited excellent permeability and selectivity characteristics that could be utilized in an environmentally friendly gas separation process. A full understanding of the mechanism through which these membranes effectively and selectively allow for the permeation of specific gases will lead to further development of these membranes. Three factors obviously influenced the conformational behavior of these polymers, which are the presence of electronegative atoms, the presence of non-linearity in the polymeric backbones (backbone kinks) and the presence of bulky side groups on the polymeric chains. The dipole moment increased sharply with the presence of backbone kinks more than any other factor. Replacing the fluorine atoms with bulky alkyl groups didn't influence the dipole moment greatly indicating that the size of the side chains had much less dramatic influence on the dipole moment than having a bent backbone. Similarly, the presence of the backbone kinks in the polymeric chains influenced the polymeric chains to assume less extended configuration causing the torsional angles around the interconnecting bonds unable to cross the high potential energy barriers. The presence of the bulky side groups also caused the energy barriers of the cis-configurations to increase dramatically, which prevented the polymeric segments from experiencing full rotation about the connecting bonds. For these polymers, it was clear that the fully extended configurations are the preferred configurations in the absence of strong electronegative atoms, backbones kinks or bulky side groups. The addition of any of these factors to the polymeric structures resulted in the polymeric chains being forced to assume less extended configurations. Rather interestingly, the length or bulkiness of the side groups didn't affect the end-to-end distance distribution to a great deal since the presence of quite large bulky side chain such as the
Trautmann, N
1976-01-01
A survey is given on the progress of fast chemical separation procedures during the last few years. Fast, discontinuous separation techniques are illustrated by a procedure for niobium. The use of such techniques for the chemical characterization of the heaviest known elements is described. Other rapid separation methods from aqueous solutions are summarized. The application of the high speed liquid chromatography to the separation of chemically similar elements is outlined. The use of the gas jet recoil transport method for nuclear reaction products and its combination with a continuous solvent extraction technique and with a thermochromatographic separation is presented. Different separation methods in the gas phase are briefly discussed and the attachment of a thermochromatographic technique to an on-line mass separator is shown. (45 refs).
Acoustofluidic bacteria separation
Li, Sixing; Ma, Fen; Bachman, Hunter; Cameron, Craig E.; Zeng, Xiangqun; Huang, Tony Jun
2017-01-01
Bacterial separation from human blood samples can help with the identification of pathogenic bacteria for sepsis diagnosis. In this work, we report an acoustofluidic device for label-free bacterial separation from human blood samples. In particular, we exploit the acoustic radiation force generated from a tilted-angle standing surface acoustic wave (taSSAW) field to separate Escherichia coli from human blood cells based on their size difference. Flow cytometry analysis of the E. coli separated from red blood cells shows a purity of more than 96%. Moreover, the label-free electrochemical detection of the separated E. coli displays reduced non-specific signals due to the removal of blood cells. Our acoustofluidic bacterial separation platform has advantages such as label-free separation, high biocompatibility, flexibility, low cost, miniaturization, automation, and ease of in-line integration. The platform can be incorporated with an on-chip sensor to realize a point-of-care sepsis diagnostic device.
Energy Technology Data Exchange (ETDEWEB)
Roennbaeck, Marie; Gustavsson, Lennart; Martinsson, Lars; Tullin, Claes; Johansson, Linda
2002-09-01
The objective of this report is to compile a survey of available technologies for separation of particles and to present research and development in the area of particle separation for biofuel plants smaller than 10 MW. Technical and economical opportunities to transfer the technologies used today in larger plants to smaller ones are discussed. As the health effects of aerosols are under investigation, the issue of separation of particle less than 1 {mu}m is especially scrutinised. Current research concerning the particle size distribution at different load is presented. The project has been realised partly as a literature survey, partly through contacts with scientists in the area and manufacturers of devices for flue gas cleaning and particle separation. The target group is owners of plants, manufacturers of devices and authorities with responsibility for air quality and energy planning. Fabric filters is an established technology that can perform low particle emissions (less than a few mg/m{sup 3}) at a low cost also at smaller plants. Also electrostatic precipitators can perform the same low emissions, but the cost for installation at smaller plants has to be reduced. Both these technologies can, properly designed, separate submicron particles. Cyclones can today as its best perform a little less than 100 mg/m{sup 3} at 13 % CO{sub 2}. Cyclones are used together with other technologies to achieve high separation at a low cost. Cyclones are attractive because of their simplicity and low price, but because they use inertia forces as separation mechanism, they can never separate submicron particles. Conventional scrubbers and flue gas condensers are capable of separation of submicron particles but the efficiency is lower compared with fabric filters and electrostatic precipitators. The emission level after a scrubber/flue gas condenser is about 70 - 80 mg/m{sup 3} at 13 % CO{sub 2}. New technologies for separation of particles oriented towards smaller plants and
[Separation anxiety in children].
Purper-Ouakil, Diane; Franc, Nathalie
2010-06-20
Separation anxiety disorder can be differentiated from developmental anxiety because of its intensity, persistence and negative impact on adaptive functioning. This disorder is closely linked to other anxiety and mood disorders and can also be associated with externalizing psychopathology in children and adolescents. Severe separation anxiety can result in school refusal and intra-familial violence. Cognitive behavioral therapies have the best evidence-based support for the treatment of separation anxiety disorder in children and adolescents. In addition, it is important to detect factors associated with persistence of anxiety such as systematic avoidance of separation and parental overprotection. The role of pediatricians and general practitioners in recognizing clinical separation anxiety and encouraging appropriate care and positive parental attitudes is essential, as separation anxiety is often associated with a variety of somatic symptoms.
[Separation anxiety. Theoretical considerations].
Blandin, N; Parquet, P J; Bailly, D
1994-01-01
The interest in separation anxiety is nowadays increasing: this disorder appearing during childhood may predispose to the occurrence of anxiety disorders (such as panic disorder and agoraphobia) and major depression into adulthood. Psychoanalytic theories differ on the nature of separation anxiety and its place in child development. For some authors, separation anxiety must be understood as resulting from the unconscious internal conflicts inherent in the individuation process and gradual attainment of autonomy. From this point of view, the fear of loss of mother by separation is not regarded as resulting from a real danger. However, Freud considers the primary experience of separation from protecting mother as the prototype situation of anxiety and compares the situations generating fear to separation experiences. For him, anxiety originates from two factors: the physiological fact is initiated at the time of birth but the primary traumatic situation is the separation from mother. This point of view may be compared with behavioral theories. Behavioral theories suggest that separation anxiety may be conditioned or learned from innate fears. In Freud's theory, the primary situation of anxiety resulting from the separation from mother plays a role comparable to innate fears. Grappling with the problem of separation anxiety, Bowlby emphasizes then the importance of the child's attachment to one person (mother or primary caregiver) and the fact that this attachment is instinctive. This point of view, based on the watch of infants, is akin to ethological theories on behaviour of non human primates. Bowlby especially shows that the reactions of infant separated from mother evolve on three stages: the phase of protestation which may constitute the prototype of adulthood anxiety, the phase of desperation which may be the prototype of depression, and the phase of detachment. He emphasizes so the role of early separations in the development of vulnerability to depression
Chang, Paul K
2014-01-01
Interdisciplinary and Advanced Topics in Science and Engineering, Volume 3: Separation of Flow presents the problem of the separation of fluid flow. This book provides information covering the fields of basic physical processes, analyses, and experiments concerning flow separation.Organized into 12 chapters, this volume begins with an overview of the flow separation on the body surface as discusses in various classical examples. This text then examines the analytical and experimental results of the laminar boundary layer of steady, two-dimensional flows in the subsonic speed range. Other chapt
Separations innovative concepts: Project summary
Energy Technology Data Exchange (ETDEWEB)
Lee, V.E. (ed.)
1988-05-01
This project summary includes the results of 10 innovations that were funded under the US Department's Innovative Concept Programs. The concepts address innovations that can substantially reduce the energy used in industrial separations. Each paper describes the proposed concept, and discusses the concept's potential energy savings, market applications, technical feasibility, prior work and state of the art, and future development needs.
The separation of adult separation anxiety disorder.
Baldwin, David S; Gordon, Robert; Abelli, Marianna; Pini, Stefano
2016-08-01
The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) categorization of mental disorders places "separation anxiety disorder" within the broad group of anxiety disorders, and its diagnosis no longer rests on establishing an onset during childhood or adolescence. In previous editions of DSM, it was included within the disorders usually first diagnosed in infancy, childhood, or adolescence, with the requirement for an onset of symptoms before the age of 18 years: symptomatic adults could only receive a retrospective diagnosis, based on establishing this early onset. The new position of separation anxiety disorder is based upon the findings of epidemiological studies that revealed the unexpectedly high prevalence of the condition in adults, often in individuals with an onset of symptoms after the teenage years; its prominent place within the DSM-5 group of anxiety disorders should encourage further research into its epidemiology, etiology, and treatment. This review examines the clinical features and boundaries of the condition, and offers guidance on how it can be distinguished from other anxiety disorders and other mental disorders in which "separation anxiety" may be apparent.
Krugman, Dorothy C.
1971-01-01
Discusses the role of the caseworker in providing support to children experiencing separation from their families and emphasizes the need to recognize that there are differences between those separation experiences dictated by the needs of children and those dictated by arbitrary or noncasework factors. (AJ)
Nauta, M.H.; Emmelkamp, P.M.G.; Sturmey, P.; Hersen, M.
2012-01-01
Separation anxiety disorder (SAD) is the only anxiety disorder that is specific to childhood; however, SAD has hardly ever been addressed as a separate disorder in clinical trials investigating treatment outcome. So far, only parent training has been developed specifically for SAD. This particular t
Mineka, Susan; Suomi, Stephen J.
1978-01-01
Reviews phenomena associated with social separation from attachment objects in nonhuman primates. Evaluates four theoretical treatments of separation in light of existing data: Bowlby's attachment-object-loss theory, Kaufman's conservation-withdrawal theory, Seligman's learned helplessness theory, and Solomon and Corbit's opponent-process theory.…
Nonterminal Separating Macro Grammars
Hogendorp, Jan Anne; Asveld, P.R.J.; Nijholt, A.; Verbeek, Leo A.M.
1987-01-01
We extend the concept of nonterminal separating (or NTS) context-free grammar to nonterminal separating $m$-macro grammar where the mode of derivation $m$ is equal to "unrestricted". "outside-in' or "inside-out". Then we show some (partial) characterization results for these NTS $m$-macro grammars.
DEFF Research Database (Denmark)
Fromager, Emmanuel; Cimiraglia, Renzo; Jensen, Hans Jørgen Aagaard
2010-01-01
A rigorous combination of multireference perturbation theory and density functional theory (DFT) is proposed. Based on a range separation of the regular two-electron Coulomb interaction, it combines a short-range density functional with second-order strongly contracted n-electron valence state pe...
NASA Armstrong's Approach to Store Separation Analysis
Acuff, Chris; Bui, Trong
2015-01-01
Presentation will an overview of NASA Armstrong's store separation capabilities and how they have been applied recently. Objective of the presentation is to brief Generation Orbit and other potential partners on NASA Armstrong's store separation capabilities. It will include discussions on the use of NAVSEP and Cart3D, as well as some Python scripting work to perform the analysis, and a short overview of this methodology applied to the Towed Glider Air Launch System. Collaboration with potential customers in this area could lead to funding for the further development of a store separation capability at NASA Armstrong, which would boost the portfolio of engineering expertise at the center.
Observation of Parity-Time Symmetry in Optically Induced Atomic Lattices
Zhang, Zhaoyang; Sheng, Jiteng; Yang, Liu; Miri, Mohammad-Ali; Christodoulides, Demetrios N; He, Bing; Zhang, Yanpeng; Xiao, Min
2016-01-01
A wide class of non-Hermitian Hamiltonians can possess entirely real eigenvalues when they have parity-time (PT) symmetric potentials. Due to their unusual properties, this family of non-Hermitian systems has recently attracted considerable attention in diverse areas of physics, especially in coupled gain-loss waveguides and optical lattices. Given that multi-level atoms can be quite efficient in judiciously synthesizing refractive index profiles, schemes based on atomic coherence have been recently proposed to realize optical potentials with PT-symmetric properties. Here, we experimentally demonstrate for the first time PT-symmetric optical lattices in a coherently-prepared four-level N-type atomic system. By appropriately tuning the pertinent atomic parameters, the onset of PT symmetry breaking is observed through measuring an abrupt phase-shift jump. The experimental realization of such readily reconfigurable and effectively controllable PT-symmetric periodic lattice structures sets a new stage for further...
Radiochemical separation of Cobalt
Erkelens, P.C. van
1961-01-01
A method is described for the radiochemical separation of cobalt based on the extraordinary stability of cobalt diethyldithiocarbamate. Interferences are few; only very small amounts of zinc and iron accompany cobalt, which is important in neutron-activation analysis.
Dai, Liang; Schmidt, Fabian
2015-01-01
The separate universe conjecture states that in General Relativity a density perturbation behaves locally (i.e. on scales much smaller than the wavelength of the mode) as a separate universe with different background density and curvature. We prove this conjecture for a spherical compensated tophat density perturbation of arbitrary amplitude and radius in $\\Lambda$CDM. We then use Conformal Fermi Coordinates to generalize this result to scalar perturbations of arbitrary configuration and scale in a general cosmology with a mixture of fluids, but to linear order in perturbations. In this case, the separate universe conjecture holds for the isotropic part of the perturbations. The anisotropic part on the other hand is exactly captured by a tidal field in the Newtonian form. We show that the separate universe picture is restricted to scales larger than the sound horizons of all fluid components. We then derive an expression for the locally measured matter bispectrum induced by a long-wavelength mode of arbitrary...
Electroextraction separation of dyestuffs
Energy Technology Data Exchange (ETDEWEB)
Luo, G.S.; Yu, M.J.; Jiang, W.B.; Zhu, S.L.; Dai, Y.Y. [Tsinghua Univ., Beijing (China). Dept. of Chemical Engineering
1999-03-01
Electroseparation technologies have prospects for significant growth well into the next century. Electroextraction, a coupled separation technique of solvent extraction with electrophoresis, was used to remove dyestuffs from their aqueous stream. A study on the characteristics of the separation technique was carried out with n-butanol/acid-chrom blue K/water and n-butanol/methyl blue/water as working systems. A continuous separation equipment was designed and sued in this work. The influences of two-phase flow, field strength, and concentration of the feed on the recovery of solute were studied. The results showed that much higher recovery of solute with less solvent consumption could be achieved by using this technique to remove dyes from their aqueous streams, especially for the separation of the dilute solution. When the field strength is increased, the recovery and mass flux increase. When the feed flow rate and the initial solute concentration are increased, the recovery decreases and the mass flux increases.
Shoulder separation - aftercare
... and top of your shoulder blade A severe shoulder separation You may need surgery right away if you have: Numbness in your fingers Cold fingers Muscle weakness in your arm Severe deformity of the joint
Radiochemical separation of Cobalt
Erkelens, P.C. van
1961-01-01
A method is described for the radiochemical separation of cobalt based on the extraordinary stability of cobalt diethyldithiocarbamate. Interferences are few; only very small amounts of zinc and iron accompany cobalt, which is important in neutron-activation analysis.
Bodlaender, H.L.; Koster, A.M.C.A.
2003-01-01
A set of vertices S Í V is called a safe separator for treewidth, if S is a separator of G, and the treewidth of G equals the maximum of the treewidth over all connected components W of G - S of the graph, obtained by making S a clique in the subgraph of G, induced by W È S. We show that such safe s
Mundschau, Michael [Longmont, CO; Xie, Xiaobing [Foster City, CA; Evenson, IV, Carl; Grimmer, Paul [Longmont, CO; Wright, Harold [Longmont, CO
2011-05-24
A method for separating a hydrogen-rich product stream from a feed stream comprising hydrogen and at least one carbon-containing gas, comprising feeding the feed stream, at an inlet pressure greater than atmospheric pressure and a temperature greater than 200.degree. C., to a hydrogen separation membrane system comprising a membrane that is selectively permeable to hydrogen, and producing a hydrogen-rich permeate product stream on the permeate side of the membrane and a carbon dioxide-rich product raffinate stream on the raffinate side of the membrane. A method for separating a hydrogen-rich product stream from a feed stream comprising hydrogen and at least one carbon-containing gas, comprising feeding the feed stream, at an inlet pressure greater than atmospheric pressure and a temperature greater than 200.degree. C., to an integrated water gas shift/hydrogen separation membrane system wherein the hydrogen separation membrane system comprises a membrane that is selectively permeable to hydrogen, and producing a hydrogen-rich permeate product stream on the permeate side of the membrane and a carbon dioxide-rich product raffinate stream on the raffinate side of the membrane. A method for pretreating a membrane, comprising: heating the membrane to a desired operating temperature and desired feed pressure in a flow of inert gas for a sufficient time to cause the membrane to mechanically deform; decreasing the feed pressure to approximately ambient pressure; and optionally, flowing an oxidizing agent across the membrane before, during, or after deformation of the membrane. A method of supporting a hydrogen separation membrane system comprising selecting a hydrogen separation membrane system comprising one or more catalyst outer layers deposited on a hydrogen transport membrane layer and sealing the hydrogen separation membrane system to a porous support.
Separation techniques: Chromatography
Coskun, Ozlem
2016-01-01
Chromatography is an important biophysical technique that enables the separation, identification, and purification of the components of a mixture for qualitative and quantitative analysis. Proteins can be purified based on characteristics such as size and shape, total charge, hydrophobic groups present on the surface, and binding capacity with the stationary phase. Four separation techniques based on molecular characteristics and interaction type use mechanisms of ion exchange, surface adsorp...
Distal humeral epiphyseal separation.
Moucha, Calin S; Mason, Dan E
2003-10-01
Distal humeral epiphyseal separation is an uncommon injury that is often misdiagnosed upon initial presentation. To make a timely, correct diagnosis, the treating physician must have a thorough understanding of basic anatomical relationships and an awareness of the existence of this injury. This is a case of a child who sustained a separation of the distal humeral epiphysis, as well as multiple other bony injuries, secondary to child abuse.
Chaotic attractors with separated scrolls
Energy Technology Data Exchange (ETDEWEB)
Bouallegue, Kais, E-mail: kais-bouallegue@yahoo.fr [Department of Electrical Engineering, Higher Institute of Applied Sciences and Technology of Sousse, Sousse (Tunisia)
2015-07-15
This paper proposes a new behavior of chaotic attractors with separated scrolls while combining Julia's process with Chua's attractor and Lorenz's attractor. The main motivation of this work is the ability to generate a set of separated scrolls with different behaviors, which in turn allows us to choose one or many scrolls combined with modulation (amplitude and frequency) for secure communication or synchronization. This set seems a new class of hyperchaos because each element of this set looks like a simple chaotic attractor with one positive Lyapunov exponent, so the cardinal of this set is greater than one. This new approach could be used to generate more general higher-dimensional hyperchaotic attractor for more potential application. Numerical simulations are given to show the effectiveness of the proposed theoretical results.
Gulf stream separation dynamics
Schoonover, Joseph
Climate models currently struggle with the more traditional, coarse ( O(100 km) ) representation of the ocean. In these coarse ocean simulations, western boundary currents are notoriously difficult to model accurately. The modeled Gulf Stream is typically seen exhibiting a mean pathway that is north of observations, and is linked to a warm sea-surface temperature bias in the Mid-Atlantic Bight. Although increased resolution ( O(10 km) ) improves the modeled Gulf Stream position, there is no clean recipe for obtaining the proper pathway. The 70 year history of literature on the Gulf Stream separation suggests that we have not reached a resolution on the dynamics that control the current's pathway just south of the Mid-Atlantic Bight. Without a concrete knowledge on the separation dynamics, we cannot provide a clean recipe for accurately modeling the Gulf Stream at increased resolutions. Further, any reliable parameterization that yields a realistic Gulf Stream path must express the proper physics of separation. The goal of this dissertation is to determine what controls the Gulf Stream separation. To do so, we examine the results of a model intercomparison study and a set of numerical regional terraforming experiments. It is argued that the separation is governed by local dynamics that are most sensitive to the steepening of the continental shelf, consistent with the topographic wave arrest hypothesis of Stern (1998). A linear extension of Stern's theory is provided, which illustrates that wave arrest is possible for a continuously stratified fluid.
Separably injective Banach spaces
Avilés, Antonio; Castillo, Jesús M F; González, Manuel; Moreno, Yolanda
2016-01-01
This monograph contains a detailed exposition of the up-to-date theory of separably injective spaces: new and old results are put into perspective with concrete examples (such as l∞/c0 and C(K) spaces, where K is a finite height compact space or an F-space, ultrapowers of L∞ spaces and spaces of universal disposition). It is no exaggeration to say that the theory of separably injective Banach spaces is strikingly different from that of injective spaces. For instance, separably injective Banach spaces are not necessarily isometric to, or complemented subspaces of, spaces of continuous functions on a compact space. Moreover, in contrast to the scarcity of examples and general results concerning injective spaces, we know of many different types of separably injective spaces and there is a rich theory around them. The monograph is completed with a preparatory chapter on injective spaces, a chapter on higher cardinal versions of separable injectivity and a lively discussion of open problems and further lines o...
Thermography pattern analysis and separation
Gao, Bin; Bai, Libing; Woo, W. L.; Tian, Guiyun
2014-06-01
Analysis of thermography spatial-transient patterns has considerable potential to enable automatic identification and quantification of defects in non-destructive testing and evaluation. This Letter proposes a non-negative pattern separation model for eddy current pulsed thermography to automatically extract important spatial and time patterns according to the transient thermal sequences without any pre-training or prior knowledge. In particular, the method is scale-invariant, such that large differences in surface emissivity, hot spots, and cool areas with dynamic range of thermal contrast can be extracted. Finally, an artificial slot in a steel sample with shining, black strip on the surface is tested to validate the proposed method.
Mass Separation by Metamaterials.
Restrepo-Flórez, Juan Manuel; Maldovan, Martin
2016-02-25
Being able to manipulate mass flow is critically important in a variety of physical processes in chemical and biomolecular science. For example, separation and catalytic systems, which requires precise control of mass diffusion, are crucial in the manufacturing of chemicals, crystal growth of semiconductors, waste recovery of biological solutes or chemicals, and production of artificial kidneys. Coordinate transformations and metamaterials are powerful methods to achieve precise manipulation of molecular diffusion. Here, we introduce a novel approach to obtain mass separation based on metamaterials that can sort chemical and biomolecular species by cloaking one compound while concentrating the other. A design strategy to realize such metamaterial using homogeneous isotropic materials is proposed. We present a practical case where a mixture of oxygen and nitrogen is manipulated using a metamaterial that cloaks nitrogen and concentrates oxygen. This work lays the foundation for molecular mass separation in biophysical and chemical systems through metamaterial devices.
Arshinoff, S A
1999-04-01
Phaco slice and separate retains the advantages of the chopping techniques of Nagahara, Koch, and Fukasaku but replaces chopping or snapping with slicing across the center of the phaco-tip-stabilized nucleus using a Nagahara chopper and then repositioning the chopper to optimally separate the divided lens halves. As the lens is rotated in the capsular bag, small pieces of the nuclear pie are sliced off, separated, emulsified, and aspirated. Emulsification and aspiration can alternatively be left until most or all the slices have been made. This technique works with a broader range of lens densities than other chopping techniques and uses no sculpting and very little phaco time. The phaco time required for this technique is relatively independent of nuclear density compared with a sculpting technique.
Membrane separation of hydrocarbons
Chang, Y. Alice; Kulkarni, Sudhir S.; Funk, Edward W.
1986-01-01
Mixtures of heavy oils and light hydrocarbons may be separated by passing the mixture through a polymeric membrane. The membrane which is utilized to effect the separation comprises a polymer which is capable of maintaining its integrity in the presence of hydrocarbon compounds and which has been modified by being subjected to the action of a sulfonating agent. Sulfonating agents which may be employed will include fuming sulfuric acid, chlorosulfonic acid, sulfur trioxide, etc., the surface or bulk modified polymer will contain a degree of sulfonation ranging from about 15 to about 50%. The separation process is effected at temperatures ranging from about ambient to about 100.degree. C. and pressures ranging from about 50 to about 1000 psig.
Schell, William J.
1979-01-01
A dry, fabric supported, polymeric gas separation membrane, such as cellulose acetate, is prepared by casting a solution of the polymer onto a shrinkable fabric preferably formed of synthetic polymers such as polyester or polyamide filaments before washing, stretching or calendering (so called griege goods). The supported membrane is then subjected to gelling, annealing, and drying by solvent exchange. During the processing steps, both the fabric support and the membrane shrink a preselected, controlled amount which prevents curling, wrinkling or cracking of the membrane in flat form or when spirally wound into a gas separation element.
Separation membrane development
Energy Technology Data Exchange (ETDEWEB)
Lee, M.W. [Savannah River Technology Center, Aiken, SC (United States)
1998-08-01
A ceramic membrane has been developed to separate hydrogen from other gases. The method used is a sol-gel process. A thin layer of dense ceramic material is coated on a coarse ceramic filter substrate. The pore size distribution in the thin layer is controlled by a densification of the coating materials by heat treatment. The membrane has been tested by permeation measurement of the hydrogen and other gases. Selectivity of the membrane has been achieved to separate hydrogen from carbon monoxide. The permeation rate of hydrogen through the ceramic membrane was about 20 times larger than Pd-Ag membrane.
Separation techniques: Chromatography
Coskun, Ozlem
2016-01-01
Chromatography is an important biophysical technique that enables the separation, identification, and purification of the components of a mixture for qualitative and quantitative analysis. Proteins can be purified based on characteristics such as size and shape, total charge, hydrophobic groups present on the surface, and binding capacity with the stationary phase. Four separation techniques based on molecular characteristics and interaction type use mechanisms of ion exchange, surface adsorption, partition, and size exclusion. Other chromatography techniques are based on the stationary bed, including column, thin layer, and paper chromatography. Column chromatography is one of the most common methods of protein purification. PMID:28058406
Learning Isometric Separation Maps
Vasiloglou, Nikolaos; Anderson, David V
2008-01-01
Maximum Variance Unfolding (MVU) and its variants have been very successful in embedding data-manifolds in lower dimensionality spaces, often revealing the true intrinsic dimensions. In this paper we show how to also incorporate supervised class information into an MVU-like method without breaking its convexity. We call this method the Isometric Separation Map and we show that the resulting kernel matrix can be used for a binary/multiclass Support Vector Machine in a semi-supervised (transductive) framework. We also show that the method always finds a kernel matrix that linearly separates the training data exactly without projecting them in infinite dimensional spaces.
Separators for electrochemical cells
Carlson, Steven Allen; Anakor, Ifenna Kingsley
2014-11-11
Provided are separators for use in an electrochemical cell comprising (a) an inorganic oxide and (b) an organic polymer, wherein the inorganic oxide comprises organic substituents. Preferably, the inorganic oxide comprises an hydrated aluminum oxide of the formula Al.sub.2O.sub.3.xH.sub.2O, wherein x is less than 1.0, and wherein the hydrated aluminum oxide comprises organic substituents, preferably comprising a reaction product of a multifunctional monomer and/or organic carbonate with an aluminum oxide, such as pseudo-boehmite and an aluminum oxide. Also provided are electrochemical cells comprising such separators.
Material review of Li ion battery separators
Weber, Christoph J.; Geiger, Sigrid; Falusi, Sandra; Roth, Michael
2014-06-01
Separators for Li Ion batteries have a strong impact on cell production, cell performance, life, as well as reliability and safety. The separator market volume is about 500 million m2 mainly based on consumer applications. It is expected to grow strongly over the next decade for mobile and stationary applications using large cells. At present, the market is essentially served by polyolefine membranes. Such membranes have some technological limitations, such as wettability, porosity, penetration resistance, shrinkage and meltdown. The development of a cell failure due to internal short circuit is potentially closely related to separator material properties. Consequently, advanced separators became an intense area of worldwide research and development activity in academia and industry. New separator technologies are being developed especially to address safety and reliability related property improvements.
Directory of Open Access Journals (Sweden)
Nobuyuki Kenmochi
1996-01-01
w is constrained to have double obstacles σ*≤w≤σ* (i.e., σ* and σ* are the threshold values of w. The objective of this paper is to discuss the semigroup {S(t} associated with the phase separation model, and construct its global attractor.
Phase separation micro molding
Vogelaar, Laura
2005-01-01
The research described in this thesis concerns the development of a new microfabrication method, Phase Separation Micro Molding (PSμM). While microfabrication is still best known from semiconductor industry, where it is used to integrate electrical components on a chip, the scope has immensely expan
Fathering After Marital Separation
Keshet, Harry Finkelstein; Rosenthal, Kristine M.
1978-01-01
Deals with experiences of a group of separated or divorced fathers who chose to remain fully involved in the upbringing of their children. As they underwent transition from married parenthood to single fatherhood, these men learned that meeting demands of child care contributed to personal stability and growth. (Author)
Energy Technology Data Exchange (ETDEWEB)
Fritz, P. [UFZ-Umweltforschungszentrum, Centre of Environmental Research Leipzig-Halle, Leipzig (Germany)
2000-07-01
Storm-runoff thus reflects the complex hydraulic behaviour of drainage basins and water-links of such systems. Water of different origin may participate in the events and in this lecture, the application of isotope techniques to separate storm hydrographs into different components will be presented.
DEFF Research Database (Denmark)
Dabelsteen, Hans B.
This PhD thesis asks how we can conceptualize the current separation doctrine of religion and politics in a country like Denmark, where the structure of the established church and peoplehood overlap. In order to answer this question, Hans Bruun Dabelsteen maps the current discussion of secularism...
Acromioclavicular Joint Separations
2013-01-01
Published online: 16 December 2012 # Springer Science+Business Media New York 2012 Abstract Acromioclavicular (AC) joint separations are common...injuries. The sports most likely to cause AC joint dislocations are football, soccer , hockey, rugby, and skiing, among others [9, 28, 29]. The major cause
1992-03-04
SEPARATEES Defense Outplacement Referral System (DORS) Since most of us are not independently wealthy, we will need a job after separation. DORS is...Job Assistance SPOUSES OF ALL SEPARATEES As a spouse you may take advantage of preparing Standard Form 17 1’s and resu- the outplacement services
Bill of Rights in Action, 1987
1987-01-01
The dimensions of the separation of powers principle are explored through three lessons in the subject areas of U.S. history, U.S. government, and world history. In 1748, a French nobleman, Baron de Montesquieu, wrote a book called "The Spirit of the Laws," in which he argued that there could be no liberty when all government power was…
Wetting and phase separation at surfaces
Indian Academy of Sciences (India)
Sanjay Puri; Kurt Binder
2005-06-01
We study the problem of surface-directed spinodal decomposition, viz., the dynamical interplay of wetting and phase separation at surfaces. In particular, we focus on the kinetics of wetting-layer growth in a semi-infinite geometry for arbitrary surface potentials and mixture compositions. We also present representative results for phase separation in confined geometries, e.g., cylindrical pores, thin films, etc.
Institute of Scientific and Technical Information of China (English)
Fang Cheng; Wu Bingliang; Zhang Wu-ming; Zhou Xing-gao
2004-01-01
A novel electrophoresis technique, in which a strip of perflurosulfonic-acid (Nafion 117) membrane was used to replace the conventional separation column and liquid buffer solution within, was developed and employed to separate the mixture of dopamine and epinephrine under a low separation voltage of 100 V with quadruple pulses amperometry detection. It was showed that the so-called Nafion membrane electrophoresis could be one of very simple and easy method and has the potentiality to be used to separate and analyze some small organic biologic molecules.
Microgravity Passive Phase Separator
Paragano, Matthew; Indoe, William; Darmetko, Jeffrey
2012-01-01
A new invention disclosure discusses a structure and process for separating gas from liquids in microgravity. The Microgravity Passive Phase Separator consists of two concentric, pleated, woven stainless- steel screens (25-micrometer nominal pore) with an axial inlet, and an annular outlet between both screens (see figure). Water enters at one end of the center screen at high velocity, eventually passing through the inner screen and out through the annular exit. As gas is introduced into the flow stream, the drag force exerted on the bubble pushes it downstream until flow stagnation or until it reaches an equilibrium point between the surface tension holding bubble to the screen and the drag force. Gas bubbles of a given size will form a front that is moved further down the length of the inner screen with increasing velocity. As more bubbles are added, the front location will remain fixed, but additional bubbles will move to the end of the unit, eventually coming to rest in the large cavity between the unit housing and the outer screen (storage area). Owing to the small size of the pores and the hydrophilic nature of the screen material, gas does not pass through the screen and is retained within the unit for emptying during ground processing. If debris is picked up on the screen, the area closest to the inlet will become clogged, so high-velocity flow will persist farther down the length of the center screen, pushing the bubble front further from the inlet of the inner screen. It is desired to keep the velocity high enough so that, for any bubble size, an area of clean screen exists between the bubbles and the debris. The primary benefits of this innovation are the lack of any need for additional power, strip gas, or location for venting the separated gas. As the unit contains no membrane, the transport fluid will not be lost due to evaporation in the process of gas separation. Separation is performed with relatively low pressure drop based on the large surface
2016-01-01
Footage of the 70 degree ISOLDE GPS separator magnet MAG70 as well as the switchyard for the Central Mass and GLM (GPS Low Mass) and GHM (GPS High Mass) beamlines in the GPS separator zone. In the GPS20 vacuum sector equipment such as the long GPS scanner 482 / 483 unit, faraday cup FC 490, vacuum valves and wiregrid piston WG210 and WG475 and radiation monitors can also be seen. Also the RILIS laser guidance and trajectory can be seen, the GPS main beamgate switch box and the actual GLM, GHM and Central Beamline beamgates in the beamlines as well as the first electrostatic quadrupoles for the GPS lines. Close up of the GHM deflector plates motor and connections and the inspection glass at the GHM side of the switchyard.
2016-01-01
Footage of the 90 and 60 degree ISOLDE HRS separator magnets in the HRS separator zone. In the two vacuum sectors HRS20 and HRS30 equipment such as the HRS slits SL240, the HRS faraday cup FC300 and wiregrid WG210 can be spotted. Vacuum valves, turbo pumps, beamlines, quadrupoles, water and compressed air connections, DC and signal cabling can be seen throughout the video. The HRS main and user beamgate in the beamline between MAG90 and MAG60 and its switchboxes as well as all vacuum bellows and flanges are shown. Instrumentation such as the HRS scanner unit 482 / 483, the HRS WG470 wiregrid and slits piston can be seen. The different quadrupoles and supports are shown as well as the RILIS guidance tubes and installation at the magnets and the different radiation monitors.
Nylon separators. [thermal degradation
Lim, H. S.
1977-01-01
A nylon separator was placed in a flooded condition in K0H solution and heated at various high temperatures ranging from 60 C to 110 C. The weight decrease was measured and the molecular weight and decomposition product were analyzed to determine: (1) the effect of K0H concentration on the hydrolysis rate; (2) the effect of K0H concentration on nylon degradation; (3) the activation energy at different K0H concentrations; and (4) the effect of oxygen on nylon degradation. The nylon hydrolysis rate is shown to increase as K0H concentration is decreased 34%, giving a maximum rate at about 16%. Separator hydrolysis is confirmed by molecular weight decrease in age of the batteries, and the reaction of nylon with molecular oxygen is probably negligible, compared to hydrolysis. The extrapolated rate value from the high temperature experiment correlates well with experimental values at 35 degrees.
Battery separator manufacturing process
Energy Technology Data Exchange (ETDEWEB)
Palmer, N.I.; Sugarman, N.
1974-12-27
A battery with a positive plate, a negative plate, and a separator of polymeric resin having a degree of undesirable hydrophobia, solid below 180/sup 0/F, extrudable as a hot melt, and resistant to degradation by at least either acids or alkalies positioned between the plates is described. The separator comprises a nonwoven mat of fibers, the fibers being comprised of the polymeric resin and a wetting agent in an amount of 0.5 to 20 percent by weight based on the weight of the resin with the amount being incompatible with the resin below the melting point of the resin such that the wetting agent will bloom over a period of time at ambient temperatures in a battery, yet being compatible with the resin at the extrusion temperature and bringing about blooming to the surface of the fibers when the fibers are subjected to heat and pressure.
DEFF Research Database (Denmark)
Dabelsteen, Hans B.
analysis, Dabelsteen study Danish secularism as an ideological concept. He finds that the conceptual structure of Danish secularism holds separation-as-principled distance at its core. Institutionally this particularly pertains to the establishment arrangement, and in practice it translates...... and proposes two conceptual expansions. The first is to include modest establishment in a framework of secularism defensible by political liberalism, and the second is to consider secularism in close connection to a theory of peoplehood. Methodologically positioned between interpretive realism and policy...... into the principle of treating everybody equally (with religious freedom, equality and Danish peoplehood as the most important principles adjacent to secularism). In a study of the historical roots of the separation doctrine and two current policy cases (same-sex marriage and reforms of church governance...
Acoustophoresis separation method
Heyman, Joseph S. (Inventor)
1993-01-01
A method and apparatus are provided for acoustophoresis, i.e., the separation of species via acoustic waves. An ultrasonic transducer applies an acoustic wave to one end of a sample container containing at least two species having different acoustic absorptions. The wave has a frequency tuned to or harmonized with the point of resonance of the species to be separated. This wave causes the species to be driven to an opposite end of the sample container for removal. A second ultrasonic transducer may be provided to apply a second, oppositely directed acoustic wave to prevent undesired streaming. In addition, a radio frequency tuned to the mechanical resonance and coupled with a magnetic field can serve to identify a species in a medium comprising species with similar absorption coefficients, whereby an acoustic wave having a frequency corresponding to this gyrational rate can then be applied to sweep the identified species to one end of the container for removal.
Todd , Matthew H
2014-01-01
In one handy volume this handbook summarizes the most common synthetic methods for the separation of racemic mixtures, allowing an easy comparison of the different strategies described in the literature.Alongside classical methods, the authors also consider kinetic resolutions, dynamic kinetic resolutions, divergent reactions of a racemic mixture, and a number of ""neglected"" cases not covered elsewhere, such as the use of circularly polarized light, polymerizations, ""ripening"" processes, dynamic combinatorial chemistry, and several thermodynamic processes. The result is a thorough introdu
Separation Logic and Concurrency
Bornat, Richard
Concurrent separation logic is a development of Hoare logic adapted to deal with pointers and concurrency. Since its inception, it has been enhanced with a treatment of permissions to enable sharing of data between threads, and a treatment of variables as resource alongside heap cells as resource. An introduction to the logic is given with several examples of proofs, culminating in a treatment of Simpson's 4-slot algorithm, an instance of racy non-blocking concurrency.
Giménez, Sixto; Rogach, Andrey L.; Lutich, Andrey A.; Gross, Dieter; Poeschl, Andreas; Susha, Andrei S.; Mora-Seró, Ivan; Lana-Villarreal, Teresa; Bisquert, Juan
2011-07-01
Hybrid structures of colloidal quantum dots (QDs) with Ru-dyes have been studied as candidates for panchromatic sensitizers for TiO2-based solar cells. Steady-state and time resolved photoluminescence spectroscopy and photocurrent measurements have been employed to identify the prevailing transfer mechanisms for photogenerated excitons between CdSe QDs capped with a traditional bulky organic ligand trioctylphosphine and Ru-dyes (N3 or Ru505) deposited onto inert glass or mesoporous TiO2 substrates. The type II energy level alignment between the QDs and both N3 and Ru505 offers a possibility for the directional charge separation, with electrons transferred to the QDs and holes to the dye. This scenario is indeed valid for the QD/Ru505 and TiO2/QD/Ru505 hybrid systems, with the negligible spectral overlap between the emission of the QDs and the absorption of the Ru505 dye. For the QD/N3 and TiO2/QD/N3 hybrid systems, the spectral overlap favors the longer range energy transfer from the QDs to N3, independently of the presence of the electron acceptor TiO2.
Innovative Separations Technologies
Energy Technology Data Exchange (ETDEWEB)
J. Tripp; N. Soelberg; R. Wigeland
2011-05-01
Reprocessing used nuclear fuel (UNF) is a multi-faceted problem involving chemistry, material properties, and engineering. Technology options are available to meet a variety of processing goals. A decision about which reprocessing method is best depends significantly on the process attributes considered to be a priority. New methods of reprocessing that could provide advantages over the aqueous Plutonium Uranium Reduction Extraction (PUREX) and Uranium Extraction + (UREX+) processes, electrochemical, and other approaches are under investigation in the Fuel Cycle Research and Development (FCR&D) Separations Campaign. In an attempt to develop a revolutionary approach to UNF recycle that may have more favorable characteristics than existing technologies, five innovative separations projects have been initiated. These include: (1) Nitrogen Trifluoride for UNF Processing; (2) Reactive Fluoride Gas (SF6) for UNF Processing; (3) Dry Head-end Nitration Processing; (4) Chlorination Processing of UNF; and (5) Enhanced Oxidation/Chlorination Processing of UNF. This report provides a description of the proposed processes, explores how they fit into the Modified Open Cycle (MOC) and Full Recycle (FR) fuel cycles, and identifies performance differences when compared to 'reference' advanced aqueous and fluoride volatility separations cases. To be able to highlight the key changes to the reference case, general background on advanced aqueous solvent extraction, advanced oxidative processes (e.g., volumetric oxidation, or 'voloxidation,' which is high temperature reaction of oxide UNF with oxygen, or modified using other oxidizing and reducing gases), and fluorination and chlorination processes is provided.
Colour Separation and Aversion
Directory of Open Access Journals (Sweden)
Sarah M Haigh
2012-05-01
Full Text Available Aversion to achromatic patterns is well documented but relatively little is known about discomfort from chromatic patterns. Large colour differences are uncommon in the natural environment and deviation from natural statistics makes images uncomfortable (Fernandez and Wilkins 2008, Perception, 37(7, 1098–113; Juricevic et al 2010, Perception, 39(7, 884–899. We report twelve studies documenting a linear increase in aversion to chromatic square-wave gratings as a function of the separation in UCS chromaticity between the component bars, independent of their luminance contrast. Two possible explanations for the aversion were investigated: (1 accommodative response, or (2 cortical metabolic demand. We found no correlation between chromaticity separation and accommodative lag or variance in lag, measured using an open-field autorefractor. However, near infrared spectroscopy of the occipital cortex revealed a larger oxyhaemoglobin response to patterns with large chromaticity separation. The aversion may be cortical in origin and does not appear to be due to accommodation.
Rem, P.C.; Bakker, M.C.M.; Berkhout, S.P.M.; Rahman, M.A.
2012-01-01
Eddy current separation apparatus (1) for separating particles (20) from a particle stream (w), wherein the apparatus (1) comprises a separator drum (4) adapted to create a first particle fraction (21) and a second particle fraction (23), a feeding device (2) upstream of the separator drum (4) for s
Maddock, A.G.; Smith, F.
1959-08-25
A method is described for separating plutonium from uranium and fission products by treating a nitrate solution of fission products, uranium, and hexavalent plutonium with a relatively water-insoluble fluoride to adsorb fission products on the fluoride, treating the residual solution with a reducing agent for plutonium to reduce its valence to four and less, treating the reduced plutonium solution with a relatively insoluble fluoride to adsorb the plutonium on the fluoride, removing the solution, and subsequently treating the fluoride with its adsorbed plutonium with a concentrated aqueous solution of at least one of a group consisting of aluminum nitrate, ferric nitrate, and manganous nitrate to remove the plutonium from the fluoride.
Karraker, D.G.
1959-07-14
A liquid-liquid extraction process is presented for the recovery of polonium from lead and bismuth. According to the invention an acidic aqueous chloride phase containing the polonium, lead, and bismuth values is contacted with a tributyl phosphate ether phase. The polonium preferentially enters the organic phase which is then separated and washed with an aqueous hydrochloric solution to remove any lead or bismuth which may also have been extracted. The now highly purified polonium in the organic phase may be transferred to an aqueous solution by extraction with aqueous nitric acid.
Beaufait, L.J. Jr.; Stevenson, F.R.; Rollefson, G.K.
1958-11-18
The recovery of plutonium ions from neutron irradiated uranium can be accomplished by bufferlng an aqueous solutlon of the irradiated materials containing tetravalent plutonium to a pH of 4 to 7, adding sufficient acetate to the solution to complex the uranyl present, adding ferric nitrate to form a colloid of ferric hydroxide, plutonlum, and associated fission products, removing and dissolving the colloid in aqueous nitric acid, oxldizlng the plutonium to the hexavalent state by adding permanganate or dichromate, treating the resultant solution with ferric nitrate to form a colloid of ferric hydroxide and associated fission products, and separating the colloid from the plutonlum left in solution.
