Quantum oscillation and the Aharonov-Bohm effect in a multiply connected normal-conductor loop

NASA Astrophysics Data System (ADS)

Takai, Daisuke; Ohta, Kuniichi

1994-12-01

The magnetostatic and electrostatic Aharonov-Bohm (AB) effects in multiply connected normal-conductor rings are studied. A previously developed model of a single mesoscopic ring is generalized to include an arbitrary number of rings, and the oscillatory behavior of the total transmission coefficients for the serially connected N (N is equal to integer) rings are derived as a function of the magnetic flux threading each ring and as a function of the electrostatic potential applied to the rings. It is shown that quantum oscillation of multiple rings exhibits greater variety of behavior than in periodic superlattices. We investigate the influence of the scattering at a junction and the number of atoms in the ring in both magnetostatic and electrostatic oscillation of multiring systems. For the electrostatic AB effects, when scattering occurs at the junctions between the connecting wire and the ring, the conductance in the AB oscillation is modified to an N-1 peaked shape. It is shown that this oscillatory behavior is greatly influenced by the number of atoms in the ring and is controlled by the electrostatic potential or magnetic flux that is applied to the ring. We discuss the behavior of the quantum oscillations upon varying the number of connected rings and the number of minibands.

The Aharonov-Bohm oscillation in the BiSbTe3 topological insulator macroflake

NASA Astrophysics Data System (ADS)

Huang, Shiu-Ming; Wang, Pin-Chun; Lin, Chien; You, Sheng-Yu; Lin, Wei-Cheng; Lin, Lin-Jie; Yan, You-Jhih; Yu, Shih-Hsun; Chou, M. C.

2018-05-01

We report the Aharonov-Bohm (AB) oscillation in the BiSbTe3 topological insulator macroflake. The magnetoresistance reveals periodic oscillations. The oscillation index number reveals the Berry phase is π which supports the oscillation originates from the surface state. The AB oscillation frequency increases as temperature decreases, and the corresponding phase coherence length is consistent with that extracted from the weak antilocalization. The phase coherence length is proportional to T-1/2. The magnetoresistance ratio reaches 700% (1000%) at 9 T (14 T) and 2 K, and it is proportional to the carrier mobility. The magnetoresistance ratio is larger than all reported values in (Bi, Sb)2(Te, Se)3 topological insulators.

Effective beam separation schemes for the measurement of the electric Aharonov-Bohm effect in an ion interferometer.

PubMed

Schütz, G; Rembold, A; Pooch, A; Prochel, H; Stibor, A

2015-11-01

We propose an experiment for the first proof of the type I electric Aharonov-Bohm effect in an ion interferometer for hydrogen. The performances of three different beam separation schemes are simulated and compared. The coherent ion beam is generated by a single atom tip (SAT) source and separated by either two biprisms with a quadrupole lens, two biprisms with an einzel-lens or three biprisms. The beam path separation is necessary to introduce two metal tubes that can be pulsed with different electric potentials. The high time resolution of a delay line detector allows to work with a continuous ion beam and circumvents the pulsed beam operation as originally suggested by Aharonov and Bohm. We demonstrate that the higher mass and therefore lower velocity of ions compared to electrons combined with the high expected SAT ion emission puts the direct proof of this quantum effect for the first time into reach of current technical possibilities. Thereby a high detection rate of coherent ions is crucial to avoid long integration times that allow the influence of dephasing noise from the environment. We can determine the period of the expected matter wave interference pattern and the signal on the detector by determining the superposition angle of the coherent partial beams. Our simulations were tested with an electron interferometer setup and agree with the experimental results. We determine the separation scheme with three biprisms to be most efficient and predict a total signal acquisition time of only 80s to measure a phase shift from 0 to 2π due to the electric Aharonov-Bohm effect. Copyright © 2015 Elsevier B.V. All rights reserved.

The interplay between the Aharonov-Bohm interference and parity selective tunneling in graphene nanoribbon rings.

PubMed

Nguyen, V Hung; Niquet, Y-M; Dollfus, P

2014-05-21

We report on a numerical study of the Aharonov-Bohm (AB) effect and parity selective tunneling in pn junctions based on rectangular graphene rings where the contacts and ring arms are all made of zigzag nanoribbons. We find that when applying a magnetic field to the ring, the AB interference can reverse the parity symmetry of incoming waves and hence can strongly modulate the parity selective transmission through the system. Therefore, the transmission between two states of different parity exhibits the AB oscillations with a π-phase shift, compared to the case of states of the same parity. On this basis, it is shown that interesting effects, such as giant (both positive and negative) magnetoresistance and strong negative differential conductance, can be achieved in this structure. Our study thus presents a new property of the AB interference in graphene nanorings, which could be helpful for further understanding the transport properties of graphene mesoscopic systems.

Distinguishability of stacks in ZnTe/ZnSe quantum dots via spectral analysis of Aharonov-Bohm oscillations

NASA Astrophysics Data System (ADS)

Roy, Bidisha; Ji, Haojie; Dhomkar, Siddharth; Cadieu, Fred J.; Peng, Le; Moug, Richard; Tamargo, Maria C.; Kuskovsky, Igor L.

2013-02-01

A spectral analysis of the Aharonov-Bohm (AB) oscillations in photoluminescence intensity was performed for stacked type-II ZnTe/ZnSe quantum dots (QDs) fabricated within multilayered Zn-Se-Te system with sub-monolayer insertions of Te. Robust AB oscillations allowed for fine probing of distinguishable QDs stacks within the ensemble of QDs. The AB transition magnetic field, B AB , changed from the lower energy side to the higher energy side of the PL spectra revealing the presence of different sets of QDs stacks. The change occurs within the spectral range, where the contributing green and blue bands of the spectra overlapped. "Bundling" in lifetime measurements is seen at transition spectral regions confirming the results.

Detecting coupling of Majorana bound states with an Aharonov-Bohm interferometer

NASA Astrophysics Data System (ADS)

Ramos-Andrade, J. P.; Orellana, P. A.; Ulloa, S. E.

2018-01-01

We study the transport properties of an interferometer composed by a quantum dot (QD) coupled with two normal leads and two one-dimensional topological superconductor nanowires (TNWs) hosting Majorana bound states (MBS) at their ends. The geometry considered is such that one TNW has both ends connected with the QD, forming an Aharonov-Bohm (AB) interferometer threaded by an external magnetic flux, while the other TNW is placed near the interferometer TNW. This geometry can alternatively be seen as a long wire contacted across a local defect, with possible coupling between independent-MBS. We use the Green’s function formalism to calculate the conductance across normal current leads on the QD. We find that the conductance exhibits a half-quantum value regardless of the AB phase and location of the dot energy level, whenever the interferometer configuration interacts with the neighboring TNW. These findings suggest that such a geometry could be used for a sensitive detection of MBS interactions across TNWs, exploiting the high sensitivity of conductance to the AB phase in the interferometer.

The observation of the Aharonov-Bohm effect in suspended semiconductor ring interferometers

NASA Astrophysics Data System (ADS)

Pokhabov, D. A.; Pogosov, A. G.; Shevyrin, A. A.; Zhdanov, E. Yu; Bakarov, A. K.; Shklyaev, A. A.; Ishutkin, S. V.; Stepanenko, M. V.; Shesterikov, E. V.

2018-02-01

A suspended semiconductor quantum ring interferometer based on a GaAs/AlGaAs heterostructure with a two-dimensional electron gas (2DEG) is created and experimentally studied. The electron interference in suspended 2DEG is observed. The interference manifests itself as the Aharonov-Bohm oscillations of the interferometer magnetoresistance, clearly observed before as well as after suspension. The amplitude of the oscillations remains almost unchanged after suspension.

Thermoelectric effect in an Aharonov-Bohm ring with an embedded quantum dot

PubMed Central

2012-01-01

Thermoelectric effect is studied in an Aharonov-Bohm interferometer with an embedded quantum dot (QD) in the Coulomb blockade regime. The electrical conductance, electron thermal conductance, thermopower, and thermoelectric figure-of-merit are calculated by using the Keldysh Green's function method. It is found that the figure-of-merit ZT of the QD ring may be quite high due to the Fano effect originated from the quantum interference effect. Moreover, the thermoelectric efficiency is sensitive to the magnitude of the dot-lead and inter-lead coupling strengthes. The effect of intradot Coulomb repulsion on ZT is significant in the weak-coupling regime, and then large ZT values can be obtained at rather high temperature. PMID:22369454

Thermoelectric effect in an Aharonov-Bohm ring with an embedded quantum dot.

PubMed

Zheng, Jun; Chi, Feng; Lu, Xiao-Dong; Zhang, Kai-Cheng

2012-02-28

Thermoelectric effect is studied in an Aharonov-Bohm interferometer with an embedded quantum dot (QD) in the Coulomb blockade regime. The electrical conductance, electron thermal conductance, thermopower, and thermoelectric figure-of-merit are calculated by using the Keldysh Green's function method. It is found that the figure-of-merit ZT of the QD ring may be quite high due to the Fano effect originated from the quantum interference effect. Moreover, the thermoelectric efficiency is sensitive to the magnitude of the dot-lead and inter-lead coupling strengthes. The effect of intradot Coulomb repulsion on ZT is significant in the weak-coupling regime, and then large ZT values can be obtained at rather high temperature.

Topological phases reviewed: The Aharonov Bohm, Aharonov Casher, and He McKellar Wilkens phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKellar, B. H. J.; He, X-G.; Klein, A. G.

2014-03-05

There are three topological phases related to electromagnetic interactions in quantum mechanics: 1. The Aharonov Bohm phase acquired when a charged particle encircles a magnetic field but travels through a field free region. 2. The Aharonov Casher phase acquired when a magnetic dipole encircles electric charges but travels through a charge free region. 3. The He McKellar Wilkens phase acquired when an electric dipole encircles magnetic charges but travels through a charge free region. We review the conditions under which these phases are indeed topological and their experimental realisation. Because the He McKellar Wilkens phase has been recently observed wemore » pay particular attention to how the basic concept of 'an electric dipole encircles magnetic charges' was realised experimentally, and discuss possible future experimental realisations.« less

A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms

NASA Astrophysics Data System (ADS)

Huo, Ming-Xia; Nie, Wei; Hutchinson, David A. W.; Kwek, Leong Chuan

2014-08-01

Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a ``hairline'' solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions.

A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms.

PubMed

Huo, Ming-Xia; Nie, Wei; Hutchinson, David A W; Kwek, Leong Chuan

2014-08-08

Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a "hairline" solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions.

Hydrogen atom in a quantum plasma environment under the influence of Aharonov-Bohm flux and electric and magnetic fields.

PubMed

Falaye, Babatunde James; Sun, Guo-Hua; Silva-Ortigoza, Ramón; Dong, Shi-Hai

2016-05-01

This study presents the confinement influences of Aharonov-Bohm (AB) flux and electric and magnetic fields directed along the z axis and encircled by quantum plasmas on the hydrogen atom. The all-inclusive effects result in a strongly attractive system while the localizations of quantum levels change and the eigenvalues decrease. We find that the combined effect of the fields is stronger than a solitary effect and consequently there is a substantial shift in the bound state energy of the system. We also find that to perpetuate a low-energy medium for the hydrogen atom in quantum plasmas, a strong electric field and weak magnetic field are required, whereas the AB flux field can be used as a regulator. The application of the perturbation technique utilized in this paper is not restricted to plasma physics; it can also be applied in molecular physics.

High-sensitivity rotation sensing with atom interferometers using Aharonov-Bohm effect

NASA Astrophysics Data System (ADS)

Özcan, Meriac

2006-02-01

In recent years there has been significant activity in research and development of high sensitivity accelerometers and gyroscopes using atom interferometers. In these devices, a fringe shift in the interference of atom de Broglie waves indicates the rotation rate of the interferometer relative to an inertial frame of reference. In both optical and atomic conventional Sagnac interferometers, the resultant phase difference due to rotation is independent of the wave velocity. However, we show that if an atom interforemeter is enclosed in a Faraday cage which is at some potential, the phase difference of the counter-propagating waves is proportional to the inverse square of the particle velocity and it is proportional to the applied potential. This is due to Aharonov-Bohm effect and it can be used to increase the rotation sensitivity of atom interferometers.

A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms

PubMed Central

Huo, Ming-Xia; Nie, Wei; Hutchinson, David A. W.; Kwek, Leong Chuan

2014-01-01

Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a “hairline” solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions. PMID:25103877

Conductance of closed and open long Aharonov-Bohm-Kondo rings

NASA Astrophysics Data System (ADS)

Shi, Zheng; Komijani, Yashar

2017-02-01

We calculate the finite temperature linear dc conductance of a generic single-impurity Anderson model containing an arbitrary number of Fermi liquid leads, and apply the formalism to closed and open long Aharonov-Bohm-Kondo (ABK) rings. We show that, as with the short ABK ring, there is a contribution to the conductance from the connected four-point Green's function of the conduction electrons. At sufficiently low temperatures this contribution can be eliminated, and the conductance can be expressed as a linear function of the T matrix of the screening channel. For closed rings we show that at temperatures high compared to the Kondo temperature, the conductance behaves differently for temperatures above and below vF/L , where vF is the Fermi velocity and L is the circumference of the ring. For open rings, when the ring arms have both a small transmission and a small reflection, we show from the microscopic model that the ring behaves like a two-path interferometer, and that the Kondo temperature is unaffected by details of the ring. Our findings confirm that ABK rings are potentially useful in the detection of the size of the Kondo screening cloud, the π /2 scattering phase shift from the Kondo singlet, and the suppression of Aharonov-Bohm oscillations due to inelastic scattering.

Enhanced spin figure of merit in an Aharonov-Bohm ring with a double quantum dot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Xingfei; Qi, Fenghua; Jin, Guojun, E-mail: gjin@nju.edu.cn

2014-04-21

We theoretically investigate the thermoelectric effects in an Aharonov-Bohm ring with a serially coupled double quantum dot embedded in one arm. An external magnetic field is perpendicularly applied to the two dots. Using the nonequilibrium Green's function method in the linear-response regime, we calculate the charge and spin figures of merit. When the energy levels of the two quantum dots are equal and the system is connected to two normal leads, a large spin figure of merit (Z{sub s}T ≈ 4.5) accompanying with a small charge figure of merit (Z{sub c}T ≈ 0) can be generated due to the remarkable bipolar effect. Further, whenmore » the system is connected to two ferromagnetic leads, the spin figure of merit can reach even a higher value about 9. Afterwards, we find that Z{sub s}T is enhanced while Z{sub c}T is reduced in the coaction of the Aharonov-Bohm flux and Rashba spin-orbit coupling. It is argued that the bipolar effect is positive (negative) to spin (charge) figure of merit in the presence of level detuning of the two quantum dots and intradot Coulomb interactions, respectively. Also, we propose a possible experiment to verify our results.« less

Aharonov-Bohm effect in the tunnelling of a quantum rotor in a linear Paul trap.

PubMed

Noguchi, Atsushi; Shikano, Yutaka; Toyoda, Kenji; Urabe, Shinji

2014-05-13

Quantum tunnelling is a common fundamental quantum mechanical phenomenon that originates from the wave-like characteristics of quantum particles. Although the quantum tunnelling effect was first observed 85 years ago, some questions regarding the dynamics of quantum tunnelling remain unresolved. Here we realize a quantum tunnelling system using two-dimensional ionic structures in a linear Paul trap. We demonstrate that the charged particles in this quantum tunnelling system are coupled to the vector potential of a magnetic field throughout the entire process, even during quantum tunnelling, as indicated by the manifestation of the Aharonov-Bohm effect in this system. The tunnelling rate of the structures periodically depends on the strength of the magnetic field, whose period is the same as the magnetic flux quantum φ0 through the rotor [(0.99 ± 0.07) × φ0].

Measurement of Aharonov-Casher effect in a Josephson junction chain

NASA Astrophysics Data System (ADS)

Pop, Ioan Mihai; Lecocq, Florent; Pannetier, Bernard; Buisson, Olivier; Guichard, Wiebke

2011-03-01

We have recently measured the effect of superconducting phase-slips on the ground state of a Josephson junction chain and a rhombi chain. Here we report clear evidence of Aharonov-Casher effect in a chain of Josephson junctions. This phenomenon is the dual of the well known Aharonov-Bohm interference. Using a capacitively coupled gate to the islands of the chain, we induce oscillations of the supercurrent by tuning the polarization charges on the islands. We observe complex interference patterns for different quantum phase slip amplitudes, that we understand quantitatively as Aharonov-Casher vortex interferences. European STREP MIDAS.

Elementary Aharonov-Bohm system in three space dimensions: Quantum attraction with no classical force

NASA Astrophysics Data System (ADS)

Goldhaber, Alfred; Requist, Ryan

2003-07-01

As a consequence of the Aharonov-Bohm effect, there is a quantum-induced attraction between a charged particle and a rigid, impenetrable hoop made from an arbitrarily thin tube containing a superconductor quantum of magnetic flux. This is remarkable because in classical physics there is no force between the two objects, and quantum-mechanical effects (associated with uncertainty-principle energy) generally are repulsive rather than attractive. For an incident spinless charged particle in a P wave (in a configuration with total angular momentum zero) we verify a resonance just above threshold using the Kohn variational principle in its S-matrix form. Even if optimistic choices of parameters describing a model system with these properties were feasible, the temperature required to observe the resonance would be far lower than has yet been attained in the laboratory.

Quantum geometric phase in Majorana's stellar representation: mapping onto a many-body Aharonov-Bohm phase.

PubMed

Bruno, Patrick

2012-06-15

The (Berry-Aharonov-Anandan) geometric phase acquired during a cyclic quantum evolution of finite-dimensional quantum systems is studied. It is shown that a pure quantum state in a (2J+1)-dimensional Hilbert space (or, equivalently, of a spin-J system) can be mapped onto the partition function of a gas of independent Dirac strings moving on a sphere and subject to the Coulomb repulsion of 2J fixed test charges (the Majorana stars) characterizing the quantum state. The geometric phase may be viewed as the Aharonov-Bohm phase acquired by the Majorana stars as they move through the gas of Dirac strings. Expressions for the geometric connection and curvature, for the metric tensor, as well as for the multipole moments (dipole, quadrupole, etc.), are given in terms of the Majorana stars. Finally, the geometric formulation of the quantum dynamics is presented and its application to systems with exotic ordering such as spin nematics is outlined.

Quantum Geometric Phase in Majorana's Stellar Representation: Mapping onto a Many-Body Aharonov-Bohm Phase

NASA Astrophysics Data System (ADS)

Bruno, Patrick

2012-06-01

The (Berry-Aharonov-Anandan) geometric phase acquired during a cyclic quantum evolution of finite-dimensional quantum systems is studied. It is shown that a pure quantum state in a (2J+1)-dimensional Hilbert space (or, equivalently, of a spin-J system) can be mapped onto the partition function of a gas of independent Dirac strings moving on a sphere and subject to the Coulomb repulsion of 2J fixed test charges (the Majorana stars) characterizing the quantum state. The geometric phase may be viewed as the Aharonov-Bohm phase acquired by the Majorana stars as they move through the gas of Dirac strings. Expressions for the geometric connection and curvature, for the metric tensor, as well as for the multipole moments (dipole, quadrupole, etc.), are given in terms of the Majorana stars. Finally, the geometric formulation of the quantum dynamics is presented and its application to systems with exotic ordering such as spin nematics is outlined.

Wave-packet rectification in nonlinear electronic systems: A tunable Aharonov-Bohm diode

PubMed Central

Li, Yunyun; Zhou, Jun; Marchesoni, Fabio; Li, Baowen

2014-01-01

Rectification of electron wave-packets propagating along a quasi-one dimensional chain is commonly achieved via the simultaneous action of nonlinearity and longitudinal asymmetry, both confined to a limited portion of the chain termed wave diode. However, it is conceivable that, in the presence of an external magnetic field, spatial asymmetry perpendicular to the direction of propagation suffices to ensure rectification. This is the case of a nonlinear ring-shaped lattice with different upper and lower halves (diode), which is attached to two elastic chains (leads). The resulting device is mirror symmetric with respect to the ring vertical axis, but mirror asymmetric with respect to the chain direction. Wave propagation along the two diode paths can be modeled for simplicity by a discrete Schrödinger equation with cubic nonlinearities. Numerical simulations demonstrate that, thanks to the Aharonov-Bohm effect, such a diode can be operated by tuning the magnetic flux across the ring. PMID:24691462

Line of magnetic monopoles and an extension of the Aharonov–Bohm effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chee, J.; Lu, W.

2016-10-15

In the Landau problem on the two-dimensional plane, physical displacement of a charged particle (i.e., magnetic translation) can be induced by an in-plane electric field. The geometric phase accompanying such magnetic translation around a closed path differs from the topological phase of Aharonov and Bohm in two essential aspects: The particle is in direct contact with the magnetic field and the geometric phase has an opposite sign from the Aharonov–Bohm phase. We show that magnetic translation on the two-dimensional cylinder implemented by the Schrödinger time evolution truly leads to the Aharonov–Bohm effect. The magnetic field normal to the cylinder’s surfacemore » corresponds to a line of magnetic monopoles of uniform density whose simulation is currently under investigation in cold atom physics. In order to characterize the quantum problem, one needs to specify the value of the magnetic flux (modulo the flux unit) that threads but not in touch with the cylinder. A general closed path on the cylinder may enclose both the Aharonov–Bohm flux and the local magnetic field that is in direct contact with the charged particle. This suggests an extension of the Aharonov–Bohm experiment that naturally takes into account both the geometric phase due to local interaction with the magnetic field and the topological phase of Aharonov and Bohm.« less

Time-dependent wave packet simulations of transport through Aharanov-Bohm rings with an embedded quantum dot.

PubMed

Kreisbeck, C; Kramer, T; Molina, R A

2017-04-20

We have performed time-dependent wave packet simulations of realistic Aharonov-Bohm (AB) devices with a quantum dot embedded in one of the arms of the interferometer. The AB ring can function as a measurement device for the intrinsic transmission phase through the quantum dot, however, care has to be taken in analyzing the influence of scattering processes in the junctions of the interferometer arms. We consider a harmonic quantum dot and show how the Darwin-Fock spectrum emerges as a unique pattern in the interference fringes of the AB oscillations.

Single-slit electron diffraction with Aharonov-Bohm phase: Feynman's thought experiment with quantum point contacts.

PubMed

Khatua, Pradip; Bansal, Bhavtosh; Shahar, Dan

2014-01-10

In a "thought experiment," now a classic in physics pedagogy, Feynman visualizes Young's double-slit interference experiment with electrons in magnetic field. He shows that the addition of an Aharonov-Bohm phase is equivalent to shifting the zero-field wave interference pattern by an angle expected from the Lorentz force calculation for classical particles. We have performed this experiment with one slit, instead of two, where ballistic electrons within two-dimensional electron gas diffract through a small orifice formed by a quantum point contact (QPC). As the QPC width is comparable to the electron wavelength, the observed intensity profile is further modulated by the transverse waveguide modes present at the injector QPC. Our experiments open the way to realizing diffraction-based ideas in mesoscopic physics.

Quantum mechanical effects of topological origin

NASA Technical Reports Server (NTRS)

Duru, I. H.

1993-01-01

Following a brief review of the original Casimir and Aharonov-Bohm effects, some other effects of similar natures are mentioned. A Casimir interaction between AB fluxes is presented. Possible realizations of the Casimir effects for massive charged fields in solid state structures and a new AB effect for photons are suggested.

Properties of Type-II ZnTe/ZnSe Submonolayer Quantum Dots Studied via Excitonic Aharonov- Bohm Effect and Polarized Optical Spectroscopy

NASA Astrophysics Data System (ADS)

Ji, Haojie

In this thesis I develop understanding of the fundamental physical and material properties of type-II ZnTe/ZnSe submonolayer quantum dots (QDs), grown via combination of molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE). I use magneto-photoluminescence, including excitonic Aharonov-Bohm (AB) effect and polarized optical spectroscopy as the primary tools in this work. I present previous studies as well as the background of optical and magneto-optical processes in semiconductor nanostructures and introduce the experimental methods in Chapters 1 - 3. In Chapter 4 I focus on the excitonic AB effect in the type-II QDs. I develop a lateral tightly-bound exciton model for ZnTe/ZnSe type-II QDs, using analytical methods and numerical calculations. This explained the magneto-PL observation and allowed for establishing the size and density of the QDs in each sample based on the results of PL and magneto-PL measurements. For samples with larger QDs, I observe behaviors that fall between properties of quantum-dot and quantum-well-like systems due to increased QD densities and their type-II nature. Finally, the decoherence mechanisms of the AB excitons are investigated via the temperature dependent studies of the magneto-PL. It is determined that the AB exciton decoherence is due to transport-like (acoustic phonon) scattering of the electrons moving in the ZnSe barriers, but with substantially smaller magnitude of electron-phonon coupling constant due to relatively strong electron-hole coupling within these type-II QDs. In Chapter 5 I discuss the results of circularly polarized magneto-PL measurements. A model with ultra-long spin-flip time of holes confined to submonolayer QDs is proposed. The g-factor of type-II excitons was extracted from the Zeeman splitting and the g-factor of electrons was obtained by fitting the temperature dependence of the degree of circular polarization (DCP), from which g-factor of holes confined within ZnTe QDs was found. It is shown

Aharonov-Bohm oscillations, quantum decoherence and amplitude modulation in mesoscopic InGaAs/InAlAs rings.

PubMed

Ren, S L; Heremans, J J; Gaspe, C K; Vijeyaragunathan, S; Mishima, T D; Santos, M B

2013-10-30

Low-temperature Aharonov-Bohm oscillations in the magnetoresistance of mesoscopic interferometric rings patterned on an InGaAs/InAlAs heterostructure are investigated for their dependence on excitation current and temperature. The rings have an average radius of 650 nm, and a lithographic arm width of 300 nm, yielding pronounced interference oscillations over a wide range of magnetic fields. Apart from a current and temperature dependence, the oscillation amplitude also shows a quasi-periodic modulation with applied magnetic field. The phase coherence length is extracted by analysis of the fundamental and higher Fourier components of the oscillations, and by direct analysis of the amplitude and its dependence on parameters. It is concluded that the Thouless energy forms the measure of excitation energies for quantum decoherence. The amplitude modulation finds an explanation in the effect of the magnetic flux threading the finite width of the interferometer arms.

Reduction by symmetries in singular quantum-mechanical problems: General scheme and application to Aharonov-Bohm model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smirnov, A. G., E-mail: smirnov@lpi.ru

2015-12-15

We develop a general technique for finding self-adjoint extensions of a symmetric operator that respects a given set of its symmetries. Problems of this type naturally arise when considering two- and three-dimensional Schrödinger operators with singular potentials. The approach is based on constructing a unitary transformation diagonalizing the symmetries and reducing the initial operator to the direct integral of a suitable family of partial operators. We prove that symmetry preserving self-adjoint extensions of the initial operator are in a one-to-one correspondence with measurable families of self-adjoint extensions of partial operators obtained by reduction. The general scheme is applied to themore » three-dimensional Aharonov-Bohm Hamiltonian describing the electron in the magnetic field of an infinitely thin solenoid. We construct all self-adjoint extensions of this Hamiltonian, invariant under translations along the solenoid and rotations around it, and explicitly find their eigenfunction expansions.« less

On the Aharonov-Bohm Operators with Varying Poles: The Boundary Behavior of Eigenvalues

NASA Astrophysics Data System (ADS)

Noris, Benedetta; Nys, Manon; Terracini, Susanna

2015-11-01

We consider a magnetic Schrödinger operator with magnetic field concentrated at one point (the pole) of a domain and half integer circulation, and we focus on the behavior of Dirichlet eigenvalues as functions of the pole. Although the magnetic field vanishes almost everywhere, it is well known that it affects the operator at the spectral level (the Aharonov-Bohm effect, Phys Rev (2) 115:485-491, 1959). Moreover, the numerical computations performed in (Bonnaillie-Noël et al., Anal PDE 7(6):1365-1395, 2014; Noris and Terracini, Indiana Univ Math J 59(4):1361-1403, 2010) show a rather complex behavior of the eigenvalues as the pole varies in a planar domain. In this paper, in continuation of the analysis started in (Bonnaillie-Noël et al., Anal PDE 7(6):1365-1395, 2014; Noris and Terracini, Indiana Univ Math J 59(4):1361-1403, 2010), we analyze the relation between the variation of the eigenvalue and the nodal structure of the associated eigenfunctions. We deal with planar domains with Dirichlet boundary conditions and we focus on the case when the singular pole approaches the boundary of the domain: then, the operator loses its singular character and the k-th magnetic eigenvalue converges to that of the standard Laplacian. We can predict both the rate of convergence and whether the convergence happens from above or from below, in relation with the number of nodal lines of the k-th eigenfunction of the Laplacian. The proof relies on the variational characterization of eigenvalues, together with a detailed asymptotic analysis of the eigenfunctions, based on an Almgren-type frequency formula for magnetic eigenfunctions and on the blow-up technique.

Thouless dephasing and amplitude modulation of Aharonov-Bohm oscillations in mesoscopic InGaAs/InAlAs interferometers

NASA Astrophysics Data System (ADS)

Heremans, J. J.; Ren, S. L.; Zhang, Yao; Gaspe, C. K.; Vijeyaragunathan, S.; Mishima, T. D.; Santos, M. B.

2014-03-01

Aharonov-Bohm oscillations in the low-temperature magnetoresistance of mesoscopic interferometric rings are investigated for their dependence on bias current and temperature, and to explore origins of the observed amplitude modulation in magnetic field. Single-ring interferometers of radius 650 nm and lithographic arm width 300 nm were fabricated on a high-mobility high-density InGaAs/InAlAs heterostructure. The rings show interference oscillations over a wide range of magnetic fields, with amplitudes subject to modulation with applied magnetic field. The quantum phase coherence length is extracted by analysis of the fundamental and higher Fourier components of the oscillations, and by comparative study of the amplitude. The variation of the amplitude with bias current and temperature shows the existence of a critical excitation energy consistent with the Thouless energy for quantum phase smearing. Autocorrelation and Fourier analysis are used to determine the quasi-period of the amplitude modulation, which is found to be consistent with an origin in the magnetic flux threading the finite width of the interferometer arms, changing the mesoscopic realization of the system. Supported by DOE DE-FG02-08ER46532 (VT) and NSF DMR-0520550 (UoO).

Photonic Aharonov–Bohm effect in photon–phonon interactions

PubMed Central

Li, Enbang; Eggleton, Benjamin J.; Fang, Kejie; Fan, Shanhui

2014-01-01

The Aharonov–Bohm effect is one of the most intriguing phenomena in both classical and quantum physics, and associates with a number of important and fundamental issues in quantum mechanics. The Aharonov–Bohm effects of charged particles have been experimentally demonstrated and found applications in various fields. Recently, attention has also focused on the Aharonov–Bohm effect for neutral particles, such as photons. Here we propose to utilize the photon–phonon interactions to demonstrate that photonic Aharonov–Bohm effects do exist for photons. By introducing nonreciprocal phases for photons, we observe experimentally a gauge potential for photons in the visible range based on the photon–phonon interactions in acousto-optic crystals, and demonstrate the photonic Aharonov–Bohm effect. The results presented here point to new possibilities to control and manipulate photons by designing an effective gauge potential. PMID:24476790

On the incorporation of the geometric phase in general single potential energy surface dynamics: A removable approximation to ab initio data.

PubMed

Malbon, Christopher L; Zhu, Xiaolei; Guo, Hua; Yarkony, David R

2016-12-21

For two electronic states coupled by conical intersections, the line integral of the derivative coupling can be used to construct a complex-valued multiplicative phase factor that makes the real-valued adiabatic electronic wave function single-valued, provided that the curl of the derivative coupling is zero. Unfortunately for ab initio determined wave functions, the curl is never rigorously zero. However, when the wave functions are determined from a coupled two diabatic state Hamiltonian H d (fit to ab initio data), the resulting derivative couplings are by construction curl free, except at points of conical intersection. In this work we focus on a recently introduced diabatization scheme that produces the H d by fitting ab initio determined energies, energy gradients, and derivative couplings to the corresponding H d determined quantities in a least squares sense, producing a removable approximation to the ab initio determined derivative coupling. This approach and related numerical issues associated with the nonremovable ab initio derivative couplings are illustrated using a full 33-dimensional representation of phenol photodissociation. The use of this approach to provide a general framework for treating the molecular Aharonov Bohm effect is demonstrated.

The Aharonov–Bohm effect in scattering theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sitenko, Yu.A., E-mail: yusitenko@bitp.kiev.ua; Vlasii, N.D.

2013-12-15

The Aharonov–Bohm effect is considered as a scattering event with nonrelativistic charged particles of the wavelength which is less than the transverse size of an impenetrable magnetic vortex. The quasiclassical WKB method is shown to be efficient in solving this scattering problem. We find that the scattering cross section consists of two terms, one describing the classical phenomenon of elastic reflection and another one describing the quantum phenomenon of diffraction; the Aharonov–Bohm effect is manifested as a fringe shift in the diffraction pattern. Both the classical and the quantum phenomena are independent of the choice of a boundary condition atmore » the vortex edge, providing that probability is conserved. We show that a propagation of charged particles can be controlled by altering the flux of a magnetic vortex placed on their way. -- Highlights: •Aharonov–Bohm effect as a scattering event. •Impenetrable magnetic vortex of nonzero transverse size. •Scattering cross section is independent of a self-adjoint extension employed. •Classical phenomenon of elastic reflection and quantum phenomenon of diffraction. •Aharonov–Bohm effect as a fringe shift in the diffraction pattern.« less

Unique spin-polarized transmission effects in a QD ring structure

NASA Astrophysics Data System (ADS)

Hedin, Eric; Joe, Yong

2010-10-01

Spintronics is an emerging field in which the spin of the electron is used for switching purposes and to communicate information. In order to obtain spin-polarized electron transmission, the Zeeman effect is employed to produce spin-split energy states in quantum dots which are embedded in the arms of a mesoscopic Aharonov-Bohm (AB) ring heterostructure. The Zeeman splitting of the QD energy levels can be induced by a parallel magnetic field, or by a perpendicular field which also produces AB-effects. The combination of these effects on the transmission resonances of the structure is studied analytically and several parameter regimes are identified which produce a high degree of spin-polarized output. Contour and line plots of the weighted spin polarization as a function of electron energy and magnetic field are presented to visualize the degree of spin-polarization. Taking advantage of these unique parameter regimes shows the potential promise of such devices for producing spin-polarized currents.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voskoboynikov, O., E-mail: vam@faculty.nctu.edu.tw

We theoretically investigate suppression and recovery of the Aharonov-Bohm oscillations of the diamagnetic response of electrons (holes) confined in self-assembled In{sub c}Ga{sub 1−c}As/GaAs semiconductor reflection asymmetrical quantum rings. Based on the mapping method and gauge-origin-independent definition for the magnetic vector potential we simulate the energies and wave functions of the electron (hole) under external magnetic and electric fields. We examine the transformation of the ground state wave function of the electron (hole) in reflection asymmetrical rings from localized in one of the potential valleys (dotlike shape of the wave function) to distributed over all volume of the ring (ringlike shape)more » under an appropriate lateral electric field. This transformation greatly recovers the electron (hole) diamagnetic coefficient and Aharonov-Bohm oscillations of the diamagnetic response of the ring. However, the recovering electric field for the first Aharonov-Bohm diamagnetic oscillation of the electron is a suppressing one for the hole (and vice versa). This can block the recovery of the optical Aharonow-Bohm effect in In{sub c}Ga{sub 1−c}As/GaAs asymmetrically wobbled rings. However, the recovery of the Aharonov-Bohm oscillations for the independent electron (hole) by the external electric field remains interesting and feasible objective for the asymmetric rings.« less

Effective tuning of electron charge and spin distribution in a dot-ring nanostructure at the ZnO interface

NASA Astrophysics Data System (ADS)

Chakraborty, Tapash; Manaselyan, Aram; Barseghyan, Manuk

2018-05-01

Electronic states and the Aharonov-Bohm effect in ZnO quantum dot-ring nanostructures containing few interacting electrons reveal several unique features. We have shown here that in contrast to the dot-rings made of conventional semiconductors, such as InAs or GaAs, the dot-rings in ZnO heterojunctions demonstrate several unique characteristics due to the unusual properties of quantum dots and rings in ZnO. In particular the energy spectra of the ZnO dot-ring and the Aharnov-Bohm oscillations are strongly dependant on the electron number in the dot or in the ring. Therefore even small changes of the confinement potential, sizes of the dot-ring or the magnetic field can drastically change the energy spectra and the behavior of Aharonov-Bohm oscillations in the system. Due to this interesting phenomena it is possible to effectively control with high accuracy the electron charge and spin distribution inside the dot-ring structure. This controlling can be achieved either by changing the magnetic field or the confinement potentials.

Flux-dependent anti-crossing of resonances in parallel non-coupled double quantum dots

NASA Astrophysics Data System (ADS)

Joe, Yong S.; Hedin, Eric R.; Kim, Jiseok

2008-08-01

We present novel resonant phenomena through parallel non-coupled double quantum dots (QDs) embedded in each arm of an Aharonov-Bohm (AB) ring with magnetic flux passing through its center. The electron transmission through this AB ring with each QD formed by two short-range potential barriers is calculated using a scattering matrix at each junction and a transfer matrix in each arm. We show that as the magnetic flux modulates, a distortion of the grid-like square transmission occurs and an anti-crossing of the resonances appears. Hence, the modulation of magnetic flux in this system can have an equivalent effect to the control of inter-dot coupling between the two QDs.

Quantum Effects of Electric Fields and Potentials on Electron Motion: An Introduction to Theoretical and Practical Aspects

ERIC Educational Resources Information Center

Matteucci, G.

2007-01-01

In the so-called electric Aharonov-Bohm effect, a quantum interference pattern shift is produced when electrons move in an electric field free region but, at the same time, in the presence of a time-dependent electric potential. Analogous fringe shifts are observed in interference experiments where electrons, travelling through an electrostatic…

Temperature and magnetic field effects on electron transport through DNA molecules in a two-dimensional four-channel system.

PubMed

Joe, Yong S; Lee, Sun H; Hedin, Eric R; Kim, Young D

2013-06-01

We utilize a two-dimensional four-channel DNA model, with a tight-binding (TB) Hamiltonian, and investigate the temperature and the magnetic field dependence of the transport behavior of a short DNA molecule. Random variation of the hopping integrals due to the thermal structural disorder, which partially destroy phase coherence of electrons and reduce quantum interference, leads to a reduction of the localization length and causes suppressed overall transmission. We also incorporate a variation of magnetic field flux density into the hopping integrals as a phase factor and observe Aharonov-Bohm (AB) oscillations in the transmission. It is shown that for non-zero magnetic flux, the transmission zero leaves the real-energy axis and moves up into the complex-energy plane. We also point out that the hydrogen bonds between the base pair with flux variations play a role to determine the periodicity of AB oscillations in the transmission.

Aharanov-Bohm quantum interference in a reconfigurable electron system

NASA Astrophysics Data System (ADS)

Irvin, P.; Lu, S.; Annadi, A.; Cheng, G.; Tomczyk, M.; Huang, M.; Levy, J.; Lee, J.-W.; Lee, H.; Eom, C.-B.

Aharanov-Bohm (AB) interference can arise in transport experiments when magnetic flux threads through two or more transport channels. The existence of this behavior requires long-range ballistic transport and is typically observed only in exceptionally clean materials. We observe AB interference in wide (w 100 nm) channels created at the LaAlO3/SrTiO3 interface using conductive AFM lithography. Interference occurs above a critical field B 4 T and increases in magnitude with increasing magnetic field. The period of oscillation implies a ballistic length that greatly exceeds the micron-scale length of the channel, consistent with Fabry-Perot interference in 1D channels. The conditions under which AB oscillations are observed will be discussed in the context of the electron pairing mechanism in LaAlO3/SrTiO3. We gratefully acknowledge financial support from AFOSR FA9550-12-1-0342 (CBE), NSF DMR-1234096 (CBE), and ONR N00014-15-1-2847 (JL).

Instability of quantum equilibrium in Bohm's dynamics

PubMed Central

Colin, Samuel; Valentini, Antony

2014-01-01

We consider Bohm's second-order dynamics for arbitrary initial conditions in phase space. In principle, Bohm's dynamics allows for ‘extended’ non-equilibrium, with initial momenta not equal to the gradient of phase of the wave function (as well as initial positions whose distribution departs from the Born rule). We show that extended non-equilibrium does not relax in general and is in fact unstable. This is in sharp contrast with de Broglie's first-order dynamics, for which non-standard momenta are not allowed and which shows an efficient relaxation to the Born rule for positions. On this basis, we argue that, while de Broglie's dynamics is a tenable physical theory, Bohm's dynamics is not. In a world governed by Bohm's dynamics, there would be no reason to expect to see an effective quantum theory today (even approximately), in contradiction with observation. PMID:25383020

The limits of the Bohm criterion in collisional plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valentini, H.-B.; Kaiser, D.

2015-05-15

The sheath formation within a low-pressure collisional plasma is analysed by means of a two-fluid model. The Bohm criterion takes into account the effects of the electric field and the inertia of the ions. Numerical results yield that these effects contribute to the space charge formation, only, if the collisionality is lower than a relatively small threshold. It follows that a lower and an upper limit of the drift speed of the ions exist where the effects treated by Bohm can form a sheath. This interval becomes narrower as the collisionality increases and vanishes at the mentioned threshold. Above themore » threshold, the sheath is mainly created by collisions and the ionisation. Under these conditions, the sheath formation cannot be described by means of Bohm like criteria. In a few references, a so-called upper limit of the Bohm criterion is stated for collisional plasmas where the momentum equation of the ions is taken into account, only. However, the present paper shows that this limit results in an unrealistically steep increase of the space charge density towards the wall, and, therefore, it yields no useful limit of the Bohm velocity.« less

Two Further Experiments on Electron Interference

ERIC Educational Resources Information Center

Matteucci, G.; Pozzi, G.

1978-01-01

Presents the results of two experiments concerning the phenomena of the interference of probabilities and of the so called Aharonov-Bohm effect. An electron biprism and a standard electron microscope have been used for the experiments. (Author/GA)

A note on the Sagnac effect for matter beams

NASA Astrophysics Data System (ADS)

Ruggiero, Matteo Luca; Tartaglia, Angelo

2015-05-01

We study the Sagnac effect for matter beams, in order to estimate the kinematic corrections to the basic formula, deriving from the position and the extent of the interferometer, and discuss the analogy with the Aharonov-Bohm effect. We show that the formula for the Sagnac time delay is the same for matter and light beams in arbitrary stationary space-times, provided that a suitable condition on the speed of the beams is fulfilled. Hence, the same results obtained for light beams apply to matter beams.

Bohm velocity in the presence of a hot cathode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palacio Mizrahi, J. H.; Krasik, Ya. E.

2013-08-15

The spatial distribution of the plasma and beam electrons in a region whose extension from a hot cathode is larger than the Debye length, but smaller than the electron mean free path, is analyzed. In addition, the influence of electrons thermionically emitted from a hot cathode and the ratio of electron-to-ion mass on the Bohm velocity and on the ion and electron densities at the plasma-sheath boundary in a gas discharge are studied. It is shown that thermionic emission has the effect of increasing the Bohm velocity, and this effect is more pronounced for lighter ions. In addition, it ismore » shown that the Bohm velocity cannot be increased to more than 24% above its value when there is no electron emission.« less

Spontaneous and persistent currents in superconductive and mesoscopic structures (Review)

NASA Astrophysics Data System (ADS)

Kulik, I. O.

2004-07-01

We briefly review aspects of superconductive persistent currents in Josephson junctions of the S/I/S, S/O/S and S/N/S types, focusing on the origin of jumps in the current versus phase dependences, and discuss in more detail the persistent and the "spontaneous" currents in Aharonov-Bohm mesoscopic and nanoscopic (macromolecular) structures. A fixed-number-of-electrons mesoscopic or macromolecular conducting ring is shown to be unstable against structural transformation removing spatial symmetry (in particular, azimuthal periodicity) of its electron-lattice Hamiltonian. In the case when the transformation is blocked by strong coupling to an external azimuthally symmetric environment, the system becomes bistable in its electronic configuration at a certain number of electrons. Under such a condition, the persistent current has a nonzero value even at an (almost) zero applied Aharonov-Bohm flux and results in very high magnetic susceptibility dM/dH at small nonzero fields, followed by an oscillatory dependence at larger fields. We tentatively assume that previously observed oscillatory magnetization in cyclic metallo-organic molecules by Gatteschi et al. can be attributed to persistent currents. If this proves correct, it may present an opportunity for (and, more generally, macromolecular cyclic structures may suggest the possibility of) engineering quantum computational tools based on the Aharonov-Bohm effect in ballistic nanostructures and macromolecular cyclic aggregates.

Nonrelativistic Conformed Symmetry in 2 + 1 Dimensional Field Theory.

NASA Astrophysics Data System (ADS)

Bergman, Oren

This thesis is devoted to the study of conformal invariance and its breaking in non-relativistic field theories. It is a well known feature of relativistic field theory that theories which are conformally invariant at the classical level can acquire a conformal anomaly upon quantization and renormalization. The anomaly appears through the introduction of an arbitrary, but dimensionful, renormalization scale. One does not usually associate the concepts of renormalization and anomaly with nonrelativistic quantum mechanics, but there are a few examples where these concepts are useful. The most well known case is the two-dimensional delta -function potential. In two dimensions the delta-function scales like the kinetic term of the Hamiltonian, and therefore the problem is classically conformally invariant. Another example of classical conformal invariance is the famous Aharonov-Bohm (AB) problem. In that case each partial wave sees a 1/r^2 potential. We use the second quantized formulation of these problems, namely the nonrelativistic field theories, to compute Green's functions and derive the conformal anomaly. In the case of the AB problem we also solve an old puzzle, namely how to reproduce the result of Aharonov and Bohm in perturbation theory. The thesis is organized in the following manner. Chapter 1 is an introduction to nonrelativistic field theory, nonrelativistic conformal invariance, contact interactions and the AB problem. In Chapter 2 we discuss nonrelativistic scalar field theory, and how its quantization produces the anomaly. Chapter 3 is devoted to the AB problem, and the resolution of the perturbation puzzle. In Chapter 4 we generalize the discussion of Chapter 3 to particles carrying nonabelian charges. The structure of the nonabelian theory is much richer, and deserves a separate discussion. We also comment on the issues of forward scattering and single -valuedness of wavefunctions, which are important for Chapter 3 as well. (Copies available

Magnetoresistance devices based on single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Hod, Oded; Rabani, Eran; Baer, Roi

2005-08-01

We demonstrate the physical principles for the construction of a nanometer-sized magnetoresistance device based on the Aharonov-Bohm effect [Phys. Rev. 115, 485 (1959)]. The proposed device is made of a short single-walled carbon nanotube (SWCNT) placed on a substrate and coupled to a tip/contacts. We consider conductance due to the motion of electrons along the circumference of the tube (as opposed to the motion parallel to its axis). We find that the circumference conductance is sensitive to magnetic fields threading the SWCNT due to the Aharonov-Bohm effect, and show that by retracting the tip/contacts, so that the coupling to the SWCNT is reduced, very high sensitivity to the threading magnetic field develops. This is due to the formation of a narrow resonance through which the tunneling current flows. Using a bias potential the resonance can be shifted to low magnetic fields, allowing the control of conductance with magnetic fields of the order of 1 T.

Aharonov-Casher effect and quantum transport in graphene based nano rings: A self-consistent Born approximation

NASA Astrophysics Data System (ADS)

Ghaderzadeh, A.; Rahbari, S. H. Ebrahimnazhad; Phirouznia, A.

2018-03-01

In this study, Rashba coupling induced Aharonov-Casher effect in a graphene based nano ring is investigated theoretically. The graphene based nano ring is considered as a central device connected to semi-infinite graphene nano ribbons. In the presence of the Rashba spin-orbit interaction, two armchair shaped edge nano ribbons are considered as semi-infinite leads. The non-equilibrium Green's function approach is utilized to obtain the quantum transport characteristics of the system. The relaxation and dephasing mechanisms within the self-consistent Born approximation is scrutinized. The Lopez-Sancho method is also applied to obtain the self-energy of the leads. We unveil that the non-equilibrium current of the system possesses measurable Aharonov-Casher oscillations with respect to the Rashba coupling strength. In addition, we have observed the same oscillations in dilute impurity regimes in which amplitude of the oscillations is shown to be suppressed as a result of the relaxations.

Magneto-optical quantum interferences in a system of spinor excitons

NASA Astrophysics Data System (ADS)

Kuan, Wen-Hsuan; Gudmundsson, Vidar

2018-04-01

In this work we investigate magneto-optical properties of two-dimensional semiconductor quantum-ring excitons with Rashba and Dresselhaus spin-orbit interactions threaded by a magnetic flux perpendicular to the plane of the ring. By calculating the excitonic Aharonov-Bohm spectrum, we study the Coulomb and spin-orbit effects on the Aharonov-Bohm features. From the light-matter interactions of the excitons, we find that for scalar excitons, there are open channels for spontaneous recombination resulting in a bright photoluminescence spectrum, whereas the forbidden recombination of dipolar excitons results in a dark photoluminescence spectrum. We investigate the generation of persistent charge and spin currents. The exploration of spin orientations manifests that by adjusting the strength of the spin-orbit interactions, the exciton can be constructed as a squeezed complex with specific spin polarization. Moreover, a coherently moving dipolar exciton acquires a nontrivial dual Aharonov-Casher phase, creating the possibility to generate persistent dipole currents and spin dipole currents. Our study reveals that in the presence of certain spin-orbit generated fields, the manipulation of the magnetic field provides a potential application for quantum-ring spinor excitons to be utilized in nano-scaled magneto-optical switches.

Tunable strength saddle-point contacts impact on quantum rings transmission

NASA Astrophysics Data System (ADS)

González, J. J.; Diago-Cisneros, L.

2016-09-01

A particular subject of investigation is the role of several sadle-point contact (QPC) parameters on the scattering properties of an Aharonov-Bohm-Aharonov-Casher quantum ring (QR) under Rashba-type spin orbit interaction. We discuss the interplay of the conductance with the confinement strengths and height of the QPC, which yields new and tunable harmonic and non-harmonics patterns, while one manipulates these constriction parameters. This phenomenology may be of utility to implement a novel way to modulate spin interference effects in semiconducting QRs, providing an appealing test-platform for spintronics applications.

Clarifying and Teaching Bohm-Bawerk's "Marginal Pairs."

ERIC Educational Resources Information Center

Egger, John B.

1998-01-01

Briefly defines and provides some background on Eugen von Bohm-Bawerk's "marginal pairs" theory of pricing. Asserts that Bohm-Bawerk's theory is a good introduction to the Austrian school of economics and illustrates the differences between this approach and neoclassical economic theory. Includes several graphs and tables of data. (MJP)

MAGNETIC FIELD LINE RANDOM WALK FOR DISTURBED FLUX SURFACES: TRAPPING EFFECTS AND MULTIPLE ROUTES TO BOHM DIFFUSION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghilea, M. C.; Ruffolo, D.; Sonsrettee, W.

2011-11-01

The magnetic field line random walk (FLRW) is important for the transport of energetic particles in many astrophysical situations. While all authors agree on the quasilinear diffusion of field lines for fluctuations that mainly vary parallel to a large-scale field, for the opposite case of fluctuations that mainly vary in the perpendicular directions, there has been an apparent conflict between concepts of Bohm diffusion and percolation/trapping effects. Here computer simulation and non-perturbative analytic techniques are used to re-examine the FLRW in magnetic turbulence with slab and two-dimensional (2D) components, in which 2D flux surfaces are disturbed by the slab fluctuations.more » Previous non-perturbative theories for D{sub perpendicular}, based on Corrsin's hypothesis, have identified a slab contribution with quasilinear behavior and a 2D contribution due to Bohm diffusion with diffusive decorrelation (DD), combined in a quadratic formula. Here we present analytic theories for other routes to Bohm diffusion, with random ballistic decorrelation (RBD) either due to the 2D component itself (for a weak slab contribution) or the total fluctuation field (for a strong slab contribution), combined in a direct sum with the slab contribution. Computer simulations confirm the applicability of RBD routes for weak or strong slab contributions, while the DD route applies for a moderate slab contribution. For a very low slab contribution, interesting trapping effects are found, including a depressed diffusion coefficient and subdiffusive behavior. Thus quasilinear, Bohm, and trapping behaviors are all found in the same system, together with an overall viewpoint to explain these behaviors.« less

Electromagnetic duality and the electric memory effect

NASA Astrophysics Data System (ADS)

Hamada, Yuta; Seo, Min-Seok; Shiu, Gary

2018-02-01

We study large gauge transformations for soft photons in quantum electrodynamics which, together with the helicity operator, form an ISO(2) algebra. We show that the two non-compact generators of the ISO(2) algebra correspond respectively to the residual gauge symmetry and its electromagnetic dual gauge symmetry that emerge at null infinity. The former is helicity universal (electric in nature) while the latter is helicity distinguishing (magnetic in nature). Thus, the conventional large gauge transformation is electric in nature, and is naturally associated with a scalar potential. We suggest that the electric Aharonov-Bohm effect is a direct measure for the electromagnetic memory arising from large gauge transformations.

Effects of Zeeman splitting on spin transportation in a three-terminal Rashba ring under a weak magnetic field

NASA Astrophysics Data System (ADS)

Zhai, Li-Xue; Wang, Yan; An, Zhong

2018-05-01

Spin-dependent transport in one-dimensional (1D) three-terminal Rashba rings is investigated under a weak magnetic field, and we focus on the Zeeman splitting (ZS) effect. For this purpose, the interaction between the electron spin and the weak magnetic field has been treated by perturbation theory. ZS removes the spin degeneracy, and breaks both the time reversal symmetry and the spin reversal symmetry of the ring system. Consequently, all conductance zeros are lifted and turned into conductance dips. Aharonov-Bohm (AB) oscillations can be found in both branch conductances and the total conductance as a function of the magnetic field. In a relatively high magnetic field, the decoherence caused by ZS decreases the amplitude of the branch conductance and increases that of the total conductance. The results have been compared with those reported in the published literature, and a reasonable agreement is obtained. The conductance as a function of the Rashba spin-orbit coupling (RSOC) strength has also been investigated. As the RSOC strength increases, the role of ZS becomes weaker and weaker; ZS can even be neglected when B ≤ 0.1 T.

Valley- and spin-polarized oscillatory magneto-optical absorption in monolayer MoS2 quantum rings

NASA Astrophysics Data System (ADS)

Oliveira, D.; Villegas-Lelovsky, L.; Soler, M. A. G.; Qu, Fanyao

2018-03-01

Besides optical valley selectivity, strong spin-orbit interaction along with Berry curvature effects also leads to unconventional valley- and spin-polarized Landau levels in monolayer transition metal dichalcogenides (TMDCs) under a perpendicular magnetic field. We find that these unique properties are inherited to the magneto-optical absorption spectrum of the TMDC quantum rings (QRs). In addition, it is robust against variation of the magnetic flux and of the QR geometry. In stark contrast to the monolayer bulk material, the MoS2 QRs manifest themselves in both the optical valley selectivity and unprecedented size tunability of the frequency of the light absorbed. We also find that when the magnetic field setup is changed, the phase transition from Aharonov-Bohm (AB) quantum interference to aperiodic oscillation of magneto-optical absorption spectrum takes place. The exciton spectrum in a realistic finite thickness MoS2 QR is also discussed.

Nonlinear Dirac cones

NASA Astrophysics Data System (ADS)

Bomantara, Raditya Weda; Zhao, Wenlei; Zhou, Longwen; Gong, Jiangbin

2017-09-01

Physics arising from two-dimensional (2D) Dirac cones has been a topic of great theoretical and experimental interest to studies of gapless topological phases and to simulations of relativistic systems. Such 2D Dirac cones are often characterized by a π Berry phase and are destroyed by a perturbative mass term. By considering mean-field nonlinearity in a minimal two-band Chern insulator model, we obtain a different type of Dirac cone that is robust to local perturbations without symmetry restrictions. Due to a different pseudospin texture, the Berry phase of the Dirac cone is no longer quantized in π , and can be continuously tuned as an order parameter. Furthermore, in an Aharonov-Bohm (AB) interference setup to detect such Dirac cones, the adiabatic AB phase is found to be π both theoretically and computationally, offering an observable topological invariant and a fascinating example where the Berry phase and AB phase are fundamentally different. We hence discover a nonlinearity-induced quantum phase transition from a known topological insulating phase to an unusual gapless topological phase.

Scanning gate microscopy of quantum rings: effects of an external magnetic field and of charged defects.

PubMed

Pala, M G; Baltazar, S; Martins, F; Hackens, B; Sellier, H; Ouisse, T; Bayot, V; Huant, S

2009-07-01

We study scanning gate microscopy (SGM) in open quantum rings obtained from buried semiconductor InGaAs/InAlAs heterostructures. By performing a theoretical analysis based on the Keldysh-Green function approach we interpret the radial fringes observed in experiments as the effect of randomly distributed charged defects. We associate SGM conductance images with the local density of states (LDOS) of the system. We show that such an association cannot be made with the current density distribution. By varying an external magnetic field we are able to reproduce recursive quasi-classical orbits in LDOS and conductance images, which bear the same periodicity as the Aharonov-Bohm effect.

Scanning Gate Microscopy on a Quantum Hall Interferometer

NASA Astrophysics Data System (ADS)

Martins, Frederico; Hackens, Benoit; Dutu, Augustin; Bayot, Vincent; Sellier, Hermann; Huant, Serge; Desplanque, Ludovic; Wallart, Xavier; Pala, Marco

2010-03-01

We perform scanning gate microscopy (SGM) experiments [1] at very low temperature (down to 100 mK) in the Quantum Hall regime on a mesoscopic quantum ring (QR) patterned in an InGaAs/InAlAs heterostructure. Close to integer filling factors ν=6, 8 and 10,the magnetoresistance of the QR is decorated with fast periodic oscillations, with a magnetic field period close to AB/ν, where AB is the Aharonov-Bohm period. We analyze the data in terms of electron tunneling between edge states trapped inside the QR and those transmitted through the QR openings [2]. SGM images reveal that the tip-induced perturbation of the electron confining potential gives rise to a rich pattern of narrow and wide concentric conductance fringes in the vicinity of the QR. [1] F. Martins et al. Phys. Rev. Lett. 99 136807 (2007); B. Hackens et al. Nat. Phys. 2 826 (2006). [2] B. Rosenow and B. I. Halperin, Phys. Rev. Lett. 98, 106801 (2007).

Unified Bohm criterion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kos, L.; Tskhakaya, D. D.; Jelić, N.

2015-09-15

Recent decades have seen research into the conditions necessary for the formation of the monotonic potential shape in the sheath, appearing at the plasma boundaries like walls, in fluid, and kinetic approximations separately. Although either of these approaches yields a formulation commonly known as the much-acclaimed Bohm criterion (BC), the respective results involve essentially different physical quantities that describe the ion gas behavior. In the fluid approach, such a quantity is clearly identified as the ion directional velocity. In the kinetic approach, the ion behavior is formulated via a quantity (the squared inverse velocity averaged by the ion distribution function)more » without any clear physical significance, which is, moreover, impractical. In the present paper, we try to explain this difference by deriving a condition called here the Unified Bohm Criterion, which combines an advanced fluid model with an upgraded explicit kinetic formula in a new form of the BC. By introducing a generalized polytropic coefficient function, the unified BC can be interpreted in a form that holds, irrespective of whether the ions are described kinetically or in the fluid approximation.« less

Critical role of electron heat flux on Bohm criterion

DOE PAGES

Tang, Xianzhu; Guo, Zehua

2016-12-05

Bohm criterion, originally derived for an isothermal-electron and cold-ion plasma, is often used as a rule of thumb for more general plasmas. Here, we establish a more precise determination of the Bohm criterion that are quantitatively useful for understanding and modeling collisional plasmas that still have collisional mean-free-path much greater than plasma Debye length. Specifically, it is shown that electron heat flux, rather than the isothermal electron assumption, is what sets the Bohm speed to bemore » $$\\sqrt{k_B(T_e||+3T_i||)/m_i}$$ with T e,i∥ the electron and ion parallel temperature at the sheath entrance and m i the ion mass.« less

Critical role of electron heat flux on Bohm criterion

NASA Astrophysics Data System (ADS)

Tang, Xian-Zhu; Guo, Zehua

2016-12-01

Bohm criterion, originally derived for an isothermal-electron and cold-ion plasma, is often used as a rule of thumb for more general plasmas. Here, we establish a more precise determination of the Bohm criterion that are quantitatively useful for understanding and modeling collisional plasmas that still have collisional mean-free-path much greater than plasma Debye length. Specifically, it is shown that electron heat flux, rather than the isothermal electron assumption, is what sets the Bohm speed to be √{ k B ( T e ∥ + 3 T i ∥ ) / m i } with T e , i ∥ the electron and ion parallel temperature at the sheath entrance and mi the ion mass.

Quasi-local action of curl-less vector potential on vortex dynamics in superconductors

NASA Astrophysics Data System (ADS)

Gulian, Armen M.; Nikoghosyan, Vahan R.; Gulian, Ellen D.; Melkonyan, Gurgen G.

2018-04-01

Studies of the Abrikosov vortex motion in superconductors based on time-dependent Ginzburg-Landau equations reveal an opportunity to detect the values of the Aharonov-Bohm type curl-less vector potentials without closed-loop electron trajectories encompassing the magnetic flux.

Quantum-ring spin interference device tuned by quantum point contacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diago-Cisneros, Leo; Mireles, Francisco

2013-11-21

We introduce a spin-interference device that comprises a quantum ring (QR) with three embedded quantum point contacts (QPCs) and study theoretically its spin transport properties in the presence of Rashba spin-orbit interaction. Two of the QPCs conform the lead-to-ring junctions while a third one is placed symmetrically in the upper arm of the QR. Using an appropriate scattering model for the QPCs and the S-matrix scattering approach, we analyze the role of the QPCs on the Aharonov-Bohm (AB) and Aharonov-Casher (AC) conductance oscillations of the QR-device. Exact formulas are obtained for the spin-resolved conductances of the QR-device as a functionmore » of the confinement of the QPCs and the AB/AC phases. Conditions for the appearance of resonances and anti-resonances in the spin-conductance are derived and discussed. We predict very distinctive variations of the QR-conductance oscillations not seen in previous QR proposals. In particular, we find that the interference pattern in the QR can be manipulated to a large extend by varying electrically the lead-to-ring topological parameters. The latter can be used to modulate the AB and AC phases by applying gate voltage only. We have shown also that the conductance oscillations exhibits a crossover to well-defined resonances as the lateral QPC confinement strength is increased, mapping the eigenenergies of the QR. In addition, unique features of the conductance arise by varying the aperture of the upper-arm QPC and the Rashba spin-orbit coupling. Our results may be of relevance for promising spin-orbitronics devices based on quantum interference mechanisms.« less

Bohm's Quantum Potential and the Visualization of Molecular Structure

NASA Technical Reports Server (NTRS)

Levit, Creon; Chancellor, Marisa K. (Technical Monitor)

1997-01-01

David Bohm's ontological interpretation of quantum theory can shed light on otherwise counter-intuitive quantum mechanical phenomena including chemical bonding. In the field of quantum chemistry, Richard Bader has shown that the topology of the Laplacian of the electronic charge density characterizes many features of molecular structure and reactivity. Visual and computational examination suggests that the Laplacian of Bader and the quantum potential of Bohm are morphologically equivalent. It appears that Bohmian mechanics and the quantum potential can make chemistry as clear as they makes physics.

On the upper bound in the Bohm sheath criterion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kotelnikov, I. A., E-mail: I.A.Kotelnikov@inp.nsk.su; Skovorodin, D. I., E-mail: D.I.Skovorodin@inp.nsk.su

2016-02-15

The question is discussed about the existence of an upper bound in the Bohm sheath criterion, according to which the Debye sheath at the interface between plasma and a negatively charged electrode is stable only if the ion flow velocity in plasma exceeds the ion sound velocity. It is stated that, with an exception of some artificial ionization models, the Bohm sheath criterion is satisfied as an equality at the lower bound and the ion flow velocity is equal to the speed of sound. In the one-dimensional theory, a supersonic flow appears in an unrealistic model of a localized ionmore » source the size of which is less than the Debye length; however, supersonic flows seem to be possible in the two- and three-dimensional cases. In the available numerical codes used to simulate charged particle sources with a plasma emitter, the presence of the upper bound in the Bohm sheath criterion is not supposed; however, the correspondence with experimental data is usually achieved if the ion flow velocity in plasma is close to the ion sound velocity.« less

Sheath formation in low-pressure discharges, the Bohm criterion and the consequences of collisions

NASA Astrophysics Data System (ADS)

Valentini, H.-B.; Kaiser, D.

2014-02-01

The space charge density in low-pressure discharges results from the generation of charged particles, the momentum transfer from these particles to the neutral gas and the electric field. A simplified model is used to treat this process analytically and numerically across the whole plasma. The effect of the electric field alone can cause the formation of the space charge sheath if the ion drift velocity υi to the wall exceeds the modified Bohm velocity υC = υB × (ni/ne)1/2, where υB is the Bohm velocity and ni and ne are the number densities of the ions and the electrons, respectively. However, a domain with υi ⩾ υC can occur only if the effect of collisions is weak. This domain is very narrow and does not come up to the wall. Limits of the electric field strength determining the sheath formation are given. It is shown that the electric field strength cannot be set equal to zero at υi = υB or υC under collisional conditions. The sheath extends from the region near the wall towards the centre and a result of that is to lower υi with respect to υB as the collisionality rises. These results are used to take into consideration various sheath criteria. The Bohm criterion takes into account the effect of the electric field only and reveals a well-defined sheath edge at υi = υB. This criterion remains a useful approximation of the sheath edge in almost collisionless plasmas as well. Under collisional conditions the definition of the sheath edge becomes more difficult and a little arbitrary. This paper takes into account new sheath criteria modified for the case of finite collisionality. The divergence between the densities of the ions and the electrons, the gradients of the space charge density and of the generalized Bohm speed υC are studied as functions of υi or the distance from the wall. These criteria are compared with the collisionally modified Bohm criteria proposed by Godyak (1982 Phys. Lett. A 89 80), Valentini (1996 Phys. Plasmas 3 1459), Chen

Imaging electron wave functions inside open quantum rings.

PubMed

Martins, F; Hackens, B; Pala, M G; Ouisse, T; Sellier, H; Wallart, X; Bollaert, S; Cappy, A; Chevrier, J; Bayot, V; Huant, S

2007-09-28

Combining scanning gate microscopy (SGM) experiments and simulations, we demonstrate low temperature imaging of the electron probability density |Psi|(2)(x,y) in embedded mesoscopic quantum rings. The tip-induced conductance modulations share the same temperature dependence as the Aharonov-Bohm effect, indicating that they originate from electron wave function interferences. Simulations of both |Psi|(2)(x,y) and SGM conductance maps reproduce the main experimental observations and link fringes in SGM images to |Psi|(2)(x,y).

Superpersistent currents and whispering gallery modes in relativistic quantum chaotic systems

PubMed Central

Xu, Hongya; Huang, Liang; Lai, Ying-Cheng; Grebogi, Celso

2015-01-01

Persistent currents (PCs), one of the most intriguing manifestations of the Aharonov-Bohm (AB) effect, are known to vanish for Schrödinger particles in the presence of random scatterings, e.g., due to classical chaos. But would this still be the case for Dirac fermions? Addressing this question is of significant value due to the tremendous recent interest in two-dimensional Dirac materials. We investigate relativistic quantum AB rings threaded by a magnetic flux and find that PCs are extremely robust. Even for highly asymmetric rings that host fully developed classical chaos, the amplitudes of PCs are of the same order of magnitude as those for integrable rings, henceforth the term superpersistent currents (SPCs). A striking finding is that the SPCs can be attributed to a robust type of relativistic quantum states, i.e., Dirac whispering gallery modes (WGMs) that carry large angular momenta and travel along the boundaries. We propose an experimental scheme using topological insulators to observe and characterize Dirac WGMs and SPCs, and speculate that these features can potentially be the base for a new class of relativistic qubit systems. Our discovery of WGMs in relativistic quantum systems is remarkable because, although WGMs are common in photonic systems, they are relatively rare in electronic systems. PMID:25758591

Superpersistent currents and whispering gallery modes in relativistic quantum chaotic systems.

PubMed

Xu, Hongya; Huang, Liang; Lai, Ying-Cheng; Grebogi, Celso

2015-03-11

Persistent currents (PCs), one of the most intriguing manifestations of the Aharonov-Bohm (AB) effect, are known to vanish for Schrödinger particles in the presence of random scatterings, e.g., due to classical chaos. But would this still be the case for Dirac fermions? Addressing this question is of significant value due to the tremendous recent interest in two-dimensional Dirac materials. We investigate relativistic quantum AB rings threaded by a magnetic flux and find that PCs are extremely robust. Even for highly asymmetric rings that host fully developed classical chaos, the amplitudes of PCs are of the same order of magnitude as those for integrable rings, henceforth the term superpersistent currents (SPCs). A striking finding is that the SPCs can be attributed to a robust type of relativistic quantum states, i.e., Dirac whispering gallery modes (WGMs) that carry large angular momenta and travel along the boundaries. We propose an experimental scheme using topological insulators to observe and characterize Dirac WGMs and SPCs, and speculate that these features can potentially be the base for a new class of relativistic qubit systems. Our discovery of WGMs in relativistic quantum systems is remarkable because, although WGMs are common in photonic systems, they are relatively rare in electronic systems.

FAST TRACK COMMUNICATION: The origin of Bohm diffusion, investigated by a comparison of different modelling methods

NASA Astrophysics Data System (ADS)

Bultinck, E.; Mahieu, S.; Depla, D.; Bogaerts, A.

2010-07-01

'Bohm diffusion' causes the electrons to diffuse perpendicularly to the magnetic field lines. However, its origin is not yet completely understood: low and high frequency electric field fluctuations are both named to cause Bohm diffusion. The importance of including this process in a Monte Carlo (MC) model is demonstrated by comparing calculated ionization rates with particle-in-cell/Monte Carlo collisions (PIC/MCC) simulations. A good agreement is found with a Bohm diffusion parameter of 0.05, which corresponds well to experiments. Since the PIC/MCC method accounts for fast electric field fluctuations, we conclude that Bohm diffusion is caused by fast electric field phenomena.

Determination of lateral size distribution of type-II ZnTe/ZnSe stacked submonolayer quantum dots via spectral analysis of optical signature of the Aharanov-Bohm excitons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ji, Haojie; Dhomkar, Siddharth; Roy, Bidisha

2014-10-28

For submonolayer quantum dot (QD) based photonic devices, size and density of QDs are critical parameters, the probing of which requires indirect methods. We report the determination of lateral size distribution of type-II ZnTe/ZnSe stacked submonolayer QDs, based on spectral analysis of the optical signature of Aharanov-Bohm (AB) excitons, complemented by photoluminescence studies, secondary-ion mass spectroscopy, and numerical calculations. Numerical calculations are employed to determine the AB transition magnetic field as a function of the type-II QD radius. The study of four samples grown with different tellurium fluxes shows that the lateral size of QDs increases by just 50%, evenmore » though tellurium concentration increases 25-fold. Detailed spectral analysis of the emission of the AB exciton shows that the QD radii take on only certain values due to vertical correlation and the stacked nature of the QDs.« less

Quantum phases for point-like charged particles and for electrically neutral dipoles in an electromagnetic field

NASA Astrophysics Data System (ADS)

Kholmetskii, A. L.; Missevitch, O. V.; Yarman, T.

2018-05-01

We point out that the known quantum phases for an electric/magnetic dipole moving in an electromagnetic (EM) field must be presented as the superposition of more fundamental quantum phases emerging for elementary charges. Using this idea, we find two new fundamental quantum phases for point-like charges, next to the known electric and magnetic Aharonov-Bohm (A-B) phases, named by us as the complementary electric and magnetic phases, correspondingly. We further demonstrate that these new phases can indeed be derived via the Schrödinger equation for a particle in an EM field, where however the operator of momentum is re-defined via the replacement of the canonical momentum of particle by the sum of its mechanical momentum and interactional field momentum for a system "charged particle and a macroscopic source of EM field". The implications of the obtained results are discussed.

The Fourth Law of Motion in Classical Mechanics and Electrodynamics

NASA Astrophysics Data System (ADS)

Pinheiro, Mario J.

2010-01-01

Newton's second law has limited scope of application when transient phenomena are at stake. We endeavor here to consider a modification of Newton's second law in order to take into account sudden change (surge) of angular momentum or linear momentum. It is shown that space react back according to a kind of induction law that is related to inertia, but also appears to give evidence of a "fluidic" nature of space itself. The back-reaction is quantified by the time rate of the angular momentum flux threading a surface, mass dependent, and bearing similarity to the quantum mechanics phase shift, present in the Aharonov-Bohm and Aharonov-Casher effects, thus giving evidence of the property of vacuum polarization, a phenomena which is relative to local space. It is formulated a kind of (qualitative) Lenz law that gives an explanation to precession.

Topological effects in quantum mechanics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peshkin, M.; Lipkin, H.J.

We completed our analysis of experiments, some completed, some planned, and some only conceptual at present, that purport to demonstrate new kinds of non-local and topological effects in the interaction of a neutron with an external electromagnetic field. In the Aharonov-Casher effect (AC), the neutron interacts with an electric field and in the Scalar Aharonov-Bohm effect (SAB) the neutron interacts with a magnetic field. In both cases, the geometry can be arranged so that there is no force on the neutron but an interference experiment nevertheless finds a phase shift proportional to the applied field and to the neutron`s magneticmore » moment. Previously, we showed that the accepted interpretation of these phenomena as topological effects due to a non-local interaction between the neutron and the electromagnetic field is incorrect. Both AC and SAB follow from local torques on the neutron whose expectation values vanish at every instant but which have non-vanishing effect on the measurable spin-correlation variables S(t) = (1/2) [{sigma}{sub x}{sigma}{sub x}(t) + {sigma}{sub y}(0){sigma}{sub y}(t) + h.c.] and V(t) = [{sigma}{sub x}(0){sigma}{sub y}(t) - {sigma}{sub y}(0){sigma}{sub x}(t) + h.c.]. We have now completed this work by observing that a criterion often used for identifying a topological effect, energy independence of the phase shift between two arms of an interferometer, is only a necessary condition, and by describing a phase shifter which obeys the energy-independence condition but whose interaction with the neutron is neither topological nor even non-local.« less

Topological vortices in gauge models of graphene

NASA Astrophysics Data System (ADS)

Zhang, Xin-Hui; Li, Xueqin; Hao, Jin-Bo

2018-06-01

Graphene-like structure possessing the topological vortices and knots, and the magnetic flux of the vortices configuration quantized, are proposed in this paper. The topological charges of the vortices are characterized by Hopf indices and Brower degrees. The Abelian background field action (BF action) is a topological invariant for the knot family, which is just the total sum of all the self-linking numbers and all the linking numbers. Flux quantization opens the possibility of having Aharonov-Bohm-type effects in graphene without external electromagnetic field.

Quantum phases for a charged particle and electric/magnetic dipole in an electromagnetic field

NASA Astrophysics Data System (ADS)

Kholmetskii, Alexander; Yarman, Tolga

2017-11-01

We point out that the known quantum phases for an electric/magnetic dipole moving in an electromagnetic field must be composed from more fundamental quantum phases emerging for moving elementary charges. Using this idea, we have found two new fundamental quantum phases, next to the known magnetic and electric Aharonov-Bohm phases, and discuss their general properties and physical meaning.

Helical quantum states in HgTe quantum dots with inverted band structures.

PubMed

Chang, Kai; Lou, Wen-Kai

2011-05-20

We investigate theoretically the electron states in HgTe quantum dots (QDs) with inverted band structures. In sharp contrast to conventional semiconductor quantum dots, the quantum states in the gap of the HgTe QD are fully spin-polarized and show ringlike density distributions near the boundary of the QD and spin-angular momentum locking. The persistent charge currents and magnetic moments, i.e., the Aharonov-Bohm effect, can be observed in such a QD structure. This feature offers us a practical way to detect these exotic ringlike edge states by using the SQUID technique.

Superstatistics of the Klein-Gordon equation in deformed formalism for modified Dirac delta distribution

NASA Astrophysics Data System (ADS)

Sargolzaeipor, S.; Hassanabadi, H.; Chung, W. S.

2018-04-01

The Klein-Gordon equation is extended in the presence of an Aharonov-Bohm magnetic field for the Cornell potential and the corresponding wave functions as well as the spectra are obtained. After introducing the superstatistics in the statistical mechanics, we first derived the effective Boltzmann factor in the deformed formalism with modified Dirac delta distribution. We then use the concepts of the superstatistics to calculate the thermodynamics properties of the system. The well-known results are recovered by the vanishing of deformation parameter and some graphs are plotted for the clarity of our results.

Analytically solvable model of an electronic Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Ngo Dinh, Stéphane; Bagrets, Dmitry A.; Mirlin, Alexander D.

2013-05-01

We consider a class of models of nonequilibrium electronic Mach-Zehnder interferometers built on integer quantum Hall edges states. The models are characterized by the electron-electron interaction being restricted to the inner part of the interferometer and transmission coefficients of the quantum quantum point contacts, defining the interferometer, which may take arbitrary values from zero to one. We establish an exact solution of these models in terms of single-particle quantities, determinants and resolvents of Fredholm integral operators. In the general situation, the results can be obtained numerically. In the case of strong charging interaction, the operators acquire the block Toeplitz form. Analyzing the corresponding Riemann-Hilbert problem, we reduce the result to certain singular single-channel determinants (which are a generalization of Toeplitz determinants with Fisher-Hartwig singularities) and obtain an analytic result for the interference current (and, in particular, for the visibility of Aharonov-Bohm oscillations). Our results, which are in good agreement with experimental observations, show an intimate connection between the observed “lobe” structure in the visibility of Aharonov-Bohm oscillations and multiple branches in the asymptotics of singular integral determinants.

Generalization of the Time-Energy Uncertainty Relation of Anandan-Aharonov Type

NASA Technical Reports Server (NTRS)

Hirayama, Minoru; Hamada, Takeshi; Chen, Jin

1996-01-01

A new type of time-energy uncertainty relation was proposed recently by Anandan and Aharonov. Their formula, to estimate the lower bound of time-integral of the energy-fluctuation in a quantum state is generalized to the one involving a set of quantum states. This is achieved by obtaining an explicit formula for the distance between two finitely separated points in the Grassman manifold.

Detailed numerical investigation of the Bohm limit in cosmic ray diffusion theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hussein, M.; Shalchi, A., E-mail: m_hussein@physics.umanitoba.ca, E-mail: andreasm4@yahoo.com

2014-04-10

A standard model in cosmic ray diffusion theory is the so-called Bohm limit in which the particle mean free path is assumed to be equal to the Larmor radius. This type of diffusion is often employed to model the propagation and acceleration of energetic particles. However, recent analytical and numerical work has shown that standard Bohm diffusion is not realistic. In the present paper, we perform test-particle simulations to explore particle diffusion in the strong turbulence limit in which the wave field is much stronger than the mean magnetic field. We show that there is indeed a lower limit ofmore » the particle mean free path along the mean field. In this limit, the mean free path is directly proportional to the unperturbed Larmor radius like in the traditional Bohm limit, but it is reduced by the factor δB/B {sub 0} where B {sub 0} is the mean field and δB the turbulent field. Although we focus on parallel diffusion, we also explore diffusion across the mean field in the strong turbulence limit.« less

Bohm criterion and plasma particle/power exhaust to and recycling at the wall

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Xianzhu; Guo, Zehua

The plasma particle and power exhaust to the divertor surface drives both particle and power recycling at the surface, which in return constrains the plasma density and temperature at the target and their profile further upstream. Both particle and power exhaust fluxes are mediated by the plasma sheath next to the divertor surface. In particular, the Bohm criterion constrains the ion exit flow speed, which enters directly into the particle flux and the kinetic flow energy component of the ion power flux, and indirectly into the electron power flux through the sheath potential drop. Here we give an overview onmore » how the Bohm speed is set in a general plasma and how it enters power exhaust and power recycling at the divertor surface, and the implication on the correct implementation of sheath boundary conditions in numerical codes. The cases of ideal and non-ideal Bohm speed are distinguished as a result of the physics discussion.« less

Bohm criterion and plasma particle/power exhaust to and recycling at the wall

DOE PAGES

Tang, Xianzhu; Guo, Zehua

2017-06-07

The plasma particle and power exhaust to the divertor surface drives both particle and power recycling at the surface, which in return constrains the plasma density and temperature at the target and their profile further upstream. Both particle and power exhaust fluxes are mediated by the plasma sheath next to the divertor surface. In particular, the Bohm criterion constrains the ion exit flow speed, which enters directly into the particle flux and the kinetic flow energy component of the ion power flux, and indirectly into the electron power flux through the sheath potential drop. Here we give an overview onmore » how the Bohm speed is set in a general plasma and how it enters power exhaust and power recycling at the divertor surface, and the implication on the correct implementation of sheath boundary conditions in numerical codes. The cases of ideal and non-ideal Bohm speed are distinguished as a result of the physics discussion.« less

Magnetic rings

NASA Astrophysics Data System (ADS)

Dolbeault, Jean; Esteban, Maria J.; Laptev, Ari; Loss, Michael

2018-05-01

We study functional and spectral properties of perturbations of the operator -(∂s+i a ) 2 in L2(S1 ) . This operator appears when considering the restriction to the unit circle of a two-dimensional Schrödinger operator with the Bohm-Aharonov vector potential. We prove a Hardy-type inequality on R2 and, on S1, a sharp interpolation inequality and a sharp Keller-Lieb-Thirring inequality.

Spin entanglement, decoherence and Bohm's EPR paradox.

PubMed

Cavalcanti, E G; Drummond, P D; Bachor, H A; Reid, M D

2009-10-12

We obtain criteria for entanglement and the EPR paradox for spin-entangled particles and analyse the effects of decoherence caused by absorption and state purity errors. For a two qubit photonic state, entanglement can occur for all transmission efficiencies. In this case, the state preparation purity must be above a threshold value. However, Bohm's spin EPR paradox can be achieved only above a critical level of loss. We calculate a required efficiency of 58%, which appears achievable with current quantum optical technologies. For a macroscopic number of particles prepared in a correlated state, spin entanglement and the EPR paradox can be demonstrated using our criteria for efficiencies eta > 1/3 and eta > 2/3 respectively. This indicates a surprising insensitivity to loss decoherence, in a macroscopic system of ultra-cold atoms or photons.

Colloidal CdSe Quantum Rings.

PubMed

Fedin, Igor; Talapin, Dmitri V

2016-08-10

Semiconductor quantum rings are of great fundamental interest because their non-trivial topology creates novel physical properties. At the same time, toroidal topology is difficult to achieve for colloidal nanocrystals and epitaxially grown semiconductor nanostructures. In this work, we introduce the synthesis of luminescent colloidal CdSe nanorings and nanostructures with double and triple toroidal topology. The nanorings form during controlled etching and rearrangement of two-dimensional nanoplatelets. We discuss a possible mechanism of the transformation of nanoplatelets into nanorings and potential utility of colloidal nanorings for magneto-optical (e.g., Aharonov-Bohm effect) and other applications.

Dirac oscillator interacting with a topological defect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carvalho, J.; Furtado, C.; Moraes, F.

In this work we study the interaction problem of a Dirac oscillator with gravitational fields produced by topological defects. The energy levels of the relativistic oscillator in the cosmic string and in the cosmic dislocation space-times are sensible to curvature and torsion associated to these defects and are important evidence of the influence of the topology on this system. In the presence of a localized magnetic field the energy levels acquire a term associated with the Aharonov-Bohm effect. We obtain the eigenfunctions and eigenvalues and see that in the nonrelativistic limit some results known in standard quantum mechanics are reached.

Chiral solitons in spinor polariton rings

NASA Astrophysics Data System (ADS)

Zezyulin, D. A.; Gulevich, D. R.; Skryabin, D. V.; Shelykh, I. A.

2018-04-01

We consider theoretically one-dimensional polariton ring accounting for both longitudinal-transverse (TE-TM) and Zeeman splittings of spinor polariton states and spin-dependent polariton-polariton interactions. We present a class of solutions in the form of the localized defects rotating with constant angular velocity and analyze their properties for realistic values of the parameters of the system. We show that the effects of the geometric phase arising from the interplay between the external magnetic field and the TE-TM splitting introduce chirality in the system and make solitons propagating in clockwise and anticlockwise directions nonequivalent. This can be interpreted as a solitonic analog of the Aharonov-Bohm effect.

Yakir Aharonov: From A to B

NASA Astrophysics Data System (ADS)

Pines, A.

Twenty years ago, I was accorded the privilege and pleasure of presenting the after banquet speech—reprinted below—at a conference celebrating the sixtieth year of my dear friend Yakir Aharonov. Does what I said then still hold today? You bet it does …the now adult Yakir has maintained the same burning curiosity, fiery enthusiasm and explosive genius for physics that characterized the life of the adolescent sixty year old. There may be no free lunch, but Yakir is living proof that there is free will, and he has exercised his free will to make ever more creative contributions to quantum physics, future and present. My admiration of Yakir as a scientist and mensch has only grown over the years. Sorry I can't be with you all at Chapman to participate in this marvelous eightieth year celebration. Dear Yakir, Ditsa and I wish you, Nilli and your family many more joyous years of health, science and friendship…' til 120.

PEOPLE IN PHYSICS: David Bohm and the implicate order: a new paradigm for physics teachers

NASA Astrophysics Data System (ADS)

Bettany, Laurence

1998-11-01

David Bohm (1917-93) was a highly original and individual physicist. His novel ideas and profound intuition extended not only to the physical world but also to the nature of consciousness and society. Bohm regarded science as having become essentially fragmented in its approach to understanding physical reality and sought a more holistic physics based on order, transformation and flowing movement. His notion of an implicate order provides an unusual and exciting challenge for both teachers and students alike.

Quantum Effects in Cosmology

NASA Astrophysics Data System (ADS)

Saharian, A. A.

2016-09-01

We investigate the vacuum expectation value of the current density for a charged scalar field on a slice of anti-de Sitter (AdS) space with toroidally compact dimensions. Along the compact dimensions periodicity conditions are imposed on the field operator with general phases and the presence of a constant gauge field is assumed. The latter gives rise to Aharonov-Bohm-like effects on the vacuum currents. The current density along compact dimensions is a periodic function of the gauge field flux with the period equal to the flux quantum. It vanishes on the AdS boundary and, near the horizon, to the leading order, it is conformally related to the corresponding quantity in Minkowski bulk for a massless field. For large values of the length of the compact dimension compared with the AdS curvature radius, the vacuum current decays as power-law for both massless and massive fields. This behavior is essentially different from the corresponding one in Minkowski background, where the currents for a massive field are suppressed exponentially.

Property attribution in Bohm's interpretation of quantum mechanics

NASA Astrophysics Data System (ADS)

Kraus, Katherine Bedard

1997-09-01

Bohmian ontology includes particles and a wavefield. I explore how these objects give rise to the world we experience, which properties these fundamental objects have, and what kind of property is spin. Also, I present an example of how our choices about property attribution affect our evaluation of the nonlocality in the system. According to the traditional presentation of Bohm's interpretation, a Bohmian world is 'classical' in the sense that pointer states, mental states, etc., are composed of or supervene on particle properties alone. However, I show that this approach does not make sense and argue that a Bohmian account of these states must include both particle properties and wavefield properties. I then clarify the role this plays in a systematic account of Bohmian probability. Also, my discussion shows that Vink's interpretation does not give us the world we experience. I then focus on particle and wavefield properties. I start by evaluating the recent arguments given by Brown et. al. that Bohmian particles do not bear properties such as gravitational mass, charge, etc. I reject their arguments but agree that (with the exception of inertial mass) we should not attribute these properties to Bohmian particles. I continue by examining the confusions underlying Cushing's (1995) proposal that a tunneling time measurement might be able to falsify Bohm's interpretation but neither verify or falsify the Copenhagen interpretation. The recognition that tunneling time is both a wavefield property and a particle property clarifies many of the issues. Next, I explain how Bohm's interpretation models spin measurements, the ways in which spin is contextual, and how Bohmian spin relates to the Kochen-Specker theorem. I also provide several reasons why we should not attribute spin vectors to Bohmian particles. Finally, I use the framework of the Bell Inequalities to discuss a system in which the properties we decide to attribute, and the time at which we evaluate the system

Chameleon Effect, the Range of Values Hypothesis and Reproducing the EPR-Bohm Correlations

NASA Astrophysics Data System (ADS)

Accardi, Luigi; Khrennikov, Andrei

2007-02-01

We present a detailed analysis of assumptions that J. Bell used to show that local realism contradicts QM. We find that Bell's viewpoint on realism is nonphysical, because it implicitly assume that observed physical variables coincides with ontic variables (i.e., these variables before measurement). The real physical process of measurement is a process of dynamical interaction between a system and a measurement device. Therefore one should check the adequacy of QM not to "Bell's realism," but to adaptive realism (chameleon realism). Dropping Bell's assumption we are able to construct a natural representation of the EPR-Bohm correlations in the local (adaptive) realistic approach.

Aharonov–Anandan quantum phases and Landau quantization associated with a magnetic quadrupole moment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fonseca, I.C.; Bakke, K., E-mail: kbakke@fisica.ufpb.br

The arising of geometric quantum phases in the wave function of a moving particle possessing a magnetic quadrupole moment is investigated. It is shown that an Aharonov–Anandan quantum phase (Aharonov and Anandan, 1987) can be obtained in the quantum dynamics of a moving particle with a magnetic quadrupole moment. In particular, it is obtained as an analogue of the scalar Aharonov–Bohm effect for a neutral particle (Anandan, 1989). Besides, by confining the quantum particle to a hard-wall confining potential, the dependence of the energy levels on the geometric quantum phase is discussed and, as a consequence, persistent currents can arisemore » from this dependence. Finally, an analogue of the Landau quantization is discussed. -- Highlights: •Scalar Aharonov–Bohm effect for a particle possessing a magnetic quadrupole moment. •Aharonov–Anandan quantum phase for a particle with a magnetic quadrupole moment. •Dependence of the energy levels on the Aharonov–Anandan quantum phase. •Landau quantization associated with a particle possessing a magnetic quadrupole moment.« less

On the spin- 1/2 Aharonov–Bohm problem in conical space: Bound states, scattering and helicity nonconservation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrade, F.M., E-mail: fmandrade@uepg.br; Silva, E.O., E-mail: edilbertoo@gmail.com; Pereira, M., E-mail: marciano@uepg.br

2013-12-15

In this work the bound state and scattering problems for a spin- 1/2 particle undergone to an Aharonov–Bohm potential in a conical space in the nonrelativistic limit are considered. The presence of a δ-function singularity, which comes from the Zeeman spin interaction with the magnetic flux tube, is addressed by the self-adjoint extension method. One of the advantages of the present approach is the determination of the self-adjoint extension parameter in terms of physics of the problem. Expressions for the energy bound states, phase-shift and S matrix are determined in terms of the self-adjoint extension parameter, which is explicitly determinedmore » in terms of the parameters of the problem. The relation between the bound state and zero modes and the failure of helicity conservation in the scattering problem and its relation with the gyromagnetic ratio g are discussed. Also, as an application, we consider the spin- 1/2 Aharonov–Bohm problem in conical space plus a two-dimensional isotropic harmonic oscillator. -- Highlights: •Planar dynamics of a spin- 1/2 neutral particle. •Bound state for Aharonov–Bohm systems. •Aharonov–Bohm scattering. •Helicity nonconservation. •Determination of the self-adjoint extension parameter.« less

Modeling of the Magnetization Behavior of Realistic Self-Organized InAs/GaAs Quantum Craters as Observed with Cross-Sectional STM

NASA Astrophysics Data System (ADS)

Fomin, V. M.; Gladilin, V. N.; Devreese, J. T.; Offermans, P.; Koenraad, P. M.; Wolter, J. H.; García, J. M.; Granados, D.

2005-06-01

Recently, using cross-sectional scanning-tunneling microscopy (X-STM), it was shown that self-organized ring-like InAs quantum dots are much smaller in diameter than it is expected from atomic force microscopy measurements and, moreover, that they possess a depression rather than an opening in the central region. For those quantum craters, we analyze the possibility to reveal the electronic properties (like the Aharonov-Bohm oscillations) peculiar to doubly connected geometry of quantum rings.

Bohm-criterion approximation versus optimal matched solution for a cylindrical probe in radial-motion theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Din, Alif

2016-08-15

The theory of positive-ion collection by a probe immersed in a low-pressure plasma was reviewed and extended by Allen et al. [Proc. Phys. Soc. 70, 297 (1957)]. The numerical computations for cylindrical and spherical probes in a sheath region were presented by F. F. Chen [J. Nucl. Energy C 7, 41 (1965)]. Here, in this paper, the sheath and presheath solutions for a cylindrical probe are matched through a numerical matching procedure to yield “matched” potential profile or “M solution.” The solution based on the Bohm criterion approach “B solution” is discussed for this particular problem. The comparison of cylindricalmore » probe characteristics obtained from the correct potential profile (M solution) and the approximated Bohm-criterion approach are different. This raises questions about the correctness of cylindrical probe theories relying only on the Bohm-criterion approach. Also the comparison between theoretical and experimental ion current characteristics shows that in an argon plasma the ions motion towards the probe is almost radial.« less

Electromagnetic potential vectors and the Lagrangian of a charged particle

NASA Technical Reports Server (NTRS)

Shebalin, John V.

1992-01-01

Maxwell's equations can be shown to imply the existence of two independent three-dimensional potential vectors. A comparison between the potential vectors and the electric and magnetic field vectors, using a spatial Fourier transformation, reveals six independent potential components but only four independent electromagnetic field components for each mode. Although the electromagnetic fields determined by Maxwell's equations give a complete description of all possible classical electromagnetic phenomena, potential vectors contains more information and allow for a description of such quantum mechanical phenomena as the Aharonov-Bohm effect. A new result is that a charged particle Lagrangian written in terms of potential vectors automatically contains a 'spontaneous symmetry breaking' potential.

Magneto-optical studies of quantum dots

NASA Astrophysics Data System (ADS)

Russ, Andreas Hans

Significant effort in condensed matter physics has recently been devoted to the field of "spintronics" which seeks to utilize the spin degree of freedom of electrons. Unlike conventional electronics that rely on the electron charge, devices exploiting their spin have the potential to yield new and novel technological applications, including spin transistors, spin filters, and spin-based memory devices. Any such application has the following essential requirements: 1) Efficient electrical injection of spin-polarized carriers; 2) Long spin lifetimes; 3) Ability to control and manipulate electron spins; 4) Effective detection of spin-polarized carriers. Recent work has demonstrated efficient electrical injection from ferromagnetic contacts such as Fe and MnAs, utilizing a spin-Light Emitting Diode (spin-LED) as a method of detection. Semiconductor quantum dots (QDs) are attractive candidates for satisfying requirements 2 and 3 as their zero dimensionality significantly suppresses many spin-flip mechanisms leading to long spin coherence times, as well as enabling the localization and manipulation of a controlled number of electrons and holes. This thesis is composed of three projects that are all based on the optical properties of QD structures including: I) Intershell exchange between spin-polarized electrons occupying adjacent shells in InAs QDs; II) Spin-polarized multiexitons in InAs QDs in the presence of spin-orbit interactions; III) The optical Aharonov-Bohm effect in AlxGa1-xAs/AlyGa1-yAs quantum wells (QWs). In the following we introduce some of the basic optical properties of quantum dots, describe the main tool (spin-LED) employed in this thesis to inject and detect spins in these QDs, and conclude with the optical Aharonov-Bohm effect (OAB) in type-II QDs.

Shrunk loop theorem for the topology probabilities of closed Brownian (or Feynman) paths on the twice punctured plane

NASA Astrophysics Data System (ADS)

Giraud, O.; Thain, A.; Hannay, J. H.

2004-02-01

The shrunk loop theorem proved here is an integral identity which facilitates the calculation of the relative probability (or probability amplitude) of any given topology that a free, closed Brownian (or Feynman) path of a given 'duration' might have on the twice punctured plane (plane with two marked points). The result is expressed as a 'scattering' series of integrals of increasing dimensionality based on the maximally shrunk version of the path. Physically, this applies in different contexts: (i) the topology probability of a closed ideal polymer chain on a plane with two impassable points, (ii) the trace of the Schrödinger Green function, and thence spectral information, in the presence of two Aharonov-Bohm fluxes and (iii) the same with two branch points of a Riemann surface instead of fluxes. Our theorem starts from the Stovicek scattering expansion for the Green function in the presence of two Aharonov-Bohm flux lines, which itself is based on the famous Sommerfeld one puncture point solution of 1896 (the one puncture case has much easier topology, just one winding number). Stovicek's expansion itself can supply the results at the expense of choosing a base point on the loop and then integrating it away. The shrunk loop theorem eliminates this extra two-dimensional integration, distilling the topology from the geometry.

The missing history of Bohm's hidden variables theory: The Ninth Symposium of the Colston Research Society, Bristol, 1957

NASA Astrophysics Data System (ADS)

Kožnjak, Boris

2018-05-01

In this paper, I analyze the historical context, scientific and philosophical content, and the implications of the thus far historically largely neglected Ninth Symposium of the Colston Research Society held in Bristol at the beginning of April 1957, the first major international event after World War II gathering eminent physicists and philosophers to discuss the foundational questions of quantum mechanics, in respect to the early reception of the causal quantum theory program mapped and defended by David Bohm during the five years preceding the Symposium. As will be demonstrated, contrary to the almost unanimously negative and even hostile reception of Bohm's ideas on hidden variables in the early 1950s, in the close aftermath of the 1957 Colston Research Symposium Bohm's ideas received a more open-minded and ideologically relaxed critical rehabilitation, in which the Symposium itself played a vital and essential part.

Measurement of Quantum Phase-Slips in Josephson Junction Chains

NASA Astrophysics Data System (ADS)

Guichard, Wiebke

2011-03-01

Quantum phase-slip dynamics in Josephson junction chains could provide the basis for the realization of a new type of topologically protected qubit or for the implementation of a new current standard. I will present measurements of the effect of quantum phase-slips on the ground state of a Josephson junction chain. We can tune in situ the strength of the phase-slips. These phase-slips are the result of fluctuations induced by the finite charging energy of each junction in the chain. Our measurements demonstrate that a Josephson junction chain under phase bias constraint behaves in a collective way. I will also show evidence of coherent phase-slip interference, the so called Aharonov-Casher effect. This phenomenon is the dual of the well known Aharonov-Bohm interference. In collaboration with I.M. Pop, Institut Neel, C.N.R.S. and Universite Joseph Fourier, BP 166, 38042 Grenoble, France; I. Protopopov, L. D. Landau Institute for Theoretical Physics, Kosygin str. 2, Moscow 119334, Russia and Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie, 76021 Karlsruhe, Germany; and F. Lecocq, Z. Peng, B. Pannetier, O. Buisson, Institut Neel, C.N.R.S. and Universite Joseph Fourier. European STREP MIDAS, ANR QUANTJO.

Topological insulator nanowires and nanowire hetero-junctions

NASA Astrophysics Data System (ADS)

Deng, Haiming; Zhao, Lukas; Wade, Travis; Konczykowski, Marcin; Krusin-Elbaum, Lia

2014-03-01

The existing topological insulator materials (TIs) continue to present a number of challenges to complete understanding of the physics of topological spin-helical Dirac surface conduction channels, owing to a relatively large charge conduction in the bulk. One way to reduce the bulk contribution and to increase surface-to-volume ratio is by nanostructuring. Here we report on the synthesis and characterization of Sb2Te3, Bi2Te3 nanowires and nanotubes and Sb2Te3/Bi2Te3 heterojunctions electrochemically grown in porous anodic aluminum oxide (AAO) membranes with varied (from 50 to 150 nm) pore diameters. Stoichiometric rigid polycrystalline nanowires with controllable cross-sections were obtained using cell voltages in the 30 - 150 mV range. Transport measurements in up to 14 T magnetic fields applied along the nanowires show Aharonov-Bohm (A-B) quantum oscillations with periods corresponding to the nanowire diameters. All nanowires were found to exhibit sharp weak anti-localization (WAL) cusps, a characteristic signature of TIs. In addition to A-B oscillations, new quantization plateaus in magnetoresistance (MR) at low fields (< 0 . 7T) were observed. The analysis of MR as well as I - V characteristics of heterojunctions will be presented. Supported in part by NSF-DMR-1122594, NSF-DMR-1312483-MWN, and DOD-W911NF-13-1-0159.

Limits on amplification by Aharonov-Albert-Vaidman weak measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koike, Tatsuhiko; Tanaka, Saki

2011-12-15

We analyze the amplification by the Aharonov-Albert-Vaidman weak quantum measurement on a Sagnac interferometer [Dixon et al., Phys. Rev. Lett. 102, 173601 (2009)] up to all orders of the coupling strength between the measured system and the measuring device. The amplifier transforms a small tilt of a mirror into a large transverse displacement of the laser beam. The conventional analysis has shown that the measured value is proportional to the weak value, so that the amplification can be made arbitrarily large in the cost of decreasing output laser intensity. It is shown that the measured displacement and the amplification factormore » are in fact not proportional to the weak value and rather vanish in the limit of infinitesimal output intensity. We derive the optimal overlap of the pre- and postselected states with which the amplification become maximum. We also show that the nonlinear effects begin to arise in the performed experiments so that any improvements in the experiment, typically with an amplification greater than 100, should require the nonlinear theory in translating the observed value to the original displacement.« less

Harvard-Lead Phase of Multi- Qubit Systems Based on Electron Spins in Coupled Quantum Dots Project Meeting

DTIC Science & Technology

2014-03-24

8.00 9.00 T. Hatano, T. Kubo , Y. Tokura, S. Amaha, S. Teraoka, S. Tarucha. Aharonov-Bohm Oscillations Changed by Indirect Interdot Tunneling via...M. Pioro-Ladrière, T. Kubo , K. Yoshida, T. Taniyama, Y. Tokura, S. Tarucha. Two-Qubit Gate of Combined Single-Spin Rotation and Interdot Spin...1 2012): 0. doi: 10.1103/PhysRevB.85.035306 S. Amaha, T. Hatano, H. Tamura, S. Teraoka, T. Kubo , Y. Tokura, D. G. Austing, S. Tarucha. Resonance

Mesoscopic Field-Effect-Induced Devices in Depleted Two-Dimensional Electron Systems

NASA Astrophysics Data System (ADS)

Bachsoliani, N.; Platonov, S.; Wieck, A. D.; Ludwig, S.

2017-12-01

Nanoelectronic devices embedded in the two-dimensional electron system (2DES) of a GaAs /(Al ,Ga )As heterostructure enable a large variety of applications ranging from fundamental research to high-speed transistors. Electrical circuits are thereby commonly defined by creating barriers for carriers by the selective depletion of a preexisting 2DES. We explore an alternative approach: we deplete the 2DES globally by applying a negative voltage to a global top gate and screen the electric field of the top gate only locally using nanoscale gates placed on the wafer surface between the plane of the 2DES and the top gate. Free carriers are located beneath the screen gates, and their properties can be controlled by means of geometry and applied voltages. This method promises considerable advantages for the definition of complex circuits by the electric-field effect, as it allows us to reduce the number of gates and simplify gate geometries. Examples are carrier systems with ring topology or large arrays of quantum dots. We present a first exploration of this method pursuing field effect, Hall effect, and Aharonov-Bohm measurements to study electrostatic, dynamic, and coherent properties.

The energy-time uncertainty principle and the EPR paradox: Experiments involving correlated two-photon emission in parametric down-conversion

NASA Technical Reports Server (NTRS)

Chiao, Raymond Y.; Kwiat, Paul G.; Steinberg, Aephraim M.

1992-01-01

The energy-time uncertainty principle is on a different footing than the momentum position uncertainty principle: in contrast to position, time is a c-number parameter, and not an operator. As Aharonov and Bohm have pointed out, this leads to different interpretations of the two uncertainty principles. In particular, one must distinguish between an inner and an outer time in the definition of the spread in time, delta t. It is the inner time which enters the energy-time uncertainty principle. We have checked this by means of a correlated two-photon light source in which the individual energies of the two photons are broad in spectra, but in which their sum is sharp. In other words, the pair of photons is in an entangled state of energy. By passing one member of the photon pair through a filter with width delta E, it is observed that the other member's wave packet collapses upon coincidence detection to a duration delta t, such that delta E(delta t) is approximately equal to planks constant/2 pi, where this duration delta t is an inner time, in the sense of Aharonov and Bohm. We have measured delta t by means of a Michelson interferometer by monitoring the visibility of the fringes seen in coincidence detection. This is a nonlocal effect, in the sense that the two photons are far away from each other when the collapse occurs. We have excluded classical-wave explanations of this effect by means of triple coincidence measurements in conjunction with a beam splitter which follows the Michelson interferometer. Since Bell's inequalities are known to be violated, we believe that it is also incorrect to interpret this experimental outcome as if energy were a local hidden variable, i.e., as if each photon, viewed as a particle, possessed some definite but unknown energy before its detection.

Field theory of pattern identification

NASA Astrophysics Data System (ADS)

Agu, Masahiro

1988-06-01

Based on the psychological experimental fact that images in mental space are transformed into other images for pattern identification, a field theory of pattern identification of geometrical patterns is developed with the use of gauge field theory in Euclidean space. Here, the ``image'' or state function ψ[χ] of the brain reacting to a geometrical pattern χ is made to correspond to the electron's wave function in Minkowski space. The pattern identification of the pattern χ with the modified pattern χ+Δχ is assumed to be such that their images ψ[χ] and ψ[χ+Δχ] in the brain are transformable with each other through suitable transformation groups such as parallel transformation, dilatation, or rotation. The transformation group is called the ``image potential'' which corresponds to the vector potential of the gauge field. An ``image field'' derived from the image potential is found to be induced in the brain when the two images ψ[χ] and ψ[χ+Δχ] are not transformable through suitable transformation groups or gauge transformations. It is also shown that, when the image field exists, the final state of the image ψ[χ] is expected to be different, depending on the paths of modifications of the pattern χ leading to a final pattern. The above fact is interpreted as a version of the Aharonov and Bohm effect of the electron's wave function [A. Aharonov and D. Bohm, Phys. Rev. 115, 485 (1959)]. An excitation equation of the image field is also derived by postulating that patterns are identified maximally for the purpose of minimizing the number of memorized standard patterns.

Extraordinary SEAWs under influence of the spin-spin interaction and the quantum Bohm potential

NASA Astrophysics Data System (ADS)

Andreev, Pavel A.

2018-06-01

The separate spin evolution (SSE) of electrons causes the existence of the spin-electron acoustic wave. Extraordinary spin-electron acoustic waves (SEAWs) propagating perpendicular to the external magnetic field have a large contribution of the transverse electric field. Its spectrum has been studied in the quasi-classical limit at the consideration of the separate spin evolution. The spin-spin interaction and the quantum Bohm potential give contribution in the spectrum extraordinary SEAWs. This contribution is studied in this paper. Moreover, it is demonstrated that the spin-spin interaction leads to the existence of the extraordinary SEAWs if the SSE is neglected. It has been found that the SSE causes the instability of the extraordinary SEAW at the large wavelengths, but the quantum Bohm potential leads to the full stabilization of the spectrum.

Decoherence of high-energy electrons in weakly disordered quantum Hall edge states

NASA Astrophysics Data System (ADS)

Nigg, Simon E.; Lunde, Anders Mathias

2016-07-01

We investigate theoretically the phase coherence of electron transport in edge states of the integer quantum Hall effect at filling factor ν =2 , in the presence of disorder and inter edge state Coulomb interaction. Within a Fokker-Planck approach, we calculate analytically the visibility of the Aharonov-Bohm oscillations of the current through an electronic Mach-Zehnder interferometer. In agreement with recent experiments, we find that the visibility is independent of the energy of the current-carrying electrons injected high above the Fermi sea. Instead, it is the amount of disorder at the edge that sets the phase space available for inter edge state energy exchange and thereby controls the visibility suppression.

Comment on ‘Information hidden in the velocity distribution of ions and the exact kinetic Bohm criterion’

NASA Astrophysics Data System (ADS)

Mustafaev, A. S.; Sukhomlinov, V. S.; Timofeev, N. A.

2018-03-01

This Comment is devoted to some mathematical inaccuracies made by the authors of the paper ‘Information hidden in the velocity distribution of ions and the exact kinetic Bohm criterion’ (Plasma Sources Science and Technology 26 055003). In the Comment, we show that the diapason of plasma parameters for the validity of the theoretical results obtained by the authors was defined incorrectly; we made a more accurate definition of this diapason. As a result, we show that it is impossible to confirm or refute the feasibility of the Bohm kinetic criterion on the basis of the data of the cited paper.

Oscillatory persistent currents in self-assembled quantum rings.

PubMed

Kleemans, N A J M; Bominaar-Silkens, I M A; Fomin, V M; Gladilin, V N; Granados, D; Taboada, A G; García, J M; Offermans, P; Zeitler, U; Christianen, P C M; Maan, J C; Devreese, J T; Koenraad, P M

2007-10-05

We report the direct measurement of the persistent current carried by a single electron by means of magnetization experiments on self-assembled InAs/GaAs quantum rings. We measured the first Aharonov-Bohm oscillation at a field of 14 T, in perfect agreement with our model based on the structural properties determined by cross-sectional scanning tunneling microscopy measurements. The observed oscillation magnitude of the magnetic moment per electron is remarkably large for the topology of our nanostructures, which are singly connected and exhibit a pronounced shape asymmetry.

Topological Proximity Effect: A Gauge Influence from Distant Fields on Planar Quantum-Coherent Systems

NASA Astrophysics Data System (ADS)

Moulopoulos, K.

2015-06-01

A quantum system that lies nearby a magnetic or time-varying electric field region, and that is under periodic boundary conditions parallel to the interface, is shown to exhibit a "hidden" Aharonov-Bohm effect (magnetic or electric), caused by fluxes that are not enclosed by, but are merely neighboring to our system - its origin being the absence of magnetic monopoles in 3D space (with corresponding spacetime generalizations). Novel possibilities then arise, where a field-free system can be dramatically affected by manipulating fields in an adjacent or even distant land, provided that these nearby fluxes are not quantized (i.e. they are fractional or irrational parts of the flux quantum). Topological effects (such as Quantum Hall types of behaviors) can therefore be induced from outside our system (that is always field-free and can even reside in simply-connected space). Potential novel applications are outlined, and exotic consequences in solid state physics are pointed out (i.e. the possibility of field-free quantum periodic systems that violate Bloch's theorem), while formal analogies with certain high energy physics phenomena and with some rather under-explored areas in mechanics and thermodynamics are noted.

Controllable continuous evolution of electronic states in a single quantum ring

NASA Astrophysics Data System (ADS)

Chakraborty, Tapash; Manaselyan, Aram; Barseghyan, Manuk; Laroze, David

2018-02-01

An intense terahertz laser field is shown to have a profound effect on the electronic and optical properties of quantum rings where the isotropic and anisotropic quantum rings can now be treated on equal footing. We have demonstrated that in isotropic quantum rings the laser field creates unusual Aharonov-Bohm oscillations that are usually expected in anisotropic rings. Furthermore, we have shown that intense laser fields can restore the isotropic physical properties in anisotropic quantum rings. In principle, all types of anisotropies (structural, effective masses, defects, etc.) can evolve as in isotropic rings in our present approach. Most importantly, we have found a continuous evolution of the energy spectra and intraband optical characteristics of structurally anisotropic quantum rings to those of isotropic rings in a controlled manner with the help of a laser field.

Flat bands in lattices with non-Hermitian coupling

NASA Astrophysics Data System (ADS)

Leykam, Daniel; Flach, Sergej; Chong, Y. D.

2017-08-01

We study non-Hermitian photonic lattices that exhibit competition between conservative and non-Hermitian (gain/loss) couplings. A bipartite sublattice symmetry enforces the existence of non-Hermitian flat bands, which are typically embedded in an auxiliary dispersive band and give rise to nondiffracting "compact localized states". Band crossings take the form of non-Hermitian degeneracies known as exceptional points. Excitations of the lattice can produce either diffracting or amplifying behaviors. If the non-Hermitian coupling is fine-tuned to generate an effective π flux, the lattice spectrum becomes completely flat, a non-Hermitian analog of Aharonov-Bohm caging in which the magnetic field is replaced by balanced gain and loss. When the effective flux is zero, the non-Hermitian band crossing points give rise to asymmetric diffraction and anomalous linear amplification.

Observation of FeGe skyrmions by electron phase microscopy with hole-free phase plate

NASA Astrophysics Data System (ADS)

Kotani, Atsuhiro; Harada, Ken; Malac, Marek; Salomons, Mark; Hayashida, Misa; Mori, Shigeo

2018-05-01

We report application of hole-free phase plate (HFPP) to imaging of magnetic skyrmion lattices. Using HFPP imaging, we observed skyrmions in FeGe, and succeeded in obtaining phase contrast images that reflect the sample magnetization distribution. According to the Aharonov-Bohm effect, the electron phase is shifted by the magnetic flux due to sample magnetization. The differential processing of the intensity in a HFPP image allows us to successfully reconstruct the magnetization map of the skyrmion lattice. Furthermore, the calculated phase shift due to the magnetization of the thin film was consistent with that measured by electron holography experiment, which demonstrates that HFPP imaging can be utilized for analysis of magnetic fields and electrostatic potential distribution at the nanoscale.

Adiabatic Edge Channel Transport in a Nanowire Quantum Point Contact Register.

PubMed

Heedt, S; Manolescu, A; Nemnes, G A; Prost, W; Schubert, J; Grützmacher, D; Schäpers, Th

2016-07-13

We report on a prototype device geometry where a number of quantum point contacts are connected in series in a single quasi-ballistic InAs nanowire. At finite magnetic field the backscattering length is increased up to the micron-scale and the quantum point contacts are connected adiabatically. Hence, several input gates can control the outcome of a ballistic logic operation. The absence of backscattering is explained in terms of selective population of spatially separated edge channels. Evidence is provided by regular Aharonov-Bohm-type conductance oscillations in transverse magnetic fields, in agreement with magnetoconductance calculations. The observation of the Shubnikov-de Haas effect at large magnetic fields corroborates the existence of spatially separated edge channels and provides a new means for nanowire characterization.

Statically screened ion potential and Bohm potential in a quantum plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moldabekov, Zhandos; Institute for Experimental and Theoretical Physics, Al-Farabi Kazakh National University, 71 Al-Farabi Str., 050040 Almaty; Schoof, Tim

2015-10-15

The effective potential Φ of a classical ion in a weakly correlated quantum plasma in thermodynamic equilibrium at finite temperature is well described by the random phase approximation screened Coulomb potential. Additionally, collision effects can be included via a relaxation time ansatz (Mermin dielectric function). These potentials are used to study the quality of various statically screened potentials that were recently proposed by Shukla and Eliasson (SE) [Phys. Rev. Lett. 108, 165007 (2012)], Akbari-Moghanjoughi (AM) [Phys. Plasmas 22, 022103 (2015)], and Stanton and Murillo (SM) [Phys. Rev. E 91, 033104 (2015)] starting from quantum hydrodynamic (QHD) theory. Our analysis revealsmore » that the SE potential is qualitatively different from the full potential, whereas the SM potential (at any temperature) and the AM potential (at zero temperature) are significantly more accurate. This confirms the correctness of the recently derived [Michta et al., Contrib. Plasma Phys. 55, 437 (2015)] pre-factor 1/9 in front of the Bohm term of QHD for fermions.« less

Electronic properties of superlattices on quantum rings.

PubMed

da Costa, D R; Chaves, A; Ferreira, W P; Farias, G A; Ferreira, R

2017-04-26

We present a theoretical study of the one-electron states of a semiconductor-made quantum ring (QR) containing a series of piecewise-constant wells and barriers distributed along the ring circumference. The single quantum well and the superlattice cases are considered in detail. We also investigate how such confining potentials affect the Aharonov-Bohm like oscillations of the energy spectrum and current in the presence of a magnetic field. The model is simple enough so as to allow obtaining various analytical or quasi-analytical results. We show that the well-in-a-ring structure presents enhanced localization features, as well as specific geometrical resonances in its above-barrier spectrum. We stress that the superlattice-in-a-ring structure allows giving a physical meaning to the often used but usually artificial Born-von-Karman periodic conditions, and discuss in detail the formation of energy minibands and minigaps for the circumferential motion, as well as several properties of the superlattice eigenstates in the presence of the magnetic field. We obtain that the Aharonov-Bohm oscillations of below-barrier miniband states are reinforced, owing to the important tunnel coupling between neighbour wells of the superlattice, which permits the electron to move in the ring. Additionally, we analysis a superlattice-like structure made of a regular distribution of ionized impurities placed around the QR, a system that may implement the superlattice in a ring idea. Finally, we consider several random disorder models, in order to study roughness disorder and to tackle the robustness of some results against deviations from the ideally nanostructured ring system.

Electronic properties of superlattices on quantum rings

NASA Astrophysics Data System (ADS)

da Costa, D. R.; Chaves, A.; Ferreira, W. P.; Farias, G. A.; Ferreira, R.

2017-04-01

We present a theoretical study of the one-electron states of a semiconductor-made quantum ring (QR) containing a series of piecewise-constant wells and barriers distributed along the ring circumference. The single quantum well and the superlattice cases are considered in detail. We also investigate how such confining potentials affect the Aharonov-Bohm like oscillations of the energy spectrum and current in the presence of a magnetic field. The model is simple enough so as to allow obtaining various analytical or quasi-analytical results. We show that the well-in-a-ring structure presents enhanced localization features, as well as specific geometrical resonances in its above-barrier spectrum. We stress that the superlattice-in-a-ring structure allows giving a physical meaning to the often used but usually artificial Born-von-Karman periodic conditions, and discuss in detail the formation of energy minibands and minigaps for the circumferential motion, as well as several properties of the superlattice eigenstates in the presence of the magnetic field. We obtain that the Aharonov-Bohm oscillations of below-barrier miniband states are reinforced, owing to the important tunnel coupling between neighbour wells of the superlattice, which permits the electron to move in the ring. Additionally, we analysis a superlattice-like structure made of a regular distribution of ionized impurities placed around the QR, a system that may implement the superlattice in a ring idea. Finally, we consider several random disorder models, in order to study roughness disorder and to tackle the robustness of some results against deviations from the ideally nanostructured ring system.

Effect of monoclonal antibodies (MoAb) to class I and class II HLA antigens on lectin- and MoAb OKT3-induced lymphocyte proliferation.

PubMed

Akiyama, Y; Zicht, R; Ferrone, S; Bonnard, G D; Herberman, R B

1985-04-01

We have examined the effect of several monoclonal antibodies (MoAb) to monomorphic determinants of class II HLA antigens, and MoAb to monomorphic determinants of class I HLA antigens and to beta-2-microglobulin (beta 2-mu) on lectin- and MoAb OKT3-induced proliferation of human peripheral blood mononuclear cells (PBMNC) and cultured T cells (CTC). Some, but not all, anti-class II HLA MoAb inhibited the proliferative response of PBMNC to MoAb OKT3 and pokeweed mitogen (PWM). The degree of inhibitory effect varied considerably. This effect was not limited to anti-class II HLA MoAb since anti-class I HLA MoAb and anti-beta 2-mu MoAb also inhibited MoAb OKT3- or PWM-induced proliferative responses. In contrast, the response of PBMNC to phytohemagglutinin (PHA) and concanavalin A (Con A) was not blocked by any anti-class II HLA MoAb. However, some anti-class II HLA MoAb also inhibited the proliferative response of CTC plus allogeneic peripheral blood adherent accessory cells (AC) to PHA or Con A as well as to MoAb OKT3 or PWM. This may be attributable to the substantially greater class II HLA antigen expression by CTC than by fresh lymphocytes. Pretreatment of either CTC or AC with anti-class II HLA MoAb inhibited OKT3-induced proliferation. In contrast, pretreatment of CTC, but not AC, with anti-class I HLA MoAb inhibited the proliferative response of CTC to OKT3. Pretreatment of CTC with anti-class I HLA MoAb inhibited PHA-, Con A and PWM-induced proliferation, to a greater degree than the anti-class II HLA MoAb. It appears as if lymphocyte activation by different mitogens exhibits variable requirements for the presence of cells expressing major histocompatibility determinants. Binding of Ab to membrane markers may interfere with lymphocyte-AC cooperation, perhaps by inhibiting binding of mitogens to their receptors or by interfering with lymphocyte and AC function. We also have examined the role of class II HLA antigens on CTC by depleting class II HLA-positive cells

mAbs

PubMed Central

2009-01-01

The twenty two monoclonal antibodies (mAbs) currently marketed in the U.S. have captured almost half of the top-20 U.S. therapeutic biotechnology sales for 2007. Eight of these products have annual sales each of more than $1 B, were developed in the relatively short average period of six years, qualified for FDA programs designed to accelerate drug approval, and their cost has been reimbursed liberally by payers. With growth of the product class driven primarily by advancements in protein engineering and the low probability of generic threats, mAbs are now the largest class of biological therapies under development. The high cost of these drugs and the lack of generic competition conflict with a financially stressed health system, setting reimbursement by payers as the major limiting factor to growth. Advances in mAb engineering are likely to result in more effective mAb drugs and an expansion of the therapeutic indications covered by the class. The parallel development of biomarkers for identifying the patient subpopulations most likely to respond to treatment may lead to a more cost-effective use of these drugs. To achieve the success of the current top-tier mAbs, companies developing new mAb products must adapt to a significantly more challenging commercial environment. PMID:20061824

Flux-periodicity crossover from h/2e to h/e in aluminium nano-loops

NASA Astrophysics Data System (ADS)

Espy, C.; Sharon, O. J.; Braun, J.; Garreis, R.; Strigl, F.; Shaulov, A.; Leiderer, P.; Scheer, E.; Yeshurun, Y.

2018-03-01

We study the magnetoresistance of aluminium ‘double-networks’ formed by connecting the vertexes of nano-loops with relatively long wires, creating two interlaced subnetworks of small and large loops (SL and LL, respectively). Far below the critical temperature, Aharonov-Bohm like quantum interference effects are observed for both the LL and the SL subnetworks. When approaching T c, both exhibit the usual Little-Parks oscillations, with periodicity of the superconducting flux quantum Φ 0 =h/2e. For one sample, with a relatively large coherence length, ξ, at temperatures very close to T c, the Φ 0 periodicity of the SL disappears, and the waveform of the first period is consistent with that predicted recently for loops with a size a < ξ, indicating a crossover to 2Φ 0 periodicity.

Wave propagation in metamaterials mimicking the topology of a cosmic string

NASA Astrophysics Data System (ADS)

Fernández-Núñez, Isabel; Bulashenko, Oleg

2018-04-01

We study the interference and diffraction of light when it propagates through a metamaterial medium mimicking the spacetime of a cosmic string—a topological defect with curvature singularity. The phenomenon may look like a gravitational analogue of the Aharonov-Bohm effect, since the light propagates in a region where the Riemann tensor vanishes, being nonetheless affected by the non-zero curvature confined to the string core. We carry out the full-wave numerical simulation of the metamaterial medium and give the analytical interpretation of the results by use of the asymptotic theory of diffraction, which turns out to be in excellent agreement. In particular, we show that the main features of wave propagation in a medium with conical singularity can be explained by four-wave interference involving two geometrical optics and two diffracted waves.

An optimum A-B scale of psychotherapist effectiveness.

PubMed

Stephens, J H; Shaffer, J W; Zlotowitz, H I

1975-04-01

On the basis of the original Whitehorn-Betz data collected over a 16-year period, it is shown that all previously derived A-B scales of psychotherapist effectiveness using Strong Vocational Interest Blank (SVIB) items are deficient in terms of correlation with the original criterion and, frequently, in terms of reliability as well. The reasons for these deficiencies are discussed, and a new experimental A-B scale is formulated and tested for adequacy. This scale is shown to possess substantial internal consistency reliability and to have a high degree of correlation with the criterion even after the removal of possible contaminating factors such as use ofancillary teatments, differences in patient prognosis, and changing practices and interest over time. It is further shown that none of the A-B scales has any validity with respect to female therapists in the original data pool. Exploration of the factor-analytic structure of this new scale and two other widely used A-B measures in terms of the occupationa scales of the SVIB reveals differential loadings on four dimensions labeled verbal/comceptual vs. manual/practical, scientific vs. sales, social concern, and artistic vs. business-oriented. It is concluded that although male therapists' scores on the best of the A-B scales may , under certain circumstances,be related to short term judged improvement in patients treated, there is little evidence that high scoring therapists are more likey than low scoring ones to have a favorable, long range impact on diagnosed schizophrenics.

Information hidden in the velocity distribution of ions and the exact kinetic Bohm criterion

NASA Astrophysics Data System (ADS)

Tsankov, Tsanko V.; Czarnetzki, Uwe

2017-05-01

Non-equilibrium distribution functions of electrons and ions play an important role in plasma physics. A prominent example is the kinetic Bohm criterion. Since its first introduction it has been controversial for theoretical reasons and due to the lack of experimental data, in particular on the ion distribution function. Here we resolve the theoretical as well as the experimental difficulties by an exact solution of the kinetic Boltzmann equation including charge exchange collisions and ionization. This also allows for the first time non-invasive measurement of spatially resolved ion velocity distributions, absolute values of the ion and electron densities, temperatures, and mean energies as well as the electric field and the plasma potential in the entire plasma. The non-invasive access to the spatially resolved distribution functions of electrons and ions is applied to the problem of the kinetic Bohm criterion. Theoretically a so far missing term in the criterion is derived and shown to be of key importance. With the new term the validity of the kinetic criterion at high collisionality and its agreement with the fluid picture are restored. All findings are supported by experimental data, theory and a numerical model with excellent agreement throughout.

Does Bohm's Quantum Force Have a Classical Origin?

NASA Astrophysics Data System (ADS)

Lush, David C.

2016-08-01

In the de Broglie-Bohm formulation of quantum mechanics, the electron is stationary in the ground state of hydrogenic atoms, because the quantum force exactly cancels the Coulomb attraction of the electron to the nucleus. In this paper it is shown that classical electrodynamics similarly predicts the Coulomb force can be effectively canceled by part of the magnetic force that occurs between two similar particles each consisting of a point charge moving with circulatory motion at the speed of light. Supposition of such motion is the basis of the Zitterbewegung interpretation of quantum mechanics. The magnetic force between two luminally-circulating charges for separation large compared to their circulatory motions contains a radial inverse square law part with magnitude equal to the Coulomb force, sinusoidally modulated by the phase difference between the circulatory motions. When the particles have equal mass and their circulatory motions are aligned but out of phase, part of the magnetic force is equal but opposite the Coulomb force. This raises a possibility that the quantum force of Bohmian mechanics may be attributable to the magnetic force of classical electrodynamics. It is further shown that relative motion between the particles leads to modulation of the magnetic force with spatial period equal to the de Broglie wavelength.

Spin-dependent thermoelectric effect and spin battery mechanism in triple quantum dots with Rashba spin-orbital interaction

NASA Astrophysics Data System (ADS)

Xu, Wei-Ping; Zhang, Yu-Ying; Wang, Qiang; Nie, Yi-Hang

2016-11-01

We have studied spin-dependent thermoelectric transport through parallel triple quantum dots with Rashba spin-orbital interaction (RSOI) embedded in an Aharonov-Bohm interferometer connected symmetrically to leads using nonequilibrium Green’s function method in the linear response regime. Under the appropriate configuration of magnetic flux phase and RSOI phase, the spin figure of merit can be enhanced and is even larger than the charge figure of merit. In particular, the charge and spin thermopowers as functions of both the magnetic flux phase and the RSOI phase present quadruple-peak structures in the contour graphs. For some specific configuration of the two phases, the device can provide a mechanism that converts heat into a spin voltage when the charge thermopower vanishes while the spin thermopower is not zero, which is useful in realizing the thermal spin battery and inducing a pure spin current in the device. Project supported by the National Natural Science Foundation of China (Grant Nos. 11274208 and 11447170).

Magnetic nanostructures.

PubMed

Bennemann, K

2010-06-23

Characteristic results of magnetism in small particles, thin films and tunnel junctions are presented. As a consequence of the reduced atomic coordination in small clusters and thin films the electronic states and density of states are modified. Thus, magnetic moments and magnetization are affected. Generally, in clusters and thin films magnetic anisotropy plays a special role. In tunnel junctions the interplay of magnetism, spin currents and superconductivity are of particular interest. In ring-like mesoscopic systems Aharonov-Bohm-induced currents are studied. Results are given for single transition metal clusters, cluster ensembles, thin films, mesoscopic structures and tunnel systems. © 2010 IOP Publishing Ltd

De Broglie-Bohm interpretation of a Hořava-Lifshitz quantum cosmology model

NASA Astrophysics Data System (ADS)

Oliveira-Neto, G.; Martins, L. G.; Monerat, G. A.; Corrêa Silva, E. V.

2018-01-01

In this paper, we consider the De Broglie-Bohm interpretation of a Hořava-Lifshitz quantum cosmology model in the presence of a radiation perfect fluid. We compute the Bohm’s trajectory for the scale factor and show that it never goes to zero. That result gives a strong indication that this model is free from singularities at the quantum level. We also compute the quantum potential. That quantity helps in understanding why the scale factor never vanishes.

Controlled parity switch of persistent currents in quantum ladders

NASA Astrophysics Data System (ADS)

Filippone, Michele; Bardyn, Charles-Edouard; Giamarchi, Thierry

2018-05-01

We investigate the behavior of persistent currents for a fixed number of noninteracting fermions in a periodic quantum ladder threaded by Aharonov-Bohm and transverse magnetic fluxes Φ and χ . We show that the coupling between ladder legs provides a way to effectively change the ground-state fermion-number parity, by varying χ . Specifically, we demonstrate that varying χ by 2 π (one flux quantum) leads to an apparent fermion-number parity switch. We find that persistent currents exhibit a robust 4 π periodicity as a function of χ , despite the fact that χ →χ +2 π leads to modifications of order 1 /N of the energy spectrum, where N is the number of sites in each ladder leg. We show that these parity-switch and 4 π periodicity effects are robust with respect to temperature and disorder, and outline potential physical realizations using cold atomic gases and photonic lattices, for bosonic analogs of the effects.

The problems in quantum foundations in the light of gauge theories

NASA Astrophysics Data System (ADS)

Ne'Eman, Yuval

1986-04-01

We review the issues of nonseparability and seemingly acausal propagation of information in EPR, as displayed by experiments and the failure of Bell's inequalities. We show that global effects are in the very nature of the geometric structure of modern physical theories, occurring even at the classical level. The Aharonov-Bohm effect, magnetic monopoles, instantons, etc. result from the topology and homotopy features of the fiber bundle manifolds of gauge theories. The conservation of probabilities, a supposedly highly quantum effect, is also achieved through global geometry equations. The EPR observables all fit in such geometries, and space-time is a truncated representation and is not the correct arena for their understanding. Relativistic quantum field theory represents the global action of the measurement operators as the zero-momentum (and therefore spatially infinitely spread) limit of their wave functions (form factors). We also analyze the collapse of the state vector as a case of spontaneous symmetry breakdown in the apparatus-observed state interaction.

Non Target Effect of Cry1 Ab and Cry Ab x Cry3 Bb1 Bt Transgenic Maize on Orius Insidiosus (Hemiptera: Anthocoridae) Abundance

USDA-ARS?s Scientific Manuscript database

Non-target effects of Cry1Ab x CP4 EPSPS and Cry1Ab + Cry3Bb1 x CP4 EPSPS Bt transgenic new maize hybrids on insidious flower bugs [Orius insidiosus (Say)] was studied in Nebraska (Mead, C lay Center, and Concord) during 2007 and 2008. The Bt effect was compared to CP4 EPSPS maize (isoline), convent...

Deletion of nfnAB in Thermoanaerobacterium saccharolyticum and Its Effect on Metabolism

DOE PAGES

Lo, Jonathan; Zheng, Tianyong; Olson, Daniel G.; ...

2015-06-29

NfnAB catalyzes the reversible transfer of electrons from reduced ferredoxin and NADH to 2 NADP +. The NfnAB complex has been hypothesized to be the main enzyme for ferredoxin oxidization in strains of Thermoanaerobacterium saccharolyticum engineered for increased ethanol production. NfnAB complex activity was detectable in crude cell extracts of T. saccharolyticum. In this paper, activity was also detected using activity staining of native PAGE gels. The nfnAB gene was deleted in different strains of T. saccharolyticum to determine its effect on end product formation. In wild-type T. saccharolyticum, deletion of nfnAB resulted in a 46% increase in H 2more » formation but otherwise little change in other fermentation products. In two engineered strains with 80% theoretical ethanol yield, loss of nfnAB caused two different responses: in one strain, ethanol yield decreased to about 30% of the theoretical value, while another strain had no change in ethanol yield. Biochemical analysis of cell extracts showed that the ΔnfnAB strain with decreased ethanol yield had NADPH-linked alcohol dehydrogenase (ADH) activity, while the ΔnfnAB strain with unchanged ethanol yield had NADH-linked ADH activity. Deletion of nfnAB caused loss of NADPH-linked ferredoxin oxidoreductase activity in all cell extracts. Significant NADH-linked ferredoxin oxidoreductase activity was seen in all cell extracts, including those that had lost nfnAB. This suggests that there is an unidentified NADH:ferredoxin oxidoreductase (distinct from nfnAB) playing a role in ethanol formation. The NfnAB complex plays a key role in generating NADPH in a strain that had become reliant on NADPH-ADH activity. Importance: Thermophilic anaerobes that can convert biomass-derived sugars into ethanol have been investigated as candidates for biofuel formation. Many anaerobes have been genetically engineered to increase biofuel formation; however, key aspects of metabolism remain unknown and poorly understood. One

DR5 mAb-conjugated, DTIC-loaded immuno-nanoparticles effectively and specifically kill malignant melanoma cells in vivo.

PubMed

Ding, Baoyue; Zhang, Wei; Wu, Xin; Wang, Jeffrey; Xie, Chen; Huang, Xuan; Zhan, Shuyu; Zheng, Yongxia; Huang, Yueyan; Xu, Ningyin; Ding, Xueying; Gao, Shen

2016-08-30

We combined chemo- and immunotherapies by constructing dual therapeutic function immuno-nanoparticles (NPs) consisting of death receptor 5 monoclonal antibody (DR5 mAb)-conjugated nanoparticles loaded with dacarbazine (DTIC) (DTIC-NPs-DR5 mAb). We determined the in vivo targeting specificity of DTIC-NPs-DR5 mAb by evaluating distribution in tumor-bearing nude mice using a real-time imaging system. Therapeutic efficacy was assessed in terms of its effect on tumor volume, survival time, histomorphology, microvessel density (MVD), and apoptotic index (AI). Systemic toxicity was evaluated by measuring white blood cells (WBC) counts, alanine aminotransferase (ALT) levels, and creatinine clearance (CR).In vivo and ex vivo imaging indicates that DR5 mAb modification enhanced the accumulation of NPs within the xenograft tumor. DTIC-NPs-DR5 mAb inhibited tumor growth more effectively than DTIC or DR5 mAb alone, indicating that combining DTIC and DR5 mAb through pharmaceutical engineering achieves a better therapeutic effect. Moreover, the toxicity of DTIC-NPs-DR5 mAb was much lower than that of DTIC, implying that DR5 mAb targeting reduces nonspecific uptake of DTIC into normal tissue and thus decreases toxic side effects. These results demonstrate that DTIC-NPs-DR5 mAb is a safe and effective nanoparticle formulation with the potential to improve the efficacy and specificity of melanoma treatment.

Spin power and efficiency in an Aharnov-Bohm ring with an embedded magnetic impurity quantum dot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Xi; Guo, Yong, E-mail: guoy66@tsinghua.edu.cn; Collaborative Innovation Center of Quantum Matter, Beijing

2015-05-11

Spin thermoelectric effects in an Aharnov-Bohm ring with a magnetic impurity quantum dot (QD) are theoretically investigated by using the nonequilibrium Green's function method. It is found that due to the exchange coupling between the impurity and the electrons in QD, spin output power, and efficiency can be significant and be further modulated by the gate voltage. The spin thermoelectric effect can be modulated effectively by adjusting the Rashba spin-orbit interaction (RSOI) and the magnetic flux. The spin power and efficiency show zigzag oscillations, and thus spin thermoelectric effect can be switched by adjusting the magnetic flux phase factor andmore » RSOI ones. In addition, the spin efficiency can be significantly enhanced by the coexistence of the RSOI and the magnetic flux, and the maximal value of normalized spin efficiency η{sub max}/η{sub C} = 0.35 is obtained. Our results show that such a QD ring device may be used as a manipulative spin thermoelectric generator.« less

DR5 mAb-conjugated, DTIC-loaded immuno-nanoparticles effectively and specifically kill malignant melanoma cells in vivo

PubMed Central

Wang, Jeffrey; Xie, Chen; Huang, Xuan; Zhan, Shuyu; Zheng, Yongxia; Huang, Yueyan; Xu, Ningyin; Ding, Xueying; Gao, Shen

2016-01-01

We combined chemo- and immunotherapies by constructing dual therapeutic function immuno-nanoparticles (NPs) consisting of death receptor 5 monoclonal antibody (DR5 mAb)-conjugated nanoparticles loaded with dacarbazine (DTIC) (DTIC-NPs-DR5 mAb). We determined the in vivo targeting specificity of DTIC-NPs-DR5 mAb by evaluating distribution in tumor-bearing nude mice using a real-time imaging system. Therapeutic efficacy was assessed in terms of its effect on tumor volume, survival time, histomorphology, microvessel density (MVD), and apoptotic index (AI). Systemic toxicity was evaluated by measuring white blood cells (WBC) counts, alanine aminotransferase (ALT) levels, and creatinine clearance (CR).In vivo and ex vivo imaging indicates that DR5 mAb modification enhanced the accumulation of NPs within the xenograft tumor. DTIC-NPs-DR5 mAb inhibited tumor growth more effectively than DTIC or DR5 mAb alone, indicating that combining DTIC and DR5 mAb through pharmaceutical engineering achieves a better therapeutic effect. Moreover, the toxicity of DTIC-NPs-DR5 mAb was much lower than that of DTIC, implying that DR5 mAb targeting reduces nonspecific uptake of DTIC into normal tissue and thus decreases toxic side effects. These results demonstrate that DTIC-NPs-DR5 mAb is a safe and effective nanoparticle formulation with the potential to improve the efficacy and specificity of melanoma treatment. PMID:27494835

Scattering amplitude and bosonization duality in general Chern-Simons vector models

NASA Astrophysics Data System (ADS)

Yokoyama, Shuichi

2016-09-01

We present the exact large N calculus of four point functions in general Chern-Simons bosonic and fermionic vector models. Applying the LSZ formula to the four point function we determine the two body scattering amplitudes in these theories taking a special care for a non-analytic term to achieve unitarity in the singlet channel. We show that the S-matrix enjoys the bosonization duality, an unusual crossing relation and a non-relativistic reduction to Aharonov-Bohm scattering. We also argue that the S-matrix develops a pole in a certain range of coupling constants, which disappears in the range where the theory reduces to the Chern-Simons theory interacting with free fermions.

Conductance oscillations of core-shell nanowires in transversal magnetic fields

NASA Astrophysics Data System (ADS)

Manolescu, Andrei; Nemnes, George Alexandru; Sitek, Anna; Rosdahl, Tomas Orn; Erlingsson, Sigurdur Ingi; Gudmundsson, Vidar

2016-05-01

We analyze theoretically electronic transport through a core-shell nanowire in the presence of a transversal magnetic field. We calculate the conductance for a variable coupling between the nanowire and the attached leads and show how the snaking states, which are low-energy states localized along the lines of the vanishing radial component of the magnetic field, manifest their existence. In the strong-coupling regime they induce flux periodic, Aharonov-Bohm-like, conductance oscillations, which, by decreasing the coupling to the leads, evolve into well-resolved peaks. The flux periodic oscillations arise due to interference of the snaking states, which is a consequence of backscattering at either the contacts with leads or magnetic or potential barriers in the wire.

An "unreasonable effectiveness" of Hilbert transform for the transition phase behavior in an Aharonov-Bohm two-path interferometer

NASA Astrophysics Data System (ADS)

Englman, R.

2016-08-01

The recent phase shift data of Takada et al. (Phys. Rev. Lett. 113 (2014) 126601) for a two level system are reconstructed from their current intensity curves by the method of Hilbert transform, for which the underlying Physics is the principle of causality. An introductory algebraic model illustrates pedagogically the working of the method and leads to newly derived relationships involving phenomenological parameters, in particular for the sign of the phase slope between the resonance peaks. While the parametrization of the experimental current intensity data in terms of a few model parameters shows only a qualitative agreement for the phase shift, due to the strong impact of small, detailed variations in the experimental intensity curve on the phase behavior, the numerical Hilbert transform yields a satisfactory reproduction of the phase.

Single, Complete, Probability Spaces Consistent With EPR-Bohm-Bell Experimental Data

NASA Astrophysics Data System (ADS)

Avis, David; Fischer, Paul; Hilbert, Astrid; Khrennikov, Andrei

2009-03-01

We show that paradoxical consequences of violations of Bell's inequality are induced by the use of an unsuitable probabilistic description for the EPR-Bohm-Bell experiment. The conventional description (due to Bell) is based on a combination of statistical data collected for different settings of polarization beam splitters (PBSs). In fact, such data consists of some conditional probabilities which only partially define a probability space. Ignoring this conditioning leads to apparent contradictions in the classical probabilistic model (due to Kolmogorov). We show how to make a completely consistent probabilistic model by taking into account the probabilities of selecting the settings of the PBSs. Our model matches both the experimental data and is consistent with classical probability theory.

Modified transverse phonon-helicon interaction in colloids laden semiconductor plasmas due to Bohm potential and Fermi degenerate pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Aartee, E-mail: aartee.sharma08@gmail.com; Yadav, N.; Ghosh, S.

2015-07-31

A detailed study of the quantum modification of acousto-helicon wave spectra due to Bohm potential and Fermi degenerate pressure in colloids laden semiconductor plasma has been presented. We have used quantum hydrodynamic model of plasmas to arrive at most general dispersion relation in presence of magnetic field. This dispersion relation has been analyzed in three different velocity regimes and the expressions for gain constants have been obtained. From the present study it has been concluded that the quantum effect and the magnetic field significantly modify the wave characteristics particularly in high doping regime in semiconductor plasma medium in presence ofmore » colloids in it.« less

Monoclonal antibody, mAb 4C13, an effective detoxicant antibody against ricin poisoning.

PubMed

Dong, Na; Luo, Longlong; Wu, Junhua; Jia, Peiyuan; Li, Qian; Wang, Yuxia; Gao, Zhongcai; Peng, Hui; Lv, Ming; Huang, Chunqian; Feng, Jiannan; Li, Hua; Shan, Junjie; Han, Gang; Shen, Beifen

2015-07-31

Ricin is a glycoprotein produced in castor seeds and consists of two polypeptide chains named Ricin Toxin A Chain (RTA) and Ricin Toxin B Chain (RTB), linked via a disulfide bridge. Due to its high toxicity, ricin is regarded as a high terrorist risk for the public. However, antibodies can play a pivotal role in neutralizing the toxin. In this research, the anti-toxicant effect of mAb 4C13, a monoclonal antibody (mAb) established using detoxicated ricin as the immunized antigen, was evaluated. Compared with mAb 4F2 and mAb 5G6, the effective mechanism of mAb 4C13 was analyzed by experiments relating to its cytotoxicity, epitope on ricin, binding kinetics with the toxin, its blockage on the protein synthesis inhibition induced by ricin and the intracelluar tracing of its complex with ricin. Our result indicated that mAb 4C13 could recognize and bind to RTA, RTB and exert its high affinity to the holotoxin. Both cytotoxicity and animal toxicity of ricin were well blocked by pre-incubating the toxin with mAb 4C13. By intravenous injection, mAb 4C13 could rescue the mouse intraperitoneally (ip) injected with a lethal dose of ricin (20μg/kg) even at 6h after the intoxication and its efficacy was dependent on its dosage. This research indicated that mAb 4C13 could be an excellent candidate for therapeutic antibodies. Its potent antitoxic efficiency was related to its recognition on the specific epitope with very high affinity and its blockage of protein synthesis inhibition in cytoplasm followed by cellular internalization with ricin. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effectiveness of motorcycle antilock braking systems (ABS) in reducing crashes, the first cross-national study.

PubMed

Rizzi, Matteo; Strandroth, Johan; Kullgren, Anders; Tingvall, Claes; Fildes, Brian

2015-01-01

This study set out to evaluate the effectiveness of motorcycle antilock braking systems (ABS) in reducing real-life crashes. Since the European Parliament has voted on legislation making ABS mandatory on all new motorcycles over 125 cc from 2016, the fitment rate in Europe is likely to increase in the coming years. Though previous research has focused on mostly large displacement motorcycles, this study used police reports from Spain (2006-2009), Italy (2009), and Sweden (2003-2012) in order to analyze a wide range of motorcycles, including scooters, and compare countries with different motorcycling habits. The statistical analysis used odds ratio calculations with an induced exposure approach. Previous research found that head-on crashes were the least ABS-affected crash type and was therefore used as the nonsensitive crash type for ABS in these calculations. The same motorcycle models, with and without ABS, were compared and the calculations were carried out for each country separately. Crashes involving only scooters were further analyzed. The effectiveness of motorcycle ABS in reducing injury crashes ranged from 24% (95% confidence interval [CI], 12-36) in Italy to 29% (95% CI, 20-38) in Spain, and 34% (95% CI, 16-52) in Sweden. The reductions in severe and fatal crashes were even greater, at 34% (95% CI, 24-44) in Spain and 42% (95% CI, 23-61) in Sweden. The overall reductions of crashes involving ABS-equipped scooters (at least 250 cc) were 27% (95% CI, 12-42) in Italy and 22% (95% CI, 2-42) in Spain. ABS on scooters with at least a 250 cc engine reduced severe and fatal crashes by 31% (95% CI, 12-50), based on Spanish data alone. At this stage, there is more than sufficient scientific-based evidence to support the implementation of ABS on all motorcycles, even light ones. Further research should aim at understanding the injury mitigating effects of motorcycle ABS, possibly in combination with combined braking systems.

Quantum motion of a point particle in the presence of the Aharonov–Bohm potential in curved space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva, Edilberto O., E-mail: edilbertoo@gmail.com; Ulhoa, Sérgio C., E-mail: sc.ulhoa@gmail.com; Andrade, Fabiano M., E-mail: f.andrade@ucl.ac.uk

The nonrelativistic quantum dynamics of a spinless charged particle in the presence of the Aharonov–Bohm potential in curved space is considered. We chose the surface as being a cone defined by a line element in polar coordinates. The geometry of this line element establishes that the motion of the particle can occur on the surface of a cone or an anti-cone. As a consequence of the nontrivial topology of the cone and also because of two-dimensional confinement, the geometric potential should be taken into account. At first, we establish the conditions for the particle describing a circular path in suchmore » a context. Because of the presence of the geometric potential, which contains a singular term, we use the self-adjoint extension method in order to describe the dynamics in all space including the singularity. Expressions are obtained for the bound state energies and wave functions. -- Highlights: •Motion of particle under the influence of magnetic field in curved space. •Bound state for Aharonov–Bohm problem. •Particle describing a circular path. •Determination of the self-adjoint extension parameter.« less

A caged Ab reveals an immediate/instructive effect of BDNF during hippocampal synaptic potentiation

PubMed Central

Kossel, Albrecht H.; Cambridge, Sidney B.; Wagner, Uta; Bonhoeffer, Tobias

2001-01-01

Neurotrophins have been shown to be involved in functional strengthening of central nervous system synapses. Although their general importance in this process is undisputed, it remains unresolved whether neurotrophins are truly mediators of synaptic strengthening or merely important cofactors. To address this question, we have devised a method to inactivate endogenous brain-derived neurotrophic factor (BDNF) with high time resolution by “caging” a function-blocking mAb against BDNF with a photosensitive protecting compound. Different assays were used to show that this inactivation of the Ab is reversible by UV light. Synaptic potentiation after τ-burst stimulation in the CA1 region of acute hippocampal slices was significantly less when applying the unmodified Ab compared with the caged Ab. Importantly, photoactivation of the caged Ab during the time of induction of synaptic enhancement led to a marked decrease in potentiation. Our experiments therefore strengthen the view that endogenous BDNF has fast effects during induction of synaptic plasticity. The results additionally show that caged Abs can provide a tool for precise spatiotemporal control over endogenous protein levels. PMID:11724927

A survey of existing and proposed classical and quantum approaches to the photon mass

NASA Astrophysics Data System (ADS)

Spavieri, G.; Quintero, J.; Gillies, G. T.; Rodríguez, M.

2011-02-01

Over the past twenty years, there have been several careful experimental, observational and phenomenological investigations aimed at searching for and establishing ever tighter bounds on the possible mass of the photon. There are many fascinating and paradoxical physical implications that would arise from the presence of even a very small value for it, and thus such searches have always been well motivated in terms of the new physics that would result. We provide a brief overview of the theoretical background and classical motivations for this work and the early tests of the exactness of Coulomb's law that underlie it. We then go on to address the modern situation, in which quantum physics approaches come to attention. Among them we focus especially on the implications that the Aharonov-Bohm and Aharonov-Casher class of effects have on searches for a photon mass. These arise in several different ways and can lead to experiments that might involve the interaction of magnetic dipoles, electric dipoles, or charged particles with suitable potentials. Still other quantum-based approaches employ measurements of the g-factor of the electron. Plausible target sensitivities for limits on the photon mass as sought by the various quantum approaches are in the range of 10-53 to 10-54 g. Possible experimental arrangements for the associated experiments are discussed. We close with an assessment of the state of the art and a prognosis for future work.

mAbs: a business perspective.

PubMed

Scolnik, Pablo A

2009-01-01

The twenty two monoclonal antibodies (mAbs) currently marketed in the U.S. have captured almost half of the top-20 U.S. therapeutic biotechnology sales for 2007. Eight of these products have annual sales each of more than $1 B, were developed in the relatively short average period of six years, qualified for FDA programs designed to accelerate drug approval, and their cost has been reimbursed liberally by payers. With growth of the product class driven primarily by advancements in protein engineering and the low probability of generic threats, mAbs are now the largest class of biological therapies under development. The high cost of these drugs and the lack of generic competition conflict with a financially stressed health system, setting reimbursement by payers as the major limiting factor to growth. Advances in mAb engineering are likely to result in more effective mAb drugs and an expansion of the therapeutic indications covered by the class. The parallel development of biomarkers for identifying the patient subpopulations most likely to respond to treatment may lead to a more cost-effective use of these drugs. To achieve the success of the current top-tier mAbs, companies developing new mAb products must adapt to a significantly more challenging commercial environment.

AB-CHMINACA, AB-PINACA, and FUBIMINA: Affinity and Potency of Novel Synthetic Cannabinoids in Producing Δ9-Tetrahydrocannabinol–Like Effects in Mice

PubMed Central

Marusich, Julie A.; Lefever, Timothy W.; Antonazzo, Kateland R.; Wallgren, Michael T.; Cortes, Ricardo A.; Patel, Purvi R.; Grabenauer, Megan; Moore, Katherine N.

2015-01-01

Diversion of synthetic cannabinoids for abuse began in the early 2000s. Despite legislation banning compounds currently on the drug market, illicit manufacturers continue to release new compounds for recreational use. This study examined new synthetic cannabinoids, AB-CHMINACA (N-[1-amino-3-methyl-oxobutan-2-yl]-1-[cyclohexylmethyl]-1H-indazole-3-carboxamide), AB-PINACA [N-(1-amino-3-methyl-1-oxobutan-2-yl)-1-pentyl-1H-indazole-3-carboxamide], and FUBIMINA [(1-(5-fluoropentyl)-1H-benzo[d]imadazol-2-yl)(naphthalen-1-yl)methanone], with the hypothesis that these compounds, like those before them, would be highly susceptible to abuse. Cannabinoids were examined in vitro for binding and activation of CB1 receptors, and in vivo for pharmacological effects in mice and in Δ9-tetrahydrocannabinol (Δ9-THC) discrimination. AB-CHMINACA, AB-PINACA, and FUBIMINA bound to and activated CB1 and CB2 receptors, and produced locomotor suppression, antinociception, hypothermia, and catalepsy. Furthermore, these compounds, along with JWH-018 [1-pentyl-3-(1-naphthoyl)indole], CP47,497 [rel-5-(1,1-dimethylheptyl)-2-[(1R,3S)-3-hydroxycyclohexyl]-phenol], and WIN55,212-2 ([(3R)-2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-naphthalenyl-methanone, monomethanesulfonate), substituted for Δ9-THC in Δ9-THC discrimination. Rank order of potency correlated with CB1 receptor-binding affinity, and all three compounds were full agonists in [35S]GTPγS binding, as compared with the partial agonist Δ9-THC. Indeed, AB-CHMINACA and AB-PINACA exhibited higher efficacy than most known full agonists of the CB1 receptor. Preliminary analysis of urinary metabolites of the compounds revealed the expected hydroxylation. AB-PINACA and AB-CHMINACA are of potential interest as research tools due to their unique chemical structures and high CB1 receptor efficacies. Further studies on these chemicals are likely to include research on understanding cannabinoid receptors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leung, P. T.; Young, K.

Reciprocity in wave propagation usually refers to the symmetry of the Green's function under the interchange of the source and the observer coordinates, but this condition is not gauge invariant in quantum mechanics, a problem that is particularly significant in the presence of a vector potential. Several possible alternative criteria are given and analyzed with reference to different examples with nonzero magnetic fields and/or vector potentials, including the case of a multiply connected spatial domain. It is shown that the appropriate reciprocity criterion allows for specific phase factors separable into functions of the source and observer coordinates and that thismore » condition is robust with respect to the addition of any scalar potential. In the Aharonov-Bohm effect, reciprocity beyond monoenergetic experiments holds only because of subsidiary conditions satisfied in actual experiments: the test charge is in units of e and the flux is produced by a condensate of particles with charge 2e.« less

Fabry-Perot Interferometry in the Integer and Fractional Quantum Hall Regimes

NASA Astrophysics Data System (ADS)

McClure, Douglas; Chang, Willy; Kou, Angela; Marcus, Charles; Pfeiffer, Loren; West, Ken

2011-03-01

We present measurements of electronic Fabry-Perot interferometers in the integer and fractional quantum Hall regimes. Two classes of resistance oscillations may be seen as a function of magnetic field and gate voltage, as we have previously reported. In small interferometers in the integer regime, oscillations of the type associated with Coulomb interaction are ubiquitous, while those consistent with single-particle Aharonov-Bohm interference are seen to co-exist in some configurations. The amplitude scaling of both types with temperature and device size is consistent with a theoretical model. Oscillations are further observed in the fractional quantum Hall regime. Here the dependence of the period on the filling factors in the constrictions and bulk of the interferometer can shed light on the effective charge of the interfering quasiparticles, but care is needed to distinguish these oscillations from those associated with integer quantum Hall states. We acknowledge funding from Microsoft Project Q and IBM.

Experimental Demonstration of a Synthetic Lorentz Force by Using Radiation Pressure.

PubMed

Šantić, N; Dubček, T; Aumiler, D; Buljan, H; Ban, T

2015-09-02

Synthetic magnetism in cold atomic gases opened the doors to many exciting novel physical systems and phenomena. Ubiquitous are the methods used for the creation of synthetic magnetic fields. They include rapidly rotating Bose-Einstein condensates employing the analogy between the Coriolis and the Lorentz force, and laser-atom interactions employing the analogy between the Berry phase and the Aharonov-Bohm phase. Interestingly, radiation pressure - being one of the most common forces induced by light - has not yet been used for synthetic magnetism. We experimentally demonstrate a synthetic Lorentz force, based on the radiation pressure and the Doppler effect, by observing the centre-of-mass motion of a cold atomic cloud. The force is perpendicular to the velocity of the cold atomic cloud, and zero for the cloud at rest. Our novel concept is straightforward to implement in a large volume, for a broad range of velocities, and can be extended to different geometries.

N-Sulfonyl-β-lactam hapten as an effective labeling reagent for aldolase mAb.

PubMed

Inokuma, Tsubasa; Fuller, Roberta P; Barbas, Carlos F

2015-04-15

Utilization of chemically programmed antibodies (cpAbs) is regarded to be one of the most efficient methods for the development of therapeutic systems. cpAbs can extend the half-life of programming reagents, activate immune systems via the Fc region of antibodies and achieve universal vaccination by attaching varieties of small, programmed molecules. In the current study, we aimed to develop a novel labeling reagent for the preparation of cpAbs and found that N-sulfonyl-β-lactams (NSBLs) were optimal. NSBL can be synthesized from readily available 4-(bromomethyl)benzenesulfonyl chloride via few simple manipulations and can label the aldolase monoclonal antibody (mAb) 84G3, which could not be labeled effectively by the conventional labeling reagent, N-acyl-β-lactam (NABL). We also demonstrated that the conjugate, which consists of mAb 84G3 and an NSBL bearing a biotin moiety, maintained strong binding activity to streptavidin. In addition, the stability assay of NSBL revealed that NSBLs can tolerate aqueous media without significant decomposition over 24h. Copyright © 2015 Elsevier Ltd. All rights reserved.

Manifestations of Surface States in the Longitudinal Magnetoresistance of an Array of Bi Nanowires

NASA Astrophysics Data System (ADS)

Latyshev, Yu. I.; Frolov, A. V.; Volkov, V. A.; Wade, T.; Prudkoglyad, V. A.; Orlov, A. P.; Pudalov, V. M.; Konczykowski, M.

2018-04-01

The longitudinal magnetoresistance of the array of parallel-oriented bismuth nanowires each 100 nm in diameter grown by electrochemical deposition in nanopores of an Al2O3 membrane has been studied in magnetic fields up to 14 T and at temperatures down to 0.3 K. The resistance increases with the field and reaches a broad maximum in fields about 10 T. An anomalous increase in the resistance in weak fields is qualitatively consistent with the suppression of the antilocalization correction to the resistance, and the maximum is qualitatively associated with the classical size effect. Near the maximum at temperatures below 0.8 K, manifestations of reproducible magneto-oscillations of the resistance, which are periodic in field, have been detected. The period of these oscillations is close to a value corresponding to the passage of the flux quantum hc/ e through the section of a nanowire. The Fourier analysis also confirms that the oscillations are periodic. This result is similar to the manifestation the Aharonov-Bohm effect caused by conducting surface states of Dirac fermions occupying L-valleys of bismuth.

Memories of AB

NASA Astrophysics Data System (ADS)

Vaks, V. G.

2013-06-01

I had the good fortune to be a student of A. B. Migdal - AB, as we called him in person or in his absence - and to work in the sector he headed at the Kurchatov Institute, along with his other students and my friends, including Vitya Galitsky, Spartak Belyayev and Tolya Larkin. I was especially close with AB in the second half of the 1950s, the years most important for my formation, and AB's contribution to this formation was very great. To this day, I've often quoted AB on various occasions, as it's hard to put things better or more precisely than he did; I tell friends stories heard from AB, because these stories enhance life as AB himself enhanced it; my daughter is named Tanya after AB's wife Tatyana Lvovna, and so on. In what follows, I'll recount a few episodes in my life in which AB played an important or decisive role, and then will share some other memories of AB...

Einstein-Podolsky-Rosen-Bohm experiment and Bell inequality violation using Type 2 parametric down conversion

NASA Technical Reports Server (NTRS)

Kiess, Thomas E.; Shih, Yan-Hua; Sergienko, A. V.; Alley, Carroll O.

1994-01-01

We report a new two-photon polarization correlation experiment for realizing the Einstein-Podolsky-Rosen-Bohm (EPRB) state and for testing Bell-type inequalities. We use the pair of orthogonally-polarized light quanta generated in Type 2 parametric down conversion. Using 1 nm interference filters in front of our detectors, we observe from the output of a 0.5mm beta - BaB2O4 (BBO) crystal the EPRB correlations in coincidence counts, and measure an associated Bell inequality violation of 22 standard deviations. The quantum state of the photon pair is a polarization analog of the spin-1/2 singlet state.

Effects of goat manure liquid fertilizer combined with AB-MIX on foliage vegetables growth in hydroponic

NASA Astrophysics Data System (ADS)

Sunaryo, Y.; Purnomo, D.; Darini, M. T.; Cahyani, V. R.

2018-03-01

Hydroponic as one of the protected cultivation practices is very important to be developed in Indonesia due to not only the reduction of arable agricultural lands in lines with increasing of residential demand and other public facilities but also due to the negative influences of climate change as well global warming to plant growth. The effects of liquid fertilizer made from goat manure (LFGM) in combination with AB-Mix on three kinds of foliage vegetable growth was examined in hydroponics. The research was conducted by 3 x 4 factorial experiment and arranged in Completely Randomized Design with 3 replications. The first factor was foliage vegetable consisting of 3 levels: Mustard Green, Lettuce, and Red Spinach. The second factor was the mixture composition of nutrient solution consisting of 4 levels: LFGM + AB-Mix (v/v: 1:1), LFGM + AB-Mix (v/v: 1:3), LFGM + AB-Mix (v/v: 3:1), and A/B mix as control. Results indicated that the application of LFGM + AB-Mix (v/v: 1:3) resulted in similar plant growth as control (AB-Mix application), and also resulted in the highest chlorophyll content of Mustard green.

Protective Measurement and Quantum Reality

NASA Astrophysics Data System (ADS)

Gao, Shan

2015-01-01

1. Protective measurements: an introduction Shan Gao; Part I. Fundamentals and Applications: 2. Protective measurements of the wave function of a single system Lev Vaidman; 3. Protective measurement, postselection and the Heisenberg representation Yakir Aharonov and Eliahu Cohen; 4. Protective and state measurement: a review Gennaro Auletta; 5. Determination of the stationary basis from protective measurement on a single system Lajos Diósi; 6. Weak measurements, the energy-momentum tensor and the Bohm approach Robert Flack and Basil J. Hiley; Part II. Meanings and Implications: 7. Measurement and metaphysics Peter J. Lewis; 8. Protective measurements and the explanatory gambit Michael Dickson; 9. Realism and instrumentalism about the wave function: how should we choose? Mauro Dorato and Frederico Laudisa; 10. Protective measurements and the PBR theorem Guy Hetzroni and Daniel Rohrlich; 11. The roads not taken: empty waves, waveform collapse and protective measurement in quantum theory Peter Holland; 12. Implications of protective measurements on de Broglie-Bohm trajectories Aurelien Drezet; 13. Entanglement, scaling, and the meaning of the wave function in protective measurement Maximilian Schlosshauer and Tangereen V. B. Claringbold; 14. Protective measurements and the nature of the wave function within the primitive ontology approach Vincent Lam; 15. Reality and meaning of the wave function Shan Gao; Index.

Magnetic field dependence of electronic properties of MoS2 quantum dots with different edges

NASA Astrophysics Data System (ADS)

Chen, Qiao; Li, L. L.; Peeters, F. M.

2018-02-01

Using the tight-binding approach, we investigate the energy spectrum of square, triangular, and hexagonal MoS2 quantum dots (QDs) in the presence of a perpendicular magnetic field. Novel edge states emerge in MoS2 QDs, which are distributed over the whole edge which we call ring states. The ring states are robust in the presence of spin-orbit coupling (SOC). The corresponding energy levels of the ring states oscillate as a function of the perpendicular magnetic field which are related to Aharonov-Bohm oscillations. Oscillations in the magnetic field dependence of the energy levels and the peaks in the magneto-optical spectrum emerge (disappear) as the ring states are formed (collapsed). The period and the amplitude of the oscillation decrease with the size of the MoS2 QDs.

Conductance maps of quantum rings due to a local potential perturbation.

PubMed

Petrović, M D; Peeters, F M; Chaves, A; Farias, G A

2013-12-11

We performed a numerical simulation of the dynamics of a Gaussian shaped wavepacket inside a small sized quantum ring, smoothly connected to two leads and exposed to a perturbing potential of a biased atomic force microscope tip. Using the Landauer formalism, we calculated conductance maps of this system in the case of single and two subband transport. We explain the main features in the conductance maps as due to the AFM tip influence on the wavepacket phase and amplitude. In the presence of an external magnetic field, the tip modifies the ϕ0 periodic Aharonov-Bohm oscillation pattern into a ϕ0/2 periodic Al'tshuler-Aronov-Spivak oscillation pattern. Our results in the case of multiband transport suggest tip selectivity to higher subbands, making them more observable in the total conductance map.

Topologically protected excitons in porphyrin thin films

NASA Astrophysics Data System (ADS)

Yuen-Zhou, Joel; Saikin, Semion K.; Yao, Norman Y.; Aspuru-Guzik, Alán

2014-11-01

The control of exciton transport in organic materials is of fundamental importance for the development of efficient light-harvesting systems. This transport is easily deteriorated by traps in the disordered energy landscape. Here, we propose and analyse a system that supports topological Frenkel exciton edge states. Backscattering of these chiral Frenkel excitons is prohibited by symmetry, ensuring that the transport properties of such a system are robust against disorder. To implement our idea, we propose a two-dimensional periodic array of tilted porphyrins interacting with a homogeneous magnetic field. This field serves to break time-reversal symmetry and results in lattice fluxes that mimic the Aharonov-Bohm phase acquired by electrons. Our proposal is the first blueprint for realizing topological phases of matter in molecular aggregates and suggests a paradigm for engineering novel excitonic materials.

Antiresonance and decoupling in electronic transport through parallel-coupled quantum-dot structures with laterally-coupled Majorana zero modes

NASA Astrophysics Data System (ADS)

Zhang, Ya-Jing; Zhang, Lian-Lian; Jiang, Cui; Gong, Wei-Jiang

2018-02-01

We theoretically investigate the electronic transport through a parallel-coupled multi-quantum-dot system, in which the terminal dots of a one-dimensional quantum-dot chain are embodied in the two arms of an Aharonov-Bohm interferometer. It is found that in the structures of odd(even) dots, all their even(odd) molecular states have opportunities to decouple from the leads, and in this process antiresonance occurs which are accordant with the odd(even)-numbered eigenenergies of the sub-molecule without terminal dots. Next when Majorana zero modes are introduced to couple laterally to the terminal dots, the antiresonance and decoupling phenomena still co-exist in the quantum transport process. Such a result can be helpful in understanding the special influence of Majorana zero mode on the electronic transport through quantum-dot systems.

Dynamics and Hall-edge-state mixing of localized electrons in a two-channel Mach-Zehnder interferometer

NASA Astrophysics Data System (ADS)

Bellentani, Laura; Beggi, Andrea; Bordone, Paolo; Bertoni, Andrea

2018-05-01

We present a numerical study of a multichannel electronic Mach-Zehnder interferometer, based on magnetically driven noninteracting edge states. The electron path is defined by a full-scale potential landscape on the two-dimensional electron gas at filling factor 2, assuming initially only the first Landau level as filled. We tailor the two beamsplitters with 50 % interchannel mixing and measure Aharonov-Bohm oscillations in the transmission probability of the second channel. We perform time-dependent simulations by solving the electron Schrödinger equation through a parallel implementation of the split-step Fourier method, and we describe the charge-carrier wave function as a Gaussian wave packet of edge states. We finally develop a simplified theoretical model to explain the features observed in the transmission probability, and we propose possible strategies to optimize gate performances.

Topologically protected excitons in porphyrin thin films.

PubMed

Yuen-Zhou, Joel; Saikin, Semion K; Yao, Norman Y; Aspuru-Guzik, Alán

2014-11-01

The control of exciton transport in organic materials is of fundamental importance for the development of efficient light-harvesting systems. This transport is easily deteriorated by traps in the disordered energy landscape. Here, we propose and analyse a system that supports topological Frenkel exciton edge states. Backscattering of these chiral Frenkel excitons is prohibited by symmetry, ensuring that the transport properties of such a system are robust against disorder. To implement our idea, we propose a two-dimensional periodic array of tilted porphyrins interacting with a homogeneous magnetic field. This field serves to break time-reversal symmetry and results in lattice fluxes that mimic the Aharonov-Bohm phase acquired by electrons. Our proposal is the first blueprint for realizing topological phases of matter in molecular aggregates and suggests a paradigm for engineering novel excitonic materials.

Immunogenicity and therapeutic effects of recombinant Ag85AB fusion protein vaccines in mice infected with Mycobacterium tuberculosis.

PubMed

Liang, Yan; Zhang, Junxian; Yang, Yourong; Bai, Xuejuan; Yu, Qi; Li, Ning; Hou, Ying; Shi, Yingchang; Wang, Lan; Wu, Xueqiong

2017-07-13

The immune function of tuberculosis (TB) patients is disordered. By using immune regulators to assist chemotherapy for TB the curative effect might be improved. In this study, a vaccine containing Mycobacterium tuberculosis (M. tuberculosis) recombinant Ag85AB fusion protein (rAg85AB) was constructed and evaluated. The mice were immunized intramuscularly three times at two-week intervals with Ag85AB fusion protein combined with Corynebacterium parvum adjuvant (rAg85AB+CP). In comparison to control mice that received either CP alone or saline, the mice that received rAg85AB+CP had significantly higher number of T cells secreting IFN-γ and higher levels of specific antibodies of IgG, IgG1 and IgG2a isotypes in sera. The specific antibodies also had higher ratios of IgG2a to IgG1, indicating a predominant Th1 immune response. To test for immunotherapy of TB, M. tuberculosis infected mice were given three intramuscular doses of 20μg, 40μg or 60μg of rAg85AB in rAg85AB+CP, or phosphate-buffered saline (PBS), or CP or Mycobacterium phlei (M. Phlei) F.U.36. Compared with the PBS group, 20µg, 40µg and 60µg rAg85AB+CP and M. phlei F.U.36 groups reduced the pulmonary bacterial loads by 0.13, 0.15, 0.42 and 0.40 log 10 , and the liver bacterial loads by 0.64, 0.64, 0.53 and 0.61 log 10 , respectively. Pathological changes of lungs were less, and the lesions were limited to a certain extent in 40µg and 60µg rAg85AB+CP and M. phlei F.U.36 groups. These results showed that rAg85AB+CP had immunotherapeutic effect on TB, significantly increasing the cellular immune response, and inhibiting the growth of M. tuberculosis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Coherence recovery mechanisms of quantum Hall edge states

NASA Astrophysics Data System (ADS)

Goremykina, Anna S.; Sukhorukov, Eugene V.

2018-03-01

This paper is motivated by an unexpected observation in a recent experiment [S. Tewari et al., Phys. Rev. B 93, 035420 (2016)., 10.1103/PhysRevB.93.035420], where a robust coherence recovery, starting from a certain energy, was detected for an electron injected into a quantum Hall edge at a filling factor of 2. After passing through a quantum dot, the electron then tunnels into the edge with a subsequent propagation towards a symmetric Mach-Zender interferometer (MZI). Afterwards, the visibility of Aharonov-Bohm (AB) oscillations is measured. An earlier study, based on the bosonization framework with a linear spectrum of the edge excitations, predicted a decay of the visibility with increasing energy. We associate this result with the destructive interference of the two quasiparticles (charge and neutral modes), formed at the edge out of the incoming electron wave packet (WP). However, in reality, it might be suppressed due to an imbalance between the quasiparticles, for instance, in the presence of dispersion and/or dissipation. This idea could also be explored further experimentally by applying a periodic potential to the arms of the MZI and thus creating the imbalance. Yet another possibility to restore phase coherence, also based on dispersion and dissipation, accounts for a drop in the energy density of the electron WP by the time it arrives at the interferometer, leading to a significantly smaller dephasing inside it. We then show that the energy density is defined by a parameter completely independent of the injected energy, which naturally explains the emergence of threshold energy in the experiment.

[Effects of bkdAB interruption on avermectin biosynthesis].

PubMed

Zhu, Hao-Jun; Liang, Yun-Xiang; Zhou, Jun-Chu; Zheng, Ying-Hua

2004-03-01

In this study, Streptomyces avermitilis Bjbm0006 which produces four avermectin B components was used as an original test strain. A replacement plasmid containing a gene cluster bkdAB (branched-chain alpha-keto acid dehydrogenase gene) involved in the biosynthesis of avermectin B in S. avermitilis Bjbm0006 was constructed by means of PCR technique and then named as pHJ5821 (pHZ1358::bkdAB&erm). A recombinant strain Bjbm5821 was obtained after the gene cluster was interrupted by double crossover. This strain was tested in laboratory conditions and analysed by PCR using the total DNA as template. The HPLC analysis showed that the strain Bjbm5821 synthesized the same 'a' components Bla and B2a as the original strain did. However, It lost the ability for the production of 'b'components for example B1b and B2b. A novel compound was detected in fermentation products. The results of present study suggests that the production of gene cluster bkdAB may play a main role similar to alpha-ketoisovaleric acid dehydrogenase in the pathway of avermectin synthesis.

Asymmetric lasing at spectral singularities

NASA Astrophysics Data System (ADS)

Jin, L.

2018-03-01

Scattering coefficients can diverge at spectral singularities. In such situation, the stationary solution becomes a laser solution with outgoing waves only. We explore a parity-time (PT )-symmetric non-Hermitian two-arm Aharonov-Bohm interferometer consisting of three coupled resonators enclosing synthetic magnetic flux. The synthetic magnetic flux does not break the PT symmetry, which protects the symmetric transmission. The features and conditions of symmetric, asymmetric, and unidirectional lasing at spectral singularities are discussed. We elucidate that lasing affected by the interference is asymmetric; asymmetric lasing is induced by the interplay between the synthetic magnetic flux and the system's non-Hermiticity. The product of the left and right transmissions is equal to that of the reflections. Our findings reveal that the synthetic magnetic flux affects light propagation, and the results can be applied in the design of lasing devices.

Energy spectra of quantum rings.

PubMed

Fuhrer, A; Lüscher, S; Ihn, T; Heinzel, T; Ensslin, K; Wegscheider, W; Bichler, M

2001-10-25

Quantum mechanical experiments in ring geometries have long fascinated physicists. Open rings connected to leads, for example, allow the observation of the Aharonov-Bohm effect, one of the best examples of quantum mechanical phase coherence. The phase coherence of electrons travelling through a quantum dot embedded in one arm of an open ring has also been demonstrated. The energy spectra of closed rings have only recently been studied by optical spectroscopy. The prediction that they allow persistent current has been explored in various experiments. Here we report magnetotransport experiments on closed rings in the Coulomb blockade regime. Our experiments show that a microscopic understanding of energy levels, so far limited to few-electron quantum dots, can be extended to a many-electron system. A semiclassical interpretation of our results indicates that electron motion in the rings is governed by regular rather than chaotic motion, an unexplored regime in many-electron quantum dots. This opens a way to experiments where even more complex structures can be investigated at a quantum mechanical level.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dessotti, F. A.; Ricco, L. S.; Souza, M. de

As the Fano effect is an interference phenomenon where tunneling paths compete for the electronic transport, it becomes a probe to catch fingerprints of Majorana fermions lying on condensed matter systems. In this work, we benefit of this mechanism by proposing as a route for that an Aharonov-Bohm-like interferometer composed by two quantum dots, being one of them coupled to a Majorana bound state, which is attached to one of the edges of a semi-infinite Kitaev wire within the topological phase. By changing the Fermi energy of the leads and the symmetric detuning of the levels for the dots, wemore » show that opposing Fano regimes result in a transmittance characterized by distinct conducting and insulating regions, which are fingerprints of an isolated Majorana quasiparticle. Furthermore, we show that the maximum fluctuation of the transmittance as a function of the detuning is half for a semi-infinite wire, while it corresponds to the unity for a finite system. The setup proposed here constitutes an alternative experimental tool to detect Majorana excitations.« less

Investigation of polarization effects in the gramicidin A channel from ab initio molecular dynamics simulations.

PubMed

Timko, Jeff; Kuyucak, Serdar

2012-11-28

Polarization is an important component of molecular interactions and is expected to play a particularly significant role in inhomogeneous environments such as pores and interfaces. Here we investigate the effects of polarization in the gramicidin A ion channel by performing quantum mechanics/molecular mechanics molecular dynamics (MD) simulations and comparing the results with those obtained from classical MD simulations with non-polarizable force fields. We consider the dipole moments of backbone carbonyl groups and channel water molecules as well as a number of structural quantities of interest. The ab initio results show that the dipole moments of the carbonyl groups and water molecules are highly sensitive to the hydrogen bonds (H-bonds) they participate in. In the absence of a K(+) ion, water molecules in the channel are quite mobile, making the H-bond network highly dynamic. A central K(+) ion acts as an anchor for the channel waters, stabilizing the H-bond network and thereby increasing their average dipole moments. In contrast, the K(+) ion has little effect on the dipole moments of the neighboring carbonyl groups. The weakness of the ion-peptide interactions helps to explain the near diffusion-rate conductance of K(+) ions through the channel. We also address the sampling issue in relatively short ab initio MD simulations. Results obtained from a continuous 20 ps ab initio MD simulation are compared with those generated by sampling ten windows from a much longer classical MD simulation and running each window for 2 ps with ab initio MD. Both methods yield similar results for a number of quantities of interest, indicating that fluctuations are fast enough to justify the short ab initio MD simulations.

The Anti-(+)-Methamphetamine Monoclonal Antibody mAb7F9 Attenuates Acute (+)-Methamphetamine Effects on Intracranial Self-Stimulation in Rats

PubMed Central

Harris, Andrew C.; LeSage, Mark G.; Shelley, David; Perry, Jennifer L.; Pentel, Paul R.; Owens, S. Michael

2015-01-01

Passive immunization with monoclonal antibodies (mAbs) against (+)-methamphetamine (METH) is being evaluated for the treatment of METH addiction. A human/mouse chimeric form of the murine anti-METH mAb7F9 has entered clinical trials. This study examined the effects of murine mAb7F9 on certain addiction-related behavioral effects of METH in rats as measured using intracranial self-stimulation (ICSS). Initial studies indicated that acute METH (0.1-0.56 mg/kg, s.c.) lowered the minimal (threshold) stimulation intensity that maintained ICSS. METH (0.3 mg/kg, s.c.) also blocked elevations in ICSS thresholds (anhedonia-like behavior) during spontaneous withdrawal from a chronic METH infusion (10 mg/kg/day x 7 days). In studies examining effects of i.v. pretreatment with mAb7F9 (at 30, 100, or 200 mg/kg), 200 mg/kg blocked the ability of an initial injection of METH (0.3 mg/kg, s.c.) to reduce baseline ICSS thresholds, but was less capable of attenuating the effect of subsequent daily injections of METH. MAb7F9 (200 mg/kg) also produced a small but significant reduction in the ability of METH (0.3 mg/kg, s.c.) to reverse METH withdrawal-induced elevations in ICSS thresholds. These studies demonstrate that mAb7F9 can partially attenuate some addiction-related effects of acute METH in an ICSS model, and provide some support for the therapeutic potential of mAb7F9 for the treatment of METH addiction. PMID:25742165

Unambiguous Signature of the Berry Phase in Intense Laser Dissociation of Diatomic Molecules.

PubMed

Bouakline, Foudhil

2018-05-03

We report strong evidence of Berry phase effects in intense laser dissociation of D 2 + molecules, manifested as Aharonov-Bohm-like oscillations in the photofragment angular distribution (PAD). Our calculations show that this interference pattern strongly depends on the parity of the diatom initial rotational state, (-1) j . Indeed, the PAD local maxima (minima) observed in one case ( j odd) correspond to local minima (maxima) in the other case ( j even). Using simple topological arguments, we clearly show that such interference conversion is a direct signature of the Berry phase. The sole effect of the latter on the rovibrational wave function is a sign change of the relative phase between two interfering components, which wind in opposite senses around a light-induced conical intersection (LICI). Therefore, encirclement of the LICI leads to constructive ( j odd) or destructive ( j even) self-interference of the initial nuclear wavepacket in the dissociative limit. To corroborate our theoretical findings, we suggest an experiment of strong-field indirect dissociation of D 2 + molecules, comparing the PAD of the ortho and para molecular species in directions nearly perpendicular to the laser polarization axis.

Holism and structuralism in U(1) gauge theory

NASA Astrophysics Data System (ADS)

Lyre, Holger

After decades of neglect philosophers of physics have discovered gauge theories-arguably the paradigm of modern field physics-as a genuine topic for foundational and philosophical research. Incidentally, in the last couple of years interest from the philosophy of physics in structural realism-in the eyes of its proponents the best suited realist position towards modern physics-has also raised. This paper tries to connect both topics and aims to show that structural realism gains further credence from an ontological analysis of gauge theories-in particular U (1) gauge theory. In the first part of the paper the framework of fiber bundle gauge theories is briefly presented and the interpretation of local gauge symmetry will be examined. In the second part, an ontological underdetermination of gauge theories is carved out by considering the various kinds of non-locality involved in such typical effects as the Aharonov-Bohm effect. The analysis shows that the peculiar form of non-separability figuring in gauge theories is a variant of spatiotemporal holism and can be distinguished from quantum theoretic holism. In the last part of the paper the arguments for a gauge theoretic support of structural realism are laid out and discussed.

Adsorption of transgenic insecticidal Cry1Ab protein to silica particles. Effects on transport and bioactivity.

PubMed

Madliger, Michael; Gasser, Christoph A; Schwarzenbach, René P; Sander, Michael

2011-05-15

Bt crops are genetically modified to be resistant against insect pests by expressing insecticidal Cry proteins. The processes governing the fate and bioavailability of the expressed transgenic Cry proteins in soils are poorly understood. We studied adsorption of Cry1Ab to negatively charged silica (SiO(2)) particles, a major soil constituent and a model for negatively charged mineral surfaces, at pH 5 to 10 and ionic strengths I = 10 mM to 250 mM, both in solution depletion and saturated column transport experiments. Cry1Ab-SiO(2) interactions were dominated by patch-controlled electrostatic attraction (PCEA), as evident from increasing Cry1Ab attraction to SiO(2) with decreasing I at pH at which both Cry1Ab and SiO(2) were net negatively charged. Experimental and modeling evidence is provided that the surface heterogeneity of SiO(2) particles modulated PCEA, leading to a fraction of adsorption sites with slow Cry1Ab desorption kinetics. Desorption rates from these sites increased upon increasing the solution pH. In toxicity bioassays, we demonstrated that Cry1Ab retained insecticidal activity when adsorbed to SiO(2), suggesting high protein conformational stability during adsorption-desorption cycles. Models predicting Cry1A protein adsorption in soils therefore need to account for combined effects of the nonuniform protein surface charge distribution and of sorbent surface heterogeneity.

[Find your way in the jungle of mAbs].

PubMed

Watier, H

2017-09-01

The rapidly increasing number of approved monoclonal antibodies (mAbs) and the huge number of mAbs in clinical development are a matter of concern for who wants to easily identify targets, indications, mechanisms of action and possible adverse effects. The current nomenclature being of limited interest, simple rationales will be presented for helping practitioners in rapidly classify mAbs depending on their structure-pharmacology relationship and in evaluating their potential effects, particularly in transfusion medicine. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Effect analysis of material properties of picosecond laser ablation for ABS/PVC

NASA Astrophysics Data System (ADS)

Tsai, Y. H.; Ho, C. Y.; Chiou, Y. J.

2017-06-01

This paper analytically investigates the picosecond laser ablation of ABS/PVC. Laser-pulsed ablation is a wellestablished tool for polymer. However the ablation mechanism of laser processing for polymer has not been thoroughly understood yet. This study utilized a thermal transport model to analyze the relationship between the ablation rate and laser fluences. This model considered the energy balance at the decomposition interface and Arrhenius law as the ablation mechanisms. The calculated variation of the ablation rate with the logarithm of the laser fluence agrees with the measured data. It is also validated in this work that the variation of the ablation rate with the logarithm of the laser fluence obeys Beer's law for low laser fluences. The effects of material properties and processing parameters on the ablation depth per pulse are also discussed for picosecond laser processing of ABS/PVC.

In Vitro Study of Bacteriophage AB3 Endolysin LysAB3 Activity Against Acinetobacter baumannii Biofilm and Biofilm-Bound A. baumannii.

PubMed

Zhang, Jie; Xu, Lu-Lu; Gan, Dan; Zhang, Xingping

2018-06-01

The increase in the prevalence of drug-resistant Acinetobacter baumannii is a serious public health concern, which is closely linked to the formation of biofilm. It is reported that the bacteriophage and its endolysin have a good ability to degrade biofilms. The goals of this study were to compare the ability of A. baumannii bacteriophage AB3, its endolysin AB3, and three antibiotics to degrade A. baumannii biofilm and biofilm-bound A. baumannii and to understand the antibacterial mechanism of LysAB3. The 558-bp sequence of the LysAB3 gene was amplified by polymerase chain reaction (PCR); the fragment was cloned into pET28a (+) to construct the recombinant plasmid pET28a-LysAB3, which was then expressed in E. coli BL21 (DE3) to obtain the LysAB3. Differences in A. baumannii biofilm and biofilm-bound A. baumannii after treatment with bacteriophage AB3, LysAB3 or three antibiotics were examined using the crystal violet staining method and an MTT (3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide) assay. Changes in biofilm morphology and thickness in each treatment group were observed by laser scanning confocal microscopy. In addition, a LysAB3 construct with the amphiphilic peptide structural region removed (LysAB3-D) was assessed for its antibacterial activity. After 24-hour treatment with either bacteriophage AB3 and its LysAB3, A. baumannii biofilms were significantly degraded, and the number of viable biofilm-bound A. baumannii were also significantly decreased. After removing the amphiphilic peptide structure motif from LysAB3, the antibacterial activity decreased from 95.8% to 33.3%. Thus, LysAB3 can effectively degrade A. baumannii biofilm and biofilm-bound A. baumannii in vitro. The antibacterial mechanism of LysAB3 may be associated with the ability of the amphiphilic peptide structural region to enhance the permeability of cytoplasmic membrane of A. baumannii by degradation of bacterial wall peptidoglycan.

Introduction to the theory and application of a unified Bohm criterion for arbitrary-ion-temperature collision-free plasmas with finite Debye lengths

NASA Astrophysics Data System (ADS)

Kos, L.; Jelić, N.; Kuhn, S.; Tskhakaya, D. D.

2018-04-01

At present, identifying and characterizing the common plasma-sheath edge (PSE) in the conventional fluid approach leads to intrinsic oversimplifications, while the kinetic one results in unusable over-generalizations. In addition, none of these approaches can be justified in realistic plasmas, i.e., those which are characterized by non-negligible Debye lengths and a well-defined non-negligible ion temperature. In an attempt to resolve this problem, we propose a new formulation of the Bohm criterion [D. Bohm, The Characteristics of Electrical Discharges in Magnetic Fields (McGraw-Hill, New York, 1949)], which is here expressed in terms of fluid, kinetic, and electrostatic-pressure contributions. This "unified" Bohm criterion consists of a set of two equations for calculating the ion directional energy (i.e., the mean directional velocity) and the plasma potential at the common PSE, and is valid for arbitrary ion-to-electron temperature ratios. It turns out to be exact at any point of the quasi-neutral plasma provided that the ion differential polytropic coefficient function (DPCF) of Kuhn et al. [Phys. Plasmas 13, 013503 (2006)] is employed, with the advantage that the DPCF is an easily measurable fluid quantity. Moreover, our unified Bohm criterion holds in plasmas with finite Debye lengths, for which the famous kinetic criterion formulated by Harrison and Thompson [Proc. Phys. Soc. 74, 145 (1959)] fails. Unlike the kinetic criterion in the case of negligible Debye length, the kinetic contribution to the unified Bohm criterion, arising due to the presence of negative and zero velocities in the ion velocity distribution function, can be calculated separately from the fluid term. This kinetic contribution disappears identically at the PSE, yielding strict equality of the ion directional velocity there and the ion sound speed, provided that the latter is formulated in terms of the present definition of DPCFs. The numerical values of these velocities are found for the

Manipulating quantum coherence of charge states in interacting double-dot Aharonov–Bohm interferometers

NASA Astrophysics Data System (ADS)

Jin, Jinshuang; Wang, Shikuan; Zhou, Jiahuan; Zhang, Wei-Min; Yan, YiJing

2018-04-01

We investigate the dynamics of charge-state coherence in a degenerate double-dot Aharonov–Bohm interferometer with finite inter-dot Coulomb interactions. The quantum coherence of the charge states is found to be sensitive to the transport setup configurations, involving both the single-electron impurity channels and the Coulomb-assisted ones. We numerically demonstrate the emergence of a complete coherence between the two charge states, with the relative phase being continuously controllable through the magnetic flux. Interestingly, a fully coherent charge qubit arises at the double-dots electron pair tunneling resonance condition, where the chemical potential of one electrode is tuned at the center between a single-electron impurity channel and the related Coulomb-assisted channel. This pure quantum state of charge qubit could be experimentally realized at the current–voltage characteristic turnover position, where differential conductance sign changes. We further elaborate the underlying mechanism for both the real-time and the stationary charge-states coherence in the double-dot systems of study.

Distinguishing Majorana bound states from localized Andreev bound states by interferometry

NASA Astrophysics Data System (ADS)

Hell, Michael; Flensberg, Karsten; Leijnse, Martin

2018-04-01

Experimental evidence for Majorana bound states (MBSs) is so far mainly based on the robustness of a zero-bias conductance peak. However, similar features can also arise due to Andreev bound states (ABSs) localized at the end of an island. We show that these two scenarios can be distinguished by an interferometry experiment based on embedding a Coulomb-blockaded island into an Aharonov-Bohm ring. For two ABSs, when the ground state is nearly degenerate, cotunneling can change the state of the island, and interference is suppressed. By contrast, for two MBSs the ground state is nondegenerate, and cotunneling has to preserve the island state, which leads to h /e -periodic conductance oscillations with magnetic flux. Such interference setups can be realized with semiconducting nanowires or two-dimensional electron gases with proximity-induced superconductivity and may also be a useful spectroscopic tool for parity-flip mechanisms.

Joining the in vitro immunization of alpaca lymphocytes and phage display: rapid and cost effective pipeline for sdAb synthesis.

PubMed

Comor, Lubos; Dolinska, Saskia; Bhide, Katarina; Pulzova, Lucia; Jiménez-Munguía, Irene; Bencurova, Elena; Flachbartova, Zuzana; Potocnakova, Lenka; Kanova, Evelina; Bhide, Mangesh

2017-01-23

Camelids possess unique functional heavy chain antibodies, which can be produced and modified in vitro as a single domain antibody (sdAb or nanobody) with full antigen binding ability. Production of sdAb in conventional manner requires active immunization of Camelidae animal, which is laborious, time consuming, costly and in many cases not feasible (e.g. in case of highly toxic or infectious antigens). In this study, we describe an alternative pipeline that includes in vitro stimulation of naïve alpaca B-lymphocytes by antigen of interest (in this case endothelial cell binding domain of OspA of Borrelia) in the presence of recombinant alpaca interleukins 2 and 4, construction of sdAb phage library, selection of antigen specific sdAb expressed on phages (biopanning) and confirmation of binding ability of sdAb to the antigen. By joining the in vitro immunization and the phage display ten unique phage clones carrying sdAb were selected. Out of ten, seven sdAb showed strong antigen binding ability in phage ELISA. Furthermore, two soluble forms of sdAb were produced and their differential antigen binding affinity was measured with bio-layer interferometry. A proposed pipeline has potential to reduce the cost substantially required for maintenance of camelid herd for active immunization. Furthermore, in vitro immunization can be achieved within a week to enrich mRNA copies encoding antigen-specific sdAbs in B cell. This rapid and cost effective pipeline can help researchers to develop efficiently sdAb for diagnostic and therapeutic purposes.

[Kidney allotransplantation from the AB0-incompatible donors].

PubMed

Goriaĭnov, V A; Kaabak, M M; Babenko, N N; Shishlo, L A; Morozova, M M; Ragimov, A A; Dazhkova, N G; Salimov, E L

2013-01-01

The experience of 28 kidney allotransplantations from the AB0-incompatible donors was analyzed. The comparative group consisted of 38 patients, who received the AB0-compatible organ. The results were assessed using the following parameters: renal function, morphology of the biopsy samples of the transplanted kidney and actuary survival of the recipients with functioning transplants in both groups. The comparative analysis showed no significant difference between the two groups, giving the right to consider the kidney allotransplantation from the AB0-incompatible donors safe and effective.

Stacking stability of MoS2 bilayer: An ab initio study

NASA Astrophysics Data System (ADS)

Tao, Peng; Guo, Huai-Hong; Yang, Teng; Zhang, Zhi-Dong

2014-10-01

The study of the stacking stability of bilayer MoS2 is essential since a bilayer has exhibited advantages over single layer MoS2 in many aspects for nanoelectronic applications. We explored the relative stability, optimal sliding path between different stacking orders of bilayer MoS2, and (especially) the effect of inter-layer stress, by combining first-principles density functional total energy calculations and the climbing-image nudge-elastic-band (CI-NEB) method. Among five typical stacking orders, which can be categorized into two kinds (I: AA, AB and II: AA', AB', A'B), we found that stacking orders with Mo and S superposing from both layers, such as AA' and AB, is more stable than the others. With smaller computational efforts than potential energy profile searching, we can study the effect of inter-layer stress on the stacking stability. Under isobaric condition, the sliding barrier increases by a few eV/(ucGPa) from AA' to AB', compared to 0.1 eV/(ucGPa) from AB to [AB]. Moreover, we found that interlayer compressive stress can help enhance the transport properties of AA'. This study can help understand why inter-layer stress by dielectric gating materials can be an effective means to improving MoS2 on nanoelectronic applications.

On Entropy Production in the Madelung Fluid and the Role of Bohm's Potential in Classical Diffusion

NASA Astrophysics Data System (ADS)

Heifetz, Eyal; Tsekov, Roumen; Cohen, Eliahu; Nussinov, Zohar

2016-07-01

The Madelung equations map the non-relativistic time-dependent Schrödinger equation into hydrodynamic equations of a virtual fluid. While the von Neumann entropy remains constant, we demonstrate that an increase of the Shannon entropy, associated with this Madelung fluid, is proportional to the expectation value of its velocity divergence. Hence, the Shannon entropy may grow (or decrease) due to an expansion (or compression) of the Madelung fluid. These effects result from the interference between solutions of the Schrödinger equation. Growth of the Shannon entropy due to expansion is common in diffusive processes. However, in the latter the process is irreversible while the processes in the Madelung fluid are always reversible. The relations between interference, compressibility and variation of the Shannon entropy are then examined in several simple examples. Furthermore, we demonstrate that for classical diffusive processes, the "force" accelerating diffusion has the form of the positive gradient of the quantum Bohm potential. Expressing then the diffusion coefficient in terms of the Planck constant reveals the lower bound given by the Heisenberg uncertainty principle in terms of the product between the gas mean free path and the Brownian momentum.

Cooperative effects in spherical spasers: Ab initio analytical model

NASA Astrophysics Data System (ADS)

Bordo, V. G.

2017-06-01

A fully analytical semiclassical theory of cooperative optical processes which occur in an ensemble of molecules embedded in a spherical core-shell nanoparticle is developed from first principles. Both the plasmonic Dicke effect and spaser generation are investigated for the designs in which a shell/core contains an arbitrarily large number of active molecules in the vicinity of a metallic core/shell. An essential aspect of the theory is an ab initio account of the feedback from the core/shell boundaries which significantly modifies the molecular dynamics. The theory provides rigorous, albeit simple and physically transparent, criteria for both plasmonic superradiance and surface plasmon generation.

Effect of Fe2O3 and Binder on the Electrochemical Properties of Fe2O3/AB (Acetylene Black) Composite Electrodes

NASA Astrophysics Data System (ADS)

Anh, Trinh Tuan; Thuan, Vu Manh; Thang, Doan Ha; Hang, Bui Thi

2017-06-01

In an effort to find the best anode material for Fe/air batteries, a Fe2O3/AB (Acetylene Black) composite was prepared by dry-type ball milling using Fe2O3 nanoparticles and AB as the active and additive materials, respectively. The effects of various binders and Fe2O3 content on the electrochemical properties of Fe2O3/AB electrodes in alkaline solution were investigated. It was found that the content of Fe2O3 strongly affected the electrochemical behavior of Fe2O3/AB electrodes; with Fe2O3 nanopowder content reaching 70 wt.% for the electrode and showing improvement of the cyclability. When the electrode binder polytetrafluoroethylene (PTFE) was used, clear redox peaks were observed via cyclic voltammetry (CV), while polyvinylidene fluoride-containing electrodes provided CV curves with unobservable redox peaks. Increasing either binder content in the electrode showed a negative effect in terms of the cyclability of the Fe2O3/AB electrode.

Singularity and Bohm criterion in hot positive ion species in the electronegative ion sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aslaninejad, Morteza; Yasserian, Kiomars

2016-05-15

The structure of the discharge for a magnetized electronegative ion source with two species of positive ions is investigated. The thermal motion of hot positive ions and the singularities involved with it are taken into account. By analytical solution of the neutral region, the location of the singular point and also the values of the plasma parameter such as electric potential and ion density at the singular point are obtained. A generalized Bohm criterion is recovered and discussed. In addition, for the non-neutral solution, the numerical method is used. In contrast with cold ion plasma, qualitative changes are observed. Themore » parameter space region within which oscillations in the density and potential can be observed has been scanned and discussed. The space charge behavior in the vicinity of edge of the ion sources has also been discussed in detail.« less

Correlating the Effects of Antimicrobial Preservatives on Conformational Stability, Aggregation Propensity, and Backbone Flexibility of an IgG1 mAb.

PubMed

Arora, Jayant; Joshi, Sangeeta B; Middaugh, C Russell; Weis, David D; Volkin, David B

2017-06-01

Multidose formulations of biotherapeutics, which offer better dosage management and reduced production costs, require the addition of antimicrobial preservatives (APs). APs have been shown, however, to decrease protein stability in solution and cause protein aggregation. In this report, the effect of 4 APs, m-cresol, phenol, phenoxyethanol, and benzyl alcohol on conformational stability, aggregation propensity, and backbone flexibility of an IgG1 mAb, mAb-4, is investigated. Compared with no preservative control, each of the APs decreased the conformational stability of mAb-4 as measured by differential scanning calorimetry and extrinsic fluorescence spectroscopy. The addition of APs resulted in increased monomer loss and aggregate accumulation at 50°C over 28 days, as monitored by size-exclusion chromatography. The extent of conformational destabilization and protein aggregation of mAb-4 induced by APs followed their calculated octanol-water partition coefficients. Increases in backbone flexibility, as measured by hydrogen exchange, of a region located in the C H 2 domain of the mAb (heavy chain 237-254) in the presence of APs also correlated with hydrophobicity. Based on these results, the destabilizing effect of APs on mAb-4 correlates with the increased hydrophobicity of the APs and their ability to enhance the local backbone flexibility of an aggregation hot spot within the C H 2 domain of the mAb. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

The AB Doradus system revisited: The dynamical mass of AB Dor A/C

NASA Astrophysics Data System (ADS)

Azulay, R.; Guirado, J. C.; Marcaide, J. M.; Martí-Vidal, I.; Ros, E.; Tognelli, E.; Jauncey, D. L.; Lestrade, J.-F.; Reynolds, J. E.

2017-10-01

Context. The study of pre-main-sequence (PMS) stars with model-independent measurements of their masses is essential to check the validity of theoretical models of stellar evolution. The well-known PMS binary AB Dor A/C is an important benchmark for this task, since it displays intense and compact radio emission, which makes possible the application of high-precision astrometric techniques to this system. Aims: We aim to revisit the dynamical masses of the components of AB Dor A/C to refine earlier comparisons between the measurements of stellar parameters and the predictions of stellar models. Methods: We observed in phase-reference mode the binary AB Dor A/C, 0.2'' separation, with the Australian Long Baseline Array at 8.4 GHz. The astrometric information resulting from our observations was analyzed along with previously reported VLBI, optical (Hipparcos), and infrared measurements. Results: The main star AB Dor A is clearly detected in all the VLBI observations, which allowed us to analyze the orbital motion of the system and to obtain model-independent dynamical masses of 0.90 ± 0.08 M⊙ and 0.090 ± 0.008 M⊙, for AB Dor A and AB Dor C, respectively. Comparisons with PMS stellar evolution models favor and age of 40-50 Myr for AB Dor A and of 25-120 Myr for AB Dor C. Conclusions: We show that the orbital motion of the AB Dor A/C system is remarkably well determined, leading to precise estimates of the dynamical masses. Comparison of our results with the prediction of evolutionary models support the observational evidence that theoretical models tend to slightly underestimate the mass of the low-mass stars.

Comparison of In Vitro Activity of Liposomal Nystatin against Aspergillus Species with Those of Nystatin, Amphotericin B (AB) Deoxycholate, AB Colloidal Dispersion, Liposomal AB, AB Lipid Complex, and Itraconazole

PubMed Central

Oakley, Karen L.; Moore, Caroline B.; Denning, David W.

1999-01-01

We compared the in vitro activity of liposomal nystatin (Nyotran) with those of other antifungal agents against 60 Aspergillus isolates. Twelve isolates were itraconazole resistant. For all isolates, geometric mean (GM) MICs (micrograms per milliliter) were 2.30 for liposomal nystatin, 0.58 for itraconazole, 0.86 for amphotericin B (AB) deoxycholate, 9.51 for nystatin, 2.07 for liposomal AB, 2.57 for AB lipid complex, and 0.86 for AB colloidal dispersion. Aspergillus terreus (GM, 8.72 μg/ml; range, 8 to 16 μg/ml) was significantly less susceptible to all of the polyene drugs than all other species (P = 0.0001). PMID:10223948

Hemostatic effect of a monoclonal antibody mAb 2021 blocking the interaction between FXa and TFPI in a rabbit hemophilia model.

PubMed

Hilden, Ida; Lauritzen, Brian; Sørensen, Brit Binow; Clausen, Jes Thorn; Jespersgaard, Christina; Krogh, Berit Olsen; Bowler, Andrew Neil; Breinholt, Jens; Gruhler, Albrecht; Svensson, L Anders; Petersen, Helle Heibroch; Petersen, Lars Christian; Balling, Kristoffer W; Hansen, Lene; Hermit, Mette Brunsgaard; Egebjerg, Thomas; Friederichsen, Birgitte; Ezban, Mirella; Bjørn, Søren Erik

2012-06-14

Hemophilia is treated by IV replacement therapy with Factor VIII (FVIII) or Factor IX (FIX), either on demand to resolve bleeding, or as prophylaxis. Improved treatment may be provided by drugs designed for subcutaneous and less frequent administration with a reduced risk of inhibitor formation. Tissue factor pathway inhibitor (TFPI) down-regulates the initiation of coagulation by inhibition of Factor VIIa (FVIIa)/tissue factor/Factor Xa (FVIIa/TF/FXa). Blockage of TFPI inhibition may facilitate thrombin generation in a hemophilic setting. A high-affinity (K(D) = 25pM) mAb, mAb 2021, against TFPI was investigated. Binding of mAb 2021 to TFPI effectively prevented inhibition of FVIIa/TF/FXa and improved clot formation in hemophilia blood and plasma. The binding epitope on the Kunitz-type protease inhibitor domain 2 of TFPI was mapped by crystallography, and showed an extensive overlap with the FXa contact region highlighting a structural basis for its mechanism of action. In a rabbit hemophilia model, an intravenous or subcutaneous dose significantly reduced cuticle bleeding. mAb 2021 showed an effect comparable with that of rFVIIa. Cuticle bleeding in the model was reduced for at least 7 days by a single intravenous dose of mAb 2021. This study suggests that neutralization of TFPI by mAb 2021 may constitute a novel treatment option in hemophilia.

Ab initio molecular dynamics with nuclear quantum effects at classical cost: Ring polymer contraction for density functional theory.

PubMed

Marsalek, Ondrej; Markland, Thomas E

2016-02-07

Path integral molecular dynamics simulations, combined with an ab initio evaluation of interactions using electronic structure theory, incorporate the quantum mechanical nature of both the electrons and nuclei, which are essential to accurately describe systems containing light nuclei. However, path integral simulations have traditionally required a computational cost around two orders of magnitude greater than treating the nuclei classically, making them prohibitively costly for most applications. Here we show that the cost of path integral simulations can be dramatically reduced by extending our ring polymer contraction approach to ab initio molecular dynamics simulations. By using density functional tight binding as a reference system, we show that our ring polymer contraction scheme gives rapid and systematic convergence to the full path integral density functional theory result. We demonstrate the efficiency of this approach in ab initio simulations of liquid water and the reactive protonated and deprotonated water dimer systems. We find that the vast majority of the nuclear quantum effects are accurately captured using contraction to just the ring polymer centroid, which requires the same number of density functional theory calculations as a classical simulation. Combined with a multiple time step scheme using the same reference system, which allows the time step to be increased, this approach is as fast as a typical classical ab initio molecular dynamics simulation and 35× faster than a full path integral calculation, while still exactly including the quantum sampling of nuclei. This development thus offers a route to routinely include nuclear quantum effects in ab initio molecular dynamics simulations at negligible computational cost.

Two-dimensional quantum ring in a graphene layer in the presence of a Aharonov–Bohm flux

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amaro Neto, José; Bueno, M.J.; Furtado, Claudio, E-mail: furtado@fisica.ufpb.br

2016-10-15

In this paper we study the relativistic quantum dynamics of a massless fermion confined in a quantum ring. We use a model of confining potential and introduce the interaction via Dirac oscillator coupling, which provides ring confinement for massless Dirac fermions. The energy levels and corresponding eigenfunctions for this model in graphene layer in the presence of Aharonov–Bohm flux in the centre of the ring and the expression for persistent current in this model are derived. We also investigate the model for quantum ring in graphene layer in the presence of a disclination and a magnetic flux. The energy spectrummore » and wave function are obtained exactly for this case. We see that the persistent current depends on parameters characterizing the topological defect.« less

Efficient creation of electron vortex beams for high resolution STEM imaging.

PubMed

Béché, A; Juchtmans, R; Verbeeck, J

2017-07-01

The recent discovery of electron vortex beams carrying quantised angular momentum in the TEM has led to an active field of research, exploring a variety of potential applications including the possibility of mapping magnetic states at the atomic scale. A prerequisite for this is the availability of atomic sized electron vortex beams at high beam current and mode purity. In this paper we present recent progress showing that by making use of the Aharonov-Bohm effect near the tip of a long single domain ferromagnetic Nickel needle, a very efficient aperture for the production of electron vortex beams can be realised. The aperture transmits more than 99% of all electrons and provides a vortex mode purity of up to 92%. Placing this aperture in the condenser plane of a state of the art Cs corrected microscope allows us to demonstrate atomic resolution HAADF STEM images with spatial resolution better than 1 Angström, in agreement with theoretical expectations and only slightly inferior to the performance of a non-vortex probe on the same instrument. Copyright © 2016 Elsevier B.V. All rights reserved.

Radiation and matter: Electrodynamics postulates and Lorenz gauge

NASA Astrophysics Data System (ADS)

Bobrov, V. B.; Trigger, S. A.; van Heijst, G. J.; Schram, P. P.

2016-11-01

In general terms, we have considered matter as the system of charged particles and quantized electromagnetic field. For consistent description of the thermodynamic properties of matter, especially in an extreme state, the problem of quantization of the longitudinal and scalar potentials should be solved. In this connection, we pay attention that the traditional postulates of electrodynamics, which claim that only electric and magnetic fields are observable, is resolved by denial of the statement about validity of the Maxwell equations for microscopic fields. The Maxwell equations, as the generalization of experimental data, are valid only for averaged values. We show that microscopic electrodynamics may be based on postulation of the d'Alembert equations for four-vector of the electromagnetic field potential. The Lorenz gauge is valid for the averages potentials (and provides the implementation of the Maxwell equations for averages). The suggested concept overcomes difficulties under the electromagnetic field quantization procedure being in accordance with the results of quantum electrodynamics. As a result, longitudinal and scalar photons become real rather than virtual and may be observed in principle. The longitudinal and scalar photons provide not only the Coulomb interaction of charged particles, but also allow the electrical Aharonov-Bohm effect.

Generalized Maxwell equations and charge conservation censorship

NASA Astrophysics Data System (ADS)

Modanese, G.

2017-02-01

The Aharonov-Bohm electrodynamics is a generalization of Maxwell theory with reduced gauge invariance. It allows to couple the electromagnetic field to a charge which is not locally conserved, and has an additional degree of freedom, the scalar field S = ∂αAα, usually interpreted as a longitudinal wave component. By reformulating the theory in a compact Lagrangian formalism, we are able to eliminate S explicitly from the dynamics and we obtain generalized Maxwell equation with interesting properties: they give ∂μFμν as the (conserved) sum of the (possibly non-conserved) physical current density jν, and a “secondary” current density iν which is a nonlocal function of jν. This implies that any non-conservation of jν is effectively “censored” by the observable field Fμν, and yet it may have real physical consequences. We give examples of stationary solutions which display these properties. Possible applications are to systems where local charge conservation is violated due to anomalies of the Adler-Bell-Jackiw (ABJ) kind or to macroscopic quantum tunnelling with currents which do not satisfy a local continuity equation.

Imaging snake orbits at graphene n -p junctions

NASA Astrophysics Data System (ADS)

Kolasiński, K.; Mreńca-Kolasińska, A.; Szafran, B.

2017-01-01

We consider conductance mapping of the snake orbits confined along the n -p junction defined in graphene by the electrostatic doping in the quantum Hall regime. We explain the periodicity of conductance oscillations at the magnetic field and the Fermi energy scales by the properties of the n -p junction as a conducting channel. We evaluate the conductance maps for a floating gate scanning the surface of the device. In the quantum Hall conditions the currents flow near the edges of the sample and along the n -p junction. The conductance mapping resolves only the n -p junction and not the edges. The conductance oscillations along the junction are found in the maps with periodicity related to the cyclotron orbits of the scattering current. Stronger probe potentials provide support to localized resonances at one of the sides of the junction with current loops that interfere with the n -p junction currents. The interference results in a series of narrow lines parallel to the junction with positions that strongly depend on the magnetic field through the Aharonov-Bohm effect. The consequences of a limited transparency of finite-width n -p junctions are also discussed.

Diode laser surgery. Ab interno and ab externo versus conventional surgery in rabbits.

PubMed

Karp, C L; Higginbotham, E J; Edward, D P; Musch, D C

1993-10-01

Fibroblastic proliferation of subconjunctival tissues remains a primary mechanism of failure in filtration surgery. Minimizing the surgical manipulation of episcleral tissues may reduce scarring. Laser sclerostomy surgery involves minimal tissue dissection, and is gaining attention as a method of potentially improving filter duration in high-risk cases. Twenty-five New Zealand rabbits underwent filtration surgery in one eye, and the fellow eye remained as the unoperated control. Ten rabbits underwent ab externo diode laser sclerostomy surgery, ten underwent ab interno diode sclerostomy surgery, and five had posterior sclerostomy procedures. Filtration failure was defined as a less-than-4-mmHg intraocular pressure (IOP) difference between the operative and control eyes. The mean time to failure for the ab externo, ab interno, and conventional posterior sclerostomy techniques measured 17.4 +/- 11.5, 13.1 +/- 6.7, and 6.0 +/- 3.1 days, respectively. In a comparison of the laser-treated groups with the conventional procedure, the time to failure was significantly longer (P = 0.02) for the ab externo filter. The mean ab interno sclerostomy duration was longer than the posterior lip procedure, but this difference was not statistically significant (P = 0.15). The overall level of IOP reduction was similar in the three groups. These data suggest that diode laser sclerostomy is a feasible technique in rabbits, and the ab externo approach resulted in longer filter duration than the conventional posterior lip procedure in this model.

Anti-GD2 mAbs and next-generation mAb-based agents for cancer therapy

PubMed Central

Perez Horta, Zulmarie; Goldberg, Jacob L; Sondel, Paul M

2016-01-01

Tumor-specific monoclonal antibodies (mAbs) have demonstrated efficacy in the clinic, becoming an important approach for cancer immunotherapy. Due to its limited expression on normal tissue, the GD2 disialogangloside expressed on neuroblastoma cells is an excellent candidate for mAb therapy. In 2015, dinutuximab (an anti-GD2 mAb) was approved by the US FDA and is currently used in a combination immunotherapeutic regimen for the treatment of children with high-risk neuroblastoma. Here, we review the extensive preclinical and clinical development of anti-GD2 mAbs and the different mechanisms by which they mediate tumor cell killing. In addition, we discuss different mAb-based strategies that capitalize on the targeting ability of anti-GD2 mAbs to potentially deliver, as monotherapy, or in combination with other treatments, improved antitumor efficacy. PMID:27485082

Masses and activity of AB Doradus B a/b. The age of the AB Dor quadruple system revisited

NASA Astrophysics Data System (ADS)

Wolter, U.; Czesla, S.; Fuhrmeister, B.; Robrade, J.; Engels, D.; Wieringa, M.; Schmitt, J. H. M. M.

2014-10-01

We present a multiwavelength study of the close binary AB Dor Ba/b (Rst137B). Our study comprises astrometric orbit measurements, optical spectroscopy, X-ray and radio observations. Using all available adaptive optics images of AB Dor B taken with VLT/NACO from 2004 to 2009, we tightly constrain its orbital period to 360.6 ± 1.5 days. We present the first orbital solution of Rst 137B and estimate the combined mass of AB Dor Ba+b as 0.69+0.02-0.24 M⊙, slightly exceeding previous estimates based on IR photometry. Our determined orbital inclination of Rst 137B is close to the axial inclination of AB Dor A inferred from Doppler imaging. Our VLT/UVES spectra yield high rotational velocities of ≥30 km s-1 for both components Ba and Bb, in accord with previous measurements, which corresponds to rotation periods significantly shorter than one day. Our combined spectral model, using PHOENIX spectra, yields an effective temperature of 3310 ± 50 K for the primary and approximately 60 K less for the secondary. The optical spectra presumably cover a chromospheric flare and show that at least one component of Rst 137B is significantly active. Activity and weak variations are also found in our simultaneous XMM-Newton observations, while our ATCA radio data yield constant fluxes at the level of previous measurements. Using evolutionary models, our newly determined stellar parameters confirm that the age of Rst 137B is between 50 and 100 Myr. Based on observations collected at the European Southern Observatory, Paranal, Chile, 383.D-1002(A) and the ESO Science Archive Facility. Using data obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member states and NASA. Using data obtained with the Australia Telescope Compact Array (ATCA) operated by the Commonwealth Scientific and Industrial Research Organisation (CSIRO).

Ab initio molecular dynamics with nuclear quantum effects at classical cost: Ring polymer contraction for density functional theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marsalek, Ondrej; Markland, Thomas E., E-mail: tmarkland@stanford.edu

Path integral molecular dynamics simulations, combined with an ab initio evaluation of interactions using electronic structure theory, incorporate the quantum mechanical nature of both the electrons and nuclei, which are essential to accurately describe systems containing light nuclei. However, path integral simulations have traditionally required a computational cost around two orders of magnitude greater than treating the nuclei classically, making them prohibitively costly for most applications. Here we show that the cost of path integral simulations can be dramatically reduced by extending our ring polymer contraction approach to ab initio molecular dynamics simulations. By using density functional tight binding asmore » a reference system, we show that our ring polymer contraction scheme gives rapid and systematic convergence to the full path integral density functional theory result. We demonstrate the efficiency of this approach in ab initio simulations of liquid water and the reactive protonated and deprotonated water dimer systems. We find that the vast majority of the nuclear quantum effects are accurately captured using contraction to just the ring polymer centroid, which requires the same number of density functional theory calculations as a classical simulation. Combined with a multiple time step scheme using the same reference system, which allows the time step to be increased, this approach is as fast as a typical classical ab initio molecular dynamics simulation and 35× faster than a full path integral calculation, while still exactly including the quantum sampling of nuclei. This development thus offers a route to routinely include nuclear quantum effects in ab initio molecular dynamics simulations at negligible computational cost.« less

Predicting the F(ab)-mediated effect of monoclonal antibodies in vivo by combining cell-level kinetic and pharmacokinetic modelling.

PubMed

Krippendorff, Ben-Fillippo; Oyarzún, Diego A; Huisinga, Wilhelm

2012-04-01

Cell-level kinetic models for therapeutically relevant processes increasingly benefit the early stages of drug development. Later stages of the drug development processes, however, rely on pharmacokinetic compartment models while cell-level dynamics are typically neglected. We here present a systematic approach to integrate cell-level kinetic models and pharmacokinetic compartment models. Incorporating target dynamics into pharmacokinetic models is especially useful for the development of therapeutic antibodies because their effect and pharmacokinetics are inherently interdependent. The approach is illustrated by analysing the F(ab)-mediated inhibitory effect of therapeutic antibodies targeting the epidermal growth factor receptor. We build a multi-level model for anti-EGFR antibodies by combining a systems biology model with in vitro determined parameters and a pharmacokinetic model based on in vivo pharmacokinetic data. Using this model, we investigated in silico the impact of biochemical properties of anti-EGFR antibodies on their F(ab)-mediated inhibitory effect. The multi-level model suggests that the F(ab)-mediated inhibitory effect saturates with increasing drug-receptor affinity, thereby limiting the impact of increasing antibody affinity on improving the effect. This indicates that observed differences in the therapeutic effects of high affinity antibodies in the market and in clinical development may result mainly from Fc-mediated indirect mechanisms such as antibody-dependent cell cytotoxicity.

The effects of a single intravenous injection of novel activin A/BMP-2 (AB204) on toxicity and the respiratory and central nervous systems

PubMed Central

Yoon, Byung-Hak; Lee, Jae Hyup; Na, Kyuheum; Ahn, Chihoon; Cho, Jongho; Ahn, Hyun Chan; Choi, Jungyoun; Oh, Hyosun; Kim, Byong Moon; Choe, Senyon

2018-01-01

The purpose of this study was to determine the effects of a single intravenous injection of a novel osteoinductive material, activin A/BMP-2 (AB204), to rodents on toxicity and their respiratory functions and central nervous system (CNS). A single intravenous injection of AB204 was given to Sprague–Dawley (SD) rats in doses of 0, 0.625, 2.5 and 10 mg/kg to observe the mortality rate, the general symptoms for 14 days. The experimental groups were also given 0.2, 0.4 and 0.8 mg/kg of AB204, respectively, and the respiration rate, the tidal volume and the minute volume were measured for 240 min. The experimental groups of imprinting control region (ICR) mice were given a single intravenous injection of 0.2, 0.4 and 0.8 mg/kg of AB204, respectively. Their body temperature was taken and general behaviors were observed to evaluate the effect of AB204 on the CNS for 240 min. The study on toxicity of a single intravenous injection found no death or abnormal symptoms, abnormal findings from autopsy, or abnormal body weight gain or loss in all the experimental groups. No abnormal variation associated with the test substance was observed in the respiration rate, the tidal volume, the minute volume, body temperature or the general behaviors. On the basis of these results, the approximate lethal dose of AB204 for a single intravenous injection exceeds 10 mg/kg for SD rats and a single intravenous injection of ≤0.8 mg/kg AB204 has no effect on their respiratory system for SD rat and no effect on their CNS for ICR mice. PMID:26446865

The effects of a single intravenous injection of novel activin A/BMP-2 (AB204) on toxicity and the respiratory and central nervous systems.

PubMed

Yoon, Byung-Hak; Lee, Jae Hyup; Na, Kyuheum; Ahn, Chihoon; Cho, Jongho; Ahn, Hyun Chan; Choi, Jungyoun; Oh, Hyosun; Kim, Byong Moon; Choe, Senyon

2016-01-01

The purpose of this study was to determine the effects of a single intravenous injection of a novel osteoinductive material, activin A/BMP-2 (AB204), to rodents on toxicity and their respiratory functions and central nervous system (CNS). A single intravenous injection of AB204 was given to Sprague-Dawley (SD) rats in doses of 0, 0.625, 2.5 and 10 mg/kg to observe the mortality rate, the general symptoms for 14 days. The experimental groups were also given 0.2, 0.4 and 0.8 mg/kg of AB204, respectively, and the respiration rate, the tidal volume and the minute volume were measured for 240 min. The experimental groups of imprinting control region (ICR) mice were given a single intravenous injection of 0.2, 0.4 and 0.8 mg/kg of AB204, respectively. Their body temperature was taken and general behaviors were observed to evaluate the effect of AB204 on the CNS for 240 min. The study on toxicity of a single intravenous injection found no death or abnormal symptoms, abnormal findings from autopsy, or abnormal body weight gain or loss in all the experimental groups. No abnormal variation associated with the test substance was observed in the respiration rate, the tidal volume, the minute volume, body temperature or the general behaviors. On the basis of these results, the approximate lethal dose of AB204 for a single intravenous injection exceeds 10 mg/kg for SD rats and a single intravenous injection of ≤0.8 mg/kg AB204 has no effect on their respiratory system for SD rat and no effect on their CNS for ICR mice.

Symmetry-Resolved Entanglement in Many-Body Systems.

PubMed

Goldstein, Moshe; Sela, Eran

2018-05-18

Similarly to the system Hamiltonian, a subsystem's reduced density matrix is composed of blocks characterized by symmetry quantum numbers (charge sectors). We present a geometric approach for extracting the contribution of individual charge sectors to the subsystem's entanglement measures within the replica trick method, via threading appropriate conjugate Aharonov-Bohm fluxes through a multisheet Riemann surface. Specializing to the case of 1+1D conformal field theory, we obtain general exact results for the entanglement entropies and spectrum, and apply them to a variety of systems, ranging from free and interacting fermions to spin and parafermion chains, and verify them numerically. We find that the total entanglement entropy, which scales as lnL, is composed of sqrt[lnL] contributions of individual subsystem charge sectors for interacting fermion chains, or even O(L^{0}) contributions when total spin conservation is also accounted for. We also explain how measurements of the contribution to the entanglement from separate charge sectors can be performed experimentally with existing techniques.

Localized end states in density modulated quantum wires and rings.

PubMed

Gangadharaiah, Suhas; Trifunovic, Luka; Loss, Daniel

2012-03-30

We study finite quantum wires and rings in the presence of a charge-density wave gap induced by a periodic modulation of the chemical potential. We show that the Tamm-Shockley bound states emerging at the ends of the wire are stable against weak disorder and interactions, for discrete open chains and for continuum systems. The low-energy physics can be mapped onto the Jackiw-Rebbi equations describing massive Dirac fermions and bound end states. We treat interactions via the continuum model and show that they increase the charge gap and further localize the end states. The electrons placed in the two localized states on the opposite ends of the wire can interact via exchange interactions and this setup can be used as a double quantum dot hosting spin qubits. The existence of these states could be experimentally detected through the presence of an unusual 4π Aharonov-Bohm periodicity in the spectrum and persistent current as a function of the external flux.

Symmetry-Resolved Entanglement in Many-Body Systems

NASA Astrophysics Data System (ADS)

Goldstein, Moshe; Sela, Eran

2018-05-01

Similarly to the system Hamiltonian, a subsystem's reduced density matrix is composed of blocks characterized by symmetry quantum numbers (charge sectors). We present a geometric approach for extracting the contribution of individual charge sectors to the subsystem's entanglement measures within the replica trick method, via threading appropriate conjugate Aharonov-Bohm fluxes through a multisheet Riemann surface. Specializing to the case of 1 +1 D conformal field theory, we obtain general exact results for the entanglement entropies and spectrum, and apply them to a variety of systems, ranging from free and interacting fermions to spin and parafermion chains, and verify them numerically. We find that the total entanglement entropy, which scales as ln L , is composed of √{ln L } contributions of individual subsystem charge sectors for interacting fermion chains, or even O (L0) contributions when total spin conservation is also accounted for. We also explain how measurements of the contribution to the entanglement from separate charge sectors can be performed experimentally with existing techniques.

General Rule of Negative Effective Ueff System & Materials Design of High-Tc Superconductors by ab initio Calculations

NASA Astrophysics Data System (ADS)

Katayama-Yoshida, Hiroshi; Nakanishi, Akitaka; Uede, Hiroki; Takawashi, Yuki; Fukushima, Tetsuya; Sato, Kazunori

2014-03-01

Based upon ab initio electronic structure calculation, I will discuss the general rule of negative effective U system by (1) exchange-correlation-induced negative effective U caused by the stability of the exchange-correlation energy in Hund's rule with high-spin ground states of d5 configuration, and (2) charge-excitation-induced negative effective U caused by the stability of chemical bond in the closed-shell of s2, p6, and d10 configurations. I will show the calculated results of negative effective U systems such as hole-doped CuAlO2 and CuFeS2. Based on the total energy calculations of antiferromagnetic and ferromagnetic states, I will discuss the magnetic phase diagram and superconductivity upon hole doping. I also discuss the computational materials design method of high-Tc superconductors by ab initio calculation to go beyond LDA and multi-scale simulations.

Unexpected effects of gene deletion on mercury interactions with the methylation-deficient mutant hgcAB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Hui; Hurt, Jr., Richard Ashley; Johs, Alexander

2014-01-01

The hgcA and hgcB gene pair is essential for mercury (Hg) methylation by certain anaerobic bacteria,1 but little is known about how deletion of hgcAB affects cell surface interactions and intracellular uptake of Hg. Here, we compare hgcAB mutants with the wild-type (WT) strains of both Geobacter sulfurreducens PCA and Desulfovibrio desulfuricans ND132 and observe differences in Hg redox transformations, adsorption, and uptake in laboratory incubation studies. In both strains, deletion of hgcAB increased the reduction of Hg(II) but decreased the oxidation of Hg(0) under anaerobic conditions. The measured cellular thiol content in hgcAB mutants was lower than the WT,more » accounting for decreased adsorption and uptake of Hg. Despite the lack of methylation activity, Hg uptake by the hgcAB continued, albeit at a slower rate than the WT. These findings demonstrate that deletion of the hgcAB gene not only eliminates Hg methylation but also alters cell physiology, resulting in changes to Hg redox reactions, sorption, and uptake by cells.« less

Quantum wavepacket ab initio molecular dynamics: an approach for computing dynamically averaged vibrational spectra including critical nuclear quantum effects.

PubMed

Sumner, Isaiah; Iyengar, Srinivasan S

2007-10-18

We have introduced a computational methodology to study vibrational spectroscopy in clusters inclusive of critical nuclear quantum effects. This approach is based on the recently developed quantum wavepacket ab initio molecular dynamics method that combines quantum wavepacket dynamics with ab initio molecular dynamics. The computational efficiency of the dynamical procedure is drastically improved (by several orders of magnitude) through the utilization of wavelet-based techniques combined with the previously introduced time-dependent deterministic sampling procedure measure to achieve stable, picosecond length, quantum-classical dynamics of electrons and nuclei in clusters. The dynamical information is employed to construct a novel cumulative flux/velocity correlation function, where the wavepacket flux from the quantized particle is combined with classical nuclear velocities to obtain the vibrational density of states. The approach is demonstrated by computing the vibrational density of states of [Cl-H-Cl]-, inclusive of critical quantum nuclear effects, and our results are in good agreement with experiment. A general hierarchical procedure is also provided, based on electronic structure harmonic frequencies, classical ab initio molecular dynamics, computation of nuclear quantum-mechanical eigenstates, and employing quantum wavepacket ab initio dynamics to understand vibrational spectroscopy in hydrogen-bonded clusters that display large degrees of anharmonicities.

Quantum detectors of vector potential and their modeling

NASA Astrophysics Data System (ADS)

Gulian, Armen; Melkonyan, Gurgen; Gulian, Ellen

Proportionality of current to vector potential is a feature not allowed in classical physics, but is one of the pillars in quantum theory. For superconductors, in particular, it allows us to describe the Meissner effect. Since the phase of the quantum wave function couples with the vector-potential, the related expressions are gauge-invariant. Is it possible to measure this gauge-invariant quantity locally? The answer is definitely ``yes'', as soon as the current is involved. Indeed, the electric current generates a magnetic field which can be measured straightforwardly. However, one can consider situations like the Aharonov-Bohm effect where the classical magnetic field is locally absent in the area occupied by the quantum object (i.e., superconductor in our case). Despite the local absence of the magnetic field, current is, nevertheless, building up. From what source is it acquiring its energy? Locally, only a vector potential is present. Is the current formation a result of a truly non-local quantum action, or does the local action of the vector potential have experimental consequences on the quantum system, which then can be considered as a detector of the vector potential? We discuss possible experimental schemes on the level of COMSOL modeling. This research is supported in part by the ONR Grant N000141612269.

Effect of exchange correlation potential on dispersion properties of lower hybrid wave in degenerate plasma

NASA Astrophysics Data System (ADS)

Rimza, Tripti; Sharma, Prerana

2017-05-01

The dispersion properties of lower hybrid wave are studied in electron-iondegenerate plasma with exchange effect in non-relativistic regime. It is found that the combined effect of Bohm potential and exchange correlation potential significantly modifies the dispersion properties of lower hybrid wave. The graphical results explicitly show the influence of degeneracy pressure, Bohm force and exchange correlation potential on the frequency of the lower hybrid mode. Present work should be of relevance for the dense astrophysical environments like white dwarfs and for laboratory experiments.

Revealing strategies of quorum sensing in Azospirillum brasilense strains Ab-V5 and Ab-V6.

PubMed

Fukami, Josiane; Abrantes, Julia Laura Fernandes; Del Cerro, Pablo; Nogueira, Marco Antonio; Ollero, Francisco Javier; Megías, Manuel; Hungria, Mariangela

2018-01-01

Azospirillum brasilense is an important plant-growth promoting bacterium (PGPB) that requires several critical steps for root colonization, including biofilm and exopolysaccharide (EPS) synthesis and cell motility. In several bacteria these mechanisms are mediated by quorum sensing (QS) systems that regulate the expression of specific genes mediated by the autoinducers N-acyl-homoserine lactones (AHLs). We investigated QS mechanisms in strains Ab-V5 and Ab-V6 of A. brasilense, which are broadly used in commercial inoculants in Brazil. Neither of these strains carries a luxI gene, but there are several luxR solos that might perceive AHL molecules. By adding external AHLs we verified that biofilm and EPS production and cell motility (swimming and swarming) were regulated via QS in Ab-V5, but not in Ab-V6. Differences were observed not only between strains, but also in the specificity of LuxR-type receptors to AHL molecules. However, Ab-V6 was outstanding in indole acetic acid (IAA) synthesis and this molecule might mimic AHL signals. We also applied the quorum quenching (QQ) strategy, obtaining transconjugants of Ab-V5 and Ab-V6 carrying a plasmid with acyl-homoserine lactonase. When maize (Zea mays L.) was inoculated with the wild-type and transconjugant strains, plant growth was decreased with the transconjugant of Ab-V5-confirming the importance of an AHL-mediated QS system-but did not affect plant growth promotion by Ab-V6.

Undoing Gender Through Legislation and Schooling: the Case of AB 537 and AB 394 IN California, USA

NASA Astrophysics Data System (ADS)

Knotts, Greg

2009-11-01

This article investigates California laws AB 537: The Student Safety and Violence Prevention Act of 2000, and the recently enacted AB 394: Safe Place to Learn Act. Both demand that gender identity and sexual orientation be added to the lexicon of anti-harassment protection in public education. However, despite these progressive measures, schools have an unconscious acceptance of heteronormativity and gendered norms, which undermines both the spirit and language of these laws. This paper examines how California schools can both change standard practices and realise the transformative social change that laws like AB 537 and AB 394 can instigate. I assert that the systemic implementation of these laws, through the adoption, enforcement and evaluation of existing AB 537 Task Force Recommendations, is necessary for their success. My second assertion is that AB 537 and AB 394 have the potential to change and reconstitute gender-based and heteronormative standards at school sites.

Data and Analysis of the Double Stars STFA 10AB and STFA 1744AB

NASA Astrophysics Data System (ADS)

Arcilla, Marisa; Bowden, Sam; DeBlase, Jacqueline; Hall, Anthony; Hall, Corielyn; Hernandez, Alyssa; Renna, Danielle; Rodriguez, Fatima; Salazar, Cassandra; Sanchez, Andres; Teeter, Dayton; Brewer, Mark; Funk, Benjamin; Gillette, Travis; Sharpe, Scott

2017-04-01

Eighth grade students at Vanguard Preparatory School measured the double stars STFA 10AB and STFA 1744AB. A 22-inch Newtonian Alt/Az telescope and a 14-inch Celestron Schmidt Cassegrain telescope were used. The star Bellatrix was used as the calibration star to determine the scale constant of the 22-inch telescope to be 7.8 “/tick marks. The double star STFA 1744AB was used as the calibration star to determine the scale constant of the 14-inch telescope to be 5.1 “/tick marks. The separation and position angle of STFA 10AB was determined by the 22-inch telescope to be 347.9” and 339.3°. The separation and position angle of STFA 1744AB was determined by the 14-inch telescope to be 3.6” and 158.1°. The measurements that were calculated were compared to the most recent measurements listed in the Washington Double Star Catalog.

Ab Initio Path Integral Molecular Dynamics Study of the Nuclear Quantum Effect on Out-of-Plane Ring Deformation of Hydrogen Maleate Anion.

PubMed

Kawashima, Yukio; Tachikawa, Masanori

2014-01-14

Ab initio path integral molecular dynamics (PIMD) simulation was performed to understand the nuclear quantum effect on the out-of-plane ring deformation of hydrogen maleate anion and investigate the existence of a stable structure with ring deformation, which was suggested in experimental observation (Fillaux et al., Chem. Phys. 1999, 120, 387-403). The isotope effect and the temperature effect are studied as well. We first investigated the nuclear quantum effect on the proton transfer. In static calculation and classical ab initio molecular dynamics simulations, the proton in the hydrogen bond is localized to either oxygen atom. On the other hand, the proton is located at the center of two oxygen atoms in quantum ab initio PIMD simulations. The nuclear quantum effect washes out the barrier of proton transfer. We next examined the nuclear quantum effect on the motion of hydrogen maleate anion. Principal component analysis revealed that the out-of-plane ring bending modes have dominant contribution to the entire molecular motion. In quantum ab initio PIMD simulations, structures with ring deformation were the global minimum for the deuterated isotope at 300 K. We analyzed the out-of-plane ring bending mode further and found that there are three minima along a ring distortion mode. We successfully found a stable structure with ring deformation of hydrogen maleate for the first time, to our knowledge, using theoretical calculation. The structures with ring deformation found in quantum simulation of the deuterated isotope allowed the proton transfer to occur more frequently than the planar structure. Static ab initio electronic structure calculation found that the structures with ring deformation have very small proton transfer barrier compared to the planar structure. We suggest that the "proton transfer driven" mechanism is the origin of stabilization for the structure with out-of-plane ring deformation.

Quantum effects on compressional Alfven waves in compensated semiconductors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amin, M. R.

2015-03-15

Amplitude modulation of a compressional Alfven wave in compensated electron-hole semiconductor plasmas is considered in the quantum magnetohydrodynamic regime in this paper. The important ingredients of this study are the inclusion of the particle degeneracy pressure, exchange-correlation potential, and the quantum diffraction effects via the Bohm potential in the momentum balance equations of the charge carriers. A modified nonlinear Schrödinger equation is derived for the evolution of the slowly varying amplitude of the compressional Alfven wave by employing the standard reductive perturbation technique. Typical values of the parameters for GaAs, GaSb, and GaN semiconductors are considered in analyzing the linearmore » and nonlinear dispersions of the compressional Alfven wave. Detailed analysis of the modulation instability in the long-wavelength regime is presented. For typical parameter ranges of the semiconductor plasmas and at the long-wavelength regime, it is found that the wave is modulationally unstable above a certain critical wavenumber. Effects of the exchange-correlation potential and the Bohm potential in the wave dynamics are also studied. It is found that the effect of the Bohm potential may be neglected in comparison with the effect of the exchange-correlation potential in the linear and nonlinear dispersions of the compressional Alfven wave.« less

Towards Accurate Ab Initio Predictions of the Spectrum of Methane

NASA Technical Reports Server (NTRS)

Schwenke, David W.; Kwak, Dochan (Technical Monitor)

2001-01-01

We have carried out extensive ab initio calculations of the electronic structure of methane, and these results are used to compute vibrational energy levels. We include basis set extrapolations, core-valence correlation, relativistic effects, and Born- Oppenheimer breakdown terms in our calculations. Our ab initio predictions of the lowest lying levels are superb.

Registration of nine sorghum seed parent (A/B) lines

USDA-ARS?s Scientific Manuscript database

Nine sorghum [Sorghum bicolor (L.) Moench] A1 cyto plasmic-genic male sterile seed parent (A) and their maintainer (B) lines [KS 133A/B, KS 134A/B, KS 135A/B, KS 136A/B, KS 137A/B, KS 138A/B, KS 139A/B, KS 140A/B and KS 141A/B] were released by the Kansas State University, Agricultural Research Cent...

Ab Initio Classical Dynamics Simulations of CO_2 Line-Mixing Effects in Infrared Bands

NASA Astrophysics Data System (ADS)

Lamouroux, Julien; Hartmann, Jean-Michel; Tran, Ha; Snels, Marcel; Stefani, Stefania; Piccioni, Giuseppe

2013-06-01

Ab initio calculations of line-mixing effects in CO_2 infrared bands are presented and compared with experiments. The predictions were carried using requantized Classical Dynamics Molecular Simulations (rCDMS) based on an approach previously developed and successfully tested for CO_2 isolated line shapes. Using classical dynamics equations, the force and torque applied to each molecule by the surrounding molecules (described by an ab initio intermolecular potential) are computed at each time step. This enables, using a requantization procedure, to predict dipole and isotropic polarizability auto-correlation functions whose Fourier-Laplace transforms yield the spectra. The quality of the rCDMS calculations is demonstrated by comparisons with measured spectra in the spectral regions of the 3ν_3 and 2ν_1+2ν_2+ν_3 Infrared bands. J.-M. Hartmann, H. Tran, N. H. Ngo, et al., Phys. Rev. Lett. A {87} (2013), 013403. H. Tran, C. Boulet, M. Snels, S. Stefani, J. Quant. Spectrosc. Radiat. Transfer {112} (2011), 925-936.

Ab Initio Crystal Field for Lanthanides.

PubMed

Ungur, Liviu; Chibotaru, Liviu F

2017-03-13

An ab initio methodology for the first-principle derivation of crystal-field (CF) parameters for lanthanides is described. The methodology is applied to the analysis of CF parameters in [Tb(Pc) 2 ] - (Pc=phthalocyanine) and Dy 4 K 2 ([Dy 4 K 2 O(OtBu) 12 ]) complexes, and compared with often used approximate and model descriptions. It is found that the application of geometry symmetrization, and the use of electrostatic point-charge and phenomenological CF models, lead to unacceptably large deviations from predictions based on ab initio calculations for experimental geometry. It is shown how the predictions of standard CASSCF (Complete Active Space Self-Consistent Field) calculations (with 4f orbitals in the active space) can be systematically improved by including effects of dynamical electronic correlation (CASPT2 step) and by admixing electronic configurations of the 5d shell. This is exemplified for the well-studied Er-trensal complex (H 3 trensal=2,2',2"-tris(salicylideneimido)trimethylamine). The electrostatic contributions to CF parameters in this complex, calculated with true charge distributions in the ligands, yield less than half of the total CF splitting, thus pointing to the dominant role of covalent effects. This analysis allows the conclusion that ab initio crystal field is an essential tool for the decent description of lanthanides. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inhibition of cholera toxin and other AB toxins by polyphenolic compounds

USDA-ARS?s Scientific Manuscript database

All AB-type protein toxins have intracellular targets despite an initial extracellular location. These toxins use different methods to reach the cytosol and have different effects on the target cell. Broad-spectrum inhibitors against AB toxins are therefore hard to develop because the toxins use dif...

AB toxins: a paradigm switch from deadly to desirable.

PubMed

Odumosu, Oludare; Nicholas, Dequina; Yano, Hiroshi; Langridge, William

2010-07-01

To ensure their survival, a number of bacterial and plant species have evolved a common strategy to capture energy from other biological systems. Being imperfect pathogens, organisms synthesizing multi-subunit AB toxins are responsible for the mortality of millions of people and animals annually. Vaccination against these organisms and their toxins has proved rather ineffective in providing long-term protection from disease. In response to the debilitating effects of AB toxins on epithelial cells of the digestive mucosa, mechanisms underlying toxin immunomodulation of immune responses have become the focus of increasing experimentation. The results of these studies reveal that AB toxins may have a beneficial application as adjuvants for the enhancement of immune protection against infection and autoimmunity. Here, we examine similarities and differences in the structure and function of bacterial and plant AB toxins that underlie their toxicity and their exceptional properties as immunomodulators for stimulating immune responses against infectious disease and for immune suppression of organ-specific autoimmunity.

AB Toxins: A Paradigm Switch from Deadly to Desirable

PubMed Central

Odumosu, Oludare; Nicholas, Dequina; Yano, Hiroshi; Langridge, William

2010-01-01

To ensure their survival, a number of bacterial and plant species have evolved a common strategy to capture energy from other biological systems. Being imperfect pathogens, organisms synthesizing multi-subunit AB toxins are responsible for the mortality of millions of people and animals annually. Vaccination against these organisms and their toxins has proved rather ineffective in providing long-term protection from disease. In response to the debilitating effects of AB toxins on epithelial cells of the digestive mucosa, mechanisms underlying toxin immunomodulation of immune responses have become the focus of increasing experimentation. The results of these studies reveal that AB toxins may have a beneficial application as adjuvants for the enhancement of immune protection against infection and autoimmunity. Here, we examine similarities and differences in the structure and function of bacterial and plant AB toxins that underlie their toxicity and their exceptional properties as immunomodulators for stimulating immune responses against infectious disease and for immune suppression of organ-specific autoimmunity. PMID:22069653

Ab initio vel ex eventu

NASA Astrophysics Data System (ADS)

Thiessen, P. A.; Treder, H.-J.

Der gegenwärtige Stand der physikalischen Erkenntnis, in Sonderheit die Atomistik und die Quantentheorie, ermöglicht (in wohldefinierten Energie-Bereichen) eine ab initio-Berechnung aller physikalischen und chemischen Prozesse und Strukturen. Die Schrödinger-Gleichung erlaubt zusammen mit den Prinzipien der Quantenstatistik (Pauli-Prinzip) aus dem Planckschen Wirkungsquantum h und den atomischen Konstanten die Berechnung aller Energieumsätze, Zeitabläufe etc., die insbesondere die chemische Physik bestimmen. Die Rechenresultate gelten auch quantitativ bis auf die unvermeidliche Stochastik.Die ab initio-Berechnungen korrespondieren einerseits und sind andererseits komplementär zu den auf den Methoden der theoretischen Chemie und der klassischen Thermodynamik beruhenden Ergebnissen ex eventu. Die theoretische Behandlung ab initio führt zu mathematischen Experimenten, die die Laboratoriums-Experimente ergänzen oder auch substituieren.Translated AbstractAb initio vel ex eventuThe present state of physical knowledge, in peculiar atomistic and quantum theory, makes an ab initio calculation of all physical and chemical processes and structures possible (in well defined reaches of energy). The Schrödinger equation together with the principles of quantum statistics (Pauli principle) permits from the Planck and atomistic constants to calculate all exchanges of energy, courses of time, etc. which govern chemical physics. The calculated results are valid even quantitatively apart from the unavoidable stochastics.These ab initio calculations on the one hand correspond and are on the other complimentary to results ex eventu based on the methods of theoretical chemistry and classical thermodynamics. Theoretical treatment ab initio leads to mathematical experiments which add to or even substitute experiments in the laboratory.

Modification of the quantum mechanical flux formula for electron-hydrogen ionization through Bohm's velocity field

NASA Astrophysics Data System (ADS)

Randazzo, J. M.; Ancarani, L. U.

2015-12-01

For the single differential cross section (SDCS) for hydrogen ionization by electron impact (e -H problem), we propose a correction to the flux formula given by R. Peterkop [Theory of Ionization of Atoms by Electron Impact (Colorado Associated University Press, Boulder, 1977)]. The modification is based on an alternative way of defining the kinetic energy fraction, using Bohm's definition of velocities instead of the usual asymptotic kinematical, or geometrical, approximation. It turns out that the solution-dependent, modified energy fraction is equally related to the components of the probability flux. Compared to what is usually observed, the correction yields a finite and well-behaved SDCS value in the asymmetrical situation where one of the continuum electrons carries all the energy while the other has zero energy. We also discuss, within the S -wave model of the e -H ionization process, the continuity of the SDCS derivative at the equal energy sharing point, a property not so clearly observed in published benchmark results obtained with integral and S -matrix formulas with unequal final states.

Spectral transmission of the pig lens: effect of ultraviolet A+B radiation.

PubMed

Artigas, C; Navea, A; López-Murcia, M-M; Felipe, A; Desco, C; Artigas, J-M

2014-12-01

To determine the spectral transmission curve of the crystalline lens of the pig. To analyse how this curve changes when the crystalline lens is irradiated with ultraviolet A+B radiation similar to that of the sun. To compare these results with literature data from the human crystalline lens. We used crystalline lenses of the common pig from a slaughterhouse, i.e. genetically similar pigs, fed with the same diet, and slaughtered at six months old. Spectral transmission was measured with a Perkin-Elmer Lambda 35 UV/VIS spectrometer. The lenses were irradiated using an Asahi Spectra Lax-C100 ultraviolet source, which made it possible to select the spectral emission band as well as the intensity and exposure time. The pig lens transmits all the visible spectrum (95%) and lets part of the ultraviolet A through (15%). Exposure to acute UV (A+B) irradiation causes a decrease in its transmission as the intensity or exposure time increases: this decrease is considerable in the UV region. We were able to determine the mean spectral transmission curve of the pig lens. It appears to be similar to that of the human lens in the visible spectrum, but different in the ultraviolet. Pig lens transmission is reduced by UV (A+B) irradiation and its transmission in the UV region can even disappear as the intensity or exposure time increases. An adequate exposure intensity and time of UV (A+B) radiation always causes an anterior subcapsular cataract (ASC). Copyright © 2014. Published by Elsevier Masson SAS.

Structural and Biophysical Characterization of Bacillus thuringiensis Insecticidal Proteins Cry34Ab1 and Cry35Ab1

PubMed Central

Kelker, Matthew S.; Berry, Colin; Evans, Steven L.; Pai, Reetal; McCaskill, David G.; Wang, Nick X.; Russell, Joshua C.; Baker, Matthew D.; Yang, Cheng; Pflugrath, J. W.; Wade, Matthew; Wess, Tim J.; Narva, Kenneth E.

2014-01-01

Bacillus thuringiensis strains are well known for the production of insecticidal proteins upon sporulation and these proteins are deposited in parasporal crystalline inclusions. The majority of these insect-specific toxins exhibit three domains in the mature toxin sequence. However, other Cry toxins are structurally and evolutionarily unrelated to this three-domain family and little is known of their three dimensional structures, limiting our understanding of their mechanisms of action and our ability to engineer the proteins to enhance their function. Among the non-three domain Cry toxins, the Cry34Ab1 and Cry35Ab1 proteins from B. thuringiensis strain PS149B1 are required to act together to produce toxicity to the western corn rootworm (WCR) Diabrotica virgifera virgifera Le Conte via a pore forming mechanism of action. Cry34Ab1 is a protein of ∼14 kDa with features of the aegerolysin family (Pfam06355) of proteins that have known membrane disrupting activity, while Cry35Ab1 is a ∼44 kDa member of the toxin_10 family (Pfam05431) that includes other insecticidal proteins such as the binary toxin BinA/BinB. The Cry34Ab1/Cry35Ab1 proteins represent an important seed trait technology having been developed as insect resistance traits in commercialized corn hybrids for control of WCR. The structures of Cry34Ab1 and Cry35Ab1 have been elucidated to 2.15 Å and 1.80 Å resolution, respectively. The solution structures of the toxins were further studied by small angle X-ray scattering and native electrospray ion mobility mass spectrometry. We present here the first published structure from the aegerolysin protein domain family and the structural comparisons of Cry34Ab1 and Cry35Ab1 with other pore forming toxins. PMID:25390338

Ab initio interatomic potentials and the thermodynamic properties of fluids

NASA Astrophysics Data System (ADS)

Vlasiuk, Maryna; Sadus, Richard J.

2017-07-01

Monte Carlo simulations with accurate ab initio interatomic potentials are used to investigate the key thermodynamic properties of argon and krypton in both vapor and liquid phases. Data are reported for the isochoric and isobaric heat capacities, the Joule-Thomson coefficient, and the speed of sound calculated using various two-body interatomic potentials and different combinations of two-body plus three-body terms. The results are compared to either experimental or reference data at state points between the triple and critical points. Using accurate two-body ab initio potentials, combined with three-body interaction terms such as the Axilrod-Teller-Muto and Marcelli-Wang-Sadus potentials, yields systematic improvements to the accuracy of thermodynamic predictions. The effect of three-body interactions is to lower the isochoric and isobaric heat capacities and increase both the Joule-Thomson coefficient and speed of sound. The Marcelli-Wang-Sadus potential is a computationally inexpensive way to utilize accurate two-body ab initio potentials for the prediction of thermodynamic properties. In particular, it provides a very effective way of extending two-body ab initio potentials to liquid phase properties.

Ab initio interatomic potentials and the thermodynamic properties of fluids.

PubMed

Vlasiuk, Maryna; Sadus, Richard J

2017-07-14

Monte Carlo simulations with accurate ab initio interatomic potentials are used to investigate the key thermodynamic properties of argon and krypton in both vapor and liquid phases. Data are reported for the isochoric and isobaric heat capacities, the Joule-Thomson coefficient, and the speed of sound calculated using various two-body interatomic potentials and different combinations of two-body plus three-body terms. The results are compared to either experimental or reference data at state points between the triple and critical points. Using accurate two-body ab initio potentials, combined with three-body interaction terms such as the Axilrod-Teller-Muto and Marcelli-Wang-Sadus potentials, yields systematic improvements to the accuracy of thermodynamic predictions. The effect of three-body interactions is to lower the isochoric and isobaric heat capacities and increase both the Joule-Thomson coefficient and speed of sound. The Marcelli-Wang-Sadus potential is a computationally inexpensive way to utilize accurate two-body ab initio potentials for the prediction of thermodynamic properties. In particular, it provides a very effective way of extending two-body ab initio potentials to liquid phase properties.

Towards accurate ab initio predictions of the vibrational spectrum of methane

NASA Technical Reports Server (NTRS)

Schwenke, David W.

2002-01-01

We have carried out extensive ab initio calculations of the electronic structure of methane, and these results are used to compute vibrational energy levels. We include basis set extrapolations, core-valence correlation, relativistic effects, and Born-Oppenheimer breakdown terms in our calculations. Our ab initio predictions of the lowest lying levels are superb.

Ab initio determination of effective electron-phonon coupling factor in copper

NASA Astrophysics Data System (ADS)

Ji, Pengfei; Zhang, Yuwen

2016-04-01

The electron temperature Te dependent electron density of states g (ε), Fermi-Dirac distribution f (ε), and electron-phonon spectral function α2 F (Ω) are computed as prerequisites before achieving effective electron-phonon coupling factor Ge-ph. The obtained Ge-ph is implemented into a molecular dynamics (MD) and two-temperature model (TTM) coupled simulation of femtosecond laser heating. By monitoring temperature evolutions of electron and lattice subsystems, the result utilizing Ge-ph from ab initio calculation shows a faster decrease of Te and increase of Tl than those using Ge-ph from phenomenological treatment. The approach of calculating Ge-ph and its implementation into MD-TTM simulation is applicable to other metals.

Morphology Formation in PC/ABS Blends during Thermal Processing and the Effect of the Viscosity Ratio of Blend Partners

PubMed Central

Bärwinkel, Stefanie; Seidel, Andreas; Hobeika, Sven; Hufen, Ralf; Mörl, Michaela; Altstädt, Volker

2016-01-01

Morphology formation during compounding, as well as injection molding of blends containing 60 wt % polycarbonate (PC) and 40 wt % polybutadiene rubber-modified styrene-acrylonitrile copolymers (ABS), has been investigated by transmission electron microscopy (TEM). Profiles of the blend morphology have been recorded in injection-molded specimens and significant morphology gradients observed between their skin and core. A <10 µm thick surface layer with strongly dispersed and elongated nano-scale (streak-like) styrene acrylonitrile (SAN) phases and well-dispersed, isolated SAN-grafted polybutadiene rubber particles is followed by a 50–150 µm thick skin layer in which polymer morphology is characterized by lamellar SAN/ABS phases. Thickness of these lamellae increases with the distance from the specimen’s surface. In the core of the specimens the SAN-grafted polybutadiene rubber particles are exclusively present within the SAN phases, which exhibit a much coarser and less oriented, dispersed morphology compared to the skin. The effects of the viscosity of the SAN in the PC/ABS blends on phase morphologies and correlations with fracture mechanics in tensile and impact tests were investigated, including scanning electron microscopy (SEM) assessment of the fracture surfaces. A model explaining the mechanisms of morphology formation during injection molding of PC/ABS blends is discussed. PMID:28773780

Solvent (acetone-butanol: ab) production

USDA-ARS?s Scientific Manuscript database

This article describes production of butanol [acetone-butanol-ethanol, (also called AB or ABE or solvent)] by fermentation using both traditional and current technologies. AB production from agricultural commodities, such as corn and molasses, was an important historical fermentation. Unfortunately,...

Staphylococcus aureus Biofilms Induce Macrophage Dysfunction Through Leukocidin AB and Alpha-Toxin

PubMed Central

Scherr, Tyler D.; Hanke, Mark L.; Huang, Ouwen; James, David B. A.; Horswill, Alexander R.; Bayles, Kenneth W.; Fey, Paul D.; Torres, Victor J.

2015-01-01

ABSTRACT The macrophage response to planktonic Staphylococcus aureus involves the induction of proinflammatory microbicidal activity. However, S. aureus biofilms can interfere with these responses in part by polarizing macrophages toward an anti-inflammatory profibrotic phenotype. Here we demonstrate that conditioned medium from mature S. aureus biofilms inhibited macrophage phagocytosis and induced cytotoxicity, suggesting the involvement of a secreted factor(s). Iterative testing found the active factor(s) to be proteinaceous and partially agr-dependent. Quantitative mass spectrometry identified alpha-toxin (Hla) and leukocidin AB (LukAB) as critical molecules secreted by S. aureus biofilms that inhibit murine macrophage phagocytosis and promote cytotoxicity. A role for Hla and LukAB was confirmed by using hla and lukAB mutants, and synergy between the two toxins was demonstrated with a lukAB hla double mutant and verified by complementation. Independent confirmation of the effects of Hla and LukAB on macrophage dysfunction was demonstrated by using an isogenic strain in which Hla was constitutively expressed, an Hla antibody to block toxin activity, and purified LukAB peptide. The importance of Hla and LukAB during S. aureus biofilm formation in vivo was assessed by using a murine orthopedic implant biofilm infection model in which the lukAB hla double mutant displayed significantly lower bacterial burdens and more macrophage infiltrates than each single mutant. Collectively, these findings reveal a critical synergistic role for Hla and LukAB in promoting macrophage dysfunction and facilitating S. aureus biofilm development in vivo. PMID:26307164

Ab-initio calculation of electronic structure and optical properties of AB-stacked bilayer α-graphyne

NASA Astrophysics Data System (ADS)

Behzad, Somayeh

2016-09-01

Monolayer α-graphyne is a new two-dimensional carbon allotrope with many special features. In this work the electronic properties of AA- and AB-stacked bilayers of this material and then the optical properties are studied, using first principle plane wave method. The electronic spectrum has two Dirac cones for AA stacked bilayer α-graphyne. For AB-stacked bilayer, the interlayer interaction changes the linear bands into parabolic bands. The optical spectra of the most stable AB-stacked bilayer closely resemble to that of the monolayer, except for small shifts of peak positions and increasing of their intensity. For AB-stacked bilayer, a pronounced peak has been found at low energies under the perpendicular polarization. This peak can be clearly ascribed to the transitions at the Dirac point as a result of the small degeneracy lift in the band structure.

Field Trial Performance of Herculex XTRA (Cry34Ab1/Cry35Ab1) and SmartStax (Cry34Ab1/Cry35Ab1 + Cry3Bb1) Hybrids and Soil Insecticides Against Western and Northern Corn Rootworms (Coleoptera: Chrysomelidae).

PubMed

Johnson, K D; Campbell, L A; Lepping, M D; Rule, D M

2017-06-01

Western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), and northern corn rootworm, Diabrotica barberi Smith and Lawrence (Coleoptera: Chrysomelidae), are important insect pests in corn, Zea mays L. For more than a decade, growers have been using transgenic plants expressing proteins from the bacterium Bacillus thuringiensis (Bt) to protect corn roots from feeding. In 2011, western corn rootworm populations were reported to have developed resistance to Bt hybrids expressing Cry3Bb1 and later found to be cross-resistant to hybrids expressing mCry3A and eCry3.1Ab. The identification of resistance to Cry3 (Cry3Bb1, mCry3A, and eCry3.1Ab) hybrids led to concerns about durability and efficacy of products with single traits and of products containing a pyramid of a Cry3 protein and the binary Bt proteins Cry34Ab1 and Cry35Ab1. From 2012 to 2014, 43 field trials were conducted across the central United States to estimate root protection provided by plants expressing Cry34Ab1/Cry35Ab1 alone (Herculex RW) or pyramided with Cry3Bb1 (SmartStax). These technologies were evaluated with and without soil-applied insecticides to determine if additional management measures provided benefit where Cry3 performance was reduced. Trials were categorized for analysis based on rootworm damage levels on Cry3-expressing hybrids and rootworm feeding pressure within each trial. Across scenarios, Cry34Ab1/Cry35Ab1 hybrids provided excellent root protection. Pyramided traits provided greater root and yield protection than non-Bt plus a soil-applied insecticide, and only in trials where larval feeding pressure exceeded two nodes of damage did Cry34Ab1/Cry35Ab1 single-trait hybrids and pyramided hybrids show greater root protection from the addition of soil-applied insecticides. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Scattering from a quantum anapole at low energies

NASA Astrophysics Data System (ADS)

Whitcomb, Kyle M.; Latimer, David C.

2017-12-01

In quantum field theory, the photon-fermion vertex can be described in terms of four form-factors that encode the static electromagnetic properties of the particle, namely, its charge, magnetic dipole moment, electric dipole moment, and anapole moment. For Majorana fermions, only the anapole moment can be nonzero, a consequence of the fact that these particles are their own antiparticles. Using the framework of quantum field theory, we perform a scattering calculation that probes the anapole moment with a spinless charged particle. In the limit of low momentum transfer, we confirm that the anapole can be classically likened to a point-like toroidal solenoid whose magnetic field is confined to the origin. Such a toroidal current distribution can be used to demonstrate the Aharonov-Bohm effect. We find that, in the non-relativistic limit, our scattering cross section agrees with a quantum mechanical computation of the cross section for a spinless current scattered by an infinitesimally thin toroidal solenoid. Our presentation is geared toward advanced undergraduate or beginning graduate students. This work serves as an introduction to the anapole moment and also provides an example of how one can develop an understanding of a particle's electromagnetic properties in quantum field theory.

Utilizing public scientific web lectures to teach contemporary physics at the high school level: A case study of learning

NASA Astrophysics Data System (ADS)

Kapon, Shulamit; Ganiel, Uri; Eylon, Bat Sheva

2011-12-01

This paper describes a teaching experiment designed to examine the learning (i.e., retention of content and conceptual development) that takes place when public scientific web lectures delivered by scientists are utilized to present advanced ideas in physics to students with a high school background in physics. The students watched an exemplary public physics web lecture that was followed by a collaborative generic activity session. The collaborative session involved a guided critical reconstruction of the main arguments in the lecture, and a processing of the key analogical explanations. Then the students watched another exemplary web lecture on a different topic. The participants (N=14) were divided into two groups differing only in the order in which the lectures were presented. The students’ discussions during the activities show that they were able to reason and demonstrate conceptual progress, although the physics ideas in the lectures were far beyond their level in physics. The discussions during the collaborative session contributed significantly to the students’ understanding. We illustrate this point through an analysis of one of these discussions between two students on an analogical explanation of the Aharonov-Bohm effect that was presented in one of the lectures. The results from the tests that were administered to the participants several times during the intervention further support this contention.

The Case of the Disappearing (and Re-Appearing) Particle.

PubMed

Aharonov, Yakir; Cohen, Eliahu; Landau, Ariel; Elitzur, Avshalom C

2017-04-03

A novel prediction is derived by the Two-State-Vector-Formalism (TSVF) for a particle superposed over three boxes. Under appropriate pre- and post-selections, and with tunneling enabled between two of the boxes, it is possible to derive not only one, but three predictions for three different times within the intermediate interval. These predictions are moreover contradictory. The particle (when looked for using a projective measurement) seems to disappear from the first box where it would have been previously found with certainty, appearing instead within the third box, to which no tunneling is possible, and later re-appearing within the second. It turns out that local measurement (i.e. opening one of the boxes) fails to indicate the particle's presence, but subtler measurements performed on the two boxes together reveal the particle's nonlocal modular momentum spatially separated from its mass. Another advance of this setting is that, unlike other predictions of the TSVF that rely on weak and/or counterfactual measurements, the present one uses actual projective measurements. This outcome is then corroborated by adding weak measurements and the Aharonov-Bohm effect. The results strengthen the recently suggested time-symmetric Heisenberg ontology based on nonlocal deterministic operators. They can be also tested using the newly developed quantum router.

Epitaxy of advanced nanowire quantum devices

NASA Astrophysics Data System (ADS)

Gazibegovic, Sasa; Car, Diana; Zhang, Hao; Balk, Stijn C.; Logan, John A.; de Moor, Michiel W. A.; Cassidy, Maja C.; Schmits, Rudi; Xu, Di; Wang, Guanzhong; Krogstrup, Peter; Op Het Veld, Roy L. M.; Zuo, Kun; Vos, Yoram; Shen, Jie; Bouman, Daniël; Shojaei, Borzoyeh; Pennachio, Daniel; Lee, Joon Sue; van Veldhoven, Petrus J.; Koelling, Sebastian; Verheijen, Marcel A.; Kouwenhoven, Leo P.; Palmstrøm, Chris J.; Bakkers, Erik P. A. M.

2017-08-01

Semiconductor nanowires are ideal for realizing various low-dimensional quantum devices. In particular, topological phases of matter hosting non-Abelian quasiparticles (such as anyons) can emerge when a semiconductor nanowire with strong spin-orbit coupling is brought into contact with a superconductor. To exploit the potential of non-Abelian anyons—which are key elements of topological quantum computing—fully, they need to be exchanged in a well-controlled braiding operation. Essential hardware for braiding is a network of crystalline nanowires coupled to superconducting islands. Here we demonstrate a technique for generic bottom-up synthesis of complex quantum devices with a special focus on nanowire networks with a predefined number of superconducting islands. Structural analysis confirms the high crystalline quality of the nanowire junctions, as well as an epitaxial superconductor-semiconductor interface. Quantum transport measurements of nanowire ‘hashtags’ reveal Aharonov-Bohm and weak-antilocalization effects, indicating a phase-coherent system with strong spin-orbit coupling. In addition, a proximity-induced hard superconducting gap (with vanishing sub-gap conductance) is demonstrated in these hybrid superconductor-semiconductor nanowires, highlighting the successful materials development necessary for a first braiding experiment. Our approach opens up new avenues for the realization of epitaxial three-dimensional quantum architectures which have the potential to become key components of various quantum devices.

Cobalt-doped ZnO nanocrystals: quantum confinement and surface effects from ab initio methods.

PubMed

Schoenhalz, Aline L; Dalpian, Gustavo M

2013-10-14

Cobalt-doped ZnO nanocrystals were studied through ab initio methods based on the Density Functional Theory. Both quantum confinement and surface effects were explicitly taken into account. When only quantum confinement effects are considered, Co atoms interact through a superexchange mechanism, stabilizing an antiferromagnetic ground state. Usually, this is the case for high quality nanoparticles with perfect surface saturation. When the surfaces were considered, a strong hybridization between the Co atoms and surfaces was observed, strongly changing their electronic and magnetic properties. Our results indicated that the surfaces might qualitatively change the properties of impurities in semiconductor nanocrystals.

[In vitro hepatic targeting tendency of galactosyl-anti CD3 McAb-TILS].

PubMed

Jiang, P; He, S; Zhang, C

1999-03-01

This study was undertaken to enhance the hepatic targeting tendency of tumor infiltrating lymphocytes (TILs) and hence to lower the recurrence rate of primary liver cancer after hepatectomy. Galactosyl-anti CD3McAb-TILs were prepared and then were incubated together with hepatocytes. Their interaction through asialoglycoprotein receptor-mediated mechanism was observed under the inverted phase contrast microscope. The carbohydrate density of galactosyl-anti CD3McAb and the combining rate of galactosyl-anti CD3McAb with TILs were measured. The results revealed that galactosyl-anti CD3 McAb-TIL obviously were adhered to hepatocytes. The carbohydrate density of galactosyl-anti CD3McAb was 62.18, and the combining rate of galactosyl-anti CD3McAb with TILs was 97.9%. The results suggested that in vitro hepatic targeting tendency of galactosyl-anti CD3McAb-TILs was satisfactory, and that the carbohydrate density of 62.18 and the combining rate of 97.9% ensured the effective use of TILs.

Berry phase and anomalous transport of the composite fermions at the half-filled Landau level

NASA Astrophysics Data System (ADS)

Pan, W.; Kang, W.; Baldwin, K. W.; West, K. W.; Pfeiffer, L. N.; Tsui, D. C.

2017-12-01

The fractional quantum Hall effect (FQHE) in two-dimensional electron systems is an exotic, superfluid-like matter with an emergent topological order. From the consideration of the Aharonov-Bohm interaction between electrons and magnetic field, the ground state of a half-filled lowest Landau level is mathematically transformed to a Fermi sea of composite objects of electrons bound to two flux quanta, termed composite fermions (CFs). A strong support for the CF theories comes from experimental confirmation of the predicted Fermi surface at ν = 1/2 (where ν is the Landau level filling factor) from the detection of the Fermi wavevector in semi-classical geometrical resonance experiments. Recent developments in the theory of CFs have led to the prediction of a π Berry phase for the CF circling around the Fermi surface at half-filling. In this paper we provide experimental evidence for the detection of the Berry phase of CFs in the fractional quantum Hall effect. Our measurements of the Shubnikov-de Haas oscillations of CFs as a function carrier density at a fixed magnetic field provide strong support for the existence of a π Berry phase at ν = 1/2. We also discover that the conductivity of composite fermions at ν = 1/2 displays an anomalous linear density dependence, whose origin remains mysterious yet tantalizing.

Time-evolution of photon heat current through series coupled two mesoscopic Josephson junction devices

NASA Astrophysics Data System (ADS)

Lu, Wen-Ting; Zhao, Hong-Kang; Wang, Jian

2018-03-01

Photon heat current tunneling through a series coupled two mesoscopic Josephson junction (MJJ) system biased by dc voltages has been investigated by employing the nonequilibrium Green’s function approach. The time-oscillating photon heat current is contributed by the superposition of different current branches associated with the frequencies of MJJs ω j (j = 1, 2). Nonlinear behaviors are exhibited to be induced by the self-inductance, Coulomb interaction, and interference effect relating to the coherent transport of Cooper pairs in the MJJs. Time-oscillating pumping photon heat current is generated in the absence of temperature difference, while it becomes zero after time-average. The combination of ω j and Coulomb interactions in the MJJs determines the concrete heat current configuration. As the external and intrinsic frequencies ω j and ω 0 of MJJs match some specific combinations, resonant photon heat current exhibits sinusoidal behaviors with large amplitudes. Symmetric and asymmetric evolutions versus time t with respect to ω 1 t and ω 2 t are controlled by the applied dc voltages of V 1 and V 2. The dc photon heat current formula is a special case of the general time-dependent heat current formula when the bias voltages are settled to zero. The Aharonov-Bohm effect has been investigated, and versatile oscillation structures of photon heat current can be achieved by tuning the magnetic fluxes threading through separating MJJs.

Surface Segregation Energies of BCC Binaries from Ab Initio and Quantum Approximate Calculations

NASA Technical Reports Server (NTRS)

Good, Brian S.

2003-01-01

We compare dilute-limit segregation energies for selected BCC transition metal binaries computed using ab initio and quantum approximate energy method. Ab initio calculations are carried out using the CASTEP plane-wave pseudopotential computer code, while quantum approximate results are computed using the Bozzolo-Ferrante-Smith (BFS) method with the most recent parameterization. Quantum approximate segregation energies are computed with and without atomistic relaxation. The ab initio calculations are performed without relaxation for the most part, but predicted relaxations from quantum approximate calculations are used in selected cases to compute approximate relaxed ab initio segregation energies. Results are discussed within the context of segregation models driven by strain and bond-breaking effects. We compare our results with other quantum approximate and ab initio theoretical work, and available experimental results.

HHV-6A/B Integration and the Pathogenesis Associated with the Reactivation of Chromosomally Integrated HHV-6A/B.

PubMed

Collin, Vanessa; Flamand, Louis

2017-06-26

Unlike other human herpesviruses, human herpesvirus 6A and 6B (HHV-6A/B) infection can lead to integration of the viral genome in human chromosomes. When integration occurs in germinal cells, the integrated HHV-6A/B genome can be transmitted to 50% of descendants. Such individuals, carrying one copy of the HHV-6A/B genome in every cell, are referred to as having inherited chromosomally-integrated HHV-6A/B (iciHHV-6) and represent approximately 1% of the world's population. Interestingly, HHV-6A/B integrate their genomes in a specific region of the chromosomes known as telomeres. Telomeres are located at chromosomes' ends and play essential roles in chromosomal stability and the long-term proliferative potential of cells. Considering that the integrated HHV-6A/B genome is mostly intact without any gross rearrangements or deletions, integration is likely used for viral maintenance into host cells. Knowing the roles played by telomeres in cellular homeostasis, viral integration in such structure is not likely to be without consequences. At present, the mechanisms and factors involved in HHV-6A/B integration remain poorly defined. In this review, we detail the potential biological and medical impacts of HHV-6A/B integration as well as the possible chromosomal integration and viral excision processes.

Position-dependent mass, finite-gap systems, and supersymmetry

NASA Astrophysics Data System (ADS)

Bravo, Rafael; Plyushchay, Mikhail S.

2016-05-01

The ordering problem in quantum systems with position-dependent mass (PDM) is treated by inclusion of the classically fictitious similarity transformation into the kinetic term. This provides a generation of supersymmetry with the first-order supercharges from the kinetic term alone, while inclusion of the potential term allows us also to generate nonlinear supersymmetry with higher-order supercharges. A broad class of finite-gap systems with PDM is obtained by different reduction procedures, and general results on supersymmetry generation are applied to them. We show that elliptic finite-gap systems of Lamé and Darboux-Treibich-Verdier types can be obtained by reduction to Seiffert's spherical spiral and Bernoulli lemniscate in the presence of Calogero-like or harmonic oscillator potentials, or by angular momentum reduction of a free motion on some AdS2 -related surfaces in the presence of Aharonov-Bohm flux. The limiting cases include the Higgs and Mathews-Lakshmanan oscillator models as well as a reflectionless model with PDM exploited recently in the discussion of cosmological inflationary scenarios.

Phase coherent transport in hybrid superconductor-topological insulator devices

NASA Astrophysics Data System (ADS)

Finck, Aaron

2015-03-01

Heterostructures of superconductors and topological insulators are predicted to host unusual zero energy bound states known as Majorana fermions, which can robustly store and process quantum information. Here, I will discuss our studies of such heterostructures through phase-coherent transport, which can act as a unique probe of Majorana fermions. We have extensively explored topological insulator Josephson junctions through SQUID and single-junction diffraction patterns, whose unusual behavior give evidence for low-energy Andreev bound states. In topological insulator devices with closely spaced normal and superconducting leads, we observe prominent Fabry-Perot oscillations, signifying gate-tunable, quasi-ballistic transport that can elegantly interact with Andreev reflection. Superconducting disks deposited on the surface of a topological insulator generate Aharonov-Bohm-like oscillations, giving evidence for unusual states lying near the interface between the superconductor and topological insulator surface. Our results point the way towards sophisticated interferometers that can detect and read out the state of Majorana fermions in topological systems. This work was done in collaboration with Cihan Kurter, Yew San Hor, and Dale Van Harlingen. We acknowledge funding from Microsoft Project Q.

Transport properties of a quantum dot and a quantum ring in series

NASA Astrophysics Data System (ADS)

Seo, Minky; Chung, Yunchul

2018-01-01

The decoherence mechanism of an electron interferometer is studied by using a serial quantum dot and ring device. By coupling a quantum dot to a quantum ring (closed-loop electron interferometer), we were able to observe both Coulomb oscillations and Aharonov-Bohm interference simultaneously. The coupled device behaves like an ordinary double quantum dot at zero magnetic field while the conductance of the Coulomb blockade peak is modulated by the electron interference at finite magnetic fields. By injecting one electron at a time (by exploiting the sequential tunneling of a quantum dot) into the interferometer, we were able to study the visibility of the electron interference at non-zero bias voltage. The visibility was found to decay rapidly as the electron energy was increased, which was consistent with the recently reported result for an electron interferometer. However, the lobe pattern and the sudden phase jump became less prominent. These results imply that the lobe pattern and the phase jump in an electron interferometer may be due to electron interactions inside the interferometer, as is predicted by the theory.

Improving the efficiency of hierarchical equations of motion approach and application to coherent dynamics in Aharonov–Bohm interferometers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hou, Dong; Xu, RuiXue; Zheng, Xiao, E-mail: xz58@ustc.edu.cn

2015-03-14

Several recent advancements for the hierarchical equations of motion (HEOM) approach are reported. First, we propose an a priori estimate for the optimal number of basis functions for the reservoir memory decomposition. Second, we make use of the sparsity of auxiliary density operators (ADOs) and propose two ansatzs to screen out all the intrinsic zero ADO elements. Third, we propose a new truncation scheme by utilizing the time derivatives of higher-tier ADOs. These novel techniques greatly reduce the memory cost of the HEOM approach, and thus enhance its efficiency and applicability. The improved HEOM approach is applied to simulate themore » coherent dynamics of Aharonov–Bohm double quantum dot interferometers. Quantitatively accurate dynamics is obtained for both noninteracting and interacting quantum dots. The crucial role of the quantum phase for the magnitude of quantum coherence and quantum entanglement is revealed.« less

Does Cry1Ab protein affect learning performances of the honey bee Apis mellifera L. (Hymenoptera, Apidae)?

PubMed

Ramirez-Romero, R; Desneux, N; Decourtye, A; Chaffiol, A; Pham-Delègue, M H

2008-06-01

Genetically modified Bt crops are increasingly used worldwide but side effects and especially sublethal effects on beneficial insects remain poorly studied. Honey bees are beneficial insects for natural and cultivated ecosystems through pollination. The goal of the present study was to assess potential effects of two concentrations of Cry1Ab protein (3 and 5000 ppb) on young adult honey bees. Following a complementary bioassay, our experiments evaluated effects of the Cry1Ab on three major life traits of young adult honey bees: (a) survival of honey bees during sub-chronic exposure to Cry1Ab, (b) feeding behaviour, and (c) learning performance at the time that honey bees become foragers. The latter effect was tested using the proboscis extension reflex (PER) procedure. The same effects were also tested using a chemical pesticide, imidacloprid, as positive reference. The tested concentrations of Cry1Ab protein did not cause lethal effects on honey bees. However, honey bee feeding behaviour was affected when exposed to the highest concentration of Cry1Ab protein, with honey bees taking longer to imbibe the contaminated syrup. Moreover, honey bees exposed to 5000 ppb of Cry1Ab had disturbed learning performances. Honey bees continued to respond to a conditioned odour even in the absence of a food reward. Our results show that transgenic crops expressing Cry1Ab protein at 5000 ppb may affect food consumption or learning processes and thereby may impact honey bee foraging efficiency. The implications of these results are discussed in terms of risks of transgenic Bt crops for honey bees.

New insights on emergence from the perspective of weak values and dynamical non-locality

NASA Astrophysics Data System (ADS)

Tollaksen, Jeff

2014-04-01

In this article, we will examine new fundamental aspects of "emergence" and "information" using novel approaches to quantum mechanics which originated from the group around Aharonov. The two-state vector formalism provides a complete description of pre- and post-selected quantum systems and has uncovered a host of new quantum phenomena which were previously hidden. The most important feature is that any weak coupling to a pre- and post-selected system is effectively a coupling to a "weak value" which is given by a simple expression depending on the two-state vector. In particular, weak values, are the outcomes of so called "weak measurements" which have recently become a very powerful tool for ultra-sensitive measurements. Using weak values, we will show how to separate a particle from its properties, not unlike the Cheshire cat story: "Well! I've often seen a cat without a grin," thought Alice; "but a grin without a cat! It's the most curious thing I ever saw in all my life!" Next, we address the question whether the physics on different scales "emerges" from quantum mechanics or whether the laws of physics at those scales are fundamental. We show that the classical limit of quantum mechanics is a far more complicated issue; it is in fact dramatically more involved and it requires a complete revision of all our intuitions. The revised intuitions can then serve as a guide to finding novel quantum effects. Next we show that novel experimental aspects of contextuality can be demonstrated with weak measurements and these suggest new restrictions on hidden variable approaches. Next we emphasize that the most important implication of the Aharonov-Bohm effect is the existence of non-local interactions which do not violate causality. Finally, we review some generalizations of quantum mechanics and their implications for "emergence" and "information." First, we review an alternative approach to quantum evolution in which each moment of time is viewed as a new "universe

Substituent Inductive Effects on the Electrochemical Oxidation of Flavonoids Studied by Square Wave Voltammetry and Ab Initio Calculations.

PubMed

Arroyo-Currás, Netzahualcóyotl; Rosas-García, Víctor M; Videa, Marcelo

2016-10-27

Flavonoids are natural products commonly found in the human diet that show antioxidant, anti-inflammatory and anti-hepatotoxic activities. These nutraceutical properties may relate to the electrochemical activity of flavonoids. To increase the understanding of structure-electrochemical activity relations and the inductive effects that OH substituents have on the redox potential of flavonoids, we carried out square-wave voltammetry experiments and ab initio calculations of eight flavonoids selected following a systematic variation in the number of hydroxyl substituents and their location on the flavan backbone: three flavonols, three anthocyanidins, one anthocyanin and the flavonoid backbone flavone. We compared the effect that the number of -OH groups in the ring B of flavan has on the oxidation potential of the flavonoids considered, finding linear correlations for both flavonols and anthocyanidins ( R 2 = 0.98 ). We analyzed the effects that position and number of -OH substituents have on electron density distributions via ab initio quantum chemical calculations. We present direct correlations between structural features and oxidation potentials that provide a deeper insight into the redox chemistry of these molecules.

SdAb heterodimer formation using leucine zippers

NASA Astrophysics Data System (ADS)

Goldman, Ellen R.; Anderson, George P.; Brozozog-Lee, P. Audrey; Zabetakis, Dan

2013-05-01

Single domain antibodies (sdAb) are variable domains cloned from camel, llama, or shark heavy chain only antibodies, and are among the smallest known naturally derived antigen binding fragments. SdAb derived from immunized llamas are able to bind antigens with high affinity, and most are capable of refolding after heat or chemical denaturation to bind antigen again. We hypothesized that the ability to produce heterodimeric sdAb would enable reagents with the robust characteristics of component sdAb, but with dramatically improved overall affinity through increased avidity. Previously we had constructed multimeric sdAb by genetically linking sdAb that bind non-overlapping epitopes on the toxin, ricin. In this work we explored a more flexible approach; the construction of multivalent binding reagents using multimerization domains. We expressed anti-ricin sdAb that recognize different epitopes on the toxin as fusions with differently charged leucine zippers. When the initially produced homodimers are mixed the leucine zipper domains will pair to produce heterodimers. We used fluorescence resonance energy transfer to confirm heterodimer formation. Surface plasmon resonance, circular dichroism, enzyme linked immunosorbent assays, and fluid array assays were used to characterize the multimer constructs, and evaluate their utility in toxin detection.

Effective prophylaxis of influenza A virus pneumonia in mice by topical passive immunotherapy with polyvalent human immunoglobulins or F(ab')2 fragments.

PubMed

Ramisse, F; Deramoudt, F X; Szatanik, M; Bianchi, A; Binder, P; Hannoun, C; Alonso, J M

1998-03-01

The effectiveness of polyvalent plasma-derived human immunoglobulins (IVIG) in passive immunotherapy of influenza virus pneumonia was assessed, using the Strain Scotland (A/Scotland/74 (H3N2)) adapted to BALB/c mice by repeated lung passages. Haemagglutinin antibodies in two batches of IVIG at 10 mg/ml had a titre of 1/16. Intravenous injection of 1000-5000 microg of IVIG, 3 h after infection, gave 60-70% protection, whereas intranasal injection of 25-50 microg protected 90% of mice infected with a lethal dose of influenza virus. F(ab')2 fragments were at least as protective as intact IVIG, suggesting that complement or Fcgamma receptor-bearing cells were not required. Topical passive immunotherapy with IVIG or F(ab')2 gave protection up to 8 h after infection, but not at 24 h, suggesting that anti-influenza A antibodies in IVIG, delivered locally, are only effective at early stages of the infectious process. The potential value of topical administration of IVIG or F(ab')2 fragments for influenza A pneumonia prophylaxis was further demonstrated by the protective effects of their intranasal administration 24 h before challenge.

Quantum ring-polymer contraction method: Including nuclear quantum effects at no additional computational cost in comparison to ab initio molecular dynamics

NASA Astrophysics Data System (ADS)

John, Christopher; Spura, Thomas; Habershon, Scott; Kühne, Thomas D.

2016-04-01

We present a simple and accurate computational method which facilitates ab initio path-integral molecular dynamics simulations, where the quantum-mechanical nature of the nuclei is explicitly taken into account, at essentially no additional computational cost in comparison to the corresponding calculation using classical nuclei. The predictive power of the proposed quantum ring-polymer contraction method is demonstrated by computing various static and dynamic properties of liquid water at ambient conditions using density functional theory. This development will enable routine inclusion of nuclear quantum effects in ab initio molecular dynamics simulations of condensed-phase systems.

40 CFR 174.506 - Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of...

Code of Federal Regulations, 2010 CFR

2010-07-01

... Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. 174.506 Section 174.506... thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. Residues of Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn are exempted from the requirement of a...

40 CFR 174.506 - Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of...

Code of Federal Regulations, 2011 CFR

2011-07-01

... Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. 174.506 Section 174.506... thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. Residues of Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn are exempted from the requirement of a...

40 CFR 174.506 - Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of...

Code of Federal Regulations, 2013 CFR

2013-07-01

... Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. 174.506 Section 174.506... thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. Residues of Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn are exempted from the requirement of a...

40 CFR 174.506 - Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of...

Code of Federal Regulations, 2014 CFR

2014-07-01

... Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. 174.506 Section 174.506... thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. Residues of Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn are exempted from the requirement of a...

40 CFR 174.506 - Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of...

Code of Federal Regulations, 2012 CFR

2012-07-01

... Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. 174.506 Section 174.506... thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn; exemption from the requirement of a tolerance. Residues of Bacillus thuringiensis Cry34Ab1 and Cry35Ab1 proteins in corn are exempted from the requirement of a...

Thermal behavior of vehicle plastic blends contained acrylonitrile-butadiene-styrene (ABS) in pyrolysis using TG-FTIR.

PubMed

Liu, Guicai; Liao, Yanfen; Ma, Xiaoqian

2017-03-01

As important plastic blends in End-of-Life vehicles (ELV), pyrolysis profiles of ABS/PVC, ABS/PA6 and ABS/PC were investigated using thermogravimetric-Fourier transform infrared spectrometer (TG-FTIR). Also, CaCO 3 was added as plastic filler to discuss its effects on the pyrolysis of these plastics. The results showed that the interaction between ABS and PVC made PVC pyrolysis earlier and HCl emission slightly accelerated. The mixing of ABS and PA6 made their decomposition temperature closer, and ketones in PA6 pyrolysis products were reduced. The presence of ABS made PC pyrolysis earlier, and phenyl compounds in PC pyrolysis products could be transferred into alcohol or H 2 O. The interaction between ABS and other polymers in pyrolysis could be attributed to the intermolecular radical transfer, and free radicals from the polymer firstly decomposed led to a fast initiation the decomposition of the other polymer. As plastic filler, CaCO 3 promoted the thermal decomposition of PA6 and PC, and had no obvious effects on ABS and PVC pyrolysis process. Also, CaCO 3 made the pyrolysis products from PA6 and PC further decomposed into small-molecule compounds like CO 2 . The kinetics analysis showed that isoconversional method like Starink method was more suitable for these polymer blends. Starink method showed the average activation energy of ABS50/PVC50, ABS50/PA50 and ABS50/PC50 was 186.63kJ/mol, 239.61kJ/mol and 248.95kJ/mol, respectively, and the interaction among them could be reflected by the activation energy variation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Antibiotic stewardship through the EU project "ABS International".

PubMed

Allerberger, Franz; Frank, Annegret; Gareis, Roland

2008-01-01

The increasing problem of antimicrobial resistance requires implementation of antibiotic stewardship (ABS) programs. The project "ABS International--implementing antibiotic strategies for appropriate use of antibiotics in hospitals in member states of the European Union" was started in September 2006 in Austria, Belgium, the Czech Republic, Germany, Hungary, Italy, Poland, Slovenia and Slovakia. A training program for national ABS trainers was prepared and standard templates for ABS tools (antibiotic list, guides for antibiotic treatment and surgical prophylaxis, antibiotic-related organization) and valid process measures, as well as quality indicators for antibiotic use were developed. Specific ABS tools are being implemented in up to five healthcare facilities in each country. Although ABS International clearly focuses on healthcare institutions, future antimicrobial stewardship programs must also cover public education and antibiotic prescribing in primary care.

Pharmaco-toxicological effects of the novel third-generation fluorinate synthetic cannabinoids, 5F-ADBINACA, AB-FUBINACA, and STS-135 in mice. In vitro and in vivo studies.

PubMed

Canazza, Isabella; Ossato, Andrea; Vincenzi, Fabrizio; Gregori, Adolfo; Di Rosa, Fabiana; Nigro, Federica; Rimessi, Alessandro; Pinton, Paolo; Varani, Katia; Borea, Pier Andrea; Marti, Matteo

2017-05-01

5F-ADBINACA, AB-FUBINACA, and STS-135 are 3 novel third-generation fluorinate synthetic cannabinoids that are illegally marketed as incense, herbal preparations, or research chemicals for their psychoactive cannabis-like effects. The present study aims at investigating the in vitro and in vivo pharmacological activity of 5F-ADBINACA, AB-FUBINACA, and STS-135 in male CD-1 mice, comparing their in vivo effects with those caused by the administration of Δ 9 -THC and JWH-018. In vitro competition binding experiments revealed a nanomolar affinity and potency of the 5F-ADBINACA, AB-FUBINACA, and STS-135 on mouse and human CB 1 and CB 2 receptors. Moreover, these synthetic cannabinoids induced neurotoxicity in murine neuro-2a cells. In vivo studies showed that 5F-ADBINACA, AB-FUBINACA, and STS-135 induced hypothermia; increased pain threshold to both noxious mechanical and thermal stimuli; caused catalepsy; reduced motor activity; impaired sensorimotor responses (visual, acoustic, and tactile); caused seizures, myoclonia, and hyperreflexia; and promoted aggressiveness in mice. Behavioral and neurological effects were fully prevented by the selective CB 1 receptor antagonist/inverse agonist AM 251. Differently, the visual sensory response induced by STS-135 was only partly prevented by the AM 251, suggesting a CB 1 -independent mechanism. For the first time, the present study demonstrates the pharmaco-toxicological effects induced by the administration of 5F-ADBINACA, AB-FUBINACA, and STS-135 in mice and suggests their possible detrimental effects on human health. Copyright © 2017 John Wiley & Sons, Ltd.

Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces

DOE PAGES

Herron, Jeffrey A.; Morikawa, Yoshitada; Mavrikakis, Manos

2016-08-08

Using ab initio molecular dynamics (as implemented in periodic, self-consistent (GGA-PBE) density functional theory (DFT) we investigated the mechanism of methanol electro-oxidation on Pt(111). We investigated the role of solvation and electrode potential on the energetics of the first proton transfer step, methanol electro-oxidation to methoxy (CH 3O) or hydroxymethyl (CH 2OH). The results show that solvation weakens the adsorption of methoxy to uncharged Pt(111), while the binding energy of methanol and hydroxymethyl are not significantly affected. The free energies of activation for breaking the C-H and O-H bonds in methanol were calculated through a Blue Moon Ensemble using constrainedmore » ab initio molecular dynamics. Calculated barriers for these elementary steps on unsolvated, uncharged Pt(111) are similar to results for climbing-image nudged elastic band calculations from the literature. Solvation reduces the barrier for both C-H and O-H bond activation steps with respect to their vapor phase values, though the effect is more pronounced for C-H bond activation due to less disruption of the hydrogen-bond network. The calculated activation energy barriers show that breaking the C-H bond of methanol is more facile than the O-H bond on solvated negatively biased, or uncharged Pt(111). Furthermore, with positive bias, O-H bond activation is enhanced, becoming slightly more facile than C-H bond activation.« less

Improvements to a five-phase ABS algorithm for experimental validation

NASA Astrophysics Data System (ADS)

Gerard, Mathieu; Pasillas-Lépine, William; de Vries, Edwin; Verhaegen, Michel

2012-10-01

The anti-lock braking system (ABS) is the most important active safety system for passenger cars. Unfortunately, the literature is not really precise about its description, stability and performance. This research improves a five-phase hybrid ABS control algorithm based on wheel deceleration [W. Pasillas-Lépine, Hybrid modeling and limit cycle analysis for a class of five-phase anti-lock brake algorithms, Veh. Syst. Dyn. 44 (2006), pp. 173-188] and validates it on a tyre-in-the-loop laboratory facility. Five relevant effects are modelled so that the simulation matches the reality: oscillations in measurements, wheel acceleration reconstruction, brake pressure dynamics, brake efficiency changes and tyre relaxation. The time delays in measurement and actuation have been identified as the main difficulty for the initial algorithm to work in practice. Three methods are proposed in order to deal with these delays. It is verified that the ABS limit cycles encircle the optimal braking point, without assuming any tyre parameter being a priori known. The ABS algorithm is compared with the commercial algorithm developed by Bosch.

Production and characterization of monoclonal antibodies (mAbs) against human serum albumin (HSA) for the development of an immunoaffinity system with oriented anti-HSA mAbs as immobilized ligand.

PubMed

Rajak, Poonam; Vijayalakshmi, M A; Jayaprakash, N S

2013-05-05

Proteins present in human serum are of immense importance in the field of biomarker discovery. But, the presence of high-abundant proteins like albumin makes the analysis more challenging because of masking effect on low-abundant proteins. Therefore, removal of albumin using highly specific monoclonal antibodies (mAbs) can potentiate the discovery of low-abundant proteins. In the present study, mAbs against human serum albumin (HSA) were developed and integrated in to an immunoaffinity based system for specific removal of albumin from the serum. Hybridomas were obtained by fusion of Sp2/0 mouse myeloma cells with spleen cells from the mouse immunized with HSA. Five clones (AHSA1-5) producing mAbs specific to HSA were established and characterized by enzyme linked immunosorbent assay (ELISA) and immunoblotting for specificity, sensitivity and affinity in terms of antigen binding. The mAbs were able to bind to both native albumin as well as its glycated isoform. Reactivity of mAbs with different mammalian sera was tested. The affinity constant of the mAbs ranged from 10(8) to 10(9)M(-1). An approach based on oriented immobilization was followed to immobilize purified anti-HSA mAbs on hydrazine activated agarose gel and the dynamic binding capacity of the column was determined. Copyright © 2013 Elsevier B.V. All rights reserved.

Overexpression of the ABC transporter AvtAB increases avermectin production in Streptomyces avermitilis.

PubMed

Qiu, Jingfan; Zhuo, Ying; Zhu, Dongqing; Zhou, Xiufen; Zhang, Lixin; Bai, Linquan; Deng, Zixin

2011-10-01

Avermectins are 16-membered macrocyclic polyketides with potent antiparasitic activities, produced by Streptomyces avermitilis. Upstream of the avermectin biosynthetic gene cluster, there is the avtAB operon encoding the ABC transporter AvtAB, which is highly homologous to the mammalian multidrug efflux pump P-glycoprotein (Pgp). Inactivation of avtAB had no effect, but increasing the concentration of avtAB mRNA 30-500-fold, using a multi-copy plasmid in S. avermitilis, enhanced avermectin production about two-fold both in the wild-type and in a high-yield producer strain on agar plates. In liquid industrial fermentation medium, the overall productivity of avermectin B1a in the engineered high-yield producer was improved for about 50%, from 3.3 to 4.8 g/l. In liquid YMG medium, moreover, the ratio of intracellular to extracellular accumulation of avermectin B1a was dropped from 6:1 to 4.5:1 in response to multiple copies of avtAB. Additionally, the overexpression of avtAB did not cause any increased expression of the avermectin biosynthetic genes through RT-PCR analysis. We propose that the AvtAB transporter exports avermectin, and thus reduces the feedback inhibition on avermectin production inside the cell. This strategy may be useful for enhancing the production of other antibiotics.

Role of EfrAB efflux pump in biocide tolerance and antibiotic resistance of Enterococcus faecalis and Enterococcus faecium isolated from traditional fermented foods and the effect of EDTA as EfrAB inhibitor.

PubMed

Lavilla Lerma, Leyre; Benomar, Nabil; Valenzuela, Antonio Sánchez; Casado Muñoz, María del Carmen; Gálvez, Antonio; Abriouel, Hikmate

2014-12-01

Enterococcus faecalis and Enterococcus faecium isolated from various traditional fermented foods of both animal and vegetable origins have shown multidrug resistance to several antibiotics and tolerance to biocides. Reduced susceptibility was intra and inter-species dependent and was due to specific and unspecific mechanisms such as efflux pumps. EfrAB, a heterodimeric ABC transporter efflux pump, was detected in 100% of multidrug resistant (MDR) E. faecalis strains and only in 12% of MDR E. faecium strains. EfrAB expression was induced by half of minimum inhibitory concentration (MIC) of gentamicin, streptomycin and chloramphenicol. However, expression of efrA and efrB genes was highly dependent on the strain tested and on the antimicrobial used. Our results indicated that 3 mM EDTA highly reduced the MICs of almost all drugs tested. Nevertheless, the higher reductions (>8 folds) were obtained with gentamicin, streptomycin, chlorhexidine and triclosan. Reductions of MICs were correlated with down-regulation of EfrAB expression (10-140 folds) in all three MDR enterococci strains. This is the first report describing the role of EfrAB in the efflux of antibiotics and biocides which reflect also the importance of EfrAB in multidrug resistance in enterococci. EDTA used at low concentration as food preservative could be one of the best choices to prevent spread of multidrug resistant enterococci throughout food chain by decreasing EfrAB expression. EfrAB could be an attractive target not only in enterococci present in food matrix but also those causing infections as well by using EDTA as therapeutic agent in combination with low doses of antibiotics. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effects of Cry1Ab Transgenic Maize on Lifecycle and Biomarker Responses of the Earthworm, Eisenia Andrei

PubMed Central

van der Merwe, Frances; Bezuidenhout, Carlos; van den Berg, Johnnie; Maboeta, Mark

2012-01-01

A 28-day study was conducted to determine the effects of the Bacillus thuringiensis Cry1Ab toxin on the earthworm Eisenia andrei. Previously, investigations have been limited to life-cycle level effects of this protein on earthworms, and mostly on E. fetida. In this study several endpoints were compared which included biomass changes, cocoon production, hatching success, a cellular metal-stress biomarker (Neutral Red Retention Time; NRRT) and potential genotoxic effects in terms of Randomly Amplified Polymorphic DNA sequences (RAPDs). NRRT results indicated no differences between treatments (p > 0.36), and NRRT remained the same for both treatments at different times during the experiment (p = 0.18). Likewise, no significant differences were found for cocoon production (p = 0.32) or hatching success (p = 0.29). Conversely, biomass data indicated a significant difference between the control treatment and the Bt treatment from the second week onwards (p < 0.001), with the Bt treatment losing significantly more weight than the isoline treatment. Possible confounding factors were identified that might have affected the differences in weight loss between groups. From the RAPD profiles no conclusive data were obtained that could link observed genetic variation to exposure of E. andrei to Cry1Ab proteins produced by Bt maize. PMID:23235452

Sorbitol crystallization-induced aggregation in frozen mAb formulations.

PubMed

Piedmonte, Deirdre Murphy; Hair, Alison; Baker, Priti; Brych, Lejla; Nagapudi, Karthik; Lin, Hong; Cao, Wenjin; Hershenson, Susan; Ratnaswamy, Gayathri

2015-02-01

Sorbitol crystallization-induced aggregation of mAbs in the frozen state was evaluated. The effect of protein aggregation resulting from sorbitol crystallization was measured as a function of formulation variables such as protein concentration and pH. Long-term studies were performed on both IgG1 and IgG2 mAbs over the protein concentration range of 0.1-120 mg/mL. Protein aggregation was measured by size-exclusion HPLC (SE-HPLC) and further characterized by capillary-electrophoresis SDS. Sorbitol crystallization was monitored and characterized by subambient differential scanning calorimetry and X-ray diffraction. Aggregation due to sorbitol crystallization is inversely proportional to both protein concentration and formulation pH. At high protein concentrations, sorbitol crystallization was suppressed, and minimal aggregation by SE-HPLC resulted, presumably because of self-stabilization of the mAbs. The glass transition temperature (Tg ') and fragility index measurements were made to assess the influence of molecular mobility on the crystallization of sorbitol. Tg ' increased with increasing protein concentration for both mAbs. The fragility index decreased with increasing protein concentration, suggesting that it is increasingly difficult for sorbitol to crystallize at high protein concentrations. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Linkage of interactions in sickle hemoglobin fiber assembly: inhibitory effect emanating from mutations in the AB region of the alpha-chain is annulled by a mutation at its EF corner.

PubMed

Sudha, Rajamani; Anantharaman, Lavanya; Sivaram, Mylavarapu V S; Mirsamadi, Neda; Choudhury, Devapriya; Lohiya, Nirmal K; Gupta, Rasik B; Roy, Rajendra P

2004-05-07

The AB and GH regions of the alpha-chain are located in spatial proximity and contain a cluster of intermolecular contact residues of the sickle hemoglobin (HbS) fiber. We have examined the role of dynamics of AB/GH region on HbS polymerization through simultaneous replacement of non-contact Ala(19) and Ala(21) of the AB corner with more flexible Gly or rigid alpha-aminoisobutyric acid (Aib) residues. The polymerization behavior of HbS with Aib substitutions was similar to the native HbS. In contrast, Gly substitutions inhibited HbS polymerization. Molecular dynamics simulation studies of alpha-chains indicated that coordinated motion of AB and GH region residues present in native (Ala) as well as in Aib mutant was disrupted in the Gly mutant. The inhibitory effect due to Gly substitutions was further explored in triple mutants that included mutation of an inter-doublestrand contact (alphaAsn(78) --> His or Gln) at the EF corner. Although the inhibitory effect of Gly substitutions in the triple mutant was unaffected in the presence of alphaGln(78), His at this site almost abrogated its inhibitory potential. The polymerization studies of point mutants (alphaGln(78) --> His) indicated that the inhibitory effect due to Gly substitutions in the triple mutant was synergistically compensated for by the polymerization-enhancing activity of His(78). Similar synergistic coupling, between alphaHis(78) and an intra-double-strand contact point (alpha16) mutation located in the AB region, was also observed. Thus, two conclusions are made: (i) Gly mutations at the AB corner inhibit HbS polymerization by perturbing the dynamics of the AB/GH region, and (ii) perturbations of AB region (through changes in dynamics of the AB/GH region or abolition of a specific fiber contact site) that influence HbS polymerization do so in concert with alpha78 site at the EF corner. The overall results provide insights about the interaction-linkage between distant regions of the HbS tetramer in

Physics of the intermediate layer between a plasma and a collisionless sheath and mathematical meaning of the Bohm criterion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Almeida, N. A.; Benilov, M. S.

A transformation of the ion momentum equation simplifies a mathematical description of the transition layer between a quasi-neutral plasma and a collisionless sheath and clearly reveals the physics involved. Balance of forces acting on the ion fluid is delicate in the vicinity of the sonic point and weak effects come into play. For this reason, the passage of the ion fluid through the sonic point, which occurs in the transition layer, is governed not only by inertia and electrostatic force but also by space charge and ion-atom collisions and/or ionization. Occurrence of different scenarios of asymptotic matching in the plasma-sheathmore » transition is analyzed by means of simple mathematical examples, asymptotic estimates, and numerical calculations. In the case of a collisionless sheath, the ion speed distribution plotted on the logarithmic scale reveals a plateau in the intermediate region between the sheath and the presheath. The value corresponding to this plateau has the meaning of speed with which ions leave the presheath and enter the sheath; the Bohm speed. The plateau is pronounced reasonably well provided that the ratio of the Debye length to the ion mean free path is of the order of 10{sup -3} or smaller. There is no such plateau if the sheath is collisional and hence no sense in talking of a speed with which ions enter the sheath.« less

The activin-βA/BMP-2 chimera AB204 is a strong stimulator of adipogenesis.

PubMed

Kim, Meejung; Kim, Jong In; Kim, Jae Bum; Choe, Senyon

2017-05-01

Several of the bone morphogenetic proteins (BMPs) have been reported to induce white as well as brown adipogenesis. Here, we characterized the adipogenic potential of AB204, a recombinant chimeric protein of activin-βA and BMP-2, in in vitro, ex vivo and in vivo settings. BMP-2 is generally known to promote adipogenesis. When compared with BMP-2, which previously showed varying degrees of adipogenesis, AB204 displayed superior in vitro adipogenic differentiation of mouse 3 T3-L1 pre-adipocytes and human adipose-derived stem cells (hASCs). Surprisingly, implantation of hASCs, preconditioned with AB204 for as short a time as 48 h, into the subcutaneous space of athymic nude mice effectively produced fat pads, but not with BMP-2. When BMP-2 and AB204 were injected intraperitoneally, AB204 promoted dramatic systemic adipogenesis of C57BL/6 mice on a high-fat diet very effectively. The results implicate the novel clinical potential of AB204, including induction of fat tissue ex vivo or in vivo for tissue re-engineering and regenerative medicinal purposes, more than any known natural protein ligand. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Substrate Screening Effects in ab initio Many-body Green's Function Calculations of Doped Graphene on SiC

NASA Astrophysics Data System (ADS)

Vigil-Fowler, Derek; Lischner, Johannes; Louie, Steven

2013-03-01

Understanding many-electron interaction effects and the influence of the substrate in graphene-on-substrate systems is of great theoretical and practical interest. Thus far, both model Hamiltonian and ab initio GW calculations for the quasiparticle properties of such systems have employed crude models for the effect of the substrate, often approximating the complicated substrate dielectric matrix by a single constant. We develop a method in which the spatially-dependent dielectric matrix of the substrate (e.g., SiC) is incorporated into that of doped graphene to obtain an accurate total dielectric matrix. We present ab initio GW + cumulant expansion calculations, showing that both the cumulant expansion (to include higher-order electron correlations) and a proper account of the substrate screening are needed to achieve agreement with features seen in ARPES. We discuss how this methodology could be used in other systems. This work was supported by NSF Grant No. DMR10-1006184 and U.S. DOE Contract No. DE-AC02-05CH11231. Computational resources have been provided by the NERSC and NICS. D.V-F. acknowledges funding from the DOD's NDSEG fellowship.

Protective mAbs and Cross-Reactive mAbs Raised by Immunization with Engineered Marburg Virus GPs.

PubMed

Fusco, Marnie L; Hashiguchi, Takao; Cassan, Robyn; Biggins, Julia E; Murin, Charles D; Warfield, Kelly L; Li, Sheng; Holtsberg, Frederick W; Shulenin, Sergey; Vu, Hong; Olinger, Gene G; Kim, Do H; Whaley, Kevin J; Zeitlin, Larry; Ward, Andrew B; Nykiforuk, Cory; Aman, M Javad; Berry, Jody D; Berry, Jody; Saphire, Erica Ollmann

2015-06-01

The filoviruses, which include the marburg- and ebolaviruses, have caused multiple outbreaks among humans this decade. Antibodies against the filovirus surface glycoprotein (GP) have been shown to provide life-saving therapy in nonhuman primates, but such antibodies are generally virus-specific. Many monoclonal antibodies (mAbs) have been described against Ebola virus. In contrast, relatively few have been described against Marburg virus. Here we present ten mAbs elicited by immunization of mice using recombinant mucin-deleted GPs from different Marburg virus (MARV) strains. Surprisingly, two of the mAbs raised against MARV GP also cross-react with the mucin-deleted GP cores of all tested ebolaviruses (Ebola, Sudan, Bundibugyo, Reston), but these epitopes are masked differently by the mucin-like domains themselves. The most efficacious mAbs in this panel were found to recognize a novel "wing" feature on the GP2 subunit that is unique to Marburg and does not exist in Ebola. Two of these anti-wing antibodies confer 90 and 100% protection, respectively, one hour post-exposure in mice challenged with MARV.

A walk through the approximations of ab initio multiple spawning

NASA Astrophysics Data System (ADS)

Mignolet, Benoit; Curchod, Basile F. E.

2018-04-01

Full multiple spawning offers an in principle exact framework for excited-state dynamics, where nuclear wavefunctions in different electronic states are represented by a set of coupled trajectory basis functions that follow classical trajectories. The couplings between trajectory basis functions can be approximated to treat molecular systems, leading to the ab initio multiple spawning method which has been successfully employed to study the photochemistry and photophysics of several molecules. However, a detailed investigation of its approximations and their consequences is currently missing in the literature. In this work, we simulate the explicit photoexcitation and subsequent excited-state dynamics of a simple system, LiH, and we analyze (i) the effect of the ab initio multiple spawning approximations on different observables and (ii) the convergence of the ab initio multiple spawning results towards numerically exact quantum dynamics upon a progressive relaxation of these approximations. We show that, despite the crude character of the approximations underlying ab initio multiple spawning for this low-dimensional system, the qualitative excited-state dynamics is adequately captured, and affordable corrections can further be applied to ameliorate the coupling between trajectory basis functions.

A walk through the approximations of ab initio multiple spawning.

PubMed

Mignolet, Benoit; Curchod, Basile F E

2018-04-07

Full multiple spawning offers an in principle exact framework for excited-state dynamics, where nuclear wavefunctions in different electronic states are represented by a set of coupled trajectory basis functions that follow classical trajectories. The couplings between trajectory basis functions can be approximated to treat molecular systems, leading to the ab initio multiple spawning method which has been successfully employed to study the photochemistry and photophysics of several molecules. However, a detailed investigation of its approximations and their consequences is currently missing in the literature. In this work, we simulate the explicit photoexcitation and subsequent excited-state dynamics of a simple system, LiH, and we analyze (i) the effect of the ab initio multiple spawning approximations on different observables and (ii) the convergence of the ab initio multiple spawning results towards numerically exact quantum dynamics upon a progressive relaxation of these approximations. We show that, despite the crude character of the approximations underlying ab initio multiple spawning for this low-dimensional system, the qualitative excited-state dynamics is adequately captured, and affordable corrections can further be applied to ameliorate the coupling between trajectory basis functions.

Modeling study of the ABS relay valve

NASA Astrophysics Data System (ADS)

Lei, Ming; Lin, Min; Guo, Bin; Luo, Zai; Xu, Weidong

2011-05-01

The ABS (anti-lock braking system) relay valve is the key component of anti-lock braking system in most commercial vehicles such as trucks, tractor-trailers, etc. In this paper, structure of ABS relay valve and its work theory were analyzed. Then a mathematical model of ABS relay valve, which was investigated by dividing into electronic part, magnetic part, pneumatic part and mechanical part, was set up. The displacement of spools and the response of pressure increasing, holding, releasing of ABS relay valve were simulated and analyzed under conditions of control pressure 500 KPa, braking pressure 600 KPa, atmospheric pressure 100 KPa and air temperature 310 K. Thisarticle provides reliable theory for improving the performance and efficiency of anti-lock braking system of vehicles.

Quasi-probabilities in conditioned quantum measurement and a geometric/statistical interpretation of Aharonov's weak value

NASA Astrophysics Data System (ADS)

Lee, Jaeha; Tsutsui, Izumi

2017-05-01

We show that the joint behavior of an arbitrary pair of (generally noncommuting) quantum observables can be described by quasi-probabilities, which are an extended version of the standard probabilities used for describing the outcome of measurement for a single observable. The physical situations that require these quasi-probabilities arise when one considers quantum measurement of an observable conditioned by some other variable, with the notable example being the weak measurement employed to obtain Aharonov's weak value. Specifically, we present a general prescription for the construction of quasi-joint probability (QJP) distributions associated with a given combination of observables. These QJP distributions are introduced in two complementary approaches: one from a bottom-up, strictly operational construction realized by examining the mathematical framework of the conditioned measurement scheme, and the other from a top-down viewpoint realized by applying the results of the spectral theorem for normal operators and their Fourier transforms. It is then revealed that, for a pair of simultaneously measurable observables, the QJP distribution reduces to the unique standard joint probability distribution of the pair, whereas for a noncommuting pair there exists an inherent indefiniteness in the choice of such QJP distributions, admitting a multitude of candidates that may equally be used for describing the joint behavior of the pair. In the course of our argument, we find that the QJP distributions furnish the space of operators in the underlying Hilbert space with their characteristic geometric structures such that the orthogonal projections and inner products of observables can be given statistical interpretations as, respectively, “conditionings” and “correlations”. The weak value Aw for an observable A is then given a geometric/statistical interpretation as either the orthogonal projection of A onto the subspace generated by another observable B, or

Predicting vapor-liquid phase equilibria with augmented ab initio interatomic potentials

NASA Astrophysics Data System (ADS)

Vlasiuk, Maryna; Sadus, Richard J.

2017-06-01

The ability of ab initio interatomic potentials to accurately predict vapor-liquid phase equilibria is investigated. Monte Carlo simulations are reported for the vapor-liquid equilibria of argon and krypton using recently developed accurate ab initio interatomic potentials. Seventeen interatomic potentials are studied, formulated from different combinations of two-body plus three-body terms. The simulation results are compared to either experimental or reference data for conditions ranging from the triple point to the critical point. It is demonstrated that the use of ab initio potentials enables systematic improvements to the accuracy of predictions via the addition of theoretically based terms. The contribution of three-body interactions is accounted for using the Axilrod-Teller-Muto plus other multipole contributions and the effective Marcelli-Wang-Sadus potentials. The results indicate that the predictive ability of recent interatomic potentials, obtained from quantum chemical calculations, is comparable to that of accurate empirical models. It is demonstrated that the Marcelli-Wang-Sadus potential can be used in combination with accurate two-body ab initio models for the computationally inexpensive and accurate estimation of vapor-liquid phase equilibria.

Predicting vapor-liquid phase equilibria with augmented ab initio interatomic potentials.

PubMed

Vlasiuk, Maryna; Sadus, Richard J

2017-06-28

The ability of ab initio interatomic potentials to accurately predict vapor-liquid phase equilibria is investigated. Monte Carlo simulations are reported for the vapor-liquid equilibria of argon and krypton using recently developed accurate ab initio interatomic potentials. Seventeen interatomic potentials are studied, formulated from different combinations of two-body plus three-body terms. The simulation results are compared to either experimental or reference data for conditions ranging from the triple point to the critical point. It is demonstrated that the use of ab initio potentials enables systematic improvements to the accuracy of predictions via the addition of theoretically based terms. The contribution of three-body interactions is accounted for using the Axilrod-Teller-Muto plus other multipole contributions and the effective Marcelli-Wang-Sadus potentials. The results indicate that the predictive ability of recent interatomic potentials, obtained from quantum chemical calculations, is comparable to that of accurate empirical models. It is demonstrated that the Marcelli-Wang-Sadus potential can be used in combination with accurate two-body ab initio models for the computationally inexpensive and accurate estimation of vapor-liquid phase equilibria.

Ab interno trabeculectomy: ultrastructural evidence and early tissue response in a human eye.

PubMed

Ferrari, Ettore; Ortolani, Fulvia; Petrelli, Lucia; Contin, Magali; Pognuz, Derri Roman; Marchini, Maurizio; Bandello, Francesco

2007-10-01

To report the results of ultrastructural analysis of the postoperative effects of ab interno trabeculectomy in a human eye. Department of Ophthalmology, Palmanova Hospital, Palmanova, Udine, Italy. A 60-year-old woman with cataract and glaucoma had enucleation for a choroidal melanoma 10 days after ab interno trabeculectomy combined with phacoemulsification. A second ab interno trabeculectomy was performed after enucleation to evaluate the outcomes of the previous trabeculectomy. Light and transmission electron microscopy analyses were performed on samples excised from areas (1) not subjected to a procedure (control samples), (2) that had ab interno trabeculectomy before enucleation, and (3) that had ab interno trabeculectomy immediately after enucleation. Control samples showed normal trabecular features. Semithin sections of all ab interno trabeculectomy samples showed full-thickness removal of trabeculum segments, with Schlemm's canal lumen opening into the anterior chamber and apparent preservation of the adjacent structures. On ultrathin sections of samples that had ab interno trabeculectomy before enucleation, the endothelium lining the outer wall of Schlemm's canal and other angle components showed intact ultrastructural features. In trabecular beams that were not removed, the extracellular matrix appeared to have maintained its fine texture and was free of activated fibroblasts or leucocyte infiltrates. Observations confirm that ab interno trabeculectomy causes direct communication between Schlemm's canal lumen and the anterior chamber in vivo and immediately after enucleation during the early postoperative period. The absence of an evident inflammatory reaction in the examined case should be considered with caution because of possible tumor-induced immune suppression.

Linear electro-optic effect in semiconductors: Ab initio description of the electronic contribution

NASA Astrophysics Data System (ADS)

Prussel, Lucie; Véniard, Valérie

2018-05-01

We propose an ab initio framework to derive the electronic part of the second-order susceptibility tensor for the electro-optic effect in bulk semiconductors. We find a general expression for χ(2 ) evaluated within time-dependent density-functional theory, including explicitly the band-gap corrections at the level of the scissors approximation. Excitonic effects are accounted for, on the basis of a simple scalar approximation. We apply our formalism to the computation of the electro-optic susceptibilities for several semiconductors, such as GaAs, GaN, and SiC. Taking into account the ionic contribution according to the Faust-Henry coefficient, we obtain a good agreement with experimental results. Finally, using different types of strain to break centrosymmetry, we show that high electro-optic coefficients can be obtained in bulk silicon for a large range of frequencies.

FTA-ABS test

MedlinePlus

... rule out a possible false-negative result. Normal Results A negative or nonreactive result means that you ... meaning of your specific test results. What Abnormal Results Mean A positive FTA-ABS is often a ...

[Comparison of the effect of different diagnostic criteria of subclinical hypothyroidism and positive TPO-Ab on pregnancy outcomes].

PubMed

He, Yiping; He, Tongqiang; Wang, Yanxia; Xu, Zhao; Xu, Yehong; Wu, Yiqing; Ji, Jing; Mi, Yang

2014-11-01

To explore the effect of different diagnositic criteria of subclinical hypothyroidism using thyroid stimulating hormone (TSH) and positive thyroid peroxidase antibodies (TPO-Ab) on the pregnancy outcomes. 3 244 pregnant women who had their antenatal care and delivered in Child and Maternity Health Hospital of Shannxi Province August from 2011 to February 2013 were recruited prospectively. According to the standard of American Thyroid Association (ATA), pregnant women with normal serum free thyroxine (FT4) whose serum TSH level> 2.50 mU/L were diagnosed as subclinical hypothyroidism in pregnancy (foreign standard group). According to the Guideline of Diagnosis and Therapy of Prenatal and Postpartum Thyroid Disease made by Chinese Society of Endocrinology and Chinese Society of Perinatal Medicine in 2012, pregnant women with serum TSH level> 5.76 mU/L, and normal FT4 were diagnosed as subclinical hypothyroidism in pregnancy(national standard group). Pregnant women with subclinical hypothyroidism whose serum TSH levels were between 2.50-5.76 mU/L were referred as the study observed group; and pregnant women with serum TSH level< 2.50 mU/L and negative TPO- Ab were referred as the control group. Positive TPO-Ab results and the pregnancy outcomes were analyzed. (1) There were 635 cases in the foreign standard group, with the incidence of 19.57% (635/3 244). And there were 70 cases in the national standard group, with the incidence of 2.16% (70/3 244). There were statistically significant difference between the two groups (P < 0.01). There were 565 cases in the study observed group, with the incidence of 17.42% (565/3 244). There was statistically significant difference (P < 0.01) when compared with the national standard group; while there was no statistically significant difference (P > 0.05) when compared with the foreign standard group. (2) Among the 3 244 cases, 402 cases had positive TPO-Ab. 318 positive cases were in the foreign standard group, and the incidence of

Density-matrix based determination of low-energy model Hamiltonians from ab initio wavefunctions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Changlani, Hitesh J.; Zheng, Huihuo; Wagner, Lucas K.

2015-09-14

We propose a way of obtaining effective low energy Hubbard-like model Hamiltonians from ab initio quantum Monte Carlo calculations for molecular and extended systems. The Hamiltonian parameters are fit to best match the ab initio two-body density matrices and energies of the ground and excited states, and thus we refer to the method as ab initio density matrix based downfolding. For benzene (a finite system), we find good agreement with experimentally available energy gaps without using any experimental inputs. For graphene, a two dimensional solid (extended system) with periodic boundary conditions, we find the effective on-site Hubbard U{sup ∗}/t tomore » be 1.3 ± 0.2, comparable to a recent estimate based on the constrained random phase approximation. For molecules, such parameterizations enable calculation of excited states that are usually not accessible within ground state approaches. For solids, the effective Hamiltonian enables large-scale calculations using techniques designed for lattice models.« less

Effects of a diet containing genetically modified rice expressing the Cry1Ab/1Ac protein (Bacillus thuringiensis toxin) on broiler chickens.

PubMed

Li, Zeyang; Gao, Yang; Zhang, Minhong; Feng, Jinghai; Xiong, Yandan

2015-01-01

The aim of this study was to evaluate the effect of feeding Bacillus thuringiensis (Bt) rice expressing the Cry1Ab/1Ac protein on broiler chicken. The genetically modified (GM) Bt rice was compared with the corresponding non-GM rice regarding performance of feeding groups, their health status, relative organ weights, biochemical serum parameters and occurrence of Cry1Ab/1Ac gene fragments. One hundred and eighty day-old Arbor Acres female broilers with the same health condition were randomly allocated to the two treatments (6 replicate cages with 15 broilers in each cage per treatment). They received diets containing GM rice (GM group) or its parental non-GM rice (non-GM group) at 52-57% of the air-dried diet for 42 days. The results show that the transgenic rice had a similar nutrient composition as the non-GM rice and had no adverse effects on chicken growth, biochemical serum parameters and necropsy during the 42-day feeding period. In birds fed the GM rice, no transgenic gene fragments were detected in the samples of blood, liver, kidneys, spleen, jejunum, ileum, duodenum and muscle tissue. In conclusion, the results suggest that Bt rice expressing Cry1Ab/1Ac protein has no adverse effects on broiler chicken. Therefore, it can be considered as safe and used as feed source for broiler chicken.

Undoing Gender through Legislation and Schooling: The Case of AB 537 and AB 394 in California, USA

ERIC Educational Resources Information Center

Knotts, Greg

2009-01-01

This article investigates California laws AB 537: The Student Safety and Violence Prevention Act of 2000, and the recently enacted AB 394: Safe Place to Learn Act. Both demand that gender identity and sexual orientation be added to the lexicon of anti-harassment protection in public education. However, despite these progressive measures, schools…

Evolving trends in mAb production processes

PubMed Central

Wolfe, Leslie S.; Mostafa, Sigma S.; Norman, Carnley

2017-01-01

Abstract Monoclonal antibodies (mAbs) have established themselves as the leading biopharmaceutical therapeutic modality. The establishment of robust manufacturing platforms are key for antibody drug discovery efforts to seamlessly translate into clinical and commercial successes. Several drivers are influencing the design of mAb manufacturing processes. The advent of biosimilars is driving a desire to achieve lower cost of goods and globalize biologics manufacturing. High titers are now routinely achieved for mAbs in mammalian cell culture. These drivers have resulted in significant evolution in process platform approaches. Additionally, several new trends in bioprocessing have arisen in keeping with these needs. These include the consideration of alternative expression systems, continuous biomanufacturing and non‐chromatographic separation formats. This paper discusses these drivers in the context of the kinds of changes they are driving in mAb production processes. PMID:29313024

Heats of Segregation of BCC Binaries from ab Initio and Quantum Approximate Calculations

NASA Technical Reports Server (NTRS)

Good, Brian S.

2004-01-01

We compare dilute-limit heats of segregation for selected BCC transition metal binaries computed using ab initio and quantum approximate energy methods. Ab initio calculations are carried out using the CASTEP plane-wave pseudopotential computer code, while quantum approximate results are computed using the Bozzolo-Ferrante-Smith (BFS) method with the most recent LMTO-based parameters. Quantum approximate segregation energies are computed with and without atomistic relaxation, while the ab initio calculations are performed without relaxation. Results are discussed within the context of a segregation model driven by strain and bond-breaking effects. We compare our results with full-potential quantum calculations and with available experimental results.

Ab Initio-Based Predictions of Hydrocarbon Combustion Chemistry

DTIC Science & Technology

2015-07-15

There are two prime objectives of the research. One is to develop and apply efficient methods for using ab initio potential energy surfaces (PESs...31-Mar-2015 Approved for Public Release; Distribution Unlimited Final Report: Ab Initio -Based Predictions of Hydrocarbon Combustion Chemistry The...Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 hydrocarbon combustion, ab initio quantum chemistry, potential energy surfaces, chemical

Unique synergism in flame retardancy in ABS based composites through blending PVDF and halloysite nanotubes

NASA Astrophysics Data System (ADS)

Remanan, Sanjay; Sharma, Maya; Jayashree, Priyadarshini; Parameswaranpillai, Jyotishkumar; Fabian, Thomas; Shih, Julie; Shankarappa, Prasad; Nuggehalli, Bharath; Bose, Suryasarathi

2017-06-01

This study demonstrates flame retardant materials designed using bi-phasic polymer blends of acrylonitrile butadiene styrene (ABS) and polyvinylidene fluoride (PVDF) containing halloysite nanotubes (HNTs) and Cloisite 30B nanoclay. The prepared blends with and without nanoparticles were extensively characterized. The nanoparticles were added in different weight concentrations to improve the flame retardancy. It was observed that prepared ABS/PVDF blends showed better flame retardancy than ABS based composites. The flame resistance was further improved by the addition of nanoparticles in the blends. The microscale combustion calorimetry (MCC) test showed better flame resistance in ABS/PVDF blends filled with 5 wt% HNTs than other composites. The total heat release of ABS/PVDF blend filled with 5 wt% HNTs decreased by 31% and also the heat of combustion decreased by 26% as compared to neat ABS. When compared with nanoparticles, the addition of PVDF reduced the peak heat release rate (PHRR) and increased the char residue more effectively. A synergistic improvement was observed from both PVDF and HNTs on the flame resistance properties.

Approaches to ab initio molecular replacement of α-helical transmembrane proteins.

PubMed

Thomas, Jens M H; Simkovic, Felix; Keegan, Ronan; Mayans, Olga; Zhang, Chengxin; Zhang, Yang; Rigden, Daniel J

2017-12-01

α-Helical transmembrane proteins are a ubiquitous and important class of proteins, but present difficulties for crystallographic structure solution. Here, the effectiveness of the AMPLE molecular replacement pipeline in solving α-helical transmembrane-protein structures is assessed using a small library of eight ideal helices, as well as search models derived from ab initio models generated both with and without evolutionary contact information. The ideal helices prove to be surprisingly effective at solving higher resolution structures, but ab initio-derived search models are able to solve structures that could not be solved with the ideal helices. The addition of evolutionary contact information results in a marked improvement in the modelling and makes additional solutions possible.

Characterization of virulence factor regulation by SrrAB, a two-component system in Staphylococcus aureus.

PubMed

Pragman, Alexa A; Yarwood, Jeremy M; Tripp, Timothy J; Schlievert, Patrick M

2004-04-01

Workers in our laboratory have previously identified the staphylococcal respiratory response AB (SrrAB), a Staphylococcus aureus two-component system that acts in the global regulation of virulence factors. This system down-regulates production of agr RNAIII, protein A, and toxic shock syndrome toxin 1 (TSST-1), particularly under low-oxygen conditions. In this study we investigated the localization and membrane orientation of SrrA and SrrB, transcription of the srrAB operon, the DNA-binding properties of SrrA, and the effect of SrrAB expression on S. aureus virulence. We found that SrrA is localized to the S. aureus cytoplasm, while SrrB is localized to the membrane and is properly oriented to function as a histidine kinase. srrAB has one transcriptional start site which results in either an srrA transcript or a full-length srrAB transcript; srrB must be cotranscribed with srrA. Gel shift assays of the agr P2, agr P3, protein A (spa), TSST-1 (tst), and srr promoters revealed SrrA binding at each of these promoters. Analysis of SrrAB-overexpressing strains by using the rabbit model of bacterial endocarditis demonstrated that overexpression of SrrAB decreased the virulence of the organisms compared to the virulence of isogenic strains that do not overexpress SrrAB. We concluded that SrrAB is properly localized and oriented to function as a two-component system. Overexpression of SrrAB, which represses agr RNAIII, TSST-1, and protein A in vitro, decreases virulence in the rabbit endocarditis model. Repression of these virulence factors is likely due to a direct interaction between SrrA and the agr, tst, and spa promoters.

DNA degradation in genetically modified rice with Cry1Ab by food processing methods: implications for the quantification of genetically modified organisms.

PubMed

Xing, Fuguo; Zhang, Wei; Selvaraj, Jonathan Nimal; Liu, Yang

2015-05-01

Food processing methods contribute to DNA degradation, thereby affecting genetically modified organism detection and quantification. This study evaluated the effect of food processing methods on the relative transgenic content of genetically modified rice with Cry1Ab. In steamed rice and rice noodles, the levels of Cry1Ab were ⩾ 100% and <83%, respectively. Frying and baking in rice crackers contributed to a reduction in Pubi and Cry1Ab, while microwaving caused a decrease in Pubi and an increase in Cry1Ab. The processing methods of sweet rice wine had the most severe degradation effects on Pubi and Cry1Ab. In steamed rice and rice noodles, Cry1Ab was the most stable, followed by SPS and Pubi. However, in rice crackers and sweet rice wine, SPS was the most stable, followed by Cry1Ab and Pubi. Therefore, Cry1Ab is a better representative of transgenic components than is Pubi because the levels of Cry1Ab were less affected compared to Pubi. Copyright © 2014 Elsevier Ltd. All rights reserved.

Ab Initio Studies of Shock-Induced Chemical Reactions of Inter-Metallics

NASA Astrophysics Data System (ADS)

Zaharieva, Roussislava; Hanagud, Sathya

2009-06-01

Shock-induced and shock assisted chemical reactions of intermetallic mixtures are studied by many researchers, using both experimental and theoretical techniques. The theoretical studies are primarily at continuum scales. The model frameworks include mixture theories and meso-scale models of grains of porous mixtures. The reaction models vary from equilibrium thermodynamic model to several non-equilibrium thermodynamic models. The shock-effects are primarily studied using appropriate conservation equations and numerical techniques to integrate the equations. All these models require material constants from experiments and estimates of transition states. Thus, the objective of this paper is to present studies based on ab initio techniques. The ab inito studies, to date, use ab inito molecular dynamics. This paper presents a study that uses shock pressures, and associated temperatures as starting variables. Then intermetallic mixtures are modeled as slabs. The required shock stresses are created by straining the lattice. Then, ab initio binding energy calculations are used to examine the stability of the reactions. Binding energies are obtained for different strain components super imposed on uniform compression and finite temperatures. Then, vibrational frequencies and nudge elastic band techniques are used to study reactivity and transition states. Examples include Ni and Al.

Topological Semimetals Studied by Ab Initio Calculations

NASA Astrophysics Data System (ADS)

Hirayama, Motoaki; Okugawa, Ryo; Murakami, Shuichi

2018-04-01

In topological semimetals such as Weyl, Dirac, and nodal-line semimetals, the band gap closes at points or along lines in k space which are not necessarily located at high-symmetry positions in the Brillouin zone. Therefore, it is not straightforward to find these topological semimetals by ab initio calculations because the band structure is usually calculated only along high-symmetry lines. In this paper, we review recent studies on topological semimetals by ab initio calculations. We explain theoretical frameworks which can be used for the search for topological semimetal materials, and some numerical methods used in the ab initio calculations.

Exploring the feasibility of an anti-idiotypic cocaine vaccine: analysis of the specificity of anticocaine antibodies (Ab1) capable of inducing Ab2beta anti-idiotypic antibodies.

PubMed

Schabacker, D S; Kirschbaum, K S; Segre, M

2000-05-01

Conventional vaccination with the cocaine molecule conjugated to a protein carrier is a new approach in the treatment of addiction. Experimentally, this strategy has been shown to alter the pharmacokinetics as well as the psychostimulant effect of a cocaine challenge. The purpose of this study was to investigate whether a more stable and less controversial molecule, an anti-idiotypic antibody, which mimics the configuration of the cocaine molecule (Ab2beta), could be successfully used instead of cocaine. Two cocaine conjugates that presented different areas of the cocaine molecule to the immune system were used to produce monoclonal antibodies specific for cocaine (Ab1). Several anti-idiotypic antibodies were then produced. Four were identified as Ab2beta, or internal images of the antigen; when injected into BALB/c mice, they elicited an anticocaine response. The anticocaine response elicited by one of the four Ab2beta (K1-4c) was sufficient to significantly reduce the level of cocaine that targeted the brain following cocaine challenge, compared with the level of cocaine found in the brain of control animals immunized with irrelevant antibody. In conclusion, the possibility of an anti-idiotypic vaccine seems to be worth pursuing.

Efficacy of Genetically Modified Bt Toxins Alone and in Combinations Against Pink Bollworm Resistant to Cry1Ac and Cry2Ab

PubMed Central

Tabashnik, Bruce E.; Fabrick, Jeffrey A.; Unnithan, Gopalan C.; Yelich, Alex J.; Masson, Luke; Zhang, Jie; Bravo, Alejandra; Soberón, Mario

2013-01-01

Evolution of resistance in pests threatens the long-term efficacy of insecticidal proteins from Bacillus thuringiensis (Bt) used in sprays and transgenic crops. Previous work showed that genetically modified Bt toxins Cry1AbMod and Cry1AcMod effectively countered resistance to native Bt toxins Cry1Ab and Cry1Ac in some pests, including pink bollworm (Pectinophora gossypiella). Here we report that Cry1AbMod and Cry1AcMod were also effective against a laboratory-selected strain of pink bollworm resistant to Cry2Ab as well as to Cry1Ab and Cry1Ac. Resistance ratios based on the concentration of toxin killing 50% of larvae for the resistant strain relative to a susceptible strain were 210 for Cry2Ab, 270 for Cry1Ab, and 310 for Cry1Ac, but only 1.6 for Cry1AbMod and 2.1 for Cry1AcMod. To evaluate the interactions among toxins, we tested combinations of Cry1AbMod, Cry1Ac, and Cry2Ab. For both the resistant and susceptible strains, the net results across all concentrations tested showed slight but significant synergism between Cry1AbMod and Cry2Ab, whereas the other combinations of toxins did not show consistent synergism or antagonism. The results suggest that the modified toxins might be useful for controlling populations of pink bollworm resistant to Cry1Ac, Cry2Ab, or both. PMID:24244692

Quantum Stochastic Trajectories: The Fokker-Planck-Bohm Equation Driven by the Reduced Density Matrix.

PubMed

Avanzini, Francesco; Moro, Giorgio J

2018-03-15

The quantum molecular trajectory is the deterministic trajectory, arising from the Bohm theory, that describes the instantaneous positions of the nuclei of molecules by assuring the agreement with the predictions of quantum mechanics. Therefore, it provides the suitable framework for representing the geometry and the motions of molecules without neglecting their quantum nature. However, the quantum molecular trajectory is extremely demanding from the computational point of view, and this strongly limits its applications. To overcome such a drawback, we derive a stochastic representation of the quantum molecular trajectory, through projection operator techniques, for the degrees of freedom of an open quantum system. The resulting Fokker-Planck operator is parametrically dependent upon the reduced density matrix of the open system. Because of the pilot role played by the reduced density matrix, this stochastic approach is able to represent accurately the main features of the open system motions both at equilibrium and out of equilibrium with the environment. To verify this procedure, the predictions of the stochastic and deterministic representation are compared for a model system of six interacting harmonic oscillators, where one oscillator is taken as the open quantum system of interest. The undeniable advantage of the stochastic approach is that of providing a simplified and self-contained representation of the dynamics of the open system coordinates. Furthermore, it can be employed to study the out of equilibrium dynamics and the relaxation of quantum molecular motions during photoinduced processes, like photoinduced conformational changes and proton transfers.

Phylogenetic and environmental diversity of DsrAB-type dissimilatory (bi)sulfite reductases

PubMed Central

Müller, Albert Leopold; Kjeldsen, Kasper Urup; Rattei, Thomas; Pester, Michael; Loy, Alexander

2015-01-01

The energy metabolism of essential microbial guilds in the biogeochemical sulfur cycle is based on a DsrAB-type dissimilatory (bi)sulfite reductase that either catalyzes the reduction of sulfite to sulfide during anaerobic respiration of sulfate, sulfite and organosulfonates, or acts in reverse during sulfur oxidation. Common use of dsrAB as a functional marker showed that dsrAB richness in many environments is dominated by novel sequence variants and collectively represents an extensive, largely uncharted sequence assemblage. Here, we established a comprehensive, manually curated dsrAB/DsrAB database and used it to categorize the known dsrAB diversity, reanalyze the evolutionary history of dsrAB and evaluate the coverage of published dsrAB-targeted primers. Based on a DsrAB consensus phylogeny, we introduce an operational classification system for environmental dsrAB sequences that integrates established taxonomic groups with operational taxonomic units (OTUs) at multiple phylogenetic levels, ranging from DsrAB enzyme families that reflect reductive or oxidative DsrAB types of bacterial or archaeal origin, superclusters, uncultured family-level lineages to species-level OTUs. Environmental dsrAB sequences constituted at least 13 stable family-level lineages without any cultivated representatives, suggesting that major taxa of sulfite/sulfate-reducing microorganisms have not yet been identified. Three of these uncultured lineages occur mainly in marine environments, while specific habitat preferences are not evident for members of the other 10 uncultured lineages. In summary, our publically available dsrAB/DsrAB database, the phylogenetic framework, the multilevel classification system and a set of recommended primers provide a necessary foundation for large-scale dsrAB ecology studies with next-generation sequencing methods. PMID:25343514

Photon-assisted electronic and spin transport through two T-shaped three-quantum-dot molecules embedded in an Aharonov-Bohm interferometer

NASA Astrophysics Data System (ADS)

Bai, Jiyuan; Li, Li; He, Zelong; Ye, Shujiang; Zhao, Shujun; Dang, Suihu; Sun, Weimin

2017-10-01

Not Available Project supported by the National Natural Science Foundation of China (Grant Nos. 11447132 and 11504042), the Natural Science Foundation of Heilongjiang, China (Grant No. A201405), 111 Project to Harbin Engineering University, China (Grant No. B13015), Chongqing Science and Technology Commission Project, China (Grant Nos. cstc2014jcyjA00032 and cstc2016jcyjA1158), and Scientific Research Project for Advanced Talents of Yangtze Normal University, China (Grant No. 2017KYQD09).

Twisted Fermi surface of a thin-film Weyl semimetal

NASA Astrophysics Data System (ADS)

Bovenzi, N.; Breitkreiz, M.; O'Brien, T. E.; Tworzydło, J.; Beenakker, C. W. J.

2018-02-01

The Fermi surface of a conventional two-dimensional electron gas is equivalent to a circle, up to smooth deformations that preserve the orientation of the equi-energy contour. Here we show that a Weyl semimetal confined to a thin film with an in-plane magnetization and broken spatial inversion symmetry can have a topologically distinct Fermi surface that is twisted into a figure-8—opposite orientations are coupled at a crossing which is protected up to an exponentially small gap. The twisted spectral response to a perpendicular magnetic field B is distinct from that of a deformed Fermi circle, because the two lobes of a figure-8 cyclotron orbit give opposite contributions to the Aharonov-Bohm phase. The magnetic edge channels come in two counterpropagating types, a wide channel of width β {l}m2\\propto 1/B and a narrow channel of width {l}m\\propto 1/\\sqrt{B} (with {l}m=\\sqrt{{\\hslash }/{eB}} the magnetic length and β the momentum separation of the Weyl points). Only one of the two is transmitted into a metallic contact, providing unique magnetotransport signatures.

Highly anisotropic magneto-transport and field orientation dependent oscillations in aligned carbon nanotube/epoxy composites

NASA Astrophysics Data System (ADS)

Wells, Brian; Kumar, Raj; Reynolds, C. Lewis; Peters, Kara; Bradford, Philip D.

2017-12-01

Carbon nanotubes (CNTs) have been widely investigated as additive materials for composites with potential applications in electronic devices due to their extremely large electrical conductivity and current density. Here, highly aligned CNT composite films were created using a sequential layering fabrication technique. The degree of CNT alignment leads to anisotropic resistance values which varies >400× in orthogonal directions. Similarly, the magnetoresistance (MR) of the CNT composite differs depending upon the relative direction of current and the applied magnetic field. A suppression of negative to positive MR crossover was also observed. More importantly, an overall positive magnetoresistance behavior with localized +/- oscillations was discovered at low fields which persists up to room temperature when the current (I) and in-plane magnetic field (B) were parallel to the axis of CNT (B∥I∥CNT), which is consistent with Aharonov-Bohm oscillations in our CNT/epoxy composites. When the current, applied magnetic field, and nanotube axis are aligned, the in-plane MR is positive instead of negative as observed for all other field, current, and tube orientations. Here, we provide in-depth analysis of the conduction mechanism and anisotropy in the magneto-transport properties of these aligned CNT-epoxy composites.

Effective mass and Fermi surface complexity factor from ab initio band structure calculations

NASA Astrophysics Data System (ADS)

Gibbs, Zachary M.; Ricci, Francesco; Li, Guodong; Zhu, Hong; Persson, Kristin; Ceder, Gerbrand; Hautier, Geoffroy; Jain, Anubhav; Snyder, G. Jeffrey

2017-02-01

The effective mass is a convenient descriptor of the electronic band structure used to characterize the density of states and electron transport based on a free electron model. While effective mass is an excellent first-order descriptor in real systems, the exact value can have several definitions, each of which describe a different aspect of electron transport. Here we use Boltzmann transport calculations applied to ab initio band structures to extract a density-of-states effective mass from the Seebeck Coefficient and an inertial mass from the electrical conductivity to characterize the band structure irrespective of the exact scattering mechanism. We identify a Fermi Surface Complexity Factor: Nv*K* from the ratio of these two masses, which in simple cases depends on the number of Fermi surface pockets (Nv* ) and their anisotropy K*, both of which are beneficial to high thermoelectric performance as exemplified by the high values found in PbTe. The Fermi Surface Complexity factor can be used in high-throughput search of promising thermoelectric materials.

Ab Initio Studies of Stratospheric Ozone Depletion Chemistry

NASA Technical Reports Server (NTRS)

Lee, Timothy J.; Head-Gordon, Martin; Langhoff, Stephen R. (Technical Monitor)

1995-01-01

An overview of the current understanding of ozone depletion chemistry, particularly with regards the formation of the so-called Antarctic ozone hole, will be presented together with an outline as to how ab initio quantum chemistry can be used to further our understanding of stratospheric chemistry. The ability of modern state-of-the art ab initio quantum chemical techniques to characterize reliably the gas-phase molecular structure, vibrational spectrum, electronic spectrum, and thermal stability of fluorine, chlorine, bromine and nitrogen oxide species will be demonstrated by presentation of some example studies. The ab initio results will be shown to be in excellent agreement with the available experimental data, and where the experimental data are either not known or are inconclusive, the theoretical results are shown to fill in the gaps and to resolve experimental controversies. In addition, ab initio studies in which the electronic spectra and the characterization of excited electronic states of halogen oxide species will also be presented. Again where available, the ab initio results are compared to experimental observations, and are used to aid in the interpretation of experimental studies.

Clinical performance of the novel DiaSorin LIAISON(®) XL murex: HBsAg Quant, HCV-Ab, HIV-Ab/Ag assays.

PubMed

Krawczyk, Adalbert; Hintze, Christian; Ackermann, Jessica; Goitowski, Birgit; Trippler, Martin; Grüner, Nico; Neumann-Fraune, Maria; Verheyen, Jens; Fiedler, Melanie

2014-01-01

The fully automated and closed LIAISON(®)XL platform was developed for reliable detection of infection markers like hepatitis B virus (HBV) surface antigen (HBsAg), hepatitis C virus (HCV) antibodies (Ab) or human immunodeficiency virus (HIV)-Ag/Ab. To date, less is known about the diagnostic performance of this system in direct comparison to the common Abbott ARCHITECT(®) platform. We compared the diagnostic performance and usability of the DiaSorin LIAISON(®)XL with the commonly used Abbott ARCHITECT(®) system. The qualitative performance of the above mentioned assays was compared in about 500 sera. Quantitative tests were performed for HBsAg-positive samples from patients under therapy (n=289) and in vitro expressed mutants (n=37). For HCV-Ab, a total number of 155 selected samples from patients chronically infected with different HCV genotypes were tested. The concordance between both systems was 99.4% for HBsAg, 98.81% for HCV-Ab, and 99.6% for HIV-Ab/Ag. The quantitative LIAISON(®)XL murex HBsAg assay detected all mutants in comparable amounts to the HBsAg wild type and yielded highly reliable HBsAg kinetics in patients treated with antiviral drugs. Dilution experiments using the 2nd International Standard for HBsAg (WHO) showed a high accuracy of this test. HCV-Ab from patients infected with genotypes 1-3 were equally detected in both systems. Interestingly, S/CO levels of HCV-Ab from patients infected with genotype 3 seem to be relatively low using both systems. The LIAISON(®)XL platform proved to be an excellent system for diagnostics of HBV, HCV, and HIV with equal performance compared to the ARCHITECT(®) system. Copyright © 2013 Elsevier B.V. All rights reserved.

[Inhibitory effect of ¹³¹I-CD133mAb combined with cisplatin on liver cancer cells in vitro and in a tumor-bearing mouse model].

PubMed

Chen, Xingyue; Hou, Yanli; Duan, Liqun; Tang, Min; Kang, Qiangqiang; Shu, Jin; Peng, Zhiping; Li, Shaolin

2014-06-01

To study the inhibitory effect of CD133 monoclonal antibody labeled with ¹³¹I (¹³¹I-CD133mAb) on Huh-7 human liver cancer cell line overexpressing CD133 antigen in vitro and in mouse models bearing the tumor cell xenograft. ¹³¹I-CD133mAb was prepared by chloramines-T method and evaluated for its stability. Flow cytometry and immunohistochemistry were used to detect the expression of CD133 in Huh-7 cells and in Huh-7 cell-derived tumors, respectively. Huh-7 cells treated with ¹³¹I-CD133mAb plus cisplatin (DDP), ¹³¹I -CD133mAb, DDP, or no treatment (blank control) were examined for cell proliferation suppression by MTT assay with the IC₅₀ calculated. BALB/c mice bearing subcutaneous Huh-7 cell xenograft in the right forelegs were treated with ¹³¹I -CD133mAb, DDP, or both every two days for two weeks. The tumor size and volume were measured twice a week, and pathological examination of the tumor was carried out after the treatments. The tumor inhibition rate was calculated and tumor cell apoptosis observed with HE staining. The labeling ratio of ¹³¹I-CD133mAb was 90.25% and the radiochemical purity was 97.78%. Huh-7 cells showed obviously higher CD133 expression than HepG2 cells. ¹³¹I-CD133mAb combined with DDP group resulted in a significantly higher tumor inhibition rate than other treatments in the tumor-bearing mice. ¹³¹I-CD133mAb can inhibit the growth of liver cancer cells with a high CD133 expression both in vivo and in vitro.

A cell-based fluorescent assay to detect the activity of AB toxins that inhibit protein synthesis

USDA-ARS?s Scientific Manuscript database

AB-type protein toxins, produced by numerous bacterial pathogens and some plants, elicit a cytotoxic effect involving the inhibition of protein synthesis. To develop an improved method to detect the inhibition of protein synthesis by AB-type toxins, the present study characterized a Vero cell line t...

Ab initio structures and polarizabilities of sodium clusters

NASA Astrophysics Data System (ADS)

Kronik, Leeor; Vasiliev, Igor; Jain, Manish; Chelikowsky, James R.

2001-09-01

We present quantitative ab initio calculations for Na cluster structures and polarizabilities, for all cluster sizes up to 20 atoms. Our calculations are performed by combining an ab initio core-corrected pseudopotential and a gradient-corrected density functional within a real space approach. We find the cluster bonding to be very floppy and catalog a host of low-energy quasi-degenerate isomers for all second-decade clusters. The existence of these isomers results in a band of polarizability values for each cluster size even at zero temperature. This eliminates any finer structure in the polarizability curve. We further show that the experimental polarizability values are consistently underestimated by calculations at zero temperature. By computing the effects of structure expansion and distortion due to a finite temperature we arrive at a quantitative agreement between theory and experiment.

Anti-ErbB-2 mAb therapy requires type I and II interferons and synergizes with anti-PD-1 or anti-CD137 mAb therapy.

PubMed

Stagg, John; Loi, Sherene; Divisekera, Upulie; Ngiow, Shin Foong; Duret, Helene; Yagita, Hideo; Teng, Michele W; Smyth, Mark J

2011-04-26

Trastuzumab, a monoclonal antibody targeting human epidermal growth factor receptor-2 (HER2/ErbB-2), has become the mainstay of treatment for HER2-positive breast cancer. Nevertheless, its exact mechanism of action has not been fully elucidated. Although several studies suggest that Fc receptor-expressing immune cells are involved in trastuzumab therapy, the relative contribution of lymphocyte-mediated cellular cytotoxicity and antitumor cytokines remains unknown. We report here that anti-ErbB-2 mAb therapy is dependent on the release of type I and type II IFNs but is independent of perforin or FasL. Our study thus challenges the notion that classical antibody-dependent, lymphocyte-mediated cellular cytotoxicity is important for trastuzumab. We demonstrate that anti-ErbB-2 mAb therapy of experimental tumors derived from MMTV-ErbB-2 transgenic mice triggers MyD88-dependent signaling and primes IFN-γ-producing CD8+ T cells. Adoptive cell transfer of purified T cell subsets confirmed the essential role of IFN-γ-producing CD8+ T cells. Notably, anti-ErbB-2 mAb therapy was independent of IL-1R or IL-17Ra signaling. Finally, we investigated whether immunostimulatory approaches with antibodies against programmed death-1 (PD-1) or 41BB (CD137) could be used to capitalize on the immune-mediated effects of trastuzumab. We demonstrate that anti-PD-1 or anti-CD137 mAb can significantly improve the therapeutic activity of anti-ErbB-2 mAb in immunocompetent mice.

Lanthanide complex coordination polyhedron geometry prediction accuracies of ab initio effective core potential calculations.

PubMed

Freire, Ricardo O; Rocha, Gerd B; Simas, Alfredo M

2006-03-01

lanthanide coordination compounds efficiently and accurately is central for the design of new ligands capable of forming stable and highly luminescent complexes. Accordingly, we present in this paper a report on the capability of various ab initio effective core potential calculations in reproducing the coordination polyhedron geometries of lanthanide complexes. Starting with all combinations of HF, B3LYP and MP2(Full) with STO-3G, 3-21G, 6-31G, 6-31G* and 6-31+G basis sets for [Eu(H2O)9]3+ and closing with more manageable calculations for the larger complexes, we computed the fully predicted ab initio geometries for a total of 80 calculations on 52 complexes of Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III) and Tm(III), the largest containing 164 atoms. Our results indicate that RHF/STO-3G/ECP appears to be the most efficient model chemistry in terms of coordination polyhedron crystallographic geometry predictions from isolated lanthanide complex ion calculations. Moreover, both augmenting the basis set and/or including electron correlation generally enlarged the deviations and aggravated the quality of the predicted coordination polyhedron crystallographic geometry. Our results further indicate that Cosentino et al.'s suggestion of using RHF/3-21G/ECP geometries appears to be indeed a more robust, but not necessarily, more accurate recommendation to be adopted for the general lanthanide complex case. [Figure: see text].

Adsorption of transgenic insecticidal Cry1Ab protein to SiO2. 2. Patch-controlled electrostatic attraction.

PubMed

Madliger, Michael; Sander, Michael; Schwarzenbach, René P

2010-12-01

Adsorption governs the fate of Cry proteins from genetically modified Bt crops in soils. The effect of ionic strength (I) on the adsorption of Cry1Ab (isoelectric point IEP(Cry1Ab) ≈ 6) to negatively charged quartz (SiO(2)) and positively charged poly-L-lysine (PLL) was investigated at pH 5 to 8, using quartz crystal microbalance with dissipation monitoring and optical waveguide lightmode spectroscopy. Cry1Ab adsorbed via positively and negatively charged surface patches to SiO(2) and PLL, respectively. This patch controlled electrostatic attraction (PCEA) explains the observed increase in Cry1Ab adsorption to sorbents that carried the same net charge as the protein (SiO(2) at pH > IEP(Cry1Ab) and PLL at pH < IEP(Cry1Ab)) with decreasing I. In contrast, the adsorption of two reference proteins, BSA and HEWL, with different adsorption mechanism, were little affected by similar changes of I. Consistent with PCEA, Cry1Ab desorption from SiO(2) at pH > IEP(Cry1Ab) increased with increasing I and pH. Weak Cry1Ab-SiO(2) PCEA above pH 7 resulted in reversible, concentration dependent adsorption. Solution depletion experiments showed that PCEA also governed Cry1Ab adsorption to SiO(2) particles at environmentally relevant concentrations (a few ng mL(-1)). These results imply that models describing Cry1Ab adsorption to charged surfaces in soils need to account for the nonuniform surface charge distribution of the protein.

The end of a myth – Bt(Cry1Ab) maize does not harm green lacewings

USDA-ARS?s Scientific Manuscript database

A concern with Bt-transgenic insect-resistant plants is their potential to harm non-target organisms. Early studies reported that Cry1Ab-producing Bt maize and purified Cry1Ab harmed larvae of the green lacewing, Chrysoperla carnea. Although these effects could not be confirmed in subsequent studies...

Ab initio calculations for industrial materials engineering: successes and challenges.

PubMed

Wimmer, Erich; Najafabadi, Reza; Young, George A; Ballard, Jake D; Angeliu, Thomas M; Vollmer, James; Chambers, James J; Niimi, Hiroaki; Shaw, Judy B; Freeman, Clive; Christensen, Mikael; Wolf, Walter; Saxe, Paul

2010-09-29

Computational materials science based on ab initio calculations has become an important partner to experiment. This is demonstrated here for the effect of impurities and alloying elements on the strength of a Zr twist grain boundary, the dissociative adsorption and diffusion of iodine on a zirconium surface, the diffusion of oxygen atoms in a Ni twist grain boundary and in bulk Ni, and the dependence of the work function of a TiN-HfO(2) junction on the replacement of N by O atoms. In all of these cases, computations provide atomic-scale understanding as well as quantitative materials property data of value to industrial research and development. There are two key challenges in applying ab initio calculations, namely a higher accuracy in the electronic energy and the efficient exploration of large parts of the configurational space. While progress in these areas is fueled by advances in computer hardware, innovative theoretical concepts combined with systematic large-scale computations will be needed to realize the full potential of ab initio calculations for industrial applications.

Pressure tracking control of vehicle ABS using piezo valve modulator

NASA Astrophysics Data System (ADS)

Jeon, Juncheol; Choi, Seung-Bok

2011-03-01

This paper presents a wheel slip control for the ABS(anti-lock brake system) of a passenger vehicle using a controllable piezo valve modulator. The ABS is designed to optimize for braking effectiveness and good steerability. As a first step, the principal design parameters of the piezo valve and pressure modulator are appropriately determined by considering the braking pressure variation during the ABS operation. The proposed piezo valve consists of a flapper, pneumatic circuit and a piezostack actuator. In order to get wide control range of the pressure, the pressure modulator is desired. The modulator consists of a dual-type cylinder filled with different substances (fluid and gas) and a piston rod moving vertical axis to transmit the force. Subsequently, a quarter car wheel slip model is formulated and integrated with the governing equation of the piezo valve modulator. A sliding mode controller to achieve the desired slip rate is then designed and implemented. Braking control performances such as brake pressure and slip rate are evaluated via computer simulations.

A highly accurate ab initio potential energy surface for methane.

PubMed

Owens, Alec; Yurchenko, Sergei N; Yachmenev, Andrey; Tennyson, Jonathan; Thiel, Walter

2016-09-14

A new nine-dimensional potential energy surface (PES) for methane has been generated using state-of-the-art ab initio theory. The PES is based on explicitly correlated coupled cluster calculations with extrapolation to the complete basis set limit and incorporates a range of higher-level additive energy corrections. These include core-valence electron correlation, higher-order coupled cluster terms beyond perturbative triples, scalar relativistic effects, and the diagonal Born-Oppenheimer correction. Sub-wavenumber accuracy is achieved for the majority of experimentally known vibrational energy levels with the four fundamentals of (12)CH4 reproduced with a root-mean-square error of 0.70 cm(-1). The computed ab initio equilibrium C-H bond length is in excellent agreement with previous values despite pure rotational energies displaying minor systematic errors as J (rotational excitation) increases. It is shown that these errors can be significantly reduced by adjusting the equilibrium geometry. The PES represents the most accurate ab initio surface to date and will serve as a good starting point for empirical refinement.

ABO Mistyping of cis-AB Blood Group by the Automated Microplate Technique.

PubMed

Chun, Sejong; Ryu, Mi Ra; Cha, Seung-Yeon; Seo, Ji-Young; Cho, Duck

2018-01-01

The cis -AB phenotype, although rare, is the relatively most frequent of ABO subgroups in Koreans. To prevent ABO mistyping of cis -AB samples, our hospital has applied a combination of the manual tile method with automated devices. Herein, we report cases of ABO mistyping detected by the combination testing system. Cases that showed discrepant results by automated devices and the manual tile method were evaluated. These samples were also tested by the standard tube method. The automated devices used in this study were a QWALYS-3 and Galileo NEO. Exons 6 and 7 of the ABO gene were sequenced. 13 cases that had the cis -AB allele showed results suggestive of the cis -AB subgroup by manual methods, but were interpreted as AB by either automated device. This happened in 87.5% of these cases by QWALYS-3 and 70.0% by Galileo NEO. Genotyping results showed that 12 cases were ABO*cis-AB01/ABO*O01 or ABO*cis-AB01/ABO*O02 , and one case was ABO*cis-AB01/ ABO*A102. Cis -AB samples were mistyped as AB by the automated microplate technique in some cases. We suggest that the manual tile method can be a simple supplemental test for the detection of the cis -AB phenotype, especially in countries with relatively high cis- AB prevalence.

Superconducting quantum circuits theory and application

NASA Astrophysics Data System (ADS)

Deng, Xiuhao

Superconducting quantum circuit models are widely used to understand superconducting devices. This thesis consists of four studies wherein the superconducting quantum circuit is used to illustrate challenges related to quantum information encoding and processing, quantum simulation, quantum signal detection and amplification. The existence of scalar Aharanov-Bohm phase has been a controversial topic for decades. Scalar AB phase, defined as time integral of electric potential, gives rises to an extra phase factor in wavefunction. We proposed a superconducting quantum Faraday cage to detect temporal interference effect as a consequence of scalar AB phase. Using the superconducting quantum circuit model, the physical system is solved and resulting AB effect is predicted. Further discussion in this chapter shows that treating the experimental apparatus quantum mechanically, spatial scalar AB effect, proposed by Aharanov-Bohm, can't be observed. Either a decoherent interference apparatus is used to observe spatial scalar AB effect, or a quantum Faraday cage is used to observe temporal scalar AB effect. The second study involves protecting a quantum system from losing coherence, which is crucial to any practical quantum computation scheme. We present a theory to encode any qubit, especially superconducting qubits, into a universal quantum degeneracy point (UQDP) where low frequency noise is suppressed significantly. Numerical simulations for superconducting charge qubit using experimental parameters show that its coherence time is prolong by two orders of magnitude using our universal degeneracy point approach. With this improvement, a set of universal quantum gates can be performed at high fidelity without losing too much quantum coherence. Starting in 2004, the use of circuit QED has enabled the manipulation of superconducting qubits with photons. We applied quantum optical approach to model coupled resonators and obtained a four-wave mixing toolbox to operate photons

A targeted complement-dependent strategy to improve the outcome of mAb therapy, and characterization in a murine model of metastatic cancer

PubMed Central

Elvington, Michelle; Huang, Yuxiang; Morgan, B. Paul; Qiao, Fei; van Rooijen, Nico; Atkinson, Carl

2012-01-01

Complement inhibitors expressed on tumor cells provide an evasion mechanism against mAb therapy and may modulate the development of an acquired antitumor immune response. Here we investigate a strategy to amplify mAb-targeted complement activation on a tumor cell, independent of a requirement to target and block complement inhibitor expression or function, which is difficult to achieve in vivo. We constructed a murine fusion protein, CR2Fc, and demonstrated that the protein targets to C3 activation products deposited on a tumor cell by a specific mAb, and amplifies mAb-dependent complement activation and tumor cell lysis in vitro. In syngeneic models of metastatic lymphoma (EL4) and melanoma (B16), CR2Fc significantly enhanced the outcome of mAb therapy. Subsequent studies using the EL4 model with various genetically modified mice and macrophage-depleted mice revealed that CR2Fc enhanced the therapeutic effect of mAb therapy via both macrophage-dependent FcγR-mediated antibody-dependent cellular cytotoxicity, and by direct complement-mediated lysis. Complement activation products can also modulate adaptive immunity, but we found no evidence that either mAb or CR2Fc treatment had any effect on an antitumor humoral or cellular immune response. CR2Fc represents a potential adjuvant treatment to increase the effectiveness of mAb therapy of cancer. PMID:22442351

A-B Distinction in a Sample of Prominent Psychotherapists

ERIC Educational Resources Information Center

Geller, Jesse D.; Berzins, Juris I.

1976-01-01

A sample of prominent psychotherapists were asked to fill out the A-B therapist "type" scale and comment on their possible differential effectiveness in treating schizoid/schizophrenic versus neurotic patients. The data suggest that B therapists desire and seek more complex and exciting sensory-cognitive inputs during therapy hours than A…

Perspective: Ab initio force field methods derived from quantum mechanics

NASA Astrophysics Data System (ADS)

Xu, Peng; Guidez, Emilie B.; Bertoni, Colleen; Gordon, Mark S.

2018-03-01

It is often desirable to accurately and efficiently model the behavior of large molecular systems in the condensed phase (thousands to tens of thousands of atoms) over long time scales (from nanoseconds to milliseconds). In these cases, ab initio methods are difficult due to the increasing computational cost with the number of electrons. A more computationally attractive alternative is to perform the simulations at the atomic level using a parameterized function to model the electronic energy. Many empirical force fields have been developed for this purpose. However, the functions that are used to model interatomic and intermolecular interactions contain many fitted parameters obtained from selected model systems, and such classical force fields cannot properly simulate important electronic effects. Furthermore, while such force fields are computationally affordable, they are not reliable when applied to systems that differ significantly from those used in their parameterization. They also cannot provide the information necessary to analyze the interactions that occur in the system, making the systematic improvement of the functional forms that are used difficult. Ab initio force field methods aim to combine the merits of both types of methods. The ideal ab initio force fields are built on first principles and require no fitted parameters. Ab initio force field methods surveyed in this perspective are based on fragmentation approaches and intermolecular perturbation theory. This perspective summarizes their theoretical foundation, key components in their formulation, and discusses key aspects of these methods such as accuracy and formal computational cost. The ab initio force fields considered here were developed for different targets, and this perspective also aims to provide a balanced presentation of their strengths and shortcomings. Finally, this perspective suggests some future directions for this actively developing area.

Postural Change Effects on Infants' AB Task Performance: Visual, Postural, or Spatial?

ERIC Educational Resources Information Center

Lew, Adina R.; Hopkins, Brian; Owen, Laura H.; Green, Michael

2007-01-01

Smith and colleagues (Smith, L. B., Thelen, E., Titzer, R., & McLin, D. (1999). Knowing in the context of acting: The task dynamics of the A-not-B error. "Psychological Review, 106," 235-260) demonstrated that 10-month-olds succeed on a Piagetian AB search task if they are moved from a sitting position to a standing position between A and B…

Development of Anti-lock Braking System (ABS) for Vehicles Braking

NASA Astrophysics Data System (ADS)

Minh, Vu Trieu; Oamen, Godwin; Vassiljeva, Kristina; Teder, Leo

2016-11-01

This paper develops a real laboratory of anti-lock braking system (ABS) for vehicle and conducts real experiments to verify the ability of this ABS to prevent the vehicle wheel from being locked while braking. Two controllers of PID and fuzzy logic are tested for analysis and comparison. This ABS laboratory is designed for bachelor and master students to simulate and analyze performances of ABS with different control techniques on various roads and load conditions. This paper provides educational theories and practices on the design of control for system dynamics.

High Yield Chemical Vapor Deposition Growth of High Quality Large-Area AB Stacked Bilayer Graphene

PubMed Central

Liu, Lixin; Zhou, Hailong; Cheng, Rui; Yu, Woo Jong; Liu, Yuan; Chen, Yu; Shaw, Jonathan; Zhong, Xing; Huang, Yu; Duan, Xiangfeng

2012-01-01

Bernal stacked (AB stacked) bilayer graphene is of significant interest for functional electronic and photonic devices due to the feasibility to continuously tune its band gap with a vertical electrical field. Mechanical exfoliation can be used to produce AB stacked bilayer graphene flakes but typically with the sizes limited to a few micrometers. Chemical vapor deposition (CVD) has been recently explored for the synthesis of bilayer graphene but usually with limited coverage and a mixture of AB and randomly stacked structures. Herein we report a rational approach to produce large-area high quality AB stacked bilayer graphene. We show that the self-limiting effect of graphene growth on Cu foil can be broken by using a high H2/CH4 ratio in a low pressure CVD process to enable the continued growth of bilayer graphene. A high temperature and low pressure nucleation step is found to be critical for the formation of bilayer graphene nuclei with high AB stacking ratio. A rational design of a two-step CVD process is developed for the growth of bilayer graphene with high AB stacking ratio (up to 90 %) and high coverage (up to 99 %). The electrical transport studies demonstrated that devices made of the as-grown bilayer graphene exhibit typical characteristics of AB stacked bilayer graphene with the highest carrier mobility exceeding 4,000 cm2/V·s at room temperature, comparable to that of the exfoliated bilayer graphene. PMID:22906199

Evaluation of a fully automated treponemal test and comparison with conventional VDRL and FTA-ABS tests.

PubMed

Park, Yongjung; Park, Younhee; Joo, Shin Young; Park, Myoung Hee; Kim, Hyon-Suk

2011-11-01

We evaluated analytic performances of an automated treponemal test and compared this test with the Venereal Disease Research Laboratory test (VDRL) and fluorescent treponemal antibody absorption test (FTA-ABS). Precision performance of the Architect Syphilis TP assay (TP; Abbott Japan, Tokyo, Japan) was assessed, and 150 serum samples were assayed with the TP before and after heat inactivation to estimate the effect of heat inactivation. A total of 616 specimens were tested with the FTA-ABS and TP, and 400 were examined with the VDRL. The TP showed good precision performance with total imprecision of less than a 10% coefficient of variation. An excellent linear relationship between results before and after heat inactivation was observed (R(2) = 0.9961). The FTA-ABS and TP agreed well with a κ coefficient of 0.981. The concordance rate between the FTA-ABS and TP was the highest (99.0%), followed by the rates between FTA-ABS and VDRL (85.0%) and between TP and VDRL (83.8%). The automated TP assay may be adequate for screening for syphilis in a large volume of samples and can be an alternative to FTA-ABS.

[VDRL and FTA-ABS reactivity in cerebrospinal fluid: our experience].

PubMed

García-Rodríguez, J A; Martín-Sánchez, A M; Canut, A; García-García, L; Cacho, J

1990-01-01

The reactivity of 194 samples of CSF against VDRL and FTA-ABS was studied in patients attending the Clinical Hospital in Salamanca over a five years period. This laboratory was asked to rule out an etiology of syphilis. Twelve samples of CSF proved to be reactive (6.2%) against VDRL and/or FTA-ABS. Seven of these corresponded to six adults diagnosed as suffering from neurosyphilis and one to an infant with early congenital syphilis without neurological alterations; these had in common the presence of active syphilis and a reactive FTA-ABS in serum. In the CSF of the six cases of neurosyphilis, VDRL was reactive in two patients (33.3%) and FTA-ABS in five (83.3%). One minimally reactive VDRL and four FTA-ABS were detected in the remaining five patients, with no known previous history of syphilis, that were suffering from different neurological alterations and that had a nonreactive FTA-ABS in serum. The results obtained in this study point to inappropriate use in CSF of VDRL and FTA-ABS to exclude neurosyphilis in our hospital since only 3.6% of the CSF studied corresponded to patients diagnosed as suffering from neurosyphilis and also to the need for improving the criteria for patient selection.

Ab initio Studies of Magnetism in the Iron Chalcogenides FeTe and FeSe

NASA Astrophysics Data System (ADS)

Hirayama, Motoaki; Misawa, Takahiro; Miyake, Takashi; Imada, Masatoshi

2015-09-01

The iron chalcogenides FeTe and FeSe belong to the family of iron-based superconductors. We study the magnetism in these compounds in the normal state using the ab initio downfolding scheme developed for strongly correlated electron systems. In deriving ab initio low-energy effective models, we employ the constrained GW method to eliminate the double counting of electron correlations originating from the exchange correlations already taken into account in the density functional theory. By solving the derived ab initio effective models, we reveal that the elimination of the double counting is important in reproducing the bicollinear antiferromagnetic order in FeTe, as is observed in experiments. We also show that the elimination of the double counting induces a unique degeneracy of several magnetic orders in FeSe, which may explain the absence of the magnetic ordering. We discuss the relationship between the degeneracy and the recently found puzzling phenomena in FeSe as well as the magnetic ordering found under pressure.

Ab Initio Effective Rovibrational Hamiltonians for Non-Rigid Molecules via Curvilinear VMP2

NASA Astrophysics Data System (ADS)

Changala, Bryan; Baraban, Joshua H.

2017-06-01

Accurate predictions of spectroscopic constants for non-rigid molecules are particularly challenging for ab initio theory. For all but the smallest systems, ``brute force'' diagonalization of the full rovibrational Hamiltonian is computationally prohibitive, leaving us at the mercy of perturbative approaches. However, standard perturbative techniques, such as second order vibrational perturbation theory (VPT2), are based on the approximation that a molecule makes small amplitude vibrations about a well defined equilibrium structure. Such assumptions are physically inappropriate for non-rigid systems. In this talk, we will describe extensions to curvilinear vibrational Møller-Plesset perturbation theory (VMP2) that account for rotational and rovibrational effects in the molecular Hamiltonian. Through several examples, we will show that this approach provides predictions to nearly microwave accuracy of molecular constants including rotational and centrifugal distortion parameters, Coriolis coupling constants, and anharmonic vibrational and tunneling frequencies.

Poly(ethylene oxide)-Assisted Macromolecular Self-Assembly of Lignin in ABS Matrix for Sustainable Composite Applications

DOE PAGES

Akato, Kokouvi M.; Tran, Chau D.; Chen, Jihua; ...

2015-11-05

Here we report the compatibilization of biomass-derived lignin polymer in acrylonitrile butadiene styrene (ABS) thermoplastic matrix without loss of mechanical properties via poly(ethylene oxide) (PEO)-mediated macromolecular self-assembly. ABS was blended with lignin in different concentrations, and blends with 10 wt % PEO (relative to lignin) were prepared. The relative tensile strength improved slightly at low lignin content but diminished rapidly as the lignin content was increased. However, the inclusion of PEO as an interfacial adhesion promoter helped avoid deleterious effects. Dynamic mechanical analysis showed that PEO plasticized the hard phase and thus lowered the activation energy (E a) for itsmore » relaxation but caused stiffening of the soft phase and increased its E a. Microscopy revealed that incorporating lignin in ABS led to the statistical dispersion of discrete lignin domains (300–1000 nm) which, after PEO addition, were reduced to smaller interconnected particles (200–500 nm). The lignin-extended partially renewable ABS resins showed shear-thinning behavior and reduced viscosity compared to neat ABS. The preferred lignin-loaded compositions reinforced with 20 vol % chopped carbon fibers exhibited mechanical performances (77–80 MPa) equivalent to those of reinforced ABS materials reportedly used in 3D printing applications. In conclusion, this approach could lower the cost of ABS while reducing its carbon footprint.« less

An Absolute Index (Ab-index) to Measure a Researcher’s Useful Contributions and Productivity

PubMed Central

Biswal, Akshaya Kumar

2013-01-01

Bibliographic analysis has been a very powerful tool in evaluating the effective contributions of a researcher and determining his/her future research potential. The lack of an absolute quantification of the author’s scientific contributions by the existing measurement system hampers the decision-making process. In this paper, a new metric system, Absolute index (Ab-index), has been proposed that allows a more objective comparison of the contributions of a researcher. The Ab-index takes into account the impact of research findings while keeping in mind the physical and intellectual contributions of the author(s) in accomplishing the task. The Ab-index and h-index were calculated for 10 highly cited geneticists and molecular biologist and 10 young researchers of biological sciences and compared for their relationship to the researchers input as a primary author. This is the first report of a measuring method clarifying the contributions of the first author, corresponding author, and other co-authors and the sharing of credit in a logical ratio. A java application has been developed for the easy calculation of the Ab-index. It can be used as a yardstick for comparing the credibility of different scientists competing for the same resources while the Productivity index (Pr-index), which is the rate of change in the Ab-index per year, can be used for comparing scientists of different age groups. The Ab-index has clear advantage over other popular metric systems in comparing scientific credibility of young scientists. The sum of the Ab-indices earned by individual researchers of an institute per year can be referred to as Pr-index of the institute. PMID:24391941

Ab initio calculations of the lattice dynamics of silver halides

NASA Astrophysics Data System (ADS)

Gordienko, A. B.; Kravchenko, N. G.; Sedelnikov, A. N.

2010-12-01

Based on ab initio pseudopotential calculations, the results of investigations of the lattice dynamics of silver halides AgHal (Hal = Cl, Br, I) are presented. Equilibrium lattice parameters, phonon spectra, frequency densities and effective atomic-charge values are obtained for all types of crystals under study.

Nonlocal Position Changes of a Photon Revealed by Quantum Routers.

PubMed

Elitzur, Avshalom C; Cohen, Eliahu; Okamoto, Ryo; Takeuchi, Shigeki

2018-05-16

Since its publication, Aharonov and Vaidman's three-box paradox has undergone three major advances: i). A non-counterfactual scheme by the same authors in 2003 with strong rather than weak measurements for verifying the particle's subtle presence in two boxes. ii) A realization of the latter by Okamoto and Takeuchi in 2016. iii) A dynamic version by Aharonov et al. in 2017, with disappearance and reappearance of the particle. We now combine these advances together. Using photonic quantum routers the particle acts like a quantum "shutter." It is initially split between Boxes A, B and C, the latter located far away from the former two. The shutter particle's whereabouts can then be followed by a probe photon, split in both space and time and reflected by the shutter in its varying locations. Measuring the former is expected to reveal the following time-evolution: The shutter particle was, with certainty, in boxes A+C at t 1 , then only in C at t 2 , and finally in B+C at t 3 . Another branch of the split probe photon can show that boxes A+B were empty at t 2 . A Bell-like theorem applied to this experiment challenges any alternative interpretation that avoids disappearance-reappearance in favor of local hidden variables.

Ab initio theory and modeling of water.

PubMed

Chen, Mohan; Ko, Hsin-Yu; Remsing, Richard C; Calegari Andrade, Marcos F; Santra, Biswajit; Sun, Zhaoru; Selloni, Annabella; Car, Roberto; Klein, Michael L; Perdew, John P; Wu, Xifan

2017-10-10

Water is of the utmost importance for life and technology. However, a genuinely predictive ab initio model of water has eluded scientists. We demonstrate that a fully ab initio approach, relying on the strongly constrained and appropriately normed (SCAN) density functional, provides such a description of water. SCAN accurately describes the balance among covalent bonds, hydrogen bonds, and van der Waals interactions that dictates the structure and dynamics of liquid water. Notably, SCAN captures the density difference between water and ice I h at ambient conditions, as well as many important structural, electronic, and dynamic properties of liquid water. These successful predictions of the versatile SCAN functional open the gates to study complex processes in aqueous phase chemistry and the interactions of water with other materials in an efficient, accurate, and predictive, ab initio manner.

Characterization of the Physical Stability of a Lyophilized IgG1 mAb After Accelerated Shipping-like Stress

PubMed Central

Telikepalli, Srivalli; Kumru, Ozan S.; Kim, Jae Hyun; Joshi, Sangeeta B.; O'Berry, Kristin B.; Blake-Haskins, Angela W.; Perkins, Melissa D.; Middaugh, C. Russell; Volkin, David B.

2014-01-01

Upon exposure to shaking stress, an IgG1 mAb formulation in both liquid and lyophilized state formed subvisible particles. Since freeze-drying is expected to minimize protein physical instability under these conditions, the extent and nature of aggregate formation in the lyophilized preparation was examined using a variety of particle characterization techniques. The effect of formulation variables such as residual moisture content, reconstitution rate, and reconstitution medium were examined. Upon reconstitution of shake-stressed lyophilized mAb, differences in protein particle size and number were observed by Microflow Digital Imaging (MFI), with the reconstitution medium having the largest impact. Shake-stress had minor effects on the structure of protein within the particles as shown by SDS-PAGE and FTIR analysis. The lyophilized mAb was shake-stressed to different extents and stored for 3 months at different temperatures. Both extent of cake collapse and storage temperature affected the physical stability of the shake-stressed lyophilized mAb upon subsequent storage. These findings demonstrate that physical degradation upon shaking of a lyophilized IgG1 mAb formulation includes not only cake breakage, but also results in an increase in subvisible particles and turbidity upon reconstitution. The shaking-induced cake breakage of the lyophilized IgG1 mAb formulation also resulted in decreased physical stability upon storage. PMID:25522000

Towards ab initio Calculations with the Dynamical Vertex Approximation

NASA Astrophysics Data System (ADS)

Galler, Anna; Kaufmann, Josef; Gunacker, Patrik; Pickem, Matthias; Thunström, Patrik; Tomczak, Jan M.; Held, Karsten

2018-04-01

While key effects of the many-body problem — such as Kondo and Mott physics — can be understood in terms of on-site correlations, non-local fluctuations of charge, spin, and pairing amplitudes are at the heart of the most fascinating and unresolved phenomena in condensed matter physics. Here, we review recent progress in diagrammatic extensions to dynamical mean-field theory for ab initio materials calculations. We first recapitulate the quantum field theoretical background behind the two-particle vertex. Next we discuss latest algorithmic advances in quantum Monte Carlo simulations for calculating such two-particle quantities using worm sampling and vertex asymptotics, before giving an introduction to the ab initio dynamical vertex approximation (AbinitioDΓA). Finally, we highlight the potential of AbinitioDΓA by detailing results for the prototypical correlated metal SrVO3.

Progress in electron- and ion-interferometry

NASA Astrophysics Data System (ADS)

Hasselbach, Franz

2010-01-01

sources. In the context of holography, methods have been developed to record holograms without modulation of the biprism fringes by waves diffracted at the edges of the biprism filament. This simplifies the reconstruction of holograms and the evaluation of interferograms (taken, e.g. to extract a spectrum by Fourier analysis of the fringe system) significantly. A major section is devoted to the influence of electromagnetic and gravito-inertial potentials and fields on the quantum mechanical phase of matter waves: the Aharonov-Bohm effect, the inertial Aharonov-Bohm effect and its realization, the Sagnac effect and Sagnac experiments with atoms, superfluid helium, Bose-Einstein condensates, electrons and ions and their potential as rotation sensors are discussed. Möllenstedt and Wohland discovered in a crossed beam analyzer (Wien filter) an optical element for charged particles that shifts wave packets longitudinally that transverse a Wien filter on laterally separated paths. This new optical element rendered it possible to measure coherence lengths and the spectrum of charged particle waves by visibility- and Fourier-spectroscopy, to perform a 'Welcher Weg' experiment, to re-establish seemingly lost longitudinal coherence in an interferometer for charged particles and to realize a decoherence free quantum eraser. A precision test of decoherence according to a proposal from Anglin and Zurek and biprism interferences with helium atoms close the section on first-order coherence experiments. The topics of the last section are Hanbury Brown-Twiss correlations and an antibuching experiment of free electrons.

Ab initio study of collective excitations in a disparate mass molten salt.

PubMed

Bryk, Taras; Klevets, Ivan

2012-12-14

Ab initio molecular dynamics simulations and the approach of generalized collective modes are applied for calculations of spectra of longitudinal and transverse collective excitations in molten LiBr. Dispersion and damping of low- and high-frequency branches of collective excitations as well as wave-number dependent relaxing modes were calculated. The main mode contributions to partial, total, and concentration dynamic structure factors were estimated in a wide region of wave numbers. A role of polarization effects is discussed from comparison of mode contributions to concentration dynamic structure factors calculated for molten LiBr from ab initio and classical rigid ion simulations.

Partitioning-Defective 1a/b Depletion Impairs Glomerular and Proximal Tubule Development.

PubMed

Akchurin, Oleh; Du, Zhongfang; Ramkellawan, Nadira; Dalal, Vidhi; Han, Seung Hyeok; Pullman, James; Müsch, Anne; Susztak, Katalin; Reidy, Kimberly J

2016-12-01

The kidney is a highly polarized epithelial organ that develops from undifferentiated mesenchyme, although the mechanisms that regulate the development of renal epithelial polarity are incompletely understood. Partitioning-defective 1 (Par1) proteins have been implicated in cell polarity and epithelial morphogenesis; however, the role of these proteins in the developing kidney has not been established. Therefore, we studied the contribution of Par1a/b to renal epithelial development. We examined the renal phenotype of newborn compound mutant mice carrying only one allele of Par1a or Par1b. Loss of three out of four Par1a/b alleles resulted in severe renal hypoplasia, associated with impaired ureteric bud branching. Compared with kidneys of newborn control littermates, kidneys of newborn mutant mice exhibited dilated proximal tubules and immature glomeruli, and the renal proximal tubular epithelia lacked proper localization of adhesion complexes. Furthermore, Par1a/b mutants expressed low levels of renal Notch ligand Jag1, activated Notch2, and Notch effecter Hes1. Together, these data demonstrate that Par1a/b has a key role in glomerular and proximal tubule development, likely via modulation of Notch signaling. Copyright © 2016 by the American Society of Nephrology.

Filaments Production and Fused Deposition Modelling of ABS/Carbon Nanotubes Composites

PubMed Central

Fambri, Luca

2018-01-01

Composite acrylonitrile–butadiene–styrene (ABS)/carbon nanotubes (CNT) filaments at 1, 2, 4, 6 and 8 wt %, suitable for fused deposition modelling (FDM) were obtained by using a completely solvent-free process based on direct melt compounding and extrusion. The optimal CNT content in the filaments for FDM was found to be 6 wt %; for this composite, a detailed investigation of the thermal, mechanical and electrical properties was performed. Presence of CNT in ABS filaments and 3D-printed parts resulted in a significant enhancement of the tensile modulus and strength, accompanied by a reduction of the elongation at break. As documented by dynamic mechanical thermal analysis, the stiffening effect of CNTs in ABS is particularly pronounced at high temperatures. Besides, the presence of CNT in 3D-printed parts accounts for better creep and thermal dimensional stabilities of 3D-printed parts, accompanied by a reduction of the coefficient of thermal expansion). 3D-printed nanocomposite samples with 6 wt % of CNT exhibited a good electrical conductivity, even if lower than pristine composite filaments. PMID:29346291

Filaments Production and Fused Deposition Modelling of ABS/Carbon Nanotubes Composites.

PubMed

Dul, Sithiprumnea; Fambri, Luca; Pegoretti, Alessandro

2018-01-18

Composite acrylonitrile-butadiene-styrene (ABS)/carbon nanotubes (CNT) filaments at 1, 2, 4, 6 and 8 wt %, suitable for fused deposition modelling (FDM) were obtained by using a completely solvent-free process based on direct melt compounding and extrusion. The optimal CNT content in the filaments for FDM was found to be 6 wt %; for this composite, a detailed investigation of the thermal, mechanical and electrical properties was performed. Presence of CNT in ABS filaments and 3D-printed parts resulted in a significant enhancement of the tensile modulus and strength, accompanied by a reduction of the elongation at break. As documented by dynamic mechanical thermal analysis, the stiffening effect of CNTs in ABS is particularly pronounced at high temperatures. Besides, the presence of CNT in 3D-printed parts accounts for better creep and thermal dimensional stabilities of 3D-printed parts, accompanied by a reduction of the coefficient of thermal expansion). 3D-printed nanocomposite samples with 6 wt % of CNT exhibited a good electrical conductivity, even if lower than pristine composite filaments.

Investigations of immunogenic, allergenic and adjuvant properties of Cry1Ab protein after intragastric exposure in a food allergy model in mice.

PubMed

Andreassen, Monica; Bøhn, Thomas; Wikmark, Odd-Gunnar; Bodin, Johanna; Traavik, Terje; Løvik, Martinus; Nygaard, Unni Cecilie

2016-05-04

In genetically modified (GM) crops there is a risk that the inserted genes may introduce new allergens and/or adjuvants into the food and feed chain. The MON810 maize, expressing the insecticidal Cry1Ab toxin, is grown in many countries worldwide. In animal models, intranasal and intraperitoneal immunisations with the purified Cry1Ab proteins have induced immune responses, and feeding trials with Cry1Ab-containing feed have revealed some altered immune responses. Previous investigations have primarily measured antibody responses to the protein, while investigations of clinical food allergy symptoms, or allergy promotion (adjuvant effect) associated with the Cry1Ab protein are largely missing. We aimed to investigate immunogenic, allergenic and adjuvant properties of purified Cry1Ab toxin (trypCry1Ab, i.e., trypsin activated Cry1Ab) in a mouse model of food allergy. Female C3H/HeJ mice were immunized by intragastric gavage of 10 μg purified, trypsin activated Cry1Ab toxin (trypCry1Ab) alone or together with the food allergen lupin. Cholera toxin was added as a positive control for adjuvant effect to break oral tolerance. Clinical symptoms (anaphylaxis) as well as humoral and cellular responses were assessed. In contrast to results from previous airway investigations, we observed no indication of immunogenic properties of trypCry1Ab protein after repeated intragastric exposures to one dose, with or without CT as adjuvant. Moreover, the results indicated that trypCry1Ab given by the intragastric route was not able to promote allergic responses or anaphylactic reactions against the co-administered allergen lupin at the given dose. The study suggests no immunogenic, allergenic or adjuvant capacity of the given dose of trypCry1Ab protein after intragastric exposure of prime aged mice.

MicroRNA-23a/b and microRNA-27a/b suppress Apaf-1 protein and alleviate hypoxia-induced neuronal apoptosis.

PubMed

Chen, Q; Xu, J; Li, L; Li, H; Mao, S; Zhang, F; Zen, K; Zhang, C-Y; Zhang, Q

2014-03-20

Expression of apoptotic protease activating factor-1 (Apaf-1) gradually decreases during brain development, and this decrease is likely responsible for the decreased sensitivity of brain tissue to apoptosis. However, the mechanism by which Apaf-1 expression is decreased remains elusive. In the present study, we found that four microRNAs (miR-23a/b and miR-27a/b) of miR-23a-27a-24 and miR-23b-27b-24 clusters play key roles in modulating the expression of Apaf-1. First, we found that miR-23a/b and miR-27a/b suppressed the expression of Apaf-1 in vitro. Interestingly, the expression of the miR-23-27-24 clusters in the mouse cortex gradually increased in a manner that was inversely correlated with the pattern of Apaf-1 expression. Second, hypoxic injuries during fetal distress caused reduced expression of the miR-23b and miR-27b that was inversely correlated with an elevation of Apaf-1 expression during neuronal apoptosis. Third, we made neuronal-specific transgenic mice and found that overexpressing the miR-23b and miR-27b in mouse neurons inhibited the neuronal apoptosis induced by intrauterine hypoxia. In conclusion, our results demonstrate, in central neural system, that miR-23a/b and miR-27a/b are endogenous inhibitory factors of Apaf-1 expression and regulate the sensitivity of neurons to apoptosis. Our findings may also have implications for the potential target role of microRNAs in the treatment of neuronal apoptosis-related diseases.

Two decades of pharmacovigilance and clinical experience with highly purified rabies immunoglobulin F(ab')2 fragments.

PubMed

Reveneau, Elisa; Cottin, Pascale; Rasuli, Anvar

2017-03-01

Rabies is a worldwide zoonotic viral disease with no specific treatment once symptoms occur; manifest disease is almost always fatal. WHO recommendations for exposed individuals include immediate attention to the wound and use of rabies immunoglobulin and/or vaccine for post-exposure prophylaxis (PEP). Here, we provide an overview of the clinical experience with a highly purified preparation of F(ab') 2 fragments from equine rabies immunoglobulin (F(ab') 2 pERIG; Favirab TM ) in rabies PEP. Areas covered: Our review comprises a retrospective analysis of adverse event reports in the Sanofi Pasteur global pharmacovigilance database for F(ab') 2 pERIG, including adverse event reports from eight Sanofi Pasteur-sponsored clinical trials and post-market surveillance data collected between 1995 and 2014. The general safety profile of F(ab') 2 pERIG is discussed, as are the occurrence of rare anaphylactic reactions, and suspected intervention failure. Expert commentary: Over 20 years of clinical development and post-licensure experience has established the safety and effectiveness of F(ab') 2 pERIG (Favirab TM ) in rabies PEP.

Cell Culture Systems To Study Human Herpesvirus 6A/B Chromosomal Integration.

PubMed

Gravel, Annie; Dubuc, Isabelle; Wallaschek, Nina; Gilbert-Girard, Shella; Collin, Vanessa; Hall-Sedlak, Ruth; Jerome, Keith R; Mori, Yasuko; Carbonneau, Julie; Boivin, Guy; Kaufer, Benedikt B; Flamand, Louis

2017-07-15

Human herpesviruses 6A/B (HHV-6A/B) can integrate their viral genomes in the telomeres of human chromosomes. The viral and cellular factors contributing to HHV-6A/B integration remain largely unknown, mostly due to the lack of efficient and reproducible cell culture models to study HHV-6A/B integration. In this study, we characterized the HHV-6A/B integration efficiencies in several human cell lines using two different approaches. First, after a short-term infection (5 h), cells were processed for single-cell cloning and analyzed for chromosomally integrated HHV-6A/B (ciHHV-6A/B). Second, cells were infected with HHV-6A/B and allowed to grow in bulk for 4 weeks or longer and then analyzed for the presence of ciHHV-6. Using quantitative PCR (qPCR), droplet digital PCR, and fluorescent in situ hybridization, we could demonstrate that HHV-6A/B integrated in most human cell lines tested, including telomerase-positive (HeLa, MCF-7, HCT-116, and HEK293T) and telomerase-negative cell lines (U2OS and GM847). Our results also indicate that inhibition of DNA replication, using phosphonoacetic acid, did not affect HHV-6A/B integration. Certain clones harboring ciHHV-6A/B spontaneously express viral genes and proteins. Treatment of cells with phorbol ester or histone deacetylase inhibitors triggered the expression of many viral genes, including U39 , U90 , and U100 , without the production of infectious virus, suggesting that the tested stimuli were not sufficient to trigger full reactivation. In summary, both integration models yielded comparable results and should enable the identification of viral and cellular factors contributing to HHV-6A/B integration and the screening of drugs influencing viral gene expression, as well as the release of infectious HHV-6A/B from the integrated state. IMPORTANCE The analysis and understanding of HHV-6A/B genome integration into host DNA is currently limited due to the lack of reproducible and efficient viral integration systems. In the

Fluorescence dye-based detection of mAb aggregates in CHO culture supernatants.

PubMed

Paul, Albert Jesuran; Schwab, Karen; Prokoph, Nina; Haas, Elena; Handrick, René; Hesse, Friedemann

2015-06-01

Product yields, efficacy, and safety of monoclonal antibodies (mAbs) are reduced by the formation of higher molecular weight aggregates during upstream processing. In-process characterization of mAb aggregate formation is a challenge since there is a lack of a fast detection method to identify mAb aggregates in cell culture. In this work, we present a rapid method to characterize mAb aggregate-containing Chinese hamster ovary (CHO) cell culture supernatants. The fluorescence dyes thioflavin T (ThT) and 4-4-bis-1-phenylamino-8-naphthalene sulfonate (Bis-ANS) enabled the detection of soluble as well as large mAb aggregates. Partial least square (PLS) regression models were used to evaluate the linearity of the dye-based mAb aggregate detection in buffer down to a mAb aggregate concentration of 2.4 μg mL(-1). Furthermore, mAb aggregates were detected in bioprocess medium using Bis-ANS and ThT. Dye binding to aggregates was stable for 60 min, making the method robust and reliable. Finally, the developed method using 10 μmol L(-1) Bis-ANS enabled discrimination between CHO cell culture supernatants containing different levels of mAb aggregates. The method can be adapted for high-throughput screening, e.g., to screen for cell culture conditions influencing mAb product quality, and hence can contribute to the improvement of production processes of biopharmaceuticals in mammalian cell culture.

Heats of Segregation of BCC Binaries from Ab Initio and Quantum Approximate Calculations

NASA Technical Reports Server (NTRS)

Good, Brian S.

2003-01-01

We compare dilute-limit segregation energies for selected BCC transition metal binaries computed using ab initio and quantum approximate energy methods. Ab initio calculations are carried out using the CASTEP plane-wave pseudopotential computer code, while quantum approximate results are computed using the Bozzolo-Ferrante-Smith (BFS) method with the most recent parameters. Quantum approximate segregation energies are computed with and without atomistic relaxation. Results are discussed within the context of segregation models driven by strain and bond-breaking effects. We compare our results with full-potential quantum calculations and with available experimental results.

Ab initio theory and modeling of water

PubMed Central

Chen, Mohan; Ko, Hsin-Yu; Remsing, Richard C.; Calegari Andrade, Marcos F.; Santra, Biswajit; Sun, Zhaoru; Selloni, Annabella; Car, Roberto; Klein, Michael L.; Perdew, John P.; Wu, Xifan

2017-01-01

Water is of the utmost importance for life and technology. However, a genuinely predictive ab initio model of water has eluded scientists. We demonstrate that a fully ab initio approach, relying on the strongly constrained and appropriately normed (SCAN) density functional, provides such a description of water. SCAN accurately describes the balance among covalent bonds, hydrogen bonds, and van der Waals interactions that dictates the structure and dynamics of liquid water. Notably, SCAN captures the density difference between water and ice Ih at ambient conditions, as well as many important structural, electronic, and dynamic properties of liquid water. These successful predictions of the versatile SCAN functional open the gates to study complex processes in aqueous phase chemistry and the interactions of water with other materials in an efficient, accurate, and predictive, ab initio manner. PMID:28973868

Phage-Mediated Competitive Chemiluminescent Immunoassay for Detecting Cry1Ab Toxin by Using an Anti-Idiotypic Camel Nanobody.

PubMed

Qiu, Yulou; Li, Pan; Dong, Sa; Zhang, Xiaoshuai; Yang, Qianru; Wang, Yulong; Ge, Jing; Hammock, Bruce D; Zhang, Cunzheng; Liu, Xianjin

2018-01-31

Cry toxins have been widely used in genetically modified organisms for pest control, raising public concern regarding their effects on the natural environment and food safety. In this work, a phage-mediated competitive chemiluminescent immunoassay (c-CLIA) was developed for determination of Cry1Ab toxin using anti-idiotypic camel nanobodies. By extracting RNA from camels' peripheral blood lymphocytes, a naive phage-displayed nanobody library was established. Using anti-Cry1Ab toxin monoclonal antibodies (mAbs) against the library for anti-idiotypic antibody screening, four anti-idiotypic nanobodies were selected and confirmed to be specific for anti-Cry1Ab mAb binding. Thereafter, a c-CLIA was developed for detection of Cry1Ab toxin based on anti-idiotypic camel nanobodies and employed for sample testing. The results revealed a half-inhibition concentration of developed assay to be 42.68 ± 2.54 ng/mL, in the linear range of 10.49-307.1 ng/mL. The established method is highly specific for Cry1Ab recognition, with negligible cross-reactivity for other Cry toxins. For spiked cereal samples, the recoveries of Cry1Ab toxin ranged from 77.4% to 127%, with coefficient of variation of less than 9%. This study demonstrated that the competitive format based on phage-displayed anti-idiotypic nanobodies can provide an alternative strategy for Cry toxin detection.

Bitrophic and Tritrophic Effects of Transgenic cry1Ab/cry2Aj Maize on the Beneficial, Nontarget Harmonia axyridis (Coleoptera: Coccinellidae).

PubMed

Chang, Xue; Lu, Zengbin; Shen, Zhicheng; Peng, Yufa; Ye, Gongyin

2017-10-01

Harmonia axyridis (Pallas) is a common and abundant predator in China and may be exposed to Cry toxins that are produced in Bt crops either by feeding on plant parts or by feeding on target or nontarget herbivorous insects. A new Bt maize line, expressing the Cry1Ab/Cry2Aj fused protein, has been developed and should be rigorously assessed for the ecological risks on the natural enemy. Laboratory experiments were carried out to study the effects of this Bt maize on nontarget predator H. axyridis via bitrophic interaction of adult H. axyridis feeding on Bt maize pollen and tritrophic interaction of H. axyridis consuming the lepidopteran prey. Spodoptera exigua (Hübner) neonate larvae were used to transfer Bt protein because they could survive after ingesting transgenic cry1Ab/cry2Aj maize kernels in the previous study. ELISA bioassays confirmed that the Bt protein could be transferred, but diluted through Bt maize-prey-predator. Life history parameters such as survival, development, weight, fecundity, and egg hatching rate were not significantly different when H. axyridis consumed prey that had been reared on Bt maize compared with prey reared on a nontransformed parental control. Furthermore, feeding directly on Bt maize pollen also had no detrimental effects on fitness, survival, and weight of female and male adults. In conclusion, our results indicate that transgenic cry1Ab/cry2Aj maize poses no ecological risks on the nontarget predator H. axyridis. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Ab initio description of continuum effects in A=11 exotic systems with chiral NN+3N forces

NASA Astrophysics Data System (ADS)

Calci, Angelo; Navratil, Petr; Roth, Robert; Dohet-Eraly, Jeremy; Quaglioni, Sofia; Hupin, Guillaume

2016-09-01

Based on the fundamental symmetries of QCD, chiral effective field theory (EFT) provides two- (NN), three- (3N) and many-nucleon interactions in a consistent and systematically improvable scheme. The rapid developments to construct divers families of chiral NN+3N interactions and the conceptual and technical improvements of ab initio many-body approaches pose a great opportunity for nuclear physics. By studying particular interesting phenomena in nuclear structure and reaction observables one can discriminate between different forces and study the predictive power of chiral EFT. The accurate description of the 11Be nucleus, in particular, the ground-state parity inversion and exceptionally strong E1 transition between its two bound states constitute an enormous challenge for the developments of nuclear forces and many-body approaches. We present a sensitivity analysis of structure and reaction observables to different NN+3N interactions in 11Be and n+10Be as well as the mirror p+10C scattering using the ab initio NCSM with continuum (NCSMC). Supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Work Proposal No. SCW1158. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada.

Lorentz-like force emerging from kinematic interactions between electrons and nuclei in molecules: A quantum mechanical origin of symmetry breaking that can trigger molecular chirality.

PubMed

Takatsuka, Kazuo

2017-02-28

The Longuet-Higgins (Berry) phase arising from nonadiabatic dynamics and the Aharonov-Bohm phase associated with the dynamics of a charged particle in the electromagnetic vector potential are well known to be individually a manifestation of a class of the so-called geometrical phase. We herein discuss another similarity between the force working on a charged particle moving in a magnetic field, the Lorentz force, and a force working on nuclei while passing across a region where they have a strong quantum mechanical kinematic (nonadiabatic) coupling with electrons in a molecule. This kinematic force is indeed akin to the Lorentz force in that its magnitude is proportional to the velocity of the relevant nuclei and works in the direction perpendicular to its translational motion. Therefore this Lorentz-like nonadiabatic force is realized only in space of more or equal to three dimensions, thereby highlighting a truly multi-dimensional effect of nonadiabatic interaction. We investigate its physical significance qualitatively in the context of breaking of molecular spatial symmetry, which is not seen otherwise without this force. This particular symmetry breaking is demonstrated in application to a coplanar collision between a planar molecule and an atom sharing the same plane. We show that the atom is guided by this force to the direction out from the plane, resulting in a configuration that distinguishes one side of the mirror plane from the other. This can serve as a trigger for the dynamics towards molecular chirality.

Bicanonical ab Initio Molecular Dynamics for Open Systems.

PubMed

Frenzel, Johannes; Meyer, Bernd; Marx, Dominik

2017-08-08

Performing ab initio molecular dynamics simulations of open systems, where the chemical potential rather than the number of both nuclei and electrons is fixed, still is a challenge. Here, drawing on bicanonical sampling ideas introduced two decades ago by Swope and Andersen [ J. Chem. Phys. 1995 , 102 , 2851 - 2863 ] to calculate chemical potentials of liquids and solids, an ab initio simulation technique is devised, which introduces a fictitious dynamics of two superimposed but otherwise independent periodic systems including full electronic structure, such that either the chemical potential or the average fractional particle number of a specific chemical species can be kept constant. As proof of concept, we demonstrate that solvation free energies can be computed from these bicanonical ab initio simulations upon directly superimposing pure bulk water and the respective aqueous solution being the two limiting systems. The method is useful in many circumstances, for instance for studying heterogeneous catalytic processes taking place on surfaces where the chemical potential of reactants rather than their number is controlled and opens a pathway toward ab initio simulations at constant electrochemical potential.

HO + CO reaction rates and H/D kinetic isotope effects: master equation models with ab initio SCTST rate constants.

PubMed

Weston, Ralph E; Nguyen, Thanh Lam; Stanton, John F; Barker, John R

2013-02-07

Ab initio microcanonical rate constants were computed using Semi-Classical Transition State Theory (SCTST) and used in two master equation formulations (1D, depending on active energy with centrifugal corrections, and 2D, depending on total energy and angular momentum) to compute temperature-dependent rate constants for the title reactions using a potential energy surface obtained by sophisticated ab initio calculations. The 2D master equation was used at the P = 0 and P = ∞ limits, while the 1D master equation with centrifugal corrections and an empirical energy transfer parameter could be used over the entire pressure range. Rate constants were computed for 75 K ≤ T ≤ 2500 K and 0 ≤ [He] ≤ 10(23) cm(-3). For all temperatures and pressures important for combustion and for the terrestrial atmosphere, the agreement with the experimental rate constants is very good, but at very high pressures and T ≤ 200 K, the theoretical rate constants are significantly smaller than the experimental values. This effect is possibly due to the presence in the experiments of dimers and prereactive complexes, which were not included in the model calculations. The computed H/D kinetic isotope effects are in acceptable agreement with experimental data, which show considerable scatter. Overall, the agreement between experimental and theoretical H/D kinetic isotope effects is much better than in previous work, and an assumption of non-RRKM behavior does not appear to be needed to reproduce experimental observations.

Biodistribution of charged F(ab')2 photoimmunoconjugates in a xenograft model of ovarian cancer.

PubMed

Duska, L R; Hamblin, M R; Bamberg, M P; Hasan, T

1997-01-01

The effect of charge modification of photoimmunoconjugates (PICs) on their biodistribution in a xenograft model of ovarian cancer was investigated. Chlorin(e6)c(e6) was attached site specifically to the F(ab')2 fragment of the murine monoclonal antibody OC125, directed against human ovarian cancer cells, via poly-1-lysine linkers carrying cationic or anionic charges. Preservation of immunoreactivity was checked by enzyme-linked immunosorbent assay (ELISA). PICs were radiolabelled with 125I and compared with non-specific rabbit IgG PICs after intraperitoneal (i.p.) injection into nude mice. Samples were taken from normal organs and tumour at 3 h and 24 h. Tumour to normal 125I ratios showed that the cationic OC125F(ab')2 PIC had the highest tumour selectivity. Ratios for c(e6) were uniformly higher than for 125I, indicating that c(e6) became separated from 125I. OC125F(ab')2 gave highest tissue values of 125I, followed by cationic OC125F(ab')2 PIC; other species were much lower. The amounts of c(e6) delivered per gram of tumour were much higher for cationic OC125F(ab')2 PIC than for other species. The results indicate that cationic charge stimulates the endocytosis and lysosomal degradation of the OC125F(ab')2-pl-c(e6) that has bound to the i.p. tumour. Positively charged PICs may have applications in the i.p. photoimmunotherapy of minimal residual ovarian cancer.

Biodistribution of charged F(ab')2 photoimmunoconjugates in a xenograft model of ovarian cancer.

PubMed Central

Duska, L. R.; Hamblin, M. R.; Bamberg, M. P.; Hasan, T.

1997-01-01

The effect of charge modification of photoimmunoconjugates (PICs) on their biodistribution in a xenograft model of ovarian cancer was investigated. Chlorin(e6)c(e6) was attached site specifically to the F(ab')2 fragment of the murine monoclonal antibody OC125, directed against human ovarian cancer cells, via poly-1-lysine linkers carrying cationic or anionic charges. Preservation of immunoreactivity was checked by enzyme-linked immunosorbent assay (ELISA). PICs were radiolabelled with 125I and compared with non-specific rabbit IgG PICs after intraperitoneal (i.p.) injection into nude mice. Samples were taken from normal organs and tumour at 3 h and 24 h. Tumour to normal 125I ratios showed that the cationic OC125F(ab')2 PIC had the highest tumour selectivity. Ratios for c(e6) were uniformly higher than for 125I, indicating that c(e6) became separated from 125I. OC125F(ab')2 gave highest tissue values of 125I, followed by cationic OC125F(ab')2 PIC; other species were much lower. The amounts of c(e6) delivered per gram of tumour were much higher for cationic OC125F(ab')2 PIC than for other species. The results indicate that cationic charge stimulates the endocytosis and lysosomal degradation of the OC125F(ab')2-pl-c(e6) that has bound to the i.p. tumour. Positively charged PICs may have applications in the i.p. photoimmunotherapy of minimal residual ovarian cancer. PMID:9062404

Optimization of Antibiotic Use in Hospitals – Antimicrobial Stewardship and the EU Project ABS International

PubMed Central

Allerberger, Franz; Lechner, Arno; Wechsler-Fördös, Agnes; Gareis, Roland

2008-01-01

Background The problem of antimicrobial resistance requires common strategies at the European level. Methods We report on an EU initiative fostering antibiotic (AB) stewardship (ABS) in hospitals. Results The project ‘ABS International: implementing antibiotic strategies for appropriate use of antibiotics in hospitals in member states of the EU’ started in September 2006 in Austria, Belgium, the Czech Republic, Germany, Hungary, Italy, Poland, Slovenia and Slovakia. A training program for national ABS trainers was prepared and standard templates for ABS tools (AB list, guidelines for AB treatment and surgical prophylaxis, and AB-related organization) and valid process measures as well as quality indicators for AB use were developed. Specific ABS tools are being implemented in up to five health care facilities per country. Conclusion ABS International is the first EU-funded initiative focusing on the implementation of structural measures in hospitals to promote the prudent use of ABs. PMID:18667815

The individual and cumulative effect of brominated flame retardant and polyvinylchloride (PVC) on thermal degradation of acrylonitrile-butadiene-styrene (ABS) copolymer.

PubMed

Brebu, Mihai; Bhaskar, Thallada; Murai, Kazuya; Muto, Akinori; Sakata, Yusaku; Uddin, Md Azhar

2004-08-01

Acrylonitrile-butadiene-styrene (ABS) copolymers without and with a polybrominated epoxy type flame retardant were thermally degraded at 450 degrees C alone (10 g) and mixed with polyvinylchloride (PVC) (8 g/2 g). Gaseous and liquid products of degradation were analysed by various gas chromatographic methods (GC with TCD, FID, AED, MSD) in order to determine the individual and cumulative effect of bromine and chlorine on the quality and quantity of degradation compounds. It was found that nitrogen, chlorine, bromine and oxygen are present as organic compounds in liquid products, their quantity depends on the pyrolysed polymer or polymer mixture. Bromophenol and dibromophenols were the main brominated compounds that come from the flame retardant. 1-Chloroethylbenzene was the main chlorine compound observed in liquid products. It was also determined that interactions appear at high temperatures during decomposition between the flame retardant, PVC and the ABS copolymer.

Nonlinear effects in evolution - an ab initio study: A model in which the classical theory of evolution occurs as a special case.

PubMed

Clerc, Daryl G

2016-07-21

An ab initio approach was used to study the molecular-level interactions that connect gene-mutation to changes in an organism׳s phenotype. The study provides new insights into the evolutionary process and presents a simplification whereby changes in phenotypic properties may be studied in terms of the binding affinities of the chemical interactions affected by mutation, rather than by correlation to the genes. The study also reports the role that nonlinear effects play in the progression of organs, and how those effects relate to the classical theory of evolution. Results indicate that the classical theory of evolution occurs as a special case within the ab initio model - a case having two attributes. The first attribute: proteins and promoter regions are not shared among organs. The second attribute: continuous limiting behavior exists in the physical properties of organs as well as in the binding affinity of the associated chemical interactions, with respect to displacements in the chemical properties of proteins and promoter regions induced by mutation. Outside of the special case, second-order coupling contributions are significant and nonlinear effects play an important role, a result corroborated by analyses of published activity levels in binding and transactivation assays. Further, gradations in the state of perfection of an organ may be small or large depending on the type of mutation, and not necessarily closely-separated as maintained by the classical theory. Results also indicate that organs progress with varying degrees of interdependence, the likelihood of successful mutation decreases with increasing complexity of the affected chemical system, and differences between the ab initio model and the classical theory increase with increasing complexity of the organism. Copyright © 2016 The Author. Published by Elsevier Ltd.. All rights reserved.

Impact-induced fracture mechanisms of immiscible PC/ABS (50/50) blends

NASA Astrophysics Data System (ADS)

Machmud, M. N.; Omiya, M.; Inoue, H.; Kishimoto, K.

2018-03-01

This paper presents a study on fracture mechanisms of polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) (50/50) blends with different ABS types under a drop weight impact test (DWIT) using a circular sheet specimen. Formation of secondary crack indicated by a stress-whitening layer on the mid-plane of scattered specimens and secondary surface of fracture perpendicular to primary fracture surface were captured under scanning electron microscope (SEM). Although the both blends finally failed in brittle modes, SEM observation showed that their secondary fracture mechanisms were completely different. Observation through the thickness of the etched PC/ABS specimen samples using SEM also clearly showed that PC and ABS were immiscible. The immiscibility between PC and ABS was indicated by presence of their layer structures through the thickness of the blends. It was revealed that layer of ABS structure was influenced by size of rubber particle and this latter parameter then affected microstructure and fracture mechanisms of the blends. Impact-induced fracture mechanisms of the blends due to such microstructures are discussed in this paper. It was also pointed out that the secondary cracking was likely caused by interface delamination between PC and ABS layers in the core due to transverse shear stress generated during the impact test.

Effects of Mg II and Ca II ionization on ab-initio solar chromosphere models

NASA Technical Reports Server (NTRS)

Rammacher, W.; Cuntz, M.

1991-01-01

Acoustically heated solar chromosphere models are computed considering radiation damping by (non-LTE) emission from H(-) and by Mg II and Ca II emission lines. The radiative transfer equations for the Mg II k and Ca II K emission lines are solved using the core-saturation method with complete redistribution. The Mg II k and Ca II K cooling rates are compared with the VAL model C. Several substantial improvements over the work of Ulmschneider et al. (1987) are included. It is found that the rapid temperature rises caused by the ionization of Mg II are not formed in the middle chromosphere, but occur at larger atmospheric heights. These models represent the temperature structure of the 'real' solar chromosphere much better. This result is a major precondition for the study of ab-initio models for solar flux tubes based on MHD wave propagation and also for ab-initio models for the solar transition layer.

Development and application of ab initio QM/MM methods for mechanistic simulation of reactions in solution and in enzymes

PubMed Central

Hu, Hao; Yang, Weitao

2013-01-01

Determining the free energies and mechanisms of chemical reactions in solution and enzymes is a major challenge. For such complex reaction processes, combined quantum mechanics/molecular mechanics (QM/MM) method is the most effective simulation method to provide an accurate and efficient theoretical description of the molecular system. The computational costs of ab initio QM methods, however, have limited the application of ab initio QM/MM methods. Recent advances in ab initio QM/MM methods allowed the accurate simulation of the free energies for reactions in solution and in enzymes and thus paved the way for broader application of the ab initio QM/MM methods. We review here the theoretical developments and applications of the ab initio QM/MM methods, focusing on the determination of reaction path and the free energies of the reaction processes in solution and enzymes. PMID:24146439

Combined clear corneal phacoemulsification and ab interno trabeculectomy: three-year case series.

PubMed

Ferrari, Ettore; Bandello, Francesco; Roman-Pognuz, Derri; Menchini, Francesca

2005-09-01

To evaluate the efficacy and safety of a novel surgical approach, ab interno trabeculectomy, in a combined procedure (clear corneal phacoemulsification + ab interno trabeculectomy) for the management of concurrent cataract and glaucoma with prognostic factors for filtration failure. Department of Ophthalmology, Palmanova Hospital, Udine, Italy. A prospective noncomparative case series of 11 eyes of 11 consecutive cataract patients with medically uncontrolled primary open-angle glaucoma or pseudoexfoliation glaucoma was performed. Each patient had phacoemulsification + intraocular lens implantation + ab interno trabeculectomy, which consisted of a gonioscopically controlled ab interno removal of a quadrant (3 clock hours) of the trabecular meshwork. The main outcome measures were intraocular pressure (IOP), the number of antiglaucomatous medications used, and complications. Ten patients completed a 3-year follow-up. One patient had further surgery because of poor IOP control; in this case, the last valid observation was carried forward for IOP calculation. Mean preoperative IOP and IOPs measured 1, 3, 6, 12, 24, and 36 months after surgery were 25.0, 15.8, 15.4, 15.4, 15.2, 15.0, and 15.3 (-38.56%) mm Hg respectively. The number of medications averaged 2.4 before surgery and dropped to 0.8 at the end of follow-up. No major complications occurred during the follow-up period. The new surgical procedure combining phacoemulsification with ab interno trabeculectomy can induce a clinically relevant decrease in IOP in eyes with cataract and glaucoma with poor prognosis for filtering surgery. However, a randomized controlled clinical trial with a more extended follow-up and a larger series of patients is needed to ascertain the actual effectiveness and safety of this procedure.

New insights into mechanistic photoisomerization of ethylene-bridged azobenzene from ab initio multiple spawning simulation.

PubMed

Liu, Lihong; Wang, Yating; Fang, Qiu

2017-02-14

Ethylene-bridged azobenzene (br-AB) has aroused broad interests due to its unique photoswitching properties. Numerous dynamical simulations have been performed for the br-AB photoisomerization, which focused mainly on the conformational effect and the funnel role of minimum-energy conical intersection (MECI) on the mechanism. In the present work, we use the "full quantum" ab initio multiple spawning method to simulate the br-AB photoisomerization, which provides new insights into the mechanism. Upon irradiation of br-AB to the first excited singlet state (S 1 ), most of the excess energies are trapped in the azo-moiety. Since the intramolecular vibrational energy redistribution is slower than the S 1 relaxation processes, the nonadiabatic transition from S 1 to the ground state (S 0 ) occurs in the vicinity of high-energy crossing seam and even the largest probabilities of the S 1 → S 0 transition are not distributed in the MECI regions. Once decaying to the S 0 state through the high-energy region, the subsequent isomerization and re-formation of the initial isomer are ultrafast processes in the S 0 state. It is the nonergodic behavior of the S 1 and S 0 dynamics that is mainly responsible for the unique photoswitching properties of the ethylene-bridged azobenzene, which will be discussed in detail.

A Kine-chemical Investigation of the AB Dor Moving Group "Stream"

NASA Astrophysics Data System (ADS)

Barenfeld, Scott A.; Bubar, Eric J.; Mamajek, Eric E.; Young, Patrick A.

2013-03-01

The AB Dor Moving Group consists of a "nucleus" of ~10 stars at d ~= 20 pc, along with dozens of purported "stream" members distributed across the sky. We perform a chemical and kinematic analysis of a subsample of AB Dor stream stars to test whether they constitute a physical stellar group. We use the NEMO Galactic kinematic code to investigate the orbits of the stream members, and perform a chemical abundance analysis using high resolution spectra taken with the Magellan Clay 6.5 m telescope. Using a χ2 test with the measured abundances for 10 different elements, we find that only half of the purported AB Dor stream members could possibly constitute a statistically chemically homogeneous sample. Some stream members with three-dimensional velocities were hundreds of parsecs from the AB Dor nucleus ~108 yr ago, and hence were unlikely to share a common origin. We conclude that the published lists of AB Dor moving group stream members are unlikely to represent the dispersed remnant of a single star formation episode. A subsample of the stream stars appears to be both statistically chemically homogeneous and in the vicinity of the AB Dor nucleus at birth. Their mean metallicity is [Fe/H] = 0.02 ± 0.02 dex, which we consider representative for the AB Dor group. Finally, we report a strong lower limit on the age of the AB Dor nucleus of >110 Myr based on the pre-main sequence contraction times for K-type members which have reached the main sequence.

Three-cluster dynamics within an ab initio framework

DOE PAGES

Quaglioni, Sofia; Romero-Redondo, Carolina; Navratil, Petr

2013-09-26

In this study, we introduce a fully antisymmetrized treatment of three-cluster dynamics within the ab initio framework of the no-core shell model/resonating-group method. Energy-independent nonlocal interactions among the three nuclear fragments are obtained from realistic nucleon-nucleon interactions and consistent ab initio many-body wave functions of the clusters. The three-cluster Schrödinger equation is solved with bound-state boundary conditions by means of the hyperspherical-harmonic method on a Lagrange mesh. We discuss the formalism in detail and give algebraic expressions for systems of two single nucleons plus a nucleus. Using a soft similarity-renormalization-group evolved chiral nucleon-nucleon potential, we apply the method to amore » 4He+n+n description of 6He and compare the results to experiment and to a six-body diagonalization of the Hamiltonian performed within the harmonic-oscillator expansions of the no-core shell model. Differences between the two calculations provide a measure of core ( 4He) polarization effects.« less

Ab initio study of the effects of thin CsI coatings on the work function of graphite cathodes

NASA Astrophysics Data System (ADS)

Vlahos, Vasilios; Booske, John H.; Morgan, Dane

2007-10-01

Cesium-iodide (CsI)-coated graphite cathodes are promising electron sources for high power microwave generators, but the mechanism driving the improved emission is not well understood. Therefore, an ab initio modeling investigation on the effects of thin CsI coatings on graphite has been carried out. It is demonstrated that the CsI coatings reduce the work function of the system significantly through a mechanism of induced dipoles. The results suggest that work function modification is a major contribution to the improved emission seen when CsI coatings are applied to C.

A novel cry2Ab gene from the indigenous isolate Bacillus thuringiensis subsp. kurstaki.

PubMed

Sevim, Ali; Eryüzlü, Emine; Demirbağ, Zihni; Demir, Ismail

2012-01-01

A novel cry2Ab gene was cloned and sequenced from the indigenous isolate of Bacillus thuringiensis subsp. kurstaki. This gene was designated as cry2Ab25 and its sequence revealed an open reading frame of 1,902 bp encoding a 633 aa protein with calculated molecular mass of 70 kDa and pI value of 8.98. The amino acid sequence of the Cry2Ab25 protein was compared with previously known Cry2Ab toxins, and the phylogenetic relationships among them were determined. The deduced amino acid sequence of the Cry2Ab25 protein showed 99% homology to the known Cry2Ab proteins, except for Cry2Ab10 and Cry2Ab12 with 97% homology, and a variation in one amino acid residue in comparison with all known Cry2Ab proteins. The cry2Ab25 gene was expressed in Escherichia coli BL21(DE3) cells. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the Cry2Ab25 protein is about 70 kDa. The toxin expressed in BL21(DE3) exhibited high toxicity against Malacosoma neustria and Rhagoletis cerasi with 73% and 75% mortality after 5 days of treatment, respectively.

Approximate Quantum Dynamics using Ab Initio Classical Separable Potentials: Spectroscopic Applications.

PubMed

Hirshberg, Barak; Sagiv, Lior; Gerber, R Benny

2017-03-14

Algorithms for quantum molecular dynamics simulations that directly use ab initio methods have many potential applications. In this article, the ab initio classical separable potentials (AICSP) method is proposed as the basis for approximate algorithms of this type. The AICSP method assumes separability of the total time-dependent wave function of the nuclei and employs mean-field potentials that govern the dynamics of each degree of freedom. In the proposed approach, the mean-field potentials are determined by classical ab initio molecular dynamics simulations. The nuclear wave function can thus be propagated in time using the effective potentials generated "on the fly". As a test of the method for realistic systems, calculations of the stationary anharmonic frequencies of hydrogen stretching modes were carried out for several polyatomic systems, including three amino acids and the guanine-cytosine pair of nucleobases. Good agreement with experiments was found. The method scales very favorably with the number of vibrational modes and should be applicable for very large molecules, e.g., peptides. The method should also be applicable for properties such as vibrational line widths and line shapes. Work in these directions is underway.

Ab initio study of the effect of vacancies on the thermal conductivity of boron arsenide

NASA Astrophysics Data System (ADS)

Protik, Nakib Haider; Carrete, Jesús; Katcho, Nebil A.; Mingo, Natalio; Broido, David

2016-07-01

Using a first principles theoretical approach, we show that vacancies give anomalously strong suppression of the lattice thermal conductivity κ of cubic Boron arsenide (BAs), which has recently been predicted to have an exceptionally high κ . This effect is tied to the unusually large phonon lifetimes in BAs and results in a stronger reduction in the BAs κ than occurs in diamond. The large changes in bonding around vacancies cannot be accurately captured using standard perturbative methods and are instead treated here using an ab initio Green function approach. As and B vacancies are found to have similar effects on κ . In contrast, we show that commonly used mass disorder models for vacancies fail for large mass ratio compounds such as BAs, incorrectly predicting much stronger (weaker) phonon scattering when the vacancy is on the heavy (light) atom site. The quantitative treatment given here contributes to fundamental understanding of the effect of point defects on thermal transport in solids and provides guidance to synthesis efforts to grow high quality BAs.

7 CFR Exhibits A-B to Subpart G... - [Reserved

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 12 2013-01-01 2013-01-01 false [Reserved] A Exhibits A-B to Subpart G to Part 1822 Agriculture Regulations of the Department of Agriculture (Continued) RURAL HOUSING SERVICE, RURAL BUSINESS..., Procedures, and Authorizations Exhibits A-B to Subpart G to Part 1822 [Reserved] ...

Creep Behavior of ABS Polymer in Temperature-Humidity Conditions

NASA Astrophysics Data System (ADS)

An, Teagen; Selvaraj, Ramya; Hong, Seokmoo; Kim, Naksoo

2017-04-01

Acrylonitrile-Butadiene-Styrene (ABS), also known as a thermoplastic polymer, is extensively utilized for manufacturing home appliances products as it possess impressive mechanical properties, such as, resistance and toughness. However, the aforementioned properties are affected by operating temperature and atmosphere humidity due to the viscoelasticity property of an ABS polymer material. Moreover, the prediction of optimum working conditions are the little challenging task as it influences the final properties of product. This present study aims to develop the finite element (FE) models for predicting the creep behavior of an ABS polymeric material. In addition, the material constants, which represent the creep properties of an ABS polymer material, were predicted with the help of an interpolation function. Furthermore, a comparative study has been made with experiment and simulation results to verify the accuracy of developed FE model. The results showed that the predicted value from FE model could agree well with experimental data as well it can replicate the actual creep behavior flawlessly.

Ab interno trabeculectomy: patient selection and perspectives

PubMed Central

Vinod, Kateki; Gedde, Steven J

2016-01-01

Ab interno trabeculectomy is one among several recently introduced minimally invasive glaucoma surgeries that avoid a conjunctival incision and full-thickness sclerostomy involved in traditional glaucoma surgery. Ablation of the trabecular meshwork and inner wall of Schlemm’s canal is performed in an arcuate fashion via a clear corneal incision, alone or in combination with phacoemulsification cataract surgery. Intraocular pressure reduction following ab interno trabeculectomy is limited by resistance in distal outflow pathways and generally stabilizes in the mid-to-high teens. Relief of medication burden has been demonstrated by some studies. A very low rate of complications, most commonly transient hyphema and intraocular pressure elevations in the immediate postoperative period, have been reported. However, available data are derived from small retrospective and prospective case series. Randomized, controlled trials are needed to better elucidate the potential merits of ab interno trabeculectomy in the combined setting versus phacoemulsification cataract surgery alone and to compare it with other minimally invasive glaucoma surgeries. PMID:27574396

Method for the separation of high impact polystyrene (HIPS) and acrylonitrile butadiene styrene (ABS) plastics

DOEpatents

Jody, Bassam J.; Arman, Bayram; Karvelas, Dimitrios E.; Pomykala, Jr., Joseph A.; Daniels, Edward J.

1997-01-01

An improved method is provided for separating acrylonitrile butadiene styrene (ABS) and high impact polystyrene (HIPS) plastics from each other. The ABS and HIPS plastics are shredded to provide a selected particle size. The shredded particles of the ABS and HIPS plastics are applied to a solution having a solution density in a predefined range between 1.055 gm/cm.sup.3 and 1.07 gm/cm.sup.3, a predefined surface tension in a range between 22 dynes/cm to 40 dynes/cm and a pH in the range of 1.77 and 2.05. In accordance with a feature of the invention, the novel method is provided for separating ABS and HIPS, two solid thermoplastics which have similar densities by selectively modifying the effective density of the HIPS using a binary solution with the appropriate properties, such as pH, density and surface tension, such as a solution of acetic acid and water or a quaternary solution having the appropriate density, surface tension, and pH.

Growth suppression of colorectal cancer by plant-derived multiple mAb CO17-1A × BR55 via inhibition of ERK1/2 phosphorylation.

PubMed

Kwak, Dong Hoon; Moussavou, Ghislain; Lee, Ju Hyoung; Heo, Sung Youn; Ko, Kisung; Hwang, Kyung-A; Jekal, Seung-Joo; Choo, Young-Kug

2014-11-14

We have generated the transgenic Tabaco plants expressing multiple monoclonal antibody (mAb) CO7-1A × BR55 by cross-pollinating with mAb CO17-1A and mAb BR55. We have demonstrated the anti-cancer effect of plant-derived multiple mAb CO17-1A × BR55. We find that co-treatment of colorectal mAbs (anti-epithelial cellular adhesion molecule (EpCAM), plant-derived monoclonal antibody (mAb(P)) CO17-1A and mAb(P) CO17-1A × BR55) with RAW264.7 cells significantly inhibited the cell growth in SW620 cancer cells. In particular, multi mAb(P) CO17-1A × BR55 significantly and efficiently suppressed the growth of SW620 cancer cells compared to another mAbs. Apoptotic death-positive cells were significantly increased in the mAb(P) CO17-1A × BR55-treated. The mAb(P) CO17-1A × BR55 treatment significantly decreased the expression of B-Cell lymphoma-2 (BCl-2), but the expression of Bcl-2-associated X protein (Bax), and cleaved caspase-3 were markedly increased. In vivo, the mAb(P) CO17-1A × BR55 significantly and efficiently inhibited the growth of colon tumors compared to another mAbs. The apoptotic cell death and inhibition of pro-apoptotic proteins expression were highest by treatment with mAb(P) CO17-1A × BR55. In addition, the mAb(P) CO17-1A × BR55 significantly inhibited the extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation in cancer cells and tumors. Therefore, this study results suggest that multiple mAb(P) CO17-1A × BR55 has a significant effect on apoptosis-mediated anticancer by suppression of ERK1/2 phosphorylation in colon cancer compared to another mAbs. In light of these results, further clinical investigation should be conducted on mAb(P) CO17-1A × BR55 to determine its possible chemopreventive and/or therapeutic efficacy against human colon cancer.

34 CFR Appendixes A-B to Part 682 - [Reserved

Code of Federal Regulations, 2010 CFR

2010-07-01

... 34 Education 3 2010-07-01 2010-07-01 false [Reserved] A Appendixes A-B to Part 682 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION FEDERAL FAMILY EDUCATION LOAN (FFEL) PROGRAM Appendixes A-B to Part 682 [Reserved] ...

Quantum interference in multi-branched molecules: The exact transfer matrix solutions.

PubMed

Jiang, Yu

2017-12-07

We present a transfer matrix formalism for studying quantum interference in a single molecule electronic system with internal branched structures. Based on the Schrödinger equation with the Bethe ansatz and employing Kirchhoff's rule for quantum wires, we derive a general closed-form expression for the transmission and reflection amplitudes of a two-port quantum network. We show that the transport through a molecule with complex internal structures can be reduced to that of a single two-port scattering unit, which contains all the information of the original composite molecule. Our method allows for the calculation of the transmission coefficient for various types of individual molecular modules giving rise to different resonant transport behaviors such as the Breit-Wigner, Fano, and Mach-Zehnder resonances. As an illustration, we first re-derive the transmittance of the Aharonov-Bohm ring, and then we apply our formulation to N identical parity-time (PT)-symmetric potentials, connected in series as well as in parallel. It is shown that the spectral singularities and PT-symmetric transitions of single scattering cells may be observed in coupled systems. Such transitions may occur at the same or distinct values of the critical parameters, depending on the connection modes under which the scattering objects are coupled.

Reversibility and measurement in quantum computing

NASA Astrophysics Data System (ADS)

Leãao, J. P.

1998-03-01

The relation between computation and measurement at a fundamental physical level is yet to be understood. Rolf Landauer was perhaps the first to stress the strong analogy between these two concepts. His early queries have regained pertinence with the recent efforts to developed realizable models of quantum computers. In this context the irreversibility of quantum measurement appears in conflict with the requirement of reversibility of the overall computation associated with the unitary dynamics of quantum evolution. The latter in turn is responsible for the features of superposition and entanglement which make some quantum algorithms superior to classical ones for the same task in speed and resource demand. In this article we advocate an approach to this question which relies on a model of computation designed to enforce the analogy between the two concepts instead of demarcating them as it has been the case so far. The model is introduced as a symmetrization of the classical Turing machine model and is then carried on to quantum mechanics, first as a an abstract local interaction scheme (symbolic measurement) and finally in a nonlocal noninteractive implementation based on Aharonov-Bohm potentials and modular variables. It is suggested that this implementation leads to the most ubiquitous of quantum algorithms: the Discrete Fourier Transform.

Quantum gas microscopy of the interacting Harper-Hofstadter system

NASA Astrophysics Data System (ADS)

Tai, M. Eric; Lukin, Alex; Preiss, Philipp; Rispoli, Matthew; Schittko, Robert; Kaufman, Adam; Greiner, Markus

2016-05-01

At the heart of many topological states is the underlying gauge field. One example of a gauge field is the magnetic field which causes the deflection of a moving charged particle. This behavior can be understood through the Aharonov-Bohm phase that a particle acquires upon traversing a closed path. Gauge fields give rise to novel states of matter that cannot be described with symmetry breaking. Instead, these states, e.g. fractional quantum Hall (FQH) states, are characterized by topological invariants, such as the Chern number. In this talk, we report on experimental results upon introducing a gauge field in a system of strongly-interacting ultracold Rb87 atoms confined to a 2D optical lattice. With single-site resolution afforded by a quantum gas microscope, we can prepare a fixed atom number and project hard walls. With an artificial gauge field, this quantum simulator realizes the Harper-Hofstadter Hamiltonian. We can independently control the two tunneling strengths as well as dynamically change the flux. This flexibility enables studies of topological phenomena from many perspectives, e.g. site-resolved images of edge currents. With the strong on-site interactions possible in our system, these experiments will pave the way to observing FQH-like states in a lattice.

Roles of Salmonella typhimurium umuDC and samAB in UV mutagenesis and UV sensitivity.

PubMed Central

Nohmi, T; Yamada, M; Watanabe, M; Murayama, S Y; Sofuni, T

1992-01-01

Expression of the umuDC operon is required for UV mutagenesis and most chemical mutagenesis in Escherichia coli. The closely related species Salmonella typhimurium has two sets of umuDC-like operons; the samAB operon is located in a 60-MDa cryptic plasmid, while the S. typhimurium umuDC (umuDCST) operon resides in a chromosome. The roles of these two umuDC-like operons in UV mutagenesis and UV sensitivity of S. typhimurium were investigated. A pBR322-derived plasmid carrying the samAB operon more efficiently restored UV mutability to a umuD44 strain and a umuC122::Tn5 strain of E. coli than a plasmid carrying the umuDCST operon did. When the umuDCST operon was specifically deleted from the chromosome of S. typhimurium TA2659, the resulting strain was not UV mutable and was more sensitive to the killing effect of UV irradiation than the parent strain was. Curing of the 60-MDa cryptic plasmid carrying the samAB operon did not influence the UV mutability of strain TA2659 but did increase its resistance to UV killing. A pSC101-derived plasmid carrying the samAB operon did not restore UV mutability to a umuD44 strain of E. coli, whereas pBR322- or pBluescript-derived plasmids carrying the samAB operon efficiently did restore UV mutability. We concluded that the umuDCST operon plays a major role in UV mutagenesis in S. typhimurium and that the ability of the samAB operon to promote UV mutagenesis is strongly affected by gene dosage. Possible reasons for the poor ability of samAB to promote UV mutagenesis when it is present on low-copy-number plasmids are discussed. Images PMID:1400244

An effective treatment approach of DPP-IV inhibitor encapsulated polymeric nanoparticles conjugated with anti-CD-4 mAb for type 1 diabetes.

PubMed

Thondawada, Mahesh; Wadhwani, Ashish Devidas; S Palanisamy, Dhanabal; Rathore, Hanumant Singh; Gupta, Ramesh C; Chintamaneni, Pavan Kumar; Samanta, Malay K; Dubala, Anil; Varma, Sameer; Krishnamurthy, Praveen T; Gowthamarajan, Kuppusamy

2018-07-01

Nanotechnology based biomedical approaches and surface modification techniques made it easier for targeting specific site and improving the treatment efficacy. The present study reports on targeted polymeric nanoparticles conjugated with antibody as a site-specific carrier system for effective treatment of type 1 diabetes. Sitagliptin (SP)-loaded Poly (lactic-co-glycolic acid) (PLGA) nanoparticles (NP) were prepared by nanoprecipitation cum solvent evaporation method and were characterized in terms of morphology, size, surface charge, and entrapment efficiency. Optimized batch demonstrated a particle size of 105.24 nm, with significant entrapment efficacy. In vitro release studies exhibited a controlled release pattern of 67.76 ± 1.30% in 24 h, and a maximum of 96.59 ± 1.26% at the end of 48 h. Thiol groups were introduced on the surface of SP-NPs whose concentration on SP-NPs was 27 ± 2.6 mmol/mol PLGA-NPs, anti-CD4 antibody clone Q4120 was conjugated to the thiolated SP-NPs via a sulfo-MBS cross-linker, ∼70% conjugation was observed. The in vitro cytotoxicity studies performed on RIN-5 F cells for mAb-SP-NPs presented an IC 50 of 76 µg/mL, and the insulin release assay had revealed an increased release at 5.15 ± 0.16 IU/mL. The results indicate that mAb-SP-NPs allowed a controlled release of SP and thereby produced insulin levels comparable with control. Therefore, mAb-SP-NPs system appears to be effective in the treatment of auto immune diabetes, subject to further analysis.

A KINE-CHEMICAL INVESTIGATION OF THE AB DOR MOVING GROUP 'STREAM'

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barenfeld, Scott A.; Bubar, Eric J.; Mamajek, Eric E.

2013-03-20

The AB Dor Moving Group consists of a 'nucleus' of {approx}10 stars at d {approx_equal} 20 pc, along with dozens of purported 'stream' members distributed across the sky. We perform a chemical and kinematic analysis of a subsample of AB Dor stream stars to test whether they constitute a physical stellar group. We use the NEMO Galactic kinematic code to investigate the orbits of the stream members, and perform a chemical abundance analysis using high resolution spectra taken with the Magellan Clay 6.5 m telescope. Using a {chi}{sup 2} test with the measured abundances for 10 different elements, we findmore » that only half of the purported AB Dor stream members could possibly constitute a statistically chemically homogeneous sample. Some stream members with three-dimensional velocities were hundreds of parsecs from the AB Dor nucleus {approx}10{sup 8} yr ago, and hence were unlikely to share a common origin. We conclude that the published lists of AB Dor moving group stream members are unlikely to represent the dispersed remnant of a single star formation episode. A subsample of the stream stars appears to be both statistically chemically homogeneous and in the vicinity of the AB Dor nucleus at birth. Their mean metallicity is [Fe/H] = 0.02 {+-} 0.02 dex, which we consider representative for the AB Dor group. Finally, we report a strong lower limit on the age of the AB Dor nucleus of >110 Myr based on the pre-main sequence contraction times for K-type members which have reached the main sequence.« less

ABS 3D printed solutions for cryogenic applications

NASA Astrophysics Data System (ADS)

Bartolomé, E.; Bozzo, B.; Sevilla, P.; Martínez-Pasarell, O.; Puig, T.; Granados, X.

2017-03-01

3D printing has become a common, inexpensive and rapid prototyping technique, enabling the ad hoc fabrication of complex shapes. In this paper, we demonstrate that 3D printed objects in ABS can be used at cryogenic temperatures, offering flexible solutions in different fields. Firstly, a thermo-mechanical characterization of ABS 3D printed specimens at 77 K is reported, which allowed us to delimit the type of cryogenic uses where 3D printed pieces may be implemented. Secondly, we present three different examples where ABS 3D printed objects working at low temperatures have provided specific solutions: (i) SQUID inserts for angular magnetometry (low temperature material characterization field); (ii) a cage support for a metamaterial ;magnetic concentrator; (superconductivity application), and (iii) dedicated tools for cryopreservation in assisted reproductive techniques (medicine field).

Measurement of filling factor 5/2 quasiparticle interference with observation of charge e/4 and e/2 period oscillations.

PubMed

Willett, R L; Pfeiffer, L N; West, K W

2009-06-02

A standing problem in low-dimensional electron systems is the nature of the 5/2 fractional quantum Hall (FQH) state: Its elementary excitations are a focus for both elucidating the state's properties and as candidates in methods to perform topological quantum computation. Interferometric devices may be used to manipulate and measure quantum Hall edge excitations. Here we use a small-area edge state interferometer designed to observe quasiparticle interference effects. Oscillations consistent in detail with the Aharonov-Bohm effect are observed for integer quantum Hall and FQH states (filling factors nu = 2, 5/3, and 7/3) with periods corresponding to their respective charges and magnetic field positions. With these factors as charge calibrations, periodic transmission through the device consistent with quasiparticle charge e/4 is observed at nu = 5/2 and at lowest temperatures. The principal finding of this work is that, in addition to these e/4 oscillations, periodic structures corresponding to e/2 are also observed at 5/2 nu and at lowest temperatures. Properties of the e/4 and e/2 oscillations are examined with the device sensitivity sufficient to observe temperature evolution of the 5/2 quasiparticle interference. In the model of quasiparticle interference, this presence of an effective e/2 period may empirically reflect an e/2 quasiparticle charge or may reflect multiple passes of the e/4 quasiparticle around the interferometer. These results are discussed within a picture of e/4 quasiparticle excitations potentially possessing non-Abelian statistics. These studies demonstrate the capacity to perform interferometry on 5/2 excitations and reveal properties important for understanding this state and its excitations.

History of California's AB 1725 and Its Major Provisions.

ERIC Educational Resources Information Center

Livingston, Tab

This paper addresses the history of California's Assembly Bill 1725 (AB 1725) legislation and describes its major provisions. Signed in 1988 by Governor George Deukmejian, AB 1725's focus is to emphasize the new role of California community colleges as postsecondary institutions committed to transferring students, offering remedial courses, and…

Acute side effects after consumption of the new synthetic cannabinoids AB-CHMINACA and MDMB-CHMICA.

PubMed

Hermanns-Clausen, Maren; Müller, Dieter; Kithinji, Josephine; Angerer, Verena; Franz, Florian; Eyer, Florian; Neurath, Hartmud; Liebetrau, Gesine; Auwärter, Volker

2018-06-01

In 2014, the "European Monitoring Centre for Drugs and Drug Addiction" (EMCDDA) reported on 30 novel synthetic cannabinoids (SCs). Among these were indole- and indazole-based valine derivatives with a cyclohexylmethyl side chain (e.g., AB-CHMINACA and MDMB-CHMICA), which represent a new class of SCs. A prospective observational study of patients treated in emergency departments (EDs) after the intake of SCs was conducted. Clinical and laboratory data were combined and reported to a poison control centre. Serum and/or urine samples of ED patients were analyzed using LC-MS/MS. Forty four patients (39 male, five female, 12-48 years) were included. AB-CHMINACA (MDMB-CHMICA) was identified in 20 (19) serum samples, and in 21 (25) urine samples, respectively. In 19 of the cases, more than one SC was present. Other psychoactive substances (mainly amfetamines) were identified in seven cases, but in five out of these in urine samples only. Based on the Poison Severity Score, severity of poisoning was minor (4), moderate (31) or severe (9). Most frequently reported neuropsychiatric symptoms were CNS-depression (n = 21, 61%), disorientation (n = 20, 45%), generalized seizures (n = 12, 27%), combativeness (n = 8, 18%) and extreme agitation (n = 7, 16%). Duration of symptoms lasting 24 hours or longer occurred in 15 cases (34%). The prevalence of certain neuropsychiatric symptoms was higher in our study than in former reports after the intake of SCs of the aminoalkylindole-type (first generation) SCs. In addition, severe poisoning and duration of symptoms were also higher. In this study, the valine derivative AB-CHMINACA and the tert-leucine derivative MDMB-CHMICA ("third generation of SCs") seem to be associated with more severe clinical toxicity than was previously reported in patients exposed to earlier generation SCs such as JWH-018. However, this observation needs to be confirmed with a larger cohort of patients with analytically confirmed abuse of

Radiolytic Synthesis of Pt-Particle/ABS Catalysts for H₂O₂ Decomposition in Contact Lens Cleaning.

PubMed

Ohkubo, Yuji; Aoki, Tomonori; Seino, Satoshi; Mori, Osamu; Ito, Issaku; Endo, Katsuyoshi; Yamamura, Kazuya

2017-08-23

A container used in contact lens cleaning requires a Pt plating weight of 1.5 mg for H₂O₂ decomposition although Pt is an expensive material. Techniques that decrease the amount of Pt are therefore needed. In this study, Pt nanoparticles instead of Pt plating film were supported on a substrate of acrylonitrile-butadiene-styrene copolymer (ABS). This was achieved by the reduction of Pt ions in an aqueous solution containing the ABS substrate using high-energy electron-beam irradiation. Pt nanoparticles supported on the ABS substrate (Pt-particle/ABS) had a size of 4-10 nm. The amount of Pt required for Pt-particle/ABS was 250 times less than that required for an ABS substrate covered with Pt plating film (Pt-film/ABS). The catalytic activity for H₂O₂ decomposition was estimated by measuring the residual H₂O₂ concentration after immersing the catalyst for 360 min. The Pt-particle/ABS catalyst had a considerably higher specific catalytic activity for H₂O₂ decomposition than the Pt-film/ABS catalyst. In addition, sterilization performance was estimated from the initial rate of H₂O₂ decomposition over 60 min. The Pt-particle/ABS catalyst demonstrated a better sterilization performance than the Pt-film/ABS catalyst. The difference between Pt-particle/ABS and Pt-film/ABS was shown to reflect the size of the O₂ bubbles formed during H₂O₂ decomposition.

A note on AB INITIO semiconductor band structures

NASA Astrophysics Data System (ADS)

Fiorentini, Vincenzo

1992-09-01

We point out that only the internal features of the DFT ab initio theoretical picture of a crystal should be used in a consistent ab initio calculation of the band structure. As a consequence, we show that ground-state band structure calculations should be performed for the system in equilibrium at zero pressure, i.e. at the computed equilibrium cell volume ω th. Examples of consequences of this attitude are considered.

Ab initio NMR parameters of BrCH3 and ICH3 with relativistic and vibrational corrections

NASA Astrophysics Data System (ADS)

Uhlíková, Tereza; Urban, Štěpán

2018-05-01

This study is focused on two effects identified when NMR parameters are calculated based on first principles. These effects are 1. vibrational correction of properties when using ab initio optimized equilibrium geometry; 2. relativistic effects and limits of using the Flygare equation. These effects have been investigated and determined for nuclear spin-rotation constants and nuclear magnetic shieldings for the CH3Br and CH3I molecules. The most significant result is the difference between chemical shieldings determined based on the ab initio relativistic four-component Dirac-Coulomb Hamiltonian and chemical shieldings calculated using experimental values and the Flygare equation. This difference is approximately 320 ppm and 1290 ppm for 79Br and 127I in the CH3X molecule, respectively.

Global analysis of double-strand break processing reveals in vivo properties of the helicase-nuclease complex AddAB

PubMed Central

Badrinarayanan, Anjana; Cisse, Ibrahim I.

2017-01-01

In bacteria, double-strand break (DSB) repair via homologous recombination is thought to be initiated through the bi-directional degradation and resection of DNA ends by a helicase-nuclease complex such as AddAB. The activity of AddAB has been well-studied in vitro, with translocation speeds between 400–2000 bp/s on linear DNA suggesting that a large section of DNA around a break site is processed for repair. However, the translocation rate and activity of AddAB in vivo is not known, and how AddAB is regulated to prevent excessive DNA degradation around a break site is unclear. To examine the functions and mechanistic regulation of AddAB inside bacterial cells, we developed a next-generation sequencing-based approach to assay DNA processing after a site-specific DSB was introduced on the chromosome of Caulobacter crescentus. Using this assay we determined the in vivo rates of DSB processing by AddAB and found that putative chi sites attenuate processing in a RecA-dependent manner. This RecA-mediated regulation of AddAB prevents the excessive loss of DNA around a break site, limiting the effects of DSB processing on transcription. In sum, our results, taken together with prior studies, support a mechanism for regulating AddAB that couples two key events of DSB repair–the attenuation of DNA-end processing and the initiation of homology search by RecA–thereby helping to ensure that genomic integrity is maintained during DSB repair. PMID:28489851

Identification of Bacillus thuringiensis Cry1AbMod binding-proteins from Spodoptera frugiperda.

PubMed

Martínez de Castro, Diana L; García-Gómez, Blanca I; Gómez, Isabel; Bravo, Alejandra; Soberón, Mario

2017-12-01

Bacillus thuringiensis Cry toxins are currently used for pest control in transgenic crops but evolution of resistance by the insect pests threatens the use of this technology. The Cry1AbMod toxin was engineered to lack the alpha helix-1 of the parental Cry1Ab toxin and was shown to counter resistance to Cry1Ab and Cry1Ac toxins in different insect species including the fall armyworm Spodoptera frugiperda. In addition, Cry1AbMod showed enhanced toxicity to Cry1Ab-susceptible S. frugiperda populations. To gain insights into the mechanisms of this Cry1AbMod-enhanced toxicity, we isolated the Cry1AbMod toxin binding proteins from S. frugiperda brush border membrane vesicles (BBMV), which were identified by pull-down assay and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The LC-MS/MS results indicated that Cry1AbMod toxin could bind to four classes of aminopeptidase (N1, N3, N4 y N5) and actin, with the highest amino acid sequence coverage acquired for APN 1 and APN4. In addition to these proteins, we found other proteins not previously described as Cry toxin binding proteins. This is the first report that suggests the interaction between Cry1AbMod and APN in S. frugiperda. Copyright © 2017 Elsevier Inc. All rights reserved.

Macrolide resistance in Legionella pneumophila: the role of LpeAB efflux pump.

PubMed

Massip, Clémence; Descours, Ghislaine; Ginevra, Christophe; Doublet, Patricia; Jarraud, Sophie; Gilbert, Christophe

2017-05-01

A previous study on 12 in vitro -selected azithromycin-resistant Legionella pneumophila lineages showed that ribosomal mutations were major macrolide resistance determinants. In addition to these mechanisms that have been well described in many species, mutations upstream of lpeAB operon, homologous to acrAB in Escherichia coli , were identified in two lineages. In this study, we investigated the role of LpeAB and of these mutations in macrolide resistance of L. pneumophila . The role of LpeAB was studied by testing the antibiotic susceptibility of WT, deleted and complemented L. pneumophila Paris strains. Translational fusion experiments using GFP as a reporter were conducted to investigate the consequences of the mutations observed in the upstream sequence of lpeAB operon. We demonstrated the involvement of LpeAB in an efflux pump responsible for a macrolide-specific reduced susceptibility of L. pneumophila Paris strain. Mutations in the upstream sequence of lpeAB operon were associated with an increased protein expression. Increased expression was also observed under sub-inhibitory macrolide concentrations in strains with both mutated and WT promoting regions. LpeAB are components of an efflux pump, which is a macrolide resistance determinant in L. pneumophila Paris strain. Mutations observed in the upstream sequence of lpeAB operon in resistant lineages led to an overexpression of this efflux pump. Sub-inhibitory concentrations of macrolides themselves participated in upregulating this efflux and could constitute a first step in the acquisition of a high macrolide resistance level. © The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

PD-L1 mAb Treats Ischemic Stroke by Controlling CNS Inflammation

PubMed Central

Bodhankar, Sheetal; Chen, Yingxin; Lapato, Andrew; Dotson, Abby L.; Wang, Jianming; Vandenbark, Arthur A.; Saugstad, Julie A.; Offner, Halina

2015-01-01

Background and Purpose Both pathogenic and regulatory immune processes are involved in the middle cerebral artery occlusion (MCAO) model of experimental stroke, including interactions involving the Programmed Death 1 (PD-1) receptor and its two ligands, PD-L1 and PD-L2. Although PD-1 reduced stroke severity, PD-L1 and PD-L2 appeared to play pathogenic roles, suggesting use of anti-PD-L monoclonal Ab (mAb) therapy for MCAO. Methods Male C57BL/6 mice were treated with a single dose of anti-PD-L1 mAb 4 h after MCAO and evaluated for clinical, histological and immunological changes after 96 h reperfusion. Results Blockade of the PD-L1 checkpoint using a single injection of 200μg anti-PD-L1 mAb given i.v. 4 h after occlusion significantly reduced MCAO infarct volumes and improved neurological outcomes after 96 h reperfusion. Treatment partially reversed splenic atrophy and decreased CNS infiltrating immune cells concomitant with enhanced appearance of CD8+ regulatory T cells in the lesioned CNS hemisphere. Conclusions This study demonstrates for the first time the beneficial therapeutic effects of PD-L1 checkpoint blockade on MCAO, thus validating proposed mechanisms obtained in our previous studies using PD-1 and PD-L deficient mice. These results provide strong support for use of available humanized anti-PD-L1 antibodies for treatment of human stroke subjects. PMID:26306753

Laboratory toxicity studies demonstrate no adverse effects of Cry1Ab and Cry3Bb1 to larvae of Adalia bipunctata (Coleoptera: Coccinellidae): the importance of study design.

PubMed

Alvarez-Alfageme, Fernando; Bigler, Franz; Romeis, Jörg

2011-06-01

Scientific studies are frequently used to support policy decisions related to transgenic crops. Schmidt et al., Arch Environ Contam Toxicol 56:221-228 (2009) recently reported that Cry1Ab and Cry3Bb were toxic to larvae of Adalia bipunctata in direct feeding studies. This study was quoted, among others, to justify the ban of Bt maize (MON 810) in Germany. The study has subsequently been criticized because of methodological shortcomings that make it questionable whether the observed effects were due to direct toxicity of the two Cry proteins. We therefore conducted tritrophic studies assessing whether an effect of the two proteins on A. bipunctata could be detected under more realistic routes of exposure. Spider mites that had fed on Bt maize (events MON810 and MON88017) were used as carriers to expose young A. bipunctata larvae to high doses of biologically active Cry1Ab and Cry3Bb1. Ingestion of the two Cry proteins by A. bipunctata did not affect larval mortality, weight, or development time. These results were confirmed in a subsequent experiment in which A. bipunctata were directly fed with a sucrose solution containing dissolved purified proteins at concentrations approximately 10 times higher than measured in Bt maize-fed spider mites. Hence, our study does not provide any evidence that larvae of A. bipunctata are sensitive to Cry1Ab and Cry3Bb1 or that Bt maize expressing these proteins would adversely affect this predator. The results suggest that the apparent harmful effects of Cry1Ab and Cry3Bb1 reported by Schmidt et al., Arch Environ Contam Toxicol 56:221-228 (2009) were artifacts of poor study design and procedures. It is thus important that decision-makers evaluate the quality of individual scientific studies and do not view all as equally rigorous and relevant.

Effects of boron-nitride substrates on Stone-Wales defect formation in graphene: An ab initio molecular dynamics study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, K.; Xiao, H. Y.; Zhang, Y.

2014-05-19

Ab initio molecular dynamics simulations are performed to investigate the effects of a boron nitride (BN) substrate on Stone-Wales (SW) defect formation and recovery in graphene. It is found that SW defects can be created by an off-plane recoil atom that interacts with the BN substrate. A mechanism with complete bond breakage for formation of SW defects in suspended graphene is also revealed for recoils at large displacement angles. In addition, further irradiation can result in recovery of the SW defects through a bond rotation mechanism in both graphene and graphene/BN, and the substrate has little effect on the recoverymore » process. This study indicates that the BN substrate enhances the irradiation resistance of graphene.« less

MiR-181a/b induce the growth, invasion, and metastasis of neuroblastoma cells through targeting ABI1.

PubMed

Liu, Xiaodan; Peng, Hongxia; Liao, Wang; Luo, Ailing; Cai, Mansi; He, Jing; Zhang, Xiaohong; Luo, Ziyan; Jiang, Hua; Xu, Ling

2018-05-26

Neuroblastoma is a pediatric malignancy, and the clinical phenotypes range from localized tumors with excellent outcomes to widely metastatic disease in which long-term survival is approximately 40%, despite intensive therapy. Emerging evidence suggests that aberrant miRNA regulation plays a role in neuroblastoma, but the miRNA functions and mechanisms remain unknown. miR-181 family members were detected in 32 neuroblastoma patients, and the effects of miR-181a/b on cell viability, invasion, and migration were evaluated in vitro and in vivo. A parallel global mRNA expression profile was obtained for neuroblastoma cells overexpressing miR-181a. The potential targets of miR-181a/b were validated. miR-181a/b expression levels were positively associated with MYCN amplification and neuroblastoma aggressiveness. Moreover, ectopic miR-181a/b expression significantly induced the growth and invasion of neuroblastoma cells in vitro and in vivo. Microarray analysis revealed that mRNAs were consistently downregulated after miR-181a overexpression, leading to cell migration. In addition, the expression of ABI1 was suppressed by miR-181a/b, and ABI1 was validated as a direct target of miR-181a/b. We concluded that miR-181a/b were significantly upregulated in aggressive neuroblastoma, which enhanced its tumorigenesis and progression by suppressing the expression of ABI1. © 2018 Wiley Periodicals, Inc.

SEER Abstracting Tool (SEER*Abs)

Cancer.gov

With this customizable tool, registrars can collect and store data abstracted from medical records. Download the software and find technical support and reference manuals. SEER*Abs has features for creating records, managing abstracting work and data, accessing reference data, and integrating edits.

Radioiodine Labeled Anti-MIF McAb: A Potential Agent for Inflammation Imaging

PubMed Central

Zhang, Chao; Hou, Gui-hua; Han, Jian-kui; Song, Jing; Liang, Ting

2007-01-01

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that may play a role in the pathogenesis of inflammation. Radiolabeled anti-MIF McAb can be used to detect in vivo inflammatory changes. The objective of this study was to investigate in vivo biology of radioiodinated anti-MIF McAb using the inflammation model mice. Anti-MIF McAb was radioiodinated with NaI125 by Iodogen method. Animal models were induced in the mice by intramuscular injection of S. aureus, E. coli, and turpentine oil. The biodistribution studies with radioiodinated anti-MIF McAb were performed on inflammation mice. The relationship between inflammatory lesions and anti-MIF McAb binding was investigated using the percent of injected dose per gram tissue (% ID/g) of tissue samples and whole-body autoradiography. The radioactivity of I125-anti-MIF McAb in the inflammatory tissue increased gradually for three inflammation models. The highest uptake was found in S. aureus group and the lowest was in E. coli group. The uptake in turpentine oil group was average. Whole-body autoradiography showed that all inflammation foci could be visualized clearly from 24 hours after injection, but 48 hours images were much clearer in accordance with the high T/NT ratio. These results demonstrate the ability of radioiodinated anti-MIF McAb to measure in vivo inflammatory events represented by high expression of MIF and suggests that radiolabeled anti-MIF McAb warrants further investigation as a potential inflammation-seeking agent for imaging to detect inflammatory disorders. PMID:18317509

Comparative study of thiophilic functionalised matrices for polyclonal F(ab')2 purification.

