Hadamard States for the Klein-Gordon Equation on Lorentzian Manifolds of Bounded Geometry

NASA Astrophysics Data System (ADS)

Gérard, Christian; Oulghazi, Omar; Wrochna, Michał

2017-06-01

We consider the Klein-Gordon equation on a class of Lorentzian manifolds with Cauchy surface of bounded geometry, which is shown to include examples such as exterior Kerr, Kerr-de Sitter spacetime and the maximal globally hyperbolic extension of the Kerr outer region. In this setup, we give an approximate diagonalization and a microlocal decomposition of the Cauchy evolution using a time-dependent version of the pseudodifferential calculus on Riemannian manifolds of bounded geometry. We apply this result to construct all pure regular Hadamard states (and associated Feynman inverses), where regular refers to the state's two-point function having Cauchy data given by pseudodifferential operators. This allows us to conclude that there is a one-parameter family of elliptic pseudodifferential operators that encodes both the choice of (pure, regular) Hadamard state and the underlying spacetime metric.

Time- and angle-resolved photoemission spectroscopy of hydrated electrons near a liquid water surface.

PubMed

Yamamoto, Yo-ichi; Suzuki, Yoshi-Ichi; Tomasello, Gaia; Horio, Takuya; Karashima, Shutaro; Mitríc, Roland; Suzuki, Toshinori

2014-05-09

We present time- and angle-resolved photoemission spectroscopy of trapped electrons near liquid surfaces. Photoemission from the ground state of a hydrated electron at 260 nm is found to be isotropic, while anisotropic photoemission is observed for the excited states of 1,4-diazabicyclo[2,2,2]octane and I- in aqueous solutions. Our results indicate that surface and subsurface species create hydrated electrons in the bulk side. No signature of a surface-bound electron has been observed.

Bimolecular reaction dynamics from photoelectron spectroscopy of negative ions

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

Bradforth, S.E.

1992-11-01

The transition state region of a neutral bimolecular reaction may be experimentally investigated by photoelectron spectroscopy of an appropriate negative ion. The photoelectron spectrum provides information on the spectroscopy and dynamics of the short lived transition state and may be used to develop model potential energy surfaces that are semi-quantitative in this important region. The principles of bound [yields] bound negative ion photoelectron spectroscopy are illustrated by way of an example: a full analysis of the photoelectron bands of CN[sup [minus

Free energy barrier for melittin reorientation from a membrane-bound state to a transmembrane state.

PubMed

Irudayam, Sheeba J; Pobandt, Tobias; Berkowitz, Max L

2013-10-31

An important step in a phospholipid membrane pore formation by melittin antimicrobial peptide is a reorientation of the peptide from a surface into a transmembrane conformation. Experiments measure the fraction of peptides in the surface state and the transmembrane state, but no computational study exists that quantifies the free energy curve for the reorientation. In this work we perform umbrella sampling simulations to calculate the potential of mean force (PMF) for the reorientation of melittin from a surface-bound state to a transmembrane state and provide a molecular level insight in understanding the peptide-lipid properties that influence the existence of the free energy barrier. The PMFs were calculated for a peptide to lipid (P/L) ratio of 1/128 and 4/128. We observe that the free energy barrier is reduced when the P/L ratio increases. In addition, we study the cooperative effect; specifically we investigate if the reorientation barrier is smaller for a second melittin, given that another neighboring melittin was already in the transmembrane orientation. We observe that indeed the barrier of the PMF curve is reduced in this case, thus confirming the presence of a cooperative effect.

Odd-frequency superconductivity induced in topological insulators with and without hexagonal warping.

PubMed

Vasenko, A S; Golubov, A A; Silkin, V M; Chulkov, E V

2017-07-26

We study the effect of the Fermi surface anisotropy on the odd-frequency spin-triplet pairing component of the induced pair potential. We consider a superconductor/ ferromagnetic insulator (S/FI) hybrid structure formed on the 3D topological insulator (TI) surface. In this case three ingredients ensure the possibility of the odd-frequency pairing: (1) the topological surface states, (2) the induced pair potential, and (3) the magnetic moment of a nearby ferromagnetic insulator. We take into account the strong anisotropy of the Dirac point in topological insulators when the chemical potential lies well above the Dirac cone and its constant energy contour has a snowflake shape. Within this model, we propose that the S/FI boundary should be properly aligned with respect to the snowflake constant energy contour to have an odd-frequency symmetry of the corresponding pairing component and to insure the Majorana bound state at the S/FI boundary. For arbitrary orientation of the boundary, the Majorana bound state is absent. This provides a selection rule to the realization of Majorana modes in S/FI hybrid structures, formed on the topological insulator surface.

Local Conformational Stability of HIV-1 gp120 in Unliganded and CD4-Bound States as Defined by Amide Hydrogen/Deuterium Exchange▿ †

PubMed Central

Kong, Leopold; Huang, Chih-chin; Coales, Stephen J.; Molnar, Kathleen S.; Skinner, Jeff; Hamuro, Yoshitomo; Kwong, Peter D.

2010-01-01

The binding reaction of the HIV-1 gp120 envelope glycoprotein to the CD4 receptor involves exceptional changes in enthalpy and entropy. Crystal structures of gp120 in unliganded and various ligand-bound states, meanwhile, reveal an inner domain able to fold into diverse conformations, a structurally invariant outer domain, and, in the CD4-bound state, a bridging sheet minidomain. These studies, however, provide only hints as to the flexibility of each state. Here we use amide hydrogen/deuterium exchange coupled to mass spectrometry to provide quantifications of local conformational stability for HIV-1 gp120 in unliganded and CD4-bound states. On average, unliganded core gp120 displayed >10,000-fold slower exchange of backbone-amide hydrogens than a theoretically unstructured protein of the same composition, with binding by CD4 reducing the rate of gp120 amide exchange a further 10-fold. For the structurally constant CD4, alterations in exchange correlated well with alterations in binding surface (P value = 0.0004). For the structurally variable gp120, however, reductions in flexibility extended outside the binding surface, and regions of expected high structural diversity (inner domain/bridging sheet) displayed roughly 20-fold more rapid exchange in the unliganded state than regions of low diversity (outer domain). Thus, despite an extraordinary reduction in entropy, neither unliganded gp120 nor free CD4 was substantially unstructured, suggesting that most of the diverse conformations that make up the gp120 unliganded state are reasonably ordered. The results provide a framework for understanding how local conformational stability influences entropic change, conformational diversity, and structural rearrangements in the gp120-CD4 binding reaction. PMID:20660185

Influence of the lipid phase state and electrostatic surface potential on the conformations of a peripherally bound membrane protein.

PubMed

Decca, María B; Galassi, Vanesa V; Perduca, Massimiliano; Monaco, Hugo L; Montich, Guillermo G

2010-11-25

Avian liver bile acid-binding protein (L-BABP) binds peripherically to anionic lipid membranes. We previously showed that in the absence of added salt the binding to 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) occurs with changes in the secondary structure, the extent of which depends on the phase state of the lipid. In the present work, we used Fourier transform infrared spectroscopy to study the conformations of L-BABP bound to lipids with phosphoglycerol and phosphatidic acid polar head groups and with different transition temperatures in an aqueous medium with high ionic strength (0.1 M NaCl). When L-BABP was bound to the lipids with saturated acyl chains, DMPG, 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG), 1,2-dimyristoyl-sn-glycero-3-phosphate (DMPA), and 1,2-dilauroyl-sn-glycero-3-phosphate (DLPA), the conformation shifted from a native-like secondary structure to an unfolded state at the temperature of lipid chain melting. The protein was in the native-like conformation when it was bound to the unsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) in the liquid-crystalline phase. We also measured the electrokinetic surface potential of POPG and DMPG vesicles in the gel and in the liquid-crystalline phase and the protein binding constant to these lipid membranes. We found a correlation indicating that protein unfolding in the interface was due to the increase in the electrostatic surface potential that occurs in the lipid phase transition.

Saddle point localization of molecular wavefunctions.

PubMed

Mellau, Georg Ch; Kyuberis, Alexandra A; Polyansky, Oleg L; Zobov, Nikolai; Field, Robert W

2016-09-15

The quantum mechanical description of isomerization is based on bound eigenstates of the molecular potential energy surface. For the near-minimum regions there is a textbook-based relationship between the potential and eigenenergies. Here we show how the saddle point region that connects the two minima is encoded in the eigenstates of the model quartic potential and in the energy levels of the [H, C, N] potential energy surface. We model the spacing of the eigenenergies with the energy dependent classical oscillation frequency decreasing to zero at the saddle point. The eigenstates with the smallest spacing are localized at the saddle point. The analysis of the HCN ↔ HNC isomerization states shows that the eigenstates with small energy spacing relative to the effective (v1, v3, ℓ) bending potentials are highly localized in the bending coordinate at the transition state. These spectroscopically detectable states represent a chemical marker of the transition state in the eigenenergy spectrum. The method developed here provides a basis for modeling characteristic patterns in the eigenenergy spectrum of bound states.

Phase coherence and Andreev reflection in topological insulator devices

DOE PAGES

Finck, A. D. K.; Kurter, C.; Hor, Y. S.; ...

2014-11-04

Topological insulators (TIs) have attracted immense interest because they host helical surface states. Protected by time-reversal symmetry, they are robust to nonmagnetic disorder. When superconductivity is induced in these helical states, they are predicted to emulate p-wave pairing symmetry, with Majorana states bound to vortices. Majorana bound states possess non-Abelian exchange statistics that can be probed through interferometry. Here, we take a significant step towards Majorana interferometry by observing pronounced Fabry-Pérot oscillations in a TI sandwiched between a superconducting and a normal lead. For energies below the superconducting gap, we observe a doubling in the frequency of the oscillations, arisingmore » from an additional phase from Andreev reflection. When a magnetic field is applied perpendicular to the TI surface, a number of very sharp and gate-tunable conductance peaks appear at or near zero energy, which has consequences for interpreting spectroscopic probes of Majorana fermions. Our results show that TIs are a promising platform for exploring phase-coherent transport in a solid-state system.« less

A mechanistic study of the interaction of water-soluble borate glass with apatite-bound heterocyclic nitrogen-containing bisphosphonates.

PubMed

Pramanik, Chandrani; Sood, Parveen; Niu, Li-Na; Yuan, He; Ghoshal, Sushanta; Henderson, Walter; Liu, Yaodong; Jang, Seung Soon; Kumar, Satish; Pashley, David H; Tay, Franklin R

2016-02-01

Long-term oral and intravenous use of nitrogen-containing bisphosphonates (N-BPs) is associated with osteonecrosis of the jaw. Although N-BPs bind strongly to bone surfaces via non-covalent bonds, it is possible for extrinsic ions to dissociate bound N-BPs from mineralized bone by competitive desorption. Here, we investigate the effects and mechanism of using an ionic cocktail derived from borate bioactive glass for sequestration of heterocyclic N-BPs bound to apatite. By employing solid-state and solution-state analytical techniques, we confirmed that sequestration of N-BPs from bisphosphonate-bound apatite occurs in the presence of the borate-containing ionic cocktail. Simulations by density functional theory computations indicate that magnesium cation and borate anion are well within the extent of the risedronate or zoledronate anion to form precipitate complexes. The sequestration mechanism is due to the borate anion competing with bisphosphonates for similar electron-deficient sites on the apatite surface for binding. Thus, application of the borate-containing ionic cocktail represents a new topical lavage approach for removing apatite-bound heterocyclic N-BPs from exposed necrotic bone in bisphosphonate-related osteonecrosis of the jaw. Long-term oral consumption and injections of nitrogen-containing bisphosphonates (N-BPs) may result in death of the jaw bone when there is traumatic injury to the bone tissues. To date, there is no effective treatment for such a condition. This work reported the use of an ionic cocktail derived from water-soluble borate glass microfibers to displace the most potent type of N-BPs that are bound strongly to the mineral component on bone surfaces. The mechanism responsible for such an effect has been identified to be cation-mediated complexation of borate anions with negatively-charged N-BPs, allowing them to be released from the mineral surface. This borate-containing cocktail may be developed into a novel topical rinse for removing mineral-bound N-BPs from exposed dead bone. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Alternate binding modes for a ubiquitin-SH3 domain interaction studied by NMR spectroscopy.

PubMed

Korzhnev, Dmitry M; Bezsonova, Irina; Lee, Soyoung; Chalikian, Tigran V; Kay, Lewis E

2009-02-20

Surfaces of many binding domains are plastic, enabling them to interact with multiple targets. An understanding of how they bind and recognize their partners is therefore predicated on characterizing such dynamic interfaces. Yet, these interfaces are difficult to study by standard biophysical techniques that often 'freeze' out conformations or that produce data averaged over an ensemble of conformers. In this study, we used NMR spectroscopy to study the interaction between the C-terminal SH3 domain of CIN85 and ubiquitin that involves the 'classical' binding sites of these proteins. Notably, chemical shift titration data of one target with another and relaxation dispersion data that report on millisecond time scale exchange processes are both well fit to a simple binding model in which free protein is in equilibrium with a single bound conformation. However, dissociation constants and chemical shift differences between free and bound states measured from both classes of experiment are in disagreement. It is shown that the data can be reconciled by considering three-state binding models involving two distinct bound conformations. By combining titration and dispersion data, kinetic and thermodynamic parameters of the three-state binding reaction are obtained along with chemical shifts for each state. A picture emerges in which one bound conformer has increased entropy and enthalpy relative to the second and chemical shifts similar to that of the free state, suggesting a less packed interface. This study provides an example of the interplay between entropy and enthalpy to fine-tune molecular interactions involving the same binding surfaces.

Einstein-Podolsky-Rosen steering: Its geometric quantification and witness

NASA Astrophysics Data System (ADS)

Ku, Huan-Yu; Chen, Shin-Liang; Budroni, Costantino; Miranowicz, Adam; Chen, Yueh-Nan; Nori, Franco

2018-02-01

We propose a measure of quantum steerability, namely, a convex steering monotone, based on the trace distance between a given assemblage and its corresponding closest assemblage admitting a local-hidden-state (LHS) model. We provide methods to estimate such a quantity, via lower and upper bounds, based on semidefinite programming. One of these upper bounds has a clear geometrical interpretation as a linear function of rescaled Euclidean distances in the Bloch sphere between the normalized quantum states of (i) a given assemblage and (ii) an LHS assemblage. For a qubit-qubit quantum state, these ideas also allow us to visualize various steerability properties of the state in the Bloch sphere via the so-called LHS surface. In particular, some steerability properties can be obtained by comparing such an LHS surface with a corresponding quantum steering ellipsoid. Thus, we propose a witness of steerability corresponding to the difference of the volumes enclosed by these two surfaces. This witness (which reveals the steerability of a quantum state) enables one to find an optimal measurement basis, which can then be used to determine the proposed steering monotone (which describes the steerability of an assemblage) optimized over all mutually unbiased bases.

Comparisons of predicted steady-state levels in rooms with extended- and local-reaction bounding surfaces

NASA Astrophysics Data System (ADS)

Hodgson, Murray; Wareing, Andrew

2008-01-01

A combined beam-tracing and transfer-matrix model for predicting steady-state sound-pressure levels in rooms with multilayer bounding surfaces was used to compare the effect of extended- and local-reaction surfaces, and the accuracy of the local-reaction approximation. Three rooms—an office, a corridor and a workshop—with one or more multilayer test surfaces were considered. The test surfaces were a single-glass panel, a double-drywall panel, a carpeted floor, a suspended-acoustical ceiling, a double-steel panel, and glass fibre on a hard backing. Each test surface was modeled as of extended or of local reaction. Sound-pressure levels were predicted and compared to determine the significance of the surface-reaction assumption. The main conclusions were that the difference between modeling a room surface as of extended or of local reaction is not significant when the surface is a single plate or a single layer of material (solid or porous) with a hard backing. The difference is significant when the surface consists of multilayers of solid or porous material and includes a layer of fluid with a large thickness relative to the other layers. The results are partially explained by considering the surface-reflection coefficients at the first-reflection angles.

Bimolecular reaction dynamics from photoelectron spectroscopy of negative ions

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

Bradforth, Stephen Edmund

1992-11-01

The transition state region of a neutral bimolecular reaction may be experimentally investigated by photoelectron spectroscopy of an appropriate negative ion. The photoelectron spectrum provides information on the spectroscopy and dynamics of the short lived transition state and may be used to develop model potential energy surfaces that are semi-quantitative in this important region. The principles of bound {yields} bound negative ion photoelectron spectroscopy are illustrated by way of an example: a full analysis of the photoelectron bands of CN -, NCO - and NCS -. Transition state photoelectron spectra are presented for the following systems Br + HI, Clmore » + HI, F + HI, F + CH 30H,F + C 2H 5OH,F + OH and F + H 2. A time dependent framework for the simulation and interpretation of the bound → free transition state photoelectron spectra is subsequently developed and applied to the hydrogen transfer reactions Br + HI, F + OH → O( 3P, 1D) + HF and F + H 2. The theoretical approach for the simulations is a fully quantum-mechanical wave packet propagation on a collinear model reaction potential surface. The connection between the wavepacket time evolution and the photoelectron spectrum is given by the time autocorrelation function. For the benchmark F + H 2 system, comparisons with three-dimensional quantum calculations are made.« less

All the nonadiabatic (J=0) bound states of NO{sub 2}

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

Salzgeber, R.F.; Mandelshtam, V.A.; Schlier, C.

1999-02-01

We calculated all 3170 A{sub 1} and B{sub 2} (J=0) vibronic bound states of the coupled electronic ground ({tilde X}&hthinsp;{sup 2}A{sub 1}) and the first excited ({tilde A}&hthinsp;{sup 2}B{sub 2}) surfaces of NO{sub 2}, using a modification of the {ital ab initio} potentials of Leonardi {ital et al.} [J. Chem. Phys. {bold 105}, 9051 (1996)]. The calculation was performed by harmonic inversion of the Chebyshev correlation function generated from a DVR Hamiltonian in Radau coordinates. The rms error of the eigenenergies is about 2.5 cm{sup {minus}1}, corresponding to a relative error of 10{sup {minus}4} near the dissociation energy. The resultsmore » are compared with the adiabatic and diabatic levels calculated from the same surfaces, with experimental data, and with some approximations for the number of states function N(E). The experimental levels are reproduced fairly well up to an energy of 12&hthinsp;000 cm{sup {minus}1} above the potential minimum while the total number of bound levels agrees to within 2{percent} with that calculated from the phase space volume. {copyright} {ital 1999 American Institute of Physics.}« less

Classical calculation of the equilibrium constants for true bound dimers using complete potential energy surface.

PubMed

Buryak, Ilya; Vigasin, Andrey A

2015-12-21

The present paper aims at deriving classical expressions which permit calculation of the equilibrium constant for weakly interacting molecular pairs using a complete multidimensional potential energy surface. The latter is often available nowadays as a result of the more and more sophisticated and accurate ab initio calculations. The water dimer formation is considered as an example. It is shown that even in case of a rather strongly bound dimer the suggested expression permits obtaining quite reliable estimate for the equilibrium constant. The reliability of our obtained water dimer equilibrium constant is briefly discussed by comparison with the available data based on experimental observations, quantum calculations, and the use of RRHO approximation, provided the latter is restricted to formation of true bound states only.

Classical calculation of the equilibrium constants for true bound dimers using complete potential energy surface

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

Buryak, Ilya; Vigasin, Andrey A., E-mail: vigasin@ifaran.ru

The present paper aims at deriving classical expressions which permit calculation of the equilibrium constant for weakly interacting molecular pairs using a complete multidimensional potential energy surface. The latter is often available nowadays as a result of the more and more sophisticated and accurate ab initio calculations. The water dimer formation is considered as an example. It is shown that even in case of a rather strongly bound dimer the suggested expression permits obtaining quite reliable estimate for the equilibrium constant. The reliability of our obtained water dimer equilibrium constant is briefly discussed by comparison with the available data basedmore » on experimental observations, quantum calculations, and the use of RRHO approximation, provided the latter is restricted to formation of true bound states only.« less

Surface acoustic wave oxygen pressure sensor

NASA Technical Reports Server (NTRS)

Oglesby, Donald M. (Inventor); Upchurch, Billy T. (Inventor); Leighty, Bradley D. (Inventor)

1994-01-01

A transducer for the measurement of absolute gas-state oxygen pressure from pressures of less than 100 Pa to atmospheric pressure (1.01 x 10(exp 5) Pa) is based on a standard surface acoustic wave (SAW) device. The piezoelectric material of the SAW device is coated with a compound which will selectively and reversibly bind oxygen. When oxygen is bound by the coating, the mass of the coating increases by an amount equal to the mass of the bound oxygen. Such an increase in the mass of the coating causes a corresponding decrease in the resonant frequency of the SAW device.

Surface Andreev Bound States and Odd-Frequency Pairing in Topological Superconductor Junctions

NASA Astrophysics Data System (ADS)

Tanaka, Yukio; Tamura, Shun

2018-04-01

In this review, we summarize the achievement of the physics of surface Andreev bound states (SABS) up to now. The route of this activity has started from the physics of SABS of unconventional superconductors where the pair potential has a sign change on the Fermi surface. It has been established that SABS can be regarded as a topological edge state with topological invariant defined in the bulk Hamiltonian. On the other hand, SABS accompanies odd-frequency pairing like spin-triplet s-wave or spin-singlet p-wave. In a spin-triplet superconductor junction, induced odd-frequency pairing can penetrate into a diffusive normal metal (DN) attached to the superconductor. It causes so called anomalous proximity effect where the local density of states of quasiparticle in DN has a zero energy peak. When bulk pairing symmetry is spin-triplet px-wave, the anomalous proximity effect becomes prominent and the zero bias voltage conductance is always quantized independent of the resistance in DN and interface. Finally, we show that the present anomalous proximity effect is realized in an artificial topological superconducting system, where a nanowire with spin-orbit coupling and Zeeman field is put on the conventional spin-singlet s-wave superconductor.

The influence of surface state and saturation state on the dissolution kinetics of biogenic aragonite in seawater

USGS Publications Warehouse

Acker, James G.; Byrne, R.H.

1989-01-01

Uses several realistic partial molar volume changes (??V) for aragonite dissolution in seawater. Indicates that the molar volume change for aragonite dissolution is within the bounds -37 cm 3/mole ?????V ??? -39.5 cm3/mole. -from Authors

A first-principles study of methyl lactate adsorption on the chiral Cu (643) surface

NASA Astrophysics Data System (ADS)

Yuk, Simuck F.; Asthagiri, Aravind

2014-11-01

We used dispersion-corrected density function theory (DFT) to investigate the enantiospecific adsorption of R- and S-methyl lactate on the chiral Cu (643)R surface. Initial study of methyl lactate adsorbed on the Cu (111) surface revealed that the most strongly bound states are associated with interaction of the hydroxyl and alkoxide group with the surface. Using dispersion-corrected DFT-derived pre-factors and desorption energies within the Redhead analysis predicts peak temperatures that are in relatively good agreement with experimental values for molecular methyl lactate desorption from both the Cu (111) and Cu (643)R surface. The global minimum of S-methyl lactate is more firmly bound by 9.5 kJ/mol over its enantiomer on the Cu (643)R surface, with a peak temperature difference of 25 K versus an experimental value of 12 K.

A complex guided spectral transform Lanczos method for studying quantum resonance states

DOE PAGES

Yu, Hua-Gen

2014-12-28

A complex guided spectral transform Lanczos (cGSTL) algorithm is proposed to compute both bound and resonance states including energies, widths and wavefunctions. The algorithm comprises of two layers of complex-symmetric Lanczos iterations. A short inner layer iteration produces a set of complex formally orthogonal Lanczos (cFOL) polynomials. They are used to span the guided spectral transform function determined by a retarded Green operator. An outer layer iteration is then carried out with the transform function to compute the eigen-pairs of the system. The guided spectral transform function is designed to have the same wavefunctions as the eigenstates of the originalmore » Hamiltonian in the spectral range of interest. Therefore the energies and/or widths of bound or resonance states can be easily computed with their wavefunctions or by using a root-searching method from the guided spectral transform surface. The new cGSTL algorithm is applied to bound and resonance states of HO₂, and compared to previous calculations.« less

Interaction of the NO 3pπ (C {sup 2}Π) Rydberg state with RG (RG = Ne, Kr, and Xe): Potential energy surfaces and spectroscopy

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

Ershova, Olga V.; Besley, Nicholas A., E-mail: Nick.Besley@nottingham.ac.uk; Wright, Timothy G., E-mail: Tim.Wright@nottingham.ac.uk

2015-01-21

We present new potential energy surfaces for the interaction of NO(C {sup 2}Π) with each of Ne, Kr, and Xe. The potential energy surfaces have been calculated using second order Møller-Plesset perturbation theory, exploiting a procedure to converge the reference Hartree-Fock wavefunction for the excited states: the maximum overlap method. The bound rovibrational states obtained from the surfaces are used to simulate the electronic spectra and their appearance is in good agreement with available (2+1) REMPI spectra. We discuss the assignment and appearance of these spectra, comparing to that of NO-Ar.

Hadamard Property of the in and out States for Klein-Gordon Fields on Asymptotically Static Spacetimes

NASA Astrophysics Data System (ADS)

Gérard, Christian; Wrochna, Michał

2017-08-01

We consider the massive Klein-Gordon equation on a class of asymptotically static spacetimes (in the long range sense) with Cauchy surface of bounded geometry. We prove the existence and Hadamard property of the in and out states constructed by scattering theory methods.

Dynamics of solvation and desolvation of rubidium attached to He nanodroplets

NASA Astrophysics Data System (ADS)

von Vangerow, J.; John, O.; Stienkemeier, F.; Mudrich, M.

2015-07-01

The real-time dynamics of photoexcited and photoionized rubidium (Rb) atoms attached to helium (He) nanodroplets is studied by femtosecond pump-probe mass spectrometry. While excited Rb atoms in the perturbed 6p-state (Rb*) desorb off the He droplets, Rb+ photoions tend to sink into the droplet interior when created near the droplet surface. The transition from Rb+ solvation to full Rb* desorption is found to occur at a delay time τ ˜ 600 fs for Rb* in the 6pΣ-state and τ ˜ 1200 fs for the 6pΠ-state. Rb+He ions are found to be created by directly exciting bound Rb*He exciplex states as well as by populating bound Rb+He-states in a photoassociative ionization process.

Mechanistic Insight into Nanoparticle Surface Adsorption by Solution NMR Spectroscopy in an Aqueous Gel

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

Egner, Timothy K.; Naik, Pranjali; Nelson, Nicholas C.

Engineering nanoparticle (NP) functions at the molecular level requires a detailed understanding of the dynamic processes occurring at the NP surface. Herein we show that a combination of dark-state exchange saturation transfer (DEST) and relaxation dispersion (RD) NMR experiments on gel-stabilized NP samples enables the accurate determination of the kinetics and thermodynamics of adsorption. We used the former approach to describe the interaction of cholic acid (CA) and phenol (PhOH) with ceria NPs with a diameter of approximately 200 nm. Whereas CA formed weak interactions with the NPs, PhOH was tightly bound to the NP surface. Interestingly, we found thatmore » the adsorption of PhOH proceeds via an intermediate, weakly bound state in which the small molecule has residual degrees of rotational diffusion. Here we believe the use of aqueous gels for stabilizing NP samples will increase the applicability of solution NMR methods to the characterization of nanomaterials.« less

Mechanistic Insight into Nanoparticle Surface Adsorption by Solution NMR Spectroscopy in an Aqueous Gel

DOE PAGES

Egner, Timothy K.; Naik, Pranjali; Nelson, Nicholas C.; ...

2017-06-22

Engineering nanoparticle (NP) functions at the molecular level requires a detailed understanding of the dynamic processes occurring at the NP surface. Herein we show that a combination of dark-state exchange saturation transfer (DEST) and relaxation dispersion (RD) NMR experiments on gel-stabilized NP samples enables the accurate determination of the kinetics and thermodynamics of adsorption. We used the former approach to describe the interaction of cholic acid (CA) and phenol (PhOH) with ceria NPs with a diameter of approximately 200 nm. Whereas CA formed weak interactions with the NPs, PhOH was tightly bound to the NP surface. Interestingly, we found thatmore » the adsorption of PhOH proceeds via an intermediate, weakly bound state in which the small molecule has residual degrees of rotational diffusion. Here we believe the use of aqueous gels for stabilizing NP samples will increase the applicability of solution NMR methods to the characterization of nanomaterials.« less

Entropic and Electrostatic Effects on the Folding Free Energy of a Surface-Attached Biomolecule: An Experimental and Theoretical Study

PubMed Central

Watkins, Herschel M.; Vallée-Bélisle, Alexis; Ricci, Francesco; Makarov, Dmitrii E.; Plaxco, Kevin W.

2012-01-01

Surface-tethered biomolecules play key roles in many biological processes and biotechnologies. However, while the physical consequences of such surface attachment have seen significant theoretical study, to date this issue has seen relatively little experimental investigation. In response we present here a quantitative experimental and theoretical study of the extent to which attachment to a charged –but otherwise apparently inert– surface alters the folding free energy of a simple biomolecule. Specifically, we have measured the folding free energy of a DNA stem loop both in solution and when site-specifically attached to a negatively charged, hydroxyl-alkane-coated gold surface. We find that, whereas surface attachment is destabilizing at low ionic strength it becomes stabilizing at ionic strengths above ~130 mM. This behavior presumably reflects two competing mechanisms: excluded volume effects, which stabilize the folded conformation by reducing the entropy of the unfolded state, and electrostatics, which, at lower ionic strengths, destabilizes the more compact folded state via repulsion from the negatively charged surface. To test this hypothesis we have employed existing theories of the electrostatics of surface-bound polyelectrolytes and the entropy of surface-bound polymers to model both effects. Despite lacking any fitted parameters, these theoretical models quantitatively fit our experimental results, suggesting that, for this system, current knowledge of both surface electrostatics and excluded volume effects is reasonably complete and accurate. PMID:22239220

Engineering On-Surface Spin Crossover: Spin-State Switching in a Self-Assembled Film of Vacuum-Sublimable Functional Molecule.

PubMed

Kumar, Kuppusamy Senthil; Studniarek, Michał; Heinrich, Benoît; Arabski, Jacek; Schmerber, Guy; Bowen, Martin; Boukari, Samy; Beaurepaire, Eric; Dreiser, Jan; Ruben, Mario

2018-03-01

The realization of spin-crossover (SCO)-based applications requires study of the spin-state switching characteristics of SCO complex molecules within nanostructured environments, especially on surfaces. Except for a very few cases, the SCO of a surface-bound thin molecular film is either quenched or heavily altered due to: (i) molecule-surface interactions and (ii) differing intermolecular interactions in films relative to the bulk. By fabricating SCO complexes on a weakly interacting surface, the interfacial quenching problem is tackled. However, engineering intermolecular interactions in thin SCO active films is rather difficult. Here, a molecular self-assembly strategy is proposed to fabricate thin spin-switchable surface-bound films with programmable intermolecular interactions. Molecular engineering of the parent complex system [Fe(H 2 B(pz) 2 ) 2 (bpy)] (pz = pyrazole, bpy = 2,2'-bipyridine) with a dodecyl (C 12 ) alkyl chain yields a classical amphiphile-like functional and vacuum-sublimable charge-neutral Fe II complex, [Fe(H 2 B(pz) 2 ) 2 (C 12 -bpy)] (C 12 -bpy = dodecyl[2,2'-bipyridine]-5-carboxylate). Both the bulk powder and 10 nm thin films sublimed onto either quartz glass or SiO x surfaces of the complex show comparable spin-state switching characteristics mediated by similar lamellar bilayer like self-assembly/molecular interactions. This unprecedented observation augurs well for the development of SCO-based applications, especially in molecular spintronics. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Vibronic transitions in the alkali-metal (Li, Na, K, Rb) - alkaline-earth-metal (Ca, Sr) series: A systematic analysis of de-excitation mechanisms based on the graphical mapping of Frank-Condon integrals

NASA Astrophysics Data System (ADS)

Pototschnig, Johann V.; Meyer, Ralf; Hauser, Andreas W.; Ernst, Wolfgang E.

2017-02-01

Research on ultracold molecules has seen a growing interest recently in the context of high-resolution spectroscopy and quantum computation. After forming weakly bound molecules from atoms in cold collisions, the preparation of molecules in low vibrational levels of the ground state is experimentally challenging, and typically achieved by population transfer using excited electronic states. Accurate potential energy surfaces are needed for a correct description of processes such as the coherent de-excitation from the highest and therefore weakly bound vibrational levels in the electronic ground state via couplings to electronically excited states. This paper is dedicated to the vibrational analysis of potentially relevant electronically excited states in the alkali-metal (Li, Na, K, Rb)- alkaline-earth metal (Ca,Sr) diatomic series. Graphical maps of Frank-Condon overlap integrals are presented for all molecules of the group. By comparison to overlap graphics produced for idealized potential surfaces, we judge the usability of the selected states for future experiments on laser-enhanced molecular formation from mixtures of quantum degenerate gases.

Ab initio study on electronically excited states of lithium isocyanide, LiNC

NASA Astrophysics Data System (ADS)

Yasumatsu, Hisato; Jeung, Gwang-Hi

2014-01-01

The electronically excited states of the lithium isocyanide molecule, LiNC, were studied by means of ab initio calculations. The bonding nature of LiNC up to ∼10 eV is discussed on the basis of the potential energy surfaces according to the interaction between the ion-pair and covalent states. The ion-pair states are described by Coulomb attractive interaction in the long distance range, while the covalent ones are almost repulsive or bound with a very shallow potential dent. These two states interact each other to form adiabatic potential energy surfaces with non-monotonic change in the potential energy with the internuclear distance.

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.

Experimental studies on hybrid superconductor-topological insulator nanoribbon Josephson devices

NASA Astrophysics Data System (ADS)

Kayyalha, Morteza; Jauregui, Luis; Kazakov, Aleksander; Miotkowski, Ireneusz; Rokhinson, Leonid; Chen, Yong

The spin-helical topological surface states (TSS) of topological insulators in proximity with an s-wave superconductor are predicted to demonstrate signatures of topological superconductivity and host Majorana fermions. Here, we report on the observation of gate-tunable proximity-induced superconductivity in an intrinsic BiSbTeSe2 topological insulator nanoribbon (TINR) based Josephson junction (JJ) with Nb contacts. We observe a gate-tunable critical current (IC) with an anomalous behavior in the temperature (T) dependence of IC. We discuss various possible scenarios that could be relevant to this anomalous behavior, such as (i) the different temperature dependence of supercurrent generated by in-gap, where phase slip plays an important role, and out-of-gap Andreev bound states or (ii) the different critical temperatures associated with the top and bottom topological surface states. Our modeling of IC vs. T suggests the possible existence of one pair of in-gap Andreev bound states in our TINR. We have also studied the effects of magnetic fields on the critical current in our TINR Josephson junctions.

A bound on holographic entanglement entropy from inverse mean curvature flow

NASA Astrophysics Data System (ADS)

Fischetti, Sebastian; Wiseman, Toby

2017-06-01

Entanglement entropies are notoriously difficult to compute. Large-N strongly-coupled holographic CFTs are an important exception, where the AdS/CFT dictionary gives the entanglement entropy of a CFT region in terms of the area of an extremal bulk surface anchored to the AdS boundary. Using this prescription, we show—for quite general states of (2  +  1)-dimensional such CFTs—that the renormalized entanglement entropy of any region of the CFT is bounded from above by a weighted local energy density. The key ingredient in this construction is the inverse mean curvature (IMC) flow, which we suitably generalize to flows of surfaces anchored to the AdS boundary. Our bound can then be thought of as a ‘subregion’ Penrose inequality in asymptotically locally AdS spacetimes, similar to the Penrose inequalities obtained from IMC flows in asymptotically flat spacetimes. Combining the result with positivity of relative entropy, we argue that our bound is valid perturbatively in 1/N, and conjecture that a restricted version of it holds in any CFT.

Do the surface Fermi arcs in Weyl semimetals survive disorder?

NASA Astrophysics Data System (ADS)

Wilson, Justin H.; Pixley, J. H.; Huse, David A.; Refael, Gil; Das Sarma, S.

2018-06-01

We theoretically study the topological robustness of the surface physics induced by Weyl Fermi-arc surface states in the presence of short-ranged quenched disorder and surface-bulk hybridization. This is investigated with numerically exact calculations on a lattice model exhibiting Weyl Fermi arcs. We find that the Fermi-arc surface states, in addition to having a finite lifetime from disorder broadening, hybridize with nonperturbative bulk rare states making them no longer bound to the surface (i.e., they lose their purely surface spectral character). Thus, we provide strong numerical evidence that the Weyl Fermi arcs are not topologically protected from disorder. Nonetheless, the surface chiral velocity is robust and survives in the presence of strong disorder, persisting all the way to the Anderson-localized phase by forming localized current loops that live within the localization length of the surface. Thus, the Weyl semimetal is not topologically robust to the presence of disorder, but the surface chiral velocity is.

All the adiabatic bound states of NO{sub 2}

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

Salzgeber, R.F.; Mandelshtam, V.; Schlier, C.

1998-07-01

We calculated all 2967 even and odd bound states of the adiabatic ground state of NO{sub 2}, using a modification of the abthinspinitio potential energy surface of Leonardi {ital et al.} [J. Chem. Phys. {bold 105}, 9051 (1996)]. The calculation was performed by harmonic inversion of the Chebyshev correlation function generated by a DVR Hamiltonian in Radau coordinates. The relative error for the computed eigenenergies (measured from the potential minimum), is 10{sup {minus}4} or better, corresponding to an absolute error of less than about 2.5thinspcm{sup {minus}1}. Near the dissociation threshold the average density of states is about 0.2/cm{sup {minus}1} formore » each symmetry. Statistical analysis of the states shows some interesting structure of the rigidity parameter {Delta}{sub 3} as a function of energy. {copyright} {ital 1998 American Institute of Physics.}« less

Electron band bending of polar, semipolar and non-polar GaN surfaces

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

Bartoš, I.; Romanyuk, O., E-mail: romanyuk@fzu.cz; Houdkova, J.

2016-03-14

The magnitudes of the surface band bending have been determined by X-ray photoelectron spectroscopy for polar, semipolar, and non-polar surfaces of wurtzite GaN crystals. All surfaces have been prepared from crystalline GaN samples grown by the hydride-vapour phase epitaxy and separated from sapphire substrates. The Ga 3d core level peak shifts have been used for band bending determination. Small band bending magnitudes and also relatively small difference between the band bendings of the surfaces with opposite polarity have been found. These results point to the presence of electron surface states of different amounts and types on surfaces of different polaritymore » and confirm the important role of the electron surface states in compensation of the bound surface polarity charges in wurtzite GaN crystals.« less

The Molecular Basis of TnrA Control by Glutamine Synthetase in Bacillus subtilis*

PubMed Central

Hauf, Ksenia; Kayumov, Airat; Gloge, Felix; Forchhammer, Karl

2016-01-01

TnrA is a master regulator of nitrogen assimilation in Bacillus subtilis. This study focuses on the mechanism of how glutamine synthetase (GS) inhibits TnrA function in response to key metabolites ATP, AMP, glutamine, and glutamate. We suggest a model of two mutually exclusive GS conformations governing the interaction with TnrA. In the ATP-bound state (A-state), GS is catalytically active but unable to interact with TnrA. This conformation was stabilized by phosphorylated l-methionine sulfoximine (MSX), fixing the enzyme in the transition state. When occupied by glutamine (or its analogue MSX), GS resides in a conformation that has high affinity for TnrA (Q-state). The A- and Q-state are mutually exclusive, and in agreement, ATP and glutamine bind to GS in a competitive manner. At elevated concentrations of glutamine, ATP is no longer able to bind GS and to bring it into the A-state. AMP efficiently competes with ATP and prevents formation of the A-state, thereby favoring GS-TnrA interaction. Surface plasmon resonance analysis shows that TnrA bound to a positively regulated promoter fragment binds GS in the Q-state, whereas it rapidly dissociates from a negatively regulated promoter fragment. These data imply that GS controls TnrA activity at positively controlled promoters by shielding the transcription factor in the DNA-bound state. According to size exclusion and multiangle light scattering analysis, the dodecameric GS can bind three TnrA dimers. The highly interdependent ligand binding properties of GS reveal this enzyme as a sophisticated sensor of the nitrogen and energy state of the cell to control the activity of DNA-bound TnrA. PMID:26635369

Symmetry conditions of a nodal superconductor for generating robust flat-band Andreev bound states at its dirty surface

NASA Astrophysics Data System (ADS)

Ikegaya, Satoshi; Kobayashi, Shingo; Asano, Yasuhiro

2018-05-01

We discuss the symmetry property of a nodal superconductor that hosts robust flat-band zero-energy states at its surface under potential disorder. Such robust zero-energy states are known to induce the anomalous proximity effect in a dirty normal metal attached to a superconductor. A recent study has shown that a topological index NZES describes the number of zero-energy states at the dirty surface of a p -wave superconductor. We generalize the theory to clarify the conditions required for a superconductor that enables NZES≠0 . Our results show that NZES≠0 is realized in a topological material that belongs to either the BDI or CII class. We also present two realistic Hamiltonians that result in NZES≠0 .

Reproducing kernel potential energy surfaces in biomolecular simulations: Nitric oxide binding to myoglobin

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

Soloviov, Maksym; Meuwly, Markus, E-mail: m.meuwly@unibas.ch

2015-09-14

Multidimensional potential energy surfaces based on reproducing kernel-interpolation are employed to explore the energetics and dynamics of free and bound nitric oxide in myoglobin (Mb). Combining a force field description for the majority of degrees of freedom and the higher-accuracy representation for the NO ligand and the Fe out-of-plane motion allows for a simulation approach akin to a mixed quantum mechanics/molecular mechanics treatment. However, the kernel-representation can be evaluated at conventional force-field speed. With the explicit inclusion of the Fe-out-of-plane (Fe-oop) coordinate, the dynamics and structural equilibrium after photodissociation of the ligand are correctly described compared to experiment. Experimentally, themore » Fe-oop coordinate plays an important role for the ligand dynamics. This is also found here where the isomerization dynamics between the Fe–ON and Fe–NO state is significantly affected whether or not this co-ordinate is explicitly included. Although the Fe–ON conformation is metastable when considering only the bound {sup 2}A state, it may disappear once the {sup 4}A state is included. This explains the absence of the Fe–ON state in previous experimental investigations of MbNO.« less

Optically detecting the edge-state of a three-dimensional topological insulator under ambient conditions by ultrafast infrared photoluminescence spectroscopy

PubMed Central

Maezawa, Shun-ya; Watanabe, Hiroshi; Takeda, Masahiro; Kuroda, Kenta; Someya, Takashi; Matsuda, Iwao; Suemoto, Tohru

2015-01-01

Ultrafast infrared photoluminescence spectroscopy was applied to a three-dimensional topological insulator TlBiSe2 under ambient conditions. The dynamics of the luminescence exhibited bulk-insulating and gapless characteristics bounded by the bulk band gap energy. The existence of the topologically protected surface state and the picosecond-order relaxation time of the surface carriers, which was distinguishable from the bulk response, were observed. Our results provide a practical method applicable to topological insulators under ambient conditions for device applications. PMID:26552784

Finite-Size Effects on the Behavior of the Susceptibility in van der Waals Films Bounded by Strongly Absorbing Substrates

NASA Technical Reports Server (NTRS)

Dantchev, Daniel; Rudnick, Joseph; Barmatz, M.

2007-01-01

We study critical point finite-size effects in the case of the susceptibility of a film in which interactions are characterized by a van der Waals-type power law tail. The geometry is appropriate to a slab-like system with two bounding surfaces. Boundary conditions are consistent with surfaces that both prefer the same phase in the low temperature, or broken symmetry, state. We take into account both interactions within the system and interactions between the constituents of the system and the material surrounding it. Specific predictions are made with respect to the behavior of 3He and 4He films in the vicinity of their respective liquid-vapor critical points.

Lifetimes and wave functions of ozone metastable vibrational states near the dissociation limit in a full-symmetry approach

NASA Astrophysics Data System (ADS)

Lapierre, David; Alijah, Alexander; Kochanov, Roman; Kokoouline, Viatcheslav; Tyuterev, Vladimir

2016-10-01

Energies and lifetimes (widths) of vibrational states above the lowest dissociation limit of O163 were determined using a previously developed efficient approach, which combines hyperspherical coordinates and a complex absorbing potential. The calculations are based on a recently computed potential energy surface of ozone determined with a spectroscopic accuracy [Tyuterev et al., J. Chem. Phys. 139, 134307 (2013), 10.1063/1.4821638]. The effect of permutational symmetry on rovibrational dynamics and the density of resonance states in O3 is discussed in detail. Correspondence between quantum numbers appropriate for short- and long-range parts of wave functions of the rovibrational continuum is established. It is shown, by symmetry arguments, that the allowed purely vibrational (J =0 ) levels of O163 and O183, both made of bosons with zero nuclear spin, cannot dissociate on the ground-state potential energy surface. Energies and wave functions of bound states of the ozone isotopologue O163 with rotational angular momentum J =0 and 1 up to the dissociation threshold were also computed. For bound levels, good agreement with experimental energies is found: The rms deviation between observed and calculated vibrational energies is 1 cm-1. Rotational constants were determined and used for a simple identification of vibrational modes of calculated levels.

Surface-confined Ullmann coupling of thiophene substituted porphyrins

NASA Astrophysics Data System (ADS)

Beggan, J. P.; Boyle, N. M.; Pryce, M. T.; Cafolla, A. A.

2015-09-01

The covalent coupling of (5,10,15,20-tetrabromothien-2-ylporphyrinato)zinc(II) (TBrThP) molecules on the Ag(111) surface has been investigated under ultra-high-vacuum conditions, using scanning tunnelling microscopy and x-ray photoelectron spectroscopy. The findings provide atomic-level insight into surface-confined Ullmann coupling of thiophene substituted porphyrins, analyzing the progression of organometallic intermediate to final coupled state. Adsorption of the TBrThP molecules on the Ag(111) surface at room temperature is found to result in the reductive dehalogenation of the bromothienyl substituents and the subsequent formation of single strand and crosslinked coordination networks. The coordinated substrate atoms bridge the proximal thienyl groups of the organometallic intermediate, while the cleaved bromine atoms are bound on the adjacent Ag(111) surface. The intermediate complex displays a thermal lability at ˜423 K that results in the dissociation of the proximal thienyl groups with the concomitant loss of the surface bound bromine. At the thermally induced dissociation of the intermediate complex the resultant thienylporphyrin derivatives covalently couple, leading to the formation of a polymeric network of thiophene linked and meso-meso fused porphyrins.

What can Andreev bound states tell us about superconductors?

PubMed

Millo, Oded; Koren, Gad

2018-08-06

Zero-energy Andreev bound states, which manifest themselves in the tunnelling spectra as zero-bias conductance peaks (ZBCPs), are abundant at interfaces between superconductors and other materials and on the nodal surface of high-temperature superconductors. In this review, we focus on the information such excitations can provide on the properties of superconductor systems. First, a general introduction to the physics of Andreev bound states in superconductor/normal metal interfaces is given with a particular emphasis on why they appear at zero energy in d -wave superconductors. Then, specific spectroscopic tunnelling studies of thin films, bilayers and junctions are described, focusing on the corresponding ZBCP features. Scanning tunnelling spectroscopy (STS) studies show that the ZBCPs on the c -axis YBa 2 Cu 3 O 7- δ (YBCO) films are correlated with the surface morphology and appear only in proximity to (110) facets. STS on c -axis La 1.88 Sr 0.12 CuO 4 (LSCO) films exhibiting the 1/8 anomaly shows spatially modulated peaks near zero bias associated with the anti-phase ordering of the d -wave order parameter predicted at this doping level. ZBCPs were also found in micrometre-size edge junctions of YBCO/SrRuO 3 /YBCO, where SrRuO 3 is ferromagnetic. Here, the results are consistent with a crossed Andreev reflection effect (CARE) at the narrow domain walls of the SrRuO 3 ZBCPs measured in STS studies of manganite/cuprate bilayers could not be attributed to CARE because the manganite's domain wall is much larger than the coherence length in YBCO, and instead are attributed to proximity-induced triplet-pairing superconductivity with non-conventional symmetry. And finally, ZBCPs found in junctions of non-intentionally doped topological insulator films of Bi 2 Se 3 and the s -wave superconductor NbN are attributed to proximity-induced p x  + ip y triplet order parameter in the topological material.This article is part of the theme issue 'Andreev bound states'. © 2018 The Author(s).

Human γ-Glutamyl Transpeptidase 1: STRUCTURES OF THE FREE ENZYME, INHIBITOR-BOUND TETRAHEDRAL TRANSITION STATES, AND GLUTAMATE-BOUND ENZYME REVEAL NOVEL MOVEMENT WITHIN THE ACTIVE SITE DURING CATALYSIS.

PubMed

Terzyan, Simon S; Burgett, Anthony W G; Heroux, Annie; Smith, Clyde A; Mooers, Blaine H M; Hanigan, Marie H

2015-07-10

γ-Glutamyl transpeptidase 1 (GGT1) is a cell surface, N-terminal nucleophile hydrolase that cleaves glutathione and other γ-glutamyl compounds. GGT1 expression is essential in cysteine homeostasis, and its induction has been implicated in the pathology of asthma, reperfusion injury, and cancer. In this study, we report four new crystal structures of human GGT1 (hGGT1) that show conformational changes within the active site as the enzyme progresses from the free enzyme to inhibitor-bound tetrahedral transition states and finally to the glutamate-bound structure prior to the release of this final product of the reaction. The structure of the apoenzyme shows flexibility within the active site. The serine-borate-bound hGGT1 crystal structure demonstrates that serine-borate occupies the active site of the enzyme, resulting in an enzyme-inhibitor complex that replicates the enzyme's tetrahedral intermediate/transition state. The structure of GGsTop-bound hGGT1 reveals its interactions with the enzyme and why neutral phosphonate diesters are more potent inhibitors than monoanionic phosphonates. These structures are the first structures for any eukaryotic GGT that include a molecule in the active site covalently bound to the catalytic Thr-381. The glutamate-bound structure shows the conformation of the enzyme prior to release of the final product and reveals novel information regarding the displacement of the main chain atoms that form the oxyanion hole and movement of the lid loop region when the active site is occupied. These data provide new insights into the mechanism of hGGT1-catalyzed reactions and will be invaluable in the development of new classes of hGGT1 inhibitors for therapeutic use. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Human γ-glutamyl transpeptidase 1: Structures of the free enzyme, inhibitor-bound tetrahedral transition states, and glutamate-bound enzyme reveal novel movement within the active site during catalysis [Human gamma-glutamyl transpeptidase: Inhibitor binding and movement within the active site

DOE PAGES

Terzyan, Simon S.; Burgett, Anthony W. G.; Heroux, Annie; ...

2015-05-26

γ-Glutamyl transpeptidase 1 (GGT1) is a cell surface, N-terminal nucleophile hydrolase that cleaves glutathione and other γ-glutamyl compounds. GGT1 expression is essential in cysteine homeostasis, and its induction has been implicated in the pathology of asthma, reperfusion injury, and cancer. In this study, we report four new crystal structures of human GGT1 (hGGT1) that show conformational changes within the active site as the enzyme progresses from the free enzyme to inhibitor-bound tetrahedral transition states and finally to the glutamate-bound structure prior to the release of this final product of the reaction. The structure of the apoenzyme shows flexibility within themore » active site. The serine-borate-bound hGGT1 crystal structure demonstrates that serine-borate occupies the active site of the enzyme, resulting in an enzyme-inhibitor complex that replicates the enzyme's tetrahedral intermediate/transition state. The structure of GGsTop-bound hGGT1 reveals its interactions with the enzyme and why neutral phosphonate diesters are more potent inhibitors than monoanionic phosphonates. These structures are the first structures for any eukaryotic GGT that include a molecule in the active site covalently bound to the catalytic Thr-381. The glutamate-bound structure shows the conformation of the enzyme prior to release of the final product and reveals novel information regarding the displacement of the main chain atoms that form the oxyanion hole and movement of the lid loop region when the active site is occupied. Lastly,tThese data provide new insights into the mechanism of hGGT1-catalyzed reactions and will be invaluable in the development of new classes of hGGT1 inhibitors for therapeutic use.« less

Human γ-glutamyl transpeptidase 1: Structures of the free enzyme, inhibitor-bound tetrahedral transition states, and glutamate-bound enzyme reveal novel movement within the active site during catalysis [Human gamma-glutamyl transpeptidase: Inhibitor binding and movement within the active site

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

Terzyan, Simon S.; Burgett, Anthony W. G.; Heroux, Annie

γ-Glutamyl transpeptidase 1 (GGT1) is a cell surface, N-terminal nucleophile hydrolase that cleaves glutathione and other γ-glutamyl compounds. GGT1 expression is essential in cysteine homeostasis, and its induction has been implicated in the pathology of asthma, reperfusion injury, and cancer. In this study, we report four new crystal structures of human GGT1 (hGGT1) that show conformational changes within the active site as the enzyme progresses from the free enzyme to inhibitor-bound tetrahedral transition states and finally to the glutamate-bound structure prior to the release of this final product of the reaction. The structure of the apoenzyme shows flexibility within themore » active site. The serine-borate-bound hGGT1 crystal structure demonstrates that serine-borate occupies the active site of the enzyme, resulting in an enzyme-inhibitor complex that replicates the enzyme's tetrahedral intermediate/transition state. The structure of GGsTop-bound hGGT1 reveals its interactions with the enzyme and why neutral phosphonate diesters are more potent inhibitors than monoanionic phosphonates. These structures are the first structures for any eukaryotic GGT that include a molecule in the active site covalently bound to the catalytic Thr-381. The glutamate-bound structure shows the conformation of the enzyme prior to release of the final product and reveals novel information regarding the displacement of the main chain atoms that form the oxyanion hole and movement of the lid loop region when the active site is occupied. Lastly,tThese data provide new insights into the mechanism of hGGT1-catalyzed reactions and will be invaluable in the development of new classes of hGGT1 inhibitors for therapeutic use.« less

Surface structure of neutron stars with high magnetic fields

NASA Technical Reports Server (NTRS)

Fushiki, I.; Gudmundsson, E. H.; Pethick, C. J.

1989-01-01

The equation of state of cold dense matter in strong magnetic fields is calculated in the Thomas-Fermi and Thomas-Fermi-Dirac approximations. For use in the latter calculation, a new expression is derived for the exchange energy of the uniform electron gas in a strong magnetic field. Detailed calculations of the density profile in the surface region of a neutron star are described for a variety of equations of state, and these show that the surface density profile is strongly affected by the magnetic field, irrespective of whether or not matter in a magnetic field has a condensed state bound with respect to isolated atoms. It is also shown that, as a consequence of the field dependence of the screening potential, magnetic fields can significantly increase nuclear reaction rates.

Tension-dependent structural deformation alters single-molecule transition kinetics.

PubMed

Sudhanshu, B; Mihardja, S; Koslover, E F; Mehraeen, S; Bustamante, C; Spakowitz, A J

2011-02-01

We analyze the response of a single nucleosome to tension, which serves as a prototypical biophysical measurement where tension-dependent deformation alters transition kinetics. We develop a statistical-mechanics model of a nucleosome as a wormlike chain bound to a spool, incorporating fluctuations in the number of bases bound, the spool orientation, and the conformations of the unbound polymer segments. With the resulting free-energy surface, we perform dynamic simulations that permit a direct comparison with experiments. This simple approach demonstrates that the experimentally observed structural states at nonzero tension are a consequence of the tension and that these tension-induced states cease to exist at zero tension. The transitions between states exhibit substantial deformation of the unbound polymer segments. The associated deformation energy increases with tension; thus, the application of tension alters the kinetics due to tension-induced deformation of the transition states. This mechanism would arise in any system where the tether molecule is deformed in the transition state under the influence of tension.

Tension-dependent structural deformation alters single-molecule transition kinetics

PubMed Central

Sudhanshu, B.; Mihardja, S.; Koslover, E. F.; Mehraeen, S.; Bustamante, C.; Spakowitz, A. J.

2011-01-01

We analyze the response of a single nucleosome to tension, which serves as a prototypical biophysical measurement where tension-dependent deformation alters transition kinetics. We develop a statistical-mechanics model of a nucleosome as a wormlike chain bound to a spool, incorporating fluctuations in the number of bases bound, the spool orientation, and the conformations of the unbound polymer segments. With the resulting free-energy surface, we perform dynamic simulations that permit a direct comparison with experiments. This simple approach demonstrates that the experimentally observed structural states at nonzero tension are a consequence of the tension and that these tension-induced states cease to exist at zero tension. The transitions between states exhibit substantial deformation of the unbound polymer segments. The associated deformation energy increases with tension; thus, the application of tension alters the kinetics due to tension-induced deformation of the transition states. This mechanism would arise in any system where the tether molecule is deformed in the transition state under the influence of tension. PMID:21245354

Tracking control of a marine surface vessel with full-state constraints

NASA Astrophysics Data System (ADS)

Yin, Zhao; He, Wei; Yang, Chenguang

2017-02-01

In this paper, a trajectory tracking control law is proposed for a class of marine surface vessels in the presence of full-state constraints and dynamics uncertainties. A barrier Lyapunov function (BLF) based control is employed to prevent states from violating the constraints. Neural networks are used to approximate the system uncertainties in the control design, and the control law is designed by using the Moore-Penrose inverse. The proposed control is able to compensate for the effects of full-state constraints. Meanwhile, the signals in the closed-loop system are guaranteed to be semiglobally uniformly bounded, with the asymptotic tracking being achieved. Finally, the performance of the proposed control has been tested and verified by simulation studies.

Measurement of the adsorption energy difference between ortho- and para-D2 on an amorphous ice surface.

PubMed

Amiaud, L; Momeni, A; Dulieu, F; Fillion, J H; Matar, E; Lemaire, J-L

2008-02-08

Molecular hydrogen interaction on water ice surfaces is a major process taking place in interstellar dense clouds. By coupling laser detection and classical thermal desorption spectroscopy, it is possible to study the effect of rotation of D(2) on adsorption on amorphous solid water ice surfaces. The desorption profiles of ortho- and para-D(2) are different. This difference is due to a shift in the adsorption energy distribution of the two lowest rotational states. Molecules in J''=1 rotational state are on average more strongly bound to the ice surface than those in J''=0 rotational state. This energy difference is estimated to be 1.4+/-0.3 meV. This value is in agreement with previous calculation and interpretation. The nonspherical wave function J'' =1 has an interaction with the asymmetric part of the adsorption potential and contributes positively in the binding energy.

Antibonding ground state of adatom molecules in bulk Dirac semimetals

NASA Astrophysics Data System (ADS)

Marques, Y.; Obispo, A. E.; Ricco, L. S.; de Souza, M.; Shelykh, I. A.; Seridonio, A. C.

2017-07-01

The ground state of the diatomic molecules in nature is inevitably bonding, and its first excited state is antibonding. We demonstrate theoretically that, for a pair of distant adatoms placed buried in three-dimensional-Dirac semimetals, this natural order of the states can be reversed and an antibonding ground state occurs at the lowest energy of the so-called bound states in the continuum. We propose an experimental protocol with the use of a scanning tunneling microscope tip to visualize the topographic map of the local density of states on the surface of the system to reveal the emerging physics.

Bound state and localization of excitation in many-body open systems

NASA Astrophysics Data System (ADS)

Cui, H. T.; Shen, H. Z.; Hou, S. C.; Yi, X. X.

2018-04-01

We study the exact bound state and time evolution for single excitations in one-dimensional X X Z spin chains within a non-Markovian reservoir. For the bound state, a common feature is the localization of single excitations, which means the spontaneous emission of excitations into the reservoir is prohibited. Exceptionally, the pseudo-bound state can be found, for which the single excitation has a finite probability of emission into the reservoir. In addition, a critical energy scale for bound states is also identified, below which only one bound state exists, and it is also the pseudo-bound state. The effect of quasirandom disorder in the spin chain is also discussed; such disorder induces the single excitation to locate at some spin sites. Furthermore, to display the effect of bound state and disorder on the preservation of quantum information, the time evolution of single excitations in spin chains is studied exactly. An interesting observation is that the excitation can stay at its initial location with high probability only when the bound state and disorder coexist. In contrast, when either one of them is absent, the information of the initial state can be erased completely or becomes mixed. This finding shows that the combination of bound state and disorder can provide an ideal mechanism for quantum memory.

Superconductivity in doped Dirac semimetals

NASA Astrophysics Data System (ADS)

Hashimoto, Tatsuki; Kobayashi, Shingo; Tanaka, Yukio; Sato, Masatoshi

2016-07-01

We theoretically study intrinsic superconductivity in doped Dirac semimetals. Dirac semimetals host bulk Dirac points, which are formed by doubly degenerate bands, so the Hamiltonian is described by a 4 ×4 matrix and six types of k -independent pair potentials are allowed by the Fermi-Dirac statistics. We show that the unique spin-orbit coupling leads to characteristic superconducting gap structures and d vectors on the Fermi surface and the electron-electron interaction between intra and interorbitals gives a novel phase diagram of superconductivity. It is found that when the interorbital attraction is dominant, an unconventional superconducting state with point nodes appears. To verify the experimental signature of possible superconducting states, we calculate the temperature dependence of bulk physical properties such as electronic specific heat and spin susceptibility and surface state. In the unconventional superconducting phase, either dispersive or flat Andreev bound states appear between point nodes, which leads to double peaks or a single peak in the surface density of states, respectively. As a result, possible superconducting states can be distinguished by combining bulk and surface measurements.

Coulomb bound states of strongly interacting photons

DOE PAGES

Maghrebi, M. F.; Gullans, Michael J.; Bienias, P.; ...

2015-09-16

We show that two photons coupled to Rydberg states via electromagnetically induced transparency (EIT) can interact via an effective Coulomb potential. The interaction then gives rise to a continuum of two-body bound states. Within the continuum, metastable bound states are distinguished in analogy with quasi-bound states tunneling through a potential barrier. We find multiple branches of metastable bound states whose energy spectrum is governed by the Coulomb problem, thus obtaining a photonic analogue of the hydrogen atom. These states propagate with a negative group velocity in the medium, which allows for a simple preparation and detection scheme, before they slowlymore » decay to pairs of bound Rydberg atoms. As a result, we verify the metastability and backward propagation of these Coulomb bound states with exact numerical simulations.« less

Electron emission from surfaces resulting from low energy positron bombardment

NASA Astrophysics Data System (ADS)

Mukherjee, Saurabh

Measurements of the secondary electron energy spectra resulting from very low energy positron bombardment of a polycrystalline Au and Cu (100) surfaces are presented that provide evidence for a single step transition from an unbound scattering state to an image potential bound state. The primary positron energy threshold for secondary electron emission and energy cutoff of the positron induced secondary electron energy peak are consistent with an Auger like process in which an incident positron make a transition from a scattering state to a surface-image potential bound while transferring all of the energy difference to an outgoing secondary electron. We term this process: the Auger mediated quantum sticking effect (AQSE). The intensities of the positron induced secondary electron peak are used to estimate the probability of this process as a function of incident positron energy. Positron annihilation induced Auger spectra (PAES) of Cu and Au are presented that are free of all primary beam induced secondary electron background. This background was eliminated by setting the positron beam energy below AQSE threshold. The background free PAES spectra obtained include the first measurements of the low energy tail of CVV Auger transitions all the way down to zero kinetic energy. The integrated intensity of this tail is several times larger than Auger peak itself which provides strong evidence for multi-electron Auger processes.

Superconducting topological surface states in the noncentrosymmetric bulk superconductor PbTaSe2.

PubMed

Guan, Syu-You; Chen, Peng-Jen; Chu, Ming-Wen; Sankar, Raman; Chou, Fangcheng; Jeng, Horng-Tay; Chang, Chia-Seng; Chuang, Tien-Ming

2016-11-01

The search for topological superconductors (TSCs) is one of the most urgent contemporary problems in condensed matter systems. TSCs are characterized by a full superconducting gap in the bulk and topologically protected gapless surface (or edge) states. Within each vortex core of TSCs, there exists the zero-energy Majorana bound states, which are predicted to exhibit non-Abelian statistics and to form the basis of the fault-tolerant quantum computation. To date, no stoichiometric bulk material exhibits the required topological surface states (TSSs) at the Fermi level ( E F ) combined with fully gapped bulk superconductivity. We report atomic-scale visualization of the TSSs of the noncentrosymmetric fully gapped superconductor PbTaSe 2 . Using quasi-particle scattering interference imaging, we find two TSSs with a Dirac point at E ≅ 1.0 eV, of which the inner TSS and the partial outer TSS cross E F , on the Pb-terminated surface of this fully gapped superconductor. This discovery reveals PbTaSe 2 as a promising candidate for TSC.

Local density of states in two-dimensional topological superconductors under a magnetic field: Signature of an exterior Majorana bound state

NASA Astrophysics Data System (ADS)

Suzuki, Shu-Ichiro; Kawaguchi, Yuki; Tanaka, Yukio

2018-04-01

We study quasiparticle states on a surface of a topological insulator (TI) with proximity-induced superconductivity under an external magnetic field. An applied magnetic field creates two Majorana bound states: a vortex Majorana state localized inside a vortex core and an exterior Majorana state localized along a circle centered at the vortex core. We calculate the spin-resolved local density of states (LDOS) and demonstrate that the shrinking of the radius of the exterior Majorana state, predicted in R. S. Akzyanov et al., Phys. Rev. B 94, 125428 (2016), 10.1103/PhysRevB.94.125428, under a strong magnetic field can be seen in LDOS without smeared out by nonzero-energy states. The spin-resolved LDOS further reveals that the spin of the exterior Majorana state is strongly spin-polarized. Accordingly, the induced odd-frequency spin-triplet pairs are found to be spin-polarized as well. In order to detect the exterior Majorana states, however, the Fermi energy should be closed to the Dirac point to avoid contributions from continuum levels. We also study a different two-dimensional topological-superconducting system where a two-dimensional electron gas with the spin-orbit coupling is sandwiched between an s -wave superconductor and a ferromagnetic insulator. We show that the radius of an exterior Majorana state can be tuned by an applied magnetic field. However, on the contrary to the results at a TI surface, neither the exterior Majorana state nor the induced odd-frequency spin-triplet pairs are spin-polarized. We conclude that the spin polarization of the Majorana state is attributed to the spin-polarized Landau level, which is characteristic for systems with the Dirac-like dispersion.

Highly mobile oxygen holes in magnesium oxide

NASA Technical Reports Server (NTRS)

Freund, Minoru M.; Freund, Friedemann; Batllo, Francois

1989-01-01

High-purity MgO exhibits an unexpected giant anomaly of the apparent static dielectric constant and a positive surface charge of the order of 5 x 10 to the 21st/cu cm in the top 15 nm. It is postulated that the MgO matrix contains traces of peroxy defects, O2(2-), associated with Mg(2+) vacancies. Above approximately 400 C the O2(2-) dissociates to vacancy bound O(-) and highly mobile O(-) states, which diffuse to the surface, giving rise to a high surface conductivity.

Supramolecular Structures with Blood Plasma Proteins, Sugars and Nanosilica

NASA Astrophysics Data System (ADS)

Turov, V. V.; Gun'ko, V. M.; Galagan, N. P.; Rugal, A. A.; Barvinchenko, V. M.; Gorbyk, P. P.

Supramolecular structures with blood plasma proteins (albumin, immunoglobulin and fibrinogen (HPF)), protein/water/silica and protein/water/ silica/sugar (glucose, fructose and saccharose) were studied by NMR, adsorption, IR and UV spectroscopy methods. Hydration parameters, amounts of weakly and strongly bound waters and interfacial energy (γ S) were determined over a wide range of component concentrations. The γ S(C protein,C silica) graphs were used to estimate the energy of protein-protein, protein-surface and particle-particle interactions. It was shown that interfacial energy of self-association (γ as) of protein molecules depends on a type of proteins. A large fraction of water bound to proteins can be displaced by sugars, and the effect of disaccharide (saccharose) was greater than that of monosugars. Changes in the structural parameters of cavities in HPF molecules and complexes with HPF/silica nanoparticles filled by bound water were analysed using NMR-cryoporometry showing that interaction of proteins with silica leads to a significant decrease in the amounts of water bound to both protein and silica surfaces. Bionanocomposites with BSA/nanosilica/sugar can be used to influence states of living cells and tissues after cryopreservation or other treatments. It was shown that interaction of proteins with silica leads to strong decrease in the volume of all types of internal cavities filled by water.

Molecular plasmonics: The role of rovibrational molecular states in exciton-plasmon materials under strong-coupling conditions

NASA Astrophysics Data System (ADS)

Sukharev, Maxim; Charron, Eric

2017-03-01

We extend the model of exciton-plasmon materials to include a rovibrational structure of molecules using wave-packet propagations on electronic potential energy surfaces. Our model replaces conventional two-level emitters with more complex molecules, allowing us to examine the influence of alignment and vibrational dynamics on strong coupling with surface plasmon-polaritons. We apply the model to a hybrid system comprising a thin layer of molecules placed on top of a periodic array of slits. Rigorous simulations are performed for two types of molecular systems described by vibrational bound-bound and bound-continuum electronic transitions. Calculations reveal new features in transmission, reflection, and absorption spectra, including the observation of significantly higher values of the Rabi splitting and vibrational patterns clearly seen in the corresponding spectra. We also examine the influence of anisotropic initial conditions on optical properties of hybrid materials, demonstrating that the optical response of the system is significantly affected by an initial prealignment of the molecules. Our work demonstrates that prealigned molecules could serve as an efficient probe for the subdiffraction characterization of the near-field near metal interfaces.

Toward tailoring Majorana bound states in artificially constructed magnetic atom chains on elemental superconductors

PubMed Central

Thorwart, Michael

2018-01-01

Realizing Majorana bound states (MBS) in condensed matter systems is a key challenge on the way toward topological quantum computing. As a promising platform, one-dimensional magnetic chains on conventional superconductors were theoretically predicted to host MBS at the chain ends. We demonstrate a novel approach to design of model-type atomic-scale systems for studying MBS using single-atom manipulation techniques. Our artificially constructed atomic Fe chains on a Re surface exhibit spin spiral states and a remarkable enhancement of the local density of states at zero energy being strongly localized at the chain ends. Moreover, the zero-energy modes at the chain ends are shown to emerge and become stabilized with increasing chain length. Tight-binding model calculations based on parameters obtained from ab initio calculations corroborate that the system resides in the topological phase. Our work opens new pathways to design MBS in atomic-scale hybrid structures as a basis for fault-tolerant topological quantum computing. PMID:29756034

Toward tailoring Majorana bound states in artificially constructed magnetic atom chains on elemental superconductors.

PubMed

Kim, Howon; Palacio-Morales, Alexandra; Posske, Thore; Rózsa, Levente; Palotás, Krisztián; Szunyogh, László; Thorwart, Michael; Wiesendanger, Roland

2018-05-01

Realizing Majorana bound states (MBS) in condensed matter systems is a key challenge on the way toward topological quantum computing. As a promising platform, one-dimensional magnetic chains on conventional superconductors were theoretically predicted to host MBS at the chain ends. We demonstrate a novel approach to design of model-type atomic-scale systems for studying MBS using single-atom manipulation techniques. Our artificially constructed atomic Fe chains on a Re surface exhibit spin spiral states and a remarkable enhancement of the local density of states at zero energy being strongly localized at the chain ends. Moreover, the zero-energy modes at the chain ends are shown to emerge and become stabilized with increasing chain length. Tight-binding model calculations based on parameters obtained from ab initio calculations corroborate that the system resides in the topological phase. Our work opens new pathways to design MBS in atomic-scale hybrid structures as a basis for fault-tolerant topological quantum computing.

Hyperspherical nuclear motion of H3 + and D3 + in the electronic triplet state, a 3Sigmau +.

PubMed

Ferreira, Tiago Mendes; Alijah, Alexander; Varandas, António J C

2008-02-07

The potential energy surface of H(3) (+) in the lowest electronic triplet state, a (3)Sigma(u) (+), shows three equivalent minima at linear nuclear configurations. The vibrational levels of H(3) (+) and D(3) (+) on this surface can therefore be described as superimposed linear molecule states. Owing to such a superposition, each vibrational state characterized by quantum numbers of an isolated linear molecule obtains a one- and a two-dimensional component. The energy splittings between the two components have now been rationalized within a hyperspherical picture. It is shown that nuclear motion along the hyperangle phi mainly accounts for the splittings and provides upper bounds. This hyperspherical motion can be considered an extension of the antisymmetric stretching motion of the individual linear molecule.

The Phosphorylation of Vascular Endothelial Growth Factor Receptor-2 (VEGFR-2) by Engineered Surfaces with Electrostatically or Covalently Immobilized VEGF

PubMed Central

Anderson, Sean M.; Chen, Tom T.; Iruela-Arispe, M. Luisa; Segura, Tatiana

2010-01-01

Growth factors are a class of signaling proteins that direct cell fate through interaction with cell surface receptors. Although a myriad of possible cell fates stem from a growth factor binding to its receptor, the signaling cascades that result in one fate over another are still being elucidated. One possible mechanism by which nature modulates growth factor signaling is through the method of presentation of the growth factor – soluble or immobilized (matrix bound). Here we present the methodology to study signaling of soluble versus immobilized VEGF through VEGFR-2. We have designed a strategy to covalently immobilize VEGF using its heparin-binding domain to orient the molecule (bind) and a secondary functional group to mediate covalent binding (lock). This bind-and-lock approach aims to allow VEGF to assume a bioactive orientation before covalent immobilization. Surface plasmon resonance (SPR) demonstrated heparin and VEGF binding with surface densities of 60 ng/cm2 and 100 pg/cm2, respectively. ELISA experiments confirmed VEGF surface density and showed that electrostatically bound VEGF releases in cell medium and heparin solutions while covalently bound VEGF remains immobilized. Electrostatically bound VEGF and covalently bound VEGF phosphorylate VEGFR-2 in both VEGFR-2 transfected cells and VEGFR-2 endogenously producing cells. HUVECs plated on VEGF functionalized surfaces showed different morphologies between surface-bound VEGF and soluble VEGF. The surfaces synthesized in these studies allow for the study of VEGF/VEGFR-2 signaling induced by covalently bound, electrostatically bound, and soluble VEGF and may provide further insight into the design of materials for the generation of a mature and stable vasculature. PMID:19540581

Utiliizing Vegetative Buffer Strips to Remove Dissolved and Sediment-Bound Herbicides from Surface Water Runoff

USDA-ARS?s Scientific Manuscript database

Current federal and state soil and water conservation programs consist primarily of cost-sharing or compensating farmers for implementing a set of pre-defined best management practices which do not consider specific environmental outcomes or cost-effectiveness of the program at the farm or watershed...

Pickup Ion Mass Spectrometry for Surface Bounded Exospheres and Composition Mapping of Lunar and Planetary Surfaces

NASA Technical Reports Server (NTRS)

Keller, J. W.; Zurbuchen, T. H.; Baragiola, R. A.; Cassidy, T. A.; Chornay, D. J.; Collier, M. R.; Hartle, R. E.; Johnson, R. E.; Killen, R. M.; Koehn, P.

2005-01-01

Many of the small to medium sized objects in the solar system can be characterized as having surface bounded exospheres, or atmospheres so tenuous that scale lengths for inter-particle collisions are much larger than the dimensions of the objects. The atmospheres of these objects are the product of their surfaces, both the surface composition and the interactions that occur on them and also their interiors when gases escape from there. Thus by studying surface bounded exospheres it is possible to develop insight into the composition and processes that are taking place on the surface and interiors of these objects. The Moon and Mercury are two examples of planetary bodies with surface bounded exospheres that have been studied through spectroscopic observations of sodium, potassium, and, on the moon, mass spectrometric measurements of lunar gases such as argon and helium.

Silica-coated gold nanorods as saturable absorber for bound-state pulse generation in a fiber laser with near-zero dispersion

NASA Astrophysics Data System (ADS)

Wang, Xude; Luo, Aiping; Luo, Zhichao; Liu, Meng; Zou, Feng; Zhu, Yanfang; Xue, Jianping; Xu, Wencheng

2017-11-01

We presented a bound-state operation in a fiber laser with near-zero anomalous dispersion based on a silica-coated gold nanorods (GNRs@SiO2) saturable absorber (SA). Using a balanced twin detector measurement technique, the modulation depth and nonsaturable loss of the GNRs@SiO2 SA were measured to be approximately 3.5% and 39.3%, respectively. By virtue of the highly nonlinear effect of the GNRs@SiO2 SA, the bound-state pulses could be easily observed. Besides the lower-order bound-state pulses with two, three, and four solitons, the higher-order bound states with up to 12 solitons were also obtained in the laser cavity. The pulse profiles of the higher-order bound states were further reconstructed theoretically. The experimental results would give further insight towards understanding the complex nonlinear dynamics of bound-state pulses in fiber lasers.

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

Dou, Xu; Kotov, Valeri N.; Uchoa, Bruno

Quantum spin-orbital liquids are elusive strongly correlated states of matter that emerge from quantum frustration between spin and orbital degrees of freedom. A promising route towards the observation of those states is the creation of artificial Mott insulators where antiferromagnetic correlations between spins and orbitals can be designed. We show that Coulomb impurity lattices on the surface of gapped honeycomb substrates, such as graphene on SiC, can be used to simulate SU(4) symmetric spin-orbital lattice models. We exploit the property that massive Dirac fermions form mid-gap bound states with spin and valley degeneracies in the vicinity of a Coulomb impurity.more » Due to electronic repulsion, the antiferromagnetic correlations of the impurity lattice are driven by a super-exchange interaction with SU(4) symmetry, which emerges from the bound states degeneracy at quarter filling. We propose that quantum spin-orbital liquids can be engineered in artificially designed solid-state systems at vastly higher temperatures than achievable in optical lattices with cold atoms. Lastly, we discuss the experimental setup and possible scenarios for candidate quantum spin-liquids in Coulomb impurity lattices of various geometries.« less

Designing Quantum Spin-Orbital Liquids in Artificial Mott Insulators

PubMed Central

Dou, Xu; Kotov, Valeri N.; Uchoa, Bruno

2016-01-01

Quantum spin-orbital liquids are elusive strongly correlated states of matter that emerge from quantum frustration between spin and orbital degrees of freedom. A promising route towards the observation of those states is the creation of artificial Mott insulators where antiferromagnetic correlations between spins and orbitals can be designed. We show that Coulomb impurity lattices on the surface of gapped honeycomb substrates, such as graphene on SiC, can be used to simulate SU(4) symmetric spin-orbital lattice models. We exploit the property that massive Dirac fermions form mid-gap bound states with spin and valley degeneracies in the vicinity of a Coulomb impurity. Due to electronic repulsion, the antiferromagnetic correlations of the impurity lattice are driven by a super-exchange interaction with SU(4) symmetry, which emerges from the bound states degeneracy at quarter filling. We propose that quantum spin-orbital liquids can be engineered in artificially designed solid-state systems at vastly higher temperatures than achievable in optical lattices with cold atoms. We discuss the experimental setup and possible scenarios for candidate quantum spin-liquids in Coulomb impurity lattices of various geometries. PMID:27553516

Towards Realistic Implementations of a Majorana Surface Code.

PubMed

Landau, L A; Plugge, S; Sela, E; Altland, A; Albrecht, S M; Egger, R

2016-02-05

Surface codes have emerged as promising candidates for quantum information processing. Building on the previous idea to realize the physical qubits of such systems in terms of Majorana bound states supported by topological semiconductor nanowires, we show that the basic code operations, namely projective stabilizer measurements and qubit manipulations, can be implemented by conventional tunnel conductance probes and charge pumping via single-electron transistors, respectively. The simplicity of the access scheme suggests that a functional code might be in close experimental reach.

Helium cluster isolation spectroscopy

NASA Astrophysics Data System (ADS)

Higgins, John Paul

Clusters of helium, each containing ~103- 104 atoms, are produced in a molecular beam and are doped with alkali metal atoms (Li, Na, and K) and large organic molecules. Electronic spectroscopy in the visible and UV regions of the spectrum is carried out on the dopant species. Since large helium clusters are liquid and attain an equilibrium internal temperature of 0.4 K, they interact weakly with atoms or molecules absorbed on their surface or resident inside the cluster. The spectra that are obtained are characterized by small frequency shifts from the positions of the gas phase transitions, narrow lines, and cold vibrational temperatures. Alkali atoms aggregate on the helium cluster surface to form dimers and trimers. The spectra of singlet alkali dimers exhibit the presence of elementary excitations in the superfluid helium cluster matrix. It is found that preparation of the alkali molecules on the surface of helium clusters leads to the preferential formation of high-spin, van der Waals bound, triplet dimers and quartet trimers. Four bound-bound and two bound-free transitions are observed in the triplet manifold of the alkali dimers. The quartet trimers serve as an ideal system for the study of a simple unimolecular reaction in the cold helium cluster environment. Analysis of the lowest quartet state provides valuable insight into three-body forces in a van der Waals trimer. The wide range of atomic and molecular systems studied in this thesis constitutes a preliminary step in the development of helium cluster isolation spectroscopy, a hybrid technique combining the advantages of high resolution spectroscopy with the synthetic, low temperature environment of matrices.

Stability of the lepton bag model based on the Kerr–Newman solution

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

Burinskii, A., E-mail: bur@ibrae.ac.ru

2015-11-15

We show that the lepton bag model considered in our previous paper [10], generating the external gravitational and electromagnetic fields of the Kerr–Newman (KN) solution, is supersymmetric and represents a BPS-saturated soliton interpolating between the internal vacuum state and the external KN solution. We obtain Bogomolnyi equations for this phase transition and show that the Bogomolnyi bound determines all important features of this bag model, including its stable shape. In particular, for the stationary KN solution, the BPS bound provides stability of the ellipsoidal form of the bag and the formation of the ring–string structure at its border, while formore » the periodic electromagnetic excitations of the KN solution, the BPS bound controls the deformation of the surface of the bag, reproducing the known flexibility of bag models.« less

Universal bounds on charged states in 2d CFT and 3d gravity

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

Benjamin, Nathan; Dyer, Ethan; Fitzpatrick, A. Liam

2016-08-04

We derive an explicit bound on the dimension of the lightest charged state in two dimensional conformal field theories with a global abelian symmetry. We find that the bound scales with c and provide examples that parametrically saturate this bound. We also prove that any such theory must contain a state with charge-to-mass ratio above a minimal lower bound. As a result, we comment on the implications for charged states in three dimensional theories of gravity.

Photon-assisted tunneling through a topological superconductor with Majorana bound states

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

Tang, Han-Zhao; Zhang, Ying-Tao, E-mail: zhangyt@mail.hebtu.edu.cn; Liu, Jian-Jun, E-mail: liujj@mail.hebtu.edu.cn

Employing the Keldysh Nonequilibrium Green’s function method, we investigate time-dependent transport through a topological superconductor with Majorana bound states in the presence of a high frequency microwave field. It is found that Majorana bound states driven by photon-assisted tunneling can absorb(emit) photons and the resulting photon-assisted tunneling side band peaks can split the Majorana bound state that then appears at non-zero bias. This splitting breaks from the current opinion that Majorana bound states appear only at zero bias and thus provides a new experimental method for detecting Majorana bound states in the Non-zero-energy mode. We not only demonstrate that themore » photon-assisted tunneling side band peaks are due to Non-zero-energy Majorana bound states, but also that the height of the photon-assisted tunneling side band peaks is related to the intensity of the microwave field. It is further shown that the time-varying conductance induced by the Majorana bound states shows negative values for a certain period of time, which corresponds to a manifestation of the phase coherent time-varying behavior in mesoscopic systems.« less

Extending the Diffuse Layer Model of Surface Acidity Behavior: III. Estimating Bound Site Activity Coefficients

EPA Science Inventory

Although detailed thermodynamic analyses of the 2-pK diffuse layer surface complexation model generally specify bound site activity coefficients for the purpose of accounting for those non-ideal excess free energies contributing to bound site electrochemical potentials, in applic...

Conformational Plasticity of the Cell-Penetrating Peptide SAP As Revealed by Solid-State 19F-NMR and Circular Dichroism Spectroscopies.

PubMed

Afonin, Sergii; Kubyshkin, Vladimir; Mykhailiuk, Pavel K; Komarov, Igor V; Ulrich, Anne S

2017-07-13

The cell-penetrating peptide SAP, which was designed as an amphipathic poly-l-proline helix II (PPII), was suggested to self-assemble into regular fibrils that are relevant for its internalization. Herein we have analyzed the structure of SAP in the membrane-bound state by solid-state 19 F-NMR, which revealed other structural states, in addition to the expected surface-aligned PPII. Trifluoromethyl-bicyclopentyl-glycine (CF 3 -Bpg) and two rigid isomers of trifluoromethyl-4,5-methanoprolines (CF 3 -MePro) were used as labels for 19 F-NMR analysis. The equilibria between different conformations of SAP were studied and were found to be shifted by the substituents at Pro-11. Synchrotron-CD results suggested that substituting Pro-11 by CF 3 -MePro governed the coil-to-PPII equilibrium in solution and in the presence of a lipid bilayer. Using CD and 19 F-NMR, we examined the slow kinetics of the association of SAP with membranes and the dependence of the SAP conformational dynamics on the lipid composition. The peptide did not bind to lipids in the solid ordered phase and aggregated only in the liquid ordered "raft"-like bilayers. Self-association could not be detected in solution or in the presence of liquid disordered membranes. Surface-bound amphipathic SAP in a nonaggregated state was structured as a mixture of nonideal extended conformations reflecting the equilibrium already present in solution, i.e., before binding to the membrane.

Testing the Perey effect

DOE PAGES

Titus, L. J.; Nunes, Filomena M.

2014-03-12

Here, the effects of non-local potentials have historically been approximately included by applying a correction factor to the solution of the corresponding equation for the local equivalent interaction. This is usually referred to as the Perey correction factor. In this work we investigate the validity of the Perey correction factor for single-channel bound and scattering states, as well as in transfer (p, d) cross sections. Method: We solve the scattering and bound state equations for non-local interactions of the Perey-Buck type, through an iterative method. Using the distorted wave Born approximation, we construct the T-matrix for (p,d) on 17O, 41Ca,more » 49Ca, 127Sn, 133Sn, and 209Pb at 20 and 50 MeV. As a result, we found that for bound states, the Perey corrected wave function resulting from the local equation agreed well with that from the non-local equation in the interior region, but discrepancies were found in the surface and peripheral regions. Overall, the Perey correction factor was adequate for scattering states, with the exception of a few partial waves corresponding to the grazing impact parameters. These differences proved to be important for transfer reactions. In conclusion, the Perey correction factor does offer an improvement over taking a direct local equivalent solution. However, if the desired accuracy is to be better than 10%, the exact solution of the non-local equation should be pursued.« less

Global neural dynamic surface tracking control of strict-feedback systems with application to hypersonic flight vehicle.

PubMed

Xu, Bin; Yang, Chenguang; Pan, Yongping

2015-10-01

This paper studies both indirect and direct global neural control of strict-feedback systems in the presence of unknown dynamics, using the dynamic surface control (DSC) technique in a novel manner. A new switching mechanism is designed to combine an adaptive neural controller in the neural approximation domain, together with the robust controller that pulls the transient states back into the neural approximation domain from the outside. In comparison with the conventional control techniques, which could only achieve semiglobally uniformly ultimately bounded stability, the proposed control scheme guarantees all the signals in the closed-loop system are globally uniformly ultimately bounded, such that the conventional constraints on initial conditions of the neural control system can be relaxed. The simulation studies of hypersonic flight vehicle (HFV) are performed to demonstrate the effectiveness of the proposed global neural DSC design.

Transient response in granular bounded heap flows

NASA Astrophysics Data System (ADS)

Xiao, Hongyi; Ottino, Julio M.; Lueptow, Richard M.; Umbanhowar, Paul B.

2017-11-01

Heap formation, a canonical granular flow, is common in industry and is also found in nature. Here, we study the transition between steady flow states in quasi-2D bounded heaps by suddenly changing the feed rate from one fixed value to another. During the transition, in both experiments and discrete element method simulations, an additional wedge of flowing particles propagates over the rising free surface. The downstream edge of the wedge - the wedge front - moves downstream with velocity inversely proportional to the square root of time. An additional longer duration transient process continues after the wedge front reaches the downstream wall. The transient flux profile during the entire transition is well modeled by a diffusion-like equation derived from local mass balance and a local linear relation between the flux and the surface slope. Scalings for the transient kinematics during the flow transitions are developed based on the flux profiles. Funded by NSF Grant CBET-1511450.

In silico Analysis of HIV-1 Env-gp120 Reveals Structural Bases for Viral Adaptation in Growth-Restrictive Cells

PubMed Central

Yokoyama, Masaru; Nomaguchi, Masako; Doi, Naoya; Kanda, Tadahito; Adachi, Akio; Sato, Hironori

2016-01-01

Variable V1/V2 and V3 loops on human immunodeficiency virus type 1 (HIV-1) envelope-gp120 core play key roles in modulating viral competence to recognize two infection receptors, CD4 and chemokine-receptors. However, molecular bases for the modulation largely remain unclear. To address these issues, we constructed structural models for a full-length gp120 in CD4-free and -bound states. The models showed topologies of gp120 surface loop that agree with those in reported structural data. Molecular dynamics simulation showed that in the unliganded state, V1/V2 loop settled into a thermodynamically stable arrangement near V3 loop for conformational masking of V3 tip, a potent neutralization epitope. In the CD4-bound state, however, V1/V2 loop was rearranged near the bound CD4 to support CD4 binding. In parallel, cell-based adaptation in the absence of anti-viral antibody pressures led to the identification of amino acid substitutions that individually enhance viral entry and growth efficiencies in association with reduced sensitivity to CCR5 antagonist TAK-779. Notably, all these substitutions were positioned on the receptors binding surfaces in V1/V2 or V3 loop. In silico structural studies predicted some physical changes of gp120 by substitutions with alterations in viral replication phenotypes. These data suggest that V1/V2 loop is critical for creating a gp120 structure that masks co-receptor binding site compatible with maintenance of viral infectivity, and for tuning a functional balance of gp120 between immune escape ability and infectivity to optimize HIV-1 replication fitness. PMID:26903989

NITROGEN BOUNDING STUDY: METHODS FOR ESTIMATING THE RELATIVE EFFECTS OF SULFUR AND NITROGEN DEPOSITION ON SURFACE WATER CHEMISTRY

EPA Science Inventory

The leaching of atmospherically deposited nitrogen from forested watersheds may acidify lakes and streams. he Nitrogen Bounding Study evaluates the potential range of such adverse effects. he study estimates bounds on changes in regional-scale surface water acidification that mig...

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

Mezei, Márk

A global quench is an interesting setting where we can study thermalization of subsystems in a pure state. We investigate entanglement entropy (EE) growth in global quenches in holographic field theories and relate some of its aspects to quantities characterizing chaos. More specifically we obtain four key results: 1. We prove holographic bounds on the entanglement velocity vE and the butterfly effect speed vB that arises in the study of chaos. 2. We obtain the EE as a function of time for large spherical entangling surfaces analytically. We show that the EE is insensitive to the details of the initialmore » state or quench protocol. 3. In a thermofield double state we determine analytically the two-sided mutual information between two large concentric spheres separated in time. 4. We derive a bound on the rate of growth of EE for arbitrary shapes, and develop an expansion for EE at early times. In a companion paper, these results are put in the broader context of EE growth in chaotic systems: we relate EE growth to the chaotic spreading of operators, derive bounds on EE at a given time, and compare the holographic results to spin chain numerics and toy models. In this paper, we perform holographic calculations that provide the basis of arguments presented in that paper.« less

On entanglement spreading from holography

DOE PAGES

Mezei, Márk

2017-05-11

A global quench is an interesting setting where we can study thermalization of subsystems in a pure state. We investigate entanglement entropy (EE) growth in global quenches in holographic field theories and relate some of its aspects to quantities characterizing chaos. More specifically we obtain four key results: 1. We prove holographic bounds on the entanglement velocity vE and the butterfly effect speed vB that arises in the study of chaos. 2. We obtain the EE as a function of time for large spherical entangling surfaces analytically. We show that the EE is insensitive to the details of the initialmore » state or quench protocol. 3. In a thermofield double state we determine analytically the two-sided mutual information between two large concentric spheres separated in time. 4. We derive a bound on the rate of growth of EE for arbitrary shapes, and develop an expansion for EE at early times. In a companion paper, these results are put in the broader context of EE growth in chaotic systems: we relate EE growth to the chaotic spreading of operators, derive bounds on EE at a given time, and compare the holographic results to spin chain numerics and toy models. In this paper, we perform holographic calculations that provide the basis of arguments presented in that paper.« less

Structural and dynamical properties of recombining ultracold neutral plasma

NASA Astrophysics Data System (ADS)

Tiwari, Sanat Kumar; Shaffer, Nathaniel R.; Baalrud, Scott D.

2017-10-01

An ultracold plasma (UCP) is an evolving collection of free charges and bound charges (Rydberg atoms). Over time, bound species concentration increases due to recombination. We present the structural and dynamical properties of an evolving UCP using classical molecular dynamics simulation. Coulomb collapse is avoided using a repulsive core with the attractive Coulomb potential. The repulsive core size controls the concentration of bound states, as it determines the depth of the potential well between opposite charges. We vary the repulsive core size to emulate the quasi-static state of plasma at different time during the evolution. Binary, chain and ring-like bound states are observed in the simulation carried out at different coupling strengths and repulsive core size. The effect of bound states can be seen as molecular peaks in the radial distribution function (RDF). The thermodynamic properties associated with the free charges can be analyzed from RDF by separating free from bound states. These bound states also change the dynamical properties of the plasma. The electron velocity auto-correlation displays oscillations due to the orbital motion in bound states. These bound states act like a neutral species, damping electron plasmon modes and broadening the ion acoustic mode. This work is supported by AFOSR Grant Number FA9550-16-1-0221. It used computational resources by XSEDE, which is supported by NSF Grant Number ACI-1053575.

Searching for DNA Lesions: Structural Evidence for Lower- and Higher-Affinity DNA Binding Conformations of Human Alkyladenine DNA Glycosylase

PubMed Central

2011-01-01

To efficiently repair DNA, human alkyladenine DNA glycosylase (AAG) must search the million-fold excess of unmodified DNA bases to find a handful of DNA lesions. Such a search can be facilitated by the ability of glycosylases, like AAG, to interact with DNA using two affinities: a lower-affinity interaction in a searching process and a higher-affinity interaction for catalytic repair. Here, we present crystal structures of AAG trapped in two DNA-bound states. The lower-affinity depiction allows us to investigate, for the first time, the conformation of this protein in the absence of a tightly bound DNA adduct. We find that active site residues of AAG involved in binding lesion bases are in a disordered state. Furthermore, two loops that contribute significantly to the positive electrostatic surface of AAG are disordered. Additionally, a higher-affinity state of AAG captured here provides a fortuitous snapshot of how this enzyme interacts with a DNA adduct that resembles a one-base loop. PMID:22148158

Marangoni Effects of a Drop in an Extensional Flow: The Role of Surfactant Physical Chemistry

NASA Technical Reports Server (NTRS)

Stebe, Kathleen J.; Balasubramaniam, R. (Technical Monitor)

2002-01-01

While the changes in stresses caused by surfactant adsorption on non-deforming interfaces have been fairly well established, prior to this work, there were few studies addressing how surfactants alter stresses on strongly deforming interfaces. We chose the model problem of a drop in a uniaxial extensional flow to study these stress conditions To model surfactant effects at fluid interfaces, a proper description of the dependence of the surface tension on surface concentration, the surface equation of state, is required. We have adopted a surface equation of state that accounts for the maximum coverage limit; that is, because surfactants have a finite cross sectional area, there is an upper bound to the amount of surfactant that can adsorb in a monolayer. The surface tension reduces strongly only when this maximum coverage is approached. Since the Marangoni stresses go as the derivative of the surface equation of state times the surface concentration gradient, the non-linear equation of state determines both the effect of surfactants in the normal stress jump, (which is balanced by the product of the mean curvature of the interface times the surface tension), and the tangential stress jump, which is balanced by Marangoni stresses. First, the effects of surface coverage and intermolecular interactions among surfactants which drive aggregation of surfactants in the interface were studied. (see Pawar and Stebe, Physics of Fluids).

Orthopositronium study of positron-irradiation-induced surface defects in alumina powder

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

Dauwe, C.; Mbungu-Tsumbu

1992-01-01

Three-quantum-yield measurements and orthopositronium ({ital o}-Ps)-lifetime spectrometry at low temperatures are used to study the interaction of positronium with the surface in fine powders of aluminum oxide. It is found that electron and/or positron irradiation of the specimen induces surface defects which influence the positronium in three ways: (1) A surface positroniumlike bound state is created, (2) the fraction of {ital o}-Ps escaping from the particles is slightly inhibited, and (3) the escaped {ital o}-Ps is quenched into two-quantum decay upon collisions with the surface defects. It is found that the surface Ps state is not populated at the expensemore » of the interparticle Ps. The most likely surface defects are Al{sup 2+} or Al{sup 0} due to the migration of irradiation-induced interstitials. The techniques of long-lifetime spectrometry and of three-quantum-annihilation-rate measurement could be used to study both the diffusion of bulk defects to the surfaces, and the interactions of {ital o}-Ps to surface defects.« less

Inhomogeneous Weyl and Dirac Semimetals: Transport in Axial Magnetic Fields and Fermi Arc Surface States from Pseudo-Landau Levels

NASA Astrophysics Data System (ADS)

Grushin, Adolfo G.; Venderbos, Jörn W. F.; Vishwanath, Ashvin; Ilan, Roni

2016-10-01

Topological Dirac and Weyl semimetals have an energy spectrum that hosts Weyl nodes appearing in pairs of opposite chirality. Topological stability is ensured when the nodes are separated in momentum space and unique spectral and transport properties follow. In this work, we study the effect of a space-dependent Weyl node separation, which we interpret as an emergent background axial-vector potential, on the electromagnetic response and the energy spectrum of Weyl and Dirac semimetals. This situation can arise in the solid state either from inhomogeneous strain or nonuniform magnetization and can also be engineered in cold atomic systems. Using a semiclassical approach, we show that the resulting axial magnetic field B5 is observable through an enhancement of the conductivity as σ ˜B52 due to an underlying chiral pseudomagnetic effect. We then use two lattice models to analyze the effect of B5 on the spectral properties of topological semimetals. We describe the emergent pseudo-Landau-level structure for different spatial profiles of B5, revealing that (i) the celebrated surface states of Weyl semimetals, the Fermi arcs, can be reinterpreted as n =0 pseudo-Landau levels resulting from a B5 confined to the surface, (ii) as a consequence of position-momentum locking, a bulk B5 creates pseudo-Landau levels interpolating in real space between Fermi arcs at opposite surfaces, and (iii) there are equilibrium bound currents proportional to B5 that average to zero over the sample, which are the analogs of bound currents in magnetic materials. We conclude by discussing how our findings can be probed experimentally.

Quantum dynamics of the Eley-Rideal hydrogen formation reaction on graphite at typical interstellar cloud conditions.

PubMed

Casolo, Simone; Martinazzo, Rocco; Bonfanti, Matteo; Tantardini, Gian Franco

2009-12-31

Eley-Rideal formation of hydrogen molecules on graphite, as well as competing collision induced processes, are investigated quantum dynamically at typical interstellar cloud conditions, focusing in particular on gas-phase temperatures below 100 K, where much of the chemistry of the so-called diffuse clouds takes place on the surface of bare carbonaceous dust grains. Collisions of gas-phase hydrogen atoms with both chemisorbed and physisorbed species are considered using available potential energy surfaces (Sha et al., J. Chem. Phys.2002 116, 7158), and state-to-state, energy-resolved cross sections are computed for a number of initial vibrational states of the hydrogen atoms bound to the surface. Results show that (i) product molecules are internally hot in both cases, with vibrational distributions sharply peaked around few (one or two) vibrational levels, and (ii) cross sections for chemisorbed species are 2-3x smaller than those for physisorbed ones. In particular, we find that H(2) formation cross sections out of chemically bound species decrease steadily when the temperature drops below approximately 1000 K, and this is likely due to a quantum reflection phenomenon. This suggests that such Eley-Rideal reaction is all but efficient in the relevant gas-phase temperature range, even when gas-phase H atoms happen to chemisorb barrierless to the surface as observed, e.g., for forming so-called para dimers. Comparison with results from classical trajectory calculations highlights the need of a quantum description of the dynamics in the astrophysically relevant energy range, whereas preliminary results of an extensive first-principles investigation of the reaction energetics reveal the importance of the adopted substrate model.

A potential-energy surface study of the 2A1 and low-lying dissociative states of the methoxy radical

NASA Technical Reports Server (NTRS)

Jackels, C. F.

1985-01-01

Accurate, ab initio quantum chemical techniques are applied in the present study of low lying bound and dissociative states of the methoxy radical at C3nu conformations, using a double zeta quality basis set that is augmented with polarization and diffuse functions. Excitation energy estimates are obtained for vertical excitation, vertical deexcitation, and system origin. The rate of methoxy photolysis is estimated to be too small to warrant its inclusion in atmospheric models.

Backbone resonance assignments for G protein α(i3) subunit in the GDP-bound state.

PubMed

Mase, Yoko; Yokogawa, Mariko; Osawa, Masanori; Shimada, Ichio

2014-10-01

Guanine-nucleotide binding proteins (G proteins) serve as molecular switches in signaling pathways, by coupling the activation of G protein-coupled receptors (GPCRs) at the cell surface to intracellular responses. In the resting state, G protein forms a heterotrimer, consisting of the G protein α subunit with GDP (Gα·GDP) and the G protein βγ subunit (Gβγ). Ligand binding to GPCRs promotes the GDP-GTP exchange on Gα, leading to the dissociation of the GTP-bound form of Gα (Gα·GTP) and Gβγ. Then, Gα·GTP and Gβγ bind to their downstream effector enzymes or ion channels and regulate their activities, leading to a variety of cellular responses. Finally, Gα hydrolyzes the bound GTP to GDP and returns to the resting state by re-associating with Gβγ. The G proteins are classified with four major families based on the amino acid sequences of Gα: i/o, s, q/11, and 12/13. Here, we established the backbone resonance assignments of human Gαi3, a member of the i/o family with a molecular weight of 41 K, in complex with GDP. The chemical shifts were compared with those of Gα(i3) in complex with a GTP-analogue, GTPγS, which we recently reported, indicating that the residues with significant chemical shift differences are mostly consistent with the regions with the structural differences between the GDP- and GTPγS-bound states, as indicated in the crystal structures. The assignments of Gα(i3)·GDP would be useful for the analyses of the dynamics of Gα(i3) and its interactions with various target molecules.

Exploring Photoinduced Excited State Evolution in Heterobimetallic Ru(II)-Co(III) Complexes.

PubMed

Kuhar, Korina; Fredin, Lisa A; Persson, Petter

2015-06-18

Quantum chemical calculations provide detailed theoretical information concerning key aspects of photoinduced electron and excitation transfer processes in supramolecular donor-acceptor systems, which are particularly relevant to fundamental charge separation in emerging molecular approaches for solar energy conversion. Here we use density functional theory (DFT) calculations to explore the excited state landscape of heterobimetallic Ru-Co systems with varying degrees of interaction between the two metal centers, unbound, weakly bound, and tightly bound systems. The interplay between structural and electronic factors involved in various excited state relaxation processes is examined through full optimizations of multiple charge/spin states of each of the investigated systems. Low-energy relaxed heterobimetallic states of energy transfer and excitation transfer character are characterized in terms of energy, structure, and electronic properties. These findings support the notion of efficient photoinduced charge separation from a Ru(II)-Co(III) ground state, via initial optical excitation of the Ru-center, to low-energy Ru(III)-Co(II) states. The strongly coupled system has significant involvement of the conjugated bridge, qualitatively distinguishing it from the other two weakly coupled systems. Finally, by constructing potential energy surfaces for the three systems where all charge/spin state combinations are projected onto relevant reaction coordinates, excited state decay pathways are explored.

Bound states in string nets

NASA Astrophysics Data System (ADS)

Schulz, Marc Daniel; Dusuel, Sébastien; Vidal, Julien

2016-11-01

We discuss the emergence of bound states in the low-energy spectrum of the string-net Hamiltonian in the presence of a string tension. In the ladder geometry, we show that a single bound state arises either for a finite tension or in the zero-tension limit depending on the theory considered. In the latter case, we perturbatively compute the binding energy as a function of the total quantum dimension. We also address this issue in the honeycomb lattice where the number of bound states in the topological phase depends on the total quantum dimension. Finally, the internal structure of these bound states is analyzed in the zero-tension limit.

Study of molecular N D bound states in the Bethe-Salpeter equation approach

NASA Astrophysics Data System (ADS)

Wang, Zhen-Yang; Qi, Jing-Juan; Guo, Xin-Heng; Wei, Ke-Wei

2018-05-01

We study the Λc(2595 )+ and Σc(2800 )0 states as the N D bound systems in the Bethe-Salpeter formalism in the ladder and instantaneous approximations. With the kernel induced by ρ , ω and σ exchanges, we solve the Bethe-Salpeter equations for the N D bound systems numerically and find that the bound states may exist. We assume that the observed states Λc(2595 )+ and Σc(2800 )0 are S -wave N D molecular bound states and calculate the decay widths of Λc(2595 )+→Σc0π+ and Σc(2800 )0→Λc+π-.

Distinguishing topological Majorana bound states from trivial Andreev bound states: Proposed tests through differential tunneling conductance spectroscopy

NASA Astrophysics Data System (ADS)

Liu, Chun-Xiao; Sau, Jay D.; Das Sarma, S.

2018-06-01

Trivial Andreev bound states arising from chemical-potential variations could lead to zero-bias tunneling conductance peaks at finite magnetic field in class-D nanowires, precisely mimicking the predicted zero-bias conductance peaks arising from the topological Majorana bound states. This finding raises a serious question on the efficacy of using zero-bias tunneling conductance peaks, by themselves, as evidence supporting the existence of topological Majorana bound states in nanowires. In the current work, we provide specific experimental protocols for tunneling spectroscopy measurements to distinguish between Andreev and Majorana bound states without invoking more demanding nonlocal measurements which have not yet been successfully performed in nanowire systems. In particular, we discuss three distinct experimental schemes involving the response of the zero-bias peak to local perturbations of the tunnel barrier, the overlap of bound states from the wire ends, and, most compellingly, introducing a sharp localized potential in the wire itself to perturb the zero-bias tunneling peaks. We provide extensive numerical simulations clarifying and supporting our theoretical predictions.

Microscopic observation of magnon bound states and their dynamics.

PubMed

Fukuhara, Takeshi; Schauß, Peter; Endres, Manuel; Hild, Sebastian; Cheneau, Marc; Bloch, Immanuel; Gross, Christian

2013-10-03

The existence of bound states of elementary spin waves (magnons) in one-dimensional quantum magnets was predicted almost 80 years ago. Identifying signatures of magnon bound states has so far remained the subject of intense theoretical research, and their detection has proved challenging for experiments. Ultracold atoms offer an ideal setting in which to find such bound states by tracking the spin dynamics with single-spin and single-site resolution following a local excitation. Here we use in situ correlation measurements to observe two-magnon bound states directly in a one-dimensional Heisenberg spin chain comprising ultracold bosonic atoms in an optical lattice. We observe the quantum dynamics of free and bound magnon states through time-resolved measurements of two spin impurities. The increased effective mass of the compound magnon state results in slower spin dynamics as compared to single-magnon excitations. We also determine the decay time of bound magnons, which is probably limited by scattering on thermal fluctuations in the system. Our results provide a new way of studying fundamental properties of quantum magnets and, more generally, properties of interacting impurities in quantum many-body 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

Disturbance observer-based adaptive sliding mode hybrid projective synchronisation of identical fractional-order financial systems

NASA Astrophysics Data System (ADS)

Khan, Ayub; Tyagi, Arti

2018-05-01

In this paper, we have studied the hybrid projective synchronisation for incommensurate, integer and commensurate fractional-order financial systems with unknown disturbance. To tackle the problem of unknown bounded disturbance, fractional-order disturbance observer is designed to approximate the unknown disturbance. Further, we have introduced simple sliding mode surface and designed adaptive sliding mode controllers incorporating with the designed fractional-order disturbance observer to achieve a bounded hybrid projective synchronisation between two identical fractional-order financial model with different initial conditions. It is shown that the slave system with disturbance can be synchronised with the projection of the master system generated through state transformation. Simulation results are presented to ensure the validity and effectiveness of the proposed sliding mode control scheme in the presence of external bounded unknown disturbance. Also, synchronisation error for commensurate, integer and incommensurate fractional-order financial systems is studied in numerical simulation.

Generation of bound states of pulses in a SESAM mode-locked Cr:ZnSe laser

NASA Astrophysics Data System (ADS)

Bu, Xiangbao; Shi, Yuhang; Xu, Jia; Li, Huijuan; Wang, Pu

2018-06-01

We report on the generation of bound states of pulses in a SESAM mode-locked Cr:ZnSe laser around 2415 nm. A thulium-doped double-clad fiber laser at 1908 nm was used as the pump source. Bound states with various pulse separations at different dispersion regimes were obtained. Especially, in the anomalous dispersion regime, vibrating bound state of solitons exhibiting an evolving phase was obtained.

Bound entangled states with a private key and their classical counterpart.

PubMed

Ozols, Maris; Smith, Graeme; Smolin, John A

2014-03-21

Entanglement is a fundamental resource for quantum information processing. In its pure form, it allows quantum teleportation and sharing classical secrets. Realistic quantum states are noisy and their usefulness is only partially understood. Bound-entangled states are central to this question--they have no distillable entanglement, yet sometimes still have a private classical key. We present a construction of bound-entangled states with a private key based on classical probability distributions. From this emerge states possessing a new classical analogue of bound entanglement, distinct from the long-sought bound information. We also find states of smaller dimensions and higher key rates than previously known. Our construction has implications for classical cryptography: we show that existing protocols are insufficient for extracting private key from our distributions due to their "bound-entangled" nature. We propose a simple extension of existing protocols that can extract a key from them.

Scattering of particles in the presence of harmonic confinement perturbed by a complex absorbing potential

NASA Astrophysics Data System (ADS)

Maghari, A.; Kermani, M. M.

2018-04-01

A system of two interacting atoms confined in 1D harmonic trap and perturbed by an absorbing boundary potential is studied using the Lippmann-Schwinger formalism. The atom-atom interaction potential was considered as a nonlocal separable model. The perturbed absorbing boundary potential was also assumed in the form of Scarf II complex absorbing potential. The model is used for the study of 1D optical lattices that support the trapping of a pair atom within a unit cell. Moreover, it allows to describe the scattering particles in a tight smooth trapping surface and to analyze the bound and resonance states. The analytical expressions for wavefunctions and transition matrix as well as the absorption probabilities are calculated. A demonstration of how the complex absorbing potential affecting the bound states and resonances of particles confined in a harmonic trap is described.

Scanning Tunneling Microscopy Observation of Phonon Condensate

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

Altfeder, Igor; Balatsky, Alexander V.; Voevodin, Andrey A.

Using quantum tunneling of electrons into vibrating surface atoms, phonon oscillations can be observed on the atomic scale. Phonon interference patterns with unusually large signal amplitudes have been revealed by scanning tunneling microscopy in intercalated van der Waals heterostructures. Our results show that the effective radius of these phonon quasi-bound states, the real-space distribution of phonon standing wave amplitudes, the scattering phase shifts, and the nonlinear intermode coupling strongly depend on the presence of defect-induced scattering resonance. The observed coherence of these quasi-bound states most likely arises from phase- and frequency-synchronized dynamics of all phonon modes, and indicates the formationmore » of many-body condensate of optical phonons around resonant defects. We found that increasing the strength of the scattering resonance causes the increase of the condensate droplet radius without affecting the condensate fraction inside it. The condensate can be observed at room temperature.« less

Scanning Tunneling Microscopy Observation of Phonon Condensate

PubMed Central

Altfeder, Igor; Voevodin, Andrey A.; Check, Michael H.; Eichfeld, Sarah M.; Robinson, Joshua A.; Balatsky, Alexander V.

2017-01-01

Using quantum tunneling of electrons into vibrating surface atoms, phonon oscillations can be observed on the atomic scale. Phonon interference patterns with unusually large signal amplitudes have been revealed by scanning tunneling microscopy in intercalated van der Waals heterostructures. Our results show that the effective radius of these phonon quasi-bound states, the real-space distribution of phonon standing wave amplitudes, the scattering phase shifts, and the nonlinear intermode coupling strongly depend on the presence of defect-induced scattering resonance. The observed coherence of these quasi-bound states most likely arises from phase- and frequency-synchronized dynamics of all phonon modes, and indicates the formation of many-body condensate of optical phonons around resonant defects. We found that increasing the strength of the scattering resonance causes the increase of the condensate droplet radius without affecting the condensate fraction inside it. The condensate can be observed at room temperature. PMID:28225066

Scanning Tunneling Microscopy Observation of Phonon Condensate

DOE PAGES

Altfeder, Igor; Balatsky, Alexander V.; Voevodin, Andrey A.; ...

2017-02-22

Using quantum tunneling of electrons into vibrating surface atoms, phonon oscillations can be observed on the atomic scale. Phonon interference patterns with unusually large signal amplitudes have been revealed by scanning tunneling microscopy in intercalated van der Waals heterostructures. Our results show that the effective radius of these phonon quasi-bound states, the real-space distribution of phonon standing wave amplitudes, the scattering phase shifts, and the nonlinear intermode coupling strongly depend on the presence of defect-induced scattering resonance. The observed coherence of these quasi-bound states most likely arises from phase- and frequency-synchronized dynamics of all phonon modes, and indicates the formationmore » of many-body condensate of optical phonons around resonant defects. We found that increasing the strength of the scattering resonance causes the increase of the condensate droplet radius without affecting the condensate fraction inside it. The condensate can be observed at room temperature.« less

77 FR 31830 - Opportunity for Designation in the West Sacramento, CA; Frankfort, IN; Indianapolis, IN; and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-30

... eastern California State line; Bounded on the East by the eastern California State line south to the... lines west to the western California State line; and Bounded on the West by the western California State...; Bounded on the East by the eastern Fulton County line south to State Route 19; State Route 19 south to...

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

Krotov, V.V.; Staroverov, S.M.; Nesterenko, P.N.

A series of heterogeneous catalysts for asymmetric Michael additions was synthesized based on ephedrine chemically bound to the surface of silica. The length of the hydrocarbon chain binding the active center to the support surface affects the sign of rotation of the reaction product from the asymmetric addition of thiophenol to benzylideneacetophenone. Grafting ephedrine to the silica surface via a short hydrocarbon chain results in a change in the configuration of the reaction product. Silanol groups on the silica surface are involved in the transition state, as evidenced by data obtained using silica which has been exhaustively treated with trimethylchlorosilane.more » The absolute specific rotation of 1,3-diphenyl-3-thiophenylpropan-1-one has been established.« less

Investigation of Positron Sticking to the Surfaces of Topological Insulators

NASA Astrophysics Data System (ADS)

Shastry, K.; Joglekar, P. V.; Olenga, A. Y.; Fazleev, N. G.; Weiss, A. H.; Barniellini, B.

2013-03-01

We describe experiments aimed at probing the sticking of positrons to the surfaces of topological insulators. In these experiments, a magnetically beam will be used to deposit positrons at the surface of Bi2Te2Se. The energy spectra and intensities of electrons emitted as a result of Positron Annihilation induced Auger electron Spectroscopy (PAES) provides a distinct element specific signal which can be used to determine if positrons can be trapped efficiently into a surface localized bound state. The experiments are aimed at determining the practicality of using positron annihilation to selectively probe the critically important top most layer of topological insulator system. Welch Y1100, NSF DMR 0907679

Using Computational Fluid Dynamics to Compare Shear Rate and Turbulence in the TIM-Automated Gastric Compartment With USP Apparatus II.

PubMed

Hopgood, Matthew; Reynolds, Gavin; Barker, Richard

2018-03-30

We use computational fluid dynamics to compare the shear rate and turbulence in an advanced in vitro gastric model (TIMagc) during its simulation of fasted state Migrating Motor Complex phases I and II, with the United States Pharmacopeia paddle dissolution apparatus II (USPII). A specific focus is placed on how shear rate in these apparatus affects erosion-based solid oral dosage forms. The study finds that tablet surface shear rates in TIMagc are strongly time dependant and fluctuate between 0.001 and 360 s -1 . In USPII, tablet surface shear rates are approximately constant for a given paddle speed and increase linearly from 9 s -1 to 36 s -1 as the paddle speed is increased from 25 to 100 rpm. A strong linear relationship is observed between tablet surface shear rate and tablet erosion rate in USPII, whereas TIMagc shows highly variable behavior. The flow regimes present in each apparatus are compared to in vivo predictions using Reynolds number analysis. Reynolds numbers for flow in TIMagc lie predominantly within the predicted in vivo bounds (0.01-30), whereas Reynolds numbers for flow in USPII lie above the predicted upper bound when operating with paddle speeds as low as 25 rpm (33). Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

RNA binding to APOBEC3G induces the disassembly of functional deaminase complexes by displacing single-stranded DNA substrates

PubMed Central

Polevoda, Bogdan; McDougall, William M.; Tun, Bradley N.; Cheung, Michael; Salter, Jason D.; Friedman, Alan E.; Smith, Harold C.

2015-01-01

APOBEC3G (A3G) DNA deaminase activity requires a holoenzyme complex whose assembly on nascent viral reverse transcripts initiates with A3G dimers binding to ssDNA followed by formation of higher-order A3G homo oligomers. Catalytic activity is inhibited when A3G binds to RNA. Our prior studies suggested that RNA inhibited A3G binding to ssDNA. In this report, near equilibrium binding and gel shift analyses showed that A3G assembly and disassembly on ssDNA was an ordered process involving A3G dimers and multimers thereof. Although, fluorescence anisotropy showed that A3G had similar nanomolar affinity for RNA and ssDNA, RNA stochastically dissociated A3G dimers and higher-order oligomers from ssDNA, suggesting a different modality for RNA binding. Mass spectrometry mapping of A3G peptides cross-linked to nucleic acid suggested ssDNA only bound to three peptides, amino acids (aa) 181–194 in the N-terminus and aa 314–320 and 345–374 in the C-terminus that were part of a continuous exposed surface. RNA bound to these peptides and uniquely associated with three additional peptides in the N- terminus, aa 15–29, 41–52 and 83–99, that formed a continuous surface area adjacent to the ssDNA binding surface. The data predict a mechanistic model of RNA inhibition of ssDNA binding to A3G in which competitive and allosteric interactions determine RNA-bound versus ssDNA-bound conformational states. PMID:26424853

Backward propagating branch of surface waves in a semi-bounded streaming plasma system

NASA Astrophysics Data System (ADS)

Lim, Young Kyung; Lee, Myoung-Jae; Seo, Ki Wan; Jung, Young-Dae

2017-06-01

The influence of wake and magnetic field on the surface ion-cyclotron wave is kinetically investigated in a semi-bounded streaming dusty magnetoplasma in the presence of the ion wake-field. The analytic expressions of the frequency and the group velocity are derived by the plasma dielectric function with the spectral reflection condition. The result shows that the ion wake-field enhances the wave frequency and the group velocity of the surface ion-cyclotron wave in a semi-bounded dusty plasma. It is found that the frequency and the group velocity of the surface electrostatic-ion-cyclotron wave increase with an increase of the strength of the magnetic field. It is interesting to find out that the group velocity without the ion flow has the backward propagation mode in a semi-bounded dusty plasma. The variations due to the frequency and the group velocity of the surface ion-cyclotron wave are also discussed.

The Bound to Bound State Contribution to the Electric Polarizability of a Relativbistic Particle

NASA Astrophysics Data System (ADS)

Vidnovic, Theodore, III; Anis Maize, Mohamed

1998-04-01

We calculate, in our study, the contribution of the transition between bound energy states to the electric polarizability of a relativistic particle. The particle is moving under the influence of a one-dimensional delta potential. Our work is done in the case of the scalar potential. The solution of Dirac's equation and the calculation of the particles total electric polarizability has been done in references (1-3). The transitions contributing to the electric polarizability are: Continuum to continuum, bound to bound, negative energy bound states to continuum, and positive energy bound states to continuum. Our task is to study the bound to bound state contribution to the electric polarizability. We will also investigate the effect of the strength of the potential on the contribution. 1. T.H. Solomon and S. Fallieros, "Relativistic One Dimensional Binding and Two Dimensional Motion." J. Franklin Inst. 320, 323-344 (1985) 2. M.A. Maize and C.A. Burkholder, "Electric Polarizability and the Solution of an Inhomogenous Differential Equation." Am.J.Phys. 63, 244-247 (1995) 3. M.A. Maize, S. Paulson, and A. D'Avanti, "Electric Polarizability of a Relativistic Particle." Am.J.Phys. 65, 888-892 (1997)

Group IV nanocrystals with ion-exchangeable surface ligands and methods of making the same

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

Wheeler, Lance M.; Nichols, Asa W.; Chernomordik, Boris D.

Methods are described that include reacting a starting nanocrystal that includes a starting nanocrystal core and a covalently bound surface species to create an ion-exchangeable (IE) nanocrystal that includes a surface charge and a first ion-exchangeable (IE) surface ligand ionically bound to the surface charge, where the starting nanocrystal core includes a group IV element.

Distinguishing Majorana bound states and Andreev bound states with microwave spectra

NASA Astrophysics Data System (ADS)

Zhang, Zhen-Tao

2018-04-01

Majorana fermions are a fascinating and not yet confirmed quasiparticles in condensed matter physics. Here we propose using microwave spectra to distinguish Majorana bound states (MBSs) from topological trivial Andreev bound states. By numerically calculating the transmission and Zeeman field dependence of the many-body excitation spectrum of a 1D Josephson junction, we find that the two kinds of bound states have distinct responses to variations in the related parameters. Furthermore, the singular behaviors of the MBSs spectrum could be attributed to the robust fractional Josephson coupling and nonlocality of MBSs. Our results provide a feasible method to verify the existence of MBSs and could accelerate its application to topological quantum computation.

Ultrafast Imaging of Surface Plasmons Propagating on a Gold Surface

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

Gong, Yu; Joly, Alan G.; Hu, Dehong

2015-05-13

We record time-resolved nonlinear photoemission electron microscopy (tr-PEEM) images of propagating surface plasmons (PSPs) launched from a lithographically patterned rectangular trench on a flat gold surface. Our tr-PEEM scheme involves a pair of identical, spatially separated, and interferometrically-locked femtosecond laser pulses. Power dependent PEEM images provide experimental evidence for a sequential coherent nonlinear photoemission process, in which one laser source creates a PSP polarization state through a linear interaction, and the second subsequently probes the prepared state via two photon photoemission. The recorded time-resolved movies of a PSP allow us to directly measure various properties of the surface-bound wave packet,more » including its carrier wavelength (785 nm) and group velocity (0.95c). In addition, tr-PEEM in concert with finite-difference time domain simulations together allow us to set a lower limit of 75 μm for the decay length of the PSP on a 100 nm thick gold film.« less

Localized versus itinerant states created by multiple oxygen vacancies in SrTiO3

NASA Astrophysics Data System (ADS)

Jeschke, Harald O.; Shen, Juan; Valentí, Roser

2015-02-01

Oxygen vacancies in strontium titanate surfaces (SrTiO3) have been linked to the presence of a two-dimensional electron gas with unique behavior. We perform a detailed density functional theory study of the lattice and electronic structure of SrTiO3 slabs with multiple oxygen vacancies, with a main focus on two vacancies near a titanium dioxide terminated SrTiO3 surface. We conclude based on total energies that the two vacancies preferably inhabit the first two layers, i.e. they cluster vertically, while in the direction parallel to the surface, the vacancies show a weak tendency towards equal spacing. Analysis of the nonmagnetic electronic structure indicates that oxygen defects in the surface TiO2 layer lead to population of Ti {{t}2g} states and thus itinerancy of the electrons donated by the oxygen vacancy. In contrast, electrons from subsurface oxygen vacancies populate Ti eg states and remain localized on the two Ti ions neighboring the vacancy. We find that both the formation of a bound oxygen-vacancy state composed of hybridized Ti 3eg and 4p states neighboring the oxygen vacancy as well as the elastic deformation after extracting oxygen contribute to the stabilization of the in-gap state.

The upper bounds of reduced axial and shear moduli in cross-ply laminates with matrix cracks

NASA Technical Reports Server (NTRS)

Lee, Jong-Won; Allen, D. H.; Harris, C. E.

1991-01-01

The present study proposes a mathematical model utilizing the internal state variable concept for predicting the upper bounds of the reduced axial and shear stiffnesses in cross-ply laminates with matrix cracks. The displacement components at the matrix crack surfaces are explicitly expressed in terms of the observable axial and shear strains and the undamaged material properties. The reduced axial and shear stiffnesses are predicted for glass/epoxy and graphite/epoxy laminates. Comparison of the model with other theoretical and experimental studies is also presented to confirm direct applicability of the model to angle-ply laminates with matrix cracks subjected to general in-plane loading.

Designing Quantum Spin-Orbital Liquids in Artificial Mott Insulators

DOE PAGES

Dou, Xu; Kotov, Valeri N.; Uchoa, Bruno

2016-08-24

Quantum spin-orbital liquids are elusive strongly correlated states of matter that emerge from quantum frustration between spin and orbital degrees of freedom. A promising route towards the observation of those states is the creation of artificial Mott insulators where antiferromagnetic correlations between spins and orbitals can be designed. We show that Coulomb impurity lattices on the surface of gapped honeycomb substrates, such as graphene on SiC, can be used to simulate SU(4) symmetric spin-orbital lattice models. We exploit the property that massive Dirac fermions form mid-gap bound states with spin and valley degeneracies in the vicinity of a Coulomb impurity.more » Due to electronic repulsion, the antiferromagnetic correlations of the impurity lattice are driven by a super-exchange interaction with SU(4) symmetry, which emerges from the bound states degeneracy at quarter filling. We propose that quantum spin-orbital liquids can be engineered in artificially designed solid-state systems at vastly higher temperatures than achievable in optical lattices with cold atoms. Lastly, we discuss the experimental setup and possible scenarios for candidate quantum spin-liquids in Coulomb impurity lattices of various geometries.« less

Numerical Implementation of the Cohesive Soil Bounding Surface Plasticity Model. Volume I.

DTIC Science & Technology

1983-02-01

AD-R24 866 NUMERICAL IMPLEMENTATION OF THE COHESIVE SOIL BOUNDING 1/2 SURFACE PLASTICITY ..(U) CALIFORNIA UNIV DAVIS DEPT OF CIVIL ENGINEERING L R...a study of various numerical means for implementing the bounding surface plasticity model for cohesive soils is presented. A comparison is made of... Plasticity Models 17 3.4 Selection Of Methods For Comparison 17 3.5 Theory 20 3.5.1 Solution Methods 20 3.5.2 Reduction Of The Number Of Equation

Symmetry Parameter Constraints from a Lower Bound on Neutron-matter Energy

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

Tews, Ingo; Lattimer, James M.; Ohnishi, Akira

We propose the existence of a lower bound on the energy of pure neutron matter (PNM) on the basis of unitary-gas considerations. We discuss its justification from experimental studies of cold atoms as well as from theoretical studies of neutron matter. We demonstrate that this bound results in limits to the density-dependent symmetry energy, which is the difference between the energies of symmetric nuclear matter and PNM. In particular, this bound leads to a lower limit to the volume symmetry energy parameter S {sub 0}. In addition, for assumed values of S {sub 0} above this minimum, this bound impliesmore » both upper and lower limits to the symmetry energy slope parameter L , which describes the lowest-order density dependence of the symmetry energy. A lower bound on neutron-matter incompressibility is also obtained. These bounds are found to be consistent with both recent calculations of the energies of PNM and constraints from nuclear experiments. Our results are significant because several equations of state that are currently used in astrophysical simulations of supernovae and neutron star mergers, as well as in nuclear physics simulations of heavy-ion collisions, have symmetry energy parameters that violate these bounds. Furthermore, below the nuclear saturation density, the bound on neutron-matter energies leads to a lower limit to the density-dependent symmetry energy, which leads to upper limits to the nuclear surface symmetry parameter and the neutron-star crust–core boundary. We also obtain a lower limit to the neutron-skin thicknesses of neutron-rich nuclei. Above the nuclear saturation density, the bound on neutron-matter energies also leads to an upper limit to the symmetry energy, with implications for neutron-star cooling via the direct Urca process.« less

Symmetry Parameter Constraints from a Lower Bound on Neutron-matter Energy

NASA Astrophysics Data System (ADS)

Tews, Ingo; Lattimer, James M.; Ohnishi, Akira; Kolomeitsev, Evgeni E.

2017-10-01

We propose the existence of a lower bound on the energy of pure neutron matter (PNM) on the basis of unitary-gas considerations. We discuss its justification from experimental studies of cold atoms as well as from theoretical studies of neutron matter. We demonstrate that this bound results in limits to the density-dependent symmetry energy, which is the difference between the energies of symmetric nuclear matter and PNM. In particular, this bound leads to a lower limit to the volume symmetry energy parameter S 0. In addition, for assumed values of S 0 above this minimum, this bound implies both upper and lower limits to the symmetry energy slope parameter L ,which describes the lowest-order density dependence of the symmetry energy. A lower bound on neutron-matter incompressibility is also obtained. These bounds are found to be consistent with both recent calculations of the energies of PNM and constraints from nuclear experiments. Our results are significant because several equations of state that are currently used in astrophysical simulations of supernovae and neutron star mergers, as well as in nuclear physics simulations of heavy-ion collisions, have symmetry energy parameters that violate these bounds. Furthermore, below the nuclear saturation density, the bound on neutron-matter energies leads to a lower limit to the density-dependent symmetry energy, which leads to upper limits to the nuclear surface symmetry parameter and the neutron-star crust-core boundary. We also obtain a lower limit to the neutron-skin thicknesses of neutron-rich nuclei. Above the nuclear saturation density, the bound on neutron-matter energies also leads to an upper limit to the symmetry energy, with implications for neutron-star cooling via the direct Urca process.

Stationary and oscillatory bound states of dissipative solitons created by third-order dispersion

NASA Astrophysics Data System (ADS)

Sakaguchi, Hidetsugu; Skryabin, Dmitry V.; Malomed, Boris A.

2018-06-01

We consider the model of fiber-laser cavities near the zero-dispersion point, based on the complex Ginzburg-Landau equation with the cubic-quintic nonlinearity, including the third-order dispersion (TOD) term. It is well known that this model supports stable dissipative solitons. We demonstrate that the same model gives rise to several families of robust bound states of the solitons, which exists only in the presence of the TOD. There are both stationary and dynamical bound states, with oscillating separation between the bound solitons. Stationary states are multistable, corresponding to different values of the separation. With the increase of the TOD coefficient, the bound state with the smallest separation gives rise the oscillatory state through the Hopf bifurcation. Further growth of TOD leads to a bifurcation transforming the oscillatory limit cycle into a strange attractor, which represents a chaotically oscillating dynamical bound state. Families of multistable three- and four-soliton complexes are found too, the ones with the smallest separation between the solitons again ending by a transition to oscillatory states through the Hopf bifurcation.

Impurity bound states in d-wave superconductors with subdominant order parameters

NASA Astrophysics Data System (ADS)

Mashkoori, Mahdi; Björnson, Kristofer; Black-Schaffer, Annica

Single magnetic impurity induces intra-gap bound states in conventional s-wave superconductors (SCs) but, in d-wave SCs only virtual bound states can be induced. However, in small cuprate islands a fully gapped spectrum has recently been discovered. In this work, we investigate the real bound states due to potential and magnetic impurities in the two candidate fully gapped states for this system: the topologically trivial d + is -wave state and the topologically non-trivial d + id' -wave (chiral d-wave state). Using the analytic T-matrix formalism and self-consistent numerical tight-binding lattice calculations, we show that potential and magnetic impurities create entirely different intra-gap bound states in d + is -wave and chiral d-wave SCs. Therefore, our results suggest that the bound states mainly depend on the subdominant order parameter. Considering that recent experiments have demonstrated an access to adjustable coupling J, impurities thus offer an intriguing way to clearly distinguish between the chiral d-wave and topologically trivial d + is -wave state. This work was supported by Swedish Research Council, Swedish Foundation for Strategic Research, the Wallenberg Academy Fellows program and the Göran Gustafsson Foundation. The computations were performed on resources provided by SNIC at LUNARC.

Bound state potential energy surface construction: ab initio zero-point energies and vibrationally averaged rotational constants.

PubMed

Bettens, Ryan P A

2003-01-15

Collins' method of interpolating a potential energy surface (PES) from quantum chemical calculations for reactive systems (Jordan, M. J. T.; Thompson, K. C.; Collins, M. A. J. Chem. Phys. 1995, 102, 5647. Thompson, K. C.; Jordan, M. J. T.; Collins, M. A. J. Chem. Phys. 1998, 108, 8302. Bettens, R. P. A.; Collins, M. A. J. Chem. Phys. 1999, 111, 816) has been applied to a bound state problem. The interpolation method has been combined for the first time with quantum diffusion Monte Carlo calculations to obtain an accurate ground state zero-point energy, the vibrationally average rotational constants, and the vibrationally averaged internal coordinates. In particular, the system studied was fluoromethane using a composite method approximating the QCISD(T)/6-311++G(2df,2p) level of theory. The approach adopted in this work (a) is fully automated, (b) is fully ab initio, (c) includes all nine nuclear degrees of freedom, (d) requires no assumption of the functional form of the PES, (e) possesses the full symmetry of the system, (f) does not involve fitting any parameters of any kind, and (g) is generally applicable to any system amenable to quantum chemical calculations and Collins' interpolation method. The calculated zero-point energy agrees to within 0.2% of its current best estimate. A0 and B0 are within 0.9 and 0.3%, respectively, of experiment.

The Surface Chemistry of Metal Chalcogenide Nanocrystals

NASA Astrophysics Data System (ADS)

Anderson, Nicholas Charles

The surface chemistry of metal chalcogenide nanocrystals is explored through several interrelated analytical investigations. After a brief discussion of the nanocrystal history and applications, molecular orbital theory is used to describe the electronic properties of semiconductors, and how these materials behave on the nanoscale. Quantum confinement plays a major role in dictating the optical properties of metal chalcogenide nanocrystals, however surface states also have an equally significant contribution to the electronic properties of nanocrystals due to the high surface area to volume ratio of nanoscale semiconductors. Controlling surface chemistry is essential to functionalizing these materials for biological imaging and photovoltaic device applications. To better understand the surface chemistry of semiconducting nanocrystals, three competing surface chemistry models are presented: 1.) The TOPO model, 2.) the Non-stoichiometric model, and 3.) the Neutral Fragment model. Both the non-stoichiometric and neutral fragment models accurately describe the behavior of metal chalcogenide nanocrystals. These models rely on the covalent bond classification system, which divides ligands into three classes: 1.) X-type, 1-electron donating ligands that balance charge with excess metal at the nanocrystal surface, 2.) L-type, 2-electron donors that bind metal sites, and 3.) Z-type, 2-electron acceptors that bind chalcogenide sites. Each of these ligand classes is explored in detail to better understand the surface chemistry of metal chalcogenide nanocrystals. First, chloride-terminated, tri-n-butylphosphine (Bu 3P) bound CdSe nanocrystals were prepared by cleaving carboxylate ligands from CdSe nanocrystals with chlorotrimethylsilane in Bu3P solution. 1H and 31P{1H} nuclear magnetic resonance spectra of the isolated nanocrystals allowed assignment of distinct signals from several free and bound species, including surface-bound Bu3P and [Bu3P-H]+[Cl]- ligands as well as a Bu3P complex of cadmium chloride. Nuclear magnetic resonance spectroscopy supports complete cleavage of the X-type carboxylate ligands. Combined with measurements of the Se:Cd:Cl ratio using Rutherford backscattering spectrometry, these studies support a structural model of nanocrystals where chloride ligands terminate the crystal lattice by balancing the charges of excess Cd2+ ions. The adsorption of dative phosphine ligands leads to nanocrystals who's solubility is afforded by reversibly bound and readily exchanged L-type ligands, e.g. primary amines and phosphines. The other halides (Br and I) can also be used to prepare Bu 3P-bound, halide-terminated CdSe nanocrystals, however these nanocrystals are not soluble after exchange. The change in binding affinity of Bu 3P over the halide series is briefly discussed. Next, we report a series of L-type ligand exchanges using Bu3P-bound, chloride-terminated CdSe nanocrystals with several Lewis bases, including aromatic, cyclic, and non-cyclic sulfides, and ethers; primary, secondary, and tertiary amines and phosphines; tertiary phosphine chalcogenides; primary alcohols, isocyanides, and isothiocyanides. Using 31P nuclear magnetic resonance spectroscopy, we establish a relative binding affinity for these ligands that reflects electronic considerations but is dominated primarily by steric interactions, as determined by comparing binding affinity to Tolmann cone angles. We also used chloride-terminated CdSe nanocrystals to explore the reactivity of ionic salts at nanocrystal surfaces. These salts, particularly [Bu3P-H]+[Cl]-, bind nanocrystals surfaces as L-type ligands, making them soluble in polar solvents such as acetonitrile. This information should provide insight for rational ligand design for future applications involving metal chalcogenide nanocrystals. The strongest ligand, primary n-alkylamine, rapidly displace the Bu3P from halide-terminated CdSe nanocrystals, leading to amine-bound nanocrystals with higher dative ligand coverages and greatly increased photoluminescence quantum yields. The importance of ligand coverage to both the UV-visible absorption and photoluminescence spectra are discussed. (Abstract shortened by UMI.).

Topological Defects in Topological Insulators and Bound States at Topological Superconductor Vortices

PubMed Central

Parente, Vincenzo; Campagnano, Gabriele; Giuliano, Domenico; Tagliacozzo, Arturo; Guinea, Francisco

2014-01-01

The scattering of Dirac electrons by topological defects could be one of the most relevant sources of resistance in graphene and at the boundary surfaces of a three-dimensional topological insulator (3D TI). In the long wavelength, continuous limit of the Dirac equation, the topological defect can be described as a distortion of the metric in curved space, which can be accounted for by a rotation of the Gamma matrices and by a spin connection inherited with the curvature. These features modify the scattering properties of the carriers. We discuss the self-energy of defect formation with this approach and the electron cross-section for intra-valley scattering at an edge dislocation in graphene, including corrections coming from the local stress. The cross-section contribution to the resistivity, ρ, is derived within the Boltzmann theory of transport. On the same lines, we discuss the scattering of a screw dislocation in a two-band 3D TI, like Bi1−xSbx, and we present the analytical simplified form of the wavefunction for gapless helical states bound at the defect. When a 3D TI is sandwiched between two even-parity superconductors, Dirac boundary states acquire superconductive correlations by proximity. In the presence of a magnetic vortex piercing the heterostructure, two Majorana states are localized at the two interfaces and bound to the vortex core. They have a half integer total angular momentum each, to match with the unitary orbital angular momentum of the vortex charge. PMID:28788537

Topological Defects in Topological Insulators and Bound States at Topological Superconductor Vortices.

PubMed

Parente, Vincenzo; Campagnano, Gabriele; Giuliano, Domenico; Tagliacozzo, Arturo; Guinea, Francisco

2014-03-04

The scattering of Dirac electrons by topological defects could be one of the most relevant sources of resistance in graphene and at the boundary surfaces of a three-dimensional topological insulator (3D TI). In the long wavelength, continuous limit of the Dirac equation, the topological defect can be described as a distortion of the metric in curved space, which can be accounted for by a rotation of the Gamma matrices and by a spin connection inherited with the curvature. These features modify the scattering properties of the carriers. We discuss the self-energy of defect formation with this approach and the electron cross-section for intra-valley scattering at an edge dislocation in graphene, including corrections coming from the local stress. The cross-section contribution to the resistivity, ρ, is derived within the Boltzmann theory of transport. On the same lines, we discuss the scattering of a screw dislocation in a two-band 3D TI, like Bi 1-x Sb x , and we present the analytical simplified form of the wavefunction for gapless helical states bound at the defect. When a 3D TI is sandwiched between two even-parity superconductors, Dirac boundary states acquire superconductive correlations by proximity. In the presence of a magnetic vortex piercing the heterostructure, two Majorana states are localized at the two interfaces and bound to the vortex core. They have a half integer total angular momentum each, to match with the unitary orbital angular momentum of the vortex charge.

Tuning Confinement in Colloidal Silicon Nanocrystals with Saturated Surface Ligands.

PubMed

Carroll, Gerard M; Limpens, Rens; Neale, Nathan R

2018-05-09

The optical properties of silicon nanocrystals (Si NCs) are a subject of intense study and continued debate. In particular, Si NC photoluminescence (PL) properties are known to depend strongly on the surface chemistry, resulting in electron-hole recombination pathways derived from the Si NC band-edge, surface-state defects, or combined NC-conjugated ligand hybrid states. In this Letter, we perform a comparison of three different saturated surface functional groups-alkyls, amides, and alkoxides-on nonthermal plasma-synthesized Si NCs. We find a systematic and size-dependent high-energy (blue) shift in the PL spectrum of Si NCs with amide and alkoxy functionalization relative to alkyl. Time-resolved photoluminescence and transient absorption spectroscopies reveal no change in the excited-state dynamics between Si NCs functionalized with alkyl, amide, or alkoxide ligands, showing for the first time that saturated ligands-not only surface-derived charge-transfer states or hybridization between NC and low-lying ligand orbitals-are responsible for tuning the Si NC optical properties. To explain these PL shifts we propose that the atom bound to the Si NC surface strongly interacts with the Si NC electronic wave function and modulates the Si NC quantum confinement. These results reveal a potentially broadly applicable correlation between the optoelectronic properties of Si NCs and related quantum-confined structures based on the interaction between NC surfaces and the ligand binding group.

Tuning Confinement in Colloidal Silicon Nanocrystals with Saturated Surface Ligands

DOE PAGES

Carroll, Gerard M.; Limpens, Rens; Neale, Nathan R.

2018-04-16

The optical properties of silicon nanocrystals (Si NCs) are a subject of intense study and continued debate. In particular, Si NC photoluminescence (PL) properties are known to depend strongly on the surface chemistry, resulting in electron-hole recombination pathways derived from the Si NC band-edge, surface-state defects, or combined NC-conjugated ligand hybrid states. In this Letter, we perform a comparison of three different saturated surface functional groups - alkyls, amides, and alkoxides - on nonthermal plasma-synthesized Si NCs. We find a systematic and size-dependent high-energy (blue) shift in the PL spectrum of Si NCs with amide and alkoxy functionalization relative tomore » alkyl. Time-resolved photoluminescence and transient absorption spectroscopies reveal no change in the excited-state dynamics between Si NCs functionalized with alkyl, amide, or alkoxide ligands, showing for the first time that saturated ligands - not only surface-derived charge-transfer states or hybridization between NC and low-lying ligand orbitals - are responsible for tuning the Si NC optical properties. To explain these PL shifts we propose that the atom bound to the Si NC surface strongly interacts with the Si NC electronic wave function and modulates the Si NC quantum confinement. Furthermore, these results reveal a potentially broadly applicable correlation between the optoelectronic properties of Si NCs and related quantum-confined structures based on the interaction between NC surfaces and the ligand binding group.« less

Electron teleportation via Majorana bound states in a mesoscopic superconductor.

PubMed

Fu, Liang

2010-02-05

Zero-energy Majorana bound states in superconductors have been proposed to be potential building blocks of a topological quantum computer, because quantum information can be encoded nonlocally in the fermion occupation of a pair of spatially separated Majorana bound states. However, despite intensive efforts, nonlocal signatures of Majorana bound states have not been found in charge transport. In this work, we predict a striking nonlocal phase-coherent electron transfer process by virtue of tunneling in and out of a pair of Majorana bound states. This teleportation phenomenon only exists in a mesoscopic superconductor because of an all-important but previously overlooked charging energy. We propose an experimental setup to detect this phenomenon in a superconductor-quantum-spin-Hall-insulator-magnetic-insulator hybrid system.

Ab initio study of the ground and excited electronic states of the methyl radical

PubMed Central

Zanchet, A.; Bañares, L.; Senent, M. L.; García-Vela, A.

2016-01-01

The ground and some excited electronic states of the methyl radical have been characterized by means of highly correlated ab intio techniques. The specific excited states investigated are those involved in the dissociation of the radical, namely the 3s and 3pz Rydberg states, and the A1 and B1 valence states crossing them, respectively. The C-H dissociative coordinate and the HCH bending angle were considered in order to generate the first two-dimensional ab initio representation of the potential surfaces of the above electronic states of CH3, along with the nonadiabatic couplings between them. Spectroscopic constants and frequencies calculated for the ground and bound excited states agree well with most of the available experimental data. Implications of the shape of the excited potential surfaces and couplings for the dissociation pathways of CH3 are discussed in the light of recent experimental results for dissociation from low-lying vibrational states of CH3. Based on the ab initio data some predictions are made regarding methyl photodissociation from higher initial vibrational states. PMID:27892569

Time of flight spectrometer for background-free positron annihilation induced Auger electron spectroscopy

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

Mukherjee, S.; Shastry, K.; Anto, C. V.

2016-03-15

We describe a novel spectrometer designed for positron annihilation induced Auger electron spectroscopy employing a time-of-flight spectrometer. The spectrometer’s new configuration enables us to implant monoenergetic positrons with kinetic energies as low as 1.5 eV on the sample while simultaneously allowing for the detection of electrons emitted from the sample surface at kinetic energies ranging from ∼500 eV to 0 eV. The spectrometer’s unique characteristics made it possible to perform (a) first experiments demonstrating the direct transition of a positron from an unbound scattering state to a bound surface state and (b) the first experiments demonstrating that Auger electron spectramore » can be obtained down to 0 eV without the beam induced secondary electron background obscuring the low energy part of the spectra. Data are presented which show alternative means of estimating positron surface state binding energy and background-free Auger spectra.« less

Energy efficient synthesis of boranes

DOEpatents

Thorn, David L [Los Alamos, NM; Tumas, William [Los Alamos, NM; Schwarz, Daniel E [Los Alamos, NM; Burrell, Anthony K [Los Alamos, NM

2012-01-24

The reaction of halo-boron compounds (B--X compounds, compounds having one or more boron-halogen bonds) with silanes provides boranes (B--H compounds, compounds having one or more B--H bonds) and halosilanes. Inorganic hydrides, such as surface-bound silane hydrides (Si--H) react with B--X compounds to form B--H compounds and surface-bound halosilanes. The surface bound halosilanes are converted back to surface-bound silanes electrochemically. Halo-boron compounds react with stannanes (tin compounds having a Sn--H bond) to form boranes and halostannanes (tin compounds having a Sn--X bond). The halostannanes are converted back to stannanes electrochemically or by the thermolysis of Sn-formate compounds. When the halo-boron compound is BCl.sub.3, the B--H compound is B.sub.2H.sub.6, and where the reducing potential is provided electrochemically or by the thermolysis of formate.

Energy efficient synthesis of boranes

DOEpatents

Thorn, David L.; Tumas, William; Schwarz, Daniel E.; Burrell, Anthony K.

2010-11-23

The reaction of halo-boron compounds (B--X compounds, compounds having one or more boron-halogen bonds) with silanes provides boranes (B--H compounds, compounds having one or more B--H bonds) and halosilanes. Inorganic hydrides, such as surface-bound silane hydrides (Si--H) react with B--X compounds to form B--H compounds and surface-bound halosilanes. The surface bound halosilanes are converted back to surface-bound silanes electrochemically. Halo-boron compounds react with stannanes (tin compounds having a Sn--H bond) to form boranes and halostannanes (tin compounds having a Sn--X bond). The halostannanes are converted back to stannanes electrochemically or by the thermolysis of Sn-formate compounds. When the halo-boron compound is BCl.sub.3, the B--H compound is B.sub.2H.sub.6, and where the reducing potential is provided electrochemically or by the thermolysis of formate.

Plamonics for Biomolecular Sensors and THz Metamaterial Waveguides (Near and Far-Field Interfaces to DNA. Guided Nanostructures from RF to Lightwave: Exploiting the Spectrum)

DTIC Science & Technology

2014-12-17

surface bound modes named spoofed surface plasmon polariton (SSPP) modes. Such modes mimic the common optical surface plasmon mode traveling at...Triangle Park, NC 27709-2211 Terahertz, Biosensing, Mach Zehnder Interferometer, Multiplexer and Spoof surface Plasmon Polariton REPORT DOCUMENTATION PAGE...frequencies, the textured surfaces on a subwavelength scale can support surface bound modes named spoofed surface plasmon polariton (SSPP) modes. Such modes

Surface-Bound Casein Modulates the Adsorption and Activity of Kinesin on SiO2 Surfaces

PubMed Central

Ozeki, Tomomitsu; Verma, Vivek; Uppalapati, Maruti; Suzuki, Yukiko; Nakamura, Mikihiko; Catchmark, Jeffrey M.; Hancock, William O.

2009-01-01

Abstract Conventional kinesin is routinely adsorbed to hydrophilic surfaces such as SiO2. Pretreatment of surfaces with casein has become the standard protocol for achieving optimal kinesin activity, but the mechanism by which casein enhances kinesin surface adsorption and function is poorly understood. We used quartz crystal microbalance measurements and microtubule gliding assays to uncover the role that casein plays in enhancing the activity of surface-adsorbed kinesin. On SiO2 surfaces, casein adsorbs as both a tightly bound monolayer and a reversibly bound second layer that has a dissociation constant of 500 nM and can be desorbed by washing with casein-free buffer. Experiments using truncated kinesins demonstrate that in the presence of soluble casein, kinesin tails bind well to the surface, whereas kinesin head binding is blocked. Removing soluble casein reverses these binding profiles. Surprisingly, reversibly bound casein plays only a moderate role during kinesin adsorption, but it significantly enhances kinesin activity when surface-adsorbed motors are interacting with microtubules. These results point to a model in which a dynamic casein bilayer prevents reversible association of the heads with the surface and enhances association of the kinesin tail with the surface. Understanding protein-surface interactions in this model system should provide a framework for engineering surfaces for functional adsorption of other motor proteins and surface-active enzymes. PMID:19383474

Bound states of moving potential wells in discrete wave mechanics

NASA Astrophysics Data System (ADS)

Longhi, S.

2017-10-01

Discrete wave mechanics describes the evolution of classical or matter waves on a lattice, which is governed by a discretized version of the Schrödinger equation. While for a vanishing lattice spacing wave evolution of the continuous Schrödinger equation is retrieved, spatial discretization and lattice effects can deeply modify wave dynamics. Here we discuss implications of breakdown of exact Galilean invariance of the discrete Schrödinger equation on the bound states sustained by a smooth potential well which is uniformly moving on the lattice with a drift velocity v. While in the continuous limit the number of bound states does not depend on the drift velocity v, as one expects from the covariance of ordinary Schrödinger equation for a Galilean boost, lattice effects can lead to a larger number of bound states for the moving potential well as compared to the potential well at rest. Moreover, for a moving potential bound states on a lattice become rather generally quasi-bound (resonance) states.

Interacting quantum walkers: two-body bosonic and fermionic bound states

NASA Astrophysics Data System (ADS)

Krapivsky, P. L.; Luck, J. M.; Mallick, K.

2015-11-01

We investigate the dynamics of bound states of two interacting particles, either bosons or fermions, performing a continuous-time quantum walk on a one-dimensional lattice. We consider the situation where the distance between both particles has a hard bound, and the richer situation where the particles are bound by a smooth confining potential. The main emphasis is on the velocity characterizing the ballistic spreading of these bound states, and on the structure of the asymptotic distribution profile of their center-of-mass coordinate. The latter profile generically exhibits many internal fronts.

GRAVITATIONAL CONTRACTION VERSUS SUPERNOVA DRIVING AND THE ORIGIN OF THE VELOCITY DISPERSION–SIZE RELATION IN MOLECULAR CLOUDS

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

Ibáñez-Mejía, Juan C.; Mac Low, Mordecai-Mark; Klessen, Ralf S.

Molecular cloud (MC) observations show that clouds have non-thermal velocity dispersions that scale with the cloud size as σ ∝ R {sup 1/2} at a constant surface density, and for varying surface density scale with both the cloud’s size and surface density, σ {sup 2} ∝ R Σ. The energy source driving these chaotic motions remains poorly understood. We describe the velocity dispersions observed in a cloud population formed in a numerical simulation of a magnetized, stratified, supernova (SN)-driven, interstellar medium, including diffuse heating and radiative cooling, before and after we include the effects of the self-gravity of the gas.more » We compare the relationships between velocity dispersion, size, and surface density measured in the simulated cloud population to those found in observations of Galactic MCs. Our simulations prior to the onset of self-gravity suggest that external SN explosions alone do not drive turbulent motions of the observed magnitudes within dense clouds. On the other hand, self-gravity induces non-thermal motions as gravitationally bound clouds begin to collapse in our model, approaching the observed relations between velocity dispersion, size, and surface density. Energy conservation suggests that the observed behavior is consistent with the kinetic energy being proportional to the gravitational energy. However, the clouds in our model show no sign of reaching a stable equilibrium state at any time, even for strongly magnetized clouds. We conclude that gravitationally bound MCs are always in a state of gravitational contraction and their properties are a natural result of this chaotic collapse. In order to agree with observed star formation efficiencies, this process must be terminated by the early destruction of the clouds, presumably from internal stellar feedback.« less

Impurity bound states in fully gapped d-wave superconductors with subdominant order parameters

PubMed Central

Mashkoori, Mahdi; Björnson, Kristofer; Black-Schaffer, Annica M.

2017-01-01

Impurities in superconductors and their induced bound states are important both for engineering novel states such as Majorana zero-energy modes and for probing bulk properties of the superconducting state. The high-temperature cuprates offer a clear advantage in a much larger superconducting order parameter, but the nodal energy spectrum of a pure d-wave superconductor only allows virtual bound states. Fully gapped d-wave superconducting states have, however, been proposed in several cuprate systems thanks to subdominant order parameters producing d + is- or d + id′-wave superconducting states. Here we study both magnetic and potential impurities in these fully gapped d-wave superconductors. Using analytical T-matrix and complementary numerical tight-binding lattice calculations, we show that magnetic and potential impurities behave fundamentally different in d + is- and d + id′-wave superconductors. In a d + is-wave superconductor, there are no bound states for potential impurities, while a magnetic impurity produces one pair of bound states, with a zero-energy level crossing at a finite scattering strength. On the other hand, a d + id′-wave symmetry always gives rise to two pairs of bound states and only produce a reachable zero-energy level crossing if the normal state has a strong particle-hole asymmetry. PMID:28281570

Deformability of adsorbents during adsorption and principles of the thermodynamics of solid-phase systems

NASA Astrophysics Data System (ADS)

Tovbin, Yu. K.

2017-09-01

A microscopic theory of adsorption, based on a discrete continuum lattice gas model for noninert (including deformable) adsorbents that change their lattice parameters during adsorption, is presented. Cases of the complete and partial equilibrium states of the adsorbent are considered. In the former, the adsorbent consists of coexisting solid and vapor phases of adsorbent components, and the adsorbate is a mobile component of the vapor phase with an arbitrary density (up to that of the liquid adsorbate phase). The adsorptive transitioning to the bound state changes the state of the near-surface region of the adsorbent. In the latter, there are no equilibrium components of the adsorbent between the solid and vapor phases. The adsorbent state is shown to be determined by its prehistory, rather than set by chemical potentials of vapor of its components. Relations between the microscopic theory and thermodynamic interpretations are discussed: (1) adsorption on an open surface, (2) two-dimensional stratification of the adsorbate mobile phase on an open homogeneous surface, (3) small microcrystals in vacuum and the gas phase, and (4) adsorption in porous systems.

SFG analysis of surface bound proteins: a route towards structure determination.

PubMed

Weidner, Tobias; Castner, David G

2013-08-14

The surface of a material is rapidly covered with proteins once that material is placed in a biological environment. The structure and function of these bound proteins play a key role in the interactions and communications of the material with the biological environment. Thus, it is crucial to gain a molecular level understanding of surface bound protein structure. While X-ray diffraction and solution phase NMR methods are well established for determining the structure of proteins in the crystalline or solution phase, there is not a corresponding single technique that can provide the same level of structural detail about proteins at surfaces or interfaces. However, recent advances in sum frequency generation (SFG) vibrational spectroscopy have significantly increased our ability to obtain structural information about surface bound proteins and peptides. A multi-technique approach of combining SFG with (1) protein engineering methods to selectively introduce mutations and isotopic labels, (2) other experimental methods such as time-of-flight secondary ion mass spectrometry (ToF-SIMS) and near edge X-ray absorption fine structure (NEXAFS) to provide complementary information, and (3) molecular dynamic (MD) simulations to extend the molecular level experimental results is a particularly promising route for structural characterization of surface bound proteins and peptides. By using model peptides and small proteins with well-defined structures, methods have been developed to determine the orientation of both backbone and side chains to the surface.

SFG analysis of surface bound proteins: A route towards structure determination

PubMed Central

Weidner, Tobias; Castner, David G.

2013-01-01

The surface of a material is rapidly covered with proteins once that material is placed in a biological environment. The structure and function of these bound proteins play a key role in the interactions and communications of the material with the biological environment. Thus, it is crucial to gain a molecular level understanding of surface bound protein structure. While X-ray diffraction and solution phase NMR methods are well established for determining the structure of proteins in the crystalline or solution phase, there is not a corresponding single technique that can provide the same level of structural detail about proteins at surfaces or interfaces. However, recent advances in sum frequency generation (SFG) vibrational spectroscopy have significantly increased our ability to obtain structural information about surface bound proteins and peptides. A multi-technique approach of combining SFG with (1) protein engineering methods to selectively introduce mutations and isotopic labels, (2) other experimental methods such as time-of-flight secondary ion mass spectrometry (ToF-SIMS) and near edge x-ray absorption fine structure (NEXAFS) to provide complementary information, and (3) molecular dynamic (MD) simulations to extend the molecular level experimental results is a particularly promising route for structural characterization of surface bound proteins and peptides. By using model peptides and small proteins with well-defined structures, methods have been developed to determine the orientation of both backbone and side chains to the surface. PMID:23727992

Generalized surface tension bounds in vacuum decay

NASA Astrophysics Data System (ADS)

Masoumi, Ali; Paban, Sonia; Weinberg, Erick J.

2018-02-01

Coleman and De Luccia (CDL) showed that gravitational effects can prevent the decay by bubble nucleation of a Minkowski or AdS false vacuum. In their thin-wall approximation this happens whenever the surface tension in the bubble wall exceeds an upper bound proportional to the difference of the square roots of the true and false vacuum energy densities. Recently it was shown that there is another type of thin-wall regime that differs from that of CDL in that the radius of curvature grows substantially as one moves through the wall. Not only does the CDL derivation of the bound fail in this case, but also its very formulation becomes ambiguous because the surface tension is not well defined. We propose a definition of the surface tension and show that it obeys a bound similar in form to that of the CDL case. We then show that both thin-wall bounds are special cases of a more general bound that is satisfied for all bounce solutions with Minkowski or AdS false vacua. We discuss the limit where the parameters of the theory attain critical values and the bound is saturated. The bounce solution then disappears and a static planar domain wall solution appears in its stead. The scalar field potential then is of the form expected in supergravity, but this is only guaranteed along the trajectory in field space traced out by the bounce.

Spectroscopic studies of organometallic compounds on single crystal metal surfaces: Surface acetylides of silver (110)

NASA Astrophysics Data System (ADS)

Madix, Robert J.

The nature of compounds formed by the reaction of organic molecules with metal surfaces can be studied with a battery of analytical methods based on both physicals and chemical understanding. In this paper the application of UPS, XPS, LEED and EELS as well as temperature programmed reaction spectroscopy (TPRS) and chemical titration methods to the characterization of surface complexes is discussed. Particular emphasis is given to the reaction of acetylene with a single crystal surface of silver, Ag(110). Previous work has shown that this surface, when clean, is unreactive to hydrocarbons, alcohols and carboxylic acids under ultra high vacuum conditions. Preadsorption of oxygen, however, renders the surface reactive, and a wide variety of organometallic surface compounds can be formed. As expected then, no stable adsorption state and no reaction was observed with clean Ag(110) following room temperature exposure to acetylene. Following exposure at 150 K, however, a weekly bound chemisorption state was observed to desorb at 195 K, indicating a binding energy to the surface of approximately 12 kcal/gmole. Reaction with preadsorbed oxygen gave water formulation upon dosing and produced surface intermediates which yeilded two acetylene desorption states at 195 and 175 K. Heating above 300 K to completely desorb the higher temperature state produced new, well-defined LEED Features due to residual surface carbon which disappeared when the surface was heated above 550 K. Clearly, there were distinc changes in the nature of the absorbed layer at 195, 300 and 550 K. These changes were reflected in XPS. For the weakly chemisorbed acetylene a large C(ls) peak at 285.6 eV with a small, broad, indistinc shoulder at higher binding energy (288.2) was observed. The spectrum of the species following acetylene desorption at 275 K, however, showed the formulation of a large C(ls) peak at 283.6 eV in addition to peaks characteristics of the weakly chemisorbed state. This result indicated that the carbon atoms in the surface acetylide became inequivalent. Heating to 300 K produced a single peak at 282.8 eV which reverted to 283.4 when heated above 550 K; the carbon atoms became chemically equivalent. This latter state could be removed completely by O 2 to form CO 2(3). The XPS results showed quantitative conversion of all surface carbon from each state observed. Conclusive evidence regarding the identity of these states was obtained with titration experiments with deuterated acetic acid. CH 3COOD was adsorbed on top of the acetylenic residues at 150 K and heated to note the isotopes of acetylene that desorbed. The 275 K acetylene desorption peak, which showed inequivalent carbon atoms, was titrated by CH 3COOD to form C 2HD, indicating C 2H as the stable surface species. The species formed above 300 K, which showed equivalent carbon atoms in XPS, titrated to form C 2D 2, indicating a C 2 surface species. In each case the formulation of surface acetate was quantitative. The structure of these species was probed further with high resolution electron energy loss spectroscopy. The weakly chemisorbed molecular state exhibited vibrational losses at 300, 700 and 3270 cm -1, characteristics of an acetylene-surface stretching motion, a C-C-H bend and the C-H stretch respectively. No C-C stretch was observed, indicating that the molecule lay parallel to the plane of the surface. For adsorbed C 2H, bands were observed at 300, 690 and 3250cm -1. The high C-H stretching frequency indicated that the C-C bound order was near three. The absence of a C-C stretch in the spectrum was somewhat surprising, but was explained by a σ-π bonded complex in which the -C=CH species was flattened toward the surface by an interaction of an Ag atom with the π system of the acetylide.

The origin of unequal bond lengths in the C 1B 2 state of SO 2: Signatures of high-lying potential energy surface crossings in the low-lying vibrational structure

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

Park, G. Barratt; Jiang, Jun; Field, Robert W.

Here the C 1B 2 state of SO 2 has a double-minimum potential in the antisymmetric stretch coordinate, such that the minimum energy geometry has nonequivalent SO bond lengths. The asymmetry in the potential energy surface is expressed as a staggering in the energy levels of the v' 3 progression. We have recently made the first observation of low-lying levels with odd quanta of v' 3, which allows us--in the current work--to characterize the origins of the level staggering. Our work demonstrates the usefulness of low-lying vibrational level structure, where the character of the wavefunctions can be relatively easily understood,more » to extract information about dynamically important potential energy surface crossings that occur at much higher energy. The measured staggering pattern is consistent with a vibronic coupling model for the double-minimum, which involves direct coupling to the bound 2 1A 1 state and indirect coupling with the repulsive 3 1A 1 state. The degree of staggering in the v' 3 levels increases with quanta of bending excitation, which is consistent with the approach along the C state potential energy surface to a conical intersection with the 2 1A 1 surface at a bond angle of ~145°.« less

The origin of unequal bond lengths in the C 1B 2 state of SO 2: Signatures of high-lying potential energy surface crossings in the low-lying vibrational structure

DOE PAGES

Park, G. Barratt; Jiang, Jun; Field, Robert W.

2016-04-14

Here the C 1B 2 state of SO 2 has a double-minimum potential in the antisymmetric stretch coordinate, such that the minimum energy geometry has nonequivalent SO bond lengths. The asymmetry in the potential energy surface is expressed as a staggering in the energy levels of the v' 3 progression. We have recently made the first observation of low-lying levels with odd quanta of v' 3, which allows us--in the current work--to characterize the origins of the level staggering. Our work demonstrates the usefulness of low-lying vibrational level structure, where the character of the wavefunctions can be relatively easily understood,more » to extract information about dynamically important potential energy surface crossings that occur at much higher energy. The measured staggering pattern is consistent with a vibronic coupling model for the double-minimum, which involves direct coupling to the bound 2 1A 1 state and indirect coupling with the repulsive 3 1A 1 state. The degree of staggering in the v' 3 levels increases with quanta of bending excitation, which is consistent with the approach along the C state potential energy surface to a conical intersection with the 2 1A 1 surface at a bond angle of ~145°.« less

Activating distillation with an infinitesimal amount of bound entanglement.

PubMed

Vollbrecht, Karl Gerd H; Wolf, Michael M

2002-06-17

We show that bipartite quantum states of any dimension, which do not have a positive partial transpose (NPPT), become 1-distillable when one adds an infinitesimal amount of bound entanglement. To this end we investigate the activation properties of a new class of symmetric bound entangled states of full rank. It is shown that in this set there exist universal activator states capable of activating the distillation of any NPPT state. The result shows that even a small amount of bound entanglement can be useful for quantum information purposes.

Search for bound states of the eta-meson in light nuclei

NASA Technical Reports Server (NTRS)

Chrien, R. E.; Bart, S.; Pile, P.; Sutter, R.; Tsoupas, N.; Funsten, H. O.; Finn, J. M.; Lyndon, C.; Punjabi, V.; Perdrisat, C. F.

1988-01-01

A search for nuclear-bound states of the eta meson was carried out. Targets of lithium, carbon, oxygen, and aluminum were placed in a pion(+) beam at 800 MeV/c. A predicted eta bound state in O-15* (E sub x approx. = 540 MeV) with a width of approx. 9 MeV was not observed. A bound state of a size 1/3 of the predicted cross section would have been seen in this experiment at a confidence level of 3sigma (P is greater than 0.9987).

A Langevin dynamics simulation study of the tribology of polymer loop brushes.

PubMed

Yin, Fang; Bedrov, Dmitry; Smith, Grant D; Kilbey, S Michael

2007-08-28

The tribology of surfaces modified with doubly bound polymer chains (loops) has been investigated in good solvent conditions using Langevin dynamics simulations. The density profiles, brush interpenetration, chain inclination, normal forces, and shear forces for two flat substrates modified by doubly bound bead-necklace polymers and equivalent singly bound polymers (twice as many polymer chains of 12 the molecular weight of the loop chains) were determined and compared as a function of surface separation, grafting density, and shear velocity. The doubly bound polymer layers showed less interpenetration with decreasing separation than the equivalent singly bound layers. Surprisingly, this difference in interpenetration between doubly bound polymer and singly bound polymer did not result in decreased friction at high shear velocity possibly due to the decreased ability of the doubly bound chains to deform in response to the applied shear. However, at lower shear velocity, where deformation of the chains in the flow direction is less pronounced and the difference in interpenetration is greater between the doubly bound and singly bound chains, some reduction in friction was observed.

Designed Long-Lived Emission from CdSe Quantum Dots through Reversible Electronic Energy Transfer with a Surface-Bound Chromophore.

PubMed

La Rosa, Marcello; Denisov, Sergey A; Jonusauskas, Gediminas; McClenaghan, Nathan D; Credi, Alberto

2018-03-12

The size-tunable emission of luminescent quantum dots (QDs) makes them highly interesting for applications that range from bioimaging to optoelectronics. For the same applications, engineering their luminescence lifetime, in particular, making it longer, would be as important; however, no rational approach to reach this goal is available to date. We describe a strategy to prolong the emission lifetime of QDs through electronic energy shuttling to the triplet excited state of a surface-bound molecular chromophore. To implement this idea, we made CdSe QDs of different sizes and carried out self-assembly with a pyrene derivative. We observed that the conjugates exhibit delayed luminescence, with emission decays that are prolonged by more than 3 orders of magnitude (lifetimes up to 330 μs) compared to the parent CdSe QDs. The mechanism invokes unprecedented reversible quantum dot to organic chromophore electronic energy transfer. © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Interactions of a designed peptide with lipopolysaccharide: Bound conformation and anti-endotoxic activity

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

Bhunia, Anirban; Chua, Geok Lin; Domadia, Prerna N.

Designed peptides that would selectively interact with lipopolysaccharide (LPS) or endotoxin and fold into specific conformations could serve as important scaffolds toward the development of antisepsis compounds. Here, we describe solution structure of a designed amphipathic peptide, H{sub 2}N-YVKLWRMIKFIR-CONH{sub 2} (YW12D) in complex with endotoxin as determined by transferred nuclear Overhauser effect spectroscopy. The conformation of the isolated peptide is highly flexible, but undergoes a dramatic structural stabilization in the presence of LPS. Structure calculations reveal that the peptide presents two amphipathic surfaces in its bound state to LPS whereby each surface is characterized by two positive charges and amore » number of aromatic and/or aliphatic residues. ITC data suggests that peptide interacts with two molecules of lipid A. In activity assays, YW12D exhibits neutralization of LPS toxicity with very little hemolysis of red blood cells. Structural and functional properties of YW12D would be applicable in designing low molecular weight non-toxic antisepsis molecules.« less

Interaction of Huntingtin Exon-1 Peptides with Lipid-Based Micellar Nanoparticles Probed by Solution NMR and Q-Band Pulsed EPR.

PubMed

Ceccon, Alberto; Schmidt, Thomas; Tugarinov, Vitali; Kotler, Samuel A; Schwieters, Charles D; Clore, G Marius

2018-05-23

Lipid-based micellar nanoparticles promote aggregation of huntingtin exon-1 peptides. Here we characterize the interaction of two such peptides, htt NT Q  7 and htt NT Q  10 comprising the N-terminal amphiphilic domain of huntingtin followed by 7 and 10 glutamine repeats, respectively, with 8 nm lipid micelles using NMR chemical exchange saturation transfer (CEST), circular dichroism and pulsed Q-band EPR. Exchange between free and micelle-bound htt NT Q  n peptides occurs on the millisecond time scale with a K D ∼ 0.5-1 mM. Upon binding micelles, residues 1-15 adopt a helical conformation. Oxidation of Met 7 to a sulfoxide reduces the binding affinity for micelles ∼3-4-fold and increases the length of the helix by a further two residues. A structure of the bound monomer unit is calculated from the backbone chemical shifts of the micelle-bound state obtained from CEST. Pulsed Q-band EPR shows that a monomer-dimer equilibrium exists on the surface of the micelles and that the two helices of the dimer adopt a parallel orientation, thereby bringing two disordered polyQ tails into close proximity which may promote aggregation upon dissociation from the micelle surface.

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

Neale, Nathan R; Carroll, Gerard; Limpens, Rens

The optical properties of silicon nanocrystals (Si NCs) are a subject of intense study and continued debate. In particular, Si NC photoluminescence (PL) properties are known to depend strongly on the surface chemistry, resulting in electron-hole recombination pathways derived from the Si NC band-edge, surface-state defects, or combined NC-conjugated ligand hybrid states. In this Letter, we perform a comparison of three different saturated surface functional groups - alkyls, amides, and alkoxides - on nonthermal plasma-synthesized Si NCs. We find a systematic and size-dependent high-energy (blue) shift in the PL spectrum of Si NCs with amide and alkoxy functionalization relative tomore » alkyl. Time-resolved photoluminescence and transient absorption spectroscopies reveal no change in the excited-state dynamics between Si NCs functionalized with alkyl, amide, or alkoxide ligands, showing for the first time that saturated ligands - not only surface-derived charge-transfer states or hybridization between NC and low-lying ligand orbitals - are responsible for tuning the Si NC optical properties. To explain these PL shifts we propose that the atom bound to the Si NC surface strongly interacts with the Si NC electronic wave function and modulates the Si NC quantum confinement. These results reveal a potentially broadly applicable correlation between the optoelectronic properties of Si NCs and related quantum-confined structures based on the interaction between NC surfaces and the ligand binding group.« less

Bounded state variables and the calculus of variations

NASA Technical Reports Server (NTRS)

Hanafy, L. M.

1972-01-01

An optimal control problem with bounded state variables is transformed into a Lagrange problem by means of differentiable mappings which take some Euclidean space onto the control and state regions. Whereas all such mappings lead to a Lagrange problem, it is shown that only those which are defined as acceptable pairs of transformations are suitable in the sense that solutions to the transformed Lagrange problem will lead to solutions to the original bounded state problem and vice versa. In particular, an acceptable pair of transformations is exhibited for the case when the control and state regions are right parallelepipeds. Finally, a description of the necessary conditions for the bounded state problem which were obtained by this method is given.

Ensemble-based characterization of unbound and bound states on protein energy landscape

PubMed Central

Ruvinsky, Anatoly M; Kirys, Tatsiana; Tuzikov, Alexander V; Vakser, Ilya A

2013-01-01

Physicochemical description of numerous cell processes is fundamentally based on the energy landscapes of protein molecules involved. Although the whole energy landscape is difficult to reconstruct, increased attention to particular targets has provided enough structures for mapping functionally important subspaces associated with the unbound and bound protein structures. The subspace mapping produces a discrete representation of the landscape, further called energy spectrum. We compiled and characterized ensembles of bound and unbound conformations of six small proteins and explored their spectra in implicit solvent. First, the analysis of the unbound-to-bound changes points to conformational selection as the binding mechanism for four proteins. Second, results show that bound and unbound spectra often significantly overlap. Moreover, the larger the overlap the smaller the root mean square deviation (RMSD) between the bound and unbound conformational ensembles. Third, the center of the unbound spectrum has a higher energy than the center of the corresponding bound spectrum of the dimeric and multimeric states for most of the proteins. This suggests that the unbound states often have larger entropy than the bound states. Fourth, the exhaustively long minimization, making small intrarotamer adjustments (all-atom RMSD ≤ 0.7 Å), dramatically reduces the distance between the centers of the bound and unbound spectra as well as the spectra extent. It condenses unbound and bound energy levels into a thin layer at the bottom of the energy landscape with the energy spacing that varies between 0.8–4.6 and 3.5–10.5 kcal/mol for the unbound and bound states correspondingly. Finally, the analysis of protein energy fluctuations showed that protein vibrations itself can excite the interstate transitions, including the unbound-to-bound ones. PMID:23526684

Dynamic Structure of Bombolitin II Bound to Lipid Bilayers as Revealed by Solid-state NMR and Molecular-Dynamics Simulation

PubMed Central

Toraya, Shuichi; Javkhlantugs, Namsrai; Mishima, Daisuke; Nishimura, Katsuyuki; Ueda, Kazuyoshi; Naito, Akira

2010-01-01

Bombolitin II (BLT2) is one of the hemolytic heptadecapeptides originally isolated from the venom of a bumblebee. Structure and orientation of BLT2 bound to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) membranes were determined by solid-state 31P and 13C NMR spectroscopy. 31P NMR spectra showed that BLT2-DPPC membranes were disrupted into small particles below the gel-to-liquid crystalline phase transition temperature (Tc) and fused to form a magnetically oriented vesicle system where the membrane surface is parallel to the magnetic fields above the Tc. 13C NMR spectra of site-specifically 13C-labeled BLT2 at the carbonyl carbons were observed and the chemical shift anisotropies were analyzed to determine the dynamic structure of BLT2 bound to the magnetically oriented vesicle system. It was revealed that the membrane-bound BLT2 adopted an α-helical structure, rotating around the membrane normal with the tilt angle of the helical axis at 33°. Interatomic distances obtained from rotational-echo double-resonance experiments further showed that BLT2 adopted a straight α-helical structure. Molecular dynamics simulation performed in the BLT2-DPPC membrane system showed that the BLT2 formed a straight α-helix and that the C-terminus was inserted into the membrane. The α-helical axis is tilted 30° to the membrane normal, which is almost the same as the value obtained from solid-state NMR. These results suggest that the membrane disruption induced by BLT2 is attributed to insertion of BLT2 into the lipid bilayers. PMID:21081076

Low capping group surface density on zinc oxide nanocrystals.

PubMed

Valdez, Carolyn N; Schimpf, Alina M; Gamelin, Daniel R; Mayer, James M

2014-09-23

The ligand shell of colloidal nanocrystals can dramatically affect their stability and reaction chemistry. We present a methodology to quantify the dodecylamine (DDA) capping shell of colloidal zinc oxide nanocrystals in a nonpolar solvent. Using NMR spectroscopy, three different binding regimes are observed: strongly bound, weakly associated, and free in solution. The surface density of bound DDA is constant over a range of nanocrystal sizes, and is low compared to both predictions of the number of surface cations and maximum coverages of self-assembled monolayers. The density of strongly bound DDA ligands on the as-prepared ZnO NCs is 25% of the most conservative estimate of the maximum surface DDA density. Thus, these NCs do not resemble the common picture of a densely capped surface ligand layer. Annealing the ZnO NCs in molten DDA for 12 h at 160 °C, which is thought to remove surface hydroxide groups, resulted in a decrease of the weakly associated DDA and an increase in the density of strongly bound DDA, to ca. 80% of the estimated density of a self-assembled monolayer on a flat ZnO surface. These findings suggest that as-prepared nanocrystal surfaces contain hydroxide groups (protons on the ZnO surfaces) that inhibit strong binding of DDA.

Formation of mercury sulfide from Hg(II)−thiolate complexes in natural organic matter

USGS Publications Warehouse

Alain Manceau,; Cyprien Lemouchi,; Mironel Enescu,; Anne-Claire Gaillot,; Martine Lanson,; Valerie Magnin,; Pieter Glatzel,; Poulin, Brett; Ryan, Joseph N.; Aiken, George R.; Isabelle Gautier-Lunea,; Kathryn L. Nagy,

2015-01-01

Methylmercury is the environmental form of neurotoxic mercury that is biomagnified in the food chain. Methylation rates are reduced when the metal is sequestered in crystalline mercury sulfides or bound to thiol groups in macromolecular natural organic matter. Mercury sulfide minerals are known to nucleate in anoxic zones, by reaction of the thiol-bound mercury with biogenic sulfide, but not in oxic environments. We present experimental evidence that mercury sulfide forms from thiol-bound mercury alone in aqueous dark systems in contact with air. The maximum amount of nanoparticulate mercury sulfide relative to thiol-bound mercury obtained by reacting dissolved mercury and soil organic matter matches that detected in the organic horizon of a contaminated soil situated downstream from Oak Ridge, TN, in the United States. The nearly identical ratios of the two forms of mercury in field and experimental systems suggest a common reaction mechanism for nucleating the mineral. We identified a chemical reaction mechanism that is thermodynamically favorable in which thiol-bound mercury polymerizes to mercury–sulfur clusters. The clusters form by elimination of sulfur from the thiol complexes via breaking of mercury–sulfur bonds as in an alkylation reaction. Addition of sulfide is not required. This nucleation mechanism provides one explanation for how mercury may be immobilized, and eventually sequestered, in oxygenated surface environments.

Energy density engineering via zero-admittance domains in all-dielectric stratified materials

NASA Astrophysics Data System (ADS)

Amra, Claude; Zerrad, Myriam; Lemarchand, Fabien; Lereu, Aude; Passian, Ali; Zapien, Juan Antonio; Lequime, Michel

2018-02-01

Emerging photonic, sensing, and quantum applications require high fields and tight localization but low power consumption. Spatial, spectral, and magnitude control of electromagnetic fields is of key importance for enabling experiments in atomic, molecular, and optical physics. We introduce the concept of zero-admittance domains as a mechanism for tailoring giant optical fields bound within or on the surface of dielectric media. The described mechanism permits the creation of highly localized fields of extreme amplitudes simultaneously for incident photons of multiple wavelengths and incidence angles but arbitrary polarization states. No material constraints are placed upon the bounding media. Both intrinsic and extrinsic potential practical limitations of the predicted field enhancement are analyzed and applications relevant to optical sensors and microsources are briefly discussed.

Adsorption and bioactivity studies of albumin onto hydroxyapatite surface.

PubMed

Mavropoulos, Elena; Costa, Andréa M; Costa, Lilian T; Achete, Carlos A; Mello, Alexandre; Granjeiro, José M; Rossi, Alexandre M

2011-03-01

Bovine serum albumin (BSA) may have an inhibitory or promoter effect on hydroxyapatite (HA) nucleation when apatite is precipitated in a medium containing the protein. In this study we evaluated the influence of BSA on the precipitation of calcium phosphate phases (CP) from simulated body fluid (SBF) when the protein was previously bounded to HA surface. The kinetics of BSA immobilization onto hydroxyapatite surface was performed in different buffers and protein concentrations in order to adjust experimental conditions in which BSA was tightly linked to HA surface for long periods in SBF solution. It was shown that for BSA concentration higher than 0.1mg/mL the adsorption to HA surface followed Langmuir-Freundlich mechanisms, which confirmed the existence of cooperative protein-protein interactions on HA surface. Fourier Transformed Infrared Attenuated Total Reflectance Microscopy (FTIRM-ATR) evidenced changes in BSA conformational state in favor of less-ordered structure. Analyses from high resolution grazing incident X-ray diffraction using synchrotron radiation (GIXRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) showed that a poorly crystalline calcium phosphate was precipitated on the surface of HA discs coated with BSA, after the immersion in SBF for 4 days. The new bioactive layer had morphological characteristics similar to the one formed on the HA surface without protein. It was identified as a carbonated apatite with preferential crystal growth along apatite 002 direction. The GIXRD results also revealed that BSA layer bound to the surface inhibited the HA dissolution leading to a reduction on the formation of new calcium phosphate phase. 2010 Elsevier B.V. All rights reserved.

Reaching the Quantum Cramér-Rao Bound for Transmission Measurements

NASA Astrophysics Data System (ADS)

Woodworth, Timothy; Chan, Kam Wai Clifford; Marino, Alberto

2017-04-01

The quantum Cramér-Rao bound (QCRB) is commonly used to quantify the lower bound for the uncertainty in the estimation of a given parameter. Here, we calculate the QCRB for transmission measurements of an optical system probed by a beam of light. Estimating the transmission of an optical element is important as it is required for the calibration of optimal states for interferometers, characterization of high efficiency photodetectors, or as part of other measurements, such as those in plasmonic sensors or in ellipsometry. We use a beam splitter model for the losses introduced by the optical system to calculate the QCRB for different input states. We compare the bound for a coherent state, a two-mode squeezed-state (TMSS), a single-mode squeezed-state (SMSS), and a Fock state and show that it is possible to obtain an ultimate lower bound, regardless of the state used to probe the system. We prove that the Fock state gives the lowest possible uncertainty in estimating the transmission for any state and demonstrate that the TMSS and SMSS approach this ultimate bound for large levels of squeezing. Finally, we show that a simple measurement strategy for the TMSS, namely an intensity difference measurement, is able to saturate the QCRB. Work supported by the W.M. Keck Foundation.

Search for a hidden strange baryon-meson bound state from ϕ production in a nuclear medium

NASA Astrophysics Data System (ADS)

Gao, Haiyan; Huang, Hongxia; Liu, Tianbo; Ping, Jialun; Wang, Fan; Zhao, Zhiwen

2017-05-01

We investigate the hidden strange light baryon-meson system. With the resonating-group method, two bound states, η'-N and ϕ -N , are found in the quark delocalization color screening model. Focusing on the ϕ -N bound state around 1950 MeV, we obtain the total decay width of about 4 MeV by calculating the phase shifts in the resonance scattering processes. To study the feasibility of an experimental search for the ϕ -N bound state, we perform a Monte Carlo simulation of the bound state production with an electron beam and a gold target. In the simulation, we use the CLAS12 detector with the Forward Tagger and the BONUS12 detector in Hall B at Jefferson Lab. Both the signal and the background channels are estimated. We demonstrate that the signal events can be separated from the background with some momentum cuts. Therefore it is feasible to experimentally search for the ϕ -N bound state through the near threshold ϕ meson production from heavy nuclei.

Expansion Hamiltonian model for a diatomic molecule adsorbed on a surface: Vibrational states of the CO/Cu(100) system including surface vibrations

NASA Astrophysics Data System (ADS)

Meng, Qingyong; Meyer, Hans-Dieter

2015-10-01

Molecular-surface studies are often done by assuming a corrugated, static (i.e., rigid) surface. To be able to investigate the effects that vibrations of surface atoms may have on spectra and cross sections, an expansion Hamiltonian model is proposed on the basis of the recently reported [R. Marquardt et al., J. Chem. Phys. 132, 074108 (2010)] SAP potential energy surface (PES), which was built for the CO/Cu(100) system with a rigid surface. In contrast to other molecule-surface coupling models, such as the modified surface oscillator model, the coupling between the adsorbed molecule and the surface atoms is already included in the present expansion SAP-PES model, in which a Taylor expansion around the equilibrium positions of the surface atoms is performed. To test the quality of the Taylor expansion, a direct model, that is avoiding the expansion, is also studied. The latter, however, requests that there is only one movable surface atom included. On the basis of the present expansion and direct models, the effects of a moving top copper atom (the one to which CO is bound) on the energy levels of a bound CO/Cu(100) system are studied. For this purpose, the multiconfiguration time-dependent Hartree calculations are carried out to obtain the vibrational fundamentals and overtones of the CO/Cu(100) system including a movable top copper atom. In order to interpret the results, a simple model consisting of two coupled harmonic oscillators is introduced. From these calculations, the vibrational levels of the CO/Cu(100) system as function of the frequency of the top copper atom are discussed.

Expansion Hamiltonian model for a diatomic molecule adsorbed on a surface: Vibrational states of the CO/Cu(100) system including surface vibrations

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

Meng, Qingyong, E-mail: mengqingyong@dicp.ac.cn; Meyer, Hans-Dieter, E-mail: hans-dieter.meyer@pci.uni-heidelberg.de

2015-10-28

Molecular-surface studies are often done by assuming a corrugated, static (i.e., rigid) surface. To be able to investigate the effects that vibrations of surface atoms may have on spectra and cross sections, an expansion Hamiltonian model is proposed on the basis of the recently reported [R. Marquardt et al., J. Chem. Phys. 132, 074108 (2010)] SAP potential energy surface (PES), which was built for the CO/Cu(100) system with a rigid surface. In contrast to other molecule-surface coupling models, such as the modified surface oscillator model, the coupling between the adsorbed molecule and the surface atoms is already included in themore » present expansion SAP-PES model, in which a Taylor expansion around the equilibrium positions of the surface atoms is performed. To test the quality of the Taylor expansion, a direct model, that is avoiding the expansion, is also studied. The latter, however, requests that there is only one movable surface atom included. On the basis of the present expansion and direct models, the effects of a moving top copper atom (the one to which CO is bound) on the energy levels of a bound CO/Cu(100) system are studied. For this purpose, the multiconfiguration time-dependent Hartree calculations are carried out to obtain the vibrational fundamentals and overtones of the CO/Cu(100) system including a movable top copper atom. In order to interpret the results, a simple model consisting of two coupled harmonic oscillators is introduced. From these calculations, the vibrational levels of the CO/Cu(100) system as function of the frequency of the top copper atom are discussed.« less

Formation of Molecular Networks: Tailored Quantum Boxes and Behavior of Adsorbed CO in Them

NASA Astrophysics Data System (ADS)

Wyrick, Jon; Sun, Dezheng; Kim, Dae-Ho; Cheng, Zhihai; Lu, Wenhao; Zhu, Yeming; Luo, Miaomiao; Kim, Yong Su; Rotenberg, Eli; Kim, Kwangmoo; Einstein, T. L.; Bartels, Ludwig

2011-03-01

We show that the behavior of CO adsorbed into the pores of large regular networks on Cu(111) is significantly affected by their nano-scale lateral confinement and that formation of the networks themselves is directed by the Shockley surface state. Saturation coverages of CO are found to exhibit persistent dislocation lines; at lower coverages their mobility increases. Individual CO within the pores titrate the surface state, providing crucial information for understanding formation of the network as a result of optimization of the number N of electrons bound within each pore. Determination of N is based on quinone-coverage-dependent UPS data and an analysis of states of particles in a pore-shaped box (verified by CO's titration); a wide range of possible pore shapes and sizes has been considered. Work at UCR supported by NSF CHE 07-49949; at UMD by NSF CHE 07-50334 & UMD NSF-MRSEC DMR 05-20471.

Whispering gallery states of neutrons and anti-hydrogen atoms and their applications to fundamental and surface physics

NASA Astrophysics Data System (ADS)

Nesvizhevsky, Valery

2013-03-01

The `whispering gallery' effect has been known since ancient times for sound waves in air, later in water and more recently for a broad range of electromagnetic waves: radio, optics, Roentgen and so on. It is intensively used and explored due to its numerous crucial applications. It consists of wave localization near a curved reflecting surface and is expected for waves of various natures, for instance, for neutrons and (anti)atoms. For (anti)matter waves, it includes a new feature: a massive particle is settled in quantum states, with parameters depending on its mass. In this talk, we present the first observation of the quantum whispering-gallery effect for matter particles (cold neutrons) 1-2. This phenomenon provides an example of an exactly solvable problem analogous to the `quantum bouncer'; it is complementary to recently discovered gravitational quantum states of neutrons3. These two phenomena provide a direct demonstration of the weak equivalence principle for a massive particle in a quantum state. Deeply bound long-living states are weakly sensitive to surface potential; highly excited short-living states are very sensitive to the wall nuclear potential shape. Therefore, they are a promising tool for studying fundamental neutron-matter interactions, quantum neutron optics and surface physics effects. Analogous phenomena could be measured with atoms and anti-atoms 4-5.

Quantum mechanics of a constrained particle

NASA Astrophysics Data System (ADS)

da Costa, R. C. T.

1981-04-01

The motion of a particle rigidly bounded to a surface is discussed, considering the Schrödinger equation of a free particle constrained to move, by the action of an external potential, in an infinitely thin sheet of the ordinary three-dimensional space. Contrary to what seems to be the general belief expressed in the literature, this limiting process gives a perfectly well-defined result, provided that we take some simple precautions in the definition of the potentials and wave functions. It can then be shown that the wave function splits into two parts: the normal part, which contains the infinite energies required by the uncertainty principle, and a tangent part which contains "surface potentials" depending both on the Gaussian and mean curvatures. An immediate consequence of these results is the existence of different quantum mechanical properties for two isometric surfaces, as can be seen from the bound state which appears along the edge of a folded (but not stretched) plane. The fact that this surface potential is not a bending invariant (cannot be expressed as a function of the components of the metric tensor and their derivatives) is also interesting from the more general point of view of the quantum mechanics in curved spaces, since it can never be obtained from the classical Lagrangian of an a priori constrained particle without substantial modifications in the usual quantization procedures. Similar calculations are also presented for the case of a particle bounded to a curve. The properties of the constraining spatial potential, necessary to a meaningful limiting process, are discussed in some detail, and, as expected, the resulting Schrödinger equation contains a "linear potential" which is a function of the curvature.

Bound states for magic state distillation in fault-tolerant quantum computation.

PubMed

Campbell, Earl T; Browne, Dan E

2010-01-22

Magic state distillation is an important primitive in fault-tolerant quantum computation. The magic states are pure nonstabilizer states which can be distilled from certain mixed nonstabilizer states via Clifford group operations alone. Because of the Gottesman-Knill theorem, mixtures of Pauli eigenstates are not expected to be magic state distillable, but it has been an open question whether all mixed states outside this set may be distilled. In this Letter we show that, when resources are finitely limited, nondistillable states exist outside the stabilizer octahedron. In analogy with the bound entangled states, which arise in entanglement theory, we call such states bound states for magic state distillation.

Effects of bias and temperature on the intersubband absorption in very long wavelength GaAs/AlGaAs quantum well infrared photodetectors

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

Liu, X. H.; Zhou, X. H., E-mail: xhzhou@mail.sitp.ac.cn; Li, N.

2014-03-28

The temperature- and bias-dependent photocurrent spectra of very long wavelength GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) are studied using spectroscopic measurements and corresponding theoretical calculations. It is found that the peak response wavelength will shift as the bias and temperature change. Aided by band structure calculations, we propose a model of the double excited states and explain the experimental observations very well. In addition, the working mechanisms of the quasi-bound state confined in the quantum well, including the processes of tunneling and thermionic emission, are also investigated in detail. We confirm that the first excited state, which belongs to themore » quasi-bound state, can be converted into a quasi-continuum state induced by bias and temperature. These obtained results provide a full understanding of the bound-to-quasi-bound state and the bound-to-quasi-continuum state transition, and thus allow for a better optimization of QWIPs performance.« less

Propagating bound states in the continuum in dielectric gratings

NASA Astrophysics Data System (ADS)

Bulgakov, E. N.; Maksimov, D. N.; Semina, P. N.; Skorobogatov, S. A.

2018-06-01

We consider propagating bound states in the continuum in dielectric gratings. The gratings consist of a slab with ridges periodically arranged ether on top or on the both sides of the slab. Based on the Fourier modal approach we recover the leaky zones above the line of light to identify the geometries of the gratings supporting Bloch bound states propagating in the direction perpendicular to the ridges. Most importantly, it is demonstrated that if a two-side grating possesses either mirror or glide symmetry the Bloch bound states are stable to variation of parameters as far as the above symmetries are preserved.

The interaction of mercury with halogenated graphene

NASA Astrophysics Data System (ADS)

Kirchofer, Abigail; Sasmaz, Erdem; Wilcox, Jennifer

2011-03-01

The interaction of mercury with halogenated graphene was studied using plane-wave density functional theory. Various configurations of H, Hg, O and Br or Cl on the zigzag edge sites of graphene were investigated. Although Hg-Br (or -Cl) complexes were found to be stable on the surface, the most stable configurations found were those with Hg adjacent to O. The surface atoms Hg, O, and Br tend to repel each other during geometric optimization, moving towards an H atom nearest-neighbor where possible. The strength of the Hg-graphene interaction is very sensitive to the local environment. The Hg-graphene binding energy is strongest when the Hg is located next to a surface O but not immediately next to a bound Br. DOS analysis revealed that Hg adsorption involves a gain in Hg 6 p-states and a loss in Hg 5 s electron density, resulting in an oxidized surface-bound Hg complex. DOS analysis suggests that Br strengthens the Hg-graphene interaction by modifying the surface carbon electron density; however, when Br is adjacent to Hg, a direct Hg-Br interaction weakens the Hg-C bond. These investigations provide insight into the mechanism associated with enhanced Hg adsorption on Br-functionalized carbon materials for Hg emissions reductions from coal-fired power plant applications. The authors acknowledge the financial support by Electric Power Research Institute (EPRI).

Chemical stabilization of graphite surfaces

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

Bistrika, Alexander A.; Lerner, Michael M.

Embodiments of a device, or a component of a device, including a stabilized graphite surface, methods of stabilizing graphite surfaces, and uses for the devices or components are disclosed. The device or component includes a surface comprising graphite, and a plurality of haloaryl ions and/or haloalkyl ions bound to at least a portion of the graphite. The ions may be perhaloaryl ions and/or perhaloalkyl ions. In certain embodiments, the ions are perfluorobenzenesulfonate anions. Embodiments of the device or component including stabilized graphite surfaces may maintain a steady-state oxidation or reduction surface current density after being exposed to continuous oxidation conditionsmore » for a period of at least 1-100 hours. The device or component is prepared by exposing a graphite-containing surface to an acidic aqueous solution of the ions under oxidizing conditions. The device or component can be exposed in situ to the solution.« less

SPM of nonlinear surface plasmon waveguides

NASA Astrophysics Data System (ADS)

Li, Yuee; Zhang, Xiaoping

2008-10-01

Pulse propagation equation of nonlinear dispersion surface plasmon waveguide is educed strictly from wave equation. The nonlinear coefficient is defined and then used to assess and compare the nonlinear characteristic of three popular 1-D surface plasmon waveguides: the single metal-dielectric interface, the metal slab bounded by dielectric and the dielectric slab bounded by metal. SPM (self-phase modulation) of the typical surface plasmon waveguide is predicted and discussed.

Better bounds on optimal measurement and entanglement recovery, with applications to uncertainty and monogamy relations

NASA Astrophysics Data System (ADS)

Renes, Joseph M.

2017-10-01

We extend the recent bounds of Sason and Verdú relating Rényi entropy and Bayesian hypothesis testing (arXiv:1701.01974.) to the quantum domain and show that they have a number of different applications. First, we obtain a sharper bound relating the optimal probability of correctly distinguishing elements of an ensemble of states to that of the pretty good measurement, and an analogous bound for optimal and pretty good entanglement recovery. Second, we obtain bounds relating optimal guessing and entanglement recovery to the fidelity of the state with a product state, which then leads to tight tripartite uncertainty and monogamy relations.

Upper bounds on the error probabilities and asymptotic error exponents in quantum multiple state discrimination

NASA Astrophysics Data System (ADS)

Audenaert, Koenraad M. R.; Mosonyi, Milán

2014-10-01

We consider the multiple hypothesis testing problem for symmetric quantum state discrimination between r given states σ1, …, σr. By splitting up the overall test into multiple binary tests in various ways we obtain a number of upper bounds on the optimal error probability in terms of the binary error probabilities. These upper bounds allow us to deduce various bounds on the asymptotic error rate, for which it has been hypothesized that it is given by the multi-hypothesis quantum Chernoff bound (or Chernoff divergence) C(σ1, …, σr), as recently introduced by Nussbaum and Szkoła in analogy with Salikhov's classical multi-hypothesis Chernoff bound. This quantity is defined as the minimum of the pairwise binary Chernoff divergences min _{j

Bound states and propagating modes in quantum wires with sharp bends and/or constrictions

NASA Astrophysics Data System (ADS)

Razavy, M.

1997-06-01

A number of interesting problems of quantum wires with different geometries can be studied with the help of conformal mapping. These include crossed wires, twisting wires, conductors with constrictions, and wires with a bend. Here the Helmholz equation with Dirichlet boundary condition on the surface of the wire is transformed to a Schröautdinger-like equation with an energy-dependent nonseparable potential but with boundary conditions given on two straight lines. By expanding the wave function in terms of the Fourier series of one of the variables one obtains an infinite set of coupled ordinary differential equations. Only the propagating modes plus a few of the localized modes contribute significantly to the total wave function. Once the problem is solved, one can express the results in terms of the original variables using the inverse conformal mapping. As an example, the total wave function, the components of the current density, and the bound-state energy for a Γ-shaped quantum wire is calculated in detail.

Multiple nitrogen isotope recorders for surface ocean nitrate utilization in the Subarctic North Pacific and the Bering Sea

NASA Astrophysics Data System (ADS)

Ren, H. A.; Anderson, R.; Sigman, D. M.; Studer, A.; Winckler, G.; Haugh, G.; Serno, S.; Gersonde, R.

2017-12-01

Sedimentary nitrogen isotopes have been developed as a proxy to reconstruct the degree of nitrate utilization in the polar surface oceans. But its application could be compromised by 1) uncertainties on the biological production, transport, and preservation of the organic material in the sediments, and 2) potential changes in the isotopic composition of the nitrate source, that is remotely controlled by processes in other regions. In this study, we map and compare spatial patterns of three d15N recorders (bulk sedimentary nitrogen, the organic nitrogen within cleaned diatom frustules or diatom-bound N, and within planktonic foraminifera tests or foraminifera-bound N) from multicore surface sediments across the Subarctic North Pacific (SNP) and the Bering Sea between 60°N and 35°N. Diatom-bound d15N varies between 3.5 and 8.5‰. Its spatial variation is reversely correlated with changes in the surface nitrate concentration, and is consistent with the expected d15N change of the export production in a simple nitrate assimilation model. Similar to previous findings, diatom-bound d15N is generally 2 4‰ higher than the modeled d15N value of the export production, likely reflecting a biomass to frustual-bound N difference. However, the greater d15N elevation observed in the eastern open SNP may be best explained by lateral transport of residual surface nitrate enriched in 15N from the western SNP. The d15N of Neogloboquadrina pachyderma (sinistral) is similar to the diatom-bound d15N within 1‰. Bulk sedimentary d15N generally agrees with diatom-bound d15N, but is more variable. It is higher than diatom-bound d15N in the eastern and western transect close to the shelf area, likely reflecting a terrigenous source, while exceptionally low d15N values were found on the Bering Sea shelf, possibly due to contamination by mineral-associated inorganic N.

Efficient DNP NMR of Membrane Proteins: Sample Preparation Protocols, Sensitivity, and Radical Location

PubMed Central

Liao, Shu Y.; Lee, Myungwoon; Wang, Tuo; Sergeyev, Ivan V.; Hong, Mei

2016-01-01

Although dynamic nuclear polarization (DNP) has dramatically enhanced solid-state NMR spectral sensitivities of many synthetic materials and some biological macromolecules, recent studies of membrane-protein DNP using exogenously doped paramagnetic radicals as polarizing agents have reported varied and sometimes surprisingly limited enhancement factors. This motivated us to carry out a systematic evaluation of sample preparation protocols for optimizing the sensitivity of DNP NMR spectra of membrane-bound peptides and proteins at cryogenic temperatures of ~110 K. We show that mixing the radical with the membrane by direct titration instead of centrifugation gives a significant boost to DNP enhancement. We quantify the relative sensitivity enhancement between AMUPol and TOTAPOL, two commonly used radicals, and between deuterated and protonated lipid membranes. AMUPol shows ~4 fold higher sensitivity enhancement than TOTAPOL, while deuterated lipid membrane does not give net higher sensitivity for the membrane peptides than protonated membrane. Overall, a ~100 fold enhancement between the microwave-on and microwave-off spectra can be achieved on lipid-rich membranes containing conformationally disordered peptides, and absolute sensitivity gains of 105–160 can be obtained between low-temperature DNP spectra and high-temperature non-DNP spectra. We also measured the paramagnetic relaxation enhancement of lipid signals by TOTAPOL and AMUPol, to determine the depths of these two radicals in the lipid bilayer. Our data indicate a bimodal distribution of both radicals, a surface-bound fraction and a membrane-bound fraction where the nitroxides lie at ~10 Å from the membrane surface. TOTAPOL appears to have a higher membrane-embedded fraction than AMUPol. These results should be useful for membrane-protein solid-state NMR studies under DNP conditions and provide insights into how biradicals interact with phospholipid membranes. PMID:26873390

Observation of topologically protected bound states in photonic quantum walks.

PubMed

Kitagawa, Takuya; Broome, Matthew A; Fedrizzi, Alessandro; Rudner, Mark S; Berg, Erez; Kassal, Ivan; Aspuru-Guzik, Alán; Demler, Eugene; White, Andrew G

2012-06-06

Topological phases exhibit some of the most striking phenomena in modern physics. Much of the rich behaviour of quantum Hall systems, topological insulators, and topological superconductors can be traced to the existence of robust bound states at interfaces between different topological phases. This robustness has applications in metrology and holds promise for future uses in quantum computing. Engineered quantum systems--notably in photonics, where wavefunctions can be observed directly--provide versatile platforms for creating and probing a variety of topological phases. Here we use photonic quantum walks to observe bound states between systems with different bulk topological properties and demonstrate their robustness to perturbations--a signature of topological protection. Although such bound states are usually discussed for static (time-independent) systems, here we demonstrate their existence in an explicitly time-dependent situation. Moreover, we discover a new phenomenon: a topologically protected pair of bound states unique to periodically driven systems.

From single magnetic adatoms on superconductors to coupled spin chains

NASA Astrophysics Data System (ADS)

Franke, Katharina J.

Magnetic adsorbates on conventional s-wave superconductors lead to exchange interactions that induce Yu-Shiba-Rusinov (YSR) states inside the superconducting energy gap. Here, we employ tunneling spectroscopy at 1.1 K to investigate magnetic atoms and chains on superconducting Pb surfaces. We show that individual Manganese (Mn) atoms give rise to a distinct number of YSR-states. The single-atom junctions are stable over several orders of magnitude in conductance. We identify single-electron tunneling as well as Andreev processes. When the atoms are brought into sufficiently close distance, the Shiba states hybridize, thus giving rise to states with bonding and anti-bonding character. It has been shown that the Pb(110) surface supports the self-assembly of Fe chains, which exhibit fingerprints of Majorana bound states. Using superconducting tips, we resolve a rich subgap structure including peaks at zero energy and low-energy resonances, which overlap with the putative Majorana states. We gratefully acknowledge funding by the Deutsche Forschungsgemeinschaft through collaborative research Grant Sfb 658, and through Grant FR2726/4, as well by the European Research Council through Consolidator Grant NanoSpin.

Orbital Picture of Yu-Shiba-Rusinov Multiplets

NASA Astrophysics Data System (ADS)

Heinrich, Benjamin W.; Ruby, Michael; Franke, Katharina J.; Peng, Yang; von Oppen, Felix

Magnetic impurities on an s-wave superconductor induce Yu-Shiba-Rusinov (YSR) bound states within the excitation gap of the superconductor. Here, we investigate single manganese (Mn) atoms adsorbed on different surface orientations of superconducting lead (Pb) and the nature of their YSR states. Depending on the adsorption site and surface, we detect a distinct number and characteristic patterns of YSR states around the Mn atoms. We show that the YSR states inherit their properties from the Mn d levels, which are split by the surrounding crystal field. The periodicity of the long-range YSR oscillations allows us to identify a dominant coupling of the d states to the outer Fermi sheet of the two-band superconductor Pb. The long-range and directional nature of the states are promising for the design of coupled adatom structures, which could bear topological phases. We acknowledge funding by the Deutsche Forschungsgemeinschaft through Grant No. FR2726/4 and through collaborative research Grants No. Sfb 658, No. CRC 183, and No. SPP 1666, as well as by the European Research Council through Consolidator Grant NanoSpin.

Search for Chemically Bound Water in the Surface Layer of Mars Based on HEND/Mars Odyssey Data

NASA Technical Reports Server (NTRS)

Basilevsky, A. T.; Litvak, M. L.; Mitrofanov, I. G.; Boynton, W.; Saunders, R. S.

2003-01-01

This study is emphasized on search for signatures of chemically bound water in surface layer of Mars based on data acquired by High Energy Neutron Detector (HEND) which is part of the Mars Odyssey Gamma Ray Spectrometer (GRS). Fluxes of epithermal (probe the upper 1-2 m) and fast (the upper 20-30 cm) neutrons, considered in this work, were measured since mid February till mid June 2002. First analysis of this data set with emphasis of chemically bound water was made. Early publications of the GRS results reported low neutron flux at high latitudes, interpreted as signature of ground water ice, and in two low latitude areas: Arabia and SW of Olympus Mons (SWOM), interpreted as 'geographic variations in the amount of chemically and/or physically bound H2O and or OH...'. It is clear that surface materials of Mars do contain chemically bound water, but its amounts are poorly known and its geographic distribution was not analyzed.

Multiple topological electronic phases in superconductor MoC

NASA Astrophysics Data System (ADS)

Huang, Angus; Smith, Adam D.; Schwinn, Madison; Lu, Qiangsheng; Chang, Tay-Rong; Xie, Weiwei; Jeng, Horng-Tay; Bian, Guang

2018-05-01

The search for a superconductor with non-s -wave pairing is important not only for understanding unconventional mechanisms of superconductivity but also for finding new types of quasiparticles such as Majorana bound states. Materials with both topological band structure and superconductivity are promising candidates as p +i p superconducting states can be generated through pairing the spin-polarized topological surface states. In this work, the electronic and phonon properties of the superconductor molybdenum carbide (MoC) are studied with first-principles methods. Our calculations show that nontrivial band topology and s -wave Bardeen-Cooper-Schrieffer superconductivity coexist in two structural phases of MoC, namely the cubic α and hexagonal γ phases. The α phase is a strong topological insulator and the γ phase is a topological nodal-line semimetal with drumhead surface states. In addition, hole doping can stabilize the crystal structure of the α phase and elevate the transition temperature in the γ phase. Therefore, MoC in different structural forms can be a practical material platform for studying topological superconductivity.

An analysis of the vertical structure equation for arbitrary thermal profiles

NASA Technical Reports Server (NTRS)

Cohn, Stephen E.; Dee, Dick P.

1989-01-01

The vertical structure equation is a singular Sturm-Liouville problem whose eigenfunctions describe the vertical dependence of the normal modes of the primitive equations linearized about a given thermal profile. The eigenvalues give the equivalent depths of the modes. The spectrum of the vertical structure equation and the appropriateness of various upper boundary conditions, both for arbitrary thermal profiles were studied. The results depend critically upon whether or not the thermal profile is such that the basic state atmosphere is bounded. In the case of a bounded atmosphere it is shown that the spectrum is always totally discrete, regardless of details of the thermal profile. For the barotropic equivalent depth, which corresponds to the lowest eigen value, upper and lower bounds which depend only on the surface temperature and the atmosphere height were obtained. All eigenfunctions are bounded, but always have unbounded first derivatives. It was proved that the commonly invoked upper boundary condition that vertical velocity must vanish as pressure tends to zero, as well as a number of alternative conditions, is well posed. It was concluded that the vertical structure equation always has a totally discrete spectrum under the assumptions implicit in the primitive equations.

An analysis of the vertical structure equation for arbitrary thermal profiles

NASA Technical Reports Server (NTRS)

Cohn, Stephen E.; Dee, Dick P.

1987-01-01

The vertical structure equation is a singular Sturm-Liouville problem whose eigenfunctions describe the vertical dependence of the normal modes of the primitive equations linearized about a given thermal profile. The eigenvalues give the equivalent depths of the modes. The spectrum of the vertical structure equation and the appropriateness of various upper boundary conditions, both for arbitrary thermal profiles were studied. The results depend critically upon whether or not the thermal profile is such that the basic state atmosphere is bounded. In the case of a bounded atmosphere it is shown that the spectrum is always totally discrete, regardless of details of the thermal profile. For the barotropic equivalent depth, which corresponds to the lowest eigen value, upper and lower bounds which depend only on the surface temperature and the atmosphere height were obtained. All eigenfunctions are bounded, but always have unbounded first derivatives. It was proved that the commonly invoked upper boundary condition that vertical velocity must vanish as pressure tends to zero, as well as a number of alternative conditions, is well posed. It was concluded that the vertical structure equation always has a totally discrete spectrum under the assumptions implicit in the primitive equations.

Tunable hybridization of Majorana bound states at the quantum spin Hall edge

NASA Astrophysics Data System (ADS)

Keidel, Felix; Burset, Pablo; Trauzettel, Björn

2018-02-01

Confinement at the helical edge of a topological insulator is possible in the presence of proximity-induced magnetic (F) or superconducting (S) order. The interplay of both phenomena leads to the formation of localized Majorana bound states (MBS) or likewise (under certain resonance conditions) the formation of ordinary Andreev bound states (ABS). We investigate the properties of bound states in junctions composed of alternating regions of F or S barriers. Interestingly, the direction of magnetization in F regions and the relative superconducting phase between S regions can be exploited to hybridize MBS or ABS at will. We show that the local properties of MBS translate into a particular nonlocal superconducting pairing amplitude. Remarkably, the symmetry of the pairing amplitude contains information about the nature of the bound state that it stems from. Hence this symmetry can in principle be used to distinguish MBS from ABS, owing to the strong connection between local density of states and nonlocal pairing in our setup.

STATIC QUARK ANTI-QUARK FREE AND INTERNAL ENERGY IN 2-FLAVOR QCD AND BOUND STATES IN THE QGP.

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

ZANTOW, F.; KACZMAREK, O.

2005-07-25

We present results on heavy quark free energies in 2-flavour QCD. The temperature dependence of the interaction between static quark anti-quark pairs will be analyzed in terms of temperature dependent screening radii, which give a first estimate on the medium modification of (heavy quark) bound states in the quark gluon plasma. Comparing those radii to the (zero temperature) mean squared charge radii of chasmonium states indicates that the J/{Psi} may survive the phase transition as a bound state, while {chi}{sub c} and {Psi}{prime} are expected to show significant thermal modifications at temperatures close to the transition. Furthermore we will analyzemore » the relation between heavy quark free energies, entropy contributions and internal energy and discuss their relation to potential models used to analyze the melting of heavy quark bound states above the deconfinement temperature. Results of different groups and various potential models for bound states in the deconfined phase of QCD are compared.« less

Slope-aspect color shading for parametric surfaces

NASA Technical Reports Server (NTRS)

Moellering, Harold J. (Inventor); Kimerling, A. Jon (Inventor)

1991-01-01

The invention is a method for generating an image of a parametric surface, such as the compass direction toward which each surface element of terrain faces, commonly called the slope-aspect azimuth of the surface element. The method maximizes color contrast to permit easy discrimination of the magnitude, ranges, intervals or classes of a surface parameter while making it easy for the user to visualize the form of the surface, such as a landscape. The four pole colors of the opponent process color theory are utilized to represent intervals or classes at 90 degree angles. The color perceived as having maximum measured luminance is selected to portray the color having an azimuth of an assumed light source and the color showing minimum measured luminance portrays the diametrically opposite azimuth. The 90 degree intermediate azimuths are portrayed by unique colors of intermediate measured luminance, such as red and green. Colors between these four pole colors are used which are perceived as mixtures or combinations of their bounding colors and are arranged progressively between their bounding colors to have perceived proportional mixtures of the bounding colors which are proportional to the interval's angular distance from its bounding colors.

Theoretical studies of positron states and annihilation characteristics at the oxidized Cu(100) surface

NASA Astrophysics Data System (ADS)

Fazleev, N. G.; Weiss, A. H.

2013-04-01

In this work we present the results of theoretical studies of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. An ab-initio study of the electronic properties of the Cu(100) missing row reconstructed surface at various on surface and sub-surface oxygen coverages has been performed on the basis of the density functional theory (DFT) using the Dmol3 code and the generalized gradient approximation (GGA). Surface structures in calculations have been constructed by adding oxygen atoms to various surface hollow and sub-surface octahedral sites of the 0.5 monolayer (ML) missing row reconstructed phase of the Cu(100) surface with oxygen coverages ranging from 0.5 to 1.5 ML. The charge redistribution at the surface and variations in atomic structure and chemical composition of the topmost layers associated with oxidation and surface reconstruction have been found to affect the spatial extent and localization of the positron surface state wave function and annihilation probabilities of surface trapped positrons with relevant core electrons. Theoretical results are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy (PAES). It has been shown that positron annihilation probabilities with Cu 3s and 3p core electrons decrease when total (on-surface and sub-surface) oxygen coverage of the Cu(100) surface increases up to 1 ML. The calculations show that for high oxygen coverage when total oxygen coverage is 1. 5 ML the positron is not bound to the surface.

Theoretical studies of positron states and annihilation characteristics at the oxidized Cu(100) surface

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

Fazleev, N. G.; Weiss, A. H.

2013-04-19

In this work we present the results of theoretical studies of positron surface and bulk states and annihilation probabilities of surface-trapped positrons with relevant core electrons at the oxidized Cu(100) surface under conditions of high oxygen coverage. An ab-initio study of the electronic properties of the Cu(100) missing row reconstructed surface at various on surface and sub-surface oxygen coverages has been performed on the basis of the density functional theory (DFT) using the Dmol3 code and the generalized gradient approximation (GGA). Surface structures in calculations have been constructed by adding oxygen atoms to various surface hollow and sub-surface octahedral sitesmore » of the 0.5 monolayer (ML) missing row reconstructed phase of the Cu(100) surface with oxygen coverages ranging from 0.5 to 1.5 ML. The charge redistribution at the surface and variations in atomic structure and chemical composition of the topmost layers associated with oxidation and surface reconstruction have been found to affect the spatial extent and localization of the positron surface state wave function and annihilation probabilities of surface trapped positrons with relevant core electrons. Theoretical results are compared with experimental data obtained from studies of oxidation of the Cu(100) surface using positron annihilation induced Auger electron spectroscopy (PAES). It has been shown that positron annihilation probabilities with Cu 3s and 3p core electrons decrease when total (on-surface and sub-surface) oxygen coverage of the Cu(100) surface increases up to 1 ML. The calculations show that for high oxygen coverage when total oxygen coverage is 1. 5 ML the positron is not bound to the surface.« less

A model of optical trapping cold atoms using a metallic nano wire with surface plasmon effect

NASA Astrophysics Data System (ADS)

Thi Phuong Lan, Nguyen; Thi Nga, Do; Viet, Nguyen Ai

2016-06-01

In this work, we construct a new model of optical trapping cold atoms with a metallic nano wire by using surface plasmon effect generated by strong field of laser beams. Using the skin effect, we send a strong oscillated electromagnetic filed through the surface of a metallic nano wire. The local field generated by evanescent effect creates an effective attractive potential near the surface of metallic nano wires. The consideration of some possible boundary and frequency conditions might lead to non-trivial bound state solution for a cold atom. We discus also the case of the laser reflection optical trap with shell-core design, and compare our model with another recent schemes of cold atom optical traps using optical fibers and carbon nanotubes.

The realistic models of relativistic stars in f (R) = R + αR 2 gravity

NASA Astrophysics Data System (ADS)

Astashenok, Artyom V.; Odintsov, Sergei D.; de la Cruz-Dombriz, Álvaro

2017-10-01

In the context of f(R)=R+α R2 gravity, we study the existence of neutron and quark stars for various α with no intermediate approximation in the system of equations. Analysis shows that for positive α the scalar curvature does not drop to zero at the star surface (as in general relativity) but exponentially decreases with distance. Also the stellar mass bounded by star surface decreases when the value α increases. Nonetheless distant observers would observe a gravitational mass due to appearance of a so-called gravitational sphere around the star. The non-zero curvature contribution to the gravitational mass eventually is shown to compensate the stellar mass decrease for growing α’s. We perform our analysis for several equations of state including purely hadronic configurations as well as hyperons and quark stars. In all cases, we assess that the relation between the parameter α and the gravitational mass weakly depends upon the chosen equation of state. Another interesting feature is the increase of the star radius in comparison with general relativity for stars with masses close to maximal, whereas for intermediate masses 1.4 -1.6 M_⊙ the radius of star depends upon α very weakly. Also the decrease in the mass bounded by star surface may cause the surface redshift to decrease in R 2-gravity when compared to Einsteinian predictions. This effect is shown to hardly depend upon the observed gravitational mass. Finally, for negative values of α our analysis shows that outside the star the scalar curvature has damped oscillations but the contribution of the gravitational sphere into the gravitational mass increases indefinitely with radial distance putting into question the very existence of such relativistic stars.

Observation of three-photon bound states in a quantum nonlinear medium

NASA Astrophysics Data System (ADS)

Liang, Qi-Yu; Venkatramani, Aditya V.; Cantu, Sergio H.; Nicholson, Travis L.; Gullans, Michael J.; Gorshkov, Alexey V.; Thompson, Jeff D.; Chin, Cheng; Lukin, Mikhail D.; Vuletić, Vladan

2018-02-01

Bound states of massive particles, such as nuclei, atoms, or molecules, constitute the bulk of the visible world around us. By contrast, photons typically only interact weakly. We report the observation of traveling three-photon bound states in a quantum nonlinear medium where the interactions between photons are mediated by atomic Rydberg states. Photon correlation and conditional phase measurements reveal the distinct bunching and phase features associated with three-photon and two-photon bound states. Such photonic trimers and dimers possess shape-preserving wave functions that depend on the constituent photon number. The observed bunching and strongly nonlinear optical phase are described by an effective field theory of Rydberg-induced photon-photon interactions. These observations demonstrate the ability to realize and control strongly interacting quantum many-body states of light.

Transfer Function Bounds for Partial-unit-memory Convolutional Codes Based on Reduced State Diagram

NASA Technical Reports Server (NTRS)

Lee, P. J.

1984-01-01

The performance of a coding system consisting of a convolutional encoder and a Viterbi decoder is analytically found by the well-known transfer function bounding technique. For the partial-unit-memory byte-oriented convolutional encoder with m sub 0 binary memory cells and (k sub 0 m sub 0) inputs, a state diagram of 2(K) (sub 0) was for the transfer function bound. A reduced state diagram of (2 (m sub 0) +1) is used for easy evaluation of transfer function bounds for partial-unit-memory codes.

Investigation of the highest bound ro-vibrational states of H+ 3, DH+ 2, HD+ 2, D+ 3, and T+ 3: use of a non-direct product basis to compute the highest allowed J > 0 states

NASA Astrophysics Data System (ADS)

Jaquet, Ralph

2013-09-01

A Lanczos algorithm with a non-direct product basis was used to compute energy levels of H+ 3, H2D+, D2H+, D+ 3, and T+ 3 with J values as large as 46, 53, 66, 66, and 81. The energy levels are based on a modified potential surface of M. Pavanello et al. that is better adapted to the ab initio energies near the dissociation limit.

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.

Universal bounds on current fluctuations.

PubMed

Pietzonka, Patrick; Barato, Andre C; Seifert, Udo

2016-05-01

For current fluctuations in nonequilibrium steady states of Markovian processes, we derive four different universal bounds valid beyond the Gaussian regime. Different variants of these bounds apply to either the entropy change or any individual current, e.g., the rate of substrate consumption in a chemical reaction or the electron current in an electronic device. The bounds vary with respect to their degree of universality and tightness. A universal parabolic bound on the generating function of an arbitrary current depends solely on the average entropy production. A second, stronger bound requires knowledge both of the thermodynamic forces that drive the system and of the topology of the network of states. These two bounds are conjectures based on extensive numerics. An exponential bound that depends only on the average entropy production and the average number of transitions per time is rigorously proved. This bound has no obvious relation to the parabolic bound but it is typically tighter further away from equilibrium. An asymptotic bound that depends on the specific transition rates and becomes tight for large fluctuations is also derived. This bound allows for the prediction of the asymptotic growth of the generating function. Even though our results are restricted to networks with a finite number of states, we show that the parabolic bound is also valid for three paradigmatic examples of driven diffusive systems for which the generating function can be calculated using the additivity principle. Our bounds provide a general class of constraints for nonequilibrium systems.

Family of nonlocal bound entangled states

NASA Astrophysics Data System (ADS)

Yu, Sixia; Oh, C. H.

2017-03-01

Bound entanglement, being entangled yet not distillable, is essential to our understanding of the relations between nonlocality and entanglement besides its applications in certain quantum information tasks. Recently, bound entangled states that violate a Bell inequality have been constructed for a two-qutrit system, disproving a conjecture by Peres that bound entanglement is local. Here we construct this kind of nonlocal bound entangled state for all finite dimensions larger than two, making possible their experimental demonstration in most general systems. We propose a Bell inequality, based on a Hardy-type argument for nonlocality, and a steering inequality to identify their nonlocality. We also provide a family of entanglement witnesses to detect their entanglement beyond the Bell inequality and the steering inequality.

Ethanol surface chemistry on MBE-grown GaN(0001), GaOx/GaN(0001), and Ga2O3(2 \\xAF 01 )

NASA Astrophysics Data System (ADS)

Kollmannsberger, Sebastian L.; Walenta, Constantin A.; Winnerl, Andrea; Knoller, Fabian; Pereira, Rui N.; Tschurl, Martin; Stutzmann, Martin; Heiz, Ueli

2017-09-01

In this work, ethanol is used as a chemical probe to study the passivation of molecular beam epitaxy-grown GaN(0001) by surface oxidation. With a high degree of oxidation, no reaction from ethanol to acetaldehyde in temperature-programmed desorption experiments is observed. The acetaldehyde formation is attributed to a mechanism based on α -H abstraction from the dissociatively bound alcohol molecule. The reactivity is related to negatively charged surface states, which are removed upon oxidation of the GaN(0001) surface. This is compared with the Ga2O3(2 ¯ 01 ) single crystal surface, which is found to be inert for the acetaldehyde production. These results offer a toolbox to explore the surface chemistry of nitrides and oxynitrides on an atomic scale and relate their intrinsic activity to systems under ambient atmosphere.

Fermi arc plasmons in Weyl semimetals

NASA Astrophysics Data System (ADS)

Song, Justin C. W.; Rudner, Mark S.

2017-11-01

In the recently discovered Weyl semimetals, the Fermi surface may feature disjoint, open segments—the so-called Fermi arcs—associated with topological states bound to exposed crystal surfaces. Here we show that the collective dynamics of electrons near such surfaces sharply departs from that of a conventional three-dimensional metal. In magnetic systems with broken time reversal symmetry, the resulting Fermi arc plasmons (FAPs) are chiral, with dispersion relations featuring open, hyperbolic constant frequency contours. As a result, a large range of surface plasmon wave vectors can be supported at a given frequency, with corresponding group velocity vectors directed along a few specific collimated directions. Fermi arc plasmons can be probed using near-field photonics techniques, which may be used to launch highly directional, focused surface plasmon beams. The unusual characteristics of FAPs arise from the interplay of bulk and surface Fermi arc carrier dynamics and give a window into the unusual fermiology of Weyl semimetals.

Ethanol surface chemistry on MBE-grown GaN(0001), GaOx/GaN(0001), and Ga2O3(2¯01).

PubMed

Kollmannsberger, Sebastian L; Walenta, Constantin A; Winnerl, Andrea; Knoller, Fabian; Pereira, Rui N; Tschurl, Martin; Stutzmann, Martin; Heiz, Ueli

2017-09-28

In this work, ethanol is used as a chemical probe to study the passivation of molecular beam epitaxy-grown GaN(0001) by surface oxidation. With a high degree of oxidation, no reaction from ethanol to acetaldehyde in temperature-programmed desorption experiments is observed. The acetaldehyde formation is attributed to a mechanism based on α-H abstraction from the dissociatively bound alcohol molecule. The reactivity is related to negatively charged surface states, which are removed upon oxidation of the GaN(0001) surface. This is compared with the Ga 2 O 3 (2¯01) single crystal surface, which is found to be inert for the acetaldehyde production. These results offer a toolbox to explore the surface chemistry of nitrides and oxynitrides on an atomic scale and relate their intrinsic activity to systems under ambient atmosphere.

Level crossings in the ionization of H(2) Rydberg molecules at a metal surface.

PubMed

McCormack, E A; Ford, M S; Softley, T P

2010-10-28

The ionization of H(2) Rydberg states at a metal surface is investigated using a molecular beam incident at grazing incidence on a gold surface. The H(2) molecules, excited by stepwise two-color laser excitation, are selected in each of the accessible Stark eigenstates of the N(+) = 2, n = 17 Rydberg manifold in turn and the ionization at the surface is characterized by applying a field to extract the ions formed. Profiles of extracted ion signal versus applied field show resonances that can be simulated by assuming an enhancement of surface ionization at fields corresponding to energy-level crossings between the populated N(+) = 2 manifold and the near-degenerate N(+) = 0 Stark manifolds. It is concluded that the slow (microsecond time scale) rotation-electronic energy transfer to N(+) = 0 states occurring at these crossings takes place in the time interval following application of the field ramp when the molecule is still distant from, and unperturbed by, the surface. However, the energy levels are strongly perturbed by image-dipole interactions as the molecule approaches close to the surface, leading to additional energy-level crossings. Adiabatic behavior at such crossings affects the intensity of the observed resonances in the surface ionization signal but not their field positions. Resonances are also observed in the surface ionization profiles at fields above the field-ionization threshold; some of these show asymmetric "Fano-type" line shapes due to quantum interference in the nonradiative coupling to degenerate bound and continuum states.

The influence of dissolved and surface-bound humic acid on the toxicity of TiO₂ nanoparticles to Chlorella sp.

PubMed

Lin, Daohui; Ji, Jing; Long, Zhifeng; Yang, Kun; Wu, Fengchang

2012-09-15

NOM is likely to coat TiO₂ nanoparticles (nano-TiO₂) discharged into the aquatic environment and influence the nanotoxicity to aquatic organisms, which however has not been well investigated. This study explored the influence of nanoparticle surface-bound humic acid (HA, as a model NOM) as well as dissolved HA on the toxicity of nano-TiO₂ to Chlorella sp., with a specific focus on adhesion of the nanoparticles to the algae. Results showed that nano-TiO₂ and the dissolved HA could inhibit the algal growth with an IC₅₀ of 4.9 and 8.4 mg L⁻¹, respectively, while both dissolved and nanoparticle surface-bound HA could significantly alleviate the algal toxicity of nano-TiO₂. IC₅₀ of nano-TiO₂ increased to 18 mg L⁻¹ in the presence of 5 mg L⁻¹ of the dissolved HA and to 48 mg L⁻¹ as the result of surface-saturation by HA. Co-precipitation experiment and transmission electron microscopy observation revealed that both dissolved and nanoparticle surface-bound HA prevented the adhesion of nano-TiO₂ to the algal cells due to the increased electrosteric repulsion. The generation of intracellular reactive oxygen species (ROS) was significantly limited by the dissolved and nanoparticle surface-bound HA. The prevention of adhesion and inhibition of ROS generation could account for the HA-mitigated nanotoxicity. Copyright © 2012 Elsevier Ltd. All rights reserved.

Proton-Induced Trap States, Injection and Recombination Dynamics in Water-Splitting Dye-Sensitized Photoelectrochemical Cells.

PubMed

McCool, Nicholas S; Swierk, John R; Nemes, Coleen T; Saunders, Timothy P; Schmuttenmaer, Charles A; Mallouk, Thomas E

2016-07-06

Water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) utilize a sensitized metal oxide and a water oxidation catalyst in order to generate hydrogen and oxygen from water. Although the Faradaic efficiency of water splitting is close to unity, the recombination of photogenerated electrons with oxidized dye molecules causes the quantum efficiency of these devices to be low. It is therefore important to understand recombination mechanisms in order to develop strategies to minimize them. In this paper, we discuss the role of proton intercalation in the formation of recombination centers. Proton intercalation forms nonmobile surface trap states that persist on time scales that are orders of magnitude longer than the electron lifetime in TiO2. As a result of electron trapping, recombination with surface-bound oxidized dye molecules occurs. We report a method for effectively removing the surface trap states by mildly heating the electrodes under vacuum, which appears to primarily improve the injection kinetics without affecting bulk trapping dynamics, further stressing the importance of proton control in WS-DSPECs.

Single-particle trajectories reveal two-state diffusion-kinetics of hOGG1 proteins on DNA.

PubMed

Vestergaard, Christian L; Blainey, Paul C; Flyvbjerg, Henrik

2018-03-16

We reanalyze trajectories of hOGG1 repair proteins diffusing on DNA. A previous analysis of these trajectories with the popular mean-squared-displacement approach revealed only simple diffusion. Here, a new optimal estimator of diffusion coefficients reveals two-state kinetics of the protein. A simple, solvable model, in which the protein randomly switches between a loosely bound, highly mobile state and a tightly bound, less mobile state is the simplest possible dynamic model consistent with the data. It yields accurate estimates of hOGG1's (i) diffusivity in each state, uncorrupted by experimental errors arising from shot noise, motion blur and thermal fluctuations of the DNA; (ii) rates of switching between states and (iii) rate of detachment from the DNA. The protein spends roughly equal time in each state. It detaches only from the loosely bound state, with a rate that depends on pH and the salt concentration in solution, while its rates for switching between states are insensitive to both. The diffusivity in the loosely bound state depends primarily on pH and is three to ten times higher than in the tightly bound state. We propose and discuss some new experiments that take full advantage of the new tools of analysis presented here.

Upper bounds on the error probabilities and asymptotic error exponents in quantum multiple state discrimination

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

Audenaert, Koenraad M. R., E-mail: koenraad.audenaert@rhul.ac.uk; Department of Physics and Astronomy, University of Ghent, S9, Krijgslaan 281, B-9000 Ghent; Mosonyi, Milán, E-mail: milan.mosonyi@gmail.com

2014-10-01

We consider the multiple hypothesis testing problem for symmetric quantum state discrimination between r given states σ₁, …, σ{sub r}. By splitting up the overall test into multiple binary tests in various ways we obtain a number of upper bounds on the optimal error probability in terms of the binary error probabilities. These upper bounds allow us to deduce various bounds on the asymptotic error rate, for which it has been hypothesized that it is given by the multi-hypothesis quantum Chernoff bound (or Chernoff divergence) C(σ₁, …, σ{sub r}), as recently introduced by Nussbaum and Szkoła in analogy with Salikhov'smore » classical multi-hypothesis Chernoff bound. This quantity is defined as the minimum of the pairwise binary Chernoff divergences min{sub j« less

Influence of carbon source on cell surface topology of Thermomonospora curvata.

PubMed Central

Hostalka, F; Moultrie, A; Stutzenberger, F

1992-01-01

The appearance of cell surface protuberances in Thermomonospora curvata correlated with cell-bound exoenzymes which could be removed by brief sonication. Mycelia grown on cellulose or xylan had numerous protuberances and retained 20 to 25% of endoglucanase and endoxylanase at cell surfaces, while those grown on pectin or starch had few protuberances and negligible bound pectinase or amylase. Images PMID:1400256

The nucleotide-free state of heterotrimeric G proteins α-subunit adopts a highly stable conformation.

PubMed

Andhirka, Sai Krishna; Vignesh, Ravichandran; Aradhyam, Gopala Krishna

2017-08-01

Deciphering the mechanism of activation of heterotrimeric G proteins by their cognate receptors continues to be an intriguing area of research. The recently solved crystal structure of the ternary complex captured the receptor-bound α-subunit in an open conformation, without bound nucleotide has improved our understanding of the activation process. Despite these advancements, the mechanism by which the receptor causes GDP release from the α-subunit remains elusive. To elucidate the mechanism of activation, we studied guanine nucleotide-induced structural stability of the α-subunit (in response to thermal/chaotrope-mediated stress). Inherent stabilities of the inactive (GDP-bound) and active (GTP-bound) forms contribute antagonistically to the difference in conformational stability whereas the GDP-bound protein is able to switch to a stable intermediate state, GTP-bound protein loses this ability. Partial perturbation of the protein fold reveals the underlying influence of the bound nucleotide providing an insight into the mechanism of activation. An extra stable, pretransition intermediate, 'empty pocket' state (conformationally active-state like) in the unfolding pathway of GDP-bound protein mimics a gating system - the activation process having to overcome this stable intermediate state. We demonstrate that a relatively more complex conformational fold of the GDP-bound protein is at the core of the gating system. We report capturing this threshold, 'metastable empty pocket' conformation (the gate) of α-subunit of G protein and hypothesize that the receptor activates the G protein by enabling it to achieve this structure through mild structural perturbation. © 2017 Federation of European Biochemical Societies.

Binding and orientation of fibronectin on polystyrene surfaces using immobilized bacterial adhesin-related peptides.

PubMed

Klueh, U; Bryers, J D; Kreutzer, D L

2003-10-01

Fibronectin (FN) is known to bind to bacteria via high affinity receptors on bacterial surfaces known as adhesins. The binding of bacteria to FN is thought to have a key role in foreign device associated infections. For example, previous studies have indicated that Staphylococcus aureus adhesins bind to the 29 kDa NH(3) terminus end of FN, and thereby promote bacteria adherence to surfaces. Recently, the peptide sequences within the S. aureus adhesin molecule that are responsible for FN binding have been identified. Based on these observations, we hypothesize that functional FN can be bound and specifically oriented on polystyrene surfaces using bacterial adhesin-related (BRP-A) peptide. We further hypothesize that monoclonal antibodies that react with specific epitopes on the FN can be used to quantify both FN binding and orientation on these surfaces. Based on this hypothesis, we initiated a systematic investigation of the binding and orientation of FN on polystyrene surfaces using BRP-A peptide. To test this hypothesis, the binding and orientation of the FN to immobilized BRP-A was quantified using (125)I-FN, and monoclonal antibodies. (125)I-FN was used to quantitate FN binding to peptide-coated polystyrene surfaces. The orientation of bound FN was demonstrated by the use of monoclonal antibodies, which are reactive with the amine (N) or carboxyl (C) termini of the FN. The results of our studies demonstrated that when the BRP-A peptide was used to bind FN to surfaces that: 1. functional FN was bound to the peptide; 2. anti-C terminus antibodies bound to the peptide FN; and 3. only limited binding of anti-N terminus antibodies to peptide-bound FN occurred. We believe that the data that indicate an enhanced binding of anti-C antibodies reactive to anti-N antibodies are a result of the FN binding in an oriented manner with the N termini of FN bound tightly to the BRP-A on the polystyrene surface. Copyright 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 36-43, 2003

A solid-state NMR study of the dynamics and interactions of phenylalanine rings in a statherin fragment bound to hydroxyapatite crystals.

PubMed

Gibson, James M; Popham, Jennifer M; Raghunathan, Vinodhkumar; Stayton, Patrick S; Drobny, Gary P

2006-04-26

Extracellular matrix proteins regulate hard tissue growth by acting as adhesion sites for cells, by triggering cell signaling pathways, and by directly regulating the primary and/or secondary crystallization of hydroxyapatite, the mineral component of bone and teeth. Despite the key role that these proteins play in the regulation of hard tissue growth in humans, the exact mechanism used by these proteins to recognize mineral surfaces is poorly understood. Interactions between mineral surfaces and proteins very likely involve specific contacts between the lattice and the protein side chains, so elucidation of the nature of interactions between protein side chains and their corresponding inorganic mineral surfaces will provide insight into the recognition and regulation of hard tissue growth. Isotropic chemical shifts, chemical shift anisotropies (CSAs), NMR line-width information, (13)C rotating frame relaxation measurements, as well as direct detection of correlations between (13)C spins on protein side chains and (31)P spins in the crystal surface with REDOR NMR show that, in the peptide fragment derived from the N-terminal 15 amino acids of salivary statherin (i.e., SN-15), the side chain of the phenylalanine nearest the C-terminus of the peptide (F14) is dynamically constrained and oriented near the surface, whereas the side chain of the phenylalanine located nearest to the peptide's N-terminus (F7) is more mobile and is oriented away from the hydroxyapatite surface. The relative dynamics and proximities of F7 and F14 to the surface together with prior data obtained for the side chain of SN-15's unique lysine (i.e., K6) were used to construct a new picture for the structure of the surface-bound peptide and its orientation to the crystal surface.

Studies of heat source driven natural convection. Ph.D. Thesis. Technical Report, Jul. 1974 - Aug. 1975

NASA Technical Reports Server (NTRS)

Kulacki, F. A.; Emara, A. A.

1975-01-01

Natural convection energy transport in a horizontal layer of internally heated fluid was measured for Rayleigh numbers from 1890 to 2.17 x 10 to the 12th power. The fluid layer is bounded below by a rigid zero-heat-flux surface and above by a rigid constant-temperature surface. Joule heating by an alternating current passing horizontally through the layer provides the uniform volumetric energy source. The overall steady-state heat transfer coefficient at the upper surface was determined by measuring the temperature difference across the layer and power input to the fluid. The correlation between the Nusselt and Rayleigh numbers for the data of the present study and the data of the Kulacki study is given.

Handshake electron transfer from hydrogen Rydberg atoms incident at a series of metallic thin films

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

Gibbard, J. A.; Softley, T. P.

2016-06-21

Thin metallic films have a 1D quantum well along the surface normal direction, which yields particle-in-a-box style electronic quantum states. However the quantum well is not infinitely deep and the wavefunctions of these states penetrate outside the surface where the electron is bound by its own image-charge attraction. Therefore a series of discrete, vacant states reach out from the thin film into the vacuum increasing the probability of electron transfer from an external atom or molecule to the thin film, especially for the resonant case where the quantum well energy matches that of the atom. We show that “handshake” electronmore » transfer from a highly excited Rydberg atom to these thin-film states is experimentally measurable. Thicker films have a wider 1D box, changing the energetic distribution and image-state contribution to the thin film wavefunctions, resulting in more resonances. Calculations successfully predict the number of resonances and the nature of the thin-film wavefunctions for a given film thickness.« less

Feshbach resonances in the exit channel of the F + CH3OH → HF + CH3O reaction observed using transition-state spectroscopy

NASA Astrophysics Data System (ADS)

Weichman, Marissa L.; Devine, Jessalyn A.; Babin, Mark C.; Li, Jun; Guo, Lifen; Ma, Jianyi; Guo, Hua; Neumark, Daniel M.

2017-10-01

The transition state governs how chemical bonds form and cleave during a chemical reaction and its direct characterization is a long-standing challenge in physical chemistry. Transition state spectroscopy experiments based on negative-ion photodetachment provide a direct probe of the vibrational structure and metastable resonances that are characteristic of the reactive surface. Dynamical resonances are extremely sensitive to the topography of the reactive surface and provide an exceptional point of comparison with theory. Here we study the seven-atom F + CH3OH → HF + CH3O reaction using slow photoelectron velocity-map imaging spectroscopy of cryocooled CH3OHF- anions. These measurements reveal spectral features associated with a manifold of vibrational Feshbach resonances and bound states supported by the post-transition state potential well. Quantum dynamical calculations yield excellent agreement with the experimental results, allow the assignment of spectral structure and demonstrate that the key dynamics of complex bimolecular reactions can be captured with a relatively simple theoretical framework.

Feshbach resonances in the exit channel of the F + CH3OH → HF + CH3O reaction observed using transition-state spectroscopy.

PubMed

Weichman, Marissa L; DeVine, Jessalyn A; Babin, Mark C; Li, Jun; Guo, Lifen; Ma, Jianyi; Guo, Hua; Neumark, Daniel M

2017-10-01

The transition state governs how chemical bonds form and cleave during a chemical reaction and its direct characterization is a long-standing challenge in physical chemistry. Transition state spectroscopy experiments based on negative-ion photodetachment provide a direct probe of the vibrational structure and metastable resonances that are characteristic of the reactive surface. Dynamical resonances are extremely sensitive to the topography of the reactive surface and provide an exceptional point of comparison with theory. Here we study the seven-atom F + CH 3 OH → HF + CH 3 O reaction using slow photoelectron velocity-map imaging spectroscopy of cryocooled CH 3 OHF - anions. These measurements reveal spectral features associated with a manifold of vibrational Feshbach resonances and bound states supported by the post-transition state potential well. Quantum dynamical calculations yield excellent agreement with the experimental results, allow the assignment of spectral structure and demonstrate that the key dynamics of complex bimolecular reactions can be captured with a relatively simple theoretical framework.

Study of Proton Transfer in E. Coli Photolyase

NASA Astrophysics Data System (ADS)

Zhang, Meng; Liu, Zheyun; Li, Jiang; Wang, Lijuan; Zhong, Dongping

2013-06-01

Photolyase is a flavoprotein which utilizes blue-light energy to repair UV-light damaged DNA. The catalytic cofactor of photolyase, flavin adenine dinucleotide (FAD), has five redox states. Conversions between these redox states involve intraprotein electron transfer and proton transfer, which play important role in protein function. Here we systematically studied proton transfer in E. coli photolyase in vitro by site-directed mutagenesis and steady-state UV-vis spectroscopy, and proposed the proton channel in photolyase. We found that in the mutant N378C/E363L, proton channel was completely eliminated when DNA substrate was bound to the protein. Proton is suggested to be transported from protein surface to FAD by two pathways: the proton relay pathway through E363 and surface water to N378 and then to FAD; and the proton diffusion pathway through the substrate binding pocket. In addition, reaction kinetics of conversions between the redox states was then solved and redox potentials of the redox states were determined. These results described a complete picture of FAD redox changes, which are fundamental to the functions of all flavoenzymes.

Quantum computation with realistic magic-state factories

NASA Astrophysics Data System (ADS)

O'Gorman, Joe; Campbell, Earl T.

2017-03-01

Leading approaches to fault-tolerant quantum computation dedicate a significant portion of the hardware to computational factories that churn out high-fidelity ancillas called magic states. Consequently, efficient and realistic factory design is of paramount importance. Here we present the most detailed resource assessment to date of magic-state factories within a surface code quantum computer, along the way introducing a number of techniques. We show that the block codes of Bravyi and Haah [Phys. Rev. A 86, 052329 (2012), 10.1103/PhysRevA.86.052329] have been systematically undervalued; we track correlated errors both numerically and analytically, providing fidelity estimates without appeal to the union bound. We also introduce a subsystem code realization of these protocols with constant time and low ancilla cost. Additionally, we confirm that magic-state factories have space-time costs that scale as a constant factor of surface code costs. We find that the magic-state factory required for postclassical factoring can be as small as 6.3 million data qubits, ignoring ancilla qubits, assuming 10-4 error gates and the availability of long-range interactions.

Magnetoconductance signatures of chiral domain-wall bound states in magnetic topological insulators

NASA Astrophysics Data System (ADS)

Tiwari, Kunal L.; Coish, W. A.; Pereg-Barnea, T.

2017-12-01

Recent magnetoconductance measurements performed on magnetic topological insulator candidates have revealed butterfly-shaped hysteresis. This hysteresis has been attributed to the formation of gapless chiral domain-wall bound states during a magnetic-field sweep. We treat this phenomenon theoretically, providing a link between microscopic magnetization dynamics and butterfly hysteresis in magnetoconductance. Further, we illustrate how a spatially resolved conductance measurement can probe the most striking feature of the domain-wall bound states: their chirality. This work establishes a regime where a definitive link between butterfly hysteresis in longitudinal magneto-conductance and domain-wall bound states can be made. This analysis provides an important tool for the identification of magnetic topological insulators.

Cosmological implications of Dark Matter bound states

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

Mitridate, Andrea; Redi, Michele; Smirnov, Juri

2017-05-01

We present generic formulæ for computing how Sommerfeld corrections together with bound-state formation affects the thermal abundance of Dark Matter with non-abelian gauge interactions. We consider DM as a fermion 3plet (wino) or 5plet under SU(2) {sub L} . In the latter case bound states raise to 11.5 TeV the DM mass required to reproduce the cosmological DM abundance and give indirect detection signals such as (for this mass) a dominant γ-line around 70 GeV. Furthermore, we consider DM co-annihilating with a colored particle, such as a squark or a gluino, finding that bound state effects are especially relevant inmore » the latter case.« less

Probing Gαi1 Protein Activation at Single Amino Acid Resolution

PubMed Central

Sun, Dawei; Maeda, Shoji; Matkovic, Milos; Mendieta, Sandro; Mayer, Daniel; Dawson, Roger; Schertler, Gebhard F.X.; Madan Babu, M.; Veprintsev, Dmitry B.

2016-01-01

We present comprehensive single amino acid resolution maps of the residues stabilising the human Gαi1 subunit in nucleotide- and receptor-bound states. We generated these maps by measuring the effects of alanine mutations on the stability of Gαi1 and of the rhodopsin-Gαi1 complex. We identified stabilization clusters in the GTPase and helical domains responsible for structural integrity and the conformational changes associated with activation. In activation cluster I, helices α1 and α5 pack against strands β1-3 to stabilize the nucleotide-bound states. In the receptor-bound state, these interactions are replaced by interactions between α5 and strands β4-6. Key residues in this cluster are Y320, crucial for the stabilization of the receptor-bound state, and F336, which stabilizes nucleotide-bound states. Destabilization of helix α1, caused by rearrangement of this activation cluster, leads to the weakening of the inter-domain interface and release of GDP. PMID:26258638

Lower bounds of concurrence for N-qubit systems and the detection of k-nonseparability of multipartite quantum systems

NASA Astrophysics Data System (ADS)

Qi, Xianfei; Gao, Ting; Yan, Fengli

2017-01-01

Concurrence, as one of the entanglement measures, is a useful tool to characterize quantum entanglement in various quantum systems. However, the computation of the concurrence involves difficult optimizations and only for the case of two qubits, an exact formula was found. We investigate the concurrence of four-qubit quantum states and derive analytical lower bound of concurrence using the multiqubit monogamy inequality. It is shown that this lower bound is able to improve the existing bounds. This approach can be generalized to arbitrary qubit systems. We present an exact formula of concurrence for some mixed quantum states. For even-qubit states, we derive an improved lower bound of concurrence using a monogamy equality for qubit systems. At the same time, we show that a multipartite state is k-nonseparable if the multipartite concurrence is larger than a constant related to the value of k, the qudit number and the dimension of the subsystems. Our results can be applied to detect the multipartite k-nonseparable states.

Generalized Hofmann quantum process fidelity bounds for quantum filters

NASA Astrophysics Data System (ADS)

Sedlák, Michal; Fiurášek, Jaromír

2016-04-01

We propose and investigate bounds on the quantum process fidelity of quantum filters, i.e., probabilistic quantum operations represented by a single Kraus operator K . These bounds generalize the Hofmann bounds on the quantum process fidelity of unitary operations [H. F. Hofmann, Phys. Rev. Lett. 94, 160504 (2005), 10.1103/PhysRevLett.94.160504] and are based on probing the quantum filter with pure states forming two mutually unbiased bases. Determination of these bounds therefore requires far fewer measurements than full quantum process tomography. We find that it is particularly suitable to construct one of the probe bases from the right eigenstates of K , because in this case the bounds are tight in the sense that if the actual filter coincides with the ideal one, then both the lower and the upper bounds are equal to 1. We theoretically investigate the application of these bounds to a two-qubit optical quantum filter formed by the interference of two photons on a partially polarizing beam splitter. For an experimentally convenient choice of factorized input states and measurements we study the tightness of the bounds. We show that more stringent bounds can be obtained by more sophisticated processing of the data using convex optimization and we compare our methods for different choices of the input probe states.

Nonmagnetic impurity resonances as a signature of sign-reversal pairing in FeAs-based superconductors.

PubMed

Zhang, Degang

2009-10-30

The energy band structure of FeAs-based superconductors is fitted by a tight-binding model with two Fe ions per unit cell and two degenerate orbitals per Fe ion. Based on this, superconductivity with extended s-wave pairing symmetry of the form cosk(x)+cosk(y) is examined. The local density of states near an impurity is also investigated by using the T-matrix approach. For the nonmagnetic scattering potential, we found that there exist two major resonances inside the gap. The height of the resonance peaks depends on the strength of the impurity potential. These in-gap resonances are originated in the Andreev's bound states due to the quasiparticle scattering between the hole Fermi surfaces around Gamma point with positive order parameter and the electron Fermi surfaces around M point with negative order parameter.

Strong Dependence of Hydration State of F-Actin on the Bound Mg(2+)/Ca(2+) Ions.

PubMed

Suzuki, Makoto; Imao, Asato; Mogami, George; Chishima, Ryotaro; Watanabe, Takahiro; Yamaguchi, Takaya; Morimoto, Nobuyuki; Wazawa, Tetsuichi

2016-07-21

Understanding of the hydration state is an important issue in the chemomechanical energetics of versatile biological functions of polymerized actin (F-actin). In this study, hydration-state differences of F-actin by the bound divalent cations are revealed through precision microwave dielectric relaxation (DR) spectroscopy. G- and F-actin in Ca- and Mg-containing buffer solutions exhibit dual hydration components comprising restrained water with DR frequency f2 (fw). The hydration state of F-actin is strongly dependent on the ionic composition. In every buffer tested, the HMW signal Dhyme (≡ (f1 - fw)δ1/(fwδw)) of F-actin is stronger than that of G-actin, where δw is DR-amplitude of bulk solvent and δ1 is that of HMW in a fixed-volume ellipsoid containing an F-actin and surrounding water in solution. Dhyme value of F-actin in Ca2.0-buffer (containing 2 mM Ca(2+)) is markedly higher than in Mg2.0-buffer (containing 2 mM Mg(2+)). Moreover, in the presence of 2 mM Mg(2+), the hydration state of F-actin is changed by adding a small fraction of Ca(2+) (∼0.1 mM) and becomes closer to that of the Ca-bound form in Ca2.0-buffer. This is consistent with the results of the partial specific volume and the Cotton effect around 290 nm in the CD spectra, indicating a change in the tertiary structure and less apparent change in the secondary structure of actin. The number of restrained water molecules per actin (N2) is estimated to be 1600-2100 for Ca2.0- and F-buffer and ∼2500 for Mg2.0-buffer at 10-15 °C. These numbers are comparable to those estimated from the available F-actin atomic structures as in the first water layer. The number of HMW molecules is roughly explained by the volume between the equipotential surface of -kT/2e and the first water layer of the actin surface by solving the Poisson-Boltzmann equation using UCSF Chimera.

Symmetry-breaking instability of quadratic soliton bound states

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

Delque, Michaeel; Departement d'Optique P.M. Duffieux, Institut FEMTO-ST, Universite de Franche-Comte, CNRS UMR 6174, F-25030 Besancon; Fanjoux, Gil

We study both numerically and experimentally two-dimensional soliton bound states in quadratic media and demonstrate their symmetry-breaking instability. The experiment is performed in a potassium titanyl phosphate crystal in a type-II configuration. The bound state is generated by the copropagation of the antisymmetric fundamental beam locked in phase with the symmetrical second harmonic one. Experimental results are in good agreement with numerical simulations of the nonlinear wave equations.

Electrostatic Rate Enhancement and Transient Complex of Protein-Protein Association

PubMed Central

Alsallaq, Ramzi; Zhou, Huan-Xiang

2012-01-01

The association of two proteins is bounded by the rate at which they, via diffusion, find each other while in appropriate relative orientations. Orientational constraints restrict this rate to ~105 – 106 M−1s−1. Proteins with higher association rates generally have complementary electrostatic surfaces; proteins with lower association rates generally are slowed down by conformational changes upon complex formation. Previous studies (Zhou, Biophys. J. 1997;73:2441–2445) have shown that electrostatic enhancement of the diffusion-limited association rate can be accurately modeled by kD = kD0 exp(−*/ kBT), where kD and kD0 are the rates in the presence and absence of electrostatic interactions, respectively, * is the average electrostatic interaction energy in a “transient-complex” ensemble, and kBT is thermal energy. The transient-complex ensemble separates the bound state from the unbound state. Predictions of the transient-complex theory on four protein complexes were found to agree well with experiment when the electrostatic interaction energy was calculated with the linearized Poisson-Boltzmann (PB) equation (Alsallaq and Zhou, Structure 2007, 15:215–224). Here we show that the agreement is further improved when the nonlinear PB equation is used. These predictions are obtained with the dielectric boundary defined as the protein van der Waals surface. When the dielectric boundary is instead specified as the molecular surface, electrostatic interactions in the transient complex become repulsive and are thus predicted to retard association. Together these results demonstrate that the transient-complex theory is predictive of electrostatic rate enhancement and can help parameterize PB calculations. PMID:17932929

Long-distance measurement-device-independent quantum key distribution with coherent-state superpositions.

PubMed

Yin, H-L; Cao, W-F; Fu, Y; Tang, Y-L; Liu, Y; Chen, T-Y; Chen, Z-B

2014-09-15

Measurement-device-independent quantum key distribution (MDI-QKD) with decoy-state method is believed to be securely applied to defeat various hacking attacks in practical quantum key distribution systems. Recently, the coherent-state superpositions (CSS) have emerged as an alternative to single-photon qubits for quantum information processing and metrology. Here, in this Letter, CSS are exploited as the source in MDI-QKD. We present an analytical method that gives two tight formulas to estimate the lower bound of yield and the upper bound of bit error rate. We exploit the standard statistical analysis and Chernoff bound to perform the parameter estimation. Chernoff bound can provide good bounds in the long-distance MDI-QKD. Our results show that with CSS, both the security transmission distance and secure key rate are significantly improved compared with those of the weak coherent states in the finite-data case.

The limits of the nuclear landscape explored by the relativistic continuum Hartree-Bogoliubov theory

NASA Astrophysics Data System (ADS)

Xia, X. W.; Lim, Y.; Zhao, P. W.; Liang, H. Z.; Qu, X. Y.; Chen, Y.; Liu, H.; Zhang, L. F.; Zhang, S. Q.; Kim, Y.; Meng, J.

2018-05-01

The ground-state properties of nuclei with 8 ⩽ Z ⩽ 120 from the proton drip line to the neutron drip line have been investigated using the spherical relativistic continuum Hartree-Bogoliubov (RCHB) theory with the relativistic density functional PC-PK1. With the effects of the continuum included, there are totally 9035 nuclei predicted to be bound, which largely extends the existing nuclear landscapes predicted with other methods. The calculated binding energies, separation energies, neutron and proton Fermi surfaces, root-mean-square (rms) radii of neutron, proton, matter, and charge distributions, ground-state spins and parities are tabulated. The extension of the nuclear landscape obtained with RCHB is discussed in detail, in particular for the neutron-rich side, in comparison with the relativistic mean field calculations without pairing correlations and also other predicted landscapes. It is found that the coupling between the bound states and the continuum due to the pairing correlations plays an essential role in extending the nuclear landscape. The systematics of the separation energies, radii, densities, potentials and pairing energies of the RCHB calculations are also discussed. In addition, the α-decay energies and proton emitters based on the RCHB calculations are investigated.

Comparative Effect of an Addition of a Surface Term to Woods-Saxon Potential on Thermodynamics of a Nucleon

NASA Astrophysics Data System (ADS)

Lütfüoğlu, B. C.

2018-01-01

In this study, we reveal the difference between Woods-Saxon (WS) and Generalized Symmetric Woods-Saxon (GSWS) potentials in order to describe the physical properties of a nucleon, by means of solving Schrödinger equation for the two potentials. The additional term squeezes the WS potential well, which leads an upward shift in the spectrum, resulting in a more realistic picture. The resulting GSWS potential does not merely accommodate extra quasi bound states, but also has modified bound state spectrum. As an application, we apply the formalism to a real problem, an α particle confined in Bohrium-270 nucleus. The thermodynamic functions Helmholtz energy, entropy, internal energy, specific heat of the system are calculated and compared for both wells. The internal energy and the specific heat capacity increase as a result of upward shift in the spectrum. The shift of the Helmholtz free energy is a direct consequence of the shift of the spectrum. The entropy decreases because of a decrement in the number of available states. Supported by the Turkish Science and Research Council (TÜBİTAK) and Akdeniz University

Antiproton--neutron bound state

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

Ju, I.; Tomozawa, Y.

1972-08-01

The possibility of an antiproton-neutron bound state for explaining a narrow peak which was found recently in the experiment p + n yields 4 pi and 6 pi is discussed. It is pointed out that the state is likely to be a /sup 1/P/ sub 1/ state or a higher angular momentum state. (auth)

Pre-polishing on a CNC platform with bound abrasive contour tools

NASA Astrophysics Data System (ADS)

Schoeffer, Adrienne E.

2003-05-01

Deterministic micorgrinding (DMG) of optical glasses and ceramics is the commercial manufacturing process of choice to shape glass surfaces prior to final finishing. This process employs rigid bound matrix diamond tooling resulting in surface roughness values of 3-51.tm peak to valley and 100-400nm rms, as well as mid-spatial frequency tool marks that require subsequent removal in secondary finishing steps. The ability to pre-polish optical surfaces within the grinding platform would reduce final finishing process times. Bound abrasive contour wheels containing cerium oxide, alumina or zirconia abrasives were constructed with an epoxy matrix. The effects of abrasive type, composition, and erosion promoters were examined for tool hardness (Shore D), and tested with commercial optical glasses in an OptiproTM CNC grinding platform. Metrology protocols were developed to examine tool wear and subsequent surface roughness. Work is directed to demonstrating effective material removal, improved surface roughness and cutter mark removal.

Prepolishing on a CNC platform with bound abrasive contour tools

NASA Astrophysics Data System (ADS)

Schoeffler, Adrienne E.; Gregg, Leslie L.; Schoen, John M.; Fess, Edward M.; Hakiel, Michael; Jacobs, Stephen D.

2003-05-01

Deterministic microgrinding (DMG) of optical glasses and ceramics is the commercial manufacturing process of choice to shape glass surfaces prior to final finishing. This process employs rigid bound matrix diamond tooling resulting in surface roughness values of 3-5μm peak to valley and 100-400nm rms, as well as mid-spatial frequency tool marks that require subsequent removal in secondary finishing steps. The ability to pre-polish optical surfaces within the grinding platform would reduce final finishing process times. Bound abrasive contour wheels containing cerium oxide, alumina or zirconia abrasives were constructed with an epoxy matrix. The effects of abrasive type, composition, and erosion promoters were examined for tool hardness (Shore D), and tested with commercial optical glasses in an Optipro CNC grinding platform. Metrology protocols were developed to examine tool wear and subsequent surface roughness. Work is directed to demonstrating effective material removal, improved surface roughness and cutter mark removal.

Increasing the potency of an alhydrogel-formulated anthrax vaccine by minimizing antigen-adjuvant interactions.

PubMed

Watkinson, Allan; Soliakov, Andrei; Ganesan, Ashok; Hirst, Karie; Lebutt, Chris; Fleetwood, Kelly; Fusco, Peter C; Fuerst, Thomas R; Lakey, Jeremy H

2013-11-01

Aluminum salts are the most widely used vaccine adjuvants, and phosphate is known to modulate antigen-adjuvant interactions. Here we report an unexpected role for phosphate buffer in an anthrax vaccine (SparVax) containing recombinant protective antigen (rPA) and aluminum oxyhydroxide (AlOH) adjuvant (Alhydrogel). Phosphate ions bind to AlOH to produce an aluminum phosphate surface with a reduced rPA adsorption coefficient and binding capacity. However, these effects continued to increase as the free phosphate concentration increased, and the binding of rPA changed from endothermic to exothermic. Crucially, phosphate restored the thermostability of bound rPA so that it resembled the soluble form, even though it remained tightly bound to the surface. Batches of vaccine with either 0.25 mM (subsaturated) or 4 mM (saturated) phosphate were tested in a disease model at batch release, which showed that the latter was significantly more potent. Both formulations retained their potency for 3 years. The strongest aluminum adjuvant effects are thus likely to be via weakly attached or easily released native-state antigen proteins.

A Four-parameter Budyko Equation for Mean Annual Water Balance

NASA Astrophysics Data System (ADS)

Tang, Y.; Wang, D.

2016-12-01

In this study, a four-parameter Budyko equation for long-term water balance at watershed scale is derived based on the proportionality relationships of the two-stage partitioning of precipitation. The four-parameter Budyko equation provides a practical solution to balance model simplicity and representation of dominated hydrologic processes. Under the four-parameter Budyko framework, the key hydrologic processes related to the lower bound of Budyko curve are determined, that is, the lower bound is corresponding to the situation when surface runoff and initial evaporation not competing with base flow generation are zero. The derived model is applied to 166 MOPEX watersheds in United States, and the dominant controlling factors on each parameter are determined. Then, four statistical models are proposed to predict the four model parameters based on the dominant controlling factors, e.g., saturated hydraulic conductivity, fraction of sand, time period between two storms, watershed slope, and Normalized Difference Vegetation Index. This study shows a potential application of the four-parameter Budyko equation to constrain land-surface parameterizations in ungauged watersheds or general circulation models.

Studies of minute quantities of natural abundance molecules using 2D heteronuclear correlation spectroscopy under 100kHz MAS

DOE PAGES

Nishiyama, Y.; Kobayashi, T.; Malon, M.; ...

2015-02-16

Two-dimensional 1H{ 13C} heteronuclear correlation solid-state NMR spectra of naturally abundant solid materials are presented, acquired using the 0.75-mm magic angle spinning (MAS) probe at spinning rates up to 100 kHz. In spite of the miniscule sample volume (290 nL), high-quality HSQC-type spectra of bulk samples as well as surface-bound molecules can be obtained within hours of experimental time. The experiments are compared with those carried out at 40 kHz MAS using a 1.6-mm probe, which offered higher overall sensitivity due to a larger rotor volume. The benefits of ultrafast MAS in such experiments include superior resolution in 1H dimensionmore » without resorting to 1H– 1H homonuclear RF decoupling, easy optimization, and applicability to mass-limited samples. As a result, the HMQC spectra of surface-bound species can be also acquired under 100 kHz MAS, although the dephasing of transverse magnetization has significant effect on the efficiency transfer under MAS alone.« less

Determination of molecular configuration by debye length modulation.

PubMed

Vacic, Aleksandar; Criscione, Jason M; Rajan, Nitin K; Stern, Eric; Fahmy, Tarek M; Reed, Mark A

2011-09-07

Silicon nanowire field effect transistors (FETs) have emerged as ultrasensitive, label-free biodetectors that operate by sensing bound surface charge. However, the ionic strength of the environment (i.e., the Debye length of the solution) dictates the effective magnitude of the surface charge. Here, we show that control of the Debye length determines the spatial extent of sensed bound surface charge on the sensor. We apply this technique to different methods of antibody immobilization, demonstrating different effective distances of induced charge from the sensor surface.

Electron-Transfer Kinetics of Redox Centers Anchored to Metal Surfaces: Weak- versus Strong-Overlap Reaction Pathways.

DTIC Science & Technology

1983-11-01

constants ket are presented for the one-electron electroreduction of various Co1]:I(NH3)5X complexes bound to mercury, platinum, and gold surfaces...electroreduction of various Co^^(NH𔃽)𔃿X complexes bound to mercury, platinum, and gold surfaces via either small inorganic or extended organic ligands X. t...platinum, gold , and copper, to enable values of ke* to be obtained for the one-electron reduction of the surface-Douna_redox center.2.3 These

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

McNeill, Jason Douglas

Electronic states of a thin layer of material on a surface possess unique physical and chemical properties. Some of these properties arise from the reduced dimensionality of the thin layer with respect to the bulk or the properties of the electric field where two materials of differing dielectric constants meet at an interface. Other properties are related to the nature of the surface chemical bond. Here, the properties of excess electrons in thin layers of Xenon, Krypton, and alkali metals are investigated, and the bound state energies and effective masses of the excess electrons are determined using two-photon photoemission. Formore » Xenon, the dependence of bound state energy, effective mass, and lifetime on layer thickness from one to nine layers is examined. Not all quantities were measured at each coverage. The two photon photoemission spectra of thin layers of Xenon on a Ag(111) substrate exhibit a number of sharp, well-defined peaks. The binding energy of the excess electronic states of Xenon layers exhibited a pronounced dependence on coverage. A discrete energy shift was observed for each additional atomic layer. At low coverage, a series of states resembling a Rydberg series is observed. This series is similar to the image state series observed on clean metal surfaces. Deviations from image state energies can be described in terms of the dielectric constant of the overlayer material and its effect on the image potential. For thicker layers of Xe (beyond the first few atomic layers), the coverage dependence of the features begins to resemble that of quantum well states. Quantum well states are related to bulk band states. However, the finite thickness of the layer restricts the perpendicular wavevector to a discrete set of values. Therefore, the spectrum of quantum well states contains a series of peaks which correspond to the various allowed values of the perpendicular wavevector. Analysis of the quantum well spectrum yields electronic band structure information. In this case, the quantum well states examined are derived from the Xenon conduction band. Measurements of the energies as a function of coverage yield the dispersion along the axis perpendicular to the surface while angle-resolved two-photon photoemission measurements yield information about dispersion along the surface parallel. The relative importance of the image potential and the overlayer band structure also depends on the quantum number and energy of the state. Some members of the image series may have an energy which is in an energy gap of the layer material, therefore such states may tend to remain physically outside the layer and retain much of their image character even at higher coverages. This is the case for the n = 1 image state of the Xe/Ag(111) system. The energies of image states which are excluded from the layer have a complex dependence on the thickness of the layer and its dielectric constant. The population decay kinetics of excited electronic states of the layer were also determined. Lifetimes are reported for the first three excited states for 1-6 atomic layers of Xe on Ag(111). As the image states evolve into quantum well states with increasing coverage, the lifetimes undergo an oscillation which marks a change in the spatial extent of the state. For example, the n = 2 quantum well state decreases substantially at 3-5 layers as the electron probability density in the layer increases. The lifetime data are modeled by extending the two-band nearly-free-electron approximation to account for the insulating Xe layer.« less

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

Oyola-Reynoso, S.; Tevis, I. D.; Chen, J.

Here, chemical grafting has been widely used to modify the surface properties of materials, especially surface energy for controlled wetting, because of the resilience of such coatings/modifications. Reagents with multiple reactive sites have been used with the expectation that a monolayer will form. The step-growth polymerization mechanism, however, suggests the possibility of gel formation for hydrolyzable moieties in the presence of physisorbed water. In this report, we demonstrated that using alkyltrichlorosilanes (trivalent [i.e., 3 reactive sites]) in the surface modification of a cellulosic material (paper) does not yield a monolayer but rather gives surface-bound particles. We infer that the presencemore » of physisorbed (surface-bound) water allows for polymerization (or oligomerization) of the silane prior to its attachment on the surface. Surface energy mismatch between the hydrophobic tails of the growing polymer and any unreacted bound water leads to the assembly of the polymerizing material into spherical particles to minimize surface tension. By varying paper grammage (16.2–201.4 g m –2), we varied the accessible surface area and thus the amount of surface-adsorbed water, allowing us to control the ratio of the silane to the bound water. Using this approach, polymeric particles were formed on the surface of cellulose fibers ranging from ~70 nm to a film. The hydrophobicity of the surface, as determined by water contact angles, correlates with particle sizes (p < 0.001, Student's t-test), and, hence, the hydrophobicity can be tuned (contact angle between 94° and 149°). Using a model structure of a house, we demonstrated that as a result of this modification, paper-based houses can be rendered self-cleaning or tolerant to surface running water. In another application, we demonstrated that the felicitous choice of architectural design allows for the hydrophobic paper to be used for water harvesting.« less

Engineering tunable bio-inspired polymeric coatings for amphiphobic fibrous materials

NASA Astrophysics Data System (ADS)

Oyola-Reynoso, Stephanie

Chemical grafting has been widely used to modify the surface properties of materials, especially surface energy for controlled wetting, because of the resilience of such coatings/modifications. Reagents with multiple reactive sites have been used with the expectation that a monolayer will form. The step-growth polymerization mechanism, however, suggests the possibility of gel formation for hydrolysable moieties in the presence of physisorbed water. In the following chapters, we demonstrate that using alkyltrichlorosilanes (trivalent [3 reactive sites]) in the surface modification of a cellulosic material (paper) does not yield a monolayer but rather gives surface-bound polymeric particles. We infer that the presence of physisorbed (surface-bound) water allows for polymerization (or oligomerization) of the silane, prior to its attachment on the surface. Surface energy mismatch between the hydrophobic tails of the growing polymer and any unreacted bound water leads to the assembly of the polymerizing material into spherical particles to minimize surface tension. By varying paper grammage (16.2-201.4 g/m2), we varied the accessible surface area and thus the amount of surface-adsorbed water, allowing us to control the ratio of the silane to the bound water. Using this approach, polymeric particles were formed on the surface of cellulose fibers ranging from 70 nm to a film. The hydrophobicity of the surface, as determined by water contact angles, correlates with particle sizes (p < 0.001, Student t-test), and, hence, the hydrophobicity can be tuned (contact angle between 94° and 149°). Using a model structure of a house, we demonstrated that as a result of this modification, cardboard houses can be rendered self-cleaning or tolerant to surface running water. Each of the chapters below supports the mechanism via a series of applications, material characterization, and/or, smart engineering.

Secure key from bound entanglement.

PubMed

Horodecki, Karol; Horodecki, Michał; Horodecki, Paweł; Oppenheim, Jonathan

2005-04-29

We characterize the set of shared quantum states which contain a cryptographically private key. This allows us to recast the theory of privacy as a paradigm closely related to that used in entanglement manipulation. It is shown that one can distill an arbitrarily secure key from bound entangled states. There are also states that have less distillable private keys than the entanglement cost of the state. In general, the amount of distillable key is bounded from above by the relative entropy of entanglement. Relationships between distillability and distinguishability are found for a class of states which have Bell states correlated to separable hiding states. We also describe a technique for finding states exhibiting irreversibility in entanglement distillation.

Ab initio investigation on the valence and dipole-bound states of CNa - and SiNa -

NASA Astrophysics Data System (ADS)

Kalcher, Josef; Sax, Alexander F.

2000-08-01

CNa - and SiNa - have been studied by the CAS-ACPF method. The 3Σ- ground states have binding energies of 5420 and 7517 cm -1, respectively. The 5Σ- excited states are 494 and 1551 cm -1 above the respective ground states. The 1Δ , 3Π , and 1Π valence-excited states for SiNa - should be at least metastable. CNa - and SiNa - possess dipole-bound 5Σ- and 3Σ- states. Binding energies of these states in CNa - are 217 and 236 cm -1, respectively. SiNa - has two stable 5Σ- dipole-bound states, whose binding energies are 246 and 118 cm -1, respectively.

Metabolism, survival, and gene expression of Pseudomonas putida to hematite nanoparticles mediated by surface-bound humic acid

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

Ouyang, Kai; Walker, Sharon L.; Yu, Xiao-Ying

Natural organic matter (NOM) is likely to coat naturally occurring nanoparticles (NNPs) in the soil environment and poses distinct effects on the interaction between NPs and soil microorganisms, however such topic has not been well investigated. This study explored the influence of nanoparticle surface-bound humic acid (HA, as a model NOM) on the toxicity of hematite NPs (i.e., nano-Fe2O3) to Pseudomonas putida (P. putida). Results showed that nano-Fe2O3 could inhibit the bacterial growth with an IC50 of 23.58 mg L-1, while nanoparticle surface-bound HA could significantly alleviate the P. putida toxicity of nano-Fe2O3. IC50 of nano-Fe2O3 increased to 4774.23 mgmore » L-1 as a result of surface-saturation by HA. Co-precipitation experiment and transmission electron microscopy observation revealed that nanoparticle surface-bound HA prevented the adhesion of nano-Fe2O3 to the cells as well as limited cell internalization of nanoparticles due to the increased electrostatic repulsion. The generation of intracellular reactive oxygen species (ROS) was significantly limited by the nanoparticle surface-bound HA. The prevention of adhesion and inhibition of ROS generation could account for the HA-mitigated nanotoxicity. Interfacial interactions between hematite NPs and cell membrane were also evaluated on the basis of the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, and the magnitude of interaction energy barrier correlated well with the 48 h LC50 data of hematite NPs to P. putida. This result implies that metal oxide NPs with strong association with the cell surface might induce more severe cytotoxicity in microorganisms.« less

Methods for finding transition states on reduced potential energy surfaces

NASA Astrophysics Data System (ADS)

Burger, Steven K.; Ayers, Paul W.

2010-06-01

Three new algorithms are presented for determining transition state (TS) structures on the reduced potential energy surface, that is, for problems in which a few important degrees of freedom can be isolated. All three methods use constrained optimization to rapidly find the TS without an initial Hessian evaluation. The algorithms highlight how efficiently the TS can be located on a reduced surface, where the rest of the degrees of freedom are minimized. The first method uses a nonpositive definite quasi-Newton update for the reduced degrees of freedom. The second uses Shepard interpolation to fit the Hessian and starts from a set of points that bound the TS. The third directly uses a finite difference scheme to calculate the reduced degrees of freedom of the Hessian of the entire system, and searches for the TS on the full potential energy surface. All three methods are tested on an epoxide hydrolase cluster, and the ring formations of cyclohexane and cyclobutenone. The results indicate that all the methods are able to converge quite rapidly to the correct TS, but that the finite difference approach is the most efficient.

Methods for finding transition states on reduced potential energy surfaces.

PubMed

Burger, Steven K; Ayers, Paul W

2010-06-21

Three new algorithms are presented for determining transition state (TS) structures on the reduced potential energy surface, that is, for problems in which a few important degrees of freedom can be isolated. All three methods use constrained optimization to rapidly find the TS without an initial Hessian evaluation. The algorithms highlight how efficiently the TS can be located on a reduced surface, where the rest of the degrees of freedom are minimized. The first method uses a nonpositive definite quasi-Newton update for the reduced degrees of freedom. The second uses Shepard interpolation to fit the Hessian and starts from a set of points that bound the TS. The third directly uses a finite difference scheme to calculate the reduced degrees of freedom of the Hessian of the entire system, and searches for the TS on the full potential energy surface. All three methods are tested on an epoxide hydrolase cluster, and the ring formations of cyclohexane and cyclobutenone. The results indicate that all the methods are able to converge quite rapidly to the correct TS, but that the finite difference approach is the most efficient.

Spectral asymmetry of atoms in the van der Waals potential of an optical nanofiber

NASA Astrophysics Data System (ADS)

Patterson, B. D.; Solano, P.; Julienne, P. S.; Orozco, L. A.; Rolston, S. L.

2018-03-01

We measure the modification of the transmission spectra of cold 87Rb atoms in the proximity of an optical nanofiber (ONF). Van der Waals interactions between the atoms an the ONF surface decrease the resonance frequency of atoms closer to the surface. An asymmetric spectra of the atoms holds information of their spatial distribution around the ONF. We use a far-detuned laser beam coupled to the ONF to thermally excite atoms at the ONF surface. We study the change of transmission spectrum of these atoms as a function of heating laser power. A semiclassical phenomenological model for the thermal excitation of atoms in the atom-surface van der Waals bound states is in good agreement with the measurements. This result suggests that van der Waals potentials could be used to trap and probe atoms at few nanometers from a dielectric surface, a key tool for hybrid photonic-atomic quantum systems.

Cell-derived microparticles and complement activation in preeclampsia versus normal pregnancy.

PubMed

Biró, E; Lok, C A R; Hack, C E; van der Post, J A M; Schaap, M C L; Sturk, A; Nieuwland, R

2007-01-01

Inflammation plays a major role in the vascular dysfunction seen in preeclampsia, and several studies suggest involvement of the complement system. To investigate whether complement activation on the surface of microparticles is increased in plasma of preeclamptic patients versus healthy pregnant controls. Microparticles from plasma of preeclamptic (n=10), healthy pregnant (n=10) and healthy nonpregnant (n=10) women were analyzed by flow cytometry for bound complement components (C1q, C4, C3) and complement activator molecules (C-reactive protein [CRP], serum amyloid P component [SAP], immunoglobulin [Ig]M, IgG). Fluid phase complement activation products and activator molecules were also determined. Levels of microparticles with bound complement components showed no increase in complement activation on the microparticle surface in preeclamptic women, in line with levels of fluid phase complement activation products. In healthy nonpregnant and pregnant women, bound CRP was associated with classical pathway activation on the microparticle surface, and in healthy pregnant women IgM and IgG molecules also contributed. In preeclamptic women, microparticles with bound SAP and those with IgG seemed to contribute to C1q binding without a clear association to further classical pathway activation. Furthermore, significantly increased levels of microparticles with bound CRP were present in preeclamptic compared with healthy pregnant women (median 178x10(6)/L versus 47x10(6)/L, P<0.01), but without concomitant increases in complement activation. We found no evidence of increased complement activation on the microparticle surface in preeclamptic women. Microparticles with bound CRP were significantly increased, but in contrast to healthy pregnant and nonpregnant women, this was not associated with increased classical pathway activation on the surface of the microparticles.

A biochemo-mechano coupled, computational model combining membrane transport and pericellular proteolysis in tissue mechanics

PubMed Central

Vuong, A.-T.; Rauch, A. D.

2017-01-01

We present a computational model for the interaction of surface- and volume-bound scalar transport and reaction processes with a deformable porous medium. The application in mind is pericellular proteolysis, i.e. the dissolution of the solid phase of the extracellular matrix (ECM) as a response to the activation of certain chemical species at the cell membrane and in the vicinity of the cell. A poroelastic medium model represents the extra cellular scaffold and the interstitial fluid flow, while a surface-bound transport model accounts for the diffusion and reaction of membrane-bound chemical species. By further modelling the volume-bound transport, we consider the advection, diffusion and reaction of sequestered chemical species within the extracellular scaffold. The chemo-mechanical coupling is established by introducing a continuum formulation for the interplay of reaction rates and the mechanical state of the ECM. It is based on known experimental insights and theoretical work on the thermodynamics of porous media and degradation kinetics of collagen fibres on the one hand and a damage-like effect of the fibre dissolution on the mechanical integrity of the ECM on the other hand. The resulting system of partial differential equations is solved via the finite-element method. To the best of our knowledge, it is the first computational model including contemporaneously the coupling between (i) advection–diffusion–reaction processes, (ii) interstitial flow and deformation of a porous medium, and (iii) the chemo-mechanical interaction impelled by the dissolution of the ECM. Our numerical examples show good agreement with experimental data. Furthermore, we outline the capability of the methodology to extend existing numerical approaches towards a more comprehensive model for cellular biochemo-mechanics. PMID:28413347

Numerical Solutions of One Reduced Bethe-Salpeter Equation for the Coulombic Bound States Composed of Virtual Constituents

NASA Astrophysics Data System (ADS)

Chen, Jiao-Kai

2018-04-01

We present one reduction of the Bethe-Salpeter equation for the bound states composed of two off-mass-shell constituents. Both the relativistic effects and the virtuality effects can be considered in the obtained spinless virtuality distribution equation. The eigenvalues of the spinless virtuality distribution equation are perturbatively calculated and the bound states e+e-, μ+μ-, τ+τ-, μ+e-, and τ+e- are discussed.

Goldstonic pseudoscalar mesons in Bethe-Salpeter-inspired setting

NASA Astrophysics Data System (ADS)

Lucha, Wolfgang; Schöberl, Franz F.

2018-03-01

For a two-particle bound-state equation closer to its Bethe-Salpeter origins than Salpeter’s equation, with effective interaction kernel deliberately forged such as to ensure, in the limit of zero mass of the bound-state constituents, the vanishing of the arising bound-state mass, we scrutinize the emerging features of the lightest pseudoscalar mesons for their agreement with the behavior predicted by a generalization of the Gell-Mann-Oakes-Renner relation.

Continuous hierarchical slope-aspect color display for parametric surfaces

NASA Technical Reports Server (NTRS)

Moellering, Harold J. (Inventor); Kimerling, A. Jon (Inventor)

1994-01-01

A method for generating an image of a parametric surface, such as the aspect of terrain which maximizes color contrast to permit easy discrimination of the magnitude, ranges, intervals or classes of a surface parameter while making it easy for the user to visualize the form of the surface, such as a landscape. The four pole colors of the opponent process color theory are utilized to represent intervals or classes at 90 degree angles. The color perceived as having maximum measured luminance is selected to portray the color having an azimuth of an assumed light source and the color showing minimum measured luminance portrays the diametrically opposite azimuth. The 90 degree intermediate azimuths are portrayed by unique colors of intermediate measured luminance, such as red and green. Colors between these four pole colors are used which are perceived as mixtures or combinations of their bounding colors and are arranged progressively between their bounding colors to have perceived proportional mixtures of the bounding colors which are proportional to the interval's angular distance from its bounding colors.

Parameter estimation of qubit states with unknown phase parameter

NASA Astrophysics Data System (ADS)

Suzuki, Jun

2015-02-01

We discuss a problem of parameter estimation for quantum two-level system, qubit system, in presence of unknown phase parameter. We analyze trade-off relations for mean square errors (MSEs) when estimating relevant parameters with separable measurements based on known precision bounds; the symmetric logarithmic derivative (SLD) Cramér-Rao (CR) bound and Hayashi-Gill-Massar (HGM) bound. We investigate the optimal measurement which attains the HGM bound and discuss its properties. We show that the HGM bound for relevant parameters can be attained asymptotically by using some fraction of given n quantum states to estimate the phase parameter. We also discuss the Holevo bound which can be attained asymptotically by a collective measurement.

Minimum-error quantum distinguishability bounds from matrix monotone functions: A comment on 'Two-sided estimates of minimum-error distinguishability of mixed quantum states via generalized Holevo-Curlander bounds' [J. Math. Phys. 50, 032106 (2009)

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

Tyson, Jon

2009-06-15

Matrix monotonicity is used to obtain upper bounds on minimum-error distinguishability of arbitrary ensembles of mixed quantum states. This generalizes one direction of a two-sided bound recently obtained by the author [J. Tyson, J. Math. Phys. 50, 032106 (2009)]. It is shown that the previously obtained special case has unique properties.

Joint experimental-theoretical investigation of the lower bound states of the NO(X2Pi)-Kr complex.

PubMed

Wen, Bo; Meyer, Henning; Kłos, Jacek; Alexander, Millard H

2009-07-02

We describe the first measurement of the near IR spectrum of the NO-Kr van der Waals complex. A variant of IR-REMPI double-resonance spectroscopy is employed in which the IR and UV lasers are scanned simultaneously in such a way that throughout the scan the sum of the two photon energies is kept constant, matching a UV resonance of the system. In the region of the first overtone vibration of the NO monomer, we observe several rotationally resolved bands for the NO-Kr complex. In addition to the origin band located at 3723.046 cm(-1), we observe excited as well as hot bands involving the excitation of one or two quanta of z-axis rotation. Another band is assigned to the excitation of one quantum of bending vibration. The experimental spectra are compared with results of bound-state calculations for a new set of potential energy surfaces calculated at the spin-restricted coupled cluster level. For the average vibration-rotation energies, there is excellent agreement between the theoretical results based on the coupled states (CS) approximation and the full close-coupling (CC) treatment. Finer details like the electrostatic splitting and the P-type doubling of the rotational levels are accounted for only within the CC formalism. The comparison of the CC results with the measured spectra confirms the high quality of the PESs. However, the high resolution of the experiments is sufficient to identify some inaccuracies in the difference between the potential energy surfaces of A' and A'' reflection symmetry.

Platinum nanocatalysts prepared with different surfactants for C1-C3 alcohol oxidations and their surface morphologies by AFM

NASA Astrophysics Data System (ADS)

Ertan, Salih; Şen, Fatih; Şen, Selda; Gökağaç, Gülsün

2012-06-01

In this study, platinum nanoparticle catalysts have been prepared using PtCl4 as a starting material and 1-octanethiol, 1-decanethiol, 1-dodecanethiol, and 1-hexadecanethiol as surfactants for methanol, ethanol, and 2-propanol oxidation reactions. The structure, particle sizes, and surface morphologies of the catalysts were characterized by X-ray diffraction (XRD), atomic force microscopy and transmission electron microscopy (TEM). XRD and TEM results indicate that all prepared catalysts have a face-centered cubic structure and are homogeneously dispersed on the carbon support with a narrow size distribution (2.0-1.3 nm). X-ray photoelectron spectra of the catalysts were examined and it is found that platinum has two different oxidation states, Pt (0) and Pt(IV), oxygen and sulfur compounds are H2Oads and OHads, bound and unbound thiols. The electrochemical and electrocatalytic properties of these catalysts were investigated with respect to C1-C3 alcohol oxidations by cyclic voltammetry and chronoamperometry. The highest electrocatalytic activity was obtained from catalyst I which was prepared with 1-octanethiol. This may be attributed to a decrease in the ratio of bound to unbound thiol species increase in Pt (0)/Pt(IV), H2Oads/OHads ratios, electrochemical surface area, CO tolerance and percent platinum utility.

Unliganded HIV-1 gp120 core structures assume the CD4-bound conformation with regulation by quaternary interactions and variable loops

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

Kwon, Young Do; Finzi, Andrés; Wu, Xueling

2013-03-04

The HIV-1 envelope (Env) spike (gp120{sub 3}/gp41{sub 3}) undergoes considerable structural rearrangements to mediate virus entry into cells and to evade the host immune response. Engagement of CD4, the primary human receptor, fixes a particular conformation and primes Env for entry. The CD4-bound state, however, is prone to spontaneous inactivation and susceptible to antibody neutralization. How does unliganded HIV-1 maintain CD4-binding capacity and regulate transitions to the CD4-bound state? To define this mechanistically, we determined crystal structures of unliganded core gp120 from HIV-1 clades B, C, and E. Notably, all of these unliganded HIV-1 structures resembled the CD4-bound state. Conformationalmore » fixation with ligand selection and thermodynamic analysis of full-length and core gp120 interactions revealed that the tendency of HIV-1 gp120 to adopt the CD4-bound conformation was restrained by the V1/V2- and V3-variable loops. In parallel, we determined the structure of core gp120 in complex with the small molecule, NBD-556, which specifically recognizes the CD4-bound conformation of gp120. Neutralization by NBD-556 indicated that Env spikes on primary isolates rarely assume the CD4-bound conformation spontaneously, although they could do so when quaternary restraints were loosened. Together, the results suggest that the CD4-bound conformation represents a 'ground state' for the gp120 core, with variable loop and quaternary interactions restraining unliganded gp120 from 'snapping' into this conformation. A mechanism of control involving deformations in unliganded structure from a functionally critical state (e.g., the CD4-bound state) provides advantages in terms of HIV-1 Env structural diversity and resistance to antibodies and inhibitors, while maintaining elements essential for entry.« less

Iron-bound organic carbon in forest soils: quantification and characterization

DOE PAGES

Zhao, Qian; Poulson, Simon R.; Obrist, Daniel; ...

2016-08-24

Iron oxide minerals play an important role in stabilizing organic carbon (OC) and regulating the biogeochemical cycles of OC on the earth surface. To predict the fate of OC, it is essential to understand the amount, spatial variability, and characteristics of Fe-bound OC in natural soils. In this study, we investigated the concentrations and characteristics of Fe-bound OC in soils collected from 14 forests in the United States and determined the impact of ecogeographical variables and soil physicochemical properties on the association of OC and Fe minerals. On average, Fe-bound OC contributed 37.8 % of total OC (TOC) in forestmore » soils. Atomic ratios of OC : Fe ranged from 0.56 to 17.7, with values of 1–10 for most samples, and the ratios indicate the importance of both sorptive and incorporative interactions. The fraction of Fe-bound OC in TOC (fFe-OC) was not related to the concentration of reactive Fe, which suggests that the importance of association with Fe in OC accumulation was not governed by the concentration of reactive Fe. Concentrations of Fe-bound OC and fFe-OC increased with latitude and reached peak values at a site with a mean annual temperature of 6.6 °C. Attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) and near-edge X-ray absorption fine structure (NEXAFS) analyses revealed that Fe-bound OC was less aliphatic than non-Fe-bound OC. Fe-bound OC also was more enriched in 13C compared to the non-Fe-bound OC, but C/N ratios did not differ substantially. In summary, 13C-enriched OC with less aliphatic carbon and more carboxylic carbon was associated with Fe minerals in the soils, with values of fFe-OC being controlled by both sorptive and incorporative associations between Fe and OC. Overall, this study demonstrates that Fe oxides play an important role in regulating the biogeochemical cycles of C in forest soils and uncovers the governing factors for the spatial variability and characteristics of Fe-bound OC.« less

Impact of iron-site defects on superconductivity in LiFeAs

DOE PAGES

Chi, Shun; Aluru, Ramakrishna; Singh, Udai Raj; ...

2016-10-19

In conventional s -wave superconductors, only magnetic impurities exhibit impurity bound states, whereas for an s ± order parameter they can occur for both magnetic and nonmagnetic impurities. Impurity bound states in superconductors can thus provide important insight into the order parameter. We present a combined experimental and theoretical study of native and engineered iron-site defects in LiFeAs. A detailed comparison of tunneling spectra measured on impurities with spin-fluctuation theory reveals a continuous evolution from negligible impurity-bound-state features for weaker scattering potential to clearly detectable states for somewhat stronger scattering potentials. Furthermore, all bound states for these intermediate strengthmore » potentials are pinned at or close to the gap edge of the smaller gap, a phenomenon that we explain and ascribe to multiorbital physics.« less

Maternal allergy is associated with surface-bound IgE on cord blood basophils.

PubMed

Matson, Adam P; Cloutier, Michelle M; Dhongade, Ashish; Puddington, Lynn; Rafti, Ektor

2013-09-01

The cell type(s) mediating the maternal influence on allergic disease in children remain unclear. We set out to define the relationship between maternal allergy and frequencies of cord blood (CB) basophils, and plasmacytoid dendritic cells (pDCs); to characterize surface-bound IgE and FcεRI expressions on these cells; and to investigate the association between maternal and CB serum IgE levels with surface-bound IgE and FcεRI expressions. One hundred and three mother/infant dyads were recruited prenatally, and maternal allergic history was recorded. Maternal blood was collected prior to delivery, and CB was collected after birth. Flow cytometry was used to identify CB basophils and pDCs and to determine surface-bound IgE and FcεRI expressions. Frequencies of CB basophils and pDCs were low and not related to maternal history of allergy. Percentages of CB basophils with surface-bound IgE were significantly higher in infants of allergic mothers compared with infants of non-allergic mothers (median, 59.60% vs. 19.70%, p = 0.01). IgE on CB basophils correlated with CB IgE levels (r = 0.72, p < 0.0001), but not with maternal IgE levels (r = 0.26, p = 0.06). IgE on CB pDCs was low and not significantly associated with maternal or CB IgE levels. Similarly, FcεRI expression by CB basophils and pDCs was not significantly associated with maternal or CB IgE levels. Frequencies of CB basophils and pDCs are not influenced by maternal allergy. CB basophils and pDCs have surface-bound IgE and express FcεRI; however, only IgE on CB basophils appears influenced by maternal allergy. © 2013 The Authors. Pediatric Allergy and Immunology published by John Wiley & Sons Ltd.

Tunneling spectroscopy of quasiparticle bound states in a spinful Josephson junction.

PubMed

Chang, W; Manucharyan, V E; Jespersen, T S; Nygård, J; Marcus, C M

2013-05-24

The spectrum of a segment of InAs nanowire, confined between two superconducting leads, was measured as function of gate voltage and superconducting phase difference using a third normal-metal tunnel probe. Subgap resonances for odd electron occupancy-interpreted as bound states involving a confined electron and a quasiparticle from the superconducting leads, reminiscent of Yu-Shiba-Rusinov states-evolve into Kondo-related resonances at higher magnetic fields. An additional zero-bias peak of unknown origin is observed to coexist with the quasiparticle bound states.

A roaming wavepacket in the dynamics of electronically excited 2-hydroxypyridine.

PubMed

Poisson, Lionel; Nandi, Dhananjay; Soep, Benoît; Hochlaf, Majdi; Boggio-Pasqua, Martial; Mestdagh, Jean-Michel

2014-01-14

How much time does it take for a wavepacket to roam on a multidimensional potential energy surface? This combined theoretical and pump-probe femtosecond time experiment on 2-hydroxypyridine proposes an answer. Bypassing the well-established transition state and conical intersection relaxation pathways, this molecular system undergoes relaxation into the S1 excited state: the central ring is destabilized by the electronic excitation, within ~100 fs after absorption of the pump photon, then the H-atom bound to oxygen undergoes a roaming behavior when it couples to other degrees of freedom of the molecule. The timescale of the latter process is measured to be ~1.3 ps. Further evolution of the wavepacket is either an oscillation onto the S1 potential or a conversion into the triplet state for timescale larger than ~110 ps. Our work introduces a new tool for the understanding of time-resolved relaxation dynamics applied to large molecules through the roaming dynamics characterized by its strongly delocalized wavepacket on flat molecular potential energy surfaces.

Numerical Analysis of Infiltration Into a Sand Profile Bounded by a Capillary Fringe

NASA Astrophysics Data System (ADS)

Curtis, Alan A.; Watson, Keith K.

1980-04-01

The rapid response sometimes observed in a tile drain system following surface ponding of water is discussed in terms of the air compressibility effect. An earlier numerical study describing water movement into a bounded profile with a lower boundary impermeable to the passage of both air and water is reviewed with particular reference to the validity of the time-dependent boundary condition transformation used in simulating the inhibiting effects of the air pressure increase on infiltration. The extension of the transformation approach to a profile bounded by a capillary fringe is then considered in detail, and the results of numerical analyses are presented for infiltration into two columns of a fine sand initially in hydraulic equilibrium from a prior gravity drainage regime. The shorter column develops a steady state flow condition at short times which is consistent with earlier experimental findings. In contrast, the pressure of the entrapped air in the longer column gradually increases as infiltration proceeds until the analysis is terminated when air escape through the lower boundary is imminent.

MD simulations of ligand-bound and ligand-free aptamer: molecular level insights into the binding and switching mechanism of the add A-riboswitch.

PubMed

Sharma, Monika; Bulusu, Gopalakrishnan; Mitra, Abhijit

2009-09-01

Riboswitches are structural cis-acting genetic regulatory elements in 5' UTRs of mRNAs, consisting of an aptamer domain that regulates the behavior of an expression platform in response to its recognition of, and binding to, specific ligands. While our understanding of the ligand-bound structure of the aptamer domain of the adenine riboswitches is based on crystal structure data and is well characterized, understanding of the structure and dynamics of the ligand-free aptamer is limited to indirect inferences from physicochemical probing experiments. Here we report the results of 15-nsec-long explicit-solvent molecular dynamics simulations of the add A-riboswitch crystal structure (1Y26), both in the adenine-bound (CLOSED) state and in the adenine-free (OPEN) state. Root-mean-square deviation, root-mean-square fluctuation, dynamic cross-correlation, and backbone torsion angle analyses are carried out on the two trajectories. These, along with solvent accessible surface area analysis of the two average structures, are benchmarked against available experimental data and are shown to constitute the basis for obtaining reliable insights into the molecular level details of the binding and switching mechanism. Our analysis reveals the interaction network responsible for, and conformational changes associated with, the communication between the binding pocket and the expression platform. It further highlights the significance of a, hitherto unreported, noncanonical W:H trans base pairing between A73 and A24, in the OPEN state, and also helps us to propose a possibly crucial role of U51 in the context of ligand binding and ligand discrimination.

Near infrared overtone (vOH = 2 ← 0) spectroscopy of Ne-H2O clusters

NASA Astrophysics Data System (ADS)

Ziemkiewicz, Michael P.; Pluetzer, Christian; Wojcik, Michael; Loreau, Jérôme; van der Avoird, Ad; Nesbitt, David J.

2017-03-01

Vibrationally state selective overtone spectroscopy and dynamics of weakly bound Ne-H2O complexes (D0(para) = 31.67 cm-1, D0(ortho) = 34.66 cm-1) are reported for the first time, based on near infrared excitation of van der Waals cluster bands correlating with vOH = 2 ← 0 overtone transitions (|02-⟩←|00+⟩ and |02+⟩ ←|00+⟩ ) out of the ortho (101) and para (000) internal rotor states of the H2O moiety. Quantum theoretical calculations for nuclear motion on a high level ab initio potential energy surface (CCSD(T)/VnZ-f12 (n = 3,4), corrected for basis set superposition error and extrapolated to the complete basis set limit) are employed for assignment of Σ ←Σ ,Π ←Σ , and Σ ←Π infrared bands in the overtone spectra, where Σ ( K = 0) and Π (K = 1) represent approximate projections (K) of the body angular momentum along the Ne-H2O internuclear axis. End-over-end tumbling of the ortho Ne-H2O cluster is evident via rotational band contours observed, with band origins and rotational progressions in excellent agreement with ab initio frequency and intensity predictions. A clear Q branch in the corresponding |02+⟩fΠ (111) ←eΣ (000) para Ne-H2O spectrum provides evidence for a novel e/f parity-dependent metastability in these weakly bound clusters, in agreement with ab initio bound state calculations and attributable to the symmetry blocking of an energetically allowed channel for internal rotor predissociation. Finally, Boltzmann analysis of the rotational spectra reveals anomalously low jet temperatures (Trot ≈ 4(1) K), which are attributed to "evaporative cooling" of weakly bound Ne-H2O clusters and provide support for similar cooling dynamics in rare gas-tagging studies.

Relativistic polytropic spheres with electric charge: Compact stars, compactness and mass bounds, and quasiblack hole configurations

NASA Astrophysics Data System (ADS)

Arbañil, José D. V.; Zanchin, Vilson T.

2018-05-01

We study the static equilibrium configurations of uncharged and charged spheres composed by a relativistic polytropic fluid, and we compare with those of spheres composed by a nonrelativistic polytropic fluid, the later case being already studied in a previous work [J. D. Arbañil, P. S. Lemos, and V. T. Zanchin, Phys. Rev. D 88, 084023 (2013), 10.1103/PhysRevD.88.084023]. An equation of state connecting the pressure p and the energy density ρ is assumed. In the nonrelativistic fluid case, the connection is through a nonrelativistic polytropic equation of state, p =ω ργ , with ω and γ being respectively the polytropic constant and the polytropic exponent. In the relativistic fluid case, the connection is through a relativistic polytropic equation of state, p =ω δγ, with δ =ρ -p /(γ -1 ), and δ being the rest-mass density of the fluid. For the electric charge distribution, we assume that the charge density ρe is proportional to the energy density ρ , ρe=α ρ , with α being a constant such that 0 ≤|α |≤1 . The study is developed by integrating numerically the hydrostatic equilibrium equation. Some properties of the charged spheres such as the gravitational mass, the total electric charge, the radius, the surface redshift, and the speed of sound are analyzed by varying the central rest-mass density, the charge fraction, and the polytropic exponent. In addition, some limits that arise in general relativity, such as the Chandrasekhar limit, the Oppenheimer-Volkoff limit, the Buchdahl bound, and the Buchdahl-Andréasson bound are studied. It is confirmed that charged relativistic polytropic spheres with γ →∞ and α →1 saturate the Buchdahl-Andréasson bound, thus indicating that it reaches the quasiblack hole configuration. We show by means of numerical analysis that, as expected, the major differences between the two cases appear in the high energy density region.

Tightening Quantum Speed Limits for Almost All States.

PubMed

Campaioli, Francesco; Pollock, Felix A; Binder, Felix C; Modi, Kavan

2018-02-09

Conventional quantum speed limits perform poorly for mixed quantum states: They are generally not tight and often significantly underestimate the fastest possible evolution speed. To remedy this, for unitary driving, we derive two quantum speed limits that outperform the traditional bounds for almost all quantum states. Moreover, our bounds are significantly simpler to compute as well as experimentally more accessible. Our bounds have a clear geometric interpretation; they arise from the evaluation of the angle between generalized Bloch vectors.

Two-polariton bound states in the Jaynes-Cummings-Hubbard model

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

Wong, Max T. C.; Law, C. K.

2011-05-15

We examine the eigenstates of the one-dimensional Jaynes-Cummings-Hubbard model in the two-excitation subspace. We discover that two-excitation bound states emerge when the ratio of vacuum Rabi frequency to the tunneling rate between cavities exceeds a critical value. We determine the critical value as a function of the quasimomentum quantum number, and indicate that the bound states carry a strong correlation in which the two polaritons appear to be spatially confined together.

The light bound states of N=1 supersymmetric SU(3) Yang-Mills theory on the lattice

NASA Astrophysics Data System (ADS)

Ali, Sajid; Bergner, Georg; Gerber, Henning; Giudice, Pietro; Montvay, Istvan; Münster, Gernot; Piemonte, Stefano; Scior, Philipp

2018-03-01

In this article we summarise our results from numerical simulations of N=1 supersymmetric Yang-Mills theory with gauge group SU(3). We use the formulation of Curci and Veneziano with clover-improved Wilson fermions. The masses of various bound states have been obtained at different values of the gluino mass and gauge coupling. Extrapolations to the limit of vanishing gluino mass indicate that the bound states form mass-degenerate supermultiplets.

The construction, fouling and enzymatic cleaning of a textile dye surface.

PubMed

Onaizi, Sagheer A; He, Lizhong; Middelberg, Anton P J

2010-11-01

The enzymatic cleaning of a rubisco protein stain bound onto Surface Plasmon Resonance (SPR) biosensor chips having a dye-bound upper layer is investigated. This novel method allowed, for the first time, a detailed kinetic study of rubisco cleanability (defined as fraction of adsorbed protein removed from a surface) from dyed surfaces (mimicking fabrics) at different enzyme concentrations. Analysis of kinetic data using an established mathematical model able to decouple enzyme transfer and reaction processes [Onaizi, He, Middelberg, Chem. Eng. Sci. 64 (2008) 3868] revealed a striking effect of dyeing on enzymatic cleaning performance. Specifically, the absolute rate constants for enzyme transfer to and from a dye-bound rubisco stain were significantly higher than reported previously for un-dyed surfaces. These increased transfer rates resulted in higher surface cleanability. Higher enzyme mobility (i.e., higher enzyme adsorption and desorption rates) at the liquid-dye interface was observed, consistent with previous suggestions that enzyme surface mobility is likely correlated with overall enzyme cleaning performance. Our results show that reaction engineering models of enzymatic action at surfaces may provide insight able to guide the design of better stain-resistant surfaces, and may also guide efforts to improve cleaning formulations. Copyright 2010 Elsevier Inc. All rights reserved.

Architectural elements and bounding surfaces in fluvial deposits: anatomy of the Kayenta formation (lower jurassic), Southwest Colorado

NASA Astrophysics Data System (ADS)

Miall, Andrew D.

1988-03-01

Three well-exposed outcrops in the Kayenta Formation (Lower Jurassic), near Dove Creek in southwestern Colorado, were studied using lateral profiles, in order to test recent regarding architectural-element analysis and the classification and interpretation of internal bounding surfaces. Examination of bounding surfaces within and between elements in the Kayenta outcrops raises problems in applying the three-fold classification of Allen (1983). Enlarging this classification to a six-fold hierarchy permits the discrimination of surfaces intermediate between Allen's second- and third-order types, corresponding to the upper bounding surfaces of macroforms, and internal erosional "reactivation" surfaces within the macroforms. Examples of the first five types of surface occur in the Kayenta outcrops at Dove Creek. The new classifications is offered as a general solution to the problem of description of complex, three-dimensional fluvial sandstone bodies. The Kayenta Formation at Dove Creek consists of a multistorey sandstone body, including the deposits of lateral- and downstream-accreted macroforms. The storeys show no internal cyclicity, neither within individual elements nor through the overall vertical thickness of the formation. Low paleocurrent variance indicates low sinuosity flow, whereas macroform geometry and orientation suggest low to moderate sinuosity. The many internal minor erosion surfaces draped with mud and followed by intraclast breccias imply frequent rapid stage fluctuation, consistent with variable (seasonal? monsonal? ephemmeral?) flow. The results suggest a fluvial architecture similar to that of the South Saskatchewan River, through with a three-dimensional geometry unlike that interpreted from surface studies of that river.

Dynamic spin injection into a quantum well coupled to a spin-split bound state

NASA Astrophysics Data System (ADS)

Maslova, N. S.; Rozhansky, I. V.; Mantsevich, V. N.; Arseyev, P. I.; Averkiev, N. S.; Lähderanta, E.

2018-05-01

We present a theoretical analysis of dynamic spin injection due to spin-dependent tunneling between a quantum well (QW) and a bound state split in spin projection due to an exchange interaction or external magnetic field. We focus on the impact of Coulomb correlations at the bound state on spin polarization and sheet density kinetics of the charge carriers in the QW. The theoretical approach is based on kinetic equations for the electron occupation numbers taking into account high order correlation functions for the bound state electrons. It is shown that the on-site Coulomb repulsion leads to an enhanced dynamic spin polarization of the electrons in the QW and a delay in the carriers tunneling into the bound state. The interplay of these two effects leads to nontrivial dependence of the spin polarization degree, which can be probed experimentally using time-resolved photoluminescence experiments. It is demonstrated that the influence of the Coulomb interactions can be controlled by adjusting the relaxation rates. These findings open a new way of studying the Hubbard-like electron interactions experimentally.

Maximum and minimum entropy states yielding local continuity bounds

NASA Astrophysics Data System (ADS)

Hanson, Eric P.; Datta, Nilanjana

2018-04-01

Given an arbitrary quantum state (σ), we obtain an explicit construction of a state ρɛ * ( σ ) [respectively, ρ * , ɛ ( σ ) ] which has the maximum (respectively, minimum) entropy among all states which lie in a specified neighborhood (ɛ-ball) of σ. Computing the entropy of these states leads to a local strengthening of the continuity bound of the von Neumann entropy, i.e., the Audenaert-Fannes inequality. Our bound is local in the sense that it depends on the spectrum of σ. The states ρɛ * ( σ ) and ρ * , ɛ (σ) depend only on the geometry of the ɛ-ball and are in fact optimizers for a larger class of entropies. These include the Rényi entropy and the minimum- and maximum-entropies, providing explicit formulas for certain smoothed quantities. This allows us to obtain local continuity bounds for these quantities as well. In obtaining this bound, we first derive a more general result which may be of independent interest, namely, a necessary and sufficient condition under which a state maximizes a concave and Gâteaux-differentiable function in an ɛ-ball around a given state σ. Examples of such a function include the von Neumann entropy and the conditional entropy of bipartite states. Our proofs employ tools from the theory of convex optimization under non-differentiable constraints, in particular Fermat's rule, and majorization theory.

Detachment dynamics of colloidal spheres with adhesive interactions

NASA Astrophysics Data System (ADS)

Bergenholtz, J.

2018-04-01

Escape of colloidal-size particles from various kinds of solids, such as aggregates and surfaces, occurs in a wide variety of settings of both fundamental and applied scientific interest. In this paper an exact solution for the detachment of adhesive spheres from each other by means of diffusion is presented. The solution takes into account repeated detachment and reattachment events in the course of time on the way toward the permanently separated state. For strongly adhesive spheres this state is approached in an exponential manner essentially regardless of how the bound state is specified. The analytical solution is shown to capture semiquantitatively the escape from more realistic potential wells using a mapping procedure whereby equality of second virial coefficients is imposed.

Bounds on the entanglement entropy of droplet states in the XXZ spin chain

NASA Astrophysics Data System (ADS)

Beaud, V.; Warzel, S.

2018-01-01

We consider a class of one-dimensional quantum spin systems on the finite lattice Λ ⊂Z , related to the XXZ spin chain in its Ising phase. It includes in particular the so-called droplet Hamiltonian. The entanglement entropy of energetically low-lying states over a bipartition Λ = B ∪ Bc is investigated and proven to satisfy a logarithmic bound in terms of min{n, |B|, |Bc|}, where n denotes the maximal number of down spins in the considered state. Upon addition of any (positive) random potential, the bound becomes uniformly constant on average, thereby establishing an area law. The proof is based on spectral methods: a deterministic bound on the local (many-body integrated) density of states is derived from an energetically motivated Combes-Thomas estimate.

Inhibition of neutrophil migration by aggregated immunoglobulin attached to micropore membranes.

PubMed Central

Kemp, A S; Brown, S

1980-01-01

The effect of substrate-bound immunoglobulin on neutrophil migration was examined. Immunoglobulin aggregates bound to micropore membranes inhibited the neutrophil response to a chemotactic stimulus. This inhibition was reversed by the presence of aggregates in suspension suggesting competition between substrate-bound and free aggregates for neutrophil surface binding sites. The immobilization of neutrophils by substrate-bound aggregated immunoglobulin suggests a mechanism for the accumulation of neutrophils at sites of immune complex deposition and tissue-bound antibodies in vivo. PMID:7380477

Application of Spaceborne Scatterometer for Mapping Freeze-Thaw State in Northern Landscapes as a Measure of Ecological and Hydrological Processes

NASA Technical Reports Server (NTRS)

McDonald, Kyle; Kimball, John; Zimmermann, Reiner; Way, JoBea; Frolking, Steve; Running, Steve

1994-01-01

Landscape freeze/thaw transitions coincide with marked shifts in albedo, surface energy and mass exchange, and associated snow dynamics. monitoring landscape freeze/thaw dynamics would improve our ability to quantify the interannual variability of boreal hydrology and river runoff/flood dynamics, The annual duration of frost-free period also bounds the period of photosynthetic activity in borel and arctic regions thus affecting the carbon budget and the interannual variability fo regional carbon fluxes.

Seismology: tectonic strain in plate interiors?

PubMed

Calais, E; Mattioli, G; DeMets, C; Nocquet, J-M; Stein, S; Newman, A; Rydelek, P

2005-12-15

It is not fully understood how or why the inner areas of tectonic plates deform, leading to large, although infrequent, earthquakes. Smalley et al. offer a potential breakthrough by suggesting that surface deformation in the central United States accumulates at rates comparable to those across plate boundaries. However, we find no statistically significant deformation in three independent analyses of the data set used by Smalley et al., and conclude therefore that only the upper bounds of magnitude and repeat time for large earthquakes can be inferred at present.

Absorption enhancement in type-II coupled quantum rings due to existence of quasi-bound states

NASA Astrophysics Data System (ADS)

Hsieh, Chi-Ti; Lin, Shih-Yen; Chang, Shu-Wei

2018-02-01

The absorption of type-II nanostructures is often weaker than type-I counterpart due to spatially separated electrons and holes. We model the bound-to-continuum absorption of type-II quantum rings (QRs) using a multiband source-radiation approach using the retarded Green function in the cylindrical coordinate system. The selection rules due to the circular symmetry for allowed transitions of absorption are utilized. The bound-tocontinuum absorptions of type-II GaSb coupled and uncoupled QRs embedded in GaAs matrix are compared here. The GaSb QRs act as energy barriers for electrons but potential wells for holes. For the coupled QR structure, the region sandwiched between two QRs forms a potential reservoir of quasi-bound electrons. Electrons in these states, though look like bound ones, would ultimately tunnel out of the reservoir through barriers. Multiband perfectly-matched layers are introduced to model the tunneling of quasi-bound states into open space. Resonance peaks are observed on the absorption spectra of type-II coupled QRs due to the formation of quasi-bound states in conduction bands, but no resonance exist in the uncoupled QR. The tunneling time of these metastable states can be extracted from the resonance and is in the order of ten femtoseconds. Absorption of coupled QRs is significantly enhanced as compared to that of uncoupled ones in certain spectral windows of interest. These features may improve the performance of photon detectors and photovoltaic devices based on type-II semiconductor nanostructures.

Search for weakly decaying Λn ‾ and ΛΛ exotic bound states in central Pb-Pb collisions at √{sNN} = 2.76 TeV

NASA Astrophysics Data System (ADS)

Adam, J.; Adamová, D.; Aggarwal, M. M.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahmed, I.; Ahn, S. U.; Aimo, I.; Aiola, S.; Ajaz, M.; Akindinov, A.; Alam, S. N.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alfaro Molina, R.; Alici, A.; Alkin, A.; Alme, J.; Alt, T.; Altinpinar, S.; Altsybeev, I.; Alves Garcia Prado, C.; Andrei, C.; Andronic, A.; Anguelov, V.; Anielski, J.; Antičić, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arcelli, S.; Armesto, N.; Arnaldi, R.; Aronsson, T.; Arsene, I. C.; Arslandok, M.; Augustinus, A.; Averbeck, R.; Azmi, M. D.; Bach, M.; Badalà, A.; Baek, Y. W.; Bagnasco, S.; Bailhache, R.; Bala, R.; Baldisseri, A.; Ball, M.; Baltasar Dos Santos Pedrosa, F.; Baral, R. C.; Barbano, A. M.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartalini, P.; Bartke, J.; Bartsch, E.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batista Camejo, A.; Batyunya, B.; Batzing, P. C.; Bearden, I. G.; Beck, H.; Bedda, C.; Behera, N. K.; Belikov, I.; Bellini, F.; Bello Martinez, H.; Bellwied, R.; Belmont, R.; Belmont-Moreno, E.; Belyaev, V.; Bencedi, G.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Bertens, R. A.; Berzano, D.; Betev, L.; Bhasin, A.; Bhat, I. R.; Bhati, A. K.; Bhattacharjee, B.; Bhom, J.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielčík, J.; Bielčíková, J.; Bilandzic, A.; Biswas, S.; Bjelogrlic, S.; Blanco, F.; Blau, D.; Blume, C.; Bock, F.; Bogdanov, A.; Bøggild, H.; Boldizsár, L.; Bombara, M.; Book, J.; Borel, H.; Borissov, A.; Borri, M.; Bossú, F.; Botje, M.; Botta, E.; Böttger, S.; Braun-Munzinger, P.; Bregant, M.; Breitner, T.; Broker, T. A.; Browning, T. A.; Broz, M.; Brucken, E. J.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buncic, P.; Busch, O.; Buthelezi, Z.; Buxton, J. T.; Caffarri, D.; Cai, X.; Caines, H.; Calero Diaz, L.; Caliva, A.; Calvo Villar, E.; Camerini, P.; Carena, F.; Carena, W.; Castillo Castellanos, J.; Castro, A. J.; Casula, E. A. R.; Cavicchioli, C.; Ceballos Sanchez, C.; Cepila, J.; Cerello, P.; Chang, B.; Chapeland, S.; Chartier, M.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Chelnokov, V.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chibante Barroso, V.; Chinellato, D. D.; Chochula, P.; Choi, K.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Colamaria, F.; Colella, D.; Collu, A.; Colocci, M.; Conesa Balbastre, G.; Conesa del Valle, Z.; Connors, M. E.; Contreras, J. G.; Cormier, T. M.; Corrales Morales, Y.; Cortés Maldonado, I.; Cortese, P.; Cosentino, M. R.; Costa, F.; Crochet, P.; Cruz Albino, R.; Cuautle, E.; Cunqueiro, L.; Dahms, T.; Dainese, A.; Danu, A.; Das, D.; Das, I.; Das, S.; Dash, A.; Dash, S.; De, S.; De Caro, A.; de Cataldo, G.; de Cuveland, J.; De Falco, A.; De Gruttola, D.; De Marco, N.; De Pasquale, S.; Deisting, A.; Deloff, A.; Dénes, E.; D'Erasmo, G.; Di Bari, D.; Di Mauro, A.; Di Nezza, P.; Diaz Corchero, M. A.; Dietel, T.; Dillenseger, P.; Divià, R.; Djuvsland, Ø.; Dobrin, A.; Dobrowolski, T.; Domenicis Gimenez, D.; Dönigus, B.; Dordic, O.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Dupieux, P.; Ehlers, R. J.; Elia, D.; Engel, H.; Erazmus, B.; Erhardt, F.; Eschweiler, D.; Espagnon, B.; Estienne, M.; Esumi, S.; Evans, D.; Evdokimov, S.; Eyyubova, G.; Fabbietti, L.; Fabris, D.; Faivre, J.; Fantoni, A.; Fasel, M.; Feldkamp, L.; Felea, D.; Feliciello, A.; Feofilov, G.; Ferencei, J.; Fernández Téllez, A.; Ferreiro, E. G.; Ferretti, A.; Festanti, A.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Fleck, M. G.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Frankenfeld, U.; Fuchs, U.; Furget, C.; Furs, A.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A. M.; Gallio, M.; Gangadharan, D. R.; Ganoti, P.; Gao, C.; Garabatos, C.; Garcia-Solis, E.; Gargiulo, C.; Gasik, P.; Germain, M.; Gheata, A.; Gheata, M.; Ghosh, P.; Ghosh, S. K.; Gianotti, P.; Giubellino, P.; Giubilato, P.; Gladysz-Dziadus, E.; Glässel, P.; Gomez Ramirez, A.; González-Zamora, P.; Gorbunov, S.; Görlich, L.; Gotovac, S.; Grabski, V.; Graczykowski, L. K.; Grelli, A.; Grigoras, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Grosse-Oetringhaus, J. F.; Grossiord, J.-Y.; Grosso, R.; Guber, F.; Guernane, R.; Guerzoni, B.; Gulbrandsen, K.; Gulkanyan, H.; Gunji, T.; Gupta, A.; Gupta, R.; Haake, R.; Haaland, Ø.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.; Hanratty, L. D.; Hansen, A.; Harris, J. W.; Hartmann, H.; Harton, A.; Hatzifotiadou, D.; Hayashi, S.; Heckel, S. T.; Heide, M.; Helstrup, H.; Herghelegiu, A.; Herrera Corral, G.; Hess, B. A.; Hetland, K. F.; Hilden, T. E.; Hillemanns, H.; Hippolyte, B.; Hristov, P.; Huang, M.; Humanic, T. J.; Hussain, N.; Hussain, T.; Hutter, D.; Hwang, D. S.; Ilkaev, R.; Ilkiv, I.; Inaba, M.; Ionita, C.; Ippolitov, M.; Irfan, M.; Ivanov, M.; Ivanov, V.; Izucheev, V.; Jachołkowski, A.; Jacobs, P. M.; Jahnke, C.; Jang, H. J.; Janik, M. A.; Jayarathna, P. H. S. Y.; Jena, C.; Jena, S.; Jimenez Bustamante, R. T.; Jones, P. G.; Jung, H.; Jusko, A.; Kalinak, P.; Kalweit, A.; Kamin, J.; Kang, J. H.; Kaplin, V.; Kar, S.; Karasu Uysal, A.; Karavichev, O.; Karavicheva, T.; Karpechev, E.; Kebschull, U.; Keidel, R.; Keijdener, D. L. D.; Keil, M.; Khan, K. H.; Khan, M. M.; Khan, P.; Khan, S. A.; Khanzadeev, A.; Kharlov, Y.; Kileng, B.; Kim, B.; Kim, D. W.; Kim, D. J.; Kim, H.; Kim, J. S.; Kim, M.; Kim, M.; Kim, S.; Kim, T.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Kiss, G.; Klay, J. L.; Klein, C.; Klein, J.; Klein-Bösing, C.; Kluge, A.; Knichel, M. L.; Knospe, A. G.; Kobayashi, T.; Kobdaj, C.; Kofarago, M.; Köhler, M. K.; Kollegger, T.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Kondratyuk, E.; Konevskikh, A.; Kouzinopoulos, C.; Kovalenko, V.; Kowalski, M.; Kox, S.; Koyithatta Meethaleveedu, G.; Kral, J.; Králik, I.; Kravčáková, A.; Krelina, M.; Kretz, M.; Krivda, M.; Krizek, F.; Kryshen, E.; Krzewicki, M.; Kubera, A. M.; Kučera, V.; Kucheriaev, Y.; Kugathasan, T.; Kuhn, C.; Kuijer, P. G.; Kulakov, I.; Kumar, J.; Kumar, L.; Kurashvili, P.; Kurepin, A.; Kurepin, A. B.; Kuryakin, A.; Kushpil, S.; Kweon, M. J.; Kwon, Y.; La Pointe, S. L.; La Rocca, P.; Lagana Fernandes, C.; Lakomov, I.; Langoy, R.; Lara, C.; Lardeux, A.; Lattuca, A.; Laudi, E.; Lea, R.; Leardini, L.; Lee, G. R.; Lee, S.; Legrand, I.; Lehnert, J.; Lemmon, R. C.; Lenti, V.; Leogrande, E.; León Monzón, I.; Leoncino, M.; Lévai, P.; Li, S.; Li, X.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Ljunggren, H. M.; Lodato, D. F.; Loenne, P. I.; Loggins, V. R.; Loginov, V.; Loizides, C.; Lopez, X.; López Torres, E.; Lowe, A.; Lu, X.-G.; Luettig, P.; Lunardon, M.; Luparello, G.; Maevskaya, A.; Mager, M.; Mahajan, S.; Mahmood, S. M.; Maire, A.; Majka, R. D.; Malaev, M.; Maldonado Cervantes, I.; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manceau, L.; Manko, V.; Manso, F.; Manzari, V.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Margutti, J.; Marín, A.; Markert, C.; Marquard, M.; Martashvili, I.; Martin, N. A.; Martin Blanco, J.; Martinengo, P.; Martínez, M. I.; Martínez García, G.; Martinez Pedreira, M.; Martynov, Y.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Massacrier, L.; Mastroserio, A.; Matyja, A.; Mayer, C.; Mazer, J.; Mazzoni, M. A.; Mcdonald, D.; Meddi, F.; Menchaca-Rocha, A.; Meninno, E.; Mercado Pérez, J.; Meres, M.; Miake, Y.; Mieskolainen, M. M.; Mikhaylov, K.; Milano, L.; Milosevic, J.; Minervini, L. M.; Mischke, A.; Mishra, A. N.; Miśkowiec, D.; Mitra, J.; Mitu, C. M.; Mohammadi, N.; Mohanty, B.; Molnar, L.; Montaño Zetina, L.; Montes, E.; Morando, M.; Moretto, S.; Morreale, A.; Morsch, A.; Muccifora, V.; Mudnic, E.; Mühlheim, D.; Muhuri, S.; Mukherjee, M.; Müller, H.; Mulligan, J. D.; Munhoz, M. G.; Murray, S.; Musa, L.; Musinsky, J.; Nandi, B. K.; Nania, R.; Nappi, E.; Naru, M. U.; Nattrass, C.; Nayak, K.; Nayak, T. K.; Nazarenko, S.; Nedosekin, A.; Nellen, L.; Ng, F.; Nicassio, M.; Niculescu, M.; Niedziela, J.; Nielsen, B. S.; Nikolaev, S.; Nikulin, S.; Nikulin, V.; Noferini, F.; Nomokonov, P.; Nooren, G.; Norman, J.; Nyanin, A.; Nystrand, J.; Oeschler, H.; Oh, S.; Oh, S. K.; Ohlson, A.; Okatan, A.; Okubo, T.; Olah, L.; Oleniacz, J.; Oliveira Da Silva, A. C.; Oliver, M. H.; Onderwaater, J.; Oppedisano, C.; Ortiz Velasquez, A.; Oskarsson, A.; Otwinowski, J.; Oyama, K.; Ozdemir, M.; Pachmayer, Y.; Pagano, P.; Paić, G.; Pajares, C.; Pal, S. K.; Pan, J.; Pandey, A. K.; Pant, D.; Papikyan, V.; Pappalardo, G. S.; Pareek, P.; Park, W. J.; Parmar, S.; Passfeld, A.; Paticchio, V.; Paul, B.; Pawlak, T.; Peitzmann, T.; Pereira Da Costa, H.; Pereira De Oliveira Filho, E.; Peresunko, D.; Pérez Lara, C. E.; Peskov, V.; Pestov, Y.; Petráček, V.; Petrov, V.; Petrovici, M.; Petta, C.; Piano, S.; Pikna, M.; Pillot, P.; Pinazza, O.; Pinsky, L.; Piyarathna, D. B.; Płoskoń, M.; Planinic, M.; Pluta, J.; Pochybova, S.; Podesta-Lerma, P. L. M.; Poghosyan, M. G.; Polichtchouk, B.; Poljak, N.; Poonsawat, W.; Pop, A.; Porteboeuf-Houssais, S.; Porter, J.; Pospisil, J.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puccio, M.; Puddu, G.; Pujahari, P.; Punin, V.; Putschke, J.; Qvigstad, H.; Rachevski, A.; Raha, S.; Rajput, S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Razazi, V.; Read, K. F.; Real, J. S.; Redlich, K.; Reed, R. J.; Rehman, A.; Reichelt, P.; Reicher, M.; Reidt, F.; Ren, X.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Rettig, F.; Revol, J.-P.; Reygers, K.; Riabov, V.; Ricci, R. A.; Richert, T.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Ristea, C.; Rivetti, A.; Rocco, E.; Rodríguez Cahuantzi, M.; Rodriguez Manso, A.; Røed, K.; Rogochaya, E.; Rohr, D.; Röhrich, D.; Romita, R.; Ronchetti, F.; Ronflette, L.; Rosnet, P.; Rossi, A.; Roukoutakis, F.; Roy, A.; Roy, C.; Roy, P.; Rubio Montero, A. J.; Rui, R.; Russo, R.; Ryabinkin, E.; Ryabov, Y.; Rybicki, A.; Sadovsky, S.; Šafařík, K.; Sahlmuller, B.; Sahoo, P.; Sahoo, R.; Sahoo, S.; Sahu, P. K.; Saini, J.; Sakai, S.; Saleh, M. A.; Salgado, C. A.; Salzwedel, J.; Sambyal, S.; Samsonov, V.; Sanchez Castro, X.; Šándor, L.; Sandoval, A.; Sano, M.; Santagati, G.; Sarkar, D.; Scapparone, E.; Scarlassara, F.; Scharenberg, R. P.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schuchmann, S.; Schukraft, J.; Schulc, M.; Schuster, T.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, R.; Seeder, K. S.; Seger, J. E.; Sekiguchi, Y.; Selyuzhenkov, I.; Senosi, K.; Seo, J.; Serradilla, E.; Sevcenco, A.; Shabanov, A.; Shabetai, A.; Shadura, O.; Shahoyan, R.; Shangaraev, A.; Sharma, A.; Sharma, N.; Shigaki, K.; Shtejer, K.; Sibiriak, Y.; Siddhanta, S.; Sielewicz, K. M.; Siemiarczuk, T.; Silvermyr, D.; Silvestre, C.; Simatovic, G.; Simonetti, G.; Singaraju, R.; Singh, R.; Singha, S.; Singhal, V.; Sinha, B. C.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Slupecki, M.; Smirnov, N.; Snellings, R. J. M.; Snellman, T. W.; Søgaard, C.; Soltz, R.; Song, J.; Song, M.; Song, Z.; Soramel, F.; Sorensen, S.; Spacek, M.; Spiriti, E.; Sputowska, I.; Spyropoulou-Stassinaki, M.; Srivastava, B. K.; Stachel, J.; Stan, I.; Stefanek, G.; Steinpreis, M.; Stenlund, E.; Steyn, G.; Stiller, J. H.; Stocco, D.; Strmen, P.; Suaide, A. A. P.; Sugitate, T.; Suire, C.; Suleymanov, M.; Sultanov, R.; Šumbera, M.; Symons, T. J. M.; Szabo, A.; Szanto de Toledo, A.; Szarka, I.; Szczepankiewicz, A.; Szymanski, M.; Takahashi, J.; Tanaka, N.; Tangaro, M. A.; Tapia Takaki, J. D.; Tarantola Peloni, A.; Tariq, M.; Tarzila, M. G.; Tauro, A.; Tejeda Muñoz, G.; Telesca, A.; Terasaki, K.; Terrevoli, C.; Teyssier, B.; Thäder, J.; Thomas, D.; Tieulent, R.; Timmins, A. R.; Toia, A.; Trogolo, S.; Trubnikov, V.; Trzaska, W. H.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ullaland, K.; Uras, A.; Usai, G. L.; Utrobicic, A.; Vajzer, M.; Vala, M.; Valencia Palomo, L.; Vallero, S.; Van Der Maarel, J.; Van Hoorne, J. W.; van Leeuwen, M.; Vanat, T.; Vande Vyvre, P.; Varga, D.; Vargas, A.; Vargyas, M.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vauthier, A.; Vechernin, V.; Veen, A. M.; Veldhoen, M.; Velure, A.; Venaruzzo, M.; Vercellin, E.; Vergara Limón, S.; Vernet, R.; Verweij, M.; Vickovic, L.; Viesti, G.; Viinikainen, J.; Vilakazi, Z.; Villalobos Baillie, O.; Vinogradov, A.; Vinogradov, L.; Vinogradov, Y.; Virgili, T.; Vislavicius, V.; Viyogi, Y. P.; Vodopyanov, A.; Völkl, M. A.; Voloshin, K.; Voloshin, S. A.; Volpe, G.; von Haller, B.; Vorobyev, I.; Vranic, D.; Vrláková, J.; Vulpescu, B.; Vyushin, A.; Wagner, B.; Wagner, J.; Wang, H.; Wang, M.; Wang, Y.; Watanabe, D.; Weber, M.; Weber, S. G.; Wessels, J. P.; Westerhoff, U.; Wiechula, J.; Wikne, J.; Wilde, M.; Wilk, G.; Wilkinson, J.; Williams, M. C. S.; Windelband, B.; Winn, M.; Yaldo, C. G.; Yamaguchi, Y.; Yang, H.; Yang, P.; Yano, S.; Yasnopolskiy, S.; Yin, Z.; Yokoyama, H.; Yoo, I.-K.; Yurchenko, V.; Yushmanov, I.; Zaborowska, A.; Zaccolo, V.; Zaman, A.; Zampolli, C.; Zanoli, H. J. C.; Zaporozhets, S.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zgura, I. S.; Zhalov, M.; Zhang, H.; Zhang, X.; Zhang, Y.; Zhao, C.; Zhigareva, N.; Zhou, D.; Zhou, Y.; Zhou, Z.; Zhu, H.; Zhu, J.; Zhu, X.; Zichichi, A.; Zimmermann, A.; Zimmermann, M. B.; Zinovjev, G.; Zyzak, M.

2016-01-01

We present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon and the possible Λn ‾ bound state. The search is performed with the ALICE detector in central (0-10%) Pb-Pb collisions at √{sNN} = 2.76 TeV, by invariant mass analysis in the decay modes Λn ‾ → d ‾π+ and H-dibaryon → Λpπ-. No evidence for these bound states is observed. Upper limits are determined at 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. The results are compared to thermal, coalescence and hybrid UrQMD model expectations, which describe correctly the production of other loosely bound states, like the deuteron and the hypertriton.

Search for weakly decaying Λ n - and ΛΛ exotic bound states in central Pb–Pb collisions at s NN = 2.76  TeV

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

Adam, J.; Adamová, D.; Aggarwal, M. M.

Here, we present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon and the possiblemore » $$\\overline{Λn}$$ bound state. The search is performed with the ALICE detector in central (0-10%) Pb-Pb collisions at $$\\sqrt{s}$$$_ {NN}$$ = 2.76 TeV, by invariant mass analysis in the decay modes $$\\overline{Λn}$$ → $$\\bar{d}$$π + and H-dibaryon →Λpπ -. No evidence for these bound states is observed. Upper limits are determined at 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. The results are compared to thermal, coalescence and hybrid UrQMD model expectations, which describe correctly the production of other loosely bound states, like the deuteron and the hypertriton.« less

Search for weakly decaying Λ n - and ΛΛ exotic bound states in central Pb–Pb collisions at s NN = 2.76  TeV

DOE PAGES

Adam, J.; Adamová, D.; Aggarwal, M. M.; ...

2016-11-28

Here, we present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon and the possiblemore » $$\\overline{Λn}$$ bound state. The search is performed with the ALICE detector in central (0-10%) Pb-Pb collisions at $$\\sqrt{s}$$$_ {NN}$$ = 2.76 TeV, by invariant mass analysis in the decay modes $$\\overline{Λn}$$ → $$\\bar{d}$$π + and H-dibaryon →Λpπ -. No evidence for these bound states is observed. Upper limits are determined at 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. The results are compared to thermal, coalescence and hybrid UrQMD model expectations, which describe correctly the production of other loosely bound states, like the deuteron and the hypertriton.« less

Aeroacoustic Duster

NASA Technical Reports Server (NTRS)

Wu, Jun-ru (Inventor); Hitt, Darren (Inventor); Vachon, Nicholas M. (Inventor); Chen, Di (Inventor); Marshall, Jeffrey S. (Inventor)

2016-01-01

The invention disclosed herein provides for high particle removal rate and/or heat transfer from surfaces. The device removes particulate matter from a surface using a bounded vortex generated over the surface, with suction in the vortex center and jets for blowing air along the periphery. The jets are tilted in the tangential direction to induce vortex motion within the suction region. The vortex is said to be bounded because streamlines originating in the downward jets are entrained back into the central vortex.

Analysis of nucleotides and oligonucleotides immobilized as self-assembled monolayers by static secondary ion mass spectrometry.

PubMed

Patrick, J S; Cooks, R G; Pachuta, S J

1994-11-01

Nucleic acid constituents can be bound to a metal surface in the form of self-assembled monolayers. Binding is achieved either through ionic interactions with a self-assembled 2-aminoethanethiol monolayer or by direct covalent binding of a dithiophosphate oligonucleotide to a metal surface through a sulfur-metal bond. Nucleotides, polynucleotides (both normal and a dithiophosphate analog) and double-stranded DNA have all been bound to surfaces. When the surfaces are interrogated using static secondary ion mass spectrometry (SIMS), the surface-bound nucleic acid constituents are observed in the form of the characteristic protonated nucleic acid base ions (BH2+). While a silver foil substrate was found to provide the highest absolute signal, vapor-deposited gold yields the best signal-to-noise ratio for ionically bound deoxyguanosine monophosphate. Under comparable conditions, a Cs+ projectile produces a 10-fold increase in the secondary ion signal relative to a Ga+ projectile. The experiment has been extended to a triple-quadrupole instrument where tandem mass spectrometric experiments on ionically immobilized dGMP showed the characteristic loss of ammonia from the released BH2+ ion. When a 'biomimetic' surface formed by ionically immobilizing double-stranded DNA is exposed to a solution containing ethidium bromide, ions corresponding to the non-covalent adduct are readily detectable using SIMS. This adduct and the nucleic acid constituents can be monitored at levels below 10 fmol.

Shape Complementarity of Protein-Protein Complexes at Multiple Resolutions

PubMed Central

Zhang, Qing; Sanner, Michel; Olson, Arthur J.

2010-01-01

Biological complexes typically exhibit intermolecular interfaces of high shape complementarity. Many computational docking approaches use this surface complementarity as a guide in the search for predicting the structures of protein-protein complexes. Proteins often undergo conformational changes in order to create a highly complementary interface when associating. These conformational changes are a major cause of failure for automated docking procedures when predicting binding modes between proteins using their unbound conformations. Low resolution surfaces in which high frequency geometric details are omitted have been used to address this problem. These smoothed, or blurred, surfaces are expected to minimize the differences between free and bound structures, especially those that are due to side chain conformations or small backbone deviations. In spite of the fact that this approach has been used in many docking protocols, there has yet to be a systematic study of the effects of such surface smoothing on the shape complementarity of the resulting interfaces. Here we investigate this question by computing shape complementarity of a set of 66 protein-protein complexes represented by multi-resolution blurred surfaces. Complexed and unbound structures are available for these protein-protein complexes. They are a subset of complexes from a non-redundant docking benchmark selected for rigidity (i.e. the proteins undergo limited conformational changes between their bound and unbound states). In this work we construct the surfaces by isocontouring a density map obtained by accumulating the densities of Gaussian functions placed at all atom centers of the molecule. The smoothness or resolution is specified by a Gaussian fall-off coefficient, termed “blobbyness”. Shape complementarity is quantified using a histogram of the shortest distances between two proteins' surface mesh vertices for both the crystallographic complexes and the complexes built using the protein structures in their unbound conformation. The histograms calculated for the bound complex structures demonstrate that medium resolution smoothing (blobbyness=−0.9) can reproduce about 88% of the shape complementarity of atomic resolution surfaces. Complexes formed from the free component structures show a partial loss of shape complementarity (more overlaps and gaps) with the atomic resolution surfaces. For surfaces smoothed to low resolution (blobbyness=−0.3), we find more consistency of shape complementarity between the complexed and free cases. To further reduce bad contacts without significantly impacting the good contacts we introduce another blurred surface, in which the Gaussian densities of flexible atoms are reduced. From these results we discuss the use of shape complementarity in protein-protein docking. PMID:18837463

Surface properties of adipocyte lipid-binding protein: Response to lipid binding, and comparison with homologous proteins.

PubMed

LiCata, V J; Bernlohr, D A

1998-12-01

Adipocyte lipid-binding protein (ALBP) is one of a family of intracellular lipid-binding proteins (iLBPs) that bind fatty acids, retinoids, and other hydrophobic ligands. The different members of this family exhibit a highly conserved three-dimensional structure; and where structures have been determined both with (holo) and without (apo) bound lipid, observed conformational changes are extremely small (Banaszak, et al., 1994, Adv. Prot. Chem. 45, 89; Bernlohr, et al., 1997, Annu. Rev. Nutr. 17, 277). We have examined the electrostatic, hydrophobic, and water accessible surfaces of ALBP in the apo form and of holo forms with a variety of bound ligands. These calculations reveal a number of previously unrecognized changes between apo and holo ALBP, including: 1) an increase in the overall protein surface area when ligand binds, 2) expansion of the binding cavity when ligand is bound, 3) clustering of individual residue exposure increases in the area surrounding the proposed ligand entry portal, and 4) ligand-binding dependent variation in the topology of the electrostatic potential in the area surrounding the ligand entry portal. These focused analyses of the crystallographic structures thus reveal a number of subtle but consistent conformational and surface changes that might serve as markers for differential targeting of protein-lipid complexes within the cell. Most changes are consistent from ligand to ligand, however there are some ligand-specific changes. Comparable calculations with intestinal fatty-acid-binding protein and other vertebrate iLBPs show differences in the electrostatic topology, hydrophobic topology, and in localized changes in solvent exposure near the ligand entry portal. These results provide a basis toward understanding the functional and mechanistic differences among these highly structurally homologous proteins. Further, they suggest that iLBPs from different tissues exhibit one of two predominant end-state structural distributions of the ligand entry portal.

S-matrix method for the numerical determination of bound states.

NASA Technical Reports Server (NTRS)

Bhatia, A. K.; Madan, R. N.

1973-01-01

A rapid numerical technique for the determination of bound states of a partial-wave-projected Schroedinger equation is presented. First, one needs to integrate the equation only outwards as in the scattering case, and second, the number of trials necessary to determine the eigenenergy and the corresponding eigenfunction is considerably less than in the usual method. As a nontrivial example of the technique, bound states are calculated in the exchange approximation for the e-/He+ system and l equals 1 partial wave.

On bound-states of the Gross Neveu model with massive fundamental fermions

NASA Astrophysics Data System (ADS)

Frishman, Yitzhak; Sonnenschein, Jacob

2018-01-01

In the search for QFT's that admit boundstates, we reinvestigate the two dimensional Gross-Neveu model, but with massive fermions. By computing the self-energy for the auxiliary boundstate field and the effective potential, we show that there are no bound states around the lowest minimum, but there is a meta-stable bound state around the other minimum, a local one. The latter decays by tunneling. We determine the dependence of its lifetime on the fermion mass and coupling constant.

Bound and resonance states of the dipolar anion of hydrogen cyanide: Competition between threshold effects and rotation in an open quantum system

DOE PAGES

Fossez, K.; Michel, N.; Nazarewicz, W.; ...

2015-01-12

In this paper, bound and resonance states of the dipole-bound anion of hydrogen cyanide HCN – are studied using a nonadiabatic pseudopotential method and the Berggren expansion technique involving bound states, decaying resonant states, and nonresonant scattering continuum. We devise an algorithm to identify the resonant states in the complex energy plane. To characterize spatial distributions of electronic wave functions, we introduce the body-fixed density and use it to assign families of resonant states into collective rotational bands. We find that the nonadiabatic coupling of electronic motion to molecular rotation results in a transition from the strong-coupling to weak-coupling regime.more » In the strong-coupling limit, the electron moving in a subthreshold, spatially extended halo state follows the rotational motion of the molecule. Above the ionization threshold, the electron's motion in a resonance state becomes largely decoupled from molecular rotation. Finally, the widths of resonance-band members depend primarily on the electron orbital angular momentum.« less

Electronic properties of GdxBi2-xSe3 single crystals analyzed by Shubnikov-de Haas oscillations

NASA Astrophysics Data System (ADS)

Kim, Soo-Whan; Jung, Myung-Hwa

2018-05-01

Magnetically doped topological insulators have been significantly researched for unlocking the nontrivial topological phases and the resultant potential applications for spintronics. We report the effect of antiferromagnetic order induced by Gd substitution on the electronic properties of GdxBi2-xSe3 single crystals by analyzing the Shubnikov-de Haas oscillations. Antiferromagnetic order of Gd ions affects the 2D surface state in Bi2Se3 and changes the effective mass and lifetime of charge carriers. These observations suggest a strong correlation of 2D surface electrons with the antiferromagnetic ordering, where the itinerant electrons are bound to the Gd ions to mediate the antiferromagnetic interaction.

Orbital superconductivity, defects, and pinned nematic fluctuations in the doped iron chalcogenide FeSe 0.45 Te 0.55

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

Sarkar, Saheli; Van Dyke, John; Sprau, Peter O.

We demonstrate that the differential conductance, dI/dV, measured via spectroscopic imaging scanning tunneling microscopy in the doped iron chalcogenide FeSe0.45Te0.55, possesses a series of characteristic features that allow one to extract the orbital structure of the superconducting gaps. This yields nearly isotropic superconducting gaps on the two holelike Fermi surfaces, and a strongly anisotropic gap on the electronlike Fermi surface. Moreover, we show that the pinning of nematic fluctuations by defects can give rise to a dumbbell-like spatial structure of the induced impurity bound states, and explains the related C-2 symmetry in the Fourier transformed differential conductance.

Majorana bound states in the finite-length chain

NASA Astrophysics Data System (ADS)

Zvyagin, A. A.

2015-08-01

Recent experiments investigating edge states in ferromagnetic atomic chains on superconducting substrate are analyzed. In particular, finite size effects are considered. It is shown how the energy of the Majorana bound state depends on the length of the chain, as well as on the parameters of the model. Oscillations of the energy of the bound edge state in the chain as a function of the length of the chain, and as a function of the applied voltage (or the chemical potential) are studied. In particular, it has been shown that oscillations can exist only for some values of the effective potential.

Evolution of complexity following a global quench

NASA Astrophysics Data System (ADS)

Moosa, Mudassir

2018-03-01

The rate of complexification of a quantum state is conjectured to be bounded from above by the average energy of the state. A different conjecture relates the complexity of a holographic CFT state to the on-shell gravitational action of a certain bulk region. We use `complexity equals action' conjecture to study the time evolution of the complexity of the CFT state after a global quench. We find that the rate of growth of complexity is not only consistent with the conjectured bound, but it also saturates the bound soon after the system has achieved local equilibrium.

Shooting quasiparticles from Andreev bound states in a superconducting constriction

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

Riwar, R.-P.; Houzet, M.; Meyer, J. S.

2014-12-15

A few-channel superconducting constriction provides a set of discrete Andreev bound states that may be populated with quasiparticles. Motivated by recent experimental research, we study the processes in an a.c. driven constriction whereby a quasiparticle is promoted to the delocalized states outside the superconducting gap and flies away. We distinguish two processes of this kind. In the process of ionization, a quasiparticle present in the Andreev bound state is transferred to the delocalized states leaving the constriction. The refill process involves two quasiparticles: one flies away while another one appears in the Andreev bound state. We notice an interesting asymmetrymore » of these processes. The electron-like quasiparticles are predominantly emitted to one side of the constriction while the hole-like ones are emitted to the other side. This produces a charge imbalance of accumulated quasiparticles, that is opposite on opposite sides of the junction. The imbalance may be detected with a tunnel contact to a normal metal lead.« less

Recruiting physisorbed water in surface polymerization for bio-inspired materials of tunable hydrophobicity

DOE PAGES

Oyola-Reynoso, S.; Tevis, I. D.; Chen, J.; ...

2016-08-18

Here, chemical grafting has been widely used to modify the surface properties of materials, especially surface energy for controlled wetting, because of the resilience of such coatings/modifications. Reagents with multiple reactive sites have been used with the expectation that a monolayer will form. The step-growth polymerization mechanism, however, suggests the possibility of gel formation for hydrolyzable moieties in the presence of physisorbed water. In this report, we demonstrated that using alkyltrichlorosilanes (trivalent [i.e., 3 reactive sites]) in the surface modification of a cellulosic material (paper) does not yield a monolayer but rather gives surface-bound particles. We infer that the presencemore » of physisorbed (surface-bound) water allows for polymerization (or oligomerization) of the silane prior to its attachment on the surface. Surface energy mismatch between the hydrophobic tails of the growing polymer and any unreacted bound water leads to the assembly of the polymerizing material into spherical particles to minimize surface tension. By varying paper grammage (16.2–201.4 g m –2), we varied the accessible surface area and thus the amount of surface-adsorbed water, allowing us to control the ratio of the silane to the bound water. Using this approach, polymeric particles were formed on the surface of cellulose fibers ranging from ~70 nm to a film. The hydrophobicity of the surface, as determined by water contact angles, correlates with particle sizes (p < 0.001, Student's t-test), and, hence, the hydrophobicity can be tuned (contact angle between 94° and 149°). Using a model structure of a house, we demonstrated that as a result of this modification, paper-based houses can be rendered self-cleaning or tolerant to surface running water. In another application, we demonstrated that the felicitous choice of architectural design allows for the hydrophobic paper to be used for water harvesting.« less

Low-dimensional Representation of Error Covariance

NASA Technical Reports Server (NTRS)

Tippett, Michael K.; Cohn, Stephen E.; Todling, Ricardo; Marchesin, Dan

2000-01-01

Ensemble and reduced-rank approaches to prediction and assimilation rely on low-dimensional approximations of the estimation error covariances. Here stability properties of the forecast/analysis cycle for linear, time-independent systems are used to identify factors that cause the steady-state analysis error covariance to admit a low-dimensional representation. A useful measure of forecast/analysis cycle stability is the bound matrix, a function of the dynamics, observation operator and assimilation method. Upper and lower estimates for the steady-state analysis error covariance matrix eigenvalues are derived from the bound matrix. The estimates generalize to time-dependent systems. If much of the steady-state analysis error variance is due to a few dominant modes, the leading eigenvectors of the bound matrix approximate those of the steady-state analysis error covariance matrix. The analytical results are illustrated in two numerical examples where the Kalman filter is carried to steady state. The first example uses the dynamics of a generalized advection equation exhibiting nonmodal transient growth. Failure to observe growing modes leads to increased steady-state analysis error variances. Leading eigenvectors of the steady-state analysis error covariance matrix are well approximated by leading eigenvectors of the bound matrix. The second example uses the dynamics of a damped baroclinic wave model. The leading eigenvectors of a lowest-order approximation of the bound matrix are shown to approximate well the leading eigenvectors of the steady-state analysis error covariance matrix.

Phonon coupling in optical transitions for singlet-triplet pairs of bound excitons in semiconductors

NASA Astrophysics Data System (ADS)

Pistol, M. E.; Monemar, B.

1986-05-01

A model is presented for the observed strong difference in selection rules for coupling of phonons in the one-phonon sideband of optical spectra related to bound excitons in semiconductors. The present treatment is specialized to the case of a closely spaced pair of singlet-triplet character as the lowest electronic states, as is common for bound excitons associated with neutral complexes in materials like GaP and Si. The optical transition for the singlet bound-exciton state is found to couple strongly only to symmetric A1 modes. The triplet state has a similar coupling strength to A1 modes, but in addition strong contributions are found for replicas corresponding to high-density-of-states phonons TAX, LAX, and TOX. This can be explained by a treatment of particle-phonon coupling beyond the ordinary adiabatic approximation. A weak mixing between the singlet and triplet states is mediated by the phonon coupling, as described in first-order perturbation theory. The model derived in this work, for such phonon-induced mixing of closely spaced electronic states, is shown to explain the observed phonon coupling for several bound-exciton systems of singlet-triplet character in GaP. In addition, the observed oscillator strength of the forbidden triplet state may be explained as partly derived from phonon-induced mixing with the singlet state, which has a much larger oscillator strength.

Deformation of Fluid Column by Action of Axial Vibration and Some Aspects of High-Rate Thermocapillary Convection

NASA Technical Reports Server (NTRS)

Feonychev, Alexander I.; Kalachinskaya, Irina S.; Pokhilko, Victor I.

1996-01-01

The deformation of the fluid column by an action of a low-frequency vibration is considered. It is shown that behavior of the free fluid surface depends on the frequency of applied vibration and its amplitude. In the area of very low frequencies when fluid has time to comment on travel of bounding solid walls limiting column, the harmonical oscillations of free surface with given frequency are observed. With increase of vibration frequency the steady-state relief on free fluid surface is formed. If the amplitude of vibration is very small and the frequency corresponding to the first peak in the vibration spectrum on the Mir orbital station, the deformation of free surface tends to zero. Fluid flow induced thermocapillary effect on deformed free surface is more unstable as in the case of smooth cylindrical surface. It was shown that width of heating zone affects very essentially the flow pattern and transition to oscillatory regime of thermocapillary convection.

Optical emission generated by collisions of 5 eV O(3P) atoms with surface-absorbed hydrazine

NASA Technical Reports Server (NTRS)

Orient, O. J.; Martus, K. E.; Chutjian, A.; Murad, E.

1992-01-01

Optical emission has been observed corresponding to vibrational bands in the NH (A 3Pi - X 3Sigma(-)) electronic transition during collisions of 5 eV, ground-state oxygen O(3P) atoms with MgF2 and Ni surfaces continuously exposed to a beam of hydrazine (N2H4). The NH emission intensity is observed to be about five times greater for MgF2 than for Ni. No dependence on temperature was observed for either surface in the range 240 - 340 K, implying that the NH-producing intermediate species is tightly bound. The half-lifetime for desorption of hydrazine from each surface was measured. This was found to be 120 min for the MgF2 surface at 240 K, and less than 20 min for Ni. After exposure, the surface composition was measured using X-ray photoelectron spectroscopy on the exposed and unexposed areas of both targets.

Electromers of the benzene dimer radical cation.

PubMed

Błoch-Mechkour, Anna; Bally, Thomas

2015-04-28

The well-studied benzene dimer radical cation, which is prototypical for this class of species, has been reinvestigated computationally. Thereby it turned out that both the σ-hemibonded and the half-shifted sandwich structures of the benzene dimer cation, which had been independently proposed, represent stationary points on the B2PLYP-D potential energy surfaces. However, these structures belong to distinct electronic states, both of which are associated with potential surfaces that are very flat with regard to rotation of the two benzene rings in an opposite sense relative to each other. The surfaces of these two "electromers" of the benzene dimer cation are separated by only 3-4 kcal mol(-1) and do not intersect along the rotation coordinate, which represents a rather unique electronic structure situation. When moving on either of the two surfaces the title complex is an extremely fluxional species, in spite of its being bound by over 20 kcal mol(-1).

Electrostatic rate enhancement and transient complex of protein-protein association.

PubMed

Alsallaq, Ramzi; Zhou, Huan-Xiang

2008-04-01

The association of two proteins is bounded by the rate at which they, via diffusion, find each other while in appropriate relative orientations. Orientational constraints restrict this rate to approximately 10(5)-10(6) M(-1) s(-1). Proteins with higher association rates generally have complementary electrostatic surfaces; proteins with lower association rates generally are slowed down by conformational changes upon complex formation. Previous studies (Zhou, Biophys J 1997;73:2441-2445) have shown that electrostatic enhancement of the diffusion-limited association rate can be accurately modeled by $k_{\\bf D}$ = $k_{D}0\\ {exp} ( - \\langle U_{el} \\rangle;{\\star}/k_{B} T),$ where k(D) and k(D0) are the rates in the presence and absence of electrostatic interactions, respectively, U(el) is the average electrostatic interaction energy in a "transient-complex" ensemble, and k(B)T is the thermal energy. The transient-complex ensemble separates the bound state from the unbound state. Predictions of the transient-complex theory on four protein complexes were found to agree well with the experiment when the electrostatic interaction energy was calculated with the linearized Poisson-Boltzmann (PB) equation (Alsallaq and Zhou, Structure 2007;15:215-224). Here we show that the agreement is further improved when the nonlinear PB equation is used. These predictions are obtained with the dielectric boundary defined as the protein van der Waals surface. When the dielectric boundary is instead specified as the molecular surface, electrostatic interactions in the transient complex become repulsive and are thus predicted to retard association. Together these results demonstrate that the transient-complex theory is predictive of electrostatic rate enhancement and can help parameterize PB calculations. (c) 2007 Wiley-Liss, Inc.

Ligand-modified metal clusters for gas separation and purification

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

Okrut, Alexander; Ouyang, Xiaoying; Runnebaum, Ron

2017-02-21

Provided is an organic ligand-bound metal surface that selects one gaseous species over another. The species can be closely sized molecular species having less than 1 Angstrom difference in kinetic diameter. In one embodiment, the species comprise carbon monoxide and ethylene. Such organic ligand-bound metal surfaces can be successfully used in gas phase separations or purifications, sensing, and in catalysis.

Entropic (de)stabilization of surface-bound peptides conjugated with polymers

NASA Astrophysics Data System (ADS)

Carmichael, Scott P.; Shell, M. Scott

2015-12-01

In many emerging biotechnologies, functional proteins must maintain their native structures on or near interfaces (e.g., tethered peptide arrays, protein coated nanoparticles, and amphiphilic peptide micelles). Because the presence of a surface is known to dramatically alter the thermostability of tethered proteins, strategies to stabilize surface-bound proteins are highly sought. Here, we show that polymer conjugation allows for significant control over the secondary structure and thermostability of a model surface-tethered peptide. We use molecular dynamics simulations to examine the folding behavior of a coarse-grained helical peptide that is conjugated to polymers of various lengths and at various conjugation sites. These polymer variations reveal surprisingly diverse behavior, with some stabilizing and some destabilizing the native helical fold. We show that ideal-chain polymer entropies explain these varied effects and can quantitatively predict shifts in folding temperature. We then develop a generic theoretical model, based on ideal-chain entropies, that predicts critical lengths for conjugated polymers to effect changes in the folding of a surface-bound protein. These results may inform new design strategies for the stabilization of surface-associated proteins important for a range technological applications.

Entropic (de)stabilization of surface-bound peptides conjugated with polymers.

PubMed

Carmichael, Scott P; Shell, M Scott

2015-12-28

In many emerging biotechnologies, functional proteins must maintain their native structures on or near interfaces (e.g., tethered peptide arrays, protein coated nanoparticles, and amphiphilic peptide micelles). Because the presence of a surface is known to dramatically alter the thermostability of tethered proteins, strategies to stabilize surface-bound proteins are highly sought. Here, we show that polymer conjugation allows for significant control over the secondary structure and thermostability of a model surface-tethered peptide. We use molecular dynamics simulations to examine the folding behavior of a coarse-grained helical peptide that is conjugated to polymers of various lengths and at various conjugation sites. These polymer variations reveal surprisingly diverse behavior, with some stabilizing and some destabilizing the native helical fold. We show that ideal-chain polymer entropies explain these varied effects and can quantitatively predict shifts in folding temperature. We then develop a generic theoretical model, based on ideal-chain entropies, that predicts critical lengths for conjugated polymers to effect changes in the folding of a surface-bound protein. These results may inform new design strategies for the stabilization of surface-associated proteins important for a range technological applications.

Real-time spectral interferometry probes the internal dynamics of femtosecond soliton molecules

NASA Astrophysics Data System (ADS)

Herink, G.; Kurtz, F.; Jalali, B.; Solli, D. R.; Ropers, C.

2017-04-01

Solitons, particle-like excitations ubiquitous in many fields of physics, have been shown to exhibit bound states akin to molecules. The formation of such temporal soliton bound states and their internal dynamics have escaped direct experimental observation. By means of an emerging time-stretch technique, we resolve the evolution of femtosecond soliton molecules in the cavity of a few-cycle mode-locked laser. We track two- and three-soliton bound states over hundreds of thousands of consecutive cavity roundtrips, identifying fixed points and periodic and aperiodic molecular orbits. A class of trajectories acquires a path-dependent geometrical phase, implying that its dynamics may be topologically protected. These findings highlight the importance of real-time detection in resolving interactions in complex nonlinear systems, including the dynamics of soliton bound states, breathers, and rogue waves.

Internal structure of acceptor-bound excitons in wide-band-gap wurtzite semiconductors

NASA Astrophysics Data System (ADS)

Gil, Bernard; Bigenwald, Pierre; Paskov, Plamen P.; Monemar, Bo

2010-02-01

We describe the internal structure of acceptor-bound excitons in wurtzite semiconductors. Our approach consists in first constructing, in the context of angular momentum algebra, the wave functions of the two-hole system that fulfill Pauli’s exclusion’s principle. Second, we construct the acceptor-bound exciton states by adding the electron states in a similar manner that two-hole states are constructed. We discuss the optical selection rules for the acceptor-bound exciton recombination. Finally, we compare our theory with experimental data for CdS and GaN. In the specific case of CdS for which much experimental information is available, we demonstrate that, compared with cubic semiconductors, the sign of the short-range hole-exchange interaction is reversed and more than one order of magnitude larger. The whole set of data is interpreted in the context of a large value of the short-range hole-exchange interaction Ξ0=3.4±0.2meV . This value dictates the splitting between the ground-state line I1 and the other transitions. The values we find for the electron-hole spin-exchange interaction and of the crystal-field splitting of the two-hole state are, respectively, -0.4±0.1 and 0.2±0.1meV . In the case of GaN, the experimental data for the acceptor-bound excitons in the case of Mg and Zn acceptors, show more than one bound-exciton line. We discuss a possible assignment of these states.

Monitoring solute interactions with poly(ethylene oxide)-modified colloidal silica nanoparticles via fluorescence anisotropy decay.

PubMed

Tleugabulova, Dina; Duft, Andy M; Brook, Michael A; Brennan, John D

2004-01-06

The fluorescence-based nanosize metrology approach, proposed recently by Geddes and Birch (Geddes, C. D.; Birch, D. J. S. J. Non-Cryst. Solids 2000, 270, 191), was used to characterize the extent of binding of a fluorescent cationic solute, rhodamine 6G (R6G), to the surface of silica particles after modification of the surface with the hydrophilic polymer poly(ethylene oxide) (PEO) of various molecular weights. The measurement of the rotational dynamics of R6G in PEO solutions showed the absence of strong interactions between R6G and PEO chains in water and the ability of the dye to sense the presence of polymer clusters in 30 wt % solutions. Time-resolved anisotropy decays of polymer-modified Ludox provided direct evidence for distribution of the dye between bound and free states, with the bound dye showing two decay components: a nanosecond decay component that is consistent with local motions of bound probes and a residual anisotropy component due to slow rotation of large silica particles. The data showed that the dye was strongly adsorbed to unmodified silica nanoparticles, to the extent that less than 1% of the dye was present in the surrounding aqueous solution. Addition of PEO blocked the adsorption of the dye to a significant degree, with up to 50% of the probe being present in the aqueous solution for Ludox samples containing 30 wt % of low molecular weight PEO. The addition of such agents also decreased the value and increased the fractional contribution of the nanosecond rotational correlation time, suggesting that polymer adsorption altered the degree of local motion of the bound probe. Atomic force microscopy imaging studies provided no evidence for a change in the particle size upon surface modification but did suggest interparticle aggregation after polymer adsorption. Thus, this redistribution of the probe is interpreted as being due to coverage of particles with the polymer, resulting in lower adsorption of R6G to the silica. The data clearly show the power of time-resolved fluorescence anisotropy decay measurements for probing the modification of silica surfaces and suggest that this method should prove useful in characterization of new chromatographic stationary phases and nanocomposite materials.

Explicit formula for the Holevo bound for two-parameter qubit-state estimation problem

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

Suzuki, Jun, E-mail: junsuzuki@uec.ac.jp

The main contribution of this paper is to derive an explicit expression for the fundamental precision bound, the Holevo bound, for estimating any two-parameter family of qubit mixed-states in terms of quantum versions of Fisher information. The obtained formula depends solely on the symmetric logarithmic derivative (SLD), the right logarithmic derivative (RLD) Fisher information, and a given weight matrix. This result immediately provides necessary and sufficient conditions for the following two important classes of quantum statistical models; the Holevo bound coincides with the SLD Cramér-Rao bound and it does with the RLD Cramér-Rao bound. One of the important results ofmore » this paper is that a general model other than these two special cases exhibits an unexpected property: the structure of the Holevo bound changes smoothly when the weight matrix varies. In particular, it always coincides with the RLD Cramér-Rao bound for a certain choice of the weight matrix. Several examples illustrate these findings.« less

Atom-field dressed states in slow-light waveguide QED

NASA Astrophysics Data System (ADS)

Calajó, Giuseppe; Ciccarello, Francesco; Chang, Darrick; Rabl, Peter

2016-03-01

We discuss the properties of atom-photon bound states in waveguide QED systems consisting of single or multiple atoms coupled strongly to a finite-bandwidth photonic channel. Such bound states are formed by an atom and a localized photonic excitation and represent the continuum analog of the familiar dressed states in single-mode cavity QED. Here we present a detailed analysis of the linear and nonlinear spectral features associated with single- and multiphoton dressed states and show how the formation of bound states affects the waveguide-mediated dipole-dipole interactions between separated atoms. Our results provide both a qualitative and quantitative description of the essential strong-coupling processes in waveguide QED systems, which are currently being developed in the optical and microwave regimes.

W-Z-top-quark bags

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

Crichigno, Marcos P.; Shuryak, Edward; Flambaum, Victor V.

2010-10-01

We discuss a new family of multiquanta-bound states in the standard model which exist due to the mutual Higgs-based attraction of the heaviest members of the standard model, namely, gauge quanta W, Z, and (anti)top quarks, t, t. We use a self-consistent mean-field approximation, up to a rather large particle number N. In this paper we do not focus on weakly bound, nonrelativistic bound states, but rather on 'bags' in which the Higgs vacuum expectation value is significantly modified or depleted. The minimal number N above which such states appear strongly depends on the ratio of the Higgs mass tomore » the masses of W, Z, t, t: For a light Higgs mass, m{sub H{approx}}50 GeV, bound states start from N{approx}O(10), but for a ''realistic'' Higgs mass, m{sub H{approx}}100 GeV, one finds metastable/bound W, Z bags only for N{approx}O(1000). We also found that in the latter case pure top bags disappear for all N, although top quarks can still be well bound to the W bags. Anticipating the cosmological applications (discussed in the following Article [Phys. Rev. D 82, 073019]) of these bags as 'doorway states' for baryosynthesis, we also consider here the existence of such metastable bags at finite temperatures, when standard-model parameters such as Higgs, gauge, and top masses are significantly modified.« less

The bound states of ultracold KRb molecules

NASA Astrophysics Data System (ADS)

Julienne, Paul; Hanna, Thomas

2009-03-01

Recently ultracold vibrational ground state ^40K^87Rb polar molecules have been made using magnetoassociation of two cold atoms to a weakly bound Feshbach molecule, followed by a two-color optical STIRAP process to transfer molecules to the molecular ground state [1]. We have used accurate potential energy curves for the singlet and triplet states of the KRb molecule [2] with coupled channels calculations to calculate all of the bound states of the ^40K^87Rb molecule as a function of magnetic field from the cold atom collision threshold to the v=0 ground state. We have also developed approximate models for understanding the changing properties of the molecular bound states as binding energy increases. Some overall conclusions from these calculations will be presented. [1] K.-K. Ni, S. Ospelkaus, M. H. G. de Miranda, A. Peer, B. Neyenhuis, J. J. Zirbel, S. Kotochigova, P. S. Julienne, D. S. Jin, and J. Ye, Science, 2008, 322, 231--235. [2] A. Pashov, O. Docenko, M. Tamanis, R. Ferber, H. Kn"ockel, and E. Tiemann, Phys. Rev. A, 2007, 76, 022511.

Resolving the Spatial Structures of Bound Hole States in Black Phosphorus.

PubMed

Qiu, Zhizhan; Fang, Hanyan; Carvalho, Alexandra; Rodin, A S; Liu, Yanpeng; Tan, Sherman J R; Telychko, Mykola; Lv, Pin; Su, Jie; Wang, Yewu; Castro Neto, A H; Lu, Jiong

2017-11-08

Understanding the local electronic properties of individual defects and dopants in black phosphorus (BP) is of great importance for both fundamental research and technological applications. Here, we employ low-temperature scanning tunnelling microscope (LT-STM) to probe the local electronic structures of single acceptors in BP. We demonstrate that the charge state of individual acceptors can be reversibly switched by controlling the tip-induced band bending. In addition, acceptor-related resonance features in the tunnelling spectra can be attributed to the formation of Rydberg-like bound hole states. The spatial mapping of the quantum bound states shows two distinct shapes evolving from an extended ellipse shape for the 1s ground state to a dumbbell shape for the 2p x excited state. The wave functions of bound hole states can be well-described using the hydrogen-like model with anisotropic effective mass, corroborated by our theoretical calculations. Our findings not only provide new insight into the many-body interactions around single dopants in this anisotropic two-dimensional material but also pave the way to the design of novel quantum devices.

Non-Abelian fermion parity interferometry of Majorana bound states in a Fermi sea

NASA Astrophysics Data System (ADS)

Dahan, Daniel; Tanhayi Ahari, Mostafa; Ortiz, Gerardo; Seradjeh, Babak; Grosfeld, Eytan

We study the quantum dynamics of Majorana and regular fermion bound states coupled to a one-dimensional lead. The dynamics following the quench in the coupling to the lead exhibits a series of dynamical revivals as the bound state propagates in the lead and reflects from the boundaries. We show that the nature of revivals for a single Majorana bound state depends uniquely on the presence of a resonant level in the lead. When two spatially separated Majorana modes are coupled to the lead, the revivals depend only on the phase difference between their host superconductors. Remarkably, the quench in this case effectively performs a fermion-parity interferometry between Majorana bound states, revealing their unique non-Abelian braiding. Using both analytical and numerical techniques, we find the pattern of fermion parity transfers following the quench, study its evolution in the presence of disorder and interactions, and thus, ascertain the fate of Majorana in a rough Fermi sea. Work supported in part by BSF Grant No. 2014345, ISF Grant Nos. 401/12 and 1626/16, EU Seventh Framework Programme (FP7/2007-2013) Grant No. 303742, NSF CAREER Grant DMR-1350663 and the College of Arts and Sciences at Indiana University.

The hyperbolic step potential: Anti-bound states, SUSY partners and Wigner time delays

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

Gadella, M.; Kuru, Ş.; Negro, J., E-mail: jnegro@fta.uva.es

We study the scattering produced by a one dimensional hyperbolic step potential, which is exactly solvable and shows an unusual interest because of its asymmetric character. The analytic continuation of the scattering matrix in the momentum representation has a branch cut and an infinite number of simple poles on the negative imaginary axis which are related with the so called anti-bound states. This model does not show resonances. Using the wave functions of the anti-bound states, we obtain supersymmetric (SUSY) partners which are the series of Rosen–Morse II potentials. We have computed the Wigner reflection and transmission time delays formore » the hyperbolic step and such SUSY partners. Our results show that the more bound states a partner Hamiltonian has the smaller is the time delay. We also have evaluated time delays for the hyperbolic step potential in the classical case and have obtained striking similitudes with the quantum case. - Highlights: • The scattering matrix of hyperbolic step potential is studied. • The scattering matrix has a branch cut and an infinite number of poles. • The poles are associated to anti-bound states. • Susy partners using antibound states are computed. • Wigner time delays for the hyperbolic step and partner potentials are compared.« less

Microfluidic Channels on Nanopatterned Substrates: Monitoring Protein Binding to Lipid Bilayers with Surface-Enhanced Raman Spectroscopy

PubMed Central

Banerjee, Amrita; Perez-Castillejos, R.; Hahn, D.; Smirnov, Alex I.; Grebel, H.

2013-01-01

We used Surface Enhanced Raman Spectroscopy (SERS) to detect binding events between streptavidin and biotinylated lipid bilayers. The binding events took place at the surface between microfluidic channels and anodized aluminum oxide (AAO) with the latter serving as substrates. The bilayers were incorporated in the substrate pores. It was revealed that non-bound molecules were easily washed away and that large suspended cells (Salmonella enterica) are less likely to interfere with the monitoring process: when focusing to the lower surface of the channel, one may resolve mostly the bound molecules. PMID:24932024

Micro-fluidic channels on nanopatterned substrates: Monitoring protein binding to lipid bilayers with surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Banerjee, Amrita; Perez-Castillejos, R.; Hahn, D.; Smirnov, Alex I.; Grebel, H.

2010-04-01

We used surface-enhanced Raman spectroscopy (SERS) to detect binding events between streptavidin and biotinylated lipid bilayers. The binding events took place at the surface between micro-fluidic channels and anodized aluminum oxide (AAO) with the latter serving as substrates. The bilayers were incorporated in the substrate pores. It was revealed that non-bound molecules were easily washed away and that large suspended cells ( Salmonella enterica) are less likely to interfere with the monitoring process: when focusing to the lower surface of the channel, one may resolve mostly the bound molecules.

Electron accommodation dynamics in the DNA base thymine

NASA Astrophysics Data System (ADS)

King, Sarah B.; Stephansen, Anne B.; Yokoi, Yuki; Yandell, Margaret A.; Kunin, Alice; Takayanagi, Toshiyuki; Neumark, Daniel M.

2015-07-01

The dynamics of electron attachment to the DNA base thymine are investigated using femtosecond time-resolved photoelectron imaging of the gas phase iodide-thymine (I-T) complex. An ultraviolet pump pulse ejects an electron from the iodide and prepares an iodine-thymine temporary negative ion that is photodetached with a near-IR probe pulse. The resulting photoelectrons are analyzed with velocity-map imaging. At excitation energies ranging from -120 meV to +90 meV with respect to the vertical detachment energy (VDE) of 4.05 eV for I-T, both the dipole-bound and valence-bound negative ions of thymine are observed. A slightly longer rise time for the valence-bound state than the dipole-bound state suggests that some of the dipole-bound anions convert to valence-bound species. No evidence is seen for a dipole-bound anion of thymine at higher excitation energies, in the range of 0.6 eV above the I-T VDE, which suggests that if the dipole-bound anion acts as a "doorway" to the valence-bound anion, it only does so at excitation energies near the VDE of the complex.

Electron accommodation dynamics in the DNA base thymine.

PubMed

King, Sarah B; Stephansen, Anne B; Yokoi, Yuki; Yandell, Margaret A; Kunin, Alice; Takayanagi, Toshiyuki; Neumark, Daniel M

2015-07-14

The dynamics of electron attachment to the DNA base thymine are investigated using femtosecond time-resolved photoelectron imaging of the gas phase iodide-thymine (I(-)T) complex. An ultraviolet pump pulse ejects an electron from the iodide and prepares an iodine-thymine temporary negative ion that is photodetached with a near-IR probe pulse. The resulting photoelectrons are analyzed with velocity-map imaging. At excitation energies ranging from -120 meV to +90 meV with respect to the vertical detachment energy (VDE) of 4.05 eV for I(-)T, both the dipole-bound and valence-bound negative ions of thymine are observed. A slightly longer rise time for the valence-bound state than the dipole-bound state suggests that some of the dipole-bound anions convert to valence-bound species. No evidence is seen for a dipole-bound anion of thymine at higher excitation energies, in the range of 0.6 eV above the I(-)T VDE, which suggests that if the dipole-bound anion acts as a "doorway" to the valence-bound anion, it only does so at excitation energies near the VDE of the complex.

Tightening the entropic uncertainty bound in the presence of quantum memory

NASA Astrophysics Data System (ADS)

Adabi, F.; Salimi, S.; Haseli, S.

2016-06-01

The uncertainty principle is a fundamental principle in quantum physics. It implies that the measurement outcomes of two incompatible observables cannot be predicted simultaneously. In quantum information theory, this principle can be expressed in terms of entropic measures. M. Berta et al. [Nat. Phys. 6, 659 (2010), 10.1038/nphys1734] have indicated that uncertainty bound can be altered by considering a particle as a quantum memory correlating with the primary particle. In this article, we obtain a lower bound for entropic uncertainty in the presence of a quantum memory by adding an additional term depending on the Holevo quantity and mutual information. We conclude that our lower bound will be tightened with respect to that of Berta et al. when the accessible information about measurements outcomes is less than the mutual information about the joint state. Some examples have been investigated for which our lower bound is tighter than Berta et al.'s lower bound. Using our lower bound, a lower bound for the entanglement of formation of bipartite quantum states has been obtained, as well as an upper bound for the regularized distillable common randomness.

33 CFR 151.2040 - What are the mandatory ballast water management requirements for vessels equipped with ballast...

Code of Federal Regulations, 2010 CFR

2010-07-01

... United States and are bound for ports or places in the United States? 151.2040 Section 151.2040... Water Management for Control of Nonindigenous Species in Waters of the United States § 151.2040 What are... operate in the waters of the United States and are bound for ports or places in the United States? (a) A...

The limits of the nuclear landscape explored by the relativistic continuum Hartree–Bogoliubov theory

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

Xia, X. W.; Lim, Y.; Zhao, P. W.

The ground-state properties of nuclei with 8more » $$\\leqslant$$ Z $$\\leqslant$$ 120 from the proton drip line to the neutron drip line have been investigated using the relativistic continuum Hartree-Bogoliubov (RCHB) theory with the relativistic density functional PC-PK1. With the effects of the continuum included, there are totally 9035 nuclei predicted to be bound, which largely extends the existing nuclear landscapes predicted with other methods. The calculated binding energies, separation energies, neutron and proton Fermi surfaces, root-mean-square (rms) radii of neutron, proton, matter, and charge distributions, ground-state spins and parities are tabulated. The extension of the nuclear landscape obtained with RCHB is discussed in detail, in particular for the neutron-rich side, in comparison with the relativistic mean field calculations without pairing correlations and also other predicted landscapes. Here, it is found that the coupling between the bound states and the continuum due to the pairing correlations plays an essential role in extending the nuclear landscape. The systematics of the separation energies, radii, densities, potentials and pairing energies of the RCHB calculations are also discussed. In addition, the α-decay energies and proton emitters based on the RCHB calculations are investigated.« less

Vortices and gate-tunable bound states in a topological insulator coupled to superconducting leads

NASA Astrophysics Data System (ADS)

Finck, Aaron; Kurter, C.; Hor, Y. S.; van Harlingen, D. J.

2014-03-01

It has been predicted that zero energy Majorana bound states can be found in the core of vortices within topological superconductors. Here, we report on Andreev spectroscopy measurements of the topological insulator Bi2Se3 with a normal metal lead and one or more niobium leads. The niobium induces superconductivity in the Bi2Se3 through the proximity effect, leading to both signatures of Andreev reflection and a prominent re-entrant resistance effect. When a large magnetic field is applied perpendicular to the surface of the Bi2Se3, we observe multiple abrupt changes in the subgap conductance that are accompanied by sharp peaks in the dynamical resistance. These peaks are very sensitive to changes in magnetic field and disappear at temperatures associated with the critical temperature of the induced superconductivity. The appearance of the transitions and peaks can be tuned by a top gate. At high magnetic fields, we also find evidence of gate-tunable states, which can lead to stable zero-bias conductance peaks. We interpret our results in terms of a transition occurring within the proximity effect region of the topological insulator, likely due to the formation of vortices. We acknowledge support from Microsoft Project Q.

The limits of the nuclear landscape explored by the relativistic continuum Hartree–Bogoliubov theory

DOE PAGES

Xia, X. W.; Lim, Y.; Zhao, P. W.; ...

2017-11-01

The ground-state properties of nuclei with 8more » $$\\leqslant$$ Z $$\\leqslant$$ 120 from the proton drip line to the neutron drip line have been investigated using the relativistic continuum Hartree-Bogoliubov (RCHB) theory with the relativistic density functional PC-PK1. With the effects of the continuum included, there are totally 9035 nuclei predicted to be bound, which largely extends the existing nuclear landscapes predicted with other methods. The calculated binding energies, separation energies, neutron and proton Fermi surfaces, root-mean-square (rms) radii of neutron, proton, matter, and charge distributions, ground-state spins and parities are tabulated. The extension of the nuclear landscape obtained with RCHB is discussed in detail, in particular for the neutron-rich side, in comparison with the relativistic mean field calculations without pairing correlations and also other predicted landscapes. Here, it is found that the coupling between the bound states and the continuum due to the pairing correlations plays an essential role in extending the nuclear landscape. The systematics of the separation energies, radii, densities, potentials and pairing energies of the RCHB calculations are also discussed. In addition, the α-decay energies and proton emitters based on the RCHB calculations are investigated.« less

Thermal dark matter co-annihilating with a strongly interacting scalar

NASA Astrophysics Data System (ADS)

Biondini, S.; Laine, M.

2018-04-01

Recently many investigations have considered Majorana dark matter co-annihilating with bound states formed by a strongly interacting scalar field. However only the gluon radiation contribution to bound state formation and dissociation, which at high temperatures is subleading to soft 2 → 2 scatterings, has been included. Making use of a non-relativistic effective theory framework and solving a plasma-modified Schrödinger equation, we address the effect of soft 2 → 2 scatterings as well as the thermal dissociation of bound states. We argue that the mass splitting between the Majorana and scalar field has in general both a lower and an upper bound, and that the dark matter mass scale can be pushed at least up to 5…6TeV.

Protein immobilization onto various surfaces using a polymer-bound isocyanate

NASA Astrophysics Data System (ADS)

Kang, Hyun-Jin; Cha, Eun Ji; Park, Hee-Deung

2015-01-01

Silane coupling agents have been widely used for immobilizing proteins onto inorganic surfaces. However, the immobilization method using silane coupling agents requires several treatment steps, and its application is limited to only surfaces containing hydroxyl groups. The aim of this study was to develop a novel method to overcome the limitations of the silane-based immobilization method using a polymer-bound isocyanate. Initially, polymer-bound isocyanate was dissolved in organic solvent and then was used to dip-coat inorganic surfaces. Proteins were then immobilized onto the dip-coated surfaces by the formation of urea bonds between the isocyanate groups of the polymer and the amine groups of the protein. The reaction was verified by FT-IR in which NCO stretching peaks disappeared, and CO and NH stretching peaks appeared after immobilization. The immobilization efficiency of the newly developed method was insensitive to reaction temperatures (4-50 °C), but the efficiency increased with reaction time and reached a maximum after 4 h. Furthermore, the method showed comparable immobilization efficiency to the silane-based immobilization method and was applicable to surfaces that cannot form hydroxyl groups. Taken together, the newly developed method provides a simple and efficient platform for immobilizing proteins onto surfaces.

The Laughlin liquid in an external potential

NASA Astrophysics Data System (ADS)

Rougerie, Nicolas; Yngvason, Jakob

2018-04-01

We study natural perturbations of the Laughlin state arising from the effects of trapping and disorder. These are N-particle wave functions that have the form of a product of Laughlin states and analytic functions of the N variables. We derive an upper bound to the ground state energy in a confining external potential, matching exactly a recently derived lower bound in the large N limit. Irrespective of the shape of the confining potential, this sharp upper bound can be achieved through a modification of the Laughlin function by suitably arranged quasi-holes.

Thermal shock induced oxidation of beryllium

NASA Astrophysics Data System (ADS)

Spilker, B.; Linke, J.; Pintsuk, G.; Wirtz, M.

2017-12-01

Beryllium has been chosen as a plasma facing material for the first wall of the experimental fusion reactor ITER, mainly because of its low atomic number and oxygen getter capabilities, which are favorable for a high plasma performance. While the steady state operational temperature of 250 °C has no deteriorating effect on the beryllium surface, transient plasma events can deposit power densities of up to 1 GW m-2 on the beryllium armor tiles. Previous research has shown that the oxidation of beryllium can occur under these thermal shock events. In the present study, S-65 grade beryllium specimens were exposed to 100 thermal shocks with an absorbed power density of 0.6 GW m-2 and a pulse duration of 1 ms, leading to a peak surface temperature of ˜800 °C. The induced surface morphology changes were compared to a steady state heated specimen at the same surface temperature with a holding time of 150 s. As a result, a pitting structure with an average pit diameter of ˜0.45 μm was observed on the thermal shock loaded surface, which was caused by beryllium oxide grain nucleation and subsequent erosion of the weakly bound beryllium oxide particles. In contrast, the steady state heated surface exhibited a more homogeneous beryllium oxide layer featuring small pits with diameters of tens of nm and showed the beryllium oxide grain nucleation in a beginning stage. The experiment demonstrated that thermal shock loading conditions can significantly accelerate the beryllium oxide grain nucleation. The resulting surface morphology change can potentially alter the fusion application relevant erosion, absorption, and retention characteristics of beryllium.

Anthrax Toxin Receptor 1 / Tumor Endothelial Marker 8: Mutation of Conserved Inserted Domain Residues Overrides Cytosolic Control of Protective Antigen Binding†

PubMed Central

Ramey, Jordan D.; Villareal, Valerie A.; Ng, Charles; Ward, Sabrina; Xiong, Jian-Ping; Clubb, Robert T.; Bradley, Kenneth A.

2010-01-01

Anthrax toxin receptor 1 (ANTXR1) / tumor endothelial marker 8 (TEM8) is one of two known proteinaceous cell surface anthrax toxin receptors. A metal ion dependent adhesion site (MIDAS) present in the integrin-like inserted (I) domain of ANTXR1 mediates the binding of the anthrax toxin subunit, protective antigen (PA). Here we provide evidence that single point mutations in the I domain can override regulation of ANTXR1 ligand-binding activity mediated by intracellular signals. A previously reported MIDAS-mutant of ANTXR1 (T118A) was found to retain normal metal ion binding and secondary structure but failed to bind PA, consistent with a locked inactive state. Conversely, mutation of a conserved I domain phenylalanine residue to a tryptophan (F205W) increased the proportion of cell-surface ANTXR1 that bound PA, consistent with a locked active state. Interestingly, the KD and total amount of PA bound by the isolated ANTXR1 I domain was not affected by the F205W mutation, indicating that ANTXR1 is preferentially found in the active state in the absence of inside-out signaling. Circular dichroism (CD) spectroscopy and 1H-15N heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) revealed that structural changes between T118A, F205W and WT I domains were minor despite a greater than 103-fold difference in their abilities to bind toxin. Regulation of toxin binding has important implications for the design of toxin inhibitors and for the targeting of ANTXR1 for anti-tumor therapies. PMID:20690680

The Role of Water Distribution Controlled by Transmembrane Potentials in the Cytochrome c-Cardiolipin Interaction: Revealing from Surface-Enhanced Infrared Absorption Spectroscopy.

PubMed

Zeng, Li; Wu, Lie; Liu, Li; Jiang, Xiue

2017-11-02

The interaction of cytochrome c (cyt c) with cardiolipin (CL) plays a crucial role in apoptotic functions, however, the changes of the transmembrane potential in governing the protein behavior at the membrane-water interface have not been studied due to the difficulties in simultaneously monitoring the interaction and regulating the electric field. Herein, surface-enhanced infrared absorption (SEIRA) spectroelectrochemistry is employed to study the mechanism of how the transmembrane potentials control the interaction of cyt c with CL membranes by regulating the electrode potentials of an Au film. When the transmembrane potential decreases, the water content at the interface of the membranes can be increased to slow down protein adsorption through decreasing the hydrogen-bond and hydrophobic interactions, but regulates the redox behavior of CL-bound cyt c through a possible water-facilitated proton-coupled electron transfer process. Our results suggest that the potential drop-induced restructure of the CL conformation and the hydration state could modify the structure and function of CL-bound cyt c on the lipid membrane. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Simulations of Membrane-Disrupting Peptides I: Alamethicin Pore Stability and Spontaneous Insertion.

PubMed

Perrin, B Scott; Pastor, Richard W

2016-09-20

An all-atom molecular dynamics simulation of the archetype barrel-stave alamethicin (alm) pore in a 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayer at 313 K indicates that ∼7 μs is required for equilibration of a preformed 6-peptide pore; the pore remains stable for the duration of the remaining 7 μs of the trajectory, and the structure factors agree well with experiment. A 5 μs simulation of 10 surface-bound alm peptides shows significant peptide unfolding and some unbinding, but no insertion. Simulations at 363 and 413 K with a -0.2 V electric field yield peptide insertion in 1 μs. Insertion is initiated by the folding of residues 3-11 into an α-helix, and mediated by membrane water or by previously inserted peptides. The stability of five alm pore peptides at 413 K with a -0.2 V electric field demonstrates a significant preference for a transmembrane orientation. Hence, and in contrast to the cationic antimicrobial peptide described in the following article, alm shows a strong preference for the inserted over the surface-bound state. Published by Elsevier Inc.

Forbidden regimes in the distribution of bipartite quantum correlations due to multiparty entanglement

NASA Astrophysics Data System (ADS)

Kumar, Asutosh; Dhar, Himadri Shekhar; Prabhu, R.; Sen(De), Aditi; Sen, Ujjwal

2017-05-01

Monogamy is a nonclassical property that limits the distribution of quantum correlation among subparts of a multiparty system. We show that monogamy scores for different quantum correlation measures are bounded above by functions of genuine multipartite entanglement for a large majority of pure multiqubit states. The bound is universal for all three-qubit pure states. We derive necessary conditions to characterize the states that violate the bound, which can also be observed by numerical simulation for a small set of states, generated Haar uniformly. The results indicate that genuine multipartite entanglement restricts the distribution of bipartite quantum correlations in a multiparty system.

The dissociative chemisorption of CO2 on Ni(100): A quantum dynamics study

NASA Astrophysics Data System (ADS)

Farjamnia, Azar; Jackson, Bret

2017-02-01

A quantum approach based on an expansion in vibrationally adiabatic eigenstates is used to explore the dissociative chemisorption of CO2 on Ni(100). The largest barrier to reaction corresponds to the formation of a bent anionic molecular precursor, bound to the surface by about 0.24 eV. The barrier to dissociation from this state is small. Our computed dissociative sticking probabilities on Ni(100) for molecules in the ground state are in very good agreement with available experimental data, reasonably reproducing the variation in reactivity with collision energy. Vibrational excitation of the incident CO2 can enhance reactivity, particularly for incident energies at or below threshold, and there is clear mode specific behavior. Both the vibrational enhancement and the increase in dissociative sticking with surface temperature are much weaker than that found in recent studies of methane and water dissociative chemisorption. The energetics for CO2 adsorption and dissociation on the stepped Ni(711) surface are found to be similar to that on Ni(100), except that the barrier to dissociation from the anionic precursor is even smaller on Ni(711). We predict that the dissociative sticking behavior is similar on the two surfaces.

The dissociative chemisorption of CO 2 on Ni(100): A quantum dynamics study

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

Farjamnia, Azar; Jackson, Bret

A quantum approach based on an expansion in vibrationally adiabatic eigenstates is used to explore the dissociative chemisorption of CO 2 on Ni(100). The largest barrier to reaction corresponds to the formation of a bent anionic molecular precursor, bound to the surface by about 0.24 eV. The barrier to dissociation from this state is small. In our computed dissociative sticking probabilities on Ni(100) for molecules, the ground states are in very good agreement with available experimental data, reasonably reproducing the variation in reactivity with collision energy. Vibrational excitation of the incident CO 2 can enhance reactivity, particularly for incident energiesmore » at or below threshold, and there is clear mode specific behavior. Both the vibrational enhancement and the increase in dissociative sticking with surface temperature are much weaker than that found in recent studies of methane and water dissociative chemisorption. The energetics for CO 2 adsorption and dissociation on the stepped Ni(711) surface are found to be similar to that on Ni(100), except that the barrier to dissociation from the anionic precursor is even smaller on Ni(711). Here, we predict that the dissociative sticking behavior is similar on the two surfaces.« less

The dissociative chemisorption of CO 2 on Ni(100): A quantum dynamics study

DOE PAGES

Farjamnia, Azar; Jackson, Bret

2017-02-21

A quantum approach based on an expansion in vibrationally adiabatic eigenstates is used to explore the dissociative chemisorption of CO 2 on Ni(100). The largest barrier to reaction corresponds to the formation of a bent anionic molecular precursor, bound to the surface by about 0.24 eV. The barrier to dissociation from this state is small. In our computed dissociative sticking probabilities on Ni(100) for molecules, the ground states are in very good agreement with available experimental data, reasonably reproducing the variation in reactivity with collision energy. Vibrational excitation of the incident CO 2 can enhance reactivity, particularly for incident energiesmore » at or below threshold, and there is clear mode specific behavior. Both the vibrational enhancement and the increase in dissociative sticking with surface temperature are much weaker than that found in recent studies of methane and water dissociative chemisorption. The energetics for CO 2 adsorption and dissociation on the stepped Ni(711) surface are found to be similar to that on Ni(100), except that the barrier to dissociation from the anionic precursor is even smaller on Ni(711). Here, we predict that the dissociative sticking behavior is similar on the two surfaces.« less

Finite-Momentum Dimer Bound State in Spin-Orbit Coupled Fermi Gas

NASA Astrophysics Data System (ADS)

Dong, Lin; Jiang, Lei; Hu, Hui; Pu, Han

2013-03-01

We investigate the two-body properties of a spin-1/2 Fermi gas subject to a spin-orbit coupling induced by laser fields. When attractive s-wave interaction between unlike spins is present, the system may form a dimer bound state. Surprisingly, under proper conditions, the bound state obtains finite center-of-mass momentum, whereas under the same condition but in the absence of the two-body interaction, the system has zero total momentum. This unusual result can be regarded as a consequence of the broken Galilean invariance by the spin-orbit coupling. Such a finite-momentum bound state will have profound effects on the many-body properties of the system. HP is supported by the NSF, the Welch Foundation (Grant No. C-1669), and DARPA. HH is supported by the ARC Discovery Projects (Grant No. DP0984522) and the National Basic Research Program of China (NFRP-China, Grant No. 2011CB921502).

Binding of the B D D ¯ and B D D systems

NASA Astrophysics Data System (ADS)

Dias, J. M.; Debastiani, V. R.; Roca, L.; Sakai, S.; Oset, E.

2017-11-01

We study theoretically the B D D ¯ and B D D systems to see if they allow for possible bound or resonant states. The three-body interaction is evaluated implementing the fixed center approximation to the Faddeev equations which considers the interaction of a D or D ¯ particle with the components of a B D cluster, previously proved to form a bound state. We find an I (JP)=1 /2 (0-) bound state for the B D D ¯ system at an energy around 8925-8985 MeV within uncertainties, which would correspond to a bottom hidden-charm meson. In contrast, for the B D D system, which would be bottom double-charm and hence manifestly exotic, we have found hints of a bound state in the energy region 8935-8985 MeV, but the results are not stable under the uncertainties of the model, and we cannot assure, nor rule out, the possibility of a B D D three-body state.

Investigation of pH response and photo-control of wettability on spiropyran-derivatized surfaces

NASA Astrophysics Data System (ADS)

Park, Choong-Do

2009-12-01

One promising method to control a liquid drop on a surface for microfluidic devices is to use the surface tension gradient on a photo-responsive surface by light irradiation. A photo-switchable spiropyran monolayer was prepared on smooth glass or silicon wafers via 3-aminopropylmethyldiethoxysilane linkages. The pH response of the surface-bound spiropyran was investigated by measuring contact angle as a function of pH, since the pH value of the liquids applied to a microfluidic system can vary widely. Based on the contact angle titration and UV-Vis spectroscopic data, a protonation and deprotonation mechanism of the surface-bound spiropyran was proposed. The advancing contact angles under UV and under visible light irradiation at high pH values were about 100 smaller than those at low pH values. The decrease in contact angle under UV light with decreasing pH value was assigned to the protonation of open merocyanine (MC) to MC-OH+. Meanwhile, the decrease in contact angle under visible light was attributed to the protonation of the closed spiropryan (SP), generating a mixed state of MC-OH+ in equilibrium with N-protonated SP-NH+. In order to examine the possibility of light-induced liquid drop motion on the spiropyran-derivatized smooth surfaces, the light-induced surface tension change between SP and MC was estimated using the contact angle hysteresis (CAH) and the Lifshitz---van der Waals/Acid-Base (LWAB) approaches based on the contact angle data. The average light-induced surface energy change between the two isomers under UV and visible light exposure was 1.4 mJ/m 2, implying that the small change in surface tension is not sufficient to move a liquid droplet on the surface. Liquid drop motion requires that the light-induced switching angle be greater than the contact angle hysteresis. However, the light-induced switching angle of the spiropyran-derivatized surface was significantly smaller than the hysteresis. Thus, in order to achieve liquid drop motion on the spiropyran-derivatized surface, a new surface design which employs a combination of chemical modification of a hydrophobic organosilane and micropatterned rough surface morphology was suggested.

Communication: Fitting potential energy surfaces with fundamental invariant neural network

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

Shao, Kejie; Chen, Jun; Zhao, Zhiqiang

A more flexible neural network (NN) method using the fundamental invariants (FIs) as the input vector is proposed in the construction of potential energy surfaces for molecular systems involving identical atoms. Mathematically, FIs finitely generate the permutation invariant polynomial (PIP) ring. In combination with NN, fundamental invariant neural network (FI-NN) can approximate any function to arbitrary accuracy. Because FI-NN minimizes the size of input permutation invariant polynomials, it can efficiently reduce the evaluation time of potential energy, in particular for polyatomic systems. In this work, we provide the FIs for all possible molecular systems up to five atoms. Potential energymore » surfaces for OH{sub 3} and CH{sub 4} were constructed with FI-NN, with the accuracy confirmed by full-dimensional quantum dynamic scattering and bound state calculations.« less

Modeling interface shear behavior of granular materials using micro-polar continuum approach

NASA Astrophysics Data System (ADS)

Ebrahimian, Babak; Noorzad, Ali; Alsaleh, Mustafa I.

2018-01-01

Recently, the authors have focused on the shear behavior of interface between granular soil body and very rough surface of moving bounding structure. For this purpose, they have used finite element method and a micro-polar elasto-plastic continuum model. They have shown that the boundary conditions assumed along the interface have strong influences on the soil behavior. While in the previous studies, only very rough bounding interfaces have been taken into account, the present investigation focuses on the rough, medium rough and relatively smooth interfaces. In this regard, plane monotonic shearing of an infinite extended narrow granular soil layer is simulated under constant vertical pressure and free dilatancy. The soil layer is located between two parallel rigid boundaries of different surface roughness values. Particular attention is paid to the effect of surface roughness of top and bottom boundaries on the shear behavior of granular soil layer. It is shown that the interaction between roughness of bounding structure surface and the rotation resistance of bounding grains can be modeled in a reasonable manner through considered Cosserat boundary conditions. The influence of surface roughness is investigated on the soil shear strength mobilized along the interface as well as on the location and evolution of shear localization formed within the layer. The obtained numerical results have been qualitatively compared with experimental observations as well as DEM simulations, and acceptable agreement is shown.

Theoretical studies of potential energy surface and rotational spectra of Xe -H2O van der Waals complex

NASA Astrophysics Data System (ADS)

Wang, Lin; Yang, Minghui

2008-11-01

In this work we report an ab initio intermolecular potential energy surface and theoretical spectroscopic studies for Xe -H2O complex. The ab initio energies are calculated with CCSD(T) method and large basis sets (aug-cc-pVQZ for H and O and aug-cc-pVQZ-PP for Xe) augmented by a {3s3p2d2f1g} set of bond functions. This potential energy surface has a global minimum corresponding to a planar and nearly linear hydrogen bonded configuration with a well depth of 192.5cm-1 at intermolecular distance of 4.0Å, which is consistent with the previous determined potential by Wen and Jäger [J. Phys. Chem. A 110, 7560 (2006)]. The bound state calculations have been performed for the complex by approximating the water molecule as a rigid rotor. The theoretical rotational transition frequencies, isotopic shifts, nuclear quadrupole coupling constants, and structure parameters are in good agreement with the experimental observed values. The wavefunctions are analyzed to understand the dynamics of the ground and the first excited states.

Localization behavior at bound Bi complex states in GaA s 1 - x B i x

DOE PAGES

Alberi, K.; Christian, T. M.; Fluegel, B.; ...

2017-07-01

While bismuth-related states are known to localize carriers in GaAs 1-xBi x alloys, the localization behavior of distinct Bi pair, triplet and cluster states bound above the valence band is less well understood. We probe localization at three different Bi complex states in dilute GaAs 1-xBi x alloys using magneto-photoluminescence and time-resolved photoluminescence spectroscopy. The mass of electrons Coulomb-bound to holes trapped at Bi pair states is found to increase relative to the average electron mass in the alloy. This increase is attributed to enhanced local compressive strain in the immediate vicinity of the pairs. The dependence of energy transfermore » between these states on composition is also explored.« less

Slow-muon study of quaternary solar-cell materials: Single layers and p -n junctions

NASA Astrophysics Data System (ADS)

Alberto, H. V.; Vilão, R. C.; Vieira, R. B. L.; Gil, J. M.; Weidinger, A.; Sousa, M. G.; Teixeira, J. P.; da Cunha, A. F.; Leitão, J. P.; Salomé, P. M. P.; Fernandes, P. A.; Törndahl, T.; Prokscha, T.; Suter, A.; Salman, Z.

2018-02-01

Thin films and p -n junctions for solar cells based on the absorber materials Cu (In ,G a ) Se2 and Cu2ZnSnS4 were investigated as a function of depth using implanted low energy muons. The most significant result is a clear decrease of the formation probability of the Mu+ state at the heterojunction interface as well as at the surface of the Cu (In ,G a ) Se2 film. This reduction is attributed to a reduced bonding reaction of the muon in the absorber defect layer at its surface. In addition, the activation energies for the conversion from a muon in an atomiclike configuration to a anion-bound position are determined from temperature-dependence measurements. It is concluded that the muon probe provides a measurement of the effective surface defect layer width, both at the heterojunctions and at the films. The CIGS surface defect layer is crucial for solar-cell electrical performance and additional information can be used for further optimizations of the surface.

Octupolar tensors for liquid crystals

NASA Astrophysics Data System (ADS)

Chen, Yannan; Qi, Liqun; Virga, Epifanio G.

2018-01-01

A third-rank three-dimensional symmetric traceless tensor, called the octupolar tensor, has been introduced to study tetrahedratic nematic phases in liquid crystals. The octupolar potential, a scalar-valued function generated on the unit sphere by that tensor, should ideally have four maxima (on the vertices of a tetrahedron), but it was recently found to possess an equally generic variant with three maxima instead of four. It was also shown that the irreducible admissible region for the octupolar tensor in a three-dimensional parameter space is bounded by a dome-shaped surface, beneath which is a separatrix surface connecting the two generic octupolar states. The latter surface, which was obtained through numerical continuation, may be physically interpreted as marking a possible intra-octupolar transition. In this paper, by using the resultant theory of algebraic geometry and the E-characteristic polynomial of spectral theory of tensors, we give a closed-form, algebraic expression for both the dome-shaped surface and the separatrix surface. This turns the envisaged intra-octupolar transition into a quantitative, possibly observable prediction.

Elastomeric nanoparticle composites covalently bound to Al2O3/GaAs surfaces.

PubMed

Song, Hyon Min; Ye, Peide D; Ivanisevic, Albena

2007-08-28

This article reports the modification of Al2O3/GaAs surfaces with multifunctional soft materials. Siloxane elastomers were covalently bound to dopamine-modified Al2O3/GaAs semiconductor surfaces using MPt (M = Fe, Ni) nanoparticles. The sizes of the monodisperse FePt and NiPt nanoparticles were less than 5 nm. The surfaces of the nanoparticles as well as the Al2O3/GaAs substrates were modified with allyl-functionalized dopamine that utilized a dihydroxy group as a strong ligand. The immobilization of the elastomers was performed via a hydrosilation reaction of the allyl-functionalized dopamines with the siloxane backbones. X-ray photoelectron spectroscopy (XPS) experiments confirmed the covalent bonding of the siloxane elastomers to the oxide layer on the semiconductor surface. Fourier transform-infrared reflection absorption spectroscopy (FT-IRRAS) measurements revealed that the allyl functional groups are bonded to the siloxane backbones. The FT-IRRAS data also showed that the density of the allyl groups on the surface was lower than that of the siloxane backbones. The mechanical properties of the surface-bound nanocomposites were tested using nanoindentation experiments. The nanoindentation data showed that the soft matrix composed of the elastomeric coating on the surfaces behaves differently from the inner, hard Al2O3/GaAs substrate.

Floquet resonant states and validity of the Floquet-Magnus expansion in the periodically driven Friedrichs models

NASA Astrophysics Data System (ADS)

Mori, Takashi

2015-02-01

The Floquet eigenvalue problem is analyzed for periodically driven Friedrichs models on discrete and continuous space. In the high-frequency regime, there exists a Floquet bound state consistent with the Floquet-Magnus expansion in the discrete Friedrichs model, while it is not the case in the continuous model. In the latter case, however, the bound state predicted by the Floquet-Magnus expansion appears as a metastable state whose lifetime diverges in the limit of large frequencies. We obtain the lifetime by evaluating the imaginary part of the quasienergy of the Floquet resonant state. In the low-frequency regime, there is no Floquet bound state and instead the Floquet resonant state with exponentially small imaginary part of the quasienergy appears, which is understood as the quantum tunneling in the energy space.

An upper bound on the second order asymptotic expansion for the quantum communication cost of state redistribution

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

Datta, Nilanjana, E-mail: n.datta@statslab.cam.ac.uk; Hsieh, Min-Hsiu, E-mail: Min-Hsiu.Hsieh@uts.edu.au; Oppenheim, Jonathan, E-mail: j.oppenheim@ucl.ac.uk

State redistribution is the protocol in which given an arbitrary tripartite quantum state, with two of the subsystems initially being with Alice and one being with Bob, the goal is for Alice to send one of her subsystems to Bob, possibly with the help of prior shared entanglement. We derive an upper bound on the second order asymptotic expansion for the quantum communication cost of achieving state redistribution with a given finite accuracy. In proving our result, we also obtain an upper bound on the quantum communication cost of this protocol in the one-shot setting, by using the protocol ofmore » coherent state merging as a primitive.« less

Spin Uncoupling in Chemisorbed OCCO and CO 2: Two High-Energy Intermediates in Catalytic CO 2 Reduction

DOE PAGES

Hedstrom, Svante; dos Santos, Egon Campos; Liu, Chang; ...

2018-05-08

Here, the production of useful compounds via the electrochemical carbon dioxide reduction reaction (CO2RR) is a matter of intense research. Although the thermodynamics and kinetic barriers of CO2RR are reported in previous computational studies, the electronic structure details are often overlooked. We study two important CO2RR intermediates: ethylenedione (OCCO) and CO 2 covalently bound to cluster and slab models of the Cu(100) surface. Both molecules exhibit a near-unity negative charge as chemisorbed, but otherwise they behave quite differently, as explained by a spin-uncoupling perspective. OCCO adopts a high-spin, quartetlike geometry, allowing two covalent bonds to the surface with an averagemore » gross interaction energy of –1.82 eV/bond. The energy cost for electronically exciting OCCO– to the quartet state is 1.5 eV which is readily repaid via the formation of its two surface bonds. CO 2, conversely, retains a low-spin, doubletlike structure upon chemisorption, and its single unpaired electron forms a single covalent surface bond of –2.07 eV. The 5.0 eV excitation energy to the CO 2 – quartet state is prohibitively costly and cannot be compensated for by an additional surface bond.« less

Validation of the SURE Program, phase 1

NASA Technical Reports Server (NTRS)

Dotson, Kelly J.

1987-01-01

Presented are the results of the first phase in the validation of the SURE (Semi-Markov Unreliability Range Evaluator) program. The SURE program gives lower and upper bounds on the death-state probabilities of a semi-Markov model. With these bounds, the reliability of a semi-Markov model of a fault-tolerant computer system can be analyzed. For the first phase in the validation, fifteen semi-Markov models were solved analytically for the exact death-state probabilities and these solutions compared to the corresponding bounds given by SURE. In every case, the SURE bounds covered the exact solution. The bounds, however, had a tendency to separate in cases where the recovery rate was slow or the fault arrival rate was fast.

Interference effects in laser-induced plasma emission from surface-bound metal micro-particles

DOE PAGES

Feigenbaum, Eyal; Malik, Omer; Rubenchik, Alexander M.; ...

2017-04-19

Here, the light-matter interaction of an optical beam and metal micro-particulates at the vicinity of an optical substrate surface is critical to the many fields of applied optics. Examples of impacted fields are laser-induced damage in high power laser systems, sub-wavelength laser machining of transmissive materials, and laser-target interaction in directed energy applications. We present a full-wave-based model that predicts the laser-induced plasma pressure exerted on a substrate surface as a result of light absorption in surface-bound micron-scale metal particles. The model predictions agree with experimental observation of laser-induced shallow pits, formed by plasma emission and etching from surface-bound metalmore » micro-particulates. It provides an explanation for the prototypical side lobes observed along the pit profile, as well as for the dependence of the pit shape on the incident laser and particle parameters. Furthermore, the model highlights the significance of the interference of the incident light in the open cavity geometry formed between the micro-particle and the substrate in the resulting pit shape.« less

Spatial aspects of prebiotic replicator coexistence and community stability in a surface-bound RNA world model

PubMed Central

2013-01-01

Background The coexistence of macromolecular replicators and thus the stability of presumed prebiotic replicator communities have been shown to critically depend on spatially constrained catalytic cooperation among RNA-like modular replicators. The necessary spatial constraints might have been supplied by mineral surfaces initially, preceding the more effective compartmentalization in membrane vesicles which must have been a later development of chemical evolution. Results Using our surface-bound RNA world model – the Metabolic Replicator Model (MRM) platform – we show that the mobilities on the mineral substrate surface of both the macromolecular replicators and the small molecules of metabolites they produce catalytically are the key factors determining the stable persistence of an evolvable metabolic replicator community. Conclusion The effects of replicator mobility and metabolite diffusion on different aspects of replicator coexistence in MRM are determined, including the maximum attainable size of the metabolic replicator system and its resistance to the invasion of parasitic replicators. We suggest a chemically plausible hypothetical scenario for the evolution of the first protocell starting from the surface-bound MRM system. PMID:24053177

Interference effects in laser-induced plasma emission from surface-bound metal micro-particles.

PubMed

Feigenbaum, Eyal; Malik, Omer; Rubenchik, Alexander M; Matthews, Manyalibo J

2017-05-01

The light-matter interaction of an optical beam and metal micro-particulates at the vicinity of an optical substrate surface is critical to the many fields of applied optics. Examples of impacted fields are laser-induced damage in high power laser systems, sub-wavelength laser machining of transmissive materials, and laser-target interaction in directed energy applications. We present a full-wave-based model that predicts the laser-induced plasma pressure exerted on a substrate surface as a result of light absorption in surface-bound micron-scale metal particles. The model predictions agree with experimental observation of laser-induced shallow pits, formed by plasma emission and etching from surface-bound metal micro-particulates. It provides an explanation for the prototypical side lobes observed along the pit profile, as well as for the dependence of the pit shape on the incident laser and particle parameters. Furthermore, the model highlights the significance of the interference of the incident light in the open cavity geometry formed between the micro-particle and the substrate in the resulting pit shape.

Clostridium perfringens Iota Toxin: Binding Studies and Characterization of Cell Surface Receptor by Fluorescence-Activated Cytometry

PubMed Central

Stiles, Bradley G.; Hale, Martha L.; Marvaud, Jean-Christophe; Popoff, Michel R.

2000-01-01

The binding characteristics of iota toxin, a binary enterotoxin produced by Clostridium perfringens type E, were studied by fluorescence-activated cytometry. The proteolytically activated binding component of iota toxin, iota b (Ib), bound to various cell types when incubated at 4, 25, or 37°C for 10 min. The binding of Ib was inhibited by antisera against C. perfringens type E or Clostridium spiroforme culture supernatants, but not C. perfringens types C or D. Pretreatment of Vero cells with glycosidases or lectins did not affect Ib interactions, while pronase effectively prevented Ib binding to the cell surface. The Ib protomer (Ibp) bound to the cell surface, but trypsinization of Ibp was necessary for docking of the ADP-ribosylating component, iota a (Ia). Ia attached to cell-bound Ib within 10 min at 37°C, but surface levels of Ia decreased 90% after 30 min and were undetectable by 60 min. Detectable surface levels of Ib also diminished over time, and Western blot analysis suggested internalization or embedment of Ib into the membrane. PMID:10816501

Clostridium perfringens iota toxin: binding studies and characterization of cell surface receptor by fluorescence-activated cytometry.

PubMed

Stiles, B G; Hale, M L; Marvaud, J C; Popoff, M R

2000-06-01

The binding characteristics of iota toxin, a binary enterotoxin produced by Clostridium perfringens type E, were studied by fluorescence-activated cytometry. The proteolytically activated binding component of iota toxin, iota b (Ib), bound to various cell types when incubated at 4, 25, or 37 degrees C for 10 min. The binding of Ib was inhibited by antisera against C. perfringens type E or Clostridium spiroforme culture supernatants, but not C. perfringens types C or D. Pretreatment of Vero cells with glycosidases or lectins did not affect Ib interactions, while pronase effectively prevented Ib binding to the cell surface. The Ib protomer (Ibp) bound to the cell surface, but trypsinization of Ibp was necessary for docking of the ADP-ribosylating component, iota a (Ia). Ia attached to cell-bound Ib within 10 min at 37 degrees C, but surface levels of Ia decreased 90% after 30 min and were undetectable by 60 min. Detectable surface levels of Ib also diminished over time, and Western blot analysis suggested internalization or embedment of Ib into the membrane.

Experimental and Computational Evidence of Highly Active Fe Impurity Sites on the Surface of Oxidized Au for the Electrocatalytic Oxidation of Water in Basic Media

DOE PAGES

Klaus, Shannon; Trotochaud, Lena; Cheng, Mu-Jeng; ...

2015-10-22

Addition of Fe to Ni- and Co-based (oxy)hydroxides has been shown to enhance the activity of these materials for electrochemical oxygen evolution. Here we show that Fe cations bound to the surface of oxidized Au exhibit enhanced oxygen evolution reaction (OER) activity. We find that the OER activity increases with increasing surface concentration of Fe. Density functional theory analysis of the OER energetics reveals that oxygen evolution over Fe cations bound to a hydroxyl-terminated oxidized Au (Fe-Au 2O 3) occurs at an overpotential ~0.3V lower than over hydroxylated Au 2O 3 (0.82V). This finding agrees well with experimental observations andmore » is a consequence of the more optimal binding energetics of OER reaction intermediates at Fe cations bound to the surface of Au 2O 3. These findings suggest that the enhanced OER activity reported recently upon low-potential cycling of Au may be due to surface Fe impurities rather than to "superactive" Au(III) surfaquo species.« less

Positrons in surface physics

NASA Astrophysics Data System (ADS)

Hugenschmidt, Christoph

2016-12-01

Within the last decade powerful methods have been developed to study surfaces using bright low-energy positron beams. These novel analysis tools exploit the unique properties of positron interaction with surfaces, which comprise the absence of exchange interaction, repulsive crystal potential and positron trapping in delocalized surface states at low energies. By applying reflection high-energy positron diffraction (RHEPD) one can benefit from the phenomenon of total reflection below a critical angle that is not present in electron surface diffraction. Therefore, RHEPD allows the determination of the atom positions of (reconstructed) surfaces with outstanding accuracy. The main advantages of positron annihilation induced Auger-electron spectroscopy (PAES) are the missing secondary electron background in the energy region of Auger-transitions and its topmost layer sensitivity for elemental analysis. In order to enable the investigation of the electron polarization at surfaces low-energy spin-polarized positrons are used to probe the outermost electrons of the surface. Furthermore, in fundamental research the preparation of well defined surfaces tailored for the production of bound leptonic systems plays an outstanding role. In this report, it is envisaged to cover both the fundamental aspects of positron surface interaction and the present status of surface studies using modern positron beam techniques.

Probing topological Fermi-Arcs and bulk boundary correspondence in the Weyl semimetal TaAs

NASA Astrophysics Data System (ADS)

Batabyal, Rajib; Morali, Noam; Avraham, Nurit; Sun, Yan; Schmidt, Marcus; Felser, Claudia; Stern, Ady; Yan, Binghai; Beidenkopf, Haim

The relation between surface Fermi-arcs and bulk Weyl cones in a Weyl semimetal, uniquely allows to study the notion of bulk to surface correspondence. We visualize these topological Fermi arc states on the surface of the Weyl semi-metal tantalum arsenide using scanning tunneling spectroscopy. Its surface hosts 12 Fermi arcs amongst several other surface bands of non-topological origin. We detect the possible scattering processes of surface bands in which Fermi arcs are involved including intra- and inter arc scatterings and arc-trivial scatterings. Each of the measured scattering processes entails additional information on the unique nature of Fermi arcs in tantalum arsenide: their contour, their energy-momentum dispersion and its relation with the bulk Weyl nodes. We further identify a sharp distinction between the wave function's spatial distribution of topological versus trivial bands. The non-topological surface bands, which are derived from the arsenic dangling bonds, are tightly bound to the arsenic termination layer. In contrast, the Fermi-arc bands reside on the deeper tantalum layer, penetrating into the bulk, which is predominantly derived from tantalum orbitals.

Magnetic states at short distances

NASA Astrophysics Data System (ADS)

Crater, Horace W.; Wong, Cheuk-Yin

2012-06-01

The magnetic interactions between a fermion and an antifermion of opposite electric or color charges in the S0-+1 and P0++3 states with J=0 are very attractive and singular near the origin and may allow the formation of new bound and resonance states at short distances. In the two-body Dirac equations formulated in constraint dynamics, the short-distance attraction for these states for point particles leads to a quasipotential that behaves near the origin as -α2/r2, where α is the coupling constant. Representing this quasipotential at short distances as λ(λ+1)/r2 with λ=(-1+1-4α2)/2, both S0-+1 and P0++3 states admit two types of eigenstates with drastically different behaviors for the radial wave function u=rψ. One type of states, with u growing as rλ+1 at small r, will be called usual states. The other type of states with u growing as r-λ will be called peculiar states. Both of the usual and peculiar eigenstates have admissible behaviors at short distances. Remarkably, the solutions for both sets of S01 states can be written out analytically. The usual bound S01 states possess attributes the same as those one usually encounters in QED and QCD, with bound QED state energies explicitly agreeing with the standard perturbative results through order α4. In contrast, the peculiar bound S01 states, yet to be observed, not only have different behaviors at the origin, but also distinctly different bound state properties (and scattering phase shifts). For the peculiar S01 ground state of fermion-antifermion pair with fermion rest mass m, the root-mean-square radius is approximately 1/m, binding energy is approximately (2-2)m, and rest mass approximately 2m. On the other hand, the (n+1)S01 peculiar state with principal quantum number (n+1) is nearly degenerate in energy and approximately equal in size with the nS01 usual states. For the P03 states, the usual solutions lead to the standard bound state energies and no resonance, but resonances have been found for the peculiar states whose energies depend on the description of the internal structure of the charges, the mass of the constituent, and the coupling constant. The existence of both usual and peculiar eigenstates in the same system leads to the non-self-adjoint property of the mass operator and two nonorthogonal complete sets. As both sets of states are physically admissible, the mass operator can be made self-adjoint with a single complete set of admissible states by introducing a new peculiarity quantum number and an enlarged Hilbert space that contains both the usual and peculiar states in different peculiarity sectors. Whether or not these newly-uncovered quantum-mechanically acceptable peculiar S01 bound states and P03 resonances for point fermion-antifermion systems correspond to physical states remains to be further investigated.

Silica-bound copper(II)triazacyclononane as a phosphate esterase: effect of linker length and surface hydrophobicity.

PubMed

Bodsgard, Brett R; Clark, Robert W; Ehrbar, Anthony W; Burstyn, Judith N

2009-04-07

A series of silica-bound Cu(ii) triazacyclononane materials was prepared to study the effect of linker length and surface hydrophobicity on the hydrolysis of phosphate esters. The general synthetic approach for these heterogeneous reagents was rhodium-catalyzed hydrosilation between an alkenyl-modified triazacyclononane and hydride-modified silica followed by metallation with a Cu(ii) salt. Elemental analysis confirmed that organic functionalization of the silica gel was successful and provided an estimate of the surface concentration of triazacyclononane. EPR spectra were consistent with square pyramidal Cu(ii), indicating that Cu(ii) ions were bound to the immobilized macrocycles. The hydrolytic efficacies of these heterogeneous reagents were tested with bis(p-nitrophenyl)phosphate (BNPP) and diethyl 4-nitrophenyl phosphate (paraoxon). The agent that performed best was an octyl-linked, propanol-blocked material. This material had the most hydrophilic surface and the most accessible active site, achieving a rate maximum on par with the other materials, but in fewer cycles and without an induction period.

Stress intensity factors in a reinforced thick-walled cylinder

NASA Technical Reports Server (NTRS)

Tang, R.; Erdogan, F.

1984-01-01

An elastic thick-walled cylinder containing a radial crack is considered. It is assumed that the cylinder is reinforced by an elastic membrane on its inner surface. The model is intended to simulate pressure vessels with cladding. The formulation of the problem is reduced to a singular integral equation. Various special cases including that of a crack terminating at the cylinder-reinforcement interface are investigated and numerical examples are given. Results indicate that in the case of the crack touching the interface the crack surface displacement derivative is finite and consequently the stress state around the corresponding crack tip is bounded; and generally, for realistic values of the stiffness parameter, the effect of the reinforcement is not very significant.

Development of an Aerosol Opacity Retrieval Algorithm for Use with Multi-Angle Land Surface Images

NASA Technical Reports Server (NTRS)

Diner, D.; Paradise, S.; Martonchik, J.

1994-01-01

In 1998, the Multi-angle Imaging SpectroRadiometer (MISR) will fly aboard the EOS-AM1 spacecraft. MISR will enable unique methods for retrieving the properties of atmospheric aerosols, by providing global imagery of the Earth at nine viewing angles in four visible and near-IR spectral bands. As part of the MISR algorithm development, theoretical methods of analyzing multi-angle, multi-spectral data are being tested using images acquired by the airborne Advanced Solid-State Array Spectroradiometer (ASAS). In this paper we derive a method to be used over land surfaces for retrieving the change in opacity between spectral bands, which can then be used in conjunction with an aerosol model to derive a bound on absolute opacity.

Orbital superconductivity, defects, and pinned nematic fluctuations in the doped iron chalcogenide FeSe 0.45 Te 0.55

DOE PAGES

Sarkar, Saheli; Van Dyke, John; Sprau, Peter O.; ...

2017-08-09

We demonstrate that the differential conductance, dI/dV , measured via spectroscopic imaging scanning tunneling microscopy in the doped iron chalcogenide FeSe0.45Te0.55, possesses a series of characteristic features that allow one to extract the orbital structure of the superconducting gaps. This yields nearly isotropic superconducting gaps on the two hole-like Fermi surfaces, and a strongly anisotropic gap on the electron-like Fermi surface. Moreover, we show that the pinning of nematic fluctuations by defects can give rise to a dumbbell-like spatial structure of the induced impurity bound states, and explains the related C 2-symmetry in the Fourier transformed differential conductance.

Orbital superconductivity, defects, and pinned nematic fluctuations in the doped iron chalcogenide FeSe 0.45 Te 0.55

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

Sarkar, Saheli; Van Dyke, John; Sprau, Peter O.

We demonstrate that the differential conductance, dI/dV , measured via spectroscopic imaging scanning tunneling microscopy in the doped iron chalcogenide FeSe0.45Te0.55, possesses a series of characteristic features that allow one to extract the orbital structure of the superconducting gaps. This yields nearly isotropic superconducting gaps on the two hole-like Fermi surfaces, and a strongly anisotropic gap on the electron-like Fermi surface. Moreover, we show that the pinning of nematic fluctuations by defects can give rise to a dumbbell-like spatial structure of the induced impurity bound states, and explains the related C 2-symmetry in the Fourier transformed differential conductance.

Spatial Charge Inhomogeneity and Defect States in Topological Dirac Semimetal Thin Films

NASA Astrophysics Data System (ADS)

Edmonds, Mark; Collins, James; Hellerstedt, Jack; Yudhistira, Indra; Rodrigues, Joao Nuno Barbosa; Gomes, Lidia Carvalho; Adam, Shaffique; Fuhrer, Michael

Dirac materials are characterized by a charge neutrality point, where the system breaks into electron/hole puddles. In graphene, substrate disorder drives fluctuations in EF, necessitating ultra-clean substrates to observe Dirac point physics. Three-dimensional topological Dirac semimetals (TDS) obviate the substrate, and should show reduced EF fluctuations due to better metallic screening and higher dielectric constants. Yet, the local response of the charge carriers in a TDS to various perturbations has yet to be explored. Here we map the potential fluctuations in TDS 20nm Na3Bi films grown via MBE using scanning tunneling microscopy/spectroscopy. The potential fluctuations are significantly smaller than room temperature (ΔEF 5 meV = 60 K) and comparable to the highest quality graphene on h-BN; far smaller than graphene on SiO2,or the Dirac surface state of a topological insulator. This observation bodes well for exploration of Dirac point physics in TDS materials. Furthermore, surface Na vacancies show a bound resonance state close to the Dirac point with large spatial extent, a possible analogue to resonant impurities in graphene.

Switching of the positive feedback for RAS activation by a concerted function of SOS membrane association domains.

PubMed

Nakamura, Yuki; Hibino, Kayo; Yanagida, Toshio; Sako, Yasushi

2016-01-01

Son of sevenless (SOS) is a guanine nucleotide exchange factor that regulates cell behavior by activating the small GTPase RAS. Recent in vitro studies have suggested that an interaction between SOS and the GTP-bound active form of RAS generates a positive feedback loop that propagates RAS activation. However, it remains unclear how the multiple domains of SOS contribute to the regulation of the feedback loop in living cells. Here, we observed single molecules of SOS in living cells to analyze the kinetics and dynamics of SOS behavior. The results indicate that the histone fold and Grb2-binding domains of SOS concertedly produce an intermediate state of SOS on the cell surface. The fraction of the intermediated state was reduced in positive feedback mutants, suggesting that the feedback loop functions during the intermediate state. Translocation of RAF, recognizing the active form of RAS, to the cell surface was almost abolished in the positive feedback mutants. Thus, the concerted functions of multiple membrane-associating domains of SOS governed the positive feedback loop, which is crucial for cell fate decision regulated by RAS.

Next-generation sequencing library construction on a surface.

PubMed

Feng, Kuan; Costa, Justin; Edwards, Jeremy S

2018-05-30

Next-generation sequencing (NGS) has revolutionized almost all fields of biology, agriculture and medicine, and is widely utilized to analyse genetic variation. Over the past decade, the NGS pipeline has been steadily improved, and the entire process is currently relatively straightforward. However, NGS instrumentation still requires upfront library preparation, which can be a laborious process, requiring significant hands-on time. Herein, we present a simple but robust approach to streamline library preparation by utilizing surface bound transposases to construct DNA libraries directly on a flowcell surface. The surface bound transposases directly fragment genomic DNA while simultaneously attaching the library molecules to the flowcell. We sequenced and analysed a Drosophila genome library generated by this surface tagmentation approach, and we showed that our surface bound library quality was comparable to the quality of the library from a commercial kit. In addition to the time and cost savings, our approach does not require PCR amplification of the library, which eliminates potential problems associated with PCR duplicates. We described the first study to construct libraries directly on a flowcell. We believe our technique could be incorporated into the existing Illumina sequencing pipeline to simplify the workflow, reduce costs, and improve data quality.

Fluoride-Mediated Capture of a Noncovalent Bound State of a Reversible Covalent Enzyme Inhibitor: X-ray Crystallographic Analysis of an Exceptionally Potent [alpha]-Ketoheterocycle Inhibitor of Fatty Acid Amide Hydrolase

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

Mileni, Mauro; Garfunkle, Joie; Ezzili, Cyrine

2011-11-02

Two cocrystal X-ray structures of the exceptionally potent {alpha}-ketoheterocycle inhibitor 1 (K{sub i} = 290 pM) bound to a humanized variant of rat fatty acid amide hydrolase (FAAH) are disclosed, representing noncovalently and covalently bound states of the same inhibitor with the enzyme. Key to securing the structure of the noncovalently bound state of the inhibitor was the inclusion of fluoride ion in the crystallization conditions that is proposed to bind the oxyanion hole precluding inhibitor covalent adduct formation with stabilization of the tetrahedral hemiketal. This permitted the opportunity to detect important noncovalent interactions stabilizing the binding of the inhibitormore » within the FAAH active site independent of the covalent reaction. Remarkably, noncovalently bound 1 in the presence of fluoride appears to capture the active site in the same 'in action' state with the three catalytic residues Ser241-Ser217-Lys142 occupying essentially identical positions observed in the covalently bound structure of 1, suggesting that this technique of introducing fluoride may have important applications in structural studies beyond inhibiting substrate or inhibitor oxyanion hole binding. Key insights to emerge from the studies include the observations that noncovalently bound 1 binds in its ketone (not gem diol) form, that the terminal phenyl group in the acyl side chain of the inhibitor serves as the key anchoring interaction overriding the intricate polar interactions in the cytosolic port, and that the role of the central activating heterocycle is dominated by its intrinsic electron-withdrawing properties. These two structures are also briefly compared with five X-ray structures of {alpha}-ketoheterocycle-based inhibitors bound to FAAH recently disclosed.« less

Quantum speed limit for arbitrary initial states

PubMed Central

Zhang, Ying-Jie; Han, Wei; Xia, Yun-Jie; Cao, Jun-Peng; Fan, Heng

2014-01-01

The minimal time a system needs to evolve from an initial state to its one orthogonal state is defined as the quantum speed limit time, which can be used to characterize the maximal speed of evolution of a quantum system. This is a fundamental question of quantum physics. We investigate the generic bound on the minimal evolution time of the open dynamical quantum system. This quantum speed limit time is applicable to both mixed and pure initial states. We then apply this result to the damped Jaynes-Cummings model and the Ohimc-like dephasing model starting from a general time-evolution state. The bound of this time-dependent state at any point in time can be found. For the damped Jaynes-Cummings model, when the system starts from the excited state, the corresponding bound first decreases and then increases in the Markovian dynamics. While in the non-Markovian regime, the speed limit time shows an interesting periodic oscillatory behavior. For the case of Ohimc-like dephasing model, this bound would be gradually trapped to a fixed value. In addition, the roles of the relativistic effects on the speed limit time for the observer in non-inertial frames are discussed. PMID:24809395

Pairing from strong repulsion in triangular lattice Hubbard model

NASA Astrophysics Data System (ADS)

Zhang, Shang-Shun; Zhu, Wei; Batista, Cristian D.

2018-04-01

We propose a pairing mechanism between holes in the dilute limit of doped frustrated Mott insulators. Hole pairing arises from a hole-hole-magnon three-body bound state. This pairing mechanism has its roots on single-hole kinetic energy frustration, which favors antiferromagnetic (AFM) correlations around the hole. We demonstrate that the AFM polaron (hole-magnon bound state) produced by a single hole propagating on a field-induced polarized background is strong enough to bind a second hole. The effective interaction between these three-body bound states is repulsive, implying that this pairing mechanism is relevant for superconductivity.

Structure and dynamics of proflavine association around DNA.

PubMed

Sasikala, Wilbee D; Mukherjee, Arnab

2016-04-21

Proflavine is a small molecule that intercalates into DNA and, thereby, acts as an anticancer agent. Intercalation of proflavine is shown to be a two-step process in which the first step is believed to be the formation of a pre-intercalative outside bound state. Experimental studies so far have been unable to capture the nature of the outside bound state. However, the sub-millisecond timescale observed in fluorescence kinetic experiments is often attributed to the binding of proflavine outside of DNA. Here, we have performed molecular dynamics simulations with multiple proflavine molecules to study the structure and dynamics of the formation of the outside bound state of DNA at different ion concentrations. We observed that the timescale of the outside bound state formation is, at least, five orders of magnitude faster (in nanoseconds) than the experimentally reported timescale (sub-milliseconds) attributed to binding outside DNA. Moreover, we also observed the stacked arrangement of proflavine all around DNA, which is different from the experimentally predicted stacking arrangement perpendicular to the helical axis of DNA in the close vicinity of the phosphate groups. This study, therefore, provides insight into the molecular structure and dynamics of the pre-intercalative outside bound state and will help in understanding the overall intercalation mechanism.

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

Topological bound states of a quantum walk with cold atoms

NASA Astrophysics Data System (ADS)

Mugel, Samuel; Celi, Alessio; Massignan, Pietro; Asbóth, János K.; Lewenstein, Maciej; Lobo, Carlos

2016-08-01

We suggest a method for engineering a quantum walk, with cold atoms as walkers, which presents topologically nontrivial properties. We derive the phase diagram, and show that we are able to produce a boundary between topologically distinct phases using the finite beam width of the applied lasers. A topologically protected bound state can then be observed, which is pinned to the interface and is robust to perturbations. We show that it is possible to identify this bound state by averaging over spin sensitive measures of the atom's position, based on the spin distribution that these states display. Interestingly, there exists a parameter regime in which our system maps on to the Creutz ladder.

Nearly Supersymmetric Dark Atoms

DOE PAGES

Behbahani, Siavosh R.; Jankowiak, Martin; Rube, Tomas; ...

2011-01-01

Theories of dark matter that support bound states are an intriguing possibility for the identity of the missing mass of the Universe. This article proposes a class of models of supersymmetric composite dark matter where the interactions with the Standard Model communicate supersymmetry breaking to the dark sector. In these models, supersymmetry breaking can be treated as a perturbation on the spectrum of bound states. Using a general formalism, the spectrum with leading supersymmetry effects is computed without specifying the details of the binding dynamics. The interactions of the composite states with the Standard Model are computed, and several benchmarkmore » models are described. General features of nonrelativistic supersymmetric bound states are emphasized.« less

Conformational phases of membrane bound cytoskeletal filaments

NASA Astrophysics Data System (ADS)

Quint, David A.; Grason, Gregory; Gopinathan, Ajay

2013-03-01

Membrane bound cytoskeletal filaments found in living cells are employed to carry out many types of activities including cellular division, rigidity and transport. When these biopolymers are bound to a membrane surface they may take on highly non-trivial conformations as compared to when they are not bound. This leads to the natural question; What are the important interactions which drive these polymers to particular conformations when they are bound to a surface? Assuming that there are binding domains along the polymer which follow a periodic helical structure set by the natural monomeric handedness, these bound conformations must arise from the interplay of the intrinsic monomeric helicity and membrane binding. To probe this question, we study a continuous model of an elastic filament with intrinsic helicity and map out the conformational phases of this filament for various mechanical and structural parameters in our model, such as elastic stiffness and intrinsic twist of the filament. Our model allows us to gain insight into the possible mechanisms which drive real biopolymers such as actin and tubulin in eukaryotes and their prokaryotic cousins MreB and FtsZ to take on their functional conformations within living cells.

Bounds on negativity for the success of quantum teleportation of qutrit-qubit system

NASA Astrophysics Data System (ADS)

K G, Paulson; Satyanarayana, S. V. M.

In the original protocol Bennet et.al., used maximally entangled pure states as quantum channel to teleport unknown states between distant observers with maximum fidelity. Noisy quantum channel can be used for imperfect teleportation. Both degree of entanglement and mixedness decide the success of teleportation in the case of mixed entangled quantum channel. . In one of our previous works, we discussed the existence of lower bound below which ,state is useless for quantum teleportation in the measure of entanglement for a fixed value of fidelity, and this lower bound decreases as rank increases for two-qubit system. We use negativity as the measure of entanglement. . In this work, we consider a qutrit-qubit system as quantum channel for teleportation, and study how the negativity and rank affect the teleportation fidelity for a class of states. We construct a new class of mixed entangled qutrit-qubit states as quantum channel, which is a convex sum of orthonormal maximally entangled and separable pure states. The classical limit of fidelity below which state is useless for quantum teleportation is fixed as 2/3. We numerically generate 30000 states and estimate the value of negativity below which each rank mixed state is useless for quantum teleportation. We also construct rank dependant boundary states by choosing appropriate eigen values, which act as upper bound for respective rank states.

Lactose binding to galectin-1 modulates structural dynamics, increases conformational entropy, and occurs with apparent negative cooperativity.

PubMed

Nesmelova, Irina V; Ermakova, Elena; Daragan, Vladimir A; Pang, Mabel; Menéndez, Margarita; Lagartera, Laura; Solís, Dolores; Baum, Linda G; Mayo, Kevin H

2010-04-16

Galectins are a family of lectins with a conserved carbohydrate recognition domain that interacts with beta-galactosides. By binding cell surface glycoconjugates, galectin-1 (gal-1) is involved in cell adhesion and migration processes and is an important regulator of tumor angiogenesis. Here, we used heteronuclear NMR spectroscopy and molecular modeling to investigate lactose binding to gal-1 and to derive solution NMR structures of gal-1 in the lactose-bound and unbound states. Structure analysis shows that the beta-strands and loops around the lactose binding site, which are more open and dynamic in the unbound state, fold in around the bound lactose molecule, dampening internal motions at that site and increasing motions elsewhere throughout the protein to contribute entropically to the binding free energy. CD data support the view of an overall more open structure in the lactose-bound state. Analysis of heteronuclear single quantum coherence titration binding data indicates that lactose binds the two carbohydrate recognition domains of the gal-1 dimer with negative cooperativity, in that the first lactose molecule binds more strongly (K(1)=21+/-6 x 10(3) M(-1)) than the second (K(2)=4+/-2 x 10(3) M(-1)). Isothermal calorimetry data fit using a sequential binding model present a similar picture, yielding K(1)=20+/-10 x 10(3) M(-1) and K(2)=1.67+/-0.07 x 10(3) M(-1). Molecular dynamics simulations provide insight into structural dynamics of the half-loaded lactose state and, together with NMR data, suggest that lactose binding at one site transmits a signal through the beta-sandwich and loops to the second binding site. Overall, our results provide new insight into gal-1 structure-function relationships and to protein-carbohydrate interactions in general. Copyright (c) 2010. Published by Elsevier Ltd.

A Monomeric Membrane Peptide that Lives in Three Worlds: In Solution, Attached to, and Inserted across Lipid Bilayers

PubMed Central

Reshetnyak, Yana K.; Segala, Michael; Andreev, Oleg A.; Engelman, Donald M.

2007-01-01

The membrane peptide pH (low) insertion peptide (pHLIP) lives in three worlds, being soluble in aqueous solution at pH 7.4, binding to the surface of lipid bilayers, and inserting as a transbilayer helix at low pH. With low pH driving the process, pHLIP can translocate cargo molecules attached to its C-terminus via a disulfide and release them in the cytoplasm of a cell. Here we examine a key aspect of the mechanism, showing that pHLIP is monomeric in each of its three major states: soluble in water near neutral pH (state I), bound to the surface of a membrane near neutral pH (state II), and inserted across the membrane as an α-helix at low pH (state III). The peptide does not induce fusion or membrane leakage. The unique properties of pHLIP made it attractive for the biophysical investigation of membrane protein folding in vitro and for the development of a novel class of delivery peptides for the transport of therapeutic and diagnostic agents to acidic tissue sites associated with various pathological processes in vivo. PMID:17557792

Semistable extremal ground states for nonlinear evolution equations in unbounded domains

NASA Astrophysics Data System (ADS)

Rodríguez-Bernal, Aníbal; Vidal-López, Alejandro

2008-02-01

In this paper we show that dissipative reaction-diffusion equations in unbounded domains posses extremal semistable ground states equilibria, which bound asymptotically the global dynamics. Uniqueness of such positive ground state and their approximation by extremal equilibria in bounded domains is also studied. The results are then applied to the important case of logistic equations.

Contemporary continuum QCD approaches to excited hadrons

NASA Astrophysics Data System (ADS)

El-Bennich, Bruno; Rojas, Eduardo

2016-03-01

Amongst the bound states produced by the strong interaction, radially excited meson and nucleon states offer an important phenomenological window into the long-range behavior of the coupling constant in Quantum Chromodynamics. We here report on some technical details related to the computation of the bound state's eigenvalue spectrum in the framework of Bethe-Salpeter and Faddeev equations.

Proton NMR studies of functionalized nanoparticles in aqueous environments

NASA Astrophysics Data System (ADS)

Tataurova, Yulia Nikolaevna

Nanoscience is an emerging field that can provide potential routes towards addressing critical issues such as clean and sustainable energy, environmental remediation and human health. Specifically, porous nanomaterials, such as zeolites and mesoporous silica, are found in a wide range of applications including catalysis, drug delivery, imaging, environmental protection, and sensing. The characterization of the physical and chemical properties of nanocrystalline materials is essential to the realization of these innovative applications. The great advantage of porous nanocrystals is their increased external surface area that can control their biological, chemical and catalytic activities. Specific functional groups synthesized on the surface of nanoparticles are able to absorb heavy metals from the solution or target disease cells, such as cancer cells. In these studies, three main issues related to functionalized nanomaterials will be addressed through the application of nuclear magnetic resonance (NMR) techniques including: 1) surface composition and structure of functionalized nanocrystalline particles; 2) chemical properties of the guest molecules on the surface of nanomaterials, and 3) adsorption and reactivity of surface bound functional groups. Nuclear magnetic resonance (NMR) is one of the major spectroscopic techniques available for the characterization of molecular structure and conformational dynamics with atomic level detail. This thesis deals with the application of 1H solution state NMR to porous nanomaterial in an aqueous environment. Understanding the aqueous phase behavior of functionalized nanomaterials is a key factor in the design and development of safe nanomaterials because their interactions with living systems are always mediated through the aqueous phase. This is often due to a lack of fundamental knowledge in interfacial chemical and physical phenomena that occur on the surface of nanoparticles. The use of solution NMR spectroscopy results in high-resolution NMR spectra. This technique is selective for protons on the surface organic functional groups due to their motional averaging in solution. In this study, 1H solution NMR spectroscopy was used to investigate the interface of the organic functional groups in D2O. The pKa for these functional groups covalently bound to the surface of nanoparticles was determined using an NMR-pH titration method based on the variation in the proton chemical shift for the alkyl group protons closest to the amine group with pH. The adsorption of toxic contaminants (chromate and arsenate anions) on the surface of functionalized silicalite-1 and mesoporous silica nanoparticles has been studied by 1H solution NMR spectroscopy. With this method, the surface bound contaminants are detected. The analysis of the intensity and position of these peaks allows quantitative assessment of the relative amounts of functional groups with adsorbed metal ions. These results demonstrate the sensitivity of solution NMR spectroscopy to the electronic environment and structure of the surface functional groups on porous nanomaterials.

Obtaining a W state from a Greenberger-Horne-Zeilinger state via stochastic local operations and classical communication with a rate approaching unity.

PubMed

Yu, Nengkun; Guo, Cheng; Duan, Runyao

2014-04-25

We introduce a notion of the entanglement transformation rate to characterize the asymptotic comparability of two multipartite pure entangled states under stochastic local operations and classical communication (SLOCC). For two well known SLOCC inequivalent three-qubit states |GHZ⟩=(1/2)(|000⟩+|111⟩) and |W⟩=(1/3)(|100⟩+|010⟩+|001⟩), we show that the entanglement transformation rate from |GHZ⟩ to |W⟩ is exactly 1. That means that we can obtain one copy of the W state from one copy of the Greenberg-Horne-Zeilinger (GHZ) state by SLOCC, asymptotically. We then apply similar techniques to obtain a lower bound on the entanglement transformation rates from an N-partite GHZ state to a class of Dicke states, and prove the tightness of this bound for some special cases which naturally generalize the |W⟩ state. A new lower bound on the tensor rank of the matrix permanent is also obtained by evaluating the tensor rank of Dicke states.

Theoretical derivation of laser-dressed atomic states by using a fractal space

NASA Astrophysics Data System (ADS)

Duchateau, Guillaume

2018-05-01

The derivation of approximate wave functions for an electron submitted to both a Coulomb and a time-dependent laser electric fields, the so-called Coulomb-Volkov (CV) state, is addressed. Despite its derivation for continuum states does not exhibit any particular problem within the framework of the standard theory of quantum mechanics (QM), difficulties arise when considering an initially bound atomic state. Indeed the natural way of translating the unperturbed momentum by the laser vector potential is no longer possible since a bound state does not exhibit a plane wave form explicitly including a momentum. The use of a fractal space permits to naturally define a momentum for a bound wave function. Within this framework, it is shown how the derivation of laser-dressed bound states can be performed. Based on a generalized eikonal approach, a new expression for the laser-dressed states is also derived, fully symmetric relative to the continuum or bound nature of the initial unperturbed wave function. It includes an additional crossed term in the Volkov phase which was not obtained within the standard theory of quantum mechanics. The derivations within this fractal framework have highlighted other possible ways to derive approximate laser-dressed states in QM. After comparing the various obtained wave functions, an application to the prediction of the ionization probability of hydrogen targets by attosecond XUV pulses within the sudden approximation is provided. This approach allows to make predictions in various regimes depending on the laser intensity, going from the non-resonant multiphoton absorption to tunneling and barrier-suppression ionization.

Reduction of adsorbed As(V) on nano-TiO2 by sulfate-reducing bacteria.

PubMed

Luo, Ting; Ye, Li; Ding, Cheng; Yan, Jinlong; Jing, Chuanyong

2017-11-15

Reduction of surface-bound arsenate [As(V)] and subsequent release into the aqueous phase contribute to elevated As in groundwater. However, this natural process is not fully understood, especially in the presence of sulfate-reducing bacteria (SRB). Gaining mechanistic insights into solid-As(V)-SRB interactions motivated our molecular level study on the fate of nano-TiO 2 bound As(V) in the presence of Desulfovibrio vulgaris DP4, a strain of SRB, using incubation and in situ ATR-FTIR experiments. The incubation results clearly revealed the reduction of As(V), either adsorbed on nano-TiO 2 or dissolved, in the presence of SRB. In contrast, this As(V) reduction was not observed in abiotic control experiments where sulfide was used as the reductant. Moreover, the reduction was faster for surface-bound As(V) than for dissolved As(V), as evidenced by the appearance of As(III) at 45h and 75h, respectively. ATR-FTIR results provided direct evidence that the surface-bound As(V) was reduced to As(III) on TiO 2 surfaces in the presence of SRB. In addition, the As(V) desorption from nano-TiO 2 was promoted by SRB relative to abiotic sulfide, due to the competition between As(V) and bacterial phosphate groups for TiO 2 surface sites. This competition was corroborated by the ATR-FTIR analysis, which showed inner-sphere surface complex formation by bacterial phosphate groups on TiO 2 surfaces. The results from this study highlight the importance of indirect bacteria-mediated As(V) reduction and release in geochemical systems. Copyright © 2017 Elsevier B.V. All rights reserved.

The Kinesin-5 Chemomechanical Cycle Is Dominated by a Two-heads-bound State*♦

PubMed Central

Mickolajczyk, Keith J.

2016-01-01

Single-molecule microscopy and stopped-flow kinetics assays were carried out to understand the microtubule polymerase activity of kinesin-5 (Eg5). Four lines of evidence argue that the motor primarily resides in a two-heads-bound (2HB) state. First, upon microtubule binding, dimeric Eg5 releases both bound ADPs. Second, microtubule dissociation in saturating ADP is 20-fold slower for the dimer than for the monomer. Third, ATP-triggered mant-ADP release is 5-fold faster than the stepping rate. Fourth, ATP binding is relatively fast when the motor is locked in a 2HB state. Shortening the neck-linker does not facilitate rear-head detachment, suggesting a minimal role for rear-head-gating. This 2HB state may enable Eg5 to stabilize incoming tubulin at the growing microtubule plus-end. The finding that slowly hydrolyzable ATP analogs trigger slower nucleotide release than ATP suggests that ATP hydrolysis in the bound head precedes stepping by the tethered head, leading to a mechanochemical cycle in which processivity is determined by the race between unbinding of the bound head and attachment of the tethered head. PMID:27402829

Volume dependence of N-body bound states

NASA Astrophysics Data System (ADS)

König, Sebastian; Lee, Dean

2018-04-01

We derive the finite-volume correction to the binding energy of an N-particle quantum bound state in a cubic periodic volume. Our results are applicable to bound states with arbitrary composition and total angular momentum, and in any number of spatial dimensions. The only assumptions are that the interactions have finite range. The finite-volume correction is a sum of contributions from all possible breakup channels. In the case where the separation is into two bound clusters, our result gives the leading volume dependence up to exponentially small corrections. If the separation is into three or more clusters, there is a power-law factor that is beyond the scope of this work, however our result again determines the leading exponential dependence. We also present two independent methods that use finite-volume data to determine asymptotic normalization coefficients. The coefficients are useful to determine low-energy capture reactions into weakly bound states relevant for nuclear astrophysics. Using the techniques introduced here, one can even extract the infinite-volume energy limit using data from a single-volume calculation. The derived relations are tested using several exactly solvable systems and numerical examples. We anticipate immediate applications to lattice calculations of hadronic, nuclear, and cold atomic systems.

Lower bounds on the violation of the monogamy inequality for quantum correlation measures

NASA Astrophysics Data System (ADS)

Kumar, Asutosh; Dhar, Himadri Shekhar

2016-06-01

In multiparty quantum systems, the monogamy inequality proposes an upper bound on the distribution of bipartite quantum correlation between a single party and each of the remaining parties in the system, in terms of the amount of quantum correlation shared by that party with the rest of the system taken as a whole. However, it is well known that not all quantum correlation measures universally satisfy the monogamy inequality. In this work, we aim at determining the nontrivial value by which the monogamy inequality can be violated by a quantum correlation measure. Using an information-theoretic complementarity relation between the normalized purity and quantum correlation in any given multiparty state, we obtain a nontrivial lower bound on the negative monogamy score for the quantum correlation measure. In particular, for the three-qubit states the lower bound is equal to the negative von Neumann entropy of the single qubit reduced density matrix. We analytically examine the tightness of the derived lower bound for certain n -qubit quantum states. Further, we report numerical results of the same for monogamy violating correlation measures using Haar uniformly generated three-qubit states.

Synthesis of surface bound silver nanoparticles on cellulose fibers using lignin as multi-functional agent.

PubMed

Hu, Sixiao; Hsieh, You-Lo

2015-10-20

Lignin has proven to be highly effective "green" multi-functional binding, complexing and reducing agents for silver cations as well as capping agents for the synthesis of silver nanoparticles on ultra-fine cellulose fibrous membranes. Silver nanoparticles could be synthesized in 10min to be densely distributed and stably bound on the cellulose fiber surfaces at up to 2.9% in mass. Silver nanoparticle increased in sizes from 5 to 100nm and became more polydispersed in size distribution on larger fibers and with longer synthesis time. These cellulose fiber bound silver nanoparticles did not agglomerate under elevated temperatures and showed improved thermal stability. The presence of alkali lignin conferred moderate UV absorbing ability in both UV-B and UV-C regions whereas the bound silver nanoparticles exhibited excellent antibacterial activities toward Escherichia coli. Copyright © 2015 Elsevier Ltd. All rights reserved.

Cost analysis of measles in refugees arriving at Los Angeles International Airport from Malaysia

PubMed Central

Coleman, Margaret S.; Burke, Heather M.; Welstead, Bethany L.; Mitchell, Tarissa; Taylor, Eboni M.; Shapovalov, Dmitry; Maskery, Brian A.; Joo, Heesoo; Weinberg, Michelle

2017-01-01

ABSTRACT Background On August 24, 2011, 31 US-bound refugees from Kuala Lumpur, Malaysia (KL) arrived in Los Angeles. One of them was diagnosed with measles post-arrival. He exposed others during a flight, and persons in the community while disembarking and seeking medical care. As a result, 9 cases of measles were identified. Methods We estimated costs of response to this outbreak and conducted a comparative cost analysis examining what might have happened had all US-bound refugees been vaccinated before leaving Malaysia. Results State-by-state costs differed and variously included vaccination, hospitalization, medical visits, and contact tracing with costs ranging from $621 to $35,115. The total of domestic and IOM Malaysia reported costs for US-bound refugees were $137,505 [range: $134,531 - $142,777 from a sensitivity analysis]. Had all US-bound refugees been vaccinated while in Malaysia, it would have cost approximately $19,646 and could have prevented 8 measles cases. Conclusion A vaccination program for US-bound refugees, supporting a complete vaccination for US-bound refugees, could improve refugees' health, reduce importations of vaccine-preventable diseases in the United States, and avert measles response activities and costs. PMID:28068211

Cost analysis of measles in refugees arriving at Los Angeles International Airport from Malaysia.

PubMed

Coleman, Margaret S; Burke, Heather M; Welstead, Bethany L; Mitchell, Tarissa; Taylor, Eboni M; Shapovalov, Dmitry; Maskery, Brian A; Joo, Heesoo; Weinberg, Michelle

2017-05-04

Background On August 24, 2011, 31 US-bound refugees from Kuala Lumpur, Malaysia (KL) arrived in Los Angeles. One of them was diagnosed with measles post-arrival. He exposed others during a flight, and persons in the community while disembarking and seeking medical care. As a result, 9 cases of measles were identified. Methods We estimated costs of response to this outbreak and conducted a comparative cost analysis examining what might have happened had all US-bound refugees been vaccinated before leaving Malaysia. Results State-by-state costs differed and variously included vaccination, hospitalization, medical visits, and contact tracing with costs ranging from $621 to $35,115. The total of domestic and IOM Malaysia reported costs for US-bound refugees were $137,505 [range: $134,531 - $142,777 from a sensitivity analysis]. Had all US-bound refugees been vaccinated while in Malaysia, it would have cost approximately $19,646 and could have prevented 8 measles cases. Conclusion A vaccination program for US-bound refugees, supporting a complete vaccination for US-bound refugees, could improve refugees' health, reduce importations of vaccine-preventable diseases in the United States, and avert measles response activities and costs.

Nucleotide Dependent Switching in Rho GTPase: Conformational Heterogeneity and Competing Molecular Interactions

PubMed Central

Kumawat, Amit; Chakrabarty, Suman; Kulkarni, Kiran

2017-01-01

Ras superfamily of GTPases regulate myriad cellular processes through a conserved nucleotide (GTP/GDP) dependent switching mechanism. Unlike Ras family of GTPases, for the Rho GTPases, there is no clear evidence for the existence of “sub-states” such as state 1 & state 2 in the GTP bound form. To explore the nucleotide dependent conformational space of the Switch I loop and also to look for existence of state 1 like conformations in Rho GTPases, atomistic molecular dynamics and metadynamics simulations on RhoA were performed. These studies demonstrate that both the nucleotide-free state and the GDP bound “OFF” state have very similar conformations, whereas the GTP bound “ON” state has unique conformations with signatures of two intermediate states. The conformational free energy landscape for these systems suggests the presence of multiple intermediate states. Interestingly, the energetic penalty of exposing the non-polar residues in the GTP bound form is counter balanced by the favourable hydrogen bonded interactions between the γ-phosphate group of GTP with the highly conserved Tyr34 and Thr37 residues. These competing molecular interactions lead to a tuneable energy landscape of the Switch I conformation, which can undergo significant changes based on the local environment including changes upon binding to effectors. PMID:28374773

Nucleotide Dependent Switching in Rho GTPase: Conformational Heterogeneity and Competing Molecular Interactions

NASA Astrophysics Data System (ADS)

Kumawat, Amit; Chakrabarty, Suman; Kulkarni, Kiran

2017-04-01

Ras superfamily of GTPases regulate myriad cellular processes through a conserved nucleotide (GTP/GDP) dependent switching mechanism. Unlike Ras family of GTPases, for the Rho GTPases, there is no clear evidence for the existence of “sub-states” such as state 1 & state 2 in the GTP bound form. To explore the nucleotide dependent conformational space of the Switch I loop and also to look for existence of state 1 like conformations in Rho GTPases, atomistic molecular dynamics and metadynamics simulations on RhoA were performed. These studies demonstrate that both the nucleotide-free state and the GDP bound “OFF” state have very similar conformations, whereas the GTP bound “ON” state has unique conformations with signatures of two intermediate states. The conformational free energy landscape for these systems suggests the presence of multiple intermediate states. Interestingly, the energetic penalty of exposing the non-polar residues in the GTP bound form is counter balanced by the favourable hydrogen bonded interactions between the γ-phosphate group of GTP with the highly conserved Tyr34 and Thr37 residues. These competing molecular interactions lead to a tuneable energy landscape of the Switch I conformation, which can undergo significant changes based on the local environment including changes upon binding to effectors.

Comment on “Propagation of surface waves on a semi-bounded quantum magnetized collisional plasma” [Phys. Plasmas 20, 122106 (2013)

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

Moradi, Afshin, E-mail: a.moradi@kut.ac.ir

2016-04-15

In a recent article [Niknam et al., Phys. Plasmas 20, 122106 (2013)], Niknam et al. investigated the propagation of TM surface waves on a semi-bounded quantum magnetized collisional plasma in the Faraday configuration (in this case, the magnetic field is parallel to the both of the plasma surface and direction of propagation). Here, we present a fresh look at the problem and show that TM surface waves cannot propagate on surface of the present system. We find in the Faraday configuration the surface waves acquire both TM and TE components due to the cyclotron motion of electrons. Therefore, the mainmore » result of the work by Niknam et al. is incorrect.« less

Universal bounds on the time evolution of entanglement entropy.

PubMed

Avery, Steven G; Paulos, Miguel F

2014-12-05

Using relative entropy, we derive bounds on the time rate of change of geometric entanglement entropy for any relativistic quantum field theory in any dimension. The bounds apply to both mixed and pure states, and may be extended to curved space. We illustrate the bounds in a few examples and comment on potential applications and future extensions.

Capture and decay of electroweak WIMPonium

NASA Astrophysics Data System (ADS)

Asadi, Pouya; Baumgart, Matthew; Fitzpatrick, Patrick J.; Krupczak, Emmett; Slatyer, Tracy R.

2017-02-01

The spectrum of Weakly-Interacting-Massive-Particle (WIMP) dark matter generically possesses bound states when the WIMP mass becomes sufficiently large relative to the mass of the electroweak gauge bosons. The presence of these bound states enhances the annihilation rate via resonances in the Sommerfeld enhancement, but they can also be produced directly with the emission of a low-energy photon. In this work we compute the rate for SU(2) triplet dark matter (the wino) to bind into WIMPonium—which is possible via single-photon emission for wino masses above 5 TeV for relative velocity v < O(10-2) —and study the subsequent decays of these bound states. We present results with applications beyond the wino case, e.g. for dark matter inhabiting a nonabelian dark sector; these include analytic capture and transition rates for general dark sectors in the limit of vanishing force carrier mass, efficient numerical routines for calculating positive and negative-energy eigenstates of a Hamiltonian containing interactions with both massive and massless force carriers, and a study of the scaling of bound state formation in the short-range Hulth&apos{e}n potential. In the specific case of the wino, we find that the rate for bound state formation is suppressed relative to direct annihilation, and so provides only a small correction to the overall annihilation rate. The soft photons radiated by the capture process and by bound state transitions could permit measurement of the dark matter's quantum numbers; for wino-like dark matter, such photons are rare, but might be observable by a future ground-based gamma-ray telescope combining large effective area and a low energy threshold.

Cytochrome c at charged interfaces studied by resonance Raman and surface-enhanced resonance Raman spectroscopy

NASA Astrophysics Data System (ADS)

Hildebrandt, Peter

1991-05-01

The effect of electrostatic fields on the structure of cytochrome c bound to charged interfaces was studied by resonance Raman and surface enhanced resonance Raman spectroscopy. Binding of this heme protein to the Ag electrode or heteropolytungstates which may be regarded as simple model systems for biological interfaces establishes an equilibrium between two conformational states (I II). In state I the structure and the redox potential are the same as for the uncomplexed cytochrome c. In state II however the heme pocket assumes an open structure and the axial iron Met80 bond is weakened leading to thennal coordination equilibrium between the fivecoordinated high spin and the sixcoordinated low spin configuration. These structural changes are accompanied by a decrease of the redox potential by 420 mV. The structural rearrangement of the heme pocket in state II is presumably initiated by the dissociation of the internal salt bridge of Lys13 due to electrostatic interactions with the negatively charged surfaces of the model systems. From detailed Raman spectroscopic studies characteristic spectral properties of the states I and II were identified. Based on these findings the interactions of cytochrome c with phospholipid vesicles as well as with its physiological reaction partner cytocbrome c oxidase were analysed. A systematic study of the cytochmme c/phospholipid system by varying the lipid composition and the temperature revealed mutual structural changes in both the lipid and the protein structure.

Capillary Phenomena: Investigations in Compressed Bubble Migration, Geometric Wetting, and Blade-Bound Droplet Stability

NASA Astrophysics Data System (ADS)

Blackmore, William Henry

Capillary flows continue to be important in numerous spacecraft systems where the effective magnitude of the gravity vector is approximately one millionth that of normal Earth gravity. Due to the free fall state of orbiting spacecraft, the effects of capillarity on the fluid systems onboard can dominate the fluid behavior over large length scales. In this research three investigations are pursued where the unique interplay between surface tension forces, wetting characteristics, and system geometry control the fluid behavior, whether in large systems aboard spacecraft, or micro-scale systems on Earth. First, efforts in support of two International Space Station (ISS) experiments are reported. A description of the development of a new NASA ground station at Portland State University is provided along with descriptions of astronaut training activities for the proper operation of four handheld experiments currently in orbit as part of the second iteration of the Capillary Flow Experiments (CFE-2). Concerning the latter, seven more vessels are expected to be launched to the ISS shortly. Analysis of the data alongside numerical simulations shows excellent agreement with theory, and a new intuitive method of viewing critical wetting angles and fluid bulk shift phenomena is offered. Secondly, during the CFE-2 space experiments, unplanned peripheral observations revealed that, on occasion, rapidly compressed air bubbles migrate along paths with vector components common to the residual acceleration onboard the ISS. Unexpectedly however, the migration velocities could be shown to be up to three orders of magnitude greater than the appropriate Stokes flow limit! Likely mechanisms are explored analytically and experimentally while citing prior theoretical works that may have anticipated such phenomena. Once properly understood, compressed bubble migration may be used as an elegant method for phase separation in spacecraft systems or microgravity-based materials manufacturing. Lastly, the stability of drops on surfaces is important in a variety of natural and industrial processes. So called 'wall-edge-vertex bound drops' (a.k.a. drops on blade tips or drops on leaf tips which they resemble) are explored using a numerical approach which applies the Surface Evolver algorithm through implementation of a new file layer and a multi-parameter sweep function. As part of a recently open sourced SE-FIT software, thousands of critical drop configurations are efficiently computed as functions of contact angle, blade edge vertex half-angle, and g-orientation. With the support of other graduate students, simple experiments are performed to benchmark the computations which are then correlated for ease of application. It is shown that sessile, pendant, and wall-edge bound drops are only limiting cases of the more generalized blade-bound drops, and that a ubiquitous 'dry leaf tip' is observed for a range of the critical geometric and wetting parameters.

Effect of Parainfluenza-3 Neuraminidase on Bovine Nasal Secretion

PubMed Central

Morein, Bror; Bergman, Rune

1972-01-01

Three samples of bovine nasal secretion were each separated into a sol phase and a surface gel phase. In all samples, the gel phase contained an approximately four times greater amount of bound N-acetylneuraminic acid (NANA) than the sol phase. From the gel phase, bound NANA could be released by exposure to parainfluenza-3 virus neuraminidase. The surface gel appears to be a natural substrate for this enzyme. PMID:4347547

Comparison of a preQ1 riboswitch aptamer in metabolite-bound and free states with implications for gene regulation.

PubMed

Jenkins, Jermaine L; Krucinska, Jolanta; McCarty, Reid M; Bandarian, Vahe; Wedekind, Joseph E

2011-07-15

Riboswitches are RNA regulatory elements that govern gene expression by recognition of small molecule ligands via a high affinity aptamer domain. Molecular recognition can lead to active or attenuated gene expression states by controlling accessibility to mRNA signals necessary for transcription or translation. Key areas of inquiry focus on how an aptamer attains specificity for its effector, the extent to which the aptamer folds prior to encountering its ligand, and how ligand binding alters expression signal accessibility. Here we present crystal structures of the preQ(1) riboswitch from Thermoanaerobacter tengcongensis in the preQ(1)-bound and free states. Although the mode of preQ(1) recognition is similar to that observed for preQ(0), surface plasmon resonance revealed an apparent K(D) of 2.1 ± 0.3 nm for preQ(1) but a value of 35.1 ± 6.1 nm for preQ(0). This difference can be accounted for by interactions between the preQ(1) methylamine and base G5 of the aptamer. To explore conformational states in the absence of metabolite, the free-state aptamer structure was determined. A14 from the ceiling of the ligand pocket shifts into the preQ(1)-binding site, resulting in "closed" access to the metabolite while simultaneously increasing exposure of the ribosome-binding site. Solution scattering data suggest that the free-state aptamer is compact, but the "closed" free-state crystal structure is inadequate to describe the solution scattering data. These observations are distinct from transcriptional preQ(1) riboswitches of the same class that exhibit strictly ligand-dependent folding. Implications for gene regulation are discussed.

Anomalous X-Ray Reflectivity Characterization of Ion Distribution at Biomimetic Membranes

NASA Astrophysics Data System (ADS)

Vaknin, David; Krüger, Peter; Lösche, Mathias

2003-05-01

Anomalous x-ray reflectivity measurements provides detailed information on ion binding to biomembrane surfaces. Using a monochromatic beam tuned to various x-ray energies at the Argonne National Laboratory Advanced Photon Source and utilizing a newly commissioned x-ray liquid surfaces reflectometer, measurements at and away from ion absorption edges allow determination of the distribution of these ions as they accumulate near lipid membranes. As a model, the interaction of Ba2+ ions with DMPA- (1,2-dimyristoyl-sn-glycero-3-phosphatidic acid) monolayers at the aqueous surface is studied. We find an unexpectedly large concentration of barium at the interface, ≈1.5 per DMPA-, forming a Stern layer of bound ions and a cloud of less densely bound ions near the lipid headgroups. This result can be understood only if one assumes that bound cations are partially speciated, e.g., as BaOH+.

Aeroacoustic Duster

NASA Technical Reports Server (NTRS)

Marshall, Jeffrey S. (Inventor); Chen, Di (Inventor); Vachon, Nicholas Mario (Inventor); Hitt, Darren (Inventor); Wu, Junru (Inventor)

2014-01-01

The aero-acoustic duster invention disclosed herein provides for high particle removal rate from surfaces with low energy expenditure relative to competing vacuum-based devices. The device removes particulate matter from a surface using a two-step process: 1. Acoustic radiation is used to break the adhesive bonds between dust and the surface, forcing particles into a mode where they continuously bounce up and down on the surface; and, 2. A bounded vortex is generated over the surface, with suction in the vortex center and jets for blowing air along the periphery. The jets are tilted in the tangential direction to induce vortex motion within the suction region. The vortex is said to be bounded because streamlines originating in the downward jets are entrained back into the central vortex.

A generalization of Bertrand's theorem to surfaces of revolution

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

Zagryadskii, Oleg A; Kudryavtseva, Elena A; Fedoseev, Denis A

We prove a generalization of Bertrand's theorem to the case of abstract surfaces of revolution that have no 'equators'. We prove a criterion for exactly two central potentials to exist on this type of surface (up to an additive and a multiplicative constant) for which all bounded orbits are closed and there is a bounded nonsingular noncircular orbit. We prove a criterion for the existence of exactly one such potential. We study the geometry and classification of the corresponding surfaces with the aforementioned pair of potentials (gravitational and oscillatory) or unique potential (oscillatory). We show that potentials of the requiredmore » form do not exist on surfaces that do not belong to any of the classes described. Bibliography: 33 titles.« less

Determination of the magnetic contribution to the heat capacity of cobalt oxide nanoparticles and the thermodynamic properties of the hydration layers

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

Spencer, Elinor; Ross, Dr. Nancy; Parker, Stewart F.

2011-01-01

We present low temperature (11 K) inelastic neutron scattering (INS) data on four hydrated nanoparticle systems: 10 nm CoO 0.10H2O (1), 16 nmCo3O4 0.40H2O (2), 25 nm Co3O4 0.30H2O (3) and 40 nmCo3O4 0.026H2O (4). The vibrational densities of states were obtained for all samples and from these the isochoric heat capacity and vibrational energy for the hydration layers confined to the surfaces of these nanoparticle systems have been elucidated. The results show that water on the surface of CoO nanoparticles is more tightly bound than water confined to the surface of Co3O4, and this is reflected in the reducedmore » heat capacity and vibrational entropy for water on CoO relative to water on Co3O4 nanoparticles. This supports the trend, seen previously, for water to be more tightly bound in materials with higher surface energies. The INS spectra for the antiferromagnetic Co3O4 particles (2 4) also show sharp and intense magnetic excitation peaks at 5 meV, and from this the magnetic contribution to the heat capacity of Co3O4 nanoparticles has been calculated; this represents the first example of use of INS data for determining the magnetic contribution to the heat capacity of any magnetic nanoparticle system.« less

Coherent control of the formation of cold heteronuclear molecules by photoassociation

NASA Astrophysics Data System (ADS)

de Lima, Emanuel F.

2017-01-01

We consider the formation of cold diatomic molecules in the electronic ground state by photoassociation of atoms of dissimilar species. A combination of two transition pathways from the free colliding pair of atoms to a bound vibrational level of the electronic molecular ground state is envisioned. The first pathway consists of a pump-dump scheme with two time-delayed laser pulses in the near-infrared frequency domain. The pump pulse drives the transition to a bound vibrational level of an excited electronic state, while the dump pulse transfers the population to a bound vibrational level of the electronic ground state. The second pathway takes advantage of the existing permanent dipole moment and employs a single pulse in the far-infrared domain to drive the transition from the unbound atoms directly to a bound vibrational level in the electronic ground state. We show that this scheme offers the possibility to coherently control the photoassociation yield by manipulating the relative phase and timing of the pulses. The photoassociation mechanism is illustrated for the formation of cold LiCs molecules.

Channel branching ratios in CH2CN- photodetachment: Rotational structure and vibrational energy redistribution in autodetachment

NASA Astrophysics Data System (ADS)

Lyle, Justin; Wedig, Olivia; Gulania, Sahil; Krylov, Anna I.; Mabbs, Richard

2017-12-01

We report photoelectron spectra of CH2CN-, recorded at photon energies between 13 460 and 15 384 cm-1, which show rapid intensity variations in particular detachment channels. The branching ratios for various spectral features reveal rotational structure associated with autodetachment from an intermediate anion state. Calculations using equation-of-motion coupled-cluster method with single and double excitations reveal the presence of two dipole-bound excited anion states (a singlet and a triplet). The computed oscillator strength for the transition to the singlet dipole-bound state provides an estimate of the autodetachment channel contribution to the total photoelectron yield. Analysis of the different spectral features allows identification of the dipole-bound and neutral vibrational levels involved in the autodetachment processes. For the most part, the autodetachment channels are consistent with the vibrational propensity rule and normal mode expectation. However, examination of the rotational structure shows that autodetachment from the ν3 (v = 1 and v = 2) levels of the dipole-bound state displays behavior counter to the normal mode expectation with the final state vibrational level belonging to a different mode.

I. Aspects of the Dark Matter Problem. II. Fermion Balls

NASA Astrophysics Data System (ADS)

Tetradis, Nikolaos Athanassiou

The first part of this thesis deals with the dark matter problem. A simple non-supersymmetric extension of the standard model is presented, which provides dark matter candidates not excluded by the existing dark matter searches. The simplest candidate is the neutral component of a zero hypercharge triplet, with vector gauge interactions. The upper bound on its mass is a few TeV. We also discuss possible modifications of the standard freeze-out scenario, induced by the presence of a phase transition. More specifically, if the critical temperature of the electroweak phase transition is sufficiently small, it can change the final abundances of heavy dark matter particles, by keeping them massless for a long time. Recent experimental bounds on the Higgs mass from LEP imply that this is not the case in the minimal standard model. In the second part we discuss non-trivial configurations, involving fermions which obtain their mass through Yukawa interactions with a scalar field. Under certain conditions, the vacuum expectation value of the scalar field is shifted from the minimum of the effective potential, in regions of high fermion density. This may result in the formation of fermion bound states. We study two such cases: (a) Using the non-linear SU(3)L times SU(3)R chiral Lagrangian coupled to a field theory of nuclear forces, we show that a bound state of baryons with a well defined surface may concievably form in the presence of kaon condensation. This state is of similar density to ordinary nuclei, but has net strangeness equal to about two thirds the baryon number. We discuss the properties of lumps of strange baryon matter with baryon number between ~20 and ~10 57 where gravitational effects become important. (b) The Higgs field near a very heavy top quark or any other heavy fermion is expected to be significantly deformed. By computing explicit solutions of the classical equations of motion for a spherically symmetric configuration without gauge fields, we show that in the standard model this cannot happen without violating either vacuum stability or perturbation theory at energies very close to the top quark mass.

Large enhancement of second harmonic generation from transition-metal dichalcogenide monolayer on grating near bound states in the continuum.

PubMed

Wang, Tiecheng; Zhang, Shihao

2018-01-08

Second harmonic generation from the two-layer structure where a transition-metal dichalcogenide monolayer is put on a one-dimensional grating has been studied. This grating supports bound states in the continuum which have no leakage lying within the continuum of radiation modes, we can enhance the second harmonic generation from the transition-metal dichalcogenide monolayer by more than four orders of magnitude based on the critical field enhancement near the bound states in the continuum. In order to complete this calculation, the scattering matrix theory has been extended to include the nonlinear effect and the scattering matrix of a two-dimensional material including nonlinear terms; furthermore, two methods to observe the bound states in the continuum are considered, where one is tuning the thickness of the grating and the other is changing the incident angle of the electromagnetic wave. We have also discussed various modulation of the second harmonic generation enhancement by adjusting the azimuthal angle of the transition-metal dichalcogenide monolayer.

Valence tautomerism in synthetic models of cytochrome P450

PubMed Central

Das, Pradip Kumar; Samanta, Subhra; McQuarters, Ashley B.; Lehnert, Nicolai

2016-01-01

CytP450s have a cysteine-bound heme cofactor that, in its as-isolated resting (oxidized) form, can be conclusively described as a ferric thiolate species. Unlike the native enzyme, most synthetic thiolate-bound ferric porphyrins are unstable in air unless the axial thiolate ligand is sterically protected. Spectroscopic investigations on a series of synthetic mimics of cytP450 indicate that a thiolate-bound ferric porphyrin coexists in organic solutions at room temperature (RT) with a thiyl-radical bound ferrous porphyrin, i.e., its valence tautomer. The ferric thiolate state is favored by greater enthalpy and is air stable. The ferrous thiyl state is favored by entropy, populates at RT, and degrades in air. These ground states can be reversibly interchanged at RT by the addition or removal of water to the apolar medium. It is concluded that hydrogen bonding and local electrostatics protect the resting oxidized cytP450 active site from degradation in air by stabilizing the ferric thiolate ground state in contrast to its synthetic analogs. PMID:27302948

Edge states at phase boundaries and their stability

NASA Astrophysics Data System (ADS)

Asorey, M.; Balachandran, A. P.; Pérez-Pardo, J. M.

2016-10-01

We analyze the effects of Robin-like boundary conditions on different quantum field theories of spin 0, 1/2 and 1 on manifolds with boundaries. In particular, we show that these conditions often lead to the appearance of edge states. These states play a significant role in physical phenomena like quantum Hall effect and topological insulators. We prove in a rigorous way the existence of spectral lower bounds on the kinetic term of different Hamiltonians, even in the case of Abelian gauge fields where it is a non-elliptic differential operator. This guarantees the stability and consistency of massive field theories with masses larger than the lower bound of the kinetic term. Moreover, we find an upper bound for the deepest edge state. In the case of Abelian gauge theories, we analyze a generalization of Robin boundary conditions. For Dirac fermions, we analyze the cases of Atiyah-Patodi-Singer and chiral bag boundary conditions. The explicit dependence of the bounds on the boundary conditions and the size of the system is derived under general assumptions.

TOPICAL REVIEW: O- bound small polarons in oxide materials

NASA Astrophysics Data System (ADS)

Schirmer, O. F.

2006-11-01

Holes bound to acceptor defects in oxide crystals are often localized by lattice distortion at just one of the equivalent oxygen ligands of the defect. Such holes thus form small polarons in symmetric clusters of a few oxygen ions. An overview on mainly the optical manifestations of those clusters is given. The article is essentially divided into two parts: the first one covers the basic features of the phenomena and their explanations, exemplified by several paradigmatic defects; in the second part numerous oxide materials are presented which exhibit bound small polaron optical properties. The first part starts with summaries on the production of bound hole polarons and the identification of their structure. It is demonstrated why they show strong, wide absorption bands, usually visible, based on polaron stabilization energies of typically 1 eV. The basic absorption process is detailed with a fictitious two-well system. Clusters with four, six and twelve equivalent ions are realized in various oxide compounds. In these cases several degenerate optically excited polaron states occur, leading to characteristic final state resonance splittings. The peak energies of the absorption bands as well as the sign of the transfer energy depend on the topology of the clusters. A special section is devoted to the distinction between interpolaron and intrapolaron optical transitions. The latter are usually comparatively weak. The oxide compounds exhibiting bound hole small polaron absorptions include the alkaline earth oxides (e.g. MgO), BeO and ZnO, the perovskites BaTiO3 and KTaO3, quartz, the sillenites (e.g. Bi12TiO20), Al2O3, LiNbO3, topaz and various other materials. There are indications that the magnetic crystals NiO, doped with Li, and LaMnO3, doped with Sr, also show optical features caused by bound hole polarons. Beyond being elementary paradigms for the properties of small polarons in general, the defect species treated can be used to explain radiation and light induced absorption especially in laser and non-linear oxide materials, the role of some defects in photorefractive compounds, the coloration of various gemstones, the structure of certain catalytic surface centres, etc. The relation to further phenomena is discussed: free small polarons, similar distorted centres in the sulfides and selenides, acceptor defects trapping two holes.

Adsorption Kinetics, Conformation, and Mobility of the Growth Hormone and Lysozyme on Solid Surfaces, Studied with TIRF

PubMed

Buijs; Hlady

1997-06-01

Interactions of recombinant human growth hormone and lysozyme with solid surfaces are studied using total internal reflection fluorescence (TIRF) and monitoring the protein's intrinsic tryptophan fluorescence. The intensity, spectra, quenching, and polarization of the fluorescence emitted by the adsorbed proteins are monitored and related to adsorption kinetics, protein conformation, and fluorophore rotational mobility. To study the influence of electrostatic and hydrophobic interactions on the adsorption process, three sorbent surfaces are used which differ in charge and hydrophobicity. The chemical surface groups are silanol, methyl, and quaternary amine. Results indicate that adsorption of hGH is dominated by hydrophobic interactions. Lysozyme adsoption is strongly affected by the ionic strength. This effect is probably caused by an ionic strength dependent conformational state in solution which, in turn, influences the affinity for adsorption. Both proteins are more strongly bound to hydrophobic surfaces and this strong interaction is accompanied by a less compact conformation. Furthermore, it was seen that regardless of the characteristics of the sorbent surface, the rotational mobility of both proteins' tryptophans is largely reduced upon adsorption.

Holographic entanglement entropy conjecture for general spacetimes

NASA Astrophysics Data System (ADS)

Sanches, Fabio; Weinberg, Sean J.

2016-10-01

We present a natural generalization of holographic entanglement entropy proposals beyond the scope of AdS /CFT by anchoring extremal surfaces to holographic screens. Holographic screens are a natural extension of the AdS boundary to arbitrary spacetimes and are preferred codimension-1 surfaces from the viewpoint of the covariant entropy bound. A broad class of screens have a unique preferred foliation into codimension-2 surfaces called leaves. Our proposal is to find the areas of extremal surfaces anchored to the boundaries of regions in leaves. We show that the properties of holographic screens are sufficient to prove, under generic conditions, that extremal surfaces anchored in this way always lie within a causal region associated with a given leaf. Within this causal region, a maximin construction similar to that of Wall proves that our proposed quantity satisfies standard properties of entanglement entropy like strong subadditivity. We conjecture that our prescription computes entanglement entropies in quantum states that holographically define arbitrary spacetimes, including those in a cosmological setting with no obvious boundary on which to anchor extremal surfaces.

Interaction of alkanes with an amorphous methanol film at 15-180 K

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

Souda, Ryutaro

2005-09-15

The hydrogen-bond imperfections and glass-liquid transition of the amorphous methanol film have been investigated on the basis of the film dewetting and the incorporation/desorption of alkane molecules adsorbed on the surface. The butane is incorporated completely in the bulk of the porous methanol film up to 70 K. At least two distinct states exist for the incorporated butane; one is assignable to solvated molecules in the bulk and the other is weakly bound species at the surface or in the subsurface site. For the nonporous methanol film, the uptake of butane in the bulk is quenched but butane forms amore » surface complex with methanol above 80 K. The butane incorporated in the bulk of the glassy methanol film is released at 120 K, where dewetting of the methanol film occurs simultaneously due to evolution of the supercooled liquid phase.« less

Use of response surface methodology for the assessment of changes in the volatile composition of Moscato bianco (Vitis vinifera L.) grape berries during ripening.

PubMed

Torchio, Fabrizio; Giacosa, Simone; Vilanova, Mar; Río Segade, Susana; Gerbi, Vincenzo; Giordano, Manuela; Rolle, Luca

2016-12-01

The changes in the volatile composition of Moscato bianco grapes were evaluated during ripening. Grape berries were sampled for five weeks (16-20 °Brix) and sorted for each date in ten density classes (1.05-1.12g/cm(3)). The highest total concentration of free terpenes was found at 19.3 °Brix; however, total concentration of the bound fraction increased significantly throughout ripening. Response surface methodology was used to assess the simultaneous effect of sampling time and berry density on the volatile composition, which was satisfactorily fitted to regression models for some key terpene compounds. Total free and bound terpenes were more affected by grape density than by sampling date. The same behaviour was observed for free and bound linalool and bound nerol, whereas the stronger effect of sampling date was exhibited for bound t-rose oxide, c-rose oxide and geraniol. The results showed that the sampling strategy impacted strongly on the aroma quality of berries. Copyright © 2016 Elsevier Ltd. All rights reserved.

Imaging of Formaldehyde Adsorption and Diffusion on TiO2(110)

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

Zhang, Zhenrong; Tang, Miru; Wang, Zhitao

2015-03-01

Surface reactions of formaldehyde with reduced TiO2(110) surfaces have been studied using variable-temperature scanning tunneling microscopy (STM) and density functional theory (DFT). STM results show that formaldehyde preferably adsorbs on the bridging bonded oxygen (Ob) vacancy (VO) defect site. Bias-dependent STM images show that both the Ti-bound CH2O and the VO-bound CH2O are positioned between the Ob row and the Ti row. The VO-bound formaldehyde rotates at 95 K. It starts to diffuse along the Ob row as –CH2– at ~170 K and starts to diffuse along the Ti row as a molecule at ~215 K. However, the stabilities andmore » the configurations of the Ti-bound and the VO-bound formaldehyde calculated using DFT are not in line with the experimental results. The values of diffusion barriers determined experimentally and theoretically are also different. The discrepancy between the experiment and theory indicates the presence of a complex charge distribution related to the defects.« less

Effect of nonmagnetic impurities on s+/- superconductivity in the presence of incipient bands

NASA Astrophysics Data System (ADS)

Chen, Xiao; Mishra, Vivek; Maiti, Saurabh; Hirschfeld, Peter

Several Fe chalcogenide superconductors without hole pockets at the Fermi level display high temperature superconductivity, in apparent contradiction to naive spin fluctuation pairing arguments. Recently, scanning tunneling microscopy measurements have measured the influence of impurities on some of these materials, and claimed that non-magnetic impurities do not create in-gap states, leading to the conclusion that the gap must be s+ +, i.e. conventional s wave with no gap sign change. Here we present various ways sign-changing gaps can be consistent with the absence of such bound states. In particular, we calculate the bound states for an s+/- system with a hole pocket below the Fermi level, and show that the nonmagnetic impurity bound state energy generically tracks the gap edge in the system, thereby rendering it unobservable. A failure to observe a bound state in the case of a nonmagnetic impurity can therefore not be used as an argument to exclude sign-changing pairing states. XC, SM and PJH were supported by NSF-DMR-1407502. VM was supported by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy.

Short Range Photoassociation of Rb2 by a high power fiber laser

NASA Astrophysics Data System (ADS)

Passagem, Henry; Rodriguez, Ricardo; Ventura, Paulo; Bouloufa, Nadia; Dulieu, Olivier; Marcassa, Luis

2016-05-01

Photoassociation has been studied using cold trapped atomic samples for the last 20 years. Due to poor Franck-Condon overlap, a free-to-bound transition followed by spontaneous decay results in a small production of electronic ground state molecules. If the photoassociation is done at short range, deeply bound ground state molecules can be formed. Optical pumping schemes can be used to populate a single state. In our experiment, we have performed trap loss spectroscopy on trapped 85 Rb atoms in a MOT using a high power fiber laser. Our single mode fiber laser (linewidth < 1 MHz) produces about 50 W, which can be tuned in the 1060-1070 nm range. Two vibrational bound states of the 0u+ potential were observed (ν = 137 and 138). The frequency positions as well as the rotational constants of these states are in good agreement with theoretical predictions. We have also measured the lifetime of a crossed optical dipole trap using such fiber laser. The lifetime on resonance is shorter than off resonance as expected. A simple theoretical model indicates that the molecules decay to deeply bound vibrational levels in the ground state. This work was supported by Fapesp and INCT-IQ.

Scattering and bound states of spinless particles in a mixed vector-scalar smooth step potential

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

Garcia, M.G.; Castro, A.S. de

2009-11-15

Scattering and bound states for a spinless particle in the background of a kink-like smooth step potential, added with a scalar uniform background, are considered with a general mixing of vector and scalar Lorentz structures. The problem is mapped into the Schroedinger-like equation with an effective Rosen-Morse potential. It is shown that the scalar uniform background present subtle and trick effects for the scattering states and reveals itself a high-handed element for formation of bound states. In that process, it is shown that the problem of solving a differential equation for the eigenenergies is transmuted into the simpler and moremore » efficient problem of solving an irrational algebraic equation.« less

Andreev bound states in a semiconducting nanowire Josephson junction, Part II: Quantum jumps and Fermion parity switching

NASA Astrophysics Data System (ADS)

Hays, M.; de Lange, G.; Serniak, K.; van Woerkom, D. J.; Väyrynen, J. I.; van Heck, B.; Vool, U.; Krogstrup, P.; Nygård, J.; Frunzio, L.; Geresdi, A.; Glazman, L. I.; Devoret, M. H.

Proximitized semiconducting nanowires subject to magnetic field should display topological superconductivity and support Majorana zero modes which have non-Abelian braiding statistics. The conventional Andreev levels formed in such wires in the absence of field are a precursor to these exotic zero modes. The fermion-parity switching time of Andreev levels sets a lower bound on the bandwidth required for experiments aimed at harnessing non-Abelian braiding statistics. We demonstrate the observation of quantum jumps between even and odd-parity states of an individual Andreev bound state in a non-topological junction, providing a direct measurement of the state populations and the parity lifetime. Work supported by: ARO, ONR, AFOSR, EU Marie Curie and YINQE.

Response to “Comment on ‘Propagation of surface waves on a semi-bounded quantum magnetized collisional plasma’” [Phys. Plasmas 23, 044701 (2016)

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

Niknam, A. R., E-mail: a-niknam@sbu.ac.ir; Taheri Boroujeni, S.; Khorashadizadeh, S. M., E-mail: smkhorashadi@birjand.ac.ir

2016-04-15

We reply to the Comment of Moradi [Phys. Plasmas 23, 044701 (2016)] on our paper [Phys. Plasmas 20, 122106 (2013)]. It is shown that TM surface waves can propagate on the surface of a semi-bounded quantum magnetized collisional plasma in the Faraday configuration in the electrostatic limit. In addition, in the Faraday configuration, one can neglect the coupling of TM and TE modes in the two limiting cases of weak magnetic field (low cyclotron frequency) and strong magnetic field (high cyclotron frequency).

How entangled can a multi-party system possibly be?

NASA Astrophysics Data System (ADS)

Qi, Liqun; Zhang, Guofeng; Ni, Guyan

2018-06-01

The geometric measure of entanglement of a pure quantum state is defined to be its distance to the space of pure product (separable) states. Given an n-partite system composed of subsystems of dimensions d1 , … ,dn, an upper bound for maximally allowable entanglement is derived in terms of geometric measure of entanglement. This upper bound is characterized exclusively by the dimensions d1 , … ,dn of composite subsystems. Numerous examples demonstrate that the upper bound appears to be reasonably tight.

Invariant criteria for bound states, degree of ionization, and plasma phase transition

NASA Technical Reports Server (NTRS)

Girardeau, M. D.

1990-01-01

Basis invariant characterizations of bound states and bound fraction of a partially ionized hydrogen plasma are given in terms of properties of the spectrum of eigenvalues and eigenfunctions of the equilibrium quantum statistical one-proton-one-electron reduced density matrix. It is suggested that these can be used to place theories of a proposed plasma-ionization phase transition on a firm foundation. This general approach may be relevant to cosmological questions such as the quark deconfinement-confinement transition.

Measurements of electron detection efficiencies in solid state detectors.

NASA Technical Reports Server (NTRS)

Lupton, J. E.; Stone, E. C.

1972-01-01

Detailed laboratory measurement of the electron response of solid state detectors as a function of incident electron energy, detector depletion depth, and energy-loss discriminator threshold. These response functions were determined by exposing totally depleted silicon surface barrier detectors with depletion depths between 50 and 1000 microns to the beam from a magnetic beta-ray spectrometer. The data were extended to 5000 microns depletion depth using the results of previously published Monte Carlo electron calculations. When the electron counting efficiency of a given detector is plotted as a function of energy-loss threshold for various incident energies, the efficiency curves are bounded by a smooth envelope which represents the upper limit to the detection efficiency. These upper limit curves, which scale in a simple way, make it possible to easily estimate the electron sensitivity of solid-state detector systems.

Influence of Magnetic Ordering between Cr Adatoms on the Yu-Shiba-Rusinov States of the β -Bi2Pd Superconductor

NASA Astrophysics Data System (ADS)

Choi, Deung-Jang; Fernández, Carlos García; Herrera, Edwin; Rubio-Verdú, Carmen; Ugeda, Miguel M.; Guillamón, Isabel; Suderow, Hermann; Pascual, José Ignacio; Lorente, Nicolás

2018-04-01

We show that the magnetic ordering of coupled atomic dimers on a superconductor is revealed by their intragap spectral features. Chromium atoms on the superconductor β -Bi2Pd surface display Yu-Shiba-Rusinov bound states, detected as pairs of intragap excitations in tunneling spectra. By means of atomic manipulation with a scanning tunneling microscope's tip, we form Cr dimers with different arrangements and find that their intragap features appear either shifted or split with respect to single atoms. These spectral variations are associated with the magnetic coupling, ferromagnetic or antiferromagnetic, of the dimer, as confirmed by density functional theory simulations. The striking qualitative differences between the observed tunneling spectra prove that intragap Shiba states are extremely sensitive to the magnetic ordering on the atomic scale.

New method for taking into account finite nuclear mass in the determination of the absence of bound states: Application to e/sup +/H

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

Armour, E.A.G.

1982-06-07

It has been known since the work of Aronson, Kleinman and Spruch, and Armour that, if the proton is considered to be infinitely massive, no bound state of a system made up of a positron and a hydrogen atom can exist. In this Letter a new method is introduced for taking into account finite nuclear mass. With use of this method it is shown that the inclusion of the finite mass of the proton does not result in the appearance of a bound state. This is the first time that this result has been established.

Free surface convection in a bounded cylindrical geometry

NASA Astrophysics Data System (ADS)

Vrentas, J. S.; Narayanan, R.; Agrawal, S. S.

1981-09-01

Surface tension-driven convection and buoyancy-driven convection in a bounded cylindrical geometry with a free surface are studied for a range of aspect ratios and Nusselt numbers. The thermal convection is in a liquid layer contained in a vertical circular cylinder with a single free boundary, the top surface, which is in contact with an inviscid gas phase. A different method is also developed for analyzing free convection problems using Green's functions, reducing the problem to the solution of an integral equation. Linear theory and some aspects of a nonlinear analysis are utilized to determine the critical Marangoni and Rayleigh numbers, the structure of the convective motion, the direction of flow, and the nature of the bifurcation branching.

Fast photo-switchable surfaces for boiling heat transfer applications

NASA Astrophysics Data System (ADS)

Hunter, C. N.; Turner, D. B.; Jespersen, M. L.; Check, M. H.; Borton, P. T.; Glavin, N. R.; Voevodin, A. A.

2012-11-01

Several milligrams of the ruthenium-centered organometallic complex, ruthenium bis-4,4'-di(thiomethyl)-2,2'-bipyridine, mono-2 -(2-pyridyl)-1,3-oxathiane ([Ru{(HS-CH2)2-bpy}2{pox}](PF6)2) were synthesized and used to produce a self assembled monolayer film on a gold substrate. X-ray photoelectron spectroscopy analysis of the film detected the presence of bound thiolate, which is an indication of a chemisorbed film. Water contact angle measurements were performed before and after 5 min of visible light irradiation using an ozone-free 1000 W Xe(Hg) arc source with a 425-680 nm long pass mirror. The contact angle changed from 52° pre-irradiation (hydrophilic state) to 95° post-irradiation (hydrophobic state).

Vibronic Transitions in the X-Sr Series (X=Li, Na, K, Rb): on the Accuracy of Nuclear Wavefunctions Derived from Quantum Chemistry

NASA Astrophysics Data System (ADS)

Meyer, Ralf; Pototschnig, Johann V.; Hauser, Andreas W.; Ernst, Wolfgang E.

2016-06-01

Research on ultracold molecules has seen a growing interest recently in the context of high-resolution spectroscopy and quantum computation. The preparation of molecules in low vibrational levels of the ground state is experimentally challenging, and typically achieved by population transfer using excited electronic states. On the theoretical side, highly accurate potential energy surfaces are needed for a correct description of processes such as the coherent de-excitation from the highest and therefore weakly bound vibrational levels in the electronic ground state via couplings to electronically excited states. Particularly problematic is the correct description of potential features at large intermolecular distances. Franck-Condon overlap integrals for nuclear wavefunctions in barely bound vibrational states are extremely sensitive to inaccuracies of the potential at long range. In this study, we compare the predictions of common, wavefunction-based ab initio techniques for a known de-excitation mechanism in alkali-alkaline earth dimers. It is the aim to analyze the predictive power of these methods for a preliminary evaluation of potential cooling mechanisms in heteronuclear open shell systems which offer the experimentalist an electric as well as a magnetic handle for manipulation. The series of X-Sr molecules, with X = Li, Na, K and Rb, has been chosen for a direct comparison. Quantum degenerate mixtures of Rb and Sr have already been produced, making this combination very promising for the production of ultracold molecules. B. Pasquiou, A. Bayerle, S. M. Tzanova, S. Stellmer, J. Szczepkowski, M. Parigger, R. Grimm, and F. Schreck, Phys. Rev. A, 2013, 88, 023601

Schmidt-number witnesses and bound entanglement

NASA Astrophysics Data System (ADS)

Sanpera, Anna; Bruß, Dagmar; Lewenstein, Maciej

2001-05-01

The Schmidt number of a mixed state characterizes the minimum Schmidt rank of the pure states needed to construct it. We investigate the Schmidt number of an arbitrary mixed state by studying Schmidt-number witnesses that detect it. We present a canonical form of such witnesses and provide constructive methods for their optimization. Finally, we present strong evidence that all bound entangled states with positive partial transpose in C3⊗C3 have Schmidt number 2.

Partitioning of dissolved organic matter-bound mercury between a hydrophobic surface and polysulfide-rubber polymer.

PubMed

Kim, Eun-Ah; Luthy, Richard G

2011-11-01

This study investigated the role of dissolved organic matter on mercury partitioning between a hydrophobic surface (polyethylene, PE) and a reduced sulfur-rich surface (polysulfide rubber, PSR). Comparative sorption studies employed polyethylene and polyethylene coated with PSR for reactions with DOM-bound mercuric ions. These studies revealed that PSR enhanced the Hg-DOM removal from water when DOM was Suwannee River natural organic matter (NOM), fulvic acid (FA), or humic acid (HA), while the same amount of 1,3-propanedithiol-bound mercuric ion was removed by both PE and PSR-PE. The differences for Hg-DOM removal efficiencies between PE and PSR-PE varied depending on which DOM was bound to mercuric ion as suggested by the PE/water and PSR-PE/water partition coefficients for mercury. The surface concentrations of mercury on PE and PSR-PE with the same DOM measured by x-ray photoelectron spectroscopy were similar, which indicated the comparable amounts of immobilized mercury on PE and PSR-PE being exposed to the aqueous phase. With these observations, two major pathways for the immobilization reactions between PSR-PE and Hg-DOM were examined: 1) adsorption of Hg-DOM on PE by hydrophobic interactions between DOM and PE, and 2) addition reaction of Hg-DOM onto PSR by a complexation reaction between Hg and PSR. The percent contribution of each pathway was derived from a mass balance and the ratios among aqueous mercury, PE-bound Hg-DOM, and PSR-bound Hg-DOM concentrations. The results indicate strong binding of mercuric ion with both dissolved organic matter and PSR polymer. The FT-IR examination of Hg-preloaded-PSR-PEs after the reaction with DOM corroborated a strong interaction between mercuric ion and 1,3-propanedithiol compared to Hg-HA, Hg-FA, or Hg-NOM interactions. Copyright © 2011 Elsevier Ltd. All rights reserved.

Partitioning of dissolved organic matter-bound mercury between a hydrophobic surface and polysulfide-rubber polymer

PubMed Central

Kim, Eun-Ah

2011-01-01

This study investigated the role of dissolved organic matter on mercury partitioning between a hydrophobic surface (polyethylene, PE) and a reduced sulfur-rich surface (polysulfide rubber, PSR). Comparative sorption studies employed polyethylene and polyethylene coated with PSR for reactions with DOM-bound mercuric ions. These studies revealed that PSR enhanced the Hg-DOM removal from water when DOM was Suwannee River natural organic matter (NOM), fulvic acid (FA), or humic acid (HA), while the same amount of 1,3-propanedithiol-bound mercuric ion was removed by both PE and PSR-PE. The differences for Hg-DOM removal efficiencies between PE and PSR-PE varied depending on which DOM was bound to mercuric ion as suggested by the PE/water and PSR-PE/water partition coefficients for mercury. The surface concentrations of mercury on PE and PSR-PE with the same DOM measured by x-ray – photoelectron spectroscopy were similar, which indicated the comparable amounts of immobilized mercury on PE and PSR-PE being exposed to the aqueous phase. With these observations, two major pathways for the immobilization reactions between PSR-PE and Hg- DOM were examined: 1) adsorption of Hg-DOM on PE by hydrophobic interactions between DOM and PE, and 2) addition reaction of Hg-DOM onto PSR by a complexation reaction between Hg and PSR. The percent contribution of each pathway was derived from a mass balance and the ratios among aqueous mercury, PE-bound Hg-DOM, and PSR-bound Hg-DOM concentrations. The results indicate strong binding of mercuric ion with both dissolved organic matter and PSR polymer. The FT-IR examination of Hg-preloaded-PSR-PEs after the reaction with DOM corroborated a strong interaction between mercuric ion and 1,3-propanedithiol compared to Hg-HA, Hg-FA, or Hg-NOM interactions. PMID:21872900

Wronskian Method for Bound States

ERIC Educational Resources Information Center

Fernandez, Francisco M.

2011-01-01

We propose a simple and straightforward method based on Wronskians for the calculation of bound-state energies and wavefunctions of one-dimensional quantum-mechanical problems. We explicitly discuss the asymptotic behaviour of the wavefunction and show that the allowed energies make the divergent part vanish. As illustrative examples we consider…

Bounds on area and charge for marginally trapped surfaces with a cosmological constant

NASA Astrophysics Data System (ADS)

Simon, Walter

2012-03-01

We sharpen the known inequalities AΛ ⩽ 4π(1 - g) (Hayward et al 1994 Phys. Rev. D 49 5080, Woolgar 1999 Class. Quantum Grav. 16 3005) and A ⩾ 4πQ2 (Dain et al 2012 Class. Quantum Grav. 29 035013) between the area A and the electric charge Q of a stable marginally outer-trapped surface (MOTS) of genus g in the presence of a cosmological constant Λ. In particular, instead of requiring stability we include the principal eigenvalue λ of the stability operator. For Λ* = Λ + λ > 0, we obtain a lower and an upper bound for Λ*A in terms of Λ*Q2, as well as the upper bound Q \\le 1/(2\\sqrt{\\Lambda ^{*}}) for the charge, which reduces to Q \\le 1/(2\\sqrt{\\Lambda }) in the stable case λ ⩾ 0. For Λ* < 0, there only remains a lower bound on A. In the spherically symmetric, static, stable case, one of our area inequalities is saturated iff the surface gravity vanishes. We also discuss implications of our inequalities for ‘jumps’ and mergers of charged MOTS.

Dynamics at Lys-553 of the acto-myosin interface in the weakly and strongly bound states.

PubMed Central

MacLean, J J; Chrin, L R; Berger, C L

2000-01-01

Lys-553 of skeletal muscle myosin subfragment 1 (S1) was specifically labeled with the fluorescent probe FHS (6-[fluorescein-5(and 6)-carboxamido]hexanoic acid succinimidyl ester) and fluorescence quenching experiments were carried out to determine the accessibility of this probe at Lys-553 in both the strongly and weakly actin-bound states of the MgATPase cycle. Solvent quenchers of varying charge [nitromethane, (2,2,6, 6-tetramethyl-1-piperinyloxy) (TEMPO), iodide (I(-)), and thallium (Tl(+))] were used to assess both the steric and electrostatic accessibilities of the FHS probe at Lys-553. In the strongly bound rigor (nucleotide-free) and MgADP states, actin offered no protection from solvent quenching of FHS by nitromethane, TEMPO, or thallium, but did decrease the Stern-Volmer constant by almost a factor of two when iodide was used as the quencher. The protection from iodide quenching was almost fully reversed with the addition of 150 mM KCl, suggesting this effect is ionic in nature rather than steric. Conversely, actin offered no protection from iodide quenching at low ionic strength during steady-state ATP hydrolysis, even with a significant fraction of the myosin heads bound to actin. Thus, the lower 50 kD subdomain of myosin containing Lys-553 appears to interact differently with actin in the weakly and strongly bound states. PMID:10692329

Late Quaternary Stratigraphic Architecture of the Santee River Delta, South Carolina, U.S.A.

NASA Astrophysics Data System (ADS)

Long, J. H.; Hanebuth, T. J. J.

2017-12-01

The Santee River of South Carolina is the second largest river in terms of drainage area and discharge in the eastern United States and forms the only river-fed delta on the country's Atlantic coast. Significant anthropogenic modifications to this system date back to the early 18th century with the extensive clearing of coastal wetland forest for rice cultivation. In the 1940's the construction of large upstream dams permanently altered the discharge of the Santee River. These modifications are likely documented within the sedimentary record of the Santee Delta as episodes of major environmental changes. The Piedmont-sourced Santee River system incised its valley to an estimated depth of 20 m during lower glacial sea level. Sedimentation during the subsequent Holocene transgression and highstand has filled much of this accommodation. The Santee system remains largely under-investigated with only a handful of studies completed in the 1970's and 1980's based on sediment cores and cuttings. Through the use of high frequency seismic profiles (0.5 - 24 kHz), sediment cores, and other field data, we differentiate depositional units, architectural elements, and bounding surfaces with temporal and spatial distributions reflecting the changing morphodynamics of this complex system at multiple scales. These lithosomes are preserved within both modern inshore and offshore settings and were deposited within a range of paralic environments by processes active on fluvial/estuarine bars, floodplains, marshes, tidal flats, spits, beach ridges, and in backbarrier settings. They are bound by surfaces ranging from diastems to regional, polygenetic, low-angle and channel-form erosional surfaces. Detailed descriptions of cores taken from within the upper 6 m of the modern lower delta plain document heterolithic, mixed-energy, organic-rich, largely aggradational sedimentation dating back to at least 5 ka cal BP. Offshore, stacked, sand-rich, progradational packages sit atop heterolithic paleochannel-fill successions contained within a framework of regionally extensive, erosional bounding surfaces. Ongoing work focuses on continued data acquisition and integration of inshore and offshore data sets into a coherent model for the Holocene evolution of the Santee Delta.

Optical Feshbach resonances and ground-state-molecule production in the RbHg system

NASA Astrophysics Data System (ADS)

Borkowski, Mateusz; Muñoz Rodriguez, Rodolfo; Kosicki, Maciej B.; Ciuryło, Roman; Żuchowski, Piotr S.

2017-12-01

We present the prospects for photoassociation, optical control of interspecies scattering lengths, and, finally, the production of ultracold absolute ground-state molecules in the Rb+Hg system. We use the state-of-the-art ab initio methods for the calculations of ground- [CCSD(T)] and excited-state (EOM-CCSD) potential curves. The RbHg system, thanks to the wide range of stable Hg bosonic isotopes, offers possibilities for mass tuning of ground-state interactions. The optical lengths describing the strengths of optical Feshbach resonances near the Rb transitions are favorable even at large laser detunings. Ground-state RbHg molecules can be produced with efficiencies ranging from about 20% for deeply bound to at least 50% for weakly bound states close to the dissociation limit. Finally, electronic transitions with favorable Franck-Condon factors can be found for the purposes of a STIRAP transfer of the weakly bound RbHg molecules to the absolute ground state using commercially available lasers.

Energy Landscape and Transition State of Protein-Protein Association

NASA Astrophysics Data System (ADS)

Alsallaq, Ramzi; Zhou, Huan-Xiang

2006-11-01

Formation of a stereospecific protein complex is favored by specific interactions between two proteins but disfavored by the loss of translational and rotational freedom. Echoing the protein folding process, we have previously proposed a transition state for protein-protein association. Here we clarify the specification of the transition state by working with two toy models for protein association. The models demonstrate that a sharp transition between the bound state with numerous short-range interactions but restricted translation and rotational freedom and the unbound state with at most a small number of interactions but expanded configurational freedom. This transition sets the outer boundary of the bound state as well as the transition state for association. The energy landscape is funnel-like, with the deep well of the bound state surrounded by a broad shallow basin. This formalism of protein-protein association is applied to four protein-protein complexes, and is found to give accurate predictions for the effects of charge mutations and ionic strength on the association rates.

Metal Halide Solid-State Surface Treatment for High Efficiency PbS and PbSe QD Solar Cells

PubMed Central

Crisp, Ryan W.; Kroupa, Daniel M.; Marshall, Ashley R.; Miller, Elisa M.; Zhang, Jianbing; Beard, Matthew C.; Luther, Joseph M.

2015-01-01

We developed a layer-by-layer method of preparing PbE (E = S or Se) quantum dot (QD) solar cells using metal halide (PbI2, PbCl2, CdI2, or CdCl2) salts dissolved in dimethylformamide to displace oleate surface ligands and form conductive QD solids. The resulting QD solids have a significant reduction in the carbon content compared to films treated with thiols and organic halides. We find that the PbI2 treatment is the most successful in removing alkyl surface ligands and also replaces most surface bound Cl- with I-. The treatment protocol results in PbS QD films exhibiting a deeper work function and band positions than other ligand exchanges reported previously. The method developed here produces solar cells that perform well even at film thicknesses approaching a micron, indicating improved carrier transport in the QD films. We demonstrate QD solar cells based on PbI2 with power conversion efficiencies above 7%. PMID:25910183

Rapid ultrasensitive single particle surface-enhanced Raman spectroscopy using metallic nanopores.

PubMed

Cecchini, Michael P; Wiener, Aeneas; Turek, Vladimir A; Chon, Hyangh; Lee, Sangyeop; Ivanov, Aleksandar P; McComb, David W; Choo, Jaebum; Albrecht, Tim; Maier, Stefan A; Edel, Joshua B

2013-10-09

Nanopore sensors embedded within thin dielectric membranes have been gaining significant interest due to their single molecule sensitivity and compatibility of detecting a large range of analytes, from DNA and proteins, to small molecules and particles. Building on this concept we utilize a metallic Au solid-state membrane to translocate and rapidly detect single Au nanoparticles (NPs) functionalized with 589 dye molecules using surface-enhanced resonance Raman spectroscopy (SERRS). We show that, due to the plasmonic coupling between the Au metallic nanopore surface and the NP, signal intensities are enhanced when probing analyte molecules bound to the NP surface. Although not single molecule, this nanopore sensing scheme benefits from the ability of SERRS to provide rich vibrational information on the analyte, improving on current nanopore-based electrical and optical detection techniques. We show that the full vibrational spectrum of the analyte can be detected with ultrahigh spectral sensitivity and a rapid temporal resolution of 880 μs.

Metal halide solid-state surface treatment for high efficiency PbS and PbSe QD solar cells.

PubMed

Crisp, Ryan W; Kroupa, Daniel M; Marshall, Ashley R; Miller, Elisa M; Zhang, Jianbing; Beard, Matthew C; Luther, Joseph M

2015-04-24

We developed a layer-by-layer method of preparing PbE (E = S or Se) quantum dot (QD) solar cells using metal halide (PbI2, PbCl2, CdI2, or CdCl2) salts dissolved in dimethylformamide to displace oleate surface ligands and form conductive QD solids. The resulting QD solids have a significant reduction in the carbon content compared to films treated with thiols and organic halides. We find that the PbI2 treatment is the most successful in removing alkyl surface ligands and also replaces most surface bound Cl(-) with I(-). The treatment protocol results in PbS QD films exhibiting a deeper work function and band positions than other ligand exchanges reported previously. The method developed here produces solar cells that perform well even at film thicknesses approaching a micron, indicating improved carrier transport in the QD films. We demonstrate QD solar cells based on PbI2 with power conversion efficiencies above 7%.

Metal Halide Solid-State Surface Treatment for High Efficiency PbS and PbSe QD Solar Cells

DOE PAGES

Crisp, R. W.; Kroupa, D. M.; Marshall, A. R.; ...

2015-04-24

We developed a layer-by-layer method of preparing PbE (E = S or Se) quantum dot (QD) solar cells using metal halide (PbI 2, PbCl 2, CdI 2, or CdCl 2) salts dissolved in dimethylformamide to displace oleate surface ligands and form conductive QD solids. The resulting QD solids have a significant reduction in the carbon content compared to films treated with thiols and organic halides. We find that the PbI 2 treatment is the most successful in removing alkyl surface ligands and also replaces most surface bound Cl- with I-. The treatment protocol results in PbS QD films exhibiting amore » deeper work function and band positions than other ligand exchanges reported previously. The method developed here produces solar cells that perform well even at film thicknesses approaching a micron, indicating improved carrier transport in the QD films. We demonstrate QD solar cells based on PbI 2 with power conversion efficiencies above 7%.« less

Emergent low-energy bound states in the two-orbital Hubbard model

DOE PAGES

Nunez-Fernandez, Y.; Kotliar, G.; Hallberg, K.

2018-03-30

A repulsive Coulomb interaction between electrons in different orbitals in correlated materials can give rise to bound quasiparticle states. We study the nonhybridized two-orbital Hubbard model with intra- (inter)orbital interaction U (U 12) and different bandwidths using an improved dynamical mean-field theory numerical technique which leads to reliable spectra on the real energy axis directly at zero temperature. We find that a finite density of states at the Fermi energy in one band is correlated with the emergence of well-defined quasiparticle states at excited energies Δ = U - U 12 in the other band. These excitations are interband holon-doublonmore » bound states. At the symmetric point U = U 12, the quasiparticle peaks are located at the Fermi energy, leading to a simultaneous and continuous Mott transition settling a long-standing controversy.« less

Temporal analysis of nonresonant two-photon coherent control involving bound and dissociative molecular states

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

Su Jing; Chen Shaohao; Jaron-Becker, Agnieszka

We theoretically study the control of two-photon excitation to bound and dissociative states in a molecule induced by trains of laser pulses, which are equivalent to certain sets of spectral phase modulated pulses. To this end, we solve the time-dependent Schroedinger equation for the interaction of molecular model systems with an external intense laser field. Our numerical results for the temporal evolution of the population in the excited states show that, in the case of an excited dissociative state, control schemes, previously validated for the atomic case, fail due to the coupling of electronic and nuclear motion. In contrast, formore » excitation to bound states the two-photon excitation probability is controlled via the time delay and the carrier-envelope phase difference between two consecutive pulses in the train.« less

Tight upper bound for the maximal quantum value of the Svetlichny operators

NASA Astrophysics Data System (ADS)

Li, Ming; Shen, Shuqian; Jing, Naihuan; Fei, Shao-Ming; Li-Jost, Xianqing

2017-10-01

It is a challenging task to detect genuine multipartite nonlocality (GMNL). In this paper, the problem is considered via computing the maximal quantum value of Svetlichny operators for three-qubit systems and a tight upper bound is obtained. The constraints on the quantum states for the tightness of the bound are also presented. The approach enables us to give the necessary and sufficient conditions of violating the Svetlichny inequality (SI) for several quantum states, including the white and color noised Greenberger-Horne-Zeilinger (GHZ) states. The relation between the genuine multipartite entanglement concurrence and the maximal quantum value of the Svetlichny operators for mixed GHZ class states is also discussed. As the SI is useful for the investigation of GMNL, our results give an effective and operational method to detect the GMNL for three-qubit mixed states.

Emergent low-energy bound states in the two-orbital Hubbard model

NASA Astrophysics Data System (ADS)

Núñez-Fernández, Y.; Kotliar, G.; Hallberg, K.

2018-03-01

A repulsive Coulomb interaction between electrons in different orbitals in correlated materials can give rise to bound quasiparticle states. We study the nonhybridized two-orbital Hubbard model with intra- (inter)orbital interaction U (U12) and different bandwidths using an improved dynamical mean-field theory numerical technique which leads to reliable spectra on the real energy axis directly at zero temperature. We find that a finite density of states at the Fermi energy in one band is correlated with the emergence of well-defined quasiparticle states at excited energies Δ =U -U12 in the other band. These excitations are interband holon-doublon bound states. At the symmetric point U =U12 , the quasiparticle peaks are located at the Fermi energy, leading to a simultaneous and continuous Mott transition settling a long-standing controversy.

Activation of Cell Surface Bound 20S Proteasome Inhibits Vascular Cell Growth and Arteriogenesis

PubMed Central

Ito, Wulf D.; Lund, Natalie; Zhang, Ziyang; Buck, Friedrich; Lellek, Heinrich; Horst, Andrea; Machens, Hans-Günther; Schunkert, Heribert; Schaper, Wolfgang; Meinertz, Thomas

2015-01-01

Arteriogenesis is an inflammatory process associated with rapid cellular changes involving vascular resident endothelial progenitor cells (VR-EPCs). Extracellular cell surface bound 20S proteasome has been implicated to play an important role in inflammatory processes. In our search for antigens initially regulated during collateral growth mAb CTA 157-2 was generated against membrane fractions of growing collateral vessels. CTA 157-2 stained endothelium of growing collateral vessels and the cell surface of VR-EPCs. CTA 157-2 bound a protein complex (760 kDa) that was identified as 26 kDa α7 and 21 kDa β3 subunit of 20S proteasome in mass spectrometry. Furthermore we demonstrated specific staining of 20S proteasome after immunoprecipitation of VR-EPC membrane extract with CTA 157-2 sepharose beads. Functionally, CTA 157-2 enhanced concentration dependently AMC (7-amino-4-methylcoumarin) cleavage from LLVY (N-Succinyl-Leu-Leu-Val-Tyr) by recombinant 20S proteasome as well as proteasomal activity in VR-EPC extracts. Proliferation of VR-EPCs (BrdU incorporation) was reduced by CTA 157-2. Infusion of the antibody into the collateral circulation reduced number of collateral arteries, collateral proliferation, and collateral conductance in vivo. In conclusion our results indicate that extracellular cell surface bound 20S proteasome influences VR-EPC function in vitro and collateral growth in vivo. PMID:26146628

Molecular alignment effect on the photoassociation process via a pump-dump scheme.

PubMed

Wang, Bin-Bin; Han, Yong-Chang; Cong, Shu-Lin

2015-09-07

The photoassociation processes via the pump-dump scheme for the heternuclear (Na + H → NaH) and the homonuclear (Na + Na → Na2) molecular systems are studied, respectively, using the time-dependent quantum wavepacket method. For both systems, the initial atom pair in the continuum of the ground electronic state (X(1)Σ(+)) is associated into the molecule in the bound states of the excited state (A(1)Σ(+)) by the pump pulse. Then driven by a time-delayed dumping pulse, the prepared excited-state molecule can be transferred to the bound states of the ground electronic state. It is found that the pump process can induce a superposition of the rovibrational levels |v, j〉 on the excited state, which can lead to the field-free alignment of the excited-state molecule. The molecular alignment can affect the dumping process by varying the effective coupling intensity between the two electronic states or by varying the population transfer pathways. As a result, the final population transferred to the bound states of the ground electronic state varies periodically with the delay time of the dumping pulse.

Molecular alignment effect on the photoassociation process via a pump-dump scheme

NASA Astrophysics Data System (ADS)

Wang, Bin-Bin; Han, Yong-Chang; Cong, Shu-Lin

2015-09-01

The photoassociation processes via the pump-dump scheme for the heternuclear (Na + H → NaH) and the homonuclear (Na + Na → Na2) molecular systems are studied, respectively, using the time-dependent quantum wavepacket method. For both systems, the initial atom pair in the continuum of the ground electronic state (X1Σ+) is associated into the molecule in the bound states of the excited state (A1Σ+) by the pump pulse. Then driven by a time-delayed dumping pulse, the prepared excited-state molecule can be transferred to the bound states of the ground electronic state. It is found that the pump process can induce a superposition of the rovibrational levels |v, j> on the excited state, which can lead to the field-free alignment of the excited-state molecule. The molecular alignment can affect the dumping process by varying the effective coupling intensity between the two electronic states or by varying the population transfer pathways. As a result, the final population transferred to the bound states of the ground electronic state varies periodically with the delay time of the dumping pulse.

Binding of leachable components of polymethyl methacrylate (PMMA) and peptide on modified SPR chip

NASA Astrophysics Data System (ADS)

Szaloki, M.; Vitalyos, G.; Harfalvi, J.; Hegedus, Cs

2013-12-01

Many types of polymers are often used in dentistry, which may cause allergic reaction, mainly methyl methacrylate allergy due to the leachable, degradable components of polymerized dental products. The aim of this study was to investigate the interaction between the leachable components of PMMA and peptides by Fourier-transform Surface Plasmon Resonance (FT SPR). In our previous work binding of oligopeptides (Ph.D.-7 and Ph.D.-12 Peptide Library Kit) was investigated to PMMA surface by phage display technique. It was found that oligopeptides bounded specifically to PMMA surface. The most common amino acids were leucine and proline inside the amino acids sequences of DNA of phages. The binding of haptens, as formaldehyde and methacrylic acid, to frequent amino acids was to investigate on the modified gold SPR chip. Self assembled monolayer (SAM) modified the surface of gold chip and ensured the specific binding between the haptens and amino acids. It was found that amino acids bounded to modified SPR gold and the haptens bounded to amino acids by creating multilayer on the chip surface. By the application of phage display and SPR modern bioanalytical methods the interaction between allergens and peptides can be investigated.

On the relation between Marcus theory and ultrafast spectroscopy of solvation kinetics

NASA Astrophysics Data System (ADS)

Roy, Santanu; Galib, Mirza; Schenter, Gregory K.; Mundy, Christopher J.

2018-01-01

The phenomena of solvent exchange control the process of solvating ions, protons, and charged molecules. Building upon our extension of Marcus' philosophy of electron transfer, we provide a new perspective of ultrafast solvent exchange mechanism around ions measurable by two-dimensional infrared (2DIR) spectroscopy. In this theory, solvent rearrangement drives an ion-bound water to an activated state of higher coordination number, triggering ion-water separation that leads to the solvent-bound state of the water molecule. This ion-bound to solvent-bound transition rate for a BF4--water system is computed using ab initio molecular dynamics and Marcus theory, and is found to be in excellent agreement with the 2DIR measurement.

Performance bounds on parallel self-initiating discrete-event

NASA Technical Reports Server (NTRS)

Nicol, David M.

1990-01-01

The use is considered of massively parallel architectures to execute discrete-event simulations of what is termed self-initiating models. A logical process in a self-initiating model schedules its own state re-evaluation times, independently of any other logical process, and sends its new state to other logical processes following the re-evaluation. The interest is in the effects of that communication on synchronization. The performance is considered of various synchronization protocols by deriving upper and lower bounds on optimal performance, upper bounds on Time Warp's performance, and lower bounds on the performance of a new conservative protocol. The analysis of Time Warp includes the overhead costs of state-saving and rollback. The analysis points out sufficient conditions for the conservative protocol to outperform Time Warp. The analysis also quantifies the sensitivity of performance to message fan-out, lookahead ability, and the probability distributions underlying the simulation.

Directional detection of dark matter in universal bound states

DOE PAGES

Laha, Ranjan

2015-10-06

It has been suggested that several small-scale structure anomalies in Λ CDM cosmology can be solved by strong self-interaction between dark matter particles. It was shown in Ref. [1] that the presence of a near threshold S-wave resonance can make the scattering cross section at nonrelativistic speeds come close to saturating the unitarity bound. This can result in the formation of a stable bound state of two asymmetric dark matter particles (which we call darkonium). Ref. [2] studied the nuclear recoil energy spectrum in dark matter direct detection experiments due to this incident bound state. Here we study the angularmore » recoil spectrum, and show that it is uniquely determined up to normalization by the S-wave scattering length. Furthermore, observing this angular recoil spectrum in a dark matter directional detection experiment will uniquely determine many of the low-energy properties of dark matter independent of the underlying dark matter microphysics.« less

Structure of Respiratory Syncytial Virus Fusion Glycoprotein in the Postfusion Conformation Reveals Preservation of Neutralizing Epitopes

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

McLellan, Jason S.; Yang, Yongping; Graham, Barney S.

2011-09-16

Respiratory syncytial virus (RSV) invades host cells via a type I fusion (F) glycoprotein that undergoes dramatic structural rearrangements during the fusion process. Neutralizing monoclonal antibodies, such as 101F, palivizumab, and motavizumab, target two major antigenic sites on the RSV F glycoprotein. The structures of these sites as peptide complexes with motavizumab and 101F have been previously determined, but a structure for the trimeric RSV F glycoprotein ectodomain has remained elusive. To address this issue, we undertook structural and biophysical studies on stable ectodomain constructs. Here, we present the 2.8-{angstrom} crystal structure of the trimeric RSV F ectodomain in itsmore » postfusion conformation. The structure revealed that the 101F and motavizumab epitopes are present in the postfusion state and that their conformations are similar to those observed in the antibody-bound peptide structures. Both antibodies bound the postfusion F glycoprotein with high affinity in surface plasmon resonance experiments. Modeling of the antibodies bound to the F glycoprotein predicts that the 101F epitope is larger than the linear peptide and restricted to a single protomer in the trimer, whereas motavizumab likely contacts residues on two protomers, indicating a quaternary epitope. Mechanistically, these results suggest that 101F and motavizumab can bind to multiple conformations of the fusion glycoprotein and can neutralize late in the entry process. The structural preservation of neutralizing epitopes in the postfusion state suggests that this conformation can elicit neutralizing antibodies and serve as a useful vaccine antigen.« less

Exotic lepton searches via bound state production at the LHC

NASA Astrophysics Data System (ADS)

Barrie, Neil D.; Kobakhidze, Archil; Liang, Shelley; Talia, Matthew; Wu, Lei

2018-06-01

Heavy long-lived multi-charged leptons (MCLs) are predicted by various new physics models. These hypothetical MCLs can form bound states, due to their high electric charges and long life times. In this work, we propose a novel strategy of searching for MCLs through their bound state productions and decays. By utilising LHC-8 TeV data in searching for resonances in the diphoton channel, we exclude the masses of isospin singlet heavy leptons with electric charge | q | ≥ 6 (in units of electron charge) lower than ∼1.2 TeV, which are much stronger than the corresponding 8 TeV LHC bounds from analysing the high ionisation and the long time-of-flight of MCLs. By utilising the current 13 TeV LHC diphoton channel measurements the bound can further exclude MCL masses up to ∼1.6 TeV for | q | ≥ 6. Also, we demonstrate that the conventional LHC limits from searching for MCLs produced via Drell-Yan processes can be enhanced by including the contribution of photon fusion processes.

Sudden death of distillability in qutrit-qutrit systems

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

Song Wei; Zhu Shiliang; Chen Lin

2009-07-15

We introduce the concept of distillability sudden death, i.e., free entangled states can evolve into nondistillable (bound entangled or separable) states in finite time under local noise. We describe the phenomenon through a specific model of local dephasing noise and compare the behavior of states in terms of the Bures fidelity. Then we propose a few methods to avoid distillability sudden death of states under (general) local dephasing noise so that free entangled states can be robust against decoherence. Moreover, we find that bound entangled states are unstable in the limit of infinite time.

In vivo assessment of a novel dacron surface with covalently bound recombinant hirudin.

PubMed

Wyers, M C; Phaneuf, M D; Rzucidlo, E M; Contreras, M A; LoGerfo, F W; Quist, W C

1999-01-01

Prosthetic arterial graft surfaces are relatively thrombogenic and fail to heal with a cellular neointima. The goal of this study was to characterize the in vivo antithrombin properties of a novel Dacron surface with covalently linked recombinant hirudin (rHir) implanted in a canine thoracic aorta with high flow and shear rates. rHir was bound to a knitted Dacron patch using crosslinker-modified bovine serum albumin (BSA) as a basecoat protein. BSA was first reacted with the heterobifunctional crosslinker, sulfo-SMCC. This BSA-SMCC complex was then bound to the carboxylic acid groups of hydrolyzed Dacron patches using the carbodiimide crosslinker, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. Iodinated, Traut's-modified rHir (125I-rHir-SH) was then reacted with the Dacron-BSA-SMCC surface, thereby covalently binding 125I-rHir. Graft segments were washed and sonicated to remove any nonspecifically bound 125I-rHir. Dacron-BSA-SMCC-S-125I-rHir patches (n = 5) and control Dacron-BSA patches (n = 5) were implanted in series in the thoracic aortas of canines. These patches were exposed to nonheparinized, arterial blood flow for 2 hours. Patches were explanted and assessed for 125I-rHir loss. Antithrombin activity of explanted 1-cm2 patch segments was evaluated using a chromogenic assay with 1, 5, 10, 15 units of added thrombin. Light microscopy was performed to qualitatively examine the pseudointima. Two animals were excluded from the study owing to excessive bleeding through the knitted 125I-rHir patch. Comparison of preoperative and postoperative 125I-rHir gamma counts revealed an overall decrease of 20+/-5.4% over the period studied. Explanted 125I-rHir patch segments were able to inhibit 1, 5, and 7 NIHU of thrombin, demonstrating retained antithrombin activity. Gross and microscopic examination of the control and test Dacron surfaces showed marked differences. Dacron surfaces with covalently bound 125I-rHir had no gross thrombus and a thin pseudointima of platelets and plasma proteins. In contrast, the control patches had a thick pseudointima composed of fibrin-rich thrombus. rHir, covalently bound to Dacron patches, maintains its biologic activity as well as prevents thrombus formation on the graft surface. This novel antithrombin coating, by modifying the blood/ graft interface, may improve both short- and long-term patency in small-diameter prosthetic arterial grafts and has applications with respect to other implantable or indwelling biomaterials.

Survey of four damage models for concrete.

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

Leelavanichkul, Seubpong; Brannon, Rebecca Moss

2009-08-01

Four conventional damage plasticity models for concrete, the Karagozian and Case model (K&C), the Riedel-Hiermaier-Thoma model (RHT), the Brannon-Fossum model (BF1), and the Continuous Surface Cap Model (CSCM) are compared. The K&C and RHT models have been used in commercial finite element programs many years, whereas the BF1 and CSCM models are relatively new. All four models are essentially isotropic plasticity models for which 'plasticity' is regarded as any form of inelasticity. All of the models support nonlinear elasticity, but with different formulations. All four models employ three shear strength surfaces. The 'yield surface' bounds an evolving set of elasticallymore » obtainable stress states. The 'limit surface' bounds stress states that can be reached by any means (elastic or plastic). To model softening, it is recognized that some stress states might be reached once, but, because of irreversible damage, might not be achievable again. In other words, softening is the process of collapse of the limit surface, ultimately down to a final 'residual surface' for fully failed material. The four models being compared differ in their softening evolution equations, as well as in their equations used to degrade the elastic stiffness. For all four models, the strength surfaces are cast in stress space. For all four models, it is recognized that scale effects are important for softening, but the models differ significantly in their approaches. The K&C documentation, for example, mentions that a particular material parameter affecting the damage evolution rate must be set by the user according to the mesh size to preserve energy to failure. Similarly, the BF1 model presumes that all material parameters are set to values appropriate to the scale of the element, and automated assignment of scale-appropriate values is available only through an enhanced implementation of BF1 (called BFS) that regards scale effects to be coupled to statistical variability of material properties. The RHT model appears to similarly support optional uncertainty and automated settings for scale-dependent material parameters. The K&C, RHT, and CSCM models support rate dependence by allowing the strength to be a function of strain rate, whereas the BF1 model uses Duvaut-Lion viscoplasticity theory to give a smoother prediction of transient effects. During softening, all four models require a certain amount of strain to develop before allowing significant damage accumulation. For the K&C, RHT, and CSCM models, the strain-to-failure is tied to fracture energy release, whereas a similar effect is achieved indirectly in the BF1 model by a time-based criterion that is tied to crack propagation speed.« less

Outdoor Education Academic Programs in the United States

ERIC Educational Resources Information Center

Bell, Brent J.; Seaman, Jayson; Trauntvein, Nate

2017-01-01

The growth of outdoor adventure programs developed, in part, from the Outward Bound movement in the 1970s (MacArthur, 1979; Outward Bound, 1968), which created a demand for specialized collegiate training. Since the inaugural conference on outdoor pursuits in higher education at Appalachian State University in 1974 (Smathers, 1974), approximately…

Influence of free surface curvature on the Pearson instability in Marangoni convection

NASA Astrophysics Data System (ADS)

Hu, W. R.

The Peason instability in a liquid layer bounded by a plate solid boundary with higher constant temperature and a plane free surface with lower constant temperatures in the microgravity environment has by extensively studied The free surface in the microgravity environment tends to be curved in general as a spherical shape and the plane configuration of free surface is a special case In the present paper a system of liquid layer bounded by a plat solid boundary with higher constant temperature and a curved free surface with lower non-uniform temperature is studied The temperature gradient on the free surface will induce the thermocapillary convection and the onset of Marangoni convection is coupled with the thermocapillary convection The thermocapillary convection induced by the temperature gradient on the curved free surface and its influence on the Marangoni convection are studied in the present paper

Influence of the Debye length on the interaction of a small molecule-modified Au nanoparticle with a surface-bound bioreceptor.

PubMed

Bukar, Natalia; Zhao, Sandy Shuo; Charbonneau, David M; Pelletier, Joelle N; Masson, Jean-Francois

2014-05-18

We report that a shorter Debye length and, as a consequence, decreased colloidal stability are required for the molecular interaction of folic acid-modified Au nanoparticles (Au NPs) to occur on a surface-bound receptor, human dihydrofolate reductase (hDHFR). The interaction measured using surface plasmon resonance (SPR) sensing was optimal in a phosphate buffer at pH 6 and ionic strength exceeding 300 mM. Under these conditions, the aggregation constant of the Au NPs was approximately 10(4) M(-1) s(-1) and the Debye length was below 1 nm, on the same length scale as the size of the folate anion (approximately 0.8 nm). Longer Debye lengths led to poorer SPR responses, revealing a reduced affinity of the folic acid-modified Au NPs for hDHFR. While high colloidal stability of Au NPs is desired in most applications, these conditions may hinder molecular interactions due to Debye lengths exceeding the size of the ligand and thus preventing close interactions with the surface-bound molecular receptor.

Residential surface soil guidance values applied worldwide to the original 2001 Stockholm Convention POP pesticides.

PubMed

Jennings, Aaron A; Li, Zijian

2015-09-01

Surface soil contamination is a worldwide problem. Many regulatory jurisdictions attempt to control human exposures with regulatory guidance values (RGVs) that specify a soil's maximum allowable concentration. Pesticides are important soil contaminants because of their intentional toxicity and widespread surface soil application. Worldwide, at least 174 regulatory jurisdictions from 54 United Nations member states have published more than 19,400 pesticide RGVs for at least 739 chemically unique pesticides. This manuscript examines the variability of the guidance values that are applied worldwide to the original 2001 Stockholm Convention persistent organic pollutants (POP) pesticides (Aldrin, Chlordane, DDT, Dieldrin, Endrin, Heptachlor, Mirex, and Toxaphene) for which at least 1667 RGVs have been promulgated. Results indicate that the spans of the RGVs applied to each of these pesticides vary from 6.1 orders of magnitude for Toxaphene to 10.0 orders of magnitude for Mirex. The distribution of values across these value spans resembles the distribution of lognormal random variables, but also contain non-random value clusters. Approximately 40% of all the POP RGVs fall within uncertainty bounds computed from the U.S. Environmental Protection Agency (USEPA) RGV cancer risk model. Another 22% of the values fall within uncertainty bounds computed from the USEPA's non-cancer risk model, but the cancer risk calculations yield the binding (lowest) value for all POP pesticides except Endrin. The results presented emphasize the continued need to rationalize the RGVs applied worldwide to important soil contaminants. Copyright © 2015 Elsevier Ltd. All rights reserved.

Stepwise Evolution of Nonliving to Living Chemical Systems

NASA Astrophysics Data System (ADS)

Lindahl, Paul A.

2004-08-01

Steps by which a nonliving chemical system could have transformed into a living system are described and discussed, assuming general features of Wächtershäuser's chemo-autotrophic surface theory of the origin of life. Environmental species such as CO2 and H2S are proposed to have reacted to form a quasi-steady state metal-bound intermediate (CH3-M) that slowly decayed into waste (CH4). Unpredictable dispersive reactions expanded the system to include surface-bound forms of the citric acid cycle intermediates (oxaloacetate --> citrate). Further reaction yielded an autocatalytic system in which raw materials are converted into the system at exponential rates. Combinatorial dispersive reactions that improved the performance of this system were automatically selected and incorporated into it. Systems evolved critical features of living systems (proteins, membranes, proteins, nucleic acids, etc.) using two related mechanisms called grafting and waste-conversion. Such living systems were transformed from less recognizable types (characterized by autocatalytic spreading, decentralization, poorly defined boundaries, etc.) into more recognizable ones (encapsulated by membranes, controlled by single-molecule genomes, etc.) that self-replicated by a cell division cycle and could evolve by the standard gene-based Darwinian mechanism. The resulting systems are viewed as having an autocatalytic network composed of three linked autocatalytic subreactions.

Delivery of drugs bound to erythrocytes: new avenues for an old intravascular carrier

PubMed Central

Villa, Carlos H; Pan, Daniel C; Zaitsev, Sergei; Cines, Douglas B; Siegel, Donald L; Muzykantov, Vladimir R

2015-01-01

For several decades, researchers have used erythrocytes for drug delivery of a wide variety of therapeutics in order to improve their pharmacokinetics, biodistribution, controlled release and pharmacodynamics. Approaches include encapsulation of drugs within erythrocytes, as well as coupling of drugs onto the red cell surface. This review focuses on the latter approach, and examines the delivery of red blood cell (RBC)-surface-bound anti-inflammatory, anti-thrombotic and anti-microbial agents, as well as RBC carriage of nanoparticles. Herein, we discuss the progress that has been made in surface loading approaches, and address in depth the issues relevant to surface loading of RBC, including intrinsic features of erythrocyte membranes, immune considerations, potential surface targets and techniques for the production of affinity ligands. PMID:26228773

Self-assembly of acetate adsorbates drives atomic rearrangement on the Au(110) surface

DOE PAGES

Hiebel, Fanny; Shong, Bonggeun; Chen, Wei; ...

2016-10-12

Weak inter-adsorbate interactions are shown to play a crucial role in determining surface structure, with major implications for its catalytic reactivity. This is exemplified here in the case of acetate bound to Au(110), where the small extra energy of the van der Waals interactions among the surface-bound groups drives massive restructuring of the underlying Au. Acetate is a key intermediate in electro-oxidation of CO 2 and a poison in partial oxidation reactions. Metal atom migration originates at surface defects and is likely facilitated by weakened Au–Au interactions due to bonding with the acetate. Even though the acetate is a relativelymore » small molecule, weak intermolecular interaction provides the energy required for molecular self-assembly and reorganization of the metal surface.« less

Self-assembly of acetate adsorbates drives atomic rearrangement on the Au(110) surface

PubMed Central

Hiebel, Fanny; Shong, Bonggeun; Chen, Wei; Madix, Robert J.; Kaxiras, Efthimios; Friend, Cynthia M.

2016-01-01

Weak inter-adsorbate interactions are shown to play a crucial role in determining surface structure, with major implications for its catalytic reactivity. This is exemplified here in the case of acetate bound to Au(110), where the small extra energy of the van der Waals interactions among the surface-bound groups drives massive restructuring of the underlying Au. Acetate is a key intermediate in electro-oxidation of CO2 and a poison in partial oxidation reactions. Metal atom migration originates at surface defects and is likely facilitated by weakened Au–Au interactions due to bonding with the acetate. Even though the acetate is a relatively small molecule, weak intermolecular interaction provides the energy required for molecular self-assembly and reorganization of the metal surface. PMID:27731407

Native Liquid Extraction Surface Analysis Mass Spectrometry: Analysis of Noncovalent Protein Complexes Directly from Dried Substrates

NASA Astrophysics Data System (ADS)

Martin, Nicholas J.; Griffiths, Rian L.; Edwards, Rebecca L.; Cooper, Helen J.

2015-08-01

Liquid extraction surface analysis (LESA) mass spectrometry is a promising tool for the analysis of intact proteins from biological substrates. Here, we demonstrate native LESA mass spectrometry of noncovalent protein complexes of myoglobin and hemoglobin from a range of surfaces. Holomyoglobin, in which apomyoglobin is noncovalently bound to the prosthetic heme group, was observed following LESA mass spectrometry of myoglobin dried onto glass and polyvinylidene fluoride surfaces. Tetrameric hemoglobin [(αβ)2 4H] was observed following LESA mass spectrometry of hemoglobin dried onto glass and polyvinylidene fluoride (PVDF) surfaces, and from dried blood spots (DBS) on filter paper. Heme-bound dimers and monomers were also observed. The `contact' LESA approach was particularly suitable for the analysis of hemoglobin tetramers from DBS.

Nearly extremal apparent horizons in simulations of merging black holes

NASA Astrophysics Data System (ADS)

Lovelace, Geoffrey; Scheel, Mark A.; Owen, Robert; Giesler, Matthew; Katebi, Reza; Szilágyi, Béla; Chu, Tony; Demos, Nicholas; Hemberger, Daniel A.; Kidder, Lawrence E.; Pfeiffer, Harald P.; Afshari, Nousha

2015-03-01

The spin angular momentum S of an isolated Kerr black hole is bounded by the surface area A of its apparent horizon: 8π S≤slant A, with equality for extremal black holes. In this paper, we explore the extremality of individual and common apparent horizons for merging, rapidly spinning binary black holes. We consider simulations of merging black holes with equal masses M and initial spin angular momenta aligned with the orbital angular momentum, including new simulations with spin magnitudes up to S/{{M}2}=0.994. We measure the area and (using approximate Killing vectors) the spin on the individual and common apparent horizons, finding that the inequality 8π S\\lt A is satisfied in all cases but is very close to equality on the common apparent horizon at the instant it first appears. We also evaluate the Booth-Fairhurst extremality, whose value for a given apparent horizon depends on the scaling of the horizon’s null normal vectors. In particular, we introduce a gauge-invariant lower bound on the extremality by computing the smallest value that Booth and Fairhurst’s extremality parameter can take for any scaling. Using this lower bound, we conclude that the common horizons are at least moderately close to extremal just after they appear. Finally, following Lovelace et al (2008 Phys. Rev. D 78 084017), we construct quasiequilibrium binary-black hole initial data with ‘overspun’ marginally trapped surfaces with 8π S\\gt A. We show that the overspun surfaces are indeed superextremal: our lower bound on their Booth-Fairhurst extremality exceeds unity. However, we confirm that these superextremal surfaces are always surrounded by marginally outer trapped surfaces (i.e., by apparent horizons) with 8π S\\lt A. The extremality lower bound on the enclosing apparent horizon is always less than unity but can exceed the value for an extremal Kerr black hole.

Plasma and serum serotonin concentrations and surface-bound platelet serotonin expression in Cavalier King Charles Spaniels with myxomatous mitral valve disease.

PubMed

Cremer, Signe E; Kristensen, Annemarie T; Reimann, Maria J; Eriksen, Nynne B; Petersen, Stine F; Marschner, Clara B; Tarnow, Inge; Oyama, Mark A; Olsen, Lisbeth H

2015-06-01

To investigate serum and plasma serotonin concentrations, percentage of serotonin-positive platelets, level of surface-bound platelet serotonin expression (mean fluorescence intensity [MFI]), and platelet activation (CD62 expression) in platelet-rich plasma from Cavalier King Charles Spaniels with myxomatous mitral valve disease (MMVD). Healthy dogs (n = 15) and dogs with mild MMVD (18), moderate-severe MMVD (19), or severe MMVD with congestive heart failure (CHF; 10). Blood samples were collected from each dog. Serum and plasma serotonin concentrations were measured with an ELISA, and surface-bound platelet serotonin expression and platelet activation were determined by flow cytometry. Dogs with mild MMVD had higher median serum (746 ng/mL) and plasma (33.3 ng/mL) serotonin concentrations, compared with MMVD-affected dogs with CHF (388 ng/mL and 9.9 ng/mL, respectively), but no other group differences were found. Among disease groups, no differences in surface-bound serotonin expression or platelet activation were found. Thrombocytopenic dogs had lower serum serotonin concentration (482 ng/mL) than nonthrombocytopenic dogs (731 ng/mL). In 26 dogs, a flow cytometry scatterplot subpopulation (FSSP) of platelets was identified; dogs with an FSSP had a higher percentage of serotonin-positive platelets (11.0%), higher level of surface-bound serotonin expression (MFI, 32,068), and higher platelet activation (MFI, 2,363) than did dogs without an FSSP (5.7%, 1,230, and 1,165, respectively). An FSSP was present in 93.8% of thrombocytopenic dogs and in 29.5% of nonthrombocytopenic dogs. A substantive influence of circulating serotonin on MMVD stages prior to CHF development in Cavalier King Charles Spaniels was not supported by the study findings. An FSSP of highly activated platelets with pronounced serotonin binding was strongly associated with thrombocytopenia but not MMVD.

Exact Solution of a Two-Species Quantum Dimer Model for Pseudogap Metals

NASA Astrophysics Data System (ADS)

Feldmeier, Johannes; Huber, Sebastian; Punk, Matthias

2018-05-01

We present an exact ground state solution of a quantum dimer model introduced by Punk, Allais, and Sachdev [Quantum dimer model for the pseudogap metal, Proc. Natl. Acad. Sci. U.S.A. 112, 9552 (2015)., 10.1073/pnas.1512206112], which features ordinary bosonic spin-singlet dimers as well as fermionic dimers that can be viewed as bound states of spinons and holons in a hole-doped resonating valence bond liquid. Interestingly, this model captures several essential properties of the metallic pseudogap phase in high-Tc cuprate superconductors. We identify a line in parameter space where the exact ground state wave functions can be constructed at an arbitrary density of fermionic dimers. At this exactly solvable line the ground state has a huge degeneracy, which can be interpreted as a flat band of fermionic excitations. Perturbing around the exactly solvable line, this degeneracy is lifted and the ground state is a fractionalized Fermi liquid with a small pocket Fermi surface in the low doping limit.

Effect of temperature on residual force enhancement in single skeletal muscle fibers.

PubMed

Lee, Eun-Jeong; Herzog, Walter

2008-08-28

It is well accepted that the steady-state isometric force following active stretching of a muscle is greater than the steady-state isometric force obtained in a purely isometric contraction at the same length. This property of skeletal muscle has been called residual force enhancement (FE). Despite decades of research the mechanisms responsible for FE have remained largely unknown. Based on previous studies showing increases in FE in fibers in which cross-bridges were biased towards weakly bound states, we hypothesized that FE might be associated with a stretch-induced facilitation of transitioning from weakly to strongly bound cross-bridges. In order to test this hypothesis, single fibers (n=11) from the lumbrical muscles of frog (Rana pipiens) were used to determine FE at temperatures of 7 and 20 degrees C. At the cold temperature, cross-bridges are biased towards weakly bound states, therefore we expected FE to be greater at 7 degrees C compared to 20 degrees C. The average FE was significantly greater at 7 degrees C (11.5+/-1.1%) than at 20 degrees C (7.8+/-1.0%), as expected. The enhancement of force/stiffness was also significantly greater at the low (13.3+/-1.4%) compared to the high temperature (5.6+/-1.7%), indicating an increased conversion from weakly to strongly bound cross-bridges at the low temperature. We conclude from the results of this study that muscle preparations that are biased towards weakly bound cross-bridge states show increased FE for given stretch conditions, thereby supporting the idea that FE might be caused, in part, by a stretch-induced facilitation of the conversion of weakly to strongly bound cross-bridges.

Exact results for the finite time thermodynamic uncertainty relation

NASA Astrophysics Data System (ADS)

Manikandan, Sreekanth K.; Krishnamurthy, Supriya

2018-03-01

We obtain exact results for the recently discovered finite-time thermodynamic uncertainty relation, for the dissipated work W d , in a stochastically driven system with non-Gaussian work statistics, both in the steady state and transient regimes, by obtaining exact expressions for any moment of W d at arbitrary times. The uncertainty function (the Fano factor of W d ) is bounded from below by 2k_BT as expected, for all times τ, in both steady state and transient regimes. The lower bound is reached at τ=0 as well as when certain system parameters vanish (corresponding to an equilibrium state). Surprisingly, we find that the uncertainty function also reaches a constant value at large τ for all the cases we have looked at. For a system starting and remaining in steady state, the uncertainty function increases monotonically, as a function of τ as well as other system parameters, implying that the large τ value is also an upper bound. For the same system in the transient regime, however, we find that the uncertainty function can have a local minimum at an accessible time τm , for a range of parameter values. The large τ value for the uncertainty function is hence not a bound in this case. The non-monotonicity suggests, rather counter-intuitively, that there might be an optimal time for the working of microscopic machines, as well as an optimal configuration in the phase space of parameter values. Our solutions show that the ratios of higher moments of the dissipated work are also bounded from below by 2k_BT . For another model, also solvable by our methods, which never reaches a steady state, the uncertainty function, is in some cases, bounded from below by a value less than 2k_BT .

Influence of the Envelope gp120 Phe 43 Cavity on HIV-1 Sensitivity to Antibody-Dependent Cell-Mediated Cytotoxicity Responses

PubMed Central

Prévost, Jérémie; Zoubchenok, Daria; Richard, Jonathan; Veillette, Maxime; Pacheco, Beatriz; Coutu, Mathieu; Brassard, Nathalie; Parsons, Matthew S.; Ruxrungtham, Kiat; Bunupuradah, Torsak; Tovanabutra, Sodsai; Hwang, Kwan-Ki; Moody, M. Anthony; Haynes, Barton F.; Bonsignori, Mattia; Sodroski, Joseph; Kaufmann, Daniel E.; Shaw, George M.; Chenine, Agnès L.

2017-01-01

ABSTRACT HIV-1-infected cells presenting envelope glycoproteins (Env) in the CD4-bound conformation on their surface are preferentially targeted by antibody-dependent cellular-mediated cytotoxicity (ADCC). HIV-1 has evolved sophisticated mechanisms to avoid the exposure of Env ADCC epitopes by downregulating CD4 and by limiting the overall amount of Env on the cell surface. In HIV-1, substitution of large residues such as histidine or tryptophan for serine 375 (S375H/W) in the gp120 Phe 43 cavity, where Phe 43 of CD4 contacts gp120, results in the spontaneous sampling of an Env conformation closer to the CD4-bound state. While residue S375 is well conserved in the majority of group M HIV-1 isolates, CRF01_AE strains have a naturally occurring histidine at this position (H375). Interestingly, CRF01_AE is the predominant circulating strain in Thailand, where the RV144 trial took place. In this trial, which resulted in a modest degree of protection, ADCC responses were identified as being part of the correlate of protection. Here we investigate the influence of the Phe 43 cavity on ADCC responses. Filling this cavity with a histidine or tryptophan residue in Env with a natural serine residue at this position (S375H/W) increased the susceptibility of HIV-1-infected cells to ADCC. Conversely, the replacement of His 375 by a serine residue (H375S) within HIV-1 CRF01_AE decreased the efficiency of the ADCC response. Our results raise the intriguing possibility that the presence of His 375 in the circulating strain where the RV144 trial was held contributed to the observed vaccine efficacy. IMPORTANCE HIV-1-infected cells presenting Env in the CD4-bound conformation on their surface are preferentially targeted by ADCC mediated by HIV-positive (HIV+) sera. Here we show that the gp120 Phe 43 cavity modulates the propensity of Env to sample this conformation and therefore affects the susceptibility of infected cells to ADCC. CRF01_AE HIV-1 strains have an unusual Phe 43 cavity-filling His 375 residue, which increases the propensity of Env to sample the CD4-bound conformation, thereby increasing susceptibility to ADCC. PMID:28100618

Unidirectional edge modes launched by surface fluctuation in magnetic metamaterials

NASA Astrophysics Data System (ADS)

Chen, Huajin; Luo, Youzhu; Liang, Chenghua; Li, Zhenglin; Liu, Shiyang; Lin, Zhifang

2018-03-01

We demonstrate theoretically that the surface fluctuation can be used to launch the unidirectional electromagnetic edge mode for a Gaussian beam incident normal to the magnetic metamaterials (MMs) composed of an array of ferrite rods with the uppermost layer introduced position or size fluctuation in the coupling region. Such an edge mode is solely allowed to propagate in one direction due to the time-reversal symmetry breaking in MMs under the exertion of an external magnetic field, and it is substantially enhanced by the magnetic surface plasmon resonance. The nonreciprocal excitation of the edge states can also be understood by examining the scattering amplitudes of different partial waves, which indicate that the 1st order of the angular momentum channel plays a crucial role in realizing the nonreciprocity. The present research might be significant for the implementation of unidirectional absorption and the reexamination of bound states in the continuum in the context of MMs. In addition, the unique optical property can be exploited to design electromagnetic waveguide devices, such as one-way waveguide and wave bender, which are strongly robust against the obstacles placed in the channel of designed devices, facilitating to realize optical integrated circuits.

Mesoscopic structure formation in condensed matter due to vacuum fluctuations

NASA Astrophysics Data System (ADS)

Sen, Siddhartha; Gupta, Kumar S.; Coey, J. M. D.

2015-10-01

An observable influence of zero-point fluctuations of the vacuum electromagnetic field on bound electrons is well known in the hydrogen atom, where it produces the Lamb shift. Here, we adapt an approach used to explain the Lamb shift in terms of a slight expansion of the orbits due to interaction with the zero-point field and apply it to assemblies of N electrons that are modeled as independent atomically bound two-level systems. The effect is to stabilize a collective ground-state energy, which leads to a prediction of novel effects at room temperature for quasi-two-dimensional systems over a range of parameters in the model, namely, N , the two-level excitation energy ℏ ω and the ionization energy ℏ ω +ɛ . Some mesoscopic systems where these effects may be observable include water sheaths on protein or DNA, surfaces of gaseous nanobubbles, and the magnetic response of inhomogeneous, electronically dilute oxides. No such effects are envisaged for uniform three-dimensional systems.

A Comparison of the Bounded Derivative and the Normal Mode Initialization Methods Using Real Data

NASA Technical Reports Server (NTRS)

Semazzi, F. H. M.; Navon, I. M.

1985-01-01

Browning et al. (1980) proposed an initialization method called the bounded derivative method (BDI). They used analytical data to test the new method. Kasahara (1982) theoretically demonstrated the equivalence between BDI and the well known nonlinear normal mode initialization method (NMI). The purposes of this study are the extension of the application of BDI to real data and comparison with NMI. The unbalanced initial state (UBD) is data of January, 1979 OOZ which were interpolated from the adjacent sigma levels of the GLAS GCM to the 300 mb surface. The global barotropic model described by Takacs and Balgovind (1983) is used. Orographic forcing is explicitly included in the model. Many comparisons are performed between various quantities. However, we only present a comparison of the time evolution at two grid points A(50 S, 90 E) and B(10 S, 20 E) which represent low and middle latitude locations. To facilitate a more complete comparison an initialization experiment based on the classical balance equation (CBE) was also included.

Haemoglobin scavenging after subarachnoid haemorrhage.

PubMed

Durnford, A; Dunbar, J; Galea, J; Bulters, D; Nicoll, J A R; Boche, D; Galea, I

2015-01-01

Rapid and effective clearance of cell-free haemoglobin after subarachnoid haemorrhage (SAH) is important to prevent vasospasm and neurotoxicity and improve long-term outcome. Haemoglobin is avidly bound by haptoglobin, and the complex is cleared by CD163 expressed on the membrane surface of macrophages. We studied the kinetics of haemoglobin and haptoglobin in cerebrospinal fluid after SAH. We show that haemoglobin levels rise gradually after SAH. Haptoglobin levels rise acutely with aneurysmal rupture as a result of injection of blood into the subarachnoid space. Although levels decline as haemoglobin scavenging occurs, complete depletion of haptoglobin does not occur and levels start rising again, indicating saturation of CD163 sites available for haptoglobin-haemoglobin clearance. In a preliminary neuropathological study we demonstrate that meningeal CD163 expression is upregulated after SAH, in keeping with a proinflammatory state. However, loss of CD163 occurs in meningeal areas with overlying blood compared with areas without overlying blood. Becauses ADAM17 is the enzyme responsible for shedding membrane-bound CD163, its inhibition may be a potential therapeutic strategy after SAH.

Majorana bound states from exceptional points in non-topological superconductors

PubMed Central

San-Jose, Pablo; Cayao, Jorge; Prada, Elsa; Aguado, Ramón

2016-01-01

Recent experimental efforts towards the detection of Majorana bound states have focused on creating the conditions for topological superconductivity. Here we demonstrate an alternative route, which achieves fully localised zero-energy Majorana bound states when a topologically trivial superconductor is strongly coupled to a helical normal region. Such a junction can be experimentally realised by e.g. proximitizing a finite section of a nanowire with spin-orbit coupling, and combining electrostatic depletion and a Zeeman field to drive the non-proximitized (normal) portion into a helical phase. Majorana zero modes emerge in such an open system without fine-tuning as a result of charge-conjugation symmetry, and can be ultimately linked to the existence of ‘exceptional points’ (EPs) in parameter space, where two quasibound Andreev levels bifurcate into two quasibound Majorana zero modes. After the EP, one of the latter becomes non-decaying as the junction approaches perfect Andreev reflection, thus resulting in a Majorana dark state (MDS) localised at the NS junction. We show that MDSs exhibit the full range of properties associated to conventional closed-system Majorana bound states (zero-energy, self-conjugation, 4π-Josephson effect and non-Abelian braiding statistics), while not requiring topological superconductivity. PMID:26865011

Pentaquarks with hidden charm as hadroquarkonia

NASA Astrophysics Data System (ADS)

Eides, Michael I.; Petrov, Victor Yu.; Polyakov, Maxim V.

2018-01-01

We consider hidden charm pentaquarks as hadroquarkonium states in a QCD inspired approach. Pentaquarks arise naturally as bound states of quarkonia excitations and ordinary baryons. The LHCb P_c(4450) pentaquark is interpreted as a ψ '-nucleon bound state with spin-parity J^P=3/2^-. The partial decay width Γ (P_c(4450)→ J/ψ +N)≈ 11 MeV is calculated and turned out to be in agreement with the experimental data for P_c(4450). The P_c(4450) pentaquark is predicted to be a member of one of the two almost degenerate hidden-charm baryon octets with spin-parities JP=1/2^-,3/2^-. The masses and decay widths of the octet pentaquarks are calculated. The widths are small and comparable with the width of the P_c(4450) pentaquark, and the masses of the octet pentaquarks satisfy the Gell-Mann-Okubo relation. Interpretation of pentaquarks as loosely bound Σ_c\\bar{D}^* and Σ_c^*\\bar{D}^* deuteronlike states is also considered. We determine quantum numbers of these bound states and calculate their masses in the one-pion exchange scenario. The hadroquarkonium and molecular approaches to exotic hadrons are compared and the relative advantages and drawbacks of each approach are discussed.

Steric Pressure among Membrane-Bound Polymers Opposes Lipid Phase Separation.

PubMed

Imam, Zachary I; Kenyon, Laura E; Carrillo, Adelita; Espinoza, Isai; Nagib, Fatema; Stachowiak, Jeanne C

2016-04-19

Lipid rafts are thought to be key organizers of membrane-protein complexes in cells. Many proteins that interact with rafts have bulky polymeric components such as intrinsically disordered protein domains and polysaccharide chains. Therefore, understanding the interaction between membrane domains and membrane-bound polymers provides insights into the roles rafts play in cells. Multiple studies have demonstrated that high concentrations of membrane-bound polymeric domains create significant lateral steric pressure at membrane surfaces. Furthermore, our recent work has shown that lateral steric pressure at membrane surfaces opposes the assembly of membrane domains. Building on these findings, here we report that membrane-bound polymers are potent suppressors of membrane phase separation, which can destabilize lipid domains with substantially greater efficiency than globular domains such as membrane-bound proteins. Specifically, we created giant vesicles with a ternary lipid composition, which separated into coexisting liquid ordered and disordered phases. Lipids with saturated tails and poly(ethylene glycol) (PEG) chains conjugated to their head groups were included at increasing molar concentrations. When these lipids were sparse on the membrane surface they partitioned to the liquid ordered phase. However, as they became more concentrated, the fraction of GUVs that were phase-separated decreased dramatically, ultimately yielding a population of homogeneous membrane vesicles. Experiments and physical modeling using compositions of increasing PEG molecular weight and lipid miscibility phase transition temperature demonstrate that longer polymers are the most efficient suppressors of membrane phase separation when the energetic barrier to lipid mixing is low. In contrast, as the miscibility transition temperature increases, longer polymers are more readily driven out of domains by the increased steric pressure. Therefore, the concentration of shorter polymers required to suppress phase separation decreases relative to longer polymers. Collectively, our results demonstrate that crowded, membrane-bound polymers are highly efficient suppressors of phase separation and suggest that the ability of lipid domains to resist steric pressure depends on both their lipid composition and the size and concentration of the membrane-bound polymers they incorporate.

Quantum Dynamical Applications of Salem's Theorem

NASA Astrophysics Data System (ADS)

Damanik, David; Del Rio, Rafael

2009-07-01

We consider the survival probability of a state that evolves according to the Schrödinger dynamics generated by a self-adjoint operator H. We deduce from a classical result of Salem that upper bounds for the Hausdorff dimension of a set supporting the spectral measure associated with the initial state imply lower bounds on a subsequence of time scales for the survival probability. This general phenomenon is illustrated with applications to the Fibonacci operator and the critical almost Mathieu operator. In particular, this gives the first quantitative dynamical bound for the critical almost Mathieu operator.

Do Reuss and Voigt Bounds Really Bound in High-Pressure Rheology Experiments?

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

Chen,J.; Li, L.; Yu, T.

2006-01-01

Energy dispersive synchrotron x-ray diffraction is carried out to measure differential lattice strains in polycrystalline Fe{sub 2}SiO{sub 4} (fayalite) and MgO samples using a multi-element solid state detector during high-pressure deformation. The theory of elastic modeling with Reuss (iso-stress) and Voigt (iso-strain) bounds is used to evaluate the aggregate stress and weight parameter, {alpha} (0{le}{alpha}{le}1), of the two bounds. Results under the elastic assumption quantitatively demonstrate that a highly stressed sample in high-pressure experiments reasonably approximates to an iso-stress state. However, when the sample is plastically deformed, the Reuss and Voigt bounds are no longer valid ({alpha} becomes beyond 1).more » Instead, if plastic slip systems of the sample are known (e.g. in the case of MgO), the aggregate property can be modeled using a visco-plastic self-consistent theory.« less