Cesium and Strontium Separation Technologies Literature Review
Energy Technology Data Exchange (ETDEWEB)
T. A. Todd; T. A. Todd; J. D. Law; R. S. Herbst
2004-03-01
Integral to the Advanced Fuel Cycle Initiative (AFCI) Program’s proposed closed nuclear fuel cycle, the fission products cesium and strontium in the dissolved spent nuclear fuel stream are to be separated and managed separately. A comprehensive literature survey is presented to identify cesium and strontium separation technologies that have the highest potential and to focus research and development efforts on these technologies. Removal of these high-heat-emitting fission products reduces the radiation fields in subsequent fuel cycle reprocessing streams and provides a significant short-term (100 yr) heat source reduction in the repository. This, along with separation of actinides, may provide a substantial future improvement in the amount of fuel that could be stored in a geologic repository. The survey and review of the candidate cesium and strontium separation technologies are presented herein. Because the AFCI program intends to manage cesium and strontium together, technologies that simultaneously separate both elements are of the greatest interest, relative to technologies that separate only one of the two elements.
Cell separation using electric fields
Mangano, Joseph (Inventor); Eppich, Henry (Inventor)
2009-01-01
The present invention involves methods and devices which enable discrete objects having a conducting inner core, surrounded by a dielectric membrane to be selectively inactivated by electric fields via irreversible breakdown of their dielectric membrane. One important application of the invention is in the selection, purification, and/or purging of desired or undesired biological cells from cell suspensions. According to the invention, electric fields can be utilized to selectively inactivate and render non-viable particular subpopulations of cells in a suspension, while not adversely affecting other desired subpopulations. According to the inventive methods, the cells can be selected on the basis of intrinsic or induced differences in a characteristic electroporation threshold, which can depend, for example, on a difference in cell size and/or critical dielectric membrane breakdown voltage. The invention enables effective cell separation without the need to employ undesirable exogenous agents, such as toxins or antibodies. The inventive method also enables relatively rapid cell separation involving a relatively low degree of trauma or modification to the selected, desired cells. The inventive method has a variety of potential applications in clinical medicine, research, etc., with two of the more important foreseeable applications being stem cell enrichment/isolation, and cancer cell purging.
SOFC and Gas Separation Membranes
DEFF Research Database (Denmark)
Hagen, Anke; Hendriksen, Peter Vang; Søgaard, Martin
2009-01-01
, increase the efficiency of power production processes from fossil fuels and also to consider carbon capture and sequestration (CCS). Solid oxide fuel cells (SOFCs) convert the chemical energy bound in a fuel directly into electrical energy at temperatures ranging from 600 to 1000 oC, depending...... on the materials used in the SOFCs. Due to the high efficiencies, the amount of CO2 emitted from carbon containing fuels is smaller compared to conventional energy production technologies based on fuel combustion. Furthermore, CO2 is formed at the anode side of the fuel cell together with steam, and thus separated...... as SOFCs. Such membranes can potentially be used in Oxyfuel processes as well as in IGCC (Integrated Gasification Combined Cycle) power plants for supply of process oxygen, which may reduce cost of carbon capture and storage as dilution of the flue gas with nitrogen is avoided. Both technologies are very...
Stone, L.L.; Otten, R.; Soenens, B.; Engels, R.C.M.E.; Janssens, J.M.A.M.
2015-01-01
Although separation anxiety is prevalent in young children, it remains unclear whether and how maternal separation anxiety is related to separation anxiety in children. This study examined associations between maternal separation anxiety and separation anxiety in children, and the potential effect p
Particle separator scroll vanes
Energy Technology Data Exchange (ETDEWEB)
Lastrina, F. A.; Mayer, J. C.; Pommer, L. M.
1985-07-09
An inlet particle separator for a gas turbine engine is provided with unique vanes distributed around an entrance to a particle collection chamber. The vanes are uniquely constructed to direct extraneous particles that enter the engine into the collection chamber and prevent the particles from rebounding back into the engine's air flow stream. The vanes are provided with several features to accomplish this function, including upstream faces that are sharply angled towards air flow stream direction to cause particles to bounce towards the collection chamber. In addition, throat regions between the vanes cause a localized air flow acceleration and a focusing of the particles that aid in directing the particles in a proper direction.
Nebulized therapy. SEPAR year.
Olveira, Casilda; Muñoz, Ana; Domenech, Adolfo
2014-12-01
Inhaled drugs are deposited directly in the respiratory tract. They therefore achieve higher concentrations with faster onset of action and fewer side effects than when used systemically. Nebulized drugs are mainly recommended for patients that require high doses of bronchodilators, when they need to inhale drugs that only exist in this form (antibiotics or dornase alfa) or when they are unable to use other inhalation devices. Technological development in recent years has led to new devices that optimize pulmonary deposits and reduce the time needed for treatment. In this review we focus solely on drugs currently used, or under investigation, for nebulization in adult patients; basically bronchodilators, inhaled steroids, antibiotics, antifungals, mucolytics and others such as anticoagulants, prostanoids and lidocaine. Copyright © 2014 SEPAR. Published by Elsevier Espana. All rights reserved.
Block copolymer battery separator
Energy Technology Data Exchange (ETDEWEB)
Wong, David; Balsara, Nitash Pervez
2016-04-26
The invention herein described is the use of a block copolymer/homopolymer blend for creating nanoporous materials for transport applications. Specifically, this is demonstrated by using the block copolymer poly(styrene-block-ethylene-block-styrene) (SES) and blending it with homopolymer polystyrene (PS). After blending the polymers, a film is cast, and the film is submerged in tetrahydrofuran, which removes the PS. This creates a nanoporous polymer film, whereby the holes are lined with PS. Control of morphology of the system is achieved by manipulating the amount of PS added and the relative size of the PS added. The porous nature of these films was demonstrated by measuring the ionic conductivity in a traditional battery electrolyte, 1M LiPF.sub.6 in EC/DEC (1:1 v/v) using AC impedance spectroscopy and comparing these results to commercially available battery separators.
Block copolymer battery separator
Wong, David; Balsara, Nitash Pervez
2016-04-26
The invention herein described is the use of a block copolymer/homopolymer blend for creating nanoporous materials for transport applications. Specifically, this is demonstrated by using the block copolymer poly(styrene-block-ethylene-block-styrene) (SES) and blending it with homopolymer polystyrene (PS). After blending the polymers, a film is cast, and the film is submerged in tetrahydrofuran, which removes the PS. This creates a nanoporous polymer film, whereby the holes are lined with PS. Control of morphology of the system is achieved by manipulating the amount of PS added and the relative size of the PS added. The porous nature of these films was demonstrated by measuring the ionic conductivity in a traditional battery electrolyte, 1M LiPF.sub.6 in EC/DEC (1:1 v/v) using AC impedance spectroscopy and comparing these results to commercially available battery separators.
Gravity separation for oil wastewater treatment
Golomeova, Mirjana; Zendelska, Afrodita; Krstev, Boris; Krstev, Aleksandar
2010-01-01
In this paper, the applications of gravity separation for oil wastewater treatment are presented. Described is operation on conventional gravity separation and parallel plate separation. Key words: gravity separation, oil, conventional gravity separation, parallel plate separation.
Gravity separation for oil wastewater treatment
Golomeova, Mirjana; Zendelska, Afrodita; Krstev, Boris; Krstev, Aleksandar
2010-01-01
In this paper, the applications of gravity separation for oil wastewater treatment are presented. Described is operation on conventional gravity separation and parallel plate separation. Key words: gravity separation, oil, conventional gravity separation, parallel plate separation.
Chromatographic Separations Using Solid-Phase Extraction Cartridges: Separation of Wine Phenolics
Brenneman, Charles A.; Ebeler, Susan E.
1999-12-01
We describe a simple laboratory experiment that demonstrates the principles of chromatographic separation using solid-phase extraction columns and red wine. By adjusting pH and mobile phase composition, the wine is separated into three fractions of differing polarity. The content of each fraction can be monitored by UV-vis spectroscopy. When the experiment is combined with experiments involving HPLC or GC separations, students gain a greater appreciation for and understanding of the highly automated instrumental systems currently available. In addition, they learn about the chemistry of polyphenolic compounds, which are present in many foods and beverages and which are receiving much attention for their potentially beneficial health effects.
Selectivity in capillary electrokinetic separations
de Zeeuw, R.A; de Jong, G.J.; Ensing, K
1999-01-01
This review gives a survey of selectivity modes in capillary electrophoresis separations in pharmaceutical analysis and bioanalysis. Despite the high efficiencies of these separation techniques, good selectivity is required to allow quantitation or identification of a Chemistry and Toxicology, parti
Physical Separation in the Workplace
DEFF Research Database (Denmark)
Stea, Diego; Foss, Nicolai Juul; Holdt Christensen, Peter
2015-01-01
Physical separation is pervasive in organizations, and has powerful effects on employee motivation and organizational behaviors. However, research shows that workplace separation is characterized by a variety of tradeoffs, tensions, and challenges that lead to both positive and negative outcomes...
Determine separations process strategy decision
Energy Technology Data Exchange (ETDEWEB)
Slaathaug, E.J.
1996-01-01
This study provides a summary level comparative analysis of selected, top-level, waste treatment strategies. These strategies include No Separations, Separations (high-level/low-level separations), and Deferred Separations of the tank waste. These three strategies encompass the full range of viable processing alternatives based upon full retrieval of the tank wastes. The assumption of full retrieval of the tank wastes is a predecessor decision and will not be revisited in this study.
Composite separators and redox flow batteries based on porous separators
Li, Bin; Wei, Xiaoliang; Luo, Qingtao; Nie, Zimin; Wang, Wei; Sprenkle, Vincent L.
2016-01-12
Composite separators having a porous structure and including acid-stable, hydrophilic, inorganic particles enmeshed in a substantially fully fluorinated polyolefin matrix can be utilized in a number of applications. The inorganic particles can provide hydrophilic characteristics. The pores of the separator result in good selectivity and electrical conductivity. The fluorinated polymeric backbone can result in high chemical stability. Accordingly, one application of the composite separators is in redox flow batteries as low cost membranes. In such applications, the composite separator can also enable additional property-enhancing features compared to ion-exchange membranes. For example, simple capacity control can be achieved through hydraulic pressure by balancing the volumes of electrolyte on each side of the separator. While a porous separator can also allow for volume and pressure regulation, in RFBs that utilize corrosive and/or oxidizing compounds, the composite separators described herein are preferable for their robustness in the presence of such compounds.
Separating Underdetermined Convolutive Speech Mixtures
DEFF Research Database (Denmark)
Pedersen, Michael Syskind; Wang, DeLiang; Larsen, Jan
2006-01-01
a method for underdetermined blind source separation of convolutive mixtures. The proposed framework is applicable for separation of instantaneous as well as convolutive speech mixtures. It is possible to iteratively extract each speech signal from the mixture by combining blind source separation...
General Motors sidestream separator
Energy Technology Data Exchange (ETDEWEB)
Tessier, R.J.
1981-01-01
On February 15, 1980, the United States Environmental Protection Agency, acting pursuant to Paragraph 113(D) (4) of the Clean Air Act, issued to General Motors an innovative technology order covering fifteen coal-fired spreader-stoker boilers located at six General Motors plants in Ohio. The purpose and effect of this order was to permit General Motors time to develop a new, innovative technique for controlling particulate emissions from the specified boilers before compliance with the federally approved Ohio particulate control regulation was required. This new technology was christened, The Sidestream Separator, by General Motors. It provides a highly cost effective means of reducing particulate emissions below levels currently obtainable with conventionally used high efficiency mechanical collectors. These improvements could prove to be of substantial benefit to many industrial facilities with spreader-stoker coal-fired boilers that cannot be brought into compliance with applicble air pollution regulations except by application of far more expensive and unwieldly electrostatic precipitators (ESP's) or fabric filters (baghouses).
PARAFFIN SEPARATION VACUUM DISTILLATION
Directory of Open Access Journals (Sweden)
Zaid A. Abdulrahman
2013-05-01
Full Text Available Simulated column performance curves were constructed for existing paraffin separation vacuum distillation column in LAB plant (Arab Detergent Company/Baiji-Iraq. The variables considered in this study are the thermodynamic model option, top vacuum pressure, top and bottom temperatures, feed temperature, feed composition & reflux ratio. Also simulated columns profiles for the temperature, vapor & liquid flow rates composition were constructed. Four different thermodynamic model options (SRK, TSRK, PR, and ESSO were used, affecting the results within 1-25% variation for the most cases.The simulated results show that about 2% to 8 % of paraffin (C10, C11, C12, & C13 present at the bottom stream which may cause a problem in the LAB plant. The major variations were noticed for the top temperature & the paraffin weight fractions at bottom section with top vacuum pressure. The bottom temperature above 240 oC is not recommended because the total bottom flow rate decreases sharply, where as the weight fraction of paraffins decrease slightly. The study gives evidence about a successful simulation with CHEMCAD
2011-11-01
central core (permeate tube). Each sheet consists of oleophobic (oil repelling) outer layers and a hydrophilic (water attracting) central layer to...without clogging. Each membrane sheet has two oleophobic (oil repelling) outer surfaces and a hydrophilic (water attracting) inner layer. This...fewer alarms for the crew and minimizes potential for accidental discharge. • Cleans in place without clogging The SPIR-O-LA TOR Membranes’ oleophobic
Rotation and instabilities for isotope and mass separation
Rax, J.-M.; Gueroult, R.
2016-10-01
Rotating plasmas have the potential to offer unique capabilities for isotope and mass separation. Among the various electric and magnetic field configurations offering mass separation capabilities, rotating plasmas produced through static or oscillating fields are shown to be a leading candidate for tackling the unsolved problem of large-scale plasma separation. The successful development and deployment of industrial-scale plasma separation technologies could, among many other applications, provide an innovative path towards advanced sustainable nuclear energy. In this context, the potential and versatility of plasma rotation induced by rotating magnetic fields is uncovered and analysed. Analytical stability diagrams are derived from rotating ion orbits as a function of ion mass. Based on these findings, the basic principles of a rotating field plasma separator are then introduced. In light of these results, challenges associated with this original separation process are underlined, and the main directions for a future research program aimed at this important unsolved problem of applied plasma physics are identified.
Gas storage and separation by electric field swing adsorption
Currier, Robert P; Obrey, Stephen J; Devlin, David J; Sansinena, Jose Maria
2013-05-28
Gases are stored, separated, and/or concentrated. An electric field is applied across a porous dielectric adsorbent material. A gas component from a gas mixture may be selectively separated inside the energized dielectric. Gas is stored in the energized dielectric for as long as the dielectric is energized. The energized dielectric selectively separates, or concentrates, a gas component of the gas mixture. When the potential is removed, gas from inside the dielectric is released.
Separators - Technology review: Ceramic based separators for secondary batteries
Nestler, Tina; Schmid, Robert; Münchgesang, Wolfram; Bazhenov, Vasilii; Schilm, Jochen; Leisegang, Tilmann; Meyer, Dirk C.
2014-06-01
Besides a continuous increase of the worldwide use of electricity, the electric energy storage technology market is a growing sector. At the latest since the German energy transition ("Energiewende") was announced, technological solutions for the storage of renewable energy have been intensively studied. Storage technologies in various forms are commercially available. A widespread technology is the electrochemical cell. Here the cost per kWh, e. g. determined by energy density, production process and cycle life, is of main interest. Commonly, an electrochemical cell consists of an anode and a cathode that are separated by an ion permeable or ion conductive membrane - the separator - as one of the main components. Many applications use polymeric separators whose pores are filled with liquid electrolyte, providing high power densities. However, problems arise from different failure mechanisms during cell operation, which can affect the integrity and functionality of these separators. In the case of excessive heating or mechanical damage, the polymeric separators become an incalculable security risk. Furthermore, the growth of metallic dendrites between the electrodes leads to unwanted short circuits. In order to minimize these risks, temperature stable and non-flammable ceramic particles can be added, forming so-called composite separators. Full ceramic separators, in turn, are currently commercially used only for high-temperature operation systems, due to their comparably low ion conductivity at room temperature. However, as security and lifetime demands increase, these materials turn into focus also for future room temperature applications. Hence, growing research effort is being spent on the improvement of the ion conductivity of these ceramic solid electrolyte materials, acting as separator and electrolyte at the same time. Starting with a short overview of available separator technologies and the separator market, this review focuses on ceramic-based separators
Mathematical modelling of membrane separation
DEFF Research Database (Denmark)
Vinther, Frank
This thesis concerns mathematical modelling of membrane separation. The thesis consists of introductory theory on membrane separation, equations of motion, and properties of dextran, which will be the solute species throughout the thesis. Furthermore, the thesis consist of three separate mathemat......This thesis concerns mathematical modelling of membrane separation. The thesis consists of introductory theory on membrane separation, equations of motion, and properties of dextran, which will be the solute species throughout the thesis. Furthermore, the thesis consist of three separate....... It is found that the probability of entering the pore is highest when the largest of the radii in the ellipse is equal to half the radius of the pore, in case of molecules with circular radius less than the pore radius. The results are directly related to the macroscopic distribution coefficient...
Capillary Separation: Micellar Electrokinetic Chromatography
Terabe, Shigeru
2009-07-01
Micellar electrokinetic chromatography (MEKC), a separation mode of capillary electrophoresis (CE), has enabled the separation of electrically neutral analytes. MEKC can be performed by adding an ionic micelle to the running solution of CE without modifying the instrument. Its separation principle is based on the differential migration of the ionic micelles and the bulk running buffer under electrophoresis conditions and on the interaction between the analyte and the micelle. Hence, MEKC's separation principle is similar to that of chromatography. MEKC is a useful technique particularly for the separation of small molecules, both neutral and charged, and yields high-efficiency separation in a short time with minimum amounts of sample and reagents. To improve the concentration sensitivity of detection, several on-line sample preconcentration techniques such as sweeping have been developed.
Separable programming theory and methods
Stefanov, Stefan M
2001-01-01
In this book, the author considers separable programming and, in particular, one of its important cases - convex separable programming Some general results are presented, techniques of approximating the separable problem by linear programming and dynamic programming are considered Convex separable programs subject to inequality equality constraint(s) and bounds on variables are also studied and iterative algorithms of polynomial complexity are proposed As an application, these algorithms are used in the implementation of stochastic quasigradient methods to some separable stochastic programs Numerical approximation with respect to I1 and I4 norms, as a convex separable nonsmooth unconstrained minimization problem, is considered as well Audience Advanced undergraduate and graduate students, mathematical programming operations research specialists
Separation process using microchannel technology
Tonkovich, Anna Lee; Perry, Steven T.; Arora, Ravi; Qiu, Dongming; Lamont, Michael Jay; Burwell, Deanna; Dritz, Terence Andrew; McDaniel, Jeffrey S.; Rogers, Jr.; William A.; Silva, Laura J.; Weidert, Daniel J.; Simmons, Wayne W.; Chadwell, G. Bradley
2009-03-24
The disclosed invention relates to a process and apparatus for separating a first fluid from a fluid mixture comprising the first fluid. The process comprises: (A) flowing the fluid mixture into a microchannel separator in contact with a sorption medium, the fluid mixture being maintained in the microchannel separator until at least part of the first fluid is sorbed by the sorption medium, removing non-sorbed parts of the fluid mixture from the microchannel separator; and (B) desorbing first fluid from the sorption medium and removing desorbed first fluid from the microchannel separator. The process and apparatus are suitable for separating nitrogen or methane from a fluid mixture comprising nitrogen and methane. The process and apparatus may be used for rejecting nitrogen in the upgrading of sub-quality methane.
Wastewater treatment with acoustic separator
Kambayashi, Takuya; Saeki, Tomonori; Buchanan, Ian
2017-07-01
Acoustic separation is a filter-free wastewater treatment method based on the forces generated in ultrasonic standing waves. In this report, a batch-system separator based on acoustic separation was demonstrated using a small-scale prototype acoustic separator to remove suspended solids from oil sand process-affected water (OSPW). By applying an acoustic separator to the batch use OSPW treatment, the required settling time, which was the time that the chemical oxygen demand (COD) decreased to the environmental criterion (<200 mg/L), could be shortened from 10 to 1 min. Moreover, for a 10 min settling time, the acoustic separator could reduce the FeCl3 dose as coagulant in OSPW treatment from 500 to 160 mg/L.
Hereditary separability in Hausdorff continua
Directory of Open Access Journals (Sweden)
D. Daniel
2012-04-01
Full Text Available We consider those Hausdorff continua S such that each separable subspace of S is hereditarily separable. Due to results of Ostaszewski and Rudin, respectively, all monotonically normal spaces and therefore all continuous Hausdorff images of ordered compacta also have this property. Our study focuses on the structure of such spaces that also possess one of various rim properties, with emphasis given to rim-separability. In so doing we obtain analogues of results of M. Tuncali and I. Loncar, respectively.
Tang, Malcolm S. Y.; Ng, Eng-Poh; Juan, Joon Ching; Ooi, Chien Wei; Ling, Tau Chuan; Woon, Kai Lin; Loke Show, Pau
2016-08-01
It is known that carbon nanotubes show desirable physical and chemical properties with a wide array of potential applications. Nonetheless, their potential has been hampered by the difficulties in acquiring high purity, chiral-specific tubes. Considerable advancement has been made in terms of the purification of carbon nanotubes, for instance chemical oxidation, physical separation, and myriad combinations of physical and chemical methods. The aqueous two-phase separation technique has recently been demonstrated to be able to sort carbon nanotubes based on their chirality. The technique requires low cost polymers and salt, and is able to sort the tubes based on their diameter as well as metallicity. In this review, we aim to provide a review that could stimulate innovative thought on the progress of a carbon nanotubes sorting method using the aqueous two-phase separation method, and present possible future work and an outlook that could enhance the methodology.
Method and device for ion mobility separations
Energy Technology Data Exchange (ETDEWEB)
Ibrahim, Yehia M.; Garimella, Sandilya V. B.; Smith, Richard D.
2017-07-11
Methods and devices for ion separations or manipulations in gas phase are disclosed. The device includes a single non-planar surface. Arrays of electrodes are coupled to the surface. A combination of RF and DC voltages are applied to the arrays of electrodes to create confining and driving fields that move ions through the device. The DC voltages are static DC voltages or time-dependent DC potentials or waveforms.
Separation of Pneumcoccal Capsular Polysaccharide BY Gel Extraction
Institute of Scientific and Technical Information of China (English)
Xu Xiaoping; Huang Xinghua; Li Zhongqin; Chen Jiebo
2004-01-01
Separation of pneumcoccal capsular polysaccharide by gel was investigated in this paper. The gels used here were poly(acrylamide-co-sodium methacrylate)gels and prepared by free radical polymerization in aqueous solution. The experimental results indicated that gel extraction is a potential method to separate pneumcoccal capsular polysaccharide from its dilute solution.
Fluorous Compounds and their Role in Separation Chemistry
Ubeda, Maria Angeles; Dembinski, Roman
2006-01-01
The main focus of fluorous chemistry targets resource and time-consuming separation, in order to improve the material economy and thus represents potentially environmentally friendly technology. Fluorous chemistry offers the advantage of easy separation based on different affirmatives of organics and fluorous molecules, where the process called…
Parental separation and pediatric cancer
DEFF Research Database (Denmark)
Grant, Sally; Carlsen, Kathrine; Bidstrup, Pernille Envold Hansen
2012-01-01
The purpose of this study was to determine the risk for separation (ending cohabitation) of the parents of a child with a diagnosis of cancer.......The purpose of this study was to determine the risk for separation (ending cohabitation) of the parents of a child with a diagnosis of cancer....
Fast Monaural Separation of Speech
DEFF Research Database (Denmark)
Pontoppidan, Niels Henrik; Dyrholm, Mads
2003-01-01
a Factorial Hidden Markov Model, with non-stationary assumptions on the source autocorrelations modelled through the Factorial Hidden Markov Model, leads to separation in the monaural case. By extending Hansens work we find that Roweis' assumptions are necessary for monaural speech separation. Furthermore we...
Metals Separation by Liquid Extraction.
Malmary, G.; And Others
1984-01-01
As part of a project focusing on techniques in industrial chemistry, students carry out experiments on separating copper from cobalt in chloride-containing aqueous solution by liquid extraction with triisoctylamine solvent and search the literature on the separation process of these metals. These experiments and the literature research are…
Vision 2020: 2000 Separations Roadmap
Energy Technology Data Exchange (ETDEWEB)
Adler, Stephen [Center for Waster Reduction Technologies; Beaver, Earl [Practical Sustainability; Bryan, Paul [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Robinson, Sharon [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Watson, Jack [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2000-01-01
This report documents the results of four workshops on the technology barriers, research needs, and priorities of the chemical, agricultural, petroleum, and pharmaceutical industries as they relate to separation technologies utilizing adsorbents, crystallization, distillation, extraction, membranes, separative reactors, ion exchange, bioseparations, and dilute solutions.
Electrostatically enhanced core separator system
Energy Technology Data Exchange (ETDEWEB)
Easom, B.H.; Smolensky, L.A.; Altman, R.F. [LSR Technologies, Inc., Acton, MA (United States)
1997-12-31
The Electrostatically Enhanced Core Separator (EECS) system employs the same design principles as the mechanical Core Separator system plus an electrostatic separation enhancing technique. The EECS system contains a special type of separator, the EECS element, a conventional solids collector and means for flow recirculation. In the EECS system solids separation and collection are accomplished in two different components. The EECS element acts as a separator, not as a collector so particles are not collected on its walls. This eliminates or at least mitigates the problems associated with reentrainment (due to high or low dust resistivity), seepage (due to gas flow below the precipitator plates and over the hoppers), sneakage (due to gas flow both above and below the precipitator plates), and rapping reentrainment. If the EECS separation efficiency is high enough, particles cannot leave the system with the process stream. They recirculate until they are extracted by the collector. As a result, the separation efficiency of the EECS element determines the efficiency of the system, even if the collector efficiency is relatively low. 8 refs., 3 figs.
Relational Parametricity and Separation Logic
DEFF Research Database (Denmark)
Birkedal, Lars; Yang, Hongseok
2008-01-01
Separation logic is a recent extension of Hoare logic for reasoning about programs with references to shared mutable data structures. In this paper, we provide a new interpretation of the logic for a programming language with higher types. Our interpretation is based on Reynolds's relational...... parametricity, and it provides a formal connection between separation logic and data abstraction. Udgivelsesdato: 2008...
Testing Orions Fairing Separation System
Martinez, Henry; Cloutier, Chris; Lemmon, Heber; Rakes, Daniel; Oldham, Joe; Schlagel, Keith
2014-01-01
Traditional fairing systems are designed to fully encapsulate and protect their payload from the harsh ascent environment including acoustic vibrations, aerodynamic forces and heating. The Orion fairing separation system performs this function and more by also sharing approximately half of the vehicle structural load during ascent. This load-share condition through launch and during jettison allows for a substantial increase in mass to orbit. A series of component-level development tests were completed to evaluate and characterize each component within Orion's unique fairing separation system. Two full-scale separation tests were performed to verify system-level functionality and provide verification data. This paper summarizes the fairing spring, Pyramidal Separation Mechanism and forward seal system component-level development tests, system-level separation tests, and lessons learned.
Separable Forces for $(d,p)$ Reactions in Momentum Space
Hlophe, L; Eremenko, V; Nunes, F M; Thompson, I J; Arbanas, G; Escher, J
2015-01-01
Treating $(d,p)$ reactions in a Faddeev-AGS framework requires the interactions in the sub-systems as input. We derived separable representations for the neutron- and proton-nucleus interactions from phenomenological global optical potentials. In order to take into account excitations of the nucleus, excitations need to be included explicity, leading to a coupled-channel separable representation of the optical potential.
Separable Forces for (d, p Reactions in Momentum Space
Directory of Open Access Journals (Sweden)
Hlophe L.
2016-01-01
Full Text Available Treating (d, p reactions in a Faddeev-AGS framework requires the interactions in the sub-systems as input. We derived separable representations for the neutron and proton-nucleus interactions from phenomenological global optical potentials. In order to take into account excitations of the nucleus, excitations need to be included explicitly, leading to a coupled-channel separable representation of the optical potential.
Separation of Oil from Wastewater by Column Flotation
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
A new type of device, a dissolved-air flotation column, was developed for separation of oily wastewater.The unique design idea of the dissolved-air flotation column is the combined use of dissolved-air flotation and column flotation.The dissolved air release occurred within the column separation system.As a potential application the column was investigated for its performance in separating emulsified oil droplets in oily wastewater.A high separation efficiency was obtained in a series of tests.The aeration performance of the bubble generator used in the dissolved-air flotation column was also studied in particular.
Linear $r$-matrix algebra for classical separable systems
Eilbeck, J C; Kuznetsov, V B; Tsiganov, A V; Kuznetsov, Vadim B.
1994-01-01
We consider a hierarchy of the natural type Hamiltonian systems of $n$ degrees of freedom with polynomial potentials separable in general ellipsoidal and general paraboloidal coordinates. We give a Lax representation in terms of $2\\times 2$ matrices for the whole hierarchy and construct the associated linear $r$-matrix algebra with the $r$-matrix dependent on the dynamical variables. A Yang-Baxter equation of dynamical type is proposed. Using the method of variable separation we provide the integration of the systems in classical mechanics conctructing the separation equations and, hence, the explicit form of action variables. The quantisation problem is discussed with the help of the separation variables.
Pseudo-stationary separation materials for highly parallel separations.
Energy Technology Data Exchange (ETDEWEB)
Singh, Anup K.; Palmer, Christopher (University of Montana, Missoula, MT)
2005-05-01
Goal of this study was to develop and characterize novel polymeric materials as pseudostationary phases in electrokinetic chromatography. Fundamental studies have characterized the chromatographic selectivity of the materials as a function of chemical structure and molecular conformation. The selectivities of the polymers has been studied extensively, resulting in a large body of fundamental knowledge regarding the performance and selectivity of polymeric pseudostationary phases. Two polymers have also been used for amino acid and peptide separations, and with laser induced fluorescence detection. The polymers performed well for the separation of derivatized amino acids, and provided some significant differences in selectivity relative to a commonly used micellar pseudostationary phase. The polymers did not perform well for peptide separations. The polymers were compatible with laser induced fluorescence detection, indicating that they should also be compatible with chip-based separations.
WASTE PRINTED CIRCUIT BOARDS SEPARATION IN ELECTROSTATIC SEPARATOR
Directory of Open Access Journals (Sweden)
Branimir Fuk
2012-12-01
Full Text Available Printed circuit boards from electronic waste are very important source of precious metals by recycling. The biggest challenge is liberation and separation of useful components; thin film which contains copper, zinc, tin, lead and precious metals like silver, gold and palladium from non useful components; polymers, ceramics and glass fibbers. The paper presents results for separation of shredded printed circuit boards from TV sets in electrostatic separator. Testing where conducted with material class 2/1 and 1/0.5 mm in laboratory on equipment for mineral processing. Results showed influence from independent variable; separation knife gradient, drum rotation speed and voltage on concentrate quality and recovery (the paper is published in Croatian.
Hydrogen isotope separation; Separation isotopique de l'hydrogene
Energy Technology Data Exchange (ETDEWEB)
Leterq, D.; Guidon, H. [CEA Bruyeres-le-Chatel, 91 (France)
2001-12-01
CEA-DAM has been operating for more than 20 years hydrogen isotopes separation by batch chromatography with palladium coated on alumina as absorbing material. The efforts have been focused on the development of two new separation processes: TCAP (Thermal Cycling Absorption Process) and chromatography an molecular sieve at 77 K. H{sub 2}/D{sub 2} first tests results are promising. (authors)
Particle separations by electrophoretic techniques
Energy Technology Data Exchange (ETDEWEB)
Ballou, N.E.; Petersen, S.L.; Ducatte, G.R.; Remcho, V.T.
1996-03-01
A new method for particle separations based on capillary electrophoresis has been developed and characterized. It uniquely separates particles according to their chemical nature. Separations have been demonstrated with chemically modified latex particles and with inorganic oxide and silicate particles. Separations have been shown both experimentally and theoretically to be essentially independent of particle size in the range of about 0.2 {mu}m to 10 {mu}m. The method has been applied to separations of U0{sub 2} particles from environmental particulate material. For this, an integrated method was developed for capillary electrophoretic separation, collection of separated fractions, and determinations of U0{sub 2} and environmental particles in each fraction. Experimental runs with the integrated method on mixtures of UO{sub 2} particles and environmental particulate material demonstrated enrichment factors of 20 for UO{sub 2} particles in respect to environmental particles in the U0{sub 2}containing fractions. This enrichment factor reduces the costs and time for processing particulate samples by the lexan process by a factor of about 20.
DEFF Research Database (Denmark)
Cervera Padrell, Albert Emili; Morthensen, Sofie Thage; Lewandowski, Daniel Jacob
2012-01-01
Continuous hydrolysis of an active pharmaceutical ingredient intermediate, and subsequent liquid–liquid (L-L) separation of the resulting organic and aqueous phases, have been achieved using a simple PTFE tube reactor connected to a miniscale hydrophobic membrane separator. An alkoxide product...... a PTFE membrane with 28 cm2 of active area. A less challenging separation of water and toluene was achieved at total flow rates as high as 80 mL/min, with potential to achieve even higher flow rates. The operability and flexibility of the membrane separator and a plate coalescer were compared...
Recycling of plastic waste by density separation: prospects for optimization.
Gent, Malcolm Richard; Menendez, Mario; Toraño, Javier; Diego, Isidro
2009-03-01
A review of existing industrial processing and results of alternative processing investigations for separating solid mixtures and specifically recycling plastic waste by density separation is presented. Media density separation is shown to be fundamental for separation and/or pre-concentration in the recycling of plastics. The current use of static media processes limits the capacity and size of material that can be treated commercially. Investigations have shown that the hydroscopic properties of plastics can be reduced to improve such separations. This indicates that an alternative processing method is required to increase the commercial recovery of recyclable plastics. Cylindroconical and cylindrical cyclone-type media separators, such as those used for processing coal, are reviewed and suggested as a potential substitute. Both have superior production capacities and are able to process a larger range in particle sizes treated. A summary of results of investigations with cyclone media devices for recycling plastics is presented.
Efficient separations & processing crosscutting program
Energy Technology Data Exchange (ETDEWEB)
NONE
1996-08-01
The Efficient Separations and Processing Crosscutting Program (ESP) was created in 1991 to identify, develop, and perfect chemical and physical separations technologies and chemical processes which treat wastes and address environmental problems throughout the DOE complex. The ESP funds several multiyear tasks that address high-priority waste remediation problems involving high-level, low-level, transuranic, hazardous, and mixed (radioactive and hazardous) wastes. The ESP supports applied research and development (R & D) leading to the demonstration or use of these separations technologies by other organizations within the Department of Energy (DOE), Office of Environmental Management.
Membrane separation systems---A research and development needs assessment
Energy Technology Data Exchange (ETDEWEB)
Baker, R.W. (Membrane Technology and Research, Inc., Menlo Park, CA (USA)); Cussler, E.L. (Minnesota Univ., Minneapolis, MN (USA). Dept. of Chemical Engineering and Materials Science); Eykamp, W. (California Univ., Berkeley, CA (USA)); Koros, W.J. (Texas Univ., Austin, TX (USA)); Riley, R.L. (Separation Systems Technology, San Diego, CA (USA)); Strathmann, H. (Fraunhofer-Institut fuer Grenzflaech
1990-03-01
Membrane based separation technology, a relative newcomer on the separations scene, has demonstrated the potential of saving enormous amounts of energy in the processing industries if substituted for conventional separation systems. Over 1 quad annually, out of 2.6, can possibly be saved in liquid-to-gas separations, alone, if membrane separation systems gain wider acceptance, according to a recent DOE/OIP (DOE/NBM-80027730 (1986)) study. In recent years great strides have been made in the field and offer even greater energy savings in the future when substituted for other conventional separation techniques such as distillation, evaporation, filtration, sedimentation, and absorption. An assessment was conducted by a group of six internationally known membrane separations experts who examined the worldwide status of research in the seven major membrane areas. This encompassed four mature technology areas: reverse osmosis, micorfiltration, ultrafiltration, and electrodialysis; two developing areas: gas separation and and pervaporation; and one emerging technology: facilitated transport. Particular attention was paid to identifying the innovative processes currently emerging, and even further improvements which could gain wider acceptance for the more mature membrane technology. The topics that were pointed out as having the greatest research emphasis are pervaporation for organic-organic separations; gas separation; micorfiltration; an oxidant-resistant reverse osmosis membrane; and a fouling-resistant ultrafiltration membrane. 35 refs., 6 figs., 22 tabs.
Lunar Soil Particle Separator Project
National Aeronautics and Space Administration — The Lunar Soil Particle Separator (LSPS) is an innovative method to beneficiate soil prior to in-situ resource utilization (ISRU). The LSPS improves ISRU oxygen...
Selective Photoinitiated Electrophoretic Separator Project
National Aeronautics and Space Administration — To address NASA Johnson Space Center needs for gas separation and collection technology for lunar in-situ resource utilization, Physical Optics Corporation (POC)...
Magnetic separation in microfluidic systems
DEFF Research Database (Denmark)
Smistrup, Kristian
2007-01-01
This Ph.D. thesis presents theory, modeling, design, fabrication, experiments and results for microfluidic magnetic separators. A model for magnetic bead movement in a microfluidic channel is presented, and the limits of the model are discussed. The effective magnetic field gradient is defined...... for fabrication of silicon based systems. This fabrication scheme is explained, and it is shown how, it is applied with variations for several designs of magnetic separators. An experimental setup for magnetic separation experiments has been developed. It has been coupled with an image analysis program....... It is shown conceptually how such a system can be applied for parallel biochemical processing in a microfluidic system. ’Passive’ magnetic separators are presented, where on-chip soft magnetic elements are magnetized by an external magnetic field and create strong magnetic fields and gradients inside...
Chiral separation of agricultural fungicides.
Pérez-Fernández, Virginia; García, Maria Ángeles; Marina, Maria Luisa
2011-09-23
Fungicides are very important and diverse environmental and agricultural concern species. Their determination in commercial formulations or environmental matrices, requires highly efficient, selective and sensitive methods. A significant number of these chemicals are chiral with the activity residing usually in one of the enantiomers. The different toxicological and degradation behavior observed in many cases for fungicide enantiomers, results in the need to investigate them separately. For this purpose, separation techniques such as GC, HPLC, supercritical fluid chromatography (SFC) and CE have widely been employed although, at present, HPLC still dominates chromatographic chiral analysis of fungicides. This review covers the literature concerning the enantiomeric separation of fungicides usually employed in agriculture grouping the chiral separation methodologies developed for their analysis in environmental, biological, and food samples.
Lunar Soil Particle Separator Project
National Aeronautics and Space Administration — The Lunar Soil Particle Separator (LSPS) is an innovative method to beneficiate soil prior to in-situ resource utilization (ISRU). The LSPS can improve ISRU oxygen...
Directory of Open Access Journals (Sweden)
Rajaonarivony Rova Karine
2017-01-01
Full Text Available In a dry biorefinery scheme, the separation of plant materials into powders rich in the constituents of interest is a crucial step. In recent years, electrostatic separation of agri-resources has sparked a growing interest for its potentialities, but optimization efforts remain to be done especially in case of fine powders. In this study a custom-designed corona-electrostatic separator has been built and its usage for the separation of mineral (ash from rice husk and vegetal powders (cellulose fibers with different particle size distributions has been studied. First, the powders have been characterized by their electric charge decay curves and their behaviour on the separator was studied. At a second time, separation tests have been carried out with blends of these two powders, and with native, finely ground, rice husk powder (constituted of both mineral and vegetal particles. In each case, the efficiency of the process was evaluated.
Rajaonarivony, Rova Karine; Rouau, Xavier; Dascalescu, Lucien; Mayer-Laigle, Claire
2017-06-01
In a dry biorefinery scheme, the separation of plant materials into powders rich in the constituents of interest is a crucial step. In recent years, electrostatic separation of agri-resources has sparked a growing interest for its potentialities, but optimization efforts remain to be done especially in case of fine powders. In this study a custom-designed corona-electrostatic separator has been built and its usage for the separation of mineral (ash from rice husk) and vegetal powders (cellulose fibers) with different particle size distributions has been studied. First, the powders have been characterized by their electric charge decay curves and their behaviour on the separator was studied. At a second time, separation tests have been carried out with blends of these two powders, and with native, finely ground, rice husk powder (constituted of both mineral and vegetal particles). In each case, the efficiency of the process was evaluated.
Separators for Lithium Ion Batteries
Institute of Scientific and Technical Information of China (English)
G.C.Li; H.P.Zhang; Y.P.Wu
2007-01-01
1 Results A separator for rechargeable batteries is a microporous membrane placed between electrodes of opposite polarity, keeping them apart to prevent electrical short circuits and at the same time allowing rapid transport of lithium ions that are needed to complete the circuit during the passage of current in an electrochemical cell, and thus plays a key role in determining the performance of the lithium ion battery. Here provides a comprehensive overview of various types of separators for lithium io...
Lithium isotope separation by laser
Energy Technology Data Exchange (ETDEWEB)
Arisawa, T.; Maruyama, Y.; Suzuki, Y.; Shiba, K.
1982-01-01
A lithium isotope separation was performed using a laser isotope separation method. It was found that the lithium atoms with a natural isotopic abundance enhanced its /sup 6/Li concentration up to over 90% by tuning the laser wavelength to the /sup 2/Psub(1/2) of /sup 6/Li. Too high power, however, leads to a loss of enrichment due to the power broadening effect which was analysed by the equation of motion of density matrices.
Development of Radiochemical Separation Technology
Energy Technology Data Exchange (ETDEWEB)
Lee, Eil Hee; Kim, K. W.; Yang, H. B. (and others)
2007-06-15
This project of the second phase was aimed at the development of basic unit technologies for advanced partitioning, and the application tests of pre-developed partitioning technologies for separation of actinides by using a simulated multi-component radioactive waste containing Am, Np, Tc, U and so on. The goals for recovery yield of TRU, and for purity of Tc are high than 99% and about 99%, respectively. The work scopes and contents were as follows. 1). For the development of basic unit technologies for advanced partitioning. 1. Development of technologies for co-removal of TRU and for mutual separation of U and TRU with a reduction-complexation reaction. 2. Development of extraction system for high-acidity co-separation of An(+3) and Ln(+3) and its radiolytic evaluation. 3. Synthesis of extractants for the selective separation of An(+3) and its relevant extraction system development. 4. Development of a hybrid system for the recovery of noble metals and its continuous separation tests. 5. Development of electrolytic system for the decompositions of N-NO3 and N-NH3 compounds to nitrogen gas. 2). For the application test of pre-developed partitioning technologies for the separation of actinide elements in a simulated multi-component solution equivalent to HLW level. 1. Co-separation of Tc, Np and U by a (TBP-TOA)/NDD system. 2. Mutual-separation of Am, Cm and RE elements by a (Zr-DEHPA)/NDD system. All results will be used as the fundamental data for the development of advanced partitioning process in the future.
Energy Technology Data Exchange (ETDEWEB)
Balestrini, S.J.
1981-07-01
The ion optics of an existing mass separator are documented. The elctrostatic and magnetic stages are analyzed theoretically, both separately and in combination, by paying particular attention to the ion trajectories, the linear and angular magnifications, and the dispersion. The possibility of converting the magnet into a tunable unit by means of current-carrying elements in the gap is demonstrated. The feasibility of correction coils constructed from printed circuit board is shown.
Sustainable process design & analysis of hybrid separations
DEFF Research Database (Denmark)
Kumar Tula, Anjan; Befort, Bridgette; Garg, Nipun
2016-01-01
Distillation is an energy intensive operation in chemical process industries. There are around 40,000 distillation columns in operation in the US, requiring approximately 40% of the total energy consumption in US chemical process industries. However, analysis of separations by distillation has...... shown that more than 50% of energy is spent in purifying the last 5-10% of the distillate product. Membrane modules on the other hand can achieve high purity separations at lower energy costs, but if the flux is high, it requires large membrane area. A hybrid scheme where distillation and membrane...... modules are combined such that each operates at its highest efficiency, has the potential for significant energy reduction without significant increase of capital costs. This paper presents a method for sustainable design of hybrid distillation-membrane schemes with guaranteed reduction of energy...
UPGRADING NATURAL GAS VIA MEMBRANE SEPARATION PROCESSES
Energy Technology Data Exchange (ETDEWEB)
S.A.Stern; P.A. Rice; J. Hao
2000-03-01
The objective of the present study is to assess the potential usefulness of membrane separation processes for removing CO{sub 2} and H{sub 2}S from low-quality natural gas containing substantial amounts of both these ''acid'' gases, e.g., up to 40 mole-% CO{sub 2} and 10 mole-% H{sub 2}S. The membrane processes must be capable of upgrading the crude natural gas to pipeline specifications ({le} 2 mole-% CO{sub 2}, {le} 4 ppm H{sub 2}S). Moreover, these processes must also be economically competitive with the conventional separation techniques, such as gas absorption, utilized for this purpose by the gas industry.
Separation mechanisms and fluid flow in oil/water separation
Energy Technology Data Exchange (ETDEWEB)
Celius, H.K.; Knudsen, B. [IKU Petroleumsforskning A/S, Trondheim (Norway); Hafskjold, B.; Hansen, E.W. [Selskapet for Industriell og Teknisk Forskning, Trondheim (Norway)
1996-12-31
This paper describes work aimed at physical and numerical modeling of separation rates of oil/water systems in order to establish better tools for design and operation of offshore operators. This work aims to integrate the chemical and physical phenomena behind coalescence and settling with those of fluid flow in the system, in order to develop tools for design and operational analysis of separation equipment. The work includes the development of a high pressure, bench-scale test rig to perform separation tests on live oil and water samples, and a rationale in the form of a computer code that can be used to interpret the test results and transform them to a form siutable for operational purposes. This involves a formulation of a mathematical description of the chemical and physical mechanisms behind the emulsification and separation process, and to establish a link to the hydrdynamic properties of the separator vessel. The Emucol computer program is used in the analysis. 12 refs., 5 figs.
Chromatographic Separations of Enantiomers and Underivatized Oligosaccharides
Energy Technology Data Exchange (ETDEWEB)
Ying Liu
2004-12-19
My graduate research has focused on separation science and bioanalytical analysis, which emphasized in method development. It includes three major areas: enantiomeric separations using high performance liquid chromatography (HPLC), Super/subcritical fluid chromatography (SFC), and capillary electrophoresis (CE); drug-protein binding behavior studies using CE; and carbohydrate analysis using liquid chromatograph-electrospray ionization mass spectrometry (LC-ESI-MS). Enantiomeric separations continue to be extremely important in the pharmaceutical industry. An in-depth evaluation of the enantiomeric separation capabilities of macrocyclic glycopeptides CSPs with SFC mobile phases was investigated using a set of over 100 chiral compounds. It was found that the macrocyclic based CSPs were able to separate enantiomers of various compounds with different polarities and functionalities. Seventy percent of all separations were achieved in less than 4 min due to the high flow rate (4.0 ml/min) that can be used in SFC. Drug-protein binding is an important process in determining the activity and fate of a drug once it enters the body. Two drug/protein systems have been studied using frontal analysis CE method. More sensitive fluorescence detection was introduced in this assay, which overcame the problem of low sensitivity that is common when using UV detection for drug-protein studies. In addition, the first usage of an argon ion laser with 257 nm beam coupled with CCD camera as a frontal analysis detection method enabled the simultaneous observation of drug fluorescence as well as the protein fluorescence. LC-ESI-MS was used for the separation and characterization of underivatized oligosaccharide mixtures. With the limits of detection as low as 50 picograms, all individual components of oligosaccharide mixtures (up to 11 glucose-units long) were baseline resolved on a Cyclobond I 2000 column and detected using ESI-MS. This system is characterized by high chromatographic
Chromatographic Separations of Enantiomers and Underivatized Oligosaccharides
Energy Technology Data Exchange (ETDEWEB)
Liu, Ying [Iowa State Univ., Ames, IA (United States)
2004-01-01
My graduate research has focused on separation science and bioanalytical analysis, which emphasized in method development. It includes three major areas: enantiomeric separations using high performance liquid chromatography (HPLC), Super/subcritical fluid chromatography (SFC), and capillary electrophoresis (CE); drug-protein binding behavior studies using CE; and carbohydrate analysis using liquid chromatograph-electrospray ionization mass spectrometry (LC-ESI-MS). Enantiomeric separations continue to be extremely important in the pharmaceutical industry. An in-depth evaluation of the enantiomeric separation capabilities of macrocyclic glycopeptides CSPs with SFC mobile phases was investigated using a set of over 100 chiral compounds. It was found that the macrocyclic based CSPs were able to separate enantiomers of various compounds with different polarities and functionalities. Seventy percent of all separations were achieved in less than 4 min due to the high flow rate (4.0 ml/min) that can be used in SFC. Drug-protein binding is an important process in determining the activity and fate of a drug once it enters the body. Two drug/protein systems have been studied using frontal analysis CE method. More sensitive fluorescence detection was introduced in this assay, which overcame the problem of low sensitivity that is common when using UV detection for drug-protein studies. In addition, the first usage of an argon ion laser with 257 nm beam coupled with CCD camera as a frontal analysis detection method enabled the simultaneous observation of drug fluorescence as well as the protein fluorescence. LC-ESI-MS was used for the separation and characterization of underivatized oligosaccharide mixtures. With the limits of detection as low as 50 picograms, all individual components of oligosaccharide mixtures (up to 11 glucose-units long) were baseline resolved on a Cyclobond I 2000 column and detected using ESI-MS. This system is characterized by high chromatographic
Separation of non-ferrous metals from ASR by corona electrostatic separation
Kim, Yang-soo; Choi, Jin-Young; Jeon, Ho-Seok; Han, Oh-Hyung; Park, Chul-Hyun
2016-04-01
Automotive shredder residue (ASR), the residual fraction of approximate 25% obtained after dismantling and shredding from waste car, consists of polymers (plastics and rubber), metals (ferrous and non-ferrous), wood, glass and fluff (textile and fiber). ASR cannot be effectively separated due to its heterogeneous materials and coated or laminated complexes and then largely deposited in land-fill sites as waste. Thus reducing a pollutant release before disposal, techniques that can improve the liberation of coated (or laminated) complexes and the recovery of valuable metals from the shredder residue are needed. ASR may be separated by a series of physical processing operations such as comminution, air, magnetic and electrostatic separations. The work deals with the characterization of the shredder residue coming from an industrial plant in korea and focuses on estimating the optimal conditions of corona electrostatic separation for improving the separation efficiency of valuable non-ferrous metals such as aluminum, copper and etc. From the results of test, the maximum separation achievable for non-ferrous metals using a corona electrostatic separation has been shown to be recovery of 92.5% at a grade of 75.8%. The recommended values of the process variables, particle size, electrode potential, drum speed, splitter position and relative humidity are -6mm, 50 kV, 35rpm, 20° and less 40%, respectively. Acknowledgments This study was supported by the R&D Center for Valuable Recycling (Global-Top R&BD Program) of the Ministry of Environment. (Project No. GT-11-C-01-170-0)
An Investigation into Separation of Impurity from Saffron Stigma Using an Electrostatic Separator
Directory of Open Access Journals (Sweden)
H Mortezapour
2015-03-01
Full Text Available In the present study, a laboratory electrostatic separator was constructed and its separation potential of white saffron impurities from stigma was investigated. The device was comprised of a nylon ribbon which moves in contact with a woolen brush and was charged by the triboelectric effect. The charged ribbon, then, moved over the material pan. Since the electrostatic behavior vary from various materials, their attraction to the ribbon differ. The separation tests were conducted at three levels of ribbon position (with 1.5, 2.5 and 3.5 cm from the material pan, three drum speeds (50, 60 and 70 rpm and three working times (120, 18 and 240 seconds. The results showed that material absorption increased as working time increased and the ribbon distance decreased. Meanwhile, rising the speed from 50 to 60 rpm improved material absorption while, more increasing from 60 to 70 rpm reduced the absorption. A maximum impurity separation of 97% was observed with ribbon distance of 1.5 cm, ribbon speed of 60 rpm and working for 240 seconds. The minimum stigma losses were found to be about 2% when the ribbon distance and speed were 3.5 cm and 70 rpm, respectively, and the separator worked for 120 seconds.
Membrane manufacture for peptide separations
Kim, Dooli
2016-06-07
Nanostructured polymeric membranes are key tools in biomedical applications such as hemodialysis, protein separations, in the food industry, and drinking water supply from seawater. Despite of the success in different separation processes, membrane manufacture itself is at risk, since the most used solvents are about to be banned in many countries due to environmental and health issues. We propose for the first time the preparation of polyethersulfone membranes based on dissolution in the ionic liquid 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM]DEP). We obtained a series of membranes tailored for separation of solutes with molecular weight of 30, 5, 1.3, and 1.25 kg mol-1 with respective water permeances of 140, 65, 30 and 20 Lm-2h-1bar-1. We demonstrate their superior efficiency in the separation of complex mixtures of peptides with molecular weights in the range of 800 to 3500 gmol-1. Furthermore, the thermodynamics and kinetics of phase separation leading to the pore formation in the membranes were investigated. The rheology of the solutions and the morphology of the prepared membranes were examed and compared to those of polyethersulfone in organic solvents currently used for membrane manufacture.
Tidal flow separation at protruding beach nourishments
Rademacher, Max; de Schipper, Matthieu A.; Swinkels, Cilia; MacMahan, Jamie H.; Reniers, Ad J.H.M.
2017-01-01
The article of record as published may be found at http://dx.doi.org/10.1002/2016JC011942 In recent years, the application of large-scale beach nourishments has been discussed, with the Sand Motor in the Netherlands as the first real-world example. Such protruding beach nourishments have an impact on tidal currents, potentially leading to tidal flow separation and the generation of tidal eddies of length scales larger than the nourishment itself. The present study examines the cha...
The Signal Space Separation method
Taulu, S; Simola, J; Taulu, Samu; Kajola, Matti; Simola, Juha
2004-01-01
Multichannel measurement with hundreds of channels essentially covers all measurable degrees of freedom of a curl and source free vector field, like the magnetic field in a volume free of current sources (e.g. in magnetoencephalography, MEG). A functional expansion solution of Laplace's equation enables one to separate signals arising from the sphere enclosing the interesting sources, e.g. the currents in the brain, from the rest of the signals. The signal space separation (SSS) is accomplished by calculating individual basis vectors for each term of the functional expansion solution to create a signal basis covering all measurable signal vectors. Any signal vector has a unique SSS decomposition with separate coefficients for the interesting signals and signals coming from outside the interesting volume. Thus, SSS basis provides an elegant method to remove external disturbances, and to transform the interesting signals to virtual sensor configurations. SSS can also be used in compensating the movements of the...
Rare Earth Separation in China
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
During the last decade, China rare earth (RE) industry has made significant progress and become one of the most important producers in the world. In this paper, the recent developments in both fundamental research and industrial application are briefly reviewed: (1) the development and application of Theory of Countercurrent Extraction, (2) the novel solvent extraction process and its application in industry for separating heavy rare earth elements (Tm, Yb, Lu), yttrium (Y), and scandium (Sc), (3) the on-line analysis and automatic control of countercurrent extraction, (4) the eco-friendly process for RE/Th separation of bastnasite in Sichuan Province and electrochemical process for Eu/RE separation, and (5) the optimized flowcharts for typical rare earth minerals in China.
PT Symmetry in Classical and Quantum Statistical Mechanics
Meisinger, Peter N
2012-01-01
PT-symmetric Hamiltonians and transfer matrices arise naturally in statistical mechanics. These classical and quantum models often require the use of complex or negative weights and thus fall outside of the conventional equilibrium statistical mechanics of Hermitian systems. PT-symmetric models form a natural class where the partition function is necessarily real, but not necessarily positive. The correlation functions of these models display a much richer set of behaviors than Hermitian systems, displaying sinusoidally-modulated exponential decay, as in a dense fluid, or even sinusoidal modulation without decay. Classical spin models with PT symmetry include Z(N) models with a complex magnetic field, the chiral Potts model and the anisotropic next-nearest-neighbor Ising (ANNNI) model. Quantum many-body problems with a non-zero chemical potential have a natural PT-symmetric representation related to the sign problem. Two-dimensional QCD with heavy quarks at non-zero chemical potential can be solved by diagona...
Taming the Exceptional Points of Parity-Time Symmetric Acoustics
Dubois, Marc; Shi, Chengzhi; Chen, Yun; Cheng, Lei; Ramezani, Hamidreza; Wang, Yuan; Zhang, Xiang
Parity-time (PT) symmetric concept and development lead to a wide range of applications including coherent perfect absorbers, single mode lasers, unidirectional cloaking and sensing, and optical isolators. These new applications and devices emerge from the existence of a phase transition in PT symmetric complex-valued potential obtained by balancing gain and loss materials. However, the systematic extension of such devices is adjourned by the key challenge in the management of the complex scattering process within the structure in order to engineer PT phase and exceptional points. Here, based on active acoustic elements, we experimentally demonstrate the simultaneous control of complex-valued potentials and multiple interference inside the structure at any given frequency. This method broadens the scope of applications for PT symmetric devices in many fields including optics, microwaves, electronics, which are crucial for sensing, imaging, cloaking, lasing, absorbing, etc.
Thermographic Detection of separated Flow
Dollinger, C.; Balaresque, N.; Schaffarczyk, A. P.; Fischer, A.
2016-09-01
Thermographic wind tunnel measurements, both on a cylinder as well as on a 2D airfoil, were performed at various Reynolds numbers in order to evaluate the possibility of detecting and visualizing separated flow areas. A new approach by acquiring a series of thermographic images and applying a spatial-temporal statistical analysis allows improving both the resolution and the information content of the thermographic images. Separated flow regions become visible and laminar/turbulent transitions can be detected more accurately. The knowledge about possibly present stall cells can be used to confirm two-dimensional flow conditions and support the development of more effective and silent rotorblades.
Separation processes, I: Azeotropic rectification
Directory of Open Access Journals (Sweden)
Milojević Svetomir
2005-01-01
Full Text Available In a series of two articles, the problems of azeotrope separation (part I and the design of separation units (part II were analyzed. The basic definition and equations of vapour-liquid equilibria for ideal and non-ideal systems, the importance of the activity coefficient calculation necessary for the analysis of non-ideal equilibrium systems, as well as theoretical aspects of azeotrope rectification and the determination of the optimal third component (modifier or azeotrope agent are presented in the first part.
Separation and confirmation of showers
Neslušan, L.; Hajduková, M.
2017-01-01
Aims: Using IAU MDC photographic, IAU MDC CAMS video, SonotaCo video, and EDMOND video databases, we aim to separate all provable annual meteor showers from each of these databases. We intend to reveal the problems inherent in this procedure and answer the question whether the databases are complete and the methods of separation used are reliable. We aim to evaluate the statistical significance of each separated shower. In this respect, we intend to give a list of reliably separated showers rather than a list of the maximum possible number of showers. Methods: To separate the showers, we simultaneously used two methods. The use of two methods enables us to compare their results, and this can indicate the reliability of the methods. To evaluate the statistical significance, we suggest a new method based on the ideas of the break-point method. Results: We give a compilation of the showers from all four databases using both methods. Using the first (second) method, we separated 107 (133) showers, which are in at least one of the databases used. These relatively low numbers are a consequence of discarding any candidate shower with a poor statistical significance. Most of the separated showers were identified as meteor showers from the IAU MDC list of all showers. Many of them were identified as several of the showers in the list. This proves that many showers have been named multiple times with different names. Conclusions: At present, a prevailing share of existing annual showers can be found in the data and confirmed when we use a combination of results from large databases. However, to gain a complete list of showers, we need more-complete meteor databases than the most extensive databases currently are. We also still need a more sophisticated method to separate showers and evaluate their statistical significance. Tables A.1 and A.2 are also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc
Barriers in Concurrent Separation Logic
Hobor, Aquinas; Gherghina, Cristian
We develop and prove sound a concurrent separation logic for Pthreads-style barriers. Although Pthreads barriers are widely used in systems, and separation logic is widely used for verification, there has not been any effort to combine the two. Unlike locks and critical sections, Pthreads barriers enable simultaneous resource redistribution between multiple threads and are inherently stateful, leading to significant complications in the design of the logic and its soundness proof. We show how our logic can be applied to a specific example program in a modular way. Our proofs are machine-checked in Coq.
Convolutive Blind Source Separation Methods
DEFF Research Database (Denmark)
Pedersen, Michael Syskind; Larsen, Jan; Kjems, Ulrik
2008-01-01
During the past decades, much attention has been given to the separation of mixed sources, in particular for the blind case where both the sources and the mixing process are unknown and only recordings of the mixtures are available. In several situations it is desirable to recover all sources from....... This may help practitioners and researchers new to the area of convolutive source separation obtain a complete overview of the field. Hopefully those with more experience in the field can identify useful tools, or find inspiration for new algorithms....
Novel, Ceramic Membrane System For Hydrogen Separation
Energy Technology Data Exchange (ETDEWEB)
Elangovan, S.
2012-12-31
Separation of hydrogen from coal gas represents one of the most promising ways to produce alternative sources of fuel. Ceramatec, teamed with CoorsTek and Sandia National Laboratories has developed materials technology for a pressure driven, high temperature proton-electron mixed conducting membrane system to remove hydrogen from the syngas. This system separates high purity hydrogen and isolates high pressure CO{sub 2} as the retentate, which is amenable to low cost capture and transport to storage sites. The team demonstrated a highly efficient, pressure-driven hydrogen separation membrane to generate high purity hydrogen from syngas using a novel ceramic-ceramic composite membrane. Recognizing the benefits and limitations of present membrane systems, the all-ceramic system has been developed to address the key technical challenges related to materials performance under actual operating conditions, while retaining the advantages of thermal and process compatibility offered by the ceramic membranes. The feasibility of the concept has already been demonstrated at Ceramatec. This project developed advanced materials composition for potential integration with water gas shift rectors to maximize the hydrogenproduction.
The application of the electrodynamic separator in minerals beneficiation
Skowron, M.; Syrek, P.; Surowiak, A.
2017-05-01
The aim of presented paper is elaboration of methodology of upgrading natural minerals in example of chalcocite and bornite sample. The results were obtained by means of laboratory drum separator. This device operates in accordance to properties of materials, which in this case was electrical conductivity. The study contains the analysis of the forces occurring inside of electrodynamic separator chamber, that act on the particles of various electrical properties. Both, the potential and electric field strength distributions were calculated, with set of separators setpoints. Theoretical analysis influenced on separator parameters, and hence impacted the empirical results too. Next, the authors conducted empirical research on chalcocite and bornite beneficiation by means of electrodynamic separation. The results of this process were shown graphically in form of upgrading curves of chalcocite considering elementary copper and lead.
Protonated Melamine Sponge for Effective Oil/Water Separation
Wang, Chih-Feng; Huang, Hsiang-Ching; Chen, Liang-Ting
2015-09-01
In this study, we fabricated a superhydrophilic and underwater superoleophobic protonated melamine sponge for effective separation of water-rich immiscible oil/water mixtures with extremely high separation efficiency. This protonated melamine sponge exhibited excellent antifouling properties and could be used to separate oil/water mixtures continuously for up to 12 h without any increase in the oil content in filtrate. Moreover, our compressed protonated melamine sponge could separate both surfactant-free and -stabilized oil-in-water emulsions with high separation efficiencies. The high performance of this protonated melamine sponge and its efficient, energy- and cost-effective preparation suggest that it has great potential for use in practical applications.
Clean separation technologies of rare earth resources in China
Institute of Scientific and Technical Information of China (English)
LIAO Chunsheng; WU Sheng; CHENG Fuxiang; WANG Songling; LIU Yan; ZHANG Bo; YAN Chunhua
2013-01-01
After a review on the conventional separation process of rare earths (RE),hyperlink extraction technology was introduced and a potential process was proposed for clean separation of RE.A great amount of acid,base and water was consumed in the conventional RE separation process which included the procedures of raw material dissolving,extraction separation and precipitation.Therefore hyperlink extraction technology had been developed,by which the repeated consumption of acid and base could be avoided during the extraction process.And based on the theory and successful applications of the hyperlink extraction technology,we proposed the integral hyperlink process in which the intermediate acid resulted in individual procedures would be recycled and reused after being treated.The proposed process would make it feasible to consume no chemicals except for oxalic acid,and so could be a promising clean separation technology with a significant reduction on consumption and emission.
Environmental Consequences of Future Biogas Technologies based on Separated Slurry
DEFF Research Database (Denmark)
Hamelin, Lorie; Wesnæs, Marianne; Wenzel, Henrik
2011-01-01
the volatile solids in the solid fraction. The biogas scenario involving the most efficient separation technology resulted in a dry matter separation efficiency of 87% and allowed a net reduction of the global warming potential of 40%, compared to the reference slurry management. This figure comprises......This consequential life cycle assessment study highlights the key environmental aspects of producing biogas from separated pig and cow slurry, a relatively new but probable scenario for future biogas production, as it avoids the reliance on constrained carbon cosubstrates. Three scenarios involving...... different slurry separation technologies have been assessed and compared to a business-as-usual reference slurry management scenario. The results show that the environmental benefits of such biogas production are highly dependent upon the efficiency of the separation technology used to concentrate...
Enabling Concise and Modular Specifications in Separation Logic
DEFF Research Database (Denmark)
Jensen, Jonas Buhrkal
2014-01-01
Separation logic is an extension of Hoare logic for reasoning about programs that use pointers or references to potentially-shared data. The problem with such programs, both in formal proofs and in informal understanding of them, is to know not only what data they change but also to know what data...... they leave unmodified. Separation logic has one simple general answer to this, known as the frame rule; it intuitively says that all data that is disjoint from the minimal footprint of the program will be unmodified. This thesis is a collection of papers with the common theme of presenting new separation...... logics and examples of using these logics to verify challenging programs. The article Modular Verification of Linked Lists with Views via Separation Logic reports on verification of a practical data structure with separation logic. The challenges identified in this work has served as motivation for later...
Magnetic separation apparatus and methods
Tibbe, Arjan; Scholtens, Tycho M.; Terstappen, Leon W.M.M.
2010-01-01
Apparatuses and methods for separating, immobilizing, and quantifying biological substances from within a fluid medium. Biological substances are observed by employing a vessel (6) having a chamber therein, the vessel comprising a transparent collection wall (5). A high internal gradient magnetic ca
Separating Device for solid Particles
De Jong, T.P.R.; Kattentidt, H.U.R.; Schokker, E.A.
2001-01-01
The invention relates to a separating device for solid fragments, comprising a conveyor belt for supplying the fragments, at least one sensor for detecting the fragments, and an ejector for dislodging the fragments from the belt. The ejector is embodied as mechanical impulse-transmitting organ opera
Operation of Electromagnetic Isotope Separator
Institute of Scientific and Technical Information of China (English)
MI; Ya-jing
2015-01-01
In 2015,we mainly completed the installation of the electromagnetic isotope separator comprehensive technical transformation projects,including the work of installation,debugging,commissioning and acceptance.In June 30,2015,according to the schedule requirements,the project
33rd Actinide Separations Conference
Energy Technology Data Exchange (ETDEWEB)
McDonald, L M; Wilk, P A
2009-05-04
Welcome to the 33rd Actinide Separations Conference hosted this year by the Lawrence Livermore National Laboratory. This annual conference is centered on the idea of networking and communication with scientists from throughout the United States, Britain, France and Japan who have expertise in nuclear material processing. This conference forum provides an excellent opportunity for bringing together experts in the fields of chemistry, nuclear and chemical engineering, and actinide processing to present and discuss experiences, research results, testing and application of actinide separation processes. The exchange of information that will take place between you, and other subject matter experts from around the nation and across the international boundaries, is a critical tool to assist in solving both national and international problems associated with the processing of nuclear materials used for both defense and energy purposes, as well as for the safe disposition of excess nuclear material. Granlibakken is a dedicated conference facility and training campus that is set up to provide the venue that supports communication between scientists and engineers attending the 33rd Actinide Separations Conference. We believe that you will find that Granlibakken and the Lake Tahoe views provide an atmosphere that is stimulating for fruitful discussions between participants from both government and private industry. We thank the Lawrence Livermore National Laboratory and the United States Department of Energy for their support of this conference. We especially thank you, the participants and subject matter experts, for your involvement in the 33rd Actinide Separations Conference.
Working inside an electrostatic separator
1980-01-01
This type of separators with electrodes of a length of 2 m and a field of 100 kV/cm were still in use for secondary beams in the East Hall at the PS. Michel Zahnd is on foreground, left, and Pierre Simon on background, right.
Development of Separator for Soybeans
Vries, de H.C.P.; Rijpma, P.J.; Owaa, J.S.E.
1997-01-01
A simple and effective separator for soybeans was developed for small-scale farmers in Uganda, to clean the seeds from foreign material, chaff, broken beans etc. as demanded by local and world markets. It will help to avoid losses during post-harvest time and to reduce human drudgery of cleaning the
Separation technology 2005; Separasjonsteknologi 2005
Energy Technology Data Exchange (ETDEWEB)
NONE
2005-07-01
The conference comprises 13 presentations on the topics of separation technology aspects with emphasis on technology assessment. Some topics of particular interest are emulsion stabilization, sand technology and handling, water handling and reservoir injection, technical equipment and compression and pressure aspects.
Separating proteins with activated carbon.
Stone, Matthew T; Kozlov, Mikhail
2014-07-15
Activated carbon is applied to separate proteins based on differences in their size and effective charge. Three guidelines are suggested for the efficient separation of proteins with activated carbon. (1) Activated carbon can be used to efficiently remove smaller proteinaceous impurities from larger proteins. (2) Smaller proteinaceous impurities are most efficiently removed at a solution pH close to the impurity's isoelectric point, where they have a minimal effective charge. (3) The most efficient recovery of a small protein from activated carbon occurs at a solution pH further away from the protein's isoelectric point, where it is strongly charged. Studies measuring the binding capacities of individual polymers and proteins were used to develop these three guidelines, and they were then applied to the separation of several different protein mixtures. The ability of activated carbon to separate proteins was demonstrated to be broadly applicable with three different types of activated carbon by both static treatment and by flowing through a packed column of activated carbon.
Gas Separations using Ceramic Membranes
Energy Technology Data Exchange (ETDEWEB)
Paul KT Liu
2005-01-13
This project has been oriented toward the development of a commercially viable ceramic membrane for high temperature gas separations. A technically and commercially viable high temperature gas separation membrane and process has been developed under this project. The lab and field tests have demonstrated the operational stability, both performance and material, of the gas separation thin film, deposited upon the ceramic membrane developed. This performance reliability is built upon the ceramic membrane developed under this project as a substrate for elevated temperature operation. A comprehensive product development approach has been taken to produce an economically viable ceramic substrate, gas selective thin film and the module required to house the innovative membranes for the elevated temperature operation. Field tests have been performed to demonstrate the technical and commercial viability for (i) energy and water recovery from boiler flue gases, and (ii) hydrogen recovery from refinery waste streams using the membrane/module product developed under this project. Active commercializations effort teaming with key industrial OEMs and end users is currently underway for these applications. In addition, the gas separation membrane developed under this project has demonstrated its economical viability for the CO2 removal from subquality natural gas and landfill gas, although performance stability at the elevated temperature remains to be confirmed in the field.
Ceria Based Composite Membranes for Oxygen Separation
DEFF Research Database (Denmark)
Gurauskis, Jonas; Ovtar, Simona; Kaiser, Andreas
2014-01-01
. Composite thin film was deposited on tubular structural support made of porous MgO phase. Porous CGO layers (20 μm) were implemented as backbones for catalytic phase on both sides of a composite membrane (Fig. 1). During initial trials, the catalytic phase free CGO/LSF composite membranes demonstrated......Mixed ionic-electronic conducting membranes for oxygen gas separation are attracting a lot of interest due to their promising potential for the pure oxygen and the syngas production. Apart from the need for a sufficiently high oxygen permeation fluxes, the prolonged stability of these membranes...... under the large oxygen potential gradients at elevated temperatures is decisive for the future applications. The gadolinium doped cerium oxide (CGO) based composite membranes are considered as promising candidates due to inherent stability of CGO phase. The CGO matrix is a main oxygen ion transporter...
The Reintegration of Military Families Following Long Term Separation
2005-05-01
again during reunion most dramatically lead to successful reintegration and what leads to negative outcomes such as domestic violence or divorce...best as possible to adapt to separation and reunion. Potentially, programs can be developed that foster traits associated with successful reintegration ...reunifies, it must be discovered what successful reintegration is for AF families after they experienced a long-term separation. Since single parenting
Smart Pipette and Microfluidic Pipette Tip for Blood Plasma Separation.
Kim, Byeongyeon; Choi, Sungyoung
2016-01-13
An integrated method for blood plasma separation is presented by combining a pneumatic device, which is referred to as a "smart pipette," and a hydrophoretic microchannel as a microfluidic pipette tip for whole-blood sample preparation. This method enables hemolysis-free, high-purity plasma separation through smart pipetting of whole blood, potentially providing the means for rapid, inexpensive blood sample preparation for point-of-care testing.
Directory of Open Access Journals (Sweden)
Ming Xue
2016-11-01
Full Text Available In recent years, chiral microporous materials with open pores have attracted much attention because of their potential applications in enantioselective separation and catalysis. This review summarizes the recent advances on chiral microporous materials, such as metal-organic frameworks (MOFs, hydrogen-bonded organic frameworks (HOFs and covalent organic frameworks (COFs. We will introduce the synthetic strategies in detail and highlight the current status of chiral microporous materials on solid enantioselective adsorption, chiral chromatography resolution and membrane separation.
Magnetic separation for environmental remediation
Energy Technology Data Exchange (ETDEWEB)
Schake, A.R.; Avens, L.R.; Hill, D.D.; Padilla, D.D.; Prenger, F.C.; Romero, D.A.; Worl, L.A. [Los Alamos National Lab., NM (United States); Tolt, T.L. [Lockheed Environmental Systems and Technologies Co., Las Vegas, NV (United States)
1994-11-01
High Gradient Magnetic Separation (HGMS) is a form of magnetic separation used to separate solids from other solids, liquids or gases. HGMS uses large magnetic field gradients to separate ferromagnetic and paramagnetic particles from diamagnetic host materials. The technology relies only on physical properties, and therefore separations can be achieved while producing a minimum of secondary waste. Actinide and fission product wastes within the DOE weapons complex pose challenging problems for environmental remediation. Because the majority of actinide complexes and many fission products are paramagnetic, while most host materials are diamagnetic, HGMS can be used to concentrate the contaminants into a low volume waste stream. The authors are currently developing HGMS for applications to soil decontamination, liquid waste treatment, underground storage tank waste treatment, and actinide chemical processing residue concentration. Application of HGMS usually involves passing a slurry of the contaminated mixture through a magnetized volume. Field gradients are produced in the magnetized volume by a ferromagnetic matrix material, such as steel wool, expanded metal, iron shot, or nickel foam. The matrix fibers become trapping sites for ferromagnetic and paramagnetic particles in the host material. The particles with a positive susceptibility are attracted toward an increasing magnetic field gradient and can be extracted from diamagnetic particles, which react in the opposite direction, moving away from the areas of high field gradients. The extracted paramagnetic contaminants are flushed from the matrix fibers when the magnetic field is reduced to zero or when the matrix canister is removed from the magnetic field. Results are discussed for the removal of uranium trioxide from water, PuO{sub 2}, U, and Pu from various soils (Fernald, Nevada Test Site), and the waste water treatment of Pu and Am isotopes using HGMS.
Polymeric Gas-Separation Membranes for Petroleum Refining
Directory of Open Access Journals (Sweden)
Yousef Alqaheem
2017-01-01
Full Text Available Polymeric gas-separation membranes were commercialized 30 years ago. The interest on these systems is increasing because of the simplicity of concept and low-energy consumption. In the refinery, gas separation is needed in many processes such as natural gas treatment, carbon dioxide capture, hydrogen purification, and hydrocarbons separations. In these processes, the membranes have proven to be a potential candidate to replace the current conventional methods of amine scrubbing, pressure swing adsorption, and cryogenic distillation. In this paper, applications of polymeric membranes in the refinery are discussed by reviewing current materials and commercialized units. Economical evaluation of these membranes in comparison to traditional processes is also indicated.
Directory of Open Access Journals (Sweden)
Marco A. P. Orrico Júnior
2009-01-01
Full Text Available O objetivo foi avaliar o potencial poluidor remanescente dos efluentes de biodigestores abastecidos com dejetos de suínos com separação da fração sólida (CSFS e sem separação da fração sólida (SSFS, e conduzidos sob diferentes tempos de retenção hidráulica (TRH. Os efluentes utilizados eram de biodigestores semicontínuos manejados com TRH de 15; 22; 29 e 36 dias, com e sem separação da fração sólida. Foram utilizados biodigestores batelada, que permaneceram em operação por todo o tempo em que houve produção de biogás (60 dias. Foram avaliadas a produção e a qualidade do biogás, bem como os potenciais de produção por kg de sólidos totais e sólidos voláteis, e as demandas química e bioquímica de oxigênio. Utilizou-se do delineamento inteiramente casualisado, em esquema fatorial 2x4, com três repetições por tratamento. Foram encontrados potenciais de produção de 385 e 117 litros de CH4kg-1 de SV adicionados no material SSFS e CSFS, respectivamente, no menor TRH (15 dias, e potenciais de produção de 74 e 18 litros de CH4kg-1 de SV adicionados no material SSFS e CSFS, respectivamente, no maior TRH (36 dias.The objective of this work was to evaluate the polluting potential from the remainings of effluents from biodigesters that operate with swine manure with the separation of the solid fraction and without the separation of the solid fraction, both under different hydraulic retention times (HRT. For the biodigestion trial, the effluents from semi-continuous biodigesters were processed with 15; 22; 29 and 36 days of hydraulic retention, with and without the separation of the solid fraction. In this part of the work batch biodigesters were used, which were kept in the operation as long as biogas was produced (60 days. It was evaluated: biogas production and quality and yield potential, the potential production per kg of total solids and volatile solids and chemical and biochemical demands for oxygen. Production
Teaching Separations: Why, What, When, and How?
Wankat, Phillip C.
2001-01-01
Describes how and when to teach separation science to chemical engineering students. Separation science is important for industrial businesses involving the manufacture of adsorption systems, distillation columns, extractors, and other separation equipment and techniques. (Contains 13 references.) (YDS)
Accessing the exceptional points of parity-time symmetric acoustics
Shi, Chengzhi; Dubois, Marc; Chen, Yun; Cheng, Lei; Ramezani, Hamidreza; Wang, Yuan; Zhang, Xiang
2016-03-01
Parity-time (PT) symmetric systems experience phase transition between PT exact and broken phases at exceptional point. These PT phase transitions contribute significantly to the design of single mode lasers, coherent perfect absorbers, isolators, and diodes. However, such exceptional points are extremely difficult to access in practice because of the dispersive behaviour of most loss and gain materials required in PT symmetric systems. Here we introduce a method to systematically tame these exceptional points and control PT phases. Our experimental demonstration hinges on an active acoustic element that realizes a complex-valued potential and simultaneously controls the multiple interference in the structure. The manipulation of exceptional points offers new routes to broaden applications for PT symmetric physics in acoustics, optics, microwaves and electronics, which are essential for sensing, communication and imaging.
Selective Photo-Initiated Electrophoretic Separator Project
National Aeronautics and Space Administration — Physical Optics Corporation (POC) proposes to develop a Selective Photoinitiated Electrophoretic Separator (SPIES) System to address NASA's volatile gas separation...
Fragment separator momentum compression schemes
Energy Technology Data Exchange (ETDEWEB)
Bandura, Laura, E-mail: bandura@anl.gov [Facility for Rare Isotope Beams (FRIB), 1 Cyclotron, East Lansing, MI 48824-1321 (United States); National Superconducting Cyclotron Lab, Michigan State University, 1 Cyclotron, East Lansing, MI 48824-1321 (United States); Erdelyi, Bela [Argonne National Laboratory, Argonne, IL 60439 (United States); Northern Illinois University, DeKalb, IL 60115 (United States); Hausmann, Marc [Facility for Rare Isotope Beams (FRIB), 1 Cyclotron, East Lansing, MI 48824-1321 (United States); Kubo, Toshiyuki [RIKEN Nishina Center, RIKEN, Wako (Japan); Nolen, Jerry [Argonne National Laboratory, Argonne, IL 60439 (United States); Portillo, Mauricio [Facility for Rare Isotope Beams (FRIB), 1 Cyclotron, East Lansing, MI 48824-1321 (United States); Sherrill, Bradley M. [National Superconducting Cyclotron Lab, Michigan State University, 1 Cyclotron, East Lansing, MI 48824-1321 (United States)
2011-07-21
We present a scheme to use a fragment separator and profiled energy degraders to transfer longitudinal phase space into transverse phase space while maintaining achromatic beam transport. The first order beam optics theory of the method is presented and the consequent enlargement of the transverse phase space is discussed. An interesting consequence of the technique is that the first order mass resolving power of the system is determined by the first dispersive section up to the energy degrader, independent of whether or not momentum compression is used. The fragment separator at the Facility for Rare Isotope Beams is a specific application of this technique and is described along with simulations by the code COSY INFINITY.
Fragment separator momentum compression schemes.
Energy Technology Data Exchange (ETDEWEB)
Bandura, L.; Erdelyi, B.; Hausmann, M.; Kubo, T.; Nolen, J.; Portillo, M.; Sherrill, B.M. (Physics); (MSU); (Northern Illinois Univ.); (RIKEN)
2011-07-21
We present a scheme to use a fragment separator and profiled energy degraders to transfer longitudinal phase space into transverse phase space while maintaining achromatic beam transport. The first order beam optics theory of the method is presented and the consequent enlargement of the transverse phase space is discussed. An interesting consequence of the technique is that the first order mass resolving power of the system is determined by the first dispersive section up to the energy degrader, independent of whether or not momentum compression is used. The fragment separator at the Facility for Rare Isotope Beams is a specific application of this technique and is described along with simulations by the code COSY INFINITY.
Causal and causally separable processes
Oreshkov, Ognyan; Giarmatzi, Christina
2016-09-01
The idea that events are equipped with a partial causal order is central to our understanding of physics in the tested regimes: given two pointlike events A and B, either A is in the causal past of B, B is in the causal past of A, or A and B are space-like separated. Operationally, the meaning of these order relations corresponds to constraints on the possible correlations between experiments performed in the vicinities of the respective events: if A is in the causal past of B, an experimenter at A could signal to an experimenter at B but not the other way around, while if A and B are space-like separated, no signaling is possible in either direction. In the context of a concrete physical theory, the correlations compatible with a given causal configuration may obey further constraints. For instance, space-like correlations in quantum mechanics arise from local measurements on joint quantum states, while time-like correlations are established via quantum channels. Similarly to other variables, however, the causal order of a set of events could be random, and little is understood about the constraints that causality implies in this case. A main difficulty concerns the fact that the order of events can now generally depend on the operations performed at the locations of these events, since, for instance, an operation at A could influence the order in which B and C occur in A’s future. So far, no formal theory of causality compatible with such dynamical causal order has been developed. Apart from being of fundamental interest in the context of inferring causal relations, such a theory is imperative for understanding recent suggestions that the causal order of events in quantum mechanics can be indefinite. Here, we develop such a theory in the general multipartite case. Starting from a background-independent definition of causality, we derive an iteratively formulated canonical decomposition of multipartite causal correlations. For a fixed number of settings and
Bayesian Source Separation and Localization
Knuth, K H
1998-01-01
The problem of mixed signals occurs in many different contexts; one of the most familiar being acoustics. The forward problem in acoustics consists of finding the sound pressure levels at various detectors resulting from sound signals emanating from the active acoustic sources. The inverse problem consists of using the sound recorded by the detectors to separate the signals and recover the original source waveforms. In general, the inverse problem is unsolvable without additional information. This general problem is called source separation, and several techniques have been developed that utilize maximum entropy, minimum mutual information, and maximum likelihood. In previous work, it has been demonstrated that these techniques can be recast in a Bayesian framework. This paper demonstrates the power of the Bayesian approach, which provides a natural means for incorporating prior information into a source model. An algorithm is developed that utilizes information regarding both the statistics of the amplitudes...
Magnetic Separator Enhances Treatment Possibilities
2008-01-01
Since the earliest missions in space, NASA specialists have performed experiments in low gravity. Protein crystal growth, cell and tissue cultures, and separation technologies such as electrophoresis and magnetophoresis have been studied on Apollo 14, Apollo 16, STS-107, and many other missions. Electrophoresis and magnetophoresis, respectively, are processes that separate substances based on the electrical charge and magnetic field of a molecule or particle. Electrophoresis has been studied on over a dozen space shuttle flights, leading to developments in electrokinetics, which analyzes the effects of electric fields on mass transport (atoms, molecules, and particles) in fluids. Further studies in microgravity will continue to improve these techniques, which researchers use to extract cells for various medical treatments and research.
Extraction and separation of proteoglycans.
Yanagishita, Masaki; Podyma-Inoue, Katarzyna Anna; Yokoyama, Miki
2009-11-01
Proteoglycans contain a unique carbohydrate component, glycosaminoglycan, which consists of repeating, typically sulfated disaccharides, and is capable of interacting with diverse molecules. Specific, clustered arrangements of sulfate on the glycosaminoglycan backbone form binding sites for many biologically important ligands such as extracellular matrix molecules and growth factors. Core proteins of proteoglycans also show molecular interactions necessary for organizing scaffolds in the extracellular matrix or for anchoring proteoglycans to the plasma membrane. Experimental protocols aiming at extracting maximal amounts of proteoglycans from tissues or cells require disruption of molecular interactions involving proteoglycans by denaturing solvents. Among many of the proteoglycan separation procedures, anion exchange chromatography, which takes advantage of the presence of highly negatively charged glycosaminoglycans in all proteoglycans, serves one of the most convenient general separation techniques.
Neurointerventional participation in craniopagus separation
Alokaili, Riyadh Nasser; Ahmed, Muhammad Ejaz; Al Feryan, Ahmed; Goodrich, James T; Aloraidi, Ahmed
2015-01-01
Craniopagus-type conjoined twins (joined at the head) are exceedingly rare. Separation of craniopagus conjoined twins is a challenging task mainly owing to complex vascular anatomy and limited experience with this disorder. Modern neuroimaging techniques including digital subtraction angiography can be used to preoperatively assess the cerebral vascular system. These techniques can also provide the raw data to fabricate three-dimensional true-scale models. We report a case in which endovascul...
LISA propulsion module separation study
Energy Technology Data Exchange (ETDEWEB)
Merkowitz, S M [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Ahmad, A [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Hyde, T T [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Sweetser, T [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Ziemer, J [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Conkey, S [Swales Aerospace, 5050 Powder Mill Road, Beltsville, MD 20705 (United States); III, W Kelly [Swales Aerospace, 5050 Powder Mill Road, Beltsville, MD 20705 (United States); Shirgur, B [Swales Aerospace, 5050 Powder Mill Road, Beltsville, MD 20705 (United States)
2005-05-21
The Laser Interferometer Space Antenna (LISA) mission is a space-borne gravitational wave detector consisting of three sciencecraft in heliocentric orbit. Each sciencecraft is delivered to its operational orbit by a propulsion module. Because of the strict thermal and mass balancing requirements of LISA, the baseline mission concept requires that the propulsion module separate from the sciencecraft after delivery. The only propulsion system currently included in the sciencecraft design are micronewton level thrusters, such as field emission electric propulsion (FEEP) or colloid thrusters, that are used to balance the 30-40 {mu}N of solar radiation pressure and provide the drag-free and attitude control of the sciencecraft. Due to these thrusters' limited authority, the separation of the propulsion module from the sciencecraft must be well controlled to not induce a large tip-off rotation of the sciencecraft. We present here the results of a study of the propulsion module separation system requirements that are necessary to safely deliver the three LISA sciencecraft to their final operational orbits.
Analytical Analysis of Motion Separability
Directory of Open Access Journals (Sweden)
Marjan Hadian Jazi
2013-01-01
Full Text Available Motion segmentation is an important task in computer vision and several practical approaches have already been developed. A common approach to motion segmentation is to use the optical flow and formulate the segmentation problem using a linear approximation of the brightness constancy constraints. Although there are numerous solutions to solve this problem and their accuracies and reliabilities have been studied, the exact definition of the segmentation problem, its theoretical feasibility and the conditions for successful motion segmentation are yet to be derived. This paper presents a simplified theoretical framework for the prediction of feasibility, of segmentation of a two-dimensional linear equation system. A statistical definition of a separable motion (structure is presented and a relatively straightforward criterion for predicting the separability of two different motions in this framework is derived. The applicability of the proposed criterion for prediction of the existence of multiple motions in practice is examined using both synthetic and real image sequences. The prescribed separability criterion is useful in designing computer vision applications as it is solely based on the amount of relative motion and the scale of measurement noise.