PubMed

Kumpalume, Peter; Slater, Nigel K H

2004-01-02

Thiophilic adsorbents have been developed using divinyl sulfone or epoxy activated Streamline quartz base matrix. Their capacity and selectivity for binding polyclonal F(ab')2 fragments generated by whole serum proteolysis was tested. Except for epoxy activated guanidine, all the adsorbents displayed high selectivity for F(ab')2 with dynamic binding capacities ranging from 3 to 10 mg/ml of adsorbent. Thiol immobilised ligands adsorbed more F(ab')2 and the recovery was equal to or more than that from amino immobilised ligands. All adsorbents showed good selectivity for IgG and the dynamic binding capacities were better than for F(ab')2.

Radiator-induced erythema ab igne in 8-year-old girl.

PubMed

Brzezinski, Piotr; Ismail, Samir; Chiriac, Anca

2014-04-01

The cutaneous lesion of erythema ab Igne are characterized by a reticulate erythema, hyperpigmentation, fine scaling, epidermal atrophy and telangiectasias, and reticulated erythema. We report a case of erythema ab igne on the hands of a 8-year-old girl, induced by classic homemade radiator.

Cost-Effective Method for Free-Energy Minimization in Complex Systems with Elaborated Ab Initio Potentials.

PubMed

Bistafa, Carlos; Kitamura, Yukichi; Martins-Costa, Marilia T C; Nagaoka, Masataka; Ruiz-López, Manuel F

2018-06-12

We describe a method to locate stationary points in the free-energy hypersurface of complex molecular systems using high-level correlated ab initio potentials. In this work, we assume a combined QM/MM description of the system although generalization to full ab initio potentials or other theoretical schemes is straightforward. The free-energy gradient (FEG) is obtained as the mean force acting on relevant nuclei using a dual level strategy. First, a statistical simulation is carried out using an appropriate, low-level quantum mechanical force-field. Free-energy perturbation (FEP) theory is then used to obtain the free-energy derivatives for the target, high-level quantum mechanical force-field. We show that this composite FEG-FEP approach is able to reproduce the results of a standard free-energy minimization procedure with high accuracy, while simultaneously allowing for a drastic reduction of both computational and wall-clock time. The method has been applied to study the structure of the water molecule in liquid water at the QCISD/aug-cc-pVTZ level of theory, using the sampling from QM/MM molecular dynamics simulations at the B3LYP/6-311+G(d,p) level. The obtained values for the geometrical parameters and for the dipole moment of the water molecule are within the experimental error, and they also display an excellent agreement when compared to other theoretical estimations. The developed methodology represents therefore an important step toward the accurate determination of the mechanism, kinetics, and thermodynamic properties of processes in solution, in enzymes, and in other disordered chemical systems using state-of-the-art ab initio potentials.

In vitro and in vivo evaluation of osteoinductivity and bone fusion ability of an activin a/BMP2 chimera (AB204): a comparison study between AB204 and rhBMP-2.

PubMed

Zheng, Guang Bin; Lee, Jae Hyup; Jin, Yuan-Zhe

2017-12-01

This study compared osteoinductivity and osteogenic capacity between AB204 and rhBMP-2 using hMSCs in vitro and a beagle's posterolateral spinal fusion model. Cultured hMSCs were treated with AB204 or rhBMP-2 with low to high doses. Three male beagles were performed posterolateral spinal fusion with biphasic calcium phosphate (2 ml) + AB204 or rhBMP-2 (20, 50 or 200 µg). They were euthanized after 8 weeks. The fusion rate and bone formation of spine samples were examined. AB204 had higher alkaline phosphatase activity, mineralization and osteogenic-related gene expression than rhBMP-2. Fusion rates in all rhBMP-2 groups were 0. They were 100% for 50 μg and 200 μg AB204 groups. Therefore, AB204 showed higher osteogenicity than rhBMP-2. It could be a better bone graft substitute.

Rescue of failed filtering blebs with ab interno trephination.

PubMed

Shihadeh, Wisam A; Ritch, Robert; Liebmann, Jeffrey M

2006-06-01

We evaluated the effectiveness of ab interno automated trephination as a technique for rescuing failed mature filtering blebs. A retrospective chart review of 40 failed blebs of 38 patients who had a posttrephination follow-up period of at least 3 months was done. With success defined as intraocular pressure (IOP) <21 mm Hg and at least a 20% reduction from baseline on the same or fewer number of pretrephination medications, 30/40 eyes (75%) fit these criteria over the entire course of follow-up. Among all 40 eyes, there was a significant reduction of IOP from pretrephination to 3 months (P<.001). The percentage of patients requiring 2 or more medications declined from 90% pretrephination to 21% at 3 months (P<.0001), and was stable thereafter. Some patients were able to eliminate all medications. Patients who did not meet the criteria of success regained successful IOP control with other modalities of management. Complications were few. We believe that ab interno trephination is an excellent option for rescuing selected failed filtering blebs.

FeP(Im)–AB Bonding Energies Evaluated with A Large Number of Density Functionals (P = porphine, Im = imidazole, AB = CO, NO, and O2)

PubMed Central

Liao, Meng-Sheng; Huang, Ming-Ju; Watts, John D.

2011-01-01

Sixty-four (64) density functionals, ranging from GGA, meta-GGA, hybrid GGA to hybrid meta-GGA, were tested to evaluate the FeP(Im)-AB bonding energies (Ebond) in the heme model complexes FeP(Im)(AB) (P = porphine, Im = imidazole, AB = CO, NO, and O2). The results indicate that an accurate prediction of Ebond for the various ligands to heme is difficult with the DFT methods; usually a functional successful for one system does not perform equally well for the other system(s). Relatively satisfactory results for the various FeP(Im)-AB bonding energies are obtained with the meta-GGA funtionals BLAP3 and Bmτ1; they yield Ebond values of ca.1.1, 1.2, and 0.4 eV for AB = CO, NO, and O2, respectively, which are in reasonable agreement with experimental data (0.78 – 0.85 eV for CO, 0.99 eV for NO, and 0.44 – 0.53 eV for O2). The other functionals show more or less deficiency for one or two of the systems. The performances of the various functionals in describing the spin-state energetics of the five-coordinate FeP(Im) complex were also examined. PMID:22228914

Multiple time step integrators in ab initio molecular dynamics.

PubMed

Luehr, Nathan; Markland, Thomas E; Martínez, Todd J

2014-02-28

Multiple time-scale algorithms exploit the natural separation of time-scales in chemical systems to greatly accelerate the efficiency of molecular dynamics simulations. Although the utility of these methods in systems where the interactions are described by empirical potentials is now well established, their application to ab initio molecular dynamics calculations has been limited by difficulties associated with splitting the ab initio potential into fast and slowly varying components. Here we present two schemes that enable efficient time-scale separation in ab initio calculations: one based on fragment decomposition and the other on range separation of the Coulomb operator in the electronic Hamiltonian. We demonstrate for both water clusters and a solvated hydroxide ion that multiple time-scale molecular dynamics allows for outer time steps of 2.5 fs, which are as large as those obtained when such schemes are applied to empirical potentials, while still allowing for bonds to be broken and reformed throughout the dynamics. This permits computational speedups of up to 4.4x, compared to standard Born-Oppenheimer ab initio molecular dynamics with a 0.5 fs time step, while maintaining the same energy conservation and accuracy.

Ab Initio Optimized Effective Potentials for Real Molecules in Optical Cavities: Photon Contributions to the Molecular Ground State

PubMed Central

2018-01-01

We introduce a simple scheme to efficiently compute photon exchange-correlation contributions due to the coupling to transversal photons as formulated in the newly developed quantum-electrodynamical density-functional theory (QEDFT).1−5 Our construction employs the optimized-effective potential (OEP) approach by means of the Sternheimer equation to avoid the explicit calculation of unoccupied states. We demonstrate the efficiency of the scheme by applying it to an exactly solvable GaAs quantum ring model system, a single azulene molecule, and chains of sodium dimers, all located in optical cavities and described in full real space. While the first example is a two-dimensional system and allows to benchmark the employed approximations, the latter two examples demonstrate that the correlated electron-photon interaction appreciably distorts the ground-state electronic structure of a real molecule. By using this scheme, we not only construct typical electronic observables, such as the electronic ground-state density, but also illustrate how photon observables, such as the photon number, and mixed electron-photon observables, for example, electron–photon correlation functions, become accessible in a density-functional theory (DFT) framework. This work constitutes the first three-dimensional ab initio calculation within the new QEDFT formalism and thus opens up a new computational route for the ab initio study of correlated electron–photon systems in quantum cavities. PMID:29594185

Revisiting the Electronic Structure of FeS Monomers Using ab Initio Ligand Field Theory and the Angular Overlap Model.

PubMed

Chilkuri, Vijay Gopal; DeBeer, Serena; Neese, Frank

2017-09-05

Iron-sulfur (FeS) proteins are universally found in nature with actives sites ranging in complexity from simple monomers to multinuclear sites from two up to eight iron atoms. These sites include mononuclear (rubredoxins), dinuclear (ferredoxins and Rieske proteins), trinuclear (e.g., hydrogenases), and tetranuclear (various ferredoxins and high-potential iron-sulfur proteins). The electronic structure of the higher-nuclearity clusters is inherently extremely complex. Hence, it is reasonable to take a bottom-up approach in which clusters of increasing nuclearity are analyzed in terms of the properties of their lower nuclearity constituents. In the present study, the first step is taken by an in-depth analysis of mononuclear FeS systems. Two different FeS molecules with phenylthiolate and methylthiolate as ligands are studied in their oxidized and reduced forms using modern wave function-based ab initio methods. The ab initio electronic spectra and wave function are presented and analyzed in detail. The very intricate electronic structure-geometry relationship in these systems is analyzed using ab initio ligand field theory (AILFT) in conjunction with the angular overlap model (AOM) parametrization scheme. The simple AOM model is used to explain the effect of geometric variations on the electronic structure. Through a comparison of the ab initio computed UV-vis absorption spectra and the available experimental spectra, the low-energy part of the many-particle spectrum is carefully analyzed. We show ab initio calculated magnetic circular dichroism spectra and present a comparison with the experimental spectrum. Finally, AILFT parameters and the ab initio spectra are compared with those obtained experimentally to understand the effect of the increased covalency of the thiolate ligands on the electronic structure of FeS monomers.

SatR Is a Repressor of Fluoroquinolone Efflux Pump SatAB

PubMed Central

Escudero, Jose Antonio; San Millan, Alvaro; Montero, Natalia; Gutierrez, Belen; Ovejero, Cristina Martinez; Carrilero, Laura

2013-01-01

Streptococcus suis is an emerging zoonotic agent responsible for high-mortality outbreaks among the human population in China. In this species, the ABC transporter SatAB mediates fluoroquinolone resistance when overexpressed. Here, we describe and characterize satR, an open reading frame (ORF) encoding a MarR superfamily regulator that acts as a repressor of satAB. satR is cotranscribed with satAB, and its interruption entails the overexpression of the pump, leading to a clinically relevant increase in resistance to fluoroquinolones. PMID:23650171

Process for treating ab5 nickel-metal hydride battery scrap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyman, J.W.; Palmer, G.R.

1994-12-31

A process for treating an AB5 Ni-MH battery to recover purified positive and negative electrode components of the battery is disclosed. An AB5 Ni-MH battery is placed in a mineral acid leach solution to cause the positive and negative electrode components of the battery to separate.

Compatibilization of HIPS/ABS blends from WEEE by using Styrene-Butadiene Rubber (SBR).

PubMed

Vazquez, Yamila V; Barbosa, Silvia E

2018-07-01

The aim of this work is to develop compatibilization strategies for High Impact Polystyrene (HIPS)/ Acrylonitrile-Butadiene-Styrene (ABS) blends from WEEE in order to add value to these recycled plastics by improving their mechanical performance. Results from a screening study of HIPS/ABS blends compatibilization by the addition of Styrene-Butadiene Rubber (SBR) are presented. Two different weight proportion of HIPS/ABS physical blends were analyzed, 80/20 and 20/80, with three different concentration of SBR: 2, 10 and 20 wt%. Compatibilization efficiency was analyzed from an accurate thermal and mechanical analysis, by comparing each physical blend and corresponding compatibilized blends with SBR. Results were discussed relating glass transition changes with mechanical performance, both aspects were interpreted in terms of blend morphology. Phase and fillers dispersion and distribution as well as SBR amount and its interaction with each phase were accurate analyzed. Compatibilization of HIPS/ABS blends from WEEE with the addition of SBR is effective in blends with HIPS as main component. With the addition of 2 wt% of SBR, strength and toughness have notably increased respect to the corresponding physical blend, 244% and 186% respectively. From this screening study is possible to infer that SBR is a sustainable and efficient compatibilizer of HIPS rich blends allowing to obtain a final blend that can be used as a replacement material of separated resins from WEEE. Copyright © 2018 Elsevier Ltd. All rights reserved.

Student Measurements of STFA 10AB (Theta Tauri)

NASA Astrophysics Data System (ADS)

Gillette, Sean; Estrada, Chris; Estrada, Reed; Aguilera, Sophia; Chavez, Valerie; Givens, Jalynn; Lindorfer, Sarah; Michels, Kaylie; Mobley, Makenzie; Reder, Gabriel; Renteria, Kayla; Shattles, Jenna; Wilkin, Aiden; Woodbury, Maisy; Rhoades, Breauna; Rhoades, Mark

2017-04-01

Eighth grade students at Vanguard Preparatory School measured the double star STFA 10AB using a 22-inch Newtonian Alt/Az telescope and a Celestron Micro Guide eyepiece. Bellatrix was used as the calibration star. The calculated means of multiple observations of STFA 10AB resulted in a separation of 45.18,” a scale constant of 7.88 arcseconds per division, and position angle of 257.9°. These measurements were compared to the most recent values in the Washington Double Star Catalog.

Emergent properties of nuclei from ab initio coupled-cluster calculations

NASA Astrophysics Data System (ADS)

Hagen, G.; Hjorth-Jensen, M.; Jansen, G. R.; Papenbrock, T.

2016-06-01

Emergent properties such as nuclear saturation and deformation, and the effects on shell structure due to the proximity of the scattering continuum and particle decay channels are fascinating phenomena in atomic nuclei. In recent years, ab initio approaches to nuclei have taken the first steps towards tackling the computational challenge of describing these phenomena from Hamiltonians with microscopic degrees of freedom. This endeavor is now possible due to ideas from effective field theories, novel optimization strategies for nuclear interactions, ab initio methods exhibiting a soft scaling with mass number, and ever-increasing computational power. This paper reviews some of the recent accomplishments. We also present new results. The recently optimized chiral interaction NNLO{}{{sat}} is shown to provide an accurate description of both charge radii and binding energies in selected light- and medium-mass nuclei up to 56Ni. We derive an efficient scheme for including continuum effects in coupled-cluster computations of nuclei based on chiral nucleon-nucleon and three-nucleon forces, and present new results for unbound states in the neutron-rich isotopes of oxygen and calcium. The coupling to the continuum impacts the energies of the {J}π =1/{2}-,3/{2}-,7/{2}-,3/{2}+ states in {}{17,23,25}O, and—contrary to naive shell-model expectations—the level ordering of the {J}π =3/{2}+,5/{2}+,9/{2}+ states in {}{53,55,61}Ca. ).

(abstract) Studies on AB(sub 5) Metal Hydride Alloys with Sn Additives

NASA Technical Reports Server (NTRS)

Ratnakumar, B. V.; Surampudi, S.; Stefano, S. Di; Halpert, G.; Witham, C.; Fultz, B.

1994-01-01

The use of metal hydrides as negative electrodes in alkaline rechargeable cells is becoming increasingly popular, due to several advantages offered by the metal hydrides over conventional anode materials (such as Zn, Cd) in terms of specific energy environmental cycle life and compatibility. Besides, the similarities in the cell voltage pressure characteristics, and charge control methods of the Ni-MH cells to the commonly used Ni-Cd point to a projected take over of 25% of the Ni-Cd market for consumer electronics by the Ni-MH cells in the next couple of years. Two classes of metal hydrides alloys based on rare earth metals (AB(sub 5)) and titanium (AB(sub 2)) are being currently developed at various laboratories. AB(sub 2) alloys exhibit higher specific energy than the AB(sub 5) alloys but the state of the art commercial Ni-MH cells are predominately manufactured using AB(sub 5) alloys.

Effect of Cu Alloying on S Poisoning of Ni Surfaces and Nanoparticle Morphologies Using Ab-Initio Thermodynamics Calculations.

PubMed

Kim, Ji-Su; Kim, Byung-Kook; Kim, Yeong-Cheol

2015-10-01

We investigated the effect of Cu alloying on S poisoning of Ni surfaces and nanoparticle morphologies using ab-initio thermodynamics calculations. Based on the Cu segregation energy and the S adsorption energy, the surface energy and nanoparticle morphology of pure Ni, pure Cu, and NiCu alloys were evaluated as functions of the chemical potential of S and the surface orientations of (100), (110), and (111). The constructed nanoparticle morphology was varied as a function of chemical potential of S. We find that the Cu added to Ni for NiCu alloys is strongly segregated into the top surface, and increases the S tolerance of the NiCu nanoparticles.

Ab-interno scleral suture loop fixation with cow-hitch knot in posterior chamber intraocular lens decentration

PubMed Central

Can, Ertuğrul; Koçak, Nurullah; Yücel, Özlem Eşki; Gül, Adem; Öztürk, Hilal Eser; Sayın, Osman

2016-01-01

Aim of Study: To describe a simplified ab-interno cow-hitch suture fixation technique for repositioning decentered posterior chamber intraocular lens (PC IOL). Materials and Methods: Two cases are presented with the surgical correction of decentered and subluxated IOL. Ab-interno scleral suture fixation technique with hitch-cow knot in the eye was performed with a ciliary sulcus guide instrument and 1 year follow-up was completed. Results: Both of the patients had well centered lenses postoperatively. Corrected distant and near visual acuities of the patients were improved. There was no significant postoperative complication. In the follow-up period of 1 year, no evidence of suture erosion was found. Conclusions: Ab-interno scleral suture loop fixation with hitch-cow knot in the eye was effective in repositioning decentered or subluxated PC IOLs with excellent postoperative centered lenses and visual outcomes. PMID:27050346

The adnAB Locus, Encoding a Putative Helicase-Nuclease Activity, Is Essential in Streptomyces

PubMed Central

Zhang, Lingli; Nguyen, Hoang Chuong; Chipot, Ludovic; Piotrowski, Emilie; Bertrand, Claire

2014-01-01

Homologous recombination is a crucial mechanism that repairs a wide range of DNA lesions, including the most deleterious ones, double-strand breaks (DSBs). This multistep process is initiated by the resection of the broken DNA ends by a multisubunit helicase-nuclease complex exemplified by Escherichia coli RecBCD, Bacillus subtilis AddAB, and newly discovered Mycobacterium tuberculosis AdnAB. Here we show that in Streptomyces, neither recBCD nor addAB homologues could be detected. The only putative helicase-nuclease-encoding genes identified were homologous to M. tuberculosis adnAB genes. These genes are conserved as a single copy in all sequenced genomes of Streptomyces. The disruption of adnAB in Streptomyces ambofaciens and Streptomyces coelicolor could not be achieved unless an ectopic copy was provided, indicating that adnAB is essential for growth. Both adnA and adnB genes were shown to be inducible in response to DNA damage (mitomycin C) and to be independently transcribed. Introduction of S. ambofaciens adnAB genes in an E. coli recB mutant restored viability and resistance to UV light, suggesting that Streptomyces AdnAB could be a functional homologue of RecBCD and be involved in DNA damage resistance. PMID:24837284

AB 1725: A Comprehensive Analysis.

ERIC Educational Resources Information Center

California Community Colleges, Sacramento. Board of Governors.

A summary and analysis is provided of California Assembly Bill (AB) 1725, a reform bill that provides new direction and support for the state's community colleges. The analysis addresses each of the eight sections of the bill: (1) mission, highlighting reforms related to mission statements, transfer core curriculum, remedial limits, articulation…

Pseudosymmetric features of non-centrosymmetric AB type crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gazhulina, A.P., E-mail: asyagazhulina@yandex.ru; Marychev, M.O.

2016-07-15

This work is supplement to our previous investigation (Gazhulina and Marychev, 2015) [1]. We have considered pseudosymmetric features with respect to the operation of inversion (pseudoinversion) for 340 non-centrosymmetric AB type crystals. Analysis of the features of particular structure types allowed us to determine the positions of pseudoinversion centers, subdivide them into separate types, and classify the entire set of crystals studied with respect to the types of pseudoinversion centers and peculiarities of the behavior of the degree of pseudoinversion depending on the ratio of atomic numbers of A and B components. For each group of crystals, average values andmore » lower boundaries of the maximum pseudoinversion are determined and distribution with respect to the degree of pseudoinversion is constructed. - Graphical abstract: A group of 340 non-centrosymmetric AB type crystals have been considered for their pseudosymmetry features with respect to the operation of inversion. Positions of pseudoinversion centers, subdivision of them into separate types, classification of the entire set of crystals studied with respect to the types of pseudoinversion centers and peculiarities of the behavior of the degree of pseudoinversion are established and discussed. Display Omitted - Highlights: • We consider pseudoinversion of 340 non-centrosymmetric AB type crystals. • AB type crystals are divided into three groups with respect to pseudoinversion. • Positions and types of pseudoinversion centers are determined. • Lower boundaries of the maximum pseudoinversion are determined.« less

Biological effects of an aqueous extract of Salix alba on the survival of Escherichia coli AB1157 cultures submitted to the action of stannous chloride.

PubMed

Souza, Raphael S S; Almeida, Marcela C; Manoel, Cristiano V; Santos-Filho, Sebastião D; Fonseca, Adenilson S; Bernardo Filho, Mario

2009-01-01

Stannous chloride (SnC12) is used in nuclear medicine as a reducing agent to obtain technetium-99m-radiopharmaceuticals. It have been reported that natural products might reduce the genotoxic and cytotoxic effects related to SnC12. This work evaluated the biological effects of an aqueous extract of Salix alba on the survival of Escherichia coli (E. coli) AB1157 (wild type) cultures submitted to the action of SnC12. E. coli AB1157 cultures (exponential growth phase) were collected by centrifugation, washed and resuspended in 0.9% NaCl. Samples were incubated in water bath shaker with: (a) SnC12 (25 microg/ml), (b) Salix alba extract(11.6 mg/ml) and (c) SnC12 (25 microg/ml) + Salix alba extract (11.6 mg/ml). Incubation with 0.9% NaCl was also carried out (control). At 60 min intervals, aliquots were withdrawn, diluted, spread onto Petri dishes with solid LB medium and incubated overnight. The colonies formed were counted and the survival fractions calculated. The extract was not able to protect the E. coli cultures against the lesive action of SnC12. The extract also did not interfere with the survival of the cultures. It suggested that the substances present in the Salix alba aqueous extract did not interfere strongly with cellular metabolism and did not alter the survival fractions of E. coli AB 1157. It is speculated that this extract cannot interfere with the generation of free radicals, the possible main agent responsible for SnC12 lesive action.

Quantum superposition at the half-metre scale.

PubMed

Kovachy, T; Asenbaum, P; Overstreet, C; Donnelly, C A; Dickerson, S M; Sugarbaker, A; Hogan, J M; Kasevich, M A

2015-12-24

The quantum superposition principle allows massive particles to be delocalized over distant positions. Though quantum mechanics has proved adept at describing the microscopic world, quantum superposition runs counter to intuitive conceptions of reality and locality when extended to the macroscopic scale, as exemplified by the thought experiment of Schrödinger's cat. Matter-wave interferometers, which split and recombine wave packets in order to observe interference, provide a way to probe the superposition principle on macroscopic scales and explore the transition to classical physics. In such experiments, large wave-packet separation is impeded by the need for long interaction times and large momentum beam splitters, which cause susceptibility to dephasing and decoherence. Here we use light-pulse atom interferometry to realize quantum interference with wave packets separated by up to 54 centimetres on a timescale of 1 second. These results push quantum superposition into a new macroscopic regime, demonstrating that quantum superposition remains possible at the distances and timescales of everyday life. The sub-nanokelvin temperatures of the atoms and a compensation of transverse optical forces enable a large separation while maintaining an interference contrast of 28 per cent. In addition to testing the superposition principle in a new regime, large quantum superposition states are vital to exploring gravity with atom interferometers in greater detail. We anticipate that these states could be used to increase sensitivity in tests of the equivalence principle, measure the gravitational Aharonov-Bohm effect, and eventually detect gravitational waves and phase shifts associated with general relativity.

Cry1Ab-expressing rice did not influence expression of fecundity-related genes in the wolf spider Pardosa pseudoannulata.

PubMed

Wang, Juan; Peng, Yuan-De; He, Chao; Wei, Bao-Yang; Liang, Yun-Shan; Yang, Hui-Lin; Wang, Zhi; Stanley, David; Song, Qi-Sheng

2016-10-30

The impact of Bacillus thuringiensis (Bt) toxin proteins on non-target predatory arthropods is not well understood at the cellular and molecular levels. Here, we investigated the potential effects of Cry1Ab expressing rice on fecundity of the wolf spider, Pardosa pseudoannulata, and some of the underlying molecular mechanisms. The results indicated that brown planthoppers (BPHs) reared on Cry1Ab-expressing rice accumulated the Cry toxin and that reproductive parameters (pre-oviposition period, post-oviposition stage, number of eggs, and egg hatching rate) of the spiders that consumed BPHs reared on Bt rice were not different from those that consumed BPHs reared on the non-Bt control rice. The accumulated Cry1Ab did not influence several vitellin (Vt) parameters, including stored energy and amino acid composition, during one generation. We considered the possibility that the Cry toxins exert their influence on beneficial predators via more subtle effects detectable at the molecular level in terms of gene expression. This led us to transcriptome analysis to detect differentially expressed genes in the ovaries of spiders exposed to dietary Cry1Ab and their counterpart control spiders. Eight genes, associated with vitellogenesis, vitellogenin receptor activity, and vitellin membrane formation were not differentially expressed between ovaries from the treated and control spiders, confirmed by qPCR analysis. We infer that dietary Cry1Ab expressing rice does not influence fecundity, nor expression levels of Vt-associated genes in P. pseudoannulata. Copyright © 2016. Published by Elsevier B.V.

Subtilase cytotoxin-encoding subAB2 variants in verotoxin-producing Escherichia coli strains isolated from goats and sheep.

PubMed

Orden, José A; Domínguez-Bernal, Gustavo; de la Fuente, Ricardo; Carrión, Javier

2016-04-01

Subtilase cytotoxin (SubAB) is a cytotoxin which might contribute to the virulence of verotoxin-producing Escherichia coli (VTEC) strains in humans. Three variants of SubAB encoding genes have been described (subAB1, subAB2-1, and subAB2-2) and it has been suggested that the strains positive for two variants of subAB may be more pathogenic for humans. In this study, 188 subAB2-positive VTEC strains isolated from goats and sheep were investigated for the presence of the subAB2-1 and subAB2-2 variants by PCR. Eighty-one of the 132 (61.4%) caprine strains and 36 of the 56 (64.3%) ovine strains possessed the subAB2-1 variant and all ovine and caprine strains, except one, were positive for the subAB2-2 variant. The results of this study show for first time that the subAB2-1 and subAB2-2 variants are found in caprine subAB2-positive VTEC strains and confirm that both subAB2 variants are detected in ovine subAB2-positive VTEC strains. Since no significant difference in the presence of both subAB2 variants was found among strains belonging to serotypes associated with severe illness in humans and strains not belonging to these serotypes, the occurrence of two subAB2 variants seems not to be associated with a higher risk of severe disease in humans. Copyright © 2016 Elsevier Ltd. All rights reserved.

Cosmic microwave background polarimetry with ABS and ACT: Instrumental design, characterization, and analysis

NASA Astrophysics Data System (ADS)

Simon, Sara Michelle

The LCDM model of the universe is supported by an abundance of astronomical observations, but it does not confirm a period of inflation in the early universe or explain the nature of dark energy and dark matter. The polarization of the cosmic microwave background (CMB) may hold the key to addressing these profound questions. If a period of inflation occurred in the early universe, it could have left a detectable odd-parity pattern called B-modes in the polarization of the CMB on large angular scales. Additionally, the CMB can be used to probe the structure of the universe on small angular scales through lensing and the detection of galaxy clusters and their motions via the Sunyaev-Zel'dovich effect, which can improve our understanding of neutrinos, dark matter, and dark energy. The Atacama B-mode Search (ABS) instrument was a cryogenic crossed-Dragone telescope located at an elevation of 5190m in the Atacama Desert in Chile that observed from February 2012 until October 2014. ABS searched on degree-angular scales for inflationary B-modes in the CMB and pioneered the use of a rapidly-rotating half-wave plate (HWP), which modulates the polarization of incoming light to permit the measurement of celestial polarization on large angular scales that would otherwise be obscured by 1/f noise from the atmosphere. Located next to ABS in the Atacama is the Atacama Cosmology Telescope (ACT), which is an off-axis Gregorian telescope. Its large 6m primary mirror facilitates measurements of the CMB on small angular scales. HWPs are baselined for use with the upgraded polarization-sensitive camera for ACT, called Advanced ACTPol, to extend observations of the polarized CMB to larger angular scales while also retaining sensitivity to small angular scales. The B-mode signal is extremely faint, and measuring it poses an instrumental challenge that requires the development of new technologies and well-characterized instruments. I will discuss the use of novel instrumentation and

Multicapillary SDS-gel electrophoresis for the analysis of fluorescently labeled mAb preparations: a high throughput quality control process for the production of QuantiPlasma and PlasmaScan mAb libraries.

PubMed

Székely, Andrea; Szekrényes, Akos; Kerékgyártó, Márta; Balogh, Attila; Kádas, János; Lázár, József; Guttman, András; Kurucz, István; Takács, László

2014-08-01

Molecular heterogeneity of mAb preparations is the result of various co- and post-translational modifications and to contaminants related to the production process. Changes in molecular composition results in alterations of functional performance, therefore quality control and validation of therapeutic or diagnostic protein products is essential. A special case is the consistent production of mAb libraries (QuantiPlasma™ and PlasmaScan™) for proteome profiling, quality control of which represents a challenge because of high number of mAbs (>1000). Here, we devise a generally applicable multicapillary SDS-gel electrophoresis process for the analysis of fluorescently labeled mAb preparations for the high throughput quality control of mAbs of the QuantiPlasma™ and PlasmaScan™ libraries. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Equine Immunoglobulin and Equine Neutralizing F(ab')₂ Protect Mice from West Nile Virus Infection.

PubMed

Cui, Jiannan; Zhao, Yongkun; Wang, Hualei; Qiu, Boning; Cao, Zengguo; Li, Qian; Zhang, Yanbo; Yan, Feihu; Jin, Hongli; Wang, Tiecheng; Sun, Weiyang; Feng, Na; Gao, Yuwei; Sun, Jing; Wang, Yanqun; Perlman, Stanley; Zhao, Jincun; Yang, Songtao; Xia, Xianzhu

2016-12-18

West Nile virus (WNV) is prevalent in Africa, Europe, the Middle East, West Asia, and North America, and causes epidemic encephalitis. To date, no effective therapy for WNV infection has been developed; therefore, there is urgent need to find an efficient method to prevent WNV disease. In this study, we prepared and evaluated the protective efficacy of immune serum IgG and pepsin-digested F(ab')₂ fragments from horses immunized with the WNV virus-like particles (VLP) expressing the WNV M and E proteins. Immune equine F(ab')₂ fragments and immune horse sera efficiently neutralized WNV infection in tissue culture. The passive transfer of equine immune antibodies significantly accelerated the virus clearance in the spleens and brains of WNV infected mice, and reduced mortality. Thus, equine immunoglobulin or equine neutralizing F(ab')₂ passive immunotherapy is a potential strategy for the prophylactic or therapeutic treatment of patients infected with WNV.

Fluctuation effects in blends of A + B homopolymers with AB diblock copolymer

NASA Astrophysics Data System (ADS)

Spencer, Russell K. W.; Matsen, Mark W.

2018-05-01

Field-theoretic simulations (FTSs) are performed on ternary blends of A- and B-type homopolymers of polymerization Nh and symmetric AB diblock copolymers of polymerization Nc. Unlike previous studies, our FTSs are conducted in three-dimensional space, with the help of two new semi-grand canonical ensembles. Motivated by the first experiment to discover bicontinuous microemulsion (BμE) in the polyethylene-polyethylene propylene system, we consider molecules of high molecular weight with size ratios of α ≡ Nh/Nc = 0.1, 0.2, and 0.4. Our focus is on the A + B coexistence between the two homopolymer-rich phases in the low-copolymer region of the phase diagram. The Scott line, at which the A + B phases mix to form a disordered melt with increasing temperature (or decreasing χ), is accurately determined using finite-size scaling techniques. We also examine how the copolymer affects the interface between the A + B phases, reducing the interfacial tension toward zero. Although comparisons with self-consistent field theory (SCFT) illustrate that fluctuation effects are relatively small, fluctuations do nevertheless produce the observed BμE that is absent in the SCFT phase diagram. Furthermore, we find evidence of three-phase A + B + BμE coexistence, which may have been missed in the original as well as subsequent experiments.

Efficacy of genetically modified Bt toxins alone and in combinations against pink bollworm resistant to Cry1Ac and Cry2Ab

USDA-ARS?s Scientific Manuscript database

Evolution of resistance in pests threatens the long-term success of transgenic crops that produce insecticidal proteins from Bacillus thuringiensis (Bt). Previous work showed that genetically modified Bt toxins Cry1AbMod and Cry1AcMod effectively countered resistance to native Bt toxins Cry1Ab and ...

Applicability of Type A/B alcohol dependence in the general population.

PubMed

Tam, Tammy W; Mulia, Nina; Schmidt, Laura A

2014-05-01

This study examined the concurrent and predictive validity of Type A/B alcohol dependence in the general population-a typology developed in clinical populations to gauge severity of dependence. Data were drawn from Waves 1 and 2 of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). The sample included 1,172 alcohol-dependent drinkers at baseline who were reinterviewed three years later. Latent class analysis was used to derive Type A/B classification using variables replicating the original Type A/B typology. Predictive validity of the Type A/B classification was assessed by multivariable linear and logistic regressions. A two-class solution consistent with Babor's original Type A/B typology adequately fit the data. Type B alcoholics in the general population, compared to Type As, had higher alcohol severity and more co-occurring drug, mental, and physical health problems. In the absence of treatment services utilization, Type B drinkers had two times the odds of being alcohol dependent three years later. Among those who utilized alcohol treatment services, Type B membership was predictive of heavy drinking and drug dependence, but not alcohol dependence, three years later. Findings suggest that Type A/B classification is both generalizable to, and valid within, the US general population of alcohol dependent drinkers. Results highlight the value of treatment for mitigating the persistence of dependence among Type B alcoholics in the general population. Screening for markers of vulnerability to Type B dependence could be of clinical value for health care providers to determine appropriate intervention. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Ultrasonic atomization and subsequent desolvation for monoclonal antibody (mAb) to the glycoprotein (GP) IIIa receptor into drug eluting stent.

PubMed

Wang, G X; Luo, L L; Yin, T Y; Li, Y; Jiang, T; Ruan, C G; Guidoin, R; Chen, Y P; Guzman, R

2010-01-01

An eluting-stent system with mAb dispersed in the PLLA (poly (L-lactic acid)) was validated in vitro. Specifically designed spray equipment based on the principle of ultrasonic atomization was used to produce a thin continuous PLLA (poly (L-lactic acid)) polymer coating incorporating monoclonal antibody (mAb). This PLLA coating was observed in light microscopy (LM) and scanning electron microscopy (SEM). The concentration of the monoclonal antibody (mAb) to the platelet glycoprotein (GP) IIIa receptor and the eluting rate were then measured by a radioisotope technique with (125)I-labelled GP IIIa mAb. An in vitro perfusion circuit was designed to evaluate the release rates at different velocities (10 or 20 ml min(-1)). The PLLA coating was thin and transparent, uniformly distributed on the surface of the stent. Three factors influenced its thickness: PLLA concentration, duration and gas pressure. The concentration of mAb was influenced by the duration of absorption and the concentration of the mAb solution; the maximum was 1662.23 + or - 38.83 ng. The eluting rate was fast for the first 2 h, then decreased slowly and attained 80% after 2 weeks. This ultrasonic atomization spray equipment and technological process to prepare protein eluting-stents were proved to be effective and reliable.

Effects of molecular packing in organic crystals on singlet fission with ab initio many body perturbation theory

NASA Astrophysics Data System (ADS)

Haber, Jonah; Refaely-Abramson, Sivan; da Jornada, Felipe H.; Louie, Steven G.; Neaton, Jeffrey B.

Multi-exciton generation processes, in which multiple charge carriers are generated from a single photon, are mechanisms of significant interest for achieving efficiencies beyond the Shockley-Queisser limit of conventional p-n junction solar cells. One well-studied multiexciton process is singlet fission, whereby a singlet decays into two spin-correlated triplet excitons. Here, we use a newly developed computational approach to calculate singlet-fission coupling terms and rates with an ab initio Green's function formalism based on many-body perturbation theory (MBPT) within the GW approximation and the Bethe-Salpeter equation approach. We compare results for crystalline pentacene and TIPS-pentacene and explore the effect of molecular packing on the singlet fission mechanism. This work is supported by the Department of Energy.

Thyroglobulin (Tg) Testing Revisited: Tg Assays, TgAb Assays, and Correlation of Results With Clinical Outcomes.

PubMed

Netzel, Brian C; Grebe, Stefan K G; Carranza Leon, B Gisella; Castro, M Regina; Clark, Penelope M; Hoofnagle, Andrew N; Spencer, Carole A; Turcu, Adina F; Algeciras-Schimnich, Alicia

2015-08-01

Measurement of thyroglobulin (Tg) by mass spectrometry (Tg-MS) is emerging as a tool for accurate Tg quantification in patients with anti-Tg autoantibodies (TgAbs). The objective of the study was to perform analytical and clinical evaluations of two Tg-MS assays in comparison with immunometric Tg assays (Tg-IAs) and Tg RIAs (Tg-RIAs) in a cohort of thyroid cancer patients. A total of 589 samples from 495 patients, 243 TgAb-/252 TgAb+, were tested by Beckman, Roche, Siemens-Immulite, and Thermo-Brahms Tg and TgAb assays, two Tg-RIAs, and two Tg-MS assays. The frequency of TgAb+ was 58%, 41%, 27%, and 39% for Roche, Beckman, Siemens-Immulite, and Thermo-Brahms, respectively. In TgAb- samples, clinical sensitivities and specificities of 100% and 74%-100%, respectively, were observed across all assays. In TgAb+ samples, all Tg-IAs demonstrated assay-dependent Tg underestimation, ranging from 41% to 86%. In TgAb+ samples, the use of a common cutoff (0.5 ng/mL) for the Tg-MS, three Tg-IAs, and the USC-RIA improved the sensitivity for the Tg-MSs and Tg-RIAs when compared with the Tg-IAs. In up to 20% of TgAb+ cases, Tg-IAs failed to detect Tg that was detectable by Tg-MS. In Tg-RIAs false-high biases were observed in TgAb+ samples containing low Tg concentrations. Tg-IAs remain the method of choice for Tg quantitation in TgAb- patients. In TgAb+ patients with undetectable Tg by immunometric assay, the Tg-MS will detect Tg in up to 20% additional cases. The Tg-RIA will detect Tg in approximately 35% cases, but a significant proportion of these will be clinical false-positive results. The undetectable Tg-MS seen in approximately 40% of TgAb+ cases in patients with disease need further evaluation.

Ab interno trabecular bypass surgery with iStent for open angle glaucoma

PubMed Central

Le, Jimmy T; Bicket, Amanda K; Li, Tianjing

2018-01-01

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: The primary objective is to assess the comparative effectiveness and safety of ab interno trabecular bypass surgery with iStent or iStent inject for OAG in comparison to conventional medical, laser, or surgical treatment. A secondary objective is to examine the effectiveness and safety of iStent or iStent Inject surgery in people who have concomitant phacoemulsification. PMID:27526051

MicroRNA-20a/b regulates cholesterol efflux through post-transcriptional repression of ATP-binding cassette transporter A1.

PubMed

Liang, Bin; Wang, Xin; Song, Xiaosu; Bai, Rui; Yang, Huiyu; Yang, Zhiming; Xiao, Chuanshi; Bian, Yunfei

2017-09-01

ATP-binding cassette transporter A1 (ABCA1) plays a crucial role in reverse cholesterol transport and exhibits anti-atherosclerosis effects. Some microRNAs (miRs) regulate ABCA1 expression, and recent studies have shown that miR-20a/b might play a critical role in atherosclerotic diseases. Here, we attempted to clarify the potential contribution of miR-20a/b in post-transcriptional regulation of ABCA1, cholesterol efflux, and atherosclerosis. We performed bioinformatics analysis and found that miR-20a/b was highly conserved and directly bound to ABCA1 mRNA with low binding free energy. Luciferase-reporter assay also confirmed that miR-20a/b significantly reduced luciferase activity associated with the ABCA1 3' untranslated region reporter construct. Additionally, miR-20a/b decreased ABCA1 expression, which, in turn, decreased cholesterol efflux and increased cholesterol content in THP-1 and RAW 264.7 macrophage-derived foam cells. In contrast, miR-20a/b inhibitors increased ABCA1 expression and cholesterol efflux, decreased cholesterol content, and inhibited foam-cell formation. Consistent with our in vitro results, miR-20a/b-treated ApoE -/- mice showed decreased ABCA1expression in the liver and reductions of reverse cholesterol transport in vivo. Furthermore, miR-20a/b regulated the formation of nascent high-density lipoprotein and promoted atherosclerotic development, whereas miR-20a/b knockdown attenuated atherosclerotic formation. miR-20 is a new miRNA capable of targeting ABCA1 and regulating ABCA1 expression. Therefore, miR-20 inhibition constitutes a new strategy for ABCA1-based treatment of atherosclerosis. Copyright © 2017 Elsevier B.V. All rights reserved.

"implicate Order" and the Good Life: Applying David Bohm's Ontology in Human World

NASA Astrophysics Data System (ADS)

Ravn, Ib.

In an attempt to formulate a coherent view of quantum reality, the theoretical physicist David Bohm has proposed a new concept of order to supplement the mechanistic Cartesian order of traditional physics. The "implicate" order is a subtler and deeper order that emphasizes "unbroken wholeness in flowing movement," in contrast to the coarser and more superficial, "explicate" Cartesian order of distinct phenomena. This dissertation attempts to develop a meaning for the idea of implicate order in the world of human experience. First is offered an account of some evolutionary episodes in terms of implicate and explicate order which draws on compatible work in cosmology, embryogenesis, visual perception, brain memory, decision making and phenomenology. Two important characteristics of the implicate order are then identified: in an implicate order, the whole is enfolded (or represented) in its parts; and all parts render different perspectives of the whole. Using arguments from decision making, the study of "flow" in human consciousness, and a model of skill acquisition, it is suggested that these characteristics manifest themselves in the human world as the "unity experience" and the "diversity experience," respectively. The former is the experience that a given part of one's life reveals a larger wholeness or unity; the subject-object distinction is transcended and one becomes absorbed in the flow of whatever activity is pursued. The latter is a deep appreciation of the diversity of ways in which people may seek the unity experience. These experiences are proposed as general values: social and psychological conditions ought to be such that these experiences are enhanced in all people. A two-by-two matrix of the two experiences demonstrates the danger of pursuing one to the exclusion of the other. The experience of unity without diversity turns into absolutism, the insistence that one's chosen activities or beliefs are the only right ones. The experience of diversity

Neutron Reflection Study of Surface Adsorption of Fc, Fab, and the Whole mAb.

PubMed

Li, Zongyi; Li, Ruiheng; Smith, Charles; Pan, Fang; Campana, Mario; Webster, John R P; van der Walle, Christopher F; Uddin, Shahid; Bishop, Steve M; Narwal, Rojaramani; Warwicker, Jim; Lu, Jian Ren

2017-07-12

Characterizing the influence of fragment crystallization (Fc) and antigen-binding fragment (Fab) on monoclonal antibody (mAb) adsorption at the air/water interface is an important step to understanding liquid mAb drug product stability during manufacture, shipping, and storage. Here, neutron reflection is used to study the air/water adsorption of a mAb and its Fc and Fab fragments. By varying the isotopic contrast, the adsorbed amount, thickness, orientation, and immersion of the adsorbed layers could be determined unambiguously. While Fc adsorption reached saturation within the hour, its surface adsorbed amount showed little variation with bulk concentration. In contrast, Fab adsorption was slower and the adsorbed amount was concentration dependent. The much higher Fc adsorption, as compared to Fab, was linked to its lower surface charge. Time and concentration dependence of mAb adsorption was dominated by Fab behavior, although both Fab and Fc behaviors contributed to the amount of mAb adsorbed. Changing the pH from 5.5 to 8.8 did not much perturb the adsorbed amount of Fc, Fab, or mAb. However, a small decrease in adsorption was observed for the Fc over pH 8-8.8 and vice versa for the Fab and mAb, consistent with a dominant Fab behavior. As bulk concentration increased from 5 to 50 ppm, the thicknesses of the Fc layers were almost constant at 40 Å, while Fab and mAb layers increased from 45 to 50 Å. These results imply that the adsorbed mAb, Fc, and Fab all retained their globular structures and were oriented with their short axial lengths perpendicular to the interface.

Operator evolution for ab initio electric dipole transitions of 4He

DOE PAGES

Schuster, Micah D.; Quaglioni, Sofia; Johnson, Calvin W.; ...

2015-07-24

A goal of nuclear theory is to make quantitative predictions of low-energy nuclear observables starting from accurate microscopic internucleon forces. A major element of such an effort is applying unitary transformations to soften the nuclear Hamiltonian and hence accelerate the convergence of ab initio calculations as a function of the model space size. The consistent simultaneous transformation of external operators, however, has been overlooked in applications of the theory, particularly for nonscalar transitions. We study the evolution of the electric dipole operator in the framework of the similarity renormalization group method and apply the renormalized matrix elements to the calculationmore » of the 4He total photoabsorption cross section and electric dipole polarizability. All observables are calculated within the ab initio no-core shell model. Furthermore, we find that, although seemingly small, the effects of evolved operators on the photoabsorption cross section are comparable in magnitude to the correction produced by including the chiral three-nucleon force and cannot be neglected.« less

Effect of alloying on screw dislocation structure in Mo: atomistic modelling approach with ab-initio parametrization

NASA Astrophysics Data System (ADS)

Gornostyrev, Yu. N.

2005-03-01

The plastic deformation in bcc metals is realized by the motion of screw dislocations with a complex star-like non-planar core. In this case, the direct investigation of the solute effect by first principles electronic structure calculations is a challenging problem for which we follow a combined approach that includes atomistic dislocation modelling with ab-initio parametrization of interatomic interactions. The screw dislocation core structure in Mo alloys is described within the model of atomic row displacements along a dislocation line with the interatomic row potential estimated from total energy full-potential linear muffin-tin orbital (FLMTO) calculations with the generalized gradient approximation (GGA) for the exchange-correlation potential. We demonstrate (1) that the solute effect on the dislocation structure is different for ``hard'' and ``easy'' cores and (2) that the softener addition in a ``hard'' core gives rise to a structural transformation into a configuration with a lower energy through an intermediate state. The softener solute is shown to disturb locally the three-fold symmetry of the dislocation core and the dislocation structure tends to the split planar core.

PREFACE: The 9th Biennial Conference on Classical and Quantum Relativistic Dynamics of Particles and Fields

NASA Astrophysics Data System (ADS)

Horwitz, L. P.

2015-05-01

The most recent meeting took place at the University of Connecticut, Storrs, on June 9-13, 2014. This meeting forms the basis for the Proceedings that are recorded in this issue of the Journal of Physics: Conference Series. Along with the work of some of the founding members of the Association, we were fortunate to have lecturers from application areas that provided strong challenges for further developments in quantum field theory, cosmological problems, and in the dynamics of systems subject to accelerations and the effects of general relativity. Topics treated in this issue include studies of the dark matter problem, rotation curves, and, in particular, for the (relatively accessible) Milky Way galaxy, compact stellar objects, a composite particle model, and the properties of a conformally invariant theory with spontaneous symmetry breaking. The Stueckelberg theory is further investigated for its properties in producing bremsstrahlung and pair production and apparent superluminal effects, and, as mentioned above, the implications of low energy nuclear reactions for such off-shell theories. Other "proper time" theories are investigated as well, and a study of the clock synchronization problem is presented. A mathematical study of to quantum groupo associated with the Toda lattice and its implications for quantum field theory, as well as a phenomenological discussion of supernova mechanics as well as a semiclassical discussion of electron spin and the question of the compatibility of special relativity and the quantum theory. A careful analysis of the covariant Aharonov-Bohm effect is given as well. The quantization of massless fields and the relation to the Maxwell theory is also discussed. We wish to thank the participants who contributed very much through their lectures, personal discussions, and these papers, to the advancement of the subject and our understanding.

Accessory proteins 8b and 8ab of severe acute respiratory syndrome coronavirus suppress the interferon signaling pathway by mediating ubiquitin-dependent rapid degradation of interferon regulatory factor 3.

PubMed

Wong, Hui Hui; Fung, To Sing; Fang, Shouguo; Huang, Mei; Le, My Tra; Liu, Ding Xiang

2018-02-01

Severe acute respiratory syndrome coronavirus (SARS-CoV) is an inefficient inducer of interferon (IFN) response. It expresses various proteins that effectively circumvent IFN production at different levels via distinct mechanisms. Through the construction of recombinant IBV expressing proteins 8a, 8b and 8ab encoded by SARS-CoV ORF8, we demonstrate that expression of 8b and 8ab enables the corresponding recombinant viruses to partially overcome the inhibitory actions of IFN activation to achieve higher replication efficiencies in cells. We also found that proteins 8b and 8ab could physically interact with IRF3. Overexpression of 8b and 8ab resulted in the reduction of poly (I:C)-induced IRF3 dimerization and inhibition of the IFN-β signaling pathway. This counteracting effect was partially mediated by protein 8b/8ab-induced degradation of IRF3 in a ubiquitin-proteasome-dependent manner. Taken together, we propose that SARS-CoV may exploit the unique functions of proteins 8b and 8ab as novel mechanisms to overcome the effect of IFN response during virus infection. Copyright © 2017 Elsevier Inc. All rights reserved.

Emergent properties of nuclei from ab initio coupled-cluster calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagen, G.; Hjorth-Jensen, M.; Jansen, G. R.

Emergent properties such as nuclear saturation and deformation, and the effects on shell structure due to the proximity of the scattering continuum and particle decay channels are fascinating phenomena in atomic nuclei. In recent years, ab initio approaches to nuclei have taken the first steps towards tackling the computational challenge of describing these phenomena from Hamiltonians with microscopic degrees of freedom. Our endeavor is now possible due to ideas from effective field theories, novel optimization strategies for nuclear interactions, ab initio methods exhibiting a soft scaling with mass number, and ever-increasing computational power. We review some of the recent accomplishments. We also present new results. The recently optimized chiral interaction NNLOmore » $${}_{{\\rm{sat}}}$$ is shown to provide an accurate description of both charge radii and binding energies in selected light- and medium-mass nuclei up to 56Ni. We derive an efficient scheme for including continuum effects in coupled-cluster computations of nuclei based on chiral nucleon–nucleon and three-nucleon forces, and present new results for unbound states in the neutron-rich isotopes of oxygen and calcium. Finally, the coupling to the continuum impacts the energies of the $${J}^{\\pi }=1/{2}^{-},3/{2}^{-},7/{2}^{-},3/{2}^{+}$$ states in $${}^{\\mathrm{17,23,25}}$$O, and—contrary to naive shell-model expectations—the level ordering of the $${J}^{\\pi }=3/{2}^{+},5/{2}^{+},9/{2}^{+}$$ states in $${}^{\\mathrm{53,55,61}}$$Ca.« less

Emergent properties of nuclei from ab initio coupled-cluster calculations

DOE PAGES

Hagen, G.; Hjorth-Jensen, M.; Jansen, G. R.; ...

2016-05-17

Emergent properties such as nuclear saturation and deformation, and the effects on shell structure due to the proximity of the scattering continuum and particle decay channels are fascinating phenomena in atomic nuclei. In recent years, ab initio approaches to nuclei have taken the first steps towards tackling the computational challenge of describing these phenomena from Hamiltonians with microscopic degrees of freedom. Our endeavor is now possible due to ideas from effective field theories, novel optimization strategies for nuclear interactions, ab initio methods exhibiting a soft scaling with mass number, and ever-increasing computational power. We review some of the recent accomplishments. We also present new results. The recently optimized chiral interaction NNLOmore » $${}_{{\\rm{sat}}}$$ is shown to provide an accurate description of both charge radii and binding energies in selected light- and medium-mass nuclei up to 56Ni. We derive an efficient scheme for including continuum effects in coupled-cluster computations of nuclei based on chiral nucleon–nucleon and three-nucleon forces, and present new results for unbound states in the neutron-rich isotopes of oxygen and calcium. Finally, the coupling to the continuum impacts the energies of the $${J}^{\\pi }=1/{2}^{-},3/{2}^{-},7/{2}^{-},3/{2}^{+}$$ states in $${}^{\\mathrm{17,23,25}}$$O, and—contrary to naive shell-model expectations—the level ordering of the $${J}^{\\pi }=3/{2}^{+},5/{2}^{+},9/{2}^{+}$$ states in $${}^{\\mathrm{53,55,61}}$$Ca.« less

Biofilm formation ability of Salmonella enterica serovar Typhimurium acrAB mutants.

PubMed

Schlisselberg, Dov B; Kler, Edna; Kisluk, Guy; Shachar, Dina; Yaron, Sima

2015-10-01

Recent studies offer contradictory findings about the role of multidrug efflux pumps in bacterial biofilm development. Thus, the aim of this study was to investigate the involvement of the AcrAB efflux pump in biofilm formation by investigating the ability of AcrB and AcrAB null mutants of Salmonella enterica serovar Typhimurium to produce biofilms. Three models were used to compare the ability of S. Typhimurium wild-type and its mutants to form biofilms: formation of biofilm on polystyrene surfaces; production of biofilm (mat model) on the air/liquid interface; and expression of curli and cellulose on Congo red-supplemented agar plates. All three investigated genotypes formed biofilms with similar characteristics. However, upon exposure to chloramphenicol, formation of biofilms on solid surfaces as well as the production of curli were either reduced or were delayed more significantly in both mutants, whilst there was no visible effect on pellicle formation. It can be concluded that when no selective pressure is applied, S. Typhimurium is able to produce biofilms even when the AcrAB efflux pumps are inactivated, implying that the use of efflux pump inhibitors to prevent biofilm formation is not a general solution and that combined treatments might be more efficient. Other factors that affect the ability to produce biofilms depending on efflux pump activity are yet to be identified. Copyright © 2015 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.

An operational multispectral scanner for bathymetric surveys - The ABS NORDA scanner

NASA Technical Reports Server (NTRS)

Haimbach, Stephen P.; Joy, Richard T.; Hickman, G. Daniel

1987-01-01

The Naval Ocean Research and Development Activity (NORDA) is developing the Airborne Bathymetric Survey (ABS) system, which will take shallow water depth soundings from a Navy P-3 aircraft. The system combines active and passive sensors to obtain optical measurements of water depth. The ABS NORDA Scanner is the systems passive multispectral scanner whose design goal is to provide 100 percent coverage of the seafloor, to depths of 20 m in average coastal waters. The ABS NORDA Scanner hardware and operational environment is discussed in detail. The optical model providing the basis for depth extraction is reviewed and the proposed data processing routine discussed.

Anti-inflammatory potential of ellagic acid, gallic acid and punicalagin A&B isolated from Punica granatum.

PubMed

BenSaad, Lamees A; Kim, Kah Hwi; Quah, Chin Chew; Kim, Wee Ric; Shahimi, Mustafa

2017-01-14

Punica granatum (pomegranate), an edible fruit originating in the Middle East, has been used as a traditional medicine for treatment of pain and inflammatory conditions such as peptic ulcer. The numerous risks associated with nonsteroidal anti-inflammatory drugs (NSAIDs) for treatment of pain and inflammation give rise to using medicinal herbs as alternative therapies. This study aimed to evaluate the anti-inflammatory effect of isolated compounds from the ethyl acetate (EtOAc) fraction of P. granatum by determination of their inhibitory effects on lipopolysaccharide (LPS), stimulated nitric oxide (NO), prostaglandin E2 (PGE-2), interleukin-6 (IL-6) and cyclooxxgenase-2 (COX-2) release from RAW264.7 cells. The compounds ellagic acid, gallic acid and punicalagin A&B were isolated from EtOAc by high performance liquid chromatography (HPLC) and further identified by mass spectrometry (MS). The inhibitory effect of ellagic acid, gallic acid and punicalagin A&B were evaluated on the production of LPS-induced NO by Griess reagent, PGE-2 and IL-6 by immunoassay kit and prostaglandin E2 competitive ELISA kit, and COX-2 by Western blotting. Ellagic acid, gallic acid and punicalagin A&B potentially inhibited LPS-induced NO, PGE-2 and IL-6 production. The results indicate that ellagic acid, gallic acid and punicalagin may be the compounds responsible for the anti-inflammatory potential of P. granatum.

Radiolabeled F(ab')2-cetuximab for theranostic purposes in colorectal and skin tumor-bearing mice models.

PubMed

Bellaye, P-S; Moreau, M; Raguin, O; Oudot, A; Bernhard, C; Vrigneaud, J-M; Dumont, L; Vandroux, D; Denat, F; Cochet, A; Brunotte, F; Collin, B

2018-05-17

This study aimed to investigate theranostic strategies in colorectal and skin cancer based on fragments of cetuximab, an anti-EGFR mAb, labeled with radionuclide with imaging and therapeutic properties, 111 In and 177 Lu, respectively. We designed F(ab') 2 -fragments of cetuximab radiolabeled with 111 In and 177 Lu. 111 In-F(ab') 2 -cetuximab tumor targeting and biodistribution were evaluated by SPECT in BalbC nude mice bearing primary colorectal tumors. The efficacy of 111 In-F(ab') 2 -cetuximab to assess therapy efficacy was performed on BalbC nude mice bearing colorectal tumors receiving 17-DMAG, an HSP90 inhibitor. Therapeutic efficacy of the radioimmunotherapy based on 177 Lu-F(ab') 2 -cetuximab was evaluated in SWISS nude mice bearing A431 tumors. Radiolabeling procedure did not change F(ab') 2 -cetuximab and cetuximab immunoreactivity nor affinity for HER1 in vitro. 111 In-DOTAGA-F(ab') 2 -cetuximab exhibited a peak tumor uptake at 24 h post-injection and showed a high tumor specificity determined by a significant decrease in tumor uptake after the addition of an excess of unlabeled-DOTAGA-F(ab') 2 -cetuximab. SPECT imaging of 111 In-DOTAGA-F(ab') 2 -cetuximab allowed an accurate evaluation of tumor growth and successfully predicted the decrease in tumor growth induced by 17-DMAG. Finally, 177 Lu-DOTAGA-F(ab') 2 -cetuximab radioimmunotherapy showed a significant reduction of tumor growth at 4 and 8 MBq doses. 111 In-DOTAGA-F(ab') 2 -cetuximab is a reliable and stable tool for specific in vivo tumor targeting and is suitable for therapy efficacy assessment. 177 Lu-DOTAGA-F(ab') 2 -cetuximab is an interesting theranostic tool allowing therapy and imaging.

Family distribution of anti-F(ab')2 antibodies in relatives of patients with systemic lupus erythematosus.

PubMed Central

Silvestris, F; Searles, R P; Bankhurst, A D; Williams, R C

1985-01-01

Recently we reported an inverse relationship between the levels of anti-F(ab')2 antibodies and disease activity in systemic lupus erythematosus (SLE). The present study focused on anti-F(ab')2 antibodies in unaffected relatives of SLE patients. Sixty sera from first degree family members from 11 SLE families and 49 sera from 8 control families were studied. Percentage of SLE family members with anti-DNA antibodies (15%) was higher than than control family sera (8%, P less than 0.05). Anti-F(ab')2 antibodies were measured using ELISA assays. The SLE family sera had higher amounts of anti-F(ab')2 antibodies than the normal control family group (P = 0.0051). In an effort to determine if anti-F(ab')2 antibodies found in high titres in the sera of some SLE family members had specificity for the F(ab')2 fragment of anti-DNA antibodies of the SLE relative patients, DNA-anti-DNA inhibition experiments were performed using anti-F(ab')2 prepared from the relative in parallel with anti-F(ab')2 prepared from normal controls with equivalent high titres of serum anti-F(ab')2. Inhibition exhibited by anti-F(ab')2 of first degree relatives was higher than that obtained from control normal donors (P less than 0.02). Such differences in inhibition were not recorded using a control tetanus toxoid-anti-tetanus toxoid assay. In direct binding ELISA experiments, peroxidase-conjugated anti-F(ab')2 antibodies from the same first degree relative showed high relative specificity against purified anti-DNA antibodies of his SLE proband when compared to those obtained against different anti-DNA antibodies isolated from unrelated SLE patients (P less than 0.001). Such a substantial difference was not observed in parallel experiments using peroxidase conjugated anti-F(ab')2 antibodies from normal controls unrelated to SLE subjects. PMID:3874025

Identification and characterization of the BmCyclin L1-BmCDK11A/B complex in relation to cell cycle regulation.

PubMed

Liu, Tai-Hang; Wu, Yun-Fei; Dong, Xiao-Long; Pan, Cai-Xia; Du, Guo-Yu; Yang, Ji-Gui; Wang, Wei; Bao, Xi-Yan; Chen, Peng; Pan, Min-Hui; Lu, Cheng

2017-05-03

Cyclin proteins are the key regulatory and activity partner of cyclin-dependent kinases (CDKs), which play pivotal regulatory roles in cell cycle progression. In the present study, we identified a Cyclin L1 and 2 CDK11 2 CDK11 splice variants, CDK11A and CDK11B, from silkworm, Bombyx mori. We determined that both Cyclin L1 and CDK11A/B are nuclear proteins, and further investigations were conducted to elucidate their spatiofunctional features. Cyclin L1 forms a complex with CDK11A/B and were co-localized to the nucleus. Moreover, the dimerization of CDK11A and CDK11B and the effects of Cyclin L1 and CDK11A/B on cell cycle regulation were also investigated. Using overexpression or RNA interference experiments, we demonstrated that the abnormal expression of Cyclin L1 and CDK11A/B leads to cell cycle arrest and cell proliferation suppression. Together, these findings indicate that CDK11A/B interacts with Cyclin L1 to regulate the cell cycle.

FTIR analysis on aging characteristics of ABS/PC blend under UV-irradiation in air

NASA Astrophysics Data System (ADS)

Li, Jiarong; Chen, Fu; Yang, Long; Jiang, Long; Dan, Yi

2017-09-01

Fourier Transform Infrared Spectroscopy (FTIR) is adopted to study the aging characteristics of poly(acrylonitrile-butadiene-styrene)/polycarbonate (ABS/PC) blend under UV-irradiation in air by analyzing the variation of the three main absorbance at about 967 cm- 1, 1720 cm- 1 and 3420 cm- 1 associated with carbon-hydrogen bonds belonging to 1,4 butadiene, carbonyl and hydroxyl groups, respectively. Results indicate that, under UV-irradiation in air, the photo-oxidation of the blend is not a simple combination of the photo-oxidation of corresponding ABS and PC themselves and takes place predominantly at the ABS component. Due to the interaction between the two components and the Fries rearrangement taken place in the PC component during the UV-irradiation in air, the ABS/PC blends behave higher photo-stability than ABS has.

HicAB toxin-antitoxin complex from Escherichia coli: expression and crystallization.

PubMed

Yang, Jingsi; Xu, Bingshuang; Gao, Zengqiang; Zhou, Ke; Liu, Peng; Dong, Yuhui; Zhang, Jianjun; Liu, Quansheng

2017-09-01

Toxin-antitoxin (TA) systems are widespread in both bacteria and archaea, where they enable cells to adapt to environmental cues. TA systems play crucial roles in various cellular processes, such as programmed cell death, cell growth, persistence and virulence. Here, two distinct forms of the type II toxin-antitoxin complex HicAB were identified and characterized in Escherichia coli K-12, and both were successfully overexpressed and purified. The two proposed forms, HicAB L and HicAB S , differed in the presence or absence of a seven-amino-acid segment at the N-terminus in the antitoxin HicB. The short form HicAB S readily crystallized under the conditions 0.1 M Tris-HCl pH 8.0, 20%(w/v) PEG 6000, 0.2 M ammonium sulfate. The HicAB S crystal diffracted and data were collected to 2.5 Å resolution. The crystal belonged to space group I222 or I2 1 2 1 2 1 , with unit-cell parameters a = 67.04, b = 66.31, c = 120.78 Å. Matthews coefficient calculation suggested the presence of two molecules each of HicA and HicB S in the asymmetric unit, with a solvent content of 55.28% and a Matthews coefficient (V M ) of 2.75 Å 3  Da -1 .

The NISTmAb Reference Material 8671 lifecycle management and quality plan.

PubMed

Schiel, John E; Turner, Abigail

2018-03-01