Soliton-impurity interaction in two Ablowitz-Ladik chains with different coupling

NASA Astrophysics Data System (ADS)

Kamburova, R. S.; Primatarowa, M. T.

2014-12-01

The interaction of solitons with point defects in a system of coupled Ablowitz- Ladik (AL) chains is studied numerically. The system is a discrete analog of coupled nonlinear Schrodinger equations. Two types of interchain coupling are investigated: one which admits reduction of the system to the standard integrable AL model (dispersive coupling) and one which couples opposite sites of the chains and does not admit reduction to the AL model (nondispersive coupling). The action of the two coupling types is additive and they can compensate each other in some cases. We have obtained that the single-peak bound soliton-defect solution (attractive impurity) is stable against perturbations, while the double-peak bound soliton-defect solution (repulsive impurity) is unstable and can be easily destroyed. Linear point defects do not influence the period of energy transfer and it is close to the period for the homogeneous case.

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

Xu, J.; Chen, T; Yang, C

Low-dimensional nanoparticles have a strong ability to induce the crystallization of polymer matrices. One-dimensional carbon nanotubes (CNTs) and two-dimensional graphene nanosheets (GNSs), both of which are both carbon-based nanoparticles, provide a good opportunity to investigate the effects of differently dimensional nanoparticles on the crystallization behavior of a polymer. For this purpose, respective nanocomposites of CNTs and GNSs with poly(L-lactide) (PLLA) as matrix were prepared by solution coagulation. Time-resolved Fourier-transform infrared spectroscopy (FTIR) and synchrotron wide-angle X-ray diffraction (WAXD) were performed to probe chain conformational changes and to determine the crystallization kinetics during the isothermal crystallization of the PLLA nanocomposites andmore » neat PLLA, especially in the early stages. Both CNTs and GNSs could serve as nucleating agents in accelerating the crystallization kinetics of PLLA; however, the ability of CNTs to induce crystallization was stronger than that of GNSs. On increasing the content of CNTs from 0.05 to 0.1 wt %, the induction period was shortened and the crystallization rate was enhanced, but the reverse situation was found for GNSs nanocomposites. In the case of neat PLLA, -CH{sub 3} interchain interactions preceded -(COC + CH{sub 3}) interchain interactions during the crystallization. Conversely, in the CNTs and GNSs nanocomposites, the conformational ordering began with -(COC + CH{sub 3}) interchain interactions, which resulted directly in a reduced induction period. Interchain interactions of this type could be explained in terms of surface-induced conformational order (SICO). Finally, the effect of the dimensionality of the nanoparticles on the crystallization behavior of PLLA is discussed.« less

Magnetic anisotropy in the frustrated spin-chain compound β - TeVO 4

DOE PAGES

Weickert, F.; Harrison, Neil; Scott, Brian Lindley; ...

2016-08-01

In this paper, isotropic and anisotropic magnetic behavior of the frustrated spin-chain compound β-TeVO 4 is reported. Three magnetic transitions observed in zero magnetic field are tracked in fields applied along different crystallographic directions using magnetization, heat capacity, and magnetostriction measurements. Qualitatively different temperature-field diagrams are obtained below 10 T for the field applied along a or b and along c, respectively. In contrast, a nearly isotropic high-field phase emerges above 18 T and persists up to the saturation that occurs around 22.5 T. Upon cooling in low fields, the transitions at T N1 and T N2 toward the spin-density-wavemore » and stripe phases are of the second order, whereas the transition at T N3 toward the helical state is of the first order and entails a lattice component. Our microscopic analysis identifies frustrated J 1-J 2 spin chains with a sizable antiferromagnetic interchain coupling in the bc plane and ferromagnetic couplings along the a direction. The competition between these ferromagnetic interchain couplings and the helical order within the chain underlies the incommensurate order along the a direction, as observed experimentally. While a helical state is triggered by the competition between J 1 and J 2 within the chain, the plane of the helix is not uniquely defined because of competing magnetic anisotropies. Finally, using high-resolution synchrotron diffraction and 125Te nuclear magnetic resonance, we also demonstrate that the crystal structure of β-TeVO 4 does not change down to 10 K, and the orbital state of V 4+ is preserved.« less

Template-directed atomically precise self-organization of perfectly ordered parallel cerium silicide nanowire arrays on Si(110)-16 × 2 surfaces.