Robust Simulations and Significant Separations
Fortnow, Lance
2010-01-01
We define and study a new notion of "robust simulations" between complexity classes which is intermediate between the traditional notions of infinitely-often and almost-everywhere, as well as a corresponding notion of "significant separations". A language L has a robust simulation in a complexity class C if there is a language in C which agrees with L on arbitrarily large polynomial stretches of input lengths. There is a significant separation of L from C if there is no robust simulation of L in C. The new notion of simulation is a cleaner and more natural notion of simulation than the infinitely-often notion. We show that various implications in complexity theory such as the collapse of PH if NP = P and the Karp-Lipton theorem have analogues for robust simulations. We then use these results to prove that most known separations in complexity theory, such as hierarchy theorems, fixed polynomial circuit lower bounds, time-space tradeoffs, and the theorems of Allender and Williams, can be strengthened to signifi...
Research and development separation technology: The DOE Industrial Energy Conservation Program
Energy Technology Data Exchange (ETDEWEB)
1987-07-01
This brochure summarizes the Office of Industrial Programs' RandD efforts in the advancement of separation technology. The purpose of this brochure is to provide interested parties with information on federal industrial energy conservation activities in separation technology. The brochure is comprised of the following sections: Separation Technology, summarizes the current state of separation technology and its uses. Potential Energy Savings, discusses the potential for industrial energy conservation through the implementation of advanced separation processes. Office of Industrial Programs' RandD Efforts in Separation Technology Development, describes the separation RandD projects conducted by IP. RandD Data Base, lists contractor, principal investigator, and location of each separation-related RandD effort sponsored by IP.
CFD Analysis of Energy Separation in Ranque-Hilsch Vortex Tube at Cryogenic Temperature
Dutta, T.; K.P.Sinhamahapatra; BANDYOPADHYAY S.S.
2013-01-01
Study of the energy separation phenomenon in vortex tube (VT) at cryogenic temperature (temperature range below 123 K) has become important because of the potential application of VT as in-flight air separator in air breathing propulsion. In the present study, a CFD model is used to simulate the energy separation phenomenon in VT with gaseous air at cryogenic temperature as working fluid. Energy separation at cryogenic temperature is found to be considerably less than that obtained at normal ...
Revisiting separation properties of convex fuzzy sets
Separation of convex sets by hyperplanes has been extensively studied on crisp sets. In a seminal paper separability and convexity are investigated, however there is a flaw on the definition of degree of separation. We revisited separation on convex fuzzy sets that have level-wise (crisp) disjointne...
Relaxation phenomena in dense gas separation membranes
Wessling, Matthias
1993-01-01
Solution-diffusion membranes are widely used for the separation of gaseous and liquid mixtures. The separation of air (O2/N2), landfill gas (CH4/CO2) and purge gas streams (NH3/H2) in the ammonia synthesis are examples for state-of-the-art membrane gas separation processes. For the separation of liq
Relaxation phenomena in dense gas separation membranes
Wessling, Matthias
1993-01-01
Solution-diffusion membranes are widely used for the separation of gaseous and liquid mixtures. The separation of air (O2/N2), landfill gas (CH4/CO2) and purge gas streams (NH3/H2) in the ammonia synthesis are examples for state-of-the-art membrane gas separation processes. For the separation of
Center for Advanced Separation Technology
Energy Technology Data Exchange (ETDEWEB)
Honaker, Rick
2013-09-30
The U.S. is the largest producer of mining products in the world. In 2011, U.S. mining operations contributed a total of $232 billion to the nation’s GDP plus $138 billion in labor income. Of this the coal mining industry contributed a total of $97.5 billion to GDP plus $53 billion in labor income. Despite these contributions, the industry has not been well supported with research and development funds as compared to mining industries in other countries. To overcome this problem, the Center for Advanced Separation Technologies (CAST) was established to develop technologies that can be used by the U.S. mining industry to create new products, reduce production costs, and meet environmental regulations. Originally set up by Virginia Tech and West Virginia University, CAST is now a five-university consortium – Virginia Tech, West Virginia University, University of Kentucky, University of Utah and Montana Tech, - that is supported through U.S. DOE Cooperative Agreement No. DE-FE0000699, Center for Advanced Separation Technology. Much of the research to be conducted with Cooperative Agreement funds will be longer term, high-risk, basic research and will be carried out in two broad areas: Advanced Pre-Combustion Clean Coal Technologies and Gas-Gas Separations. Distribution of funds is handled via competitive solicitation of research proposals through Site Coordinators at the five member universities. These were reviewed and the selected proposals were forwarded these to the DOE/NETL Project Officer for final review and approval. The successful projects are listed below by category, along with abstracts from their final reports.
SEPARATION OF THORIUM FROM URANIUM
Bane, R.W.
1959-09-01
A description is given for the separation of thorium from uranium by forming an aqueous acidic solution containing ionic species of thorium, uranyl uranium, and hydroxylamine, flowing the solution through a column containing the phenol-formaldehyde type cation exchange resin to selectively adsorb substantially all the thorium values and a portion of the uranium values, flowing a dilute solution of hydrochloric acid through the column to desorb the uranium values, and then flowing a dilute aqueous acidic solution containing an ion, such as bisulfate, which has a complexing effect upon thortum through the column to desorb substantially all of the thorium.
SEPARATION OF URANIUM FROM THORIUM
Hellman, N.N.
1959-07-01
A process is presented for separating uranium from thorium wherein the ratio of thorium to uranium is between 100 to 10,000. According to the invention the thoriumuranium mixture is dissolved in nitric acid, and the solution is prepared so as to obtain the desired concentration within a critical range of from 4 to 8 N with regard to the total nitrate due to thorium nitrate, with or without nitric acid or any nitrate salting out agent. The solution is then contacted with an ether, such as diethyl ether, whereby uranium is extracted into ihe organic phase while thorium remains in the aqueous phase.
Separation vortices and pattern formation
DEFF Research Database (Denmark)
Andersen, Anders Peter; Bohr, Tomas; Schnipper, Teis
2010-01-01
In this paper examples are given of the importance of flow separation for fluid patterns at moderate Reynolds numbers—both in the stationary and in the time-dependent domain. In the case of circular hydraulic jumps, it has been shown recently that it is possible to generalise the Prandtl–Kármán–P...... results for the vortex patterns behind a flapping foil in a flowing soap film, which shows the interaction and competition between the vortices shed from the round leading edge (like the von Kármán vortex street) and those created at the sharp trailing edge....
Materials for carbon dioxide separation
Energy Technology Data Exchange (ETDEWEB)
Xu, Qingqing
2014-10-01
The CO{sub 2} adsorption capacities at room temperature have been investigated by comparing carbon nanotubes, fullerene, graphenes, graphite and granular activated carbons. It turned out that the amount of the micropore surface area was dominating the CO{sub 2} adsorption ability. Another promising class of materials for CO{sub 2} capture and separation are CaO derived from the eggshells. Two aspects were studied in present work: a new hybrid materials synthesized by doping the CaTiO{sub 3} and the relationship between physisorption and chemisorption properties of CaO-based materials.
The bioethics of separating conjoined twins in plastic surgery.
Lee, Michelle; Gosain, Arun K; Becker, Devra
2011-10-01
The incidence of craniopagus twins approximates four to six per 10 million births. Although rare, surgical separation of conjoined twins poses significant technical and ethical challenges. The present report uses the case of craniopagus twins AD and TD to examine the bioethical issues faced by a multidisciplinary medical team in planning the separation of craniopagus twins. AD and TD are craniopagus twins conjoined at the head. TD's head is conjoined to the back of AD's head. Neurologically, AD has the dominant cerebral circulation. TD has two normal kidneys, whereas AD has none. AD depends on TD's renal function and, on separation, will require either a kidney transplant or lifelong dialysis. This case report reviews one approach to analyzing and solving complex ethical dilemmas in pediatric plastic surgery. The principles reviewed are (1) autonomy and informed consent, focusing especially on the role of children in the informed consent process; (2) beneficence and nonmaleficence, two intricately intertwined principles because separation could potentially cause irreversible harm to one twin while improving the quality of life for the other (as separation is not a life-saving procedure, is it ethical to perform a procedure with unknown surgical risk to improve children's quality of life?); and (3) justice (is it fair to allocate excessive medical resources for the twins' separation?). The present report explores the ethics behind such decisions with respect to the separation of conjoined twins.
Technique to separate lidar signal and sunlight.
Sun, Wenbo; Hu, Yongxiang; MacDonnell, David G; Weimer, Carl; Baize, Rosemary R
2016-06-13
Sunlight contamination dominates the backscatter noise in space-based lidar measurements during daytime. The background scattered sunlight is highly variable and dependent upon the surface and atmospheric albedo. The scattered sunlight contribution to noise increases over land and snow surfaces where surface albedos are high and thus overwhelm lidar backscatter from optically thin atmospheric constituents like aerosols and thin clouds. In this work, we developed a novel lidar remote sensing concept that potentially can eliminate sunlight induced noise. The new lidar concept requires: (1) a transmitted laser light that carries orbital angular momentum (OAM); and (2) a photon sieve (PS) diffractive filter that separates scattered sunlight from laser light backscattered from the atmosphere, ocean and solid surfaces. The method is based on numerical modeling of the focusing of Laguerre-Gaussian (LG) laser beam and plane-wave light by a PS. The model results show that after passing through a PS, laser light that carries the OAM is focused on a ring (called "focal ring" here) on the focal plane of the PS filter, very little energy arrives at the center of the focal plane. However, scattered sunlight, as a plane wave without the OAM, focuses at the center of the focal plane and thus can be effectively blocked or ducted out. We also find that the radius of the "focal ring" increases with the increase of azimuthal mode (L) of LG laser light, thus increasing L can more effectively separate the lidar signal away from the sunlight noise.
Electrically Driven Ion Separations in Permeable Membranes
Energy Technology Data Exchange (ETDEWEB)
Bruening, Merlin [Michigan State Univ., East Lansing, MI (United States)
2017-04-21
Membranes are attractive for a wide range of separations due to their low energy costs and continuous operation. To achieve practical fluxes, most membranes consist of a thin, selective skin on a highly permeable substrate that provides mechanical strength. Thus, this project focused on creating new methods for forming highly selective ultrathin skins as well as modeling transport through these coatings to better understand their unprecedented selectivities. The research explored both gas and ion separations, and the latter included transport due to concentration, pressure and electrical potential gradients. This report describes a series of highlights of the research and then provides a complete list of publications supported by the grant. These publications have been cited more than 4000 times. Perhaps the most stunning finding is the recent discovery of monovalent/divalent cation and anion selectivities around 1000 when modifying cation- and anion-exchange membranes with polyelectrolyte multilayers (PEMs). This discovery builds on many years of exciting research. (Citation numbers refer to the journal articles in the bibliography.)
Reversal of laryngotracheal separation in paediatric patients.
LENUS (Irish Health Repository)
Young, Orla
2012-02-01
OBJECTIVE: Laryngotracheal separation (LTS) is an effective and reliable definitive treatment for intractable aspiration. A major advantage of this treatment for intractable aspiration is its\\' potential reversibility. Should the underlying disorder improve, a reversal of the procedure may be attempted. This has been successfully achieved in the adult population. To our knowledge, no previous cases have been reported of successful reversal of LTS in children. METHODS: A retrospective review from 2003 to 2010 identified four cases of intractable aspiration treated with LTS in our department. Two of these patients displayed objective evidence of sufficient recovery of their underlying aspiration to consider reversal. Patient selection for reversal was dependent upon successful oral intake for 9 months along with videofluoroscopic evidence of normal or minimally impaired swallow. RESULTS: Two children who were successfully treated for intractable aspiration with LTS demonstrated objective evidence of recovery sufficient to attempt reversal. Both children underwent successful surgical reversal of LTS using a cricotracheal resection with end-to-end anastamosis, similar to that used in treatment of subglottic stenosis. Both children can now tolerate oral diet and their speech and language development is in line with their overall developmental level. CONCLUSIONS: Laryngotracheal separation is an effective and reliable definitive treatment for intractable aspiration facilitating protection of the airway and allowing safe swallowing with unimpeded respiration, but with the major drawback of loss of phonation. To our knowledge, we document the first two cases of successful LTS reversal in children.
Finger prick blood plasma separation using a standard lab equipment
DEFF Research Database (Denmark)
Kwasny, Dorota; Andersen, Karsten Brandt; Pfreundt, Andrea
separation and analyte detection on-chip are reported in the literature [1]. Although versatile, these plasma separation techniques often require sample dilution prior to separation and use low flow rates resulting in longer processing times which greatly hinders their use in commercial systems. Here we......Blood is a complex biological matrix that has a huge potential for diagnostics as it contains various analytes and biomarkers. Traditionally the analysis is performed on plasma and white blood cells separated from venous blood. However, the collection of venous blood samples is painful and requires...... a few milliliters of blood. It has been demonstrated that the blood taken from finger prick contains the same analytes as venous blood in sufficient abundance and could therefore be used for diagnosis as an alternative in many cases. Various approaches towards analysis of finger prick blood with plasma...
Separation energy dependence of hole form factors
Energy Technology Data Exchange (ETDEWEB)
Van de Wiele, J. [Institut de Physique Nucleaire, 91 - Orsay (France); Vdovin, A. [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Langevin-Joliot, H. [Institut de Physique Nucleaire, 91 - Orsay (France)
1996-08-05
Form factors of fragmented hole states are studied within the quasiparticle-phonon model, using the inhomogeneous equation method. The validity of this method is successfully checked by comparison with coupled equation solutions in schematic vibrational model cases. A systematic investigation of form factors is performed for neutron and proton hole states in the valence and first inner shells of {sup 208}Pb. Large fluctuations of form factor radii are observed for individual levels superimposed on a general increase with separation energy. Average characteristics are introduced for groups of levels, namely the mean form factors, summed source terms and correction potentials, and their behaviour is presented. The role of the relative values of the interaction radius parameter and binding well radius is discussed in detail. (orig.).
Metal separations using aqueous biphasic partitioning systems
Energy Technology Data Exchange (ETDEWEB)
Chaiko, D.J.; Zaslavsky, B.; Rollins, A.N.; Vojta, Y.; Gartelmann, J.; Mego, W. [Argonne National Lab., IL (United States). Chemical Technology Div.
1996-05-01
Aqueous biphasic extraction (ABE) processes offer the potential for low-cost, highly selective separations. This countercurrent extraction technique involves selective partitioning of either dissolved solutes or ultrafine particulates between two immiscible aqueous phases. The extraction systems that the authors have studied are generated by combining an aqueous salt solution with an aqueous polymer solution. They have examined a wide range of applications for ABE, including the treatment of solid and liquid nuclear wastes, decontamination of soils, and processing of mineral ores. They have also conducted fundamental studies of solution microstructure using small angle neutron scattering (SANS). In this report they review the physicochemical fundamentals of aqueous biphase formation and discuss the development and scaleup of ABE processes for environmental remediation.
Countercurrent Separation of Natural Products: An Update
2015-01-01
This work assesses the current instrumentation, method development, and applications in countercurrent chromatography (CCC) and centrifugal partition chromatography (CPC), collectively referred to as countercurrent separation (CCS). The article provides a critical review of the CCS literature from 2007 since our last review (J. Nat. Prod.2008, 71, 1489–1508), with a special emphasis on the applications of CCS in natural products research. The current state of CCS is reviewed in regard to three continuing topics (instrumentation, solvent system development, theory) and three new topics (optimization of parameters, workflow, bioactivity applications). The goals of this review are to deliver the necessary background with references for an up-to-date perspective of CCS, to point out its potential for the natural product scientist, and thereby to induce new applications in natural product chemistry, metabolome, and drug discovery research involving organisms from terrestrial and marine sources. PMID:26177360
Source number estimation and separation algorithms of underdetermined blind separation
Institute of Scientific and Technical Information of China (English)
YANG ZuYuan; TAN BeiHai; ZHOU GuoXu; ZHANG JinLong
2008-01-01
Recently,sparse component analysis (SCA) has become a hot spot in BSS research.Instead of independent component analysis (ICA),SCA can be used to solve underdetermined mixture efficiently.Two-step approach (TSA) is one of the typical methods to solve SCA based BSS problems.It estimates the mixing matrix before the separation of the sources.K-means clustering is often used to estimate the mixing matrix.It relies on the prior knowledge of the source number strongly.However,the estimation of the source number is an obstacle.In this paper,a fuzzy clustering method is proposed to estimate the source number and mixing matrix simultaneously.After that,the sources are recovered by the shortest path method (SPM).Simulations show the availability and robustness of the proposed method.
Energy Technology Data Exchange (ETDEWEB)
Hakuta, Toshikatu [National Inst. of Materials and Chemical Research, Ibaraki (Japan)
1993-12-31
The climate change induced by CO{sub 2} and other greenhouse gases is probably the most serious environmental threat that mankind has ever experienced. Nowadays fossil fuels occupy the majority of the world commercial energy supply. Most nations will be dependent on fossil fuels even in the first half of the next century. Around 30 % of CO{sub 2} in the world is emitted from thermal power plants. Recovering CO{sub 2} from energy conversion processes and storing it outside the atmosphere is a promising option for the mitigation of global warming. CO{sub 2} fixation and storage include CO{sub 2} disposal into oceans and underground, and utilization of CO{sub 2}. CO{sub 2} separation process will be used in any CO{sub 2} storage system, and is estimated to consume almost half the energy of the total system. Research and development of highly efficient CO{sub 2} separation process is most important from the viewpoint of practical application of CO{sub 2} fixation system.
Ganichev, Sergey D.; Bel'Kov, Vasily V.; Tarasenko, Sergey A.; Danilov, Sergey N.; Giglberger, Stephan; Hoffmann, Christoph; Ivchenko, Eougenious L.; Weiss, Dieter; Wegscheider, Werner; Gerl, Christian; Schuh, Dieter; Stahl, Joachim; de Boeck, Jo; Borghs, Gustaaf; Prettl, Wilhelm
2006-09-01
The generation, manipulation and detection of spin-polarized electrons in low-dimensional semiconductors are at the heart of spintronics. Pure spin currents, that is, fluxes of magnetization without charge current, are quite attractive in this respect. A paradigmatic example is the spin Hall effect, where an electrical current drives a transverse spin current and causes a non-equilibrium spin accumulation observed near the sample boundary. Here we provide evidence for an another effect causing spin currents which is fundamentally different from the spin Hall effect. In contrast to the spin Hall effect, it does not require an electric current to flow: without bias the spin separation is achieved by spin-dependent scattering of electrons in media with suitable symmetry. We show, by free-carrier absorption of terahertz (THz) radiation, that spin currents flow in a wide range of temperatures. Moreover, the experimental results provide evidence that simple electron gas heating by any means is already sufficient to yield spin separation due to spin-dependent energy-relaxation processes.
Separations and safeguards model integration.
Energy Technology Data Exchange (ETDEWEB)
Cipiti, Benjamin B.; Zinaman, Owen
2010-09-01
Research and development of advanced reprocessing plant designs can greatly benefit from the development of a reprocessing plant model capable of transient solvent extraction chemistry. This type of model can be used to optimize the operations of a plant as well as the designs for safeguards, security, and safety. Previous work has integrated a transient solvent extraction simulation module, based on the Solvent Extraction Process Having Interaction Solutes (SEPHIS) code developed at Oak Ridge National Laboratory, with the Separations and Safeguards Performance Model (SSPM) developed at Sandia National Laboratory, as a first step toward creating a more versatile design and evaluation tool. The goal of this work was to strengthen the integration by linking more variables between the two codes. The results from this integrated model show expected operational performance through plant transients. Additionally, ORIGEN source term files were integrated into the SSPM to provide concentrations, radioactivity, neutron emission rate, and thermal power data for various spent fuels. This data was used to generate measurement blocks that can determine the radioactivity, neutron emission rate, or thermal power of any stream or vessel in the plant model. This work examined how the code could be expanded to integrate other separation steps and benchmark the results to other data. Recommendations for future work will be presented.
Motility-Induced Phase Separation
Cates, Michael E.; Tailleur, Julien
2015-03-01
Self-propelled particles include both self-phoretic synthetic colloids and various microorganisms. By continually consuming energy, they bypass the laws of equilibrium thermodynamics. These laws enforce the Boltzmann distribution in thermal equilibrium: The steady state is then independent of kinetic parameters. In contrast, self-propelled particles tend to accumulate where they move more slowly. They may also slow down at high density for either biochemical or steric reasons. This creates positive feedback, which can lead to motility-induced phase separation (MIPS) between dense and dilute fluid phases. At leading order in gradients, a mapping relates variable-speed, self-propelled particles to passive particles with attractions. This deep link to equilibrium phase separation is confirmed by simulations but generally breaks down at higher order in gradients: New effects, with no equilibrium counterpart, then emerge. We give a selective overview of the fast-developing field of MIPS, focusing on theory and simulation but including a brief speculative survey of its experimental implications.
Spatial valley separation in strained graphene pn junction
Tian, HongYu; Wang, Jun
2017-09-01
Valleytronics in analogy to spintronics aims to use the electron valley degree of freedom to carry and manipulate information, and one of urgent tasks in this field is to generate valley-polarized electrons. In this work, we propose using the electron focusing effect in a strained graphene pn junction to separate valleys spatially through a beam of valley-unpolarized electrons, since the strain-induced pseudo-gauge potentials are opposite for K and K^\\prime valleys and severely affect the trajectories of K and K^\\prime electron propagation. We numerically simulate this valley-separated Veselago lens effect in a lattice model and demonstrate that pseudo-gauge potentials can efficiently control valley separation patterns.
DESIGN AND DEVELOPMENT OF INTEGRATED COMPACT MULTIPHASE SEPARATION SYSTEM (CMSS)
Energy Technology Data Exchange (ETDEWEB)
Ram S. Mohan; Ovadia Shoham
2004-12-31
The petroleum industry has relied in the past mainly on conventional vessel-type separators, which are bulky, heavy and expensive, to process wellhead production of oil-water-gas flow. Economic and operational pressures continue to force the petroleum industry to seek less expensive and more efficient separation alternatives in the form of compact separators. The compact dimensions, smaller footprint and lower weight of compact separators have a potential for cost savings to the industry, especially in offshore and subsea applications. Also, compact separators reduce the inventory of hydrocarbons significantly, which is critical for environmental and safety considerations. This report presents a brief overview of the activities and tasks accomplished during the part July 09, 2003--October 08, 2004, related to the Budget Period I (July 09, 2003--October 08, 2004) of the DOE project titled ''Design and Development of Integrated Compact Multiphase Separation System (CMSS{copyright})''. An executive summary is presented initially followed by the tasks of the current budget period. Then, detailed description of the experimental and modeling investigations are presented. Subsequently, the technical and scientific results of the activities of this project period are presented with discussions. The findings of this investigation are summarized in the ''Conclusions'' section followed by relevant references. The initial phase of the project (Budget Period I--07/09/2003 to 10/08/2004) focuses on the development of additional individual compact separation components, such as the horizontal pipe separator (HPS{copyright}), for obtaining clean oil stream from oil-water mixture, flow conditioning components, such as the helical pipe (HP) and slug damper (SD{copyright}), for dissipating slugs upstream of the compact separators. The project will also design and test an upstream slug generator (SG).
Adding a complex shift to HVPT
Energy Technology Data Exchange (ETDEWEB)
Killingbeck, John P [Observatoire de Besancon-Institut UTINAM, CNRS UMR 6213, Universite de Franche-Comte, 41 bis Avenue de l' Observatoire BP1615, 25010 Besancon cedex (France) and Centre for Mathematics, Loten Building, University of Hull, Hull HU6 7RX (United Kingdom)
2009-03-20
A complex coordinate shift is incorporated in renormalized hypervirial perturbation theory. Test calculations on harmonic oscillators with cubic perturbations show that the resulting method produces accurate numerical results for the real energies of PT symmetric Hamiltonians with complex potentials and for the complex resonance energies of Hamiltonians with real potentials.
Separation of Chlorella vulgaris from liquid phase using bioflocculants
Directory of Open Access Journals (Sweden)
Gizem Günay
2014-12-01
results showed that C. vulgaris was partially separated from the liquid phase. However, the experiments will continue for the purpose of increasing the flocculating activity. Getting successfully experimental results with kaolin showed that bioflocculant has a potential use in wastewater treatment. For this reason, it also is thought to analyze the effect of bioflocculant on the wastewater treatment with further studies.[¤
Ultrasound imaging for quantitative evaluation of magnetic density separation
Sanaee, S.A.
2013-01-01
This thesis is dedicated to an investigation of the potential and technological possibilities of an inline ultrasound system as a quality control system for wet recycling of solid waste. The main targeted recycling technology is magnetic density separation (MDS), a novel technique that was
Improved procedures for separating crystals from the melt
Verdoes, D.; Arkenbout, G.J.; Bruinsma, O.S.L.; Koutsoukos, P.G.; Ulrich, J.
1997-01-01
Innovative separation techniques like melt crystallization have the potential to fulfil two important demands, namely: a significant reduction of energy consumption by the chemical industry, and the production of high quality products required by industry. Several industrial applications of melt cry
Separation of nanocolloids driven by dielectrophoresis: A molecular dynamics simulation
Institute of Scientific and Technical Information of China (English)
NI ZhongHua; ZHANG XinJie; YI Hong
2009-01-01
The nonequilibrium molecular dynamics (MD) method was used to model the nanocolloids and the solvent particles. By introducing a non-uniform electric field, colloids were polarized to have opposite polarities. Separation of colloids driven by dielectrophoresis (DEP) could be seen clearly under a strong electric field at low temperatures. Analyzing the ratio of DEP velocities of colloids to thermal velocities of neutral solvent particles showed that when the ratio was correspondingly big, collision between colloids and solvent particles would be intense, making the DEP velocity of colloids fluctuate frequently. By changing the electric field strength, it was found that the enhancement of electric field strength would quicken the separation of colloids. But when the electric field strength increased to a certain degree, the separation motion would be slow because of the strong friction resistance of the solvent particles to the colloids. Moreover, studying the separation reason of colloids based on the potential energy showed that after colloids were polarized, the attractive potential energy among the colloids would be weaker than before, while the increase of temperature would reduce the attractive potential energy and increase the repulsive potential energy, which accorded with the DLVO theory.
Ultrasound imaging for quantitative evaluation of magnetic density separation
Sanaee, S.A.
2013-01-01
This thesis is dedicated to an investigation of the potential and technological possibilities of an inline ultrasound system as a quality control system for wet recycling of solid waste. The main targeted recycling technology is magnetic density separation (MDS), a novel technique that was investiga
Energy Technology Data Exchange (ETDEWEB)
Li, SG; Zong, ZW; Zhou, SJ; Huang, Y; Song, ZN; Feng, XH; Zhou, RF; Meyer, HS; Yu, M; Carreon, MA
2015-08-01
SAPO-34 membranes were synthesized by several routes towards N-2/CH4 separation. Membrane synthesis parameters including water content in the gel, crystallization time, support pore size, and aluminum source were investigated. High performance N-2-selective membranes were obtained on 100-nm-pore alumina tubes by using Al(i-C3H7O)(3) as aluminum source with a crystallization time of 6 h. These membranes separated N-2 from CH, with N-2 permeance as high as 500 GPU with separation selectivity of 8 at 24 degrees C. for a 50/50 N-2/CH4 mixture. Nitrogen and CH, adsorption isotherms were measured on SAPO-34 crystals. The N-2 and CH, heats of adsorption were 11 and 15 kJ/mol, respectively, which lead to a preferential adsorption of CE-H-4 over N-2 in the N-2/CH4 mixture. Despite this, the SAPO-34 membranes were selective for N-2 over CH4 in the mixture because N-2 diffuses much faster than CH4 and differences in diffusivity played a more critical role than the competitive adsorption. Preliminary economic evaluation indicates that the required N-2/CH4 selectivity would be 15 in order to maintain a CH4 loss below 10%. For small nitrogen-contaminated gas wells, our current SAPO-34 membranes have potential to compete with the benchmark technology cryogenic distillation for N-2 rejection. (C) 2015 Elsevier B.V. All rights reserved,
SEPARATION OF HAFNIUM FROM ZIRCONIUM
Overholser, L.B.; Barton, C.J. Sr.; Ramsey, J.W.
1960-05-31
The separation of hafnium impurities from zirconium can be accomplished by means of organic solvent extraction. The hafnium-containing zirconium feed material is dissolved in an aqueous chloride solution and the resulting solution is contacted with an organic hexone phase, with at least one of the phases containing thiocyanate. The hafnium is extracted into the organic phase while zirconium remains in the aqueous phase. Further recovery of zirconium is effected by stripping the onganic phase with a hydrochloric acid solution and commingling the resulting strip solution with the aqueous feed solution. Hexone is recovered and recycled by means of scrubbing the onganic phase with a sulfuric acid solution to remove the hafnium, and thiocyanate is recovered and recycled by means of neutralizing the effluent streams to obtain ammonium thiocyanate.
Explaining outliers by subspace separability
DEFF Research Database (Denmark)
Micenková, Barbora; Ng, Raymond T.; Dang, Xuan-Hong
2013-01-01
Outliers are extraordinary objects in a data collection. Depending on the domain, they may represent errors, fraudulent activities or rare events that are subject of our interest. Existing approaches focus on detection of outliers or degrees of outlierness (ranking), but do not provide a possible...... explanation of how these objects deviate from the rest of the data. Such explanations would help user to interpret or validate the detected outliers. The problem addressed in this paper is as follows: given an outlier detected by an existing algorithm, we propose a method that determines possible explanations...... for the outlier. These explanations are expressed in the form of subspaces in which the given outlier shows separability from the inliers. In this manner, our proposed method complements existing outlier detection algorithms by providing additional information about the outliers. Our method is designed to work...
Separation vortices and pattern formation
DEFF Research Database (Denmark)
Andersen, Anders Peter; Bohr, Tomas; Schnipper, Teis
2010-01-01
In this paper examples are given of the importance of flow separation for fluid patterns at moderate Reynolds numbers—both in the stationary and in the time-dependent domain. In the case of circular hydraulic jumps, it has been shown recently that it is possible to generalise the Prandtl–Kármán–P...... results for the vortex patterns behind a flapping foil in a flowing soap film, which shows the interaction and competition between the vortices shed from the round leading edge (like the von Kármán vortex street) and those created at the sharp trailing edge.......-time evolution of the sand ripple pattern, which has the surprising features that it breaks the local sand conservation and has long-range interaction, features that can be underpinned by experiments. Very similar vortex dynamics takes place around oscillating structures such as wings and fins. Here, we present...
Separating Para and Ortho Water
Horke, Daniel A; Długołęcki, Karol; Küpper, Jochen
2014-01-01
Water exists as two nuclear-spin isomers, para and ortho, determined by the overall spin of its two hydrogen nuclei. For isolated water molecules the conversion between these isomers is forbidden and they act as different molecular species. Yet, these species are not readily separable, and little is known about their specific physical and chemical properties, conversion mechanisms, or interactions. Here we demonstrate the production of isolated samples of both spin isomers in pure beams of para and ortho water, with both species in their respective absolute ground state. These single-quantum-state samples are ideal targets for unraveling spin-conversion mechanisms, for precision spectroscopy and fundamental-symmetry-breaking studies, and for spin-enhanced applications, e. g., laboratory astrophysics and -chemistry or hypersensitized NMR experiments.
Separation of variables new trends
Sklyanin, E K
1995-01-01
The review is based on the author's papers since 1985 in which a new approach to the separation of variables (\\SoV) has being developed. It is argued that \\SoV, understood generally enough, could be the most universal tool to solve integrable models of the classical and quantum mechanics. It is shown that the standard construction of the action-angle variables from the poles of the Baker-Akhiezer function can be interpreted as a variant of \\SoV, and moreover, for many particular models it has a direct quantum counterpart. The list of the models discussed includes XXX and XYZ magnets, Gaudin model, Nonlinear Schr\\"odinger equation, SL(3)-invariant magnetic chain. New results for the 3-particle quantum Calogero-Moser system are reported.
SEPARATION PROCESS FOR THORIUM SALTS
Bridger, G.L.; Whatley, M.E.; Shaw, K.G.
1957-12-01
A process is described for the separation of uranium, thorium, and rare earths extracted from monazite by digesting with sulfuric acid. By carefully increasing the pH of the solution, stepwise, over the range 0.8 to 5.5, a series of selective precipitations will be achieved, with the thorium values coming out at lower pH, the rare earths at intermediate pH and the uranium last. Some mixed precipitates will be obtained, and these may be treated by dissolving in HNO/sub 3/ and contacting with dibutyl phosphate, whereby thorium or uranium are taken up by the organic phase while the rare earths preferentially remain in the aqueous solution.
Olefin separation membrane and process
Pinnau, Ingo; Toy, Lora G.; Casillas, Carlos
1997-01-01
A membrane and process for separating unsaturated hydrocarbons from fluid mixtures. The membrane and process differ from previously known membranes and processes, in that the feed and permeate streams can both be dry, the membrane need not be water or solvent swollen, and the membrane is characterized by a selectivity for an unsaturated hydrocarbon over a saturated hydrocarbon having the same number of carbon atoms of at least about 20, and a pressure-normalized flux of said unsaturated hydrocarbon of at least about 5.times.10.sup.-6 cm.sup.3 (STP)/cm.sup.2 .multidot.s.multidot.cmHg, said flux and selectivity being measured with a gas mixture containing said unsaturated and saturated hydrocarbons, and in a substantially dry environment.
Shell Separation for Mirror Replication
1999-01-01
NASA's Space Optics Manufacturing Center has been working to expand our view of the universe via sophisticated new telescopes. The Optics Center's goal is to develop low-cost, advanced space optics technologies for the NASA program in the 21st century - including the long-term goal of imaging Earth-like planets in distant solar systems. To reduce the cost of mirror fabrication, Marshall Space Flight Center (MSFC) has developed replication techniques, the machinery, and materials to replicate electro-formed nickel mirrors. Optics replication uses reusable forms, called mandrels, to make telescope mirrors ready for final finishing. MSFC optical physicist Bill Jones monitors a device used to chill a mandrel, causing it to shrink and separate from the telescope mirror without deforming the mirror's precisely curved surface.
Separating detection and catalog production
Akhlaghi, Mohammad
2016-01-01
In the coming era of massive surveys (e.g. LSST, SKA), the role of the database designers and the algorithms they choose to adopt becomes the decisive factor in scientific progress. Systems that allow/encourage users/scientists to be more creative with the reduction/analysis algorithms can greatly enhance scientific productivity. The separation/modularity of the detection processes and catalog production is one proposal for achieving `Reduction/analysis algorithms for large databases and vice versa' (a key theme for the 26th ADASS). With the new noise-based detection paradigm, non-parametric detection is now possible for astronomical objects to very low surface brightness limits. In our implementation, one software (NoiseChisel) is in charge of detection and another (MakeCatalog) is in charge of catalog production. This modularity has many advantages for pipeline developers, and more importantly, it empowers scientific curiosity and creativity.
A Building Connecting Separated Communities
DEFF Research Database (Denmark)
Axel, Erik
Producing something for general use involves the designers' anticipation of the use of the object. Personal as well as professional experience is involved in the design anticipations of the process. Using an object means exploring it as a concrete arrangement for our everyday conduct of life....... Living in a house means staying in a place, formed by experiences and anticipations of different ways of living, of social regulations of who can be where, and used for varied concrete purposes. Professionals in the construction business build houses for living, for working, for events etc....... in no systematic sequence. This, among other things, separates design and use, which is worth investigating in order to understand the problems involved in connecting the design of a house and analyzing the experience of a user. We undertook a preliminary investigation of how a dormitory for visiting students from...
Origins and Evolution of Inorganic-Based and MOF-Based Mixed-Matrix Membranes for Gas Separations
National Research Council Canada - National Science Library
Perez, Edson; Karunaweera, Chamaal; Musselman, Inga; Balkus, Kenneth; Ferraris, John
2016-01-01
.... Among the separation methods currently being used, like distillation, amine scrubbing, and pressure and temperature swing adsorption, membrane-based gas separation has the potential to meet these demands...
Evaluation of Mars CO2 Capture and Gas Separation Technologies
Muscatello, Anthony C.; Santiago-Maldonado, Edgardo; Gibson, Tracy; Devor, Robert; Captain, James
2011-01-01
Recent national policy statements have established that the ultimate destination of NASA's human exploration program is Mars. In Situ Resource Utilization (ISRU) is a key technology required to ,enable such missions and it is appropriate to review progress in this area and continue to advance the systems required to produce rocket propellant, oxygen, and other consumables on Mars using the carbon dioxide atmosphere and other potential resources. The Mars Atmospheric Capture and Gas separation project is selecting, developing, and demonstrating techniques to capture and purify Martian atmospheric gases for their utilization for the production of hydrocarbons, oxygen, and water in ISRU systems. Trace gases will be required to be separated from Martian atmospheric gases to provide pure CO2 to processing elements. In addition, other Martian gases, such as nitrogen and argon, occur in concentrations high enough to be useful as buffer gas and should be captured as well. To achieve these goals, highly efficient gas separation processes will be required. These gas separation techniques are also required across various areas within the ISRU project to support various consumable production processes. The development of innovative gas separation techniques will evaluate the current state-of-the-art for the gas separation required, with the objective to demonstrate and develop light-weight, low-power methods for gas separation. Gas separation requirements include, but are not limited to the selective separation of: (1) methane and water from unreacted carbon oxides (C02-CO) and hydrogen typical of a Sabatier-type process, (2) carbon oxides and water from unreacted hydrogen from a Reverse Water-Gas Shift process, (3)/carbon oxides from oxygen from a trash/waste processing reaction, and (4) helium from hydrogen or oxygen from a propellant scavenging process. Potential technologies for the separations include' freezers, selective membranes, selective solvents, polymeric sorbents
Activated Carbon Composites for Air Separation
Energy Technology Data Exchange (ETDEWEB)
Baker, Frederick S [ORNL; Contescu, Cristian I [ORNL; Tsouris, Costas [ORNL; Burchell, Timothy D [ORNL
2011-09-01
Coal-derived synthesis gas is a potential major source of hydrogen for fuel cells. Oxygen-blown coal gasification is an efficient approach to achieving the goal of producing hydrogen from coal, but a cost-effective means of enriching O2 concentration in air is required. A key objective of this project is to assess the utility of a system that exploits porous carbon materials and electrical swing adsorption to produce an O2-enriched air stream for coal gasification. As a complement to O2 and N2 adsorption measurements, CO2 was used as a more sensitive probe molecule for the characterization of molecular sieving effects. To further enhance the potential of activated carbon composite materials for air separation, work was implemented on incorporating a novel twist into the system; namely the addition of a magnetic field to influence O2 adsorption, which is accompanied by a transition between the paramagnetic and diamagnetic states. The preliminary findings in this respect are discussed.
Shameful Separations and Embarrassing Proximities
DEFF Research Database (Denmark)
Frederiksen, Maja Bissenbakker
2012-01-01
This article introduces various theories of shame as they figure within a queer theoretical framework. Drawing on E.K. Sedgwick’s thinking, shame is presented as a theory of nonnormative subject formation that holds potential for political activist thinking. Rather than regarding shame as an inner...
Mesoporous Cladophora cellulose separators for lithium-ion batteries
Pan, Ruijun; Cheung, Ocean; Wang, Zhaohui; Tammela, Petter; Huo, Jinxing; Lindh, Jonas; Edström, Kristina; Strømme, Maria; Nyholm, Leif
2016-07-01
Much effort is currently made to develop inexpensive and renewable materials which can replace the polyolefin microporous separators conventionally used in contemporary lithium-ion batteries. In the present work, it is demonstrated that mesoporous Cladophora cellulose (CC) separators constitute very promising alternatives based on their high crystallinity, good thermal stability and straightforward manufacturing. The CC separators, which are fabricated using an undemanding paper-making like process involving vacuum filtration, have a typical thickness of about 35 μm, an average pore size of about 20 nm, a Young's modulus of 5.9 GPa and also exhibit an ionic conductivity of 0.4 mS cm-1 after soaking with 1 M LiPF6 EC: DEC (1/1, v/v) electrolyte. The CC separators are demonstrated to be thermally stable at 150 °C and electrochemically inert in the potential range between 0 and 5 V vs. Li+/Li. A LiFePO4/Li cell containing a CC separator showed good cycling stability with 99.5% discharge capacity retention after 50 cycles at a rate of 0.2 C. These results indicate that the renewable CC separators are well-suited for use in high-performance lithium-ion batteries.
Temperature-responsive chromatography for the separation of biomolecules.
Kanazawa, Hideko; Okano, Teruo
2011-12-09
Temperature-responsive chromatography for the separation of biomolecules utilizing poly(N-isopropylacrylamide) (PNIPAAm) and its copolymer-modified stationary phase is performed with an aqueous mobile phase without using organic solvent. The surface properties and function of the stationary phase are controlled by external temperature changes without changing the mobile-phase composition. This analytical system is based on nonspecific adsorption by the reversible transition of a hydrophilic-hydrophobic PNIPAAm-grafted surface. The driving force for retention is hydrophobic interaction between the solute molecules and the hydrophobized polymer chains on the stationary phase surface. The separation of the biomolecules, such as nucleotides and proteins was achieved by a dual temperature- and pH-responsive chromatography system. The electrostatic and hydrophobic interactions could be modulated simultaneously with the temperature in an aqueous mobile phase, thus the separation system would have potential applications in the separation of biomolecules. Additionally, chromatographic matrices prepared by a surface-initiated atom transfer radical polymerization (ATRP) exhibit a strong interaction with analytes, because the polymerization procedure forms a densely packed polymer, called a polymer brush, on the surfaces. The copolymer brush grafted surfaces prepared by ATRP was an effective tool for separating basic biomolecules by modulating the electrostatic and hydrophobic interactions. Applications of thermally responsive columns for the separations of biomolecules are reviewed here.
In-Plant Testing of High-Efficiency Hydraulic Separators
Energy Technology Data Exchange (ETDEWEB)
G. H. Luttrell; R. Q. Honaker; R. C. Bratton; T. C. Westerfield; J. N. Kohmuench
2006-06-30
Hydraulic separators are commonly used for particle size classification and gravity concentration of minerals and coal. Unfortunately, the efficiency of these processes can be quite low due to poor equipment design and variations in feed consistency. To help alleviate these problems, an industry-driven R&D program has been undertaken to develop a new generation of hydraulic separators that are more efficient and less costly to operate and maintain. These units, which are commercially called the CrossFlow separator and HydroFloat separator, have the potential to improve performance (separation efficiency and throughput) and reduce operating costs (power consumption, water and reagent usage). In Phase I of this project, laboratory and pilot-scale test units were evaluated at various industrial sites in both the coal and mineral industries. Based on promising results obtained from Phase I, full-scale prototypes were purchased and installed by a major U.S. phosphate producer and a large eastern U.S. coal company. The test data obtained from these sites demonstrate that significant performance improvements can be realized through the application of these high-efficiency separators.
IN-PLANT TESTING OF HIGH-EFFICIENCY HYDRAULIC SEPARATORS
Energy Technology Data Exchange (ETDEWEB)
G.H. Luttrell; R.Q. Honaker; R.C. Bratton; T.C. Westerfield; J.N. Kohmuench
2006-05-22
Hydraulic separators are commonly used for particle size classification and gravity concentration of minerals and coal. Unfortunately, the efficiency of these processes can be quite low due to poor equipment design and variations in feed consistency. To help alleviate these problems, an industry-driven R&D program has been undertaken to develop a new generation of hydraulic separators that are more efficient and less costly to operate and maintain. These units, which are commercially called the CrossFlow separator and HydroFloat separator, have the potential to improve performance (separation efficiency and throughput) and reduce operating costs (power consumption, water and reagent usage). In Phase I of this project, laboratory and pilot-scale test units were evaluated at various industrial sites in both the coal and mineral industries. Based on promising results obtained from Phase I, full-scale prototypes were purchased and installed by a major U.S. phosphate producer and a large eastern U.S. coal company. The test data obtained from these sites demonstrate that significant performance improvements can be realized through the application of these high-efficiency separators.