PubMed

Hong, Ie-Hong; Liao, Yung-Cheng; Tsai, Yung-Feng

2013-11-05

The perfectly ordered parallel arrays of periodic Ce silicide nanowires can self-organize with atomic precision on single-domain Si(110)-16 × 2 surfaces. The growth evolution of self-ordered parallel Ce silicide nanowire arrays is investigated over a broad range of Ce coverages on single-domain Si(110)-16 × 2 surfaces by scanning tunneling microscopy (STM). Three different types of well-ordered parallel arrays, consisting of uniformly spaced and atomically identical Ce silicide nanowires, are self-organized through the heteroepitaxial growth of Ce silicides on a long-range grating-like 16 × 2 reconstruction at the deposition of various Ce coverages. Each atomically precise Ce silicide nanowire consists of a bundle of chains and rows with different atomic structures. The atomic-resolution dual-polarity STM images reveal that the interchain coupling leads to the formation of the registry-aligned chain bundles within individual Ce silicide nanowire. The nanowire width and the interchain coupling can be adjusted systematically by varying the Ce coverage on a Si(110) surface. This natural template-directed self-organization of perfectly regular parallel nanowire arrays allows for the precise control of the feature size and positions within ±0.2 nm over a large area. Thus, it is a promising route to produce parallel nanowire arrays in a straightforward, low-cost, high-throughput process.

Template-directed atomically precise self-organization of perfectly ordered parallel cerium silicide nanowire arrays on Si(110)-16 × 2 surfaces

PubMed Central

2013-01-01

The perfectly ordered parallel arrays of periodic Ce silicide nanowires can self-organize with atomic precision on single-domain Si(110)-16 × 2 surfaces. The growth evolution of self-ordered parallel Ce silicide nanowire arrays is investigated over a broad range of Ce coverages on single-domain Si(110)-16 × 2 surfaces by scanning tunneling microscopy (STM). Three different types of well-ordered parallel arrays, consisting of uniformly spaced and atomically identical Ce silicide nanowires, are self-organized through the heteroepitaxial growth of Ce silicides on a long-range grating-like 16 × 2 reconstruction at the deposition of various Ce coverages. Each atomically precise Ce silicide nanowire consists of a bundle of chains and rows with different atomic structures. The atomic-resolution dual-polarity STM images reveal that the interchain coupling leads to the formation of the registry-aligned chain bundles within individual Ce silicide nanowire. The nanowire width and the interchain coupling can be adjusted systematically by varying the Ce coverage on a Si(110) surface. This natural template-directed self-organization of perfectly regular parallel nanowire arrays allows for the precise control of the feature size and positions within ±0.2 nm over a large area. Thus, it is a promising route to produce parallel nanowire arrays in a straightforward, low-cost, high-throughput process. PMID:24188092

Identifying hydrodynamic interaction effects in tethered polymers in uniform flow.

PubMed

Kienle, Diego; Rzehak, Roland; Zimmermann, Walter

2011-06-01

Using Brownian dynamics simulations, we investigate how hydrodynamic interaction (HI) affects the behavior of tethered polymers in uniform flow. While it is expected that the HI within the polymer will lead to a dependency of the polymer's drag coefficient on the flow velocity, the interchain HI causes additional screening effects. For the case of two polymers in uniform flow with their tether points a finite distance apart, it is shown that the interchain HI not only causes a further reduction of the drag per polymer with decreasing distance between the tether points but simultaneously induces a polymer-polymer attraction as well. This attraction exhibits a characteristic maximum at intermediate flow velocities when the drag forces are of the order of the entropic forces. The effects uniquely attributed to the presence of HI can be verified experimentally.

Exciton intrachain transport induced by interchain packing configurations in conjugated polymers.

PubMed

Meng, Ruixuan; Gao, Kun; Zhang, Gaiyan; Han, Shixuan; Yang, Fujiang; Li, Yuan; Xie, Shijie

2015-07-28

Based on a tight binding model combined with a nonadiabatic dynamics approach, we theoretically investigate the exciton intrachain transport in conjugated polymers with different interchain packing configurations. We construct two different interchain packing configurations, i.e. linear and exponential forms, and simulate the dynamical processes of the exciton transport in these systems. We find that, in both cases, there exists a distribution of driving force for exciton transport, which stems from the gradient of the exciton creation energy along the chains. This finding enriches the picture of exciton transport in polymers and provides a new idea to improve the exciton transport length in polymeric photovoltaic devices.

Intrachain versus interchain electron transport in poly(fluorene-alt-benzothiadiazole): a quantum-chemical insight.

PubMed

Van Vooren, Antoine; Kim, Ji-Seon; Cornil, Jérôme

2008-05-16

Poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) [F8BT], displays very different charge-transport properties for holes versus electrons when comparing annealed and pristine thin films and transport parallel (intrachain) and perpendicular (interchain) to the polymer axes. The present theoretical contribution focuses on the electron-transport properties of F8BT chains and compares the efficiency of intrachain versus interchain transport in the hopping regime. The theoretical results rationalize significantly lowered electron mobility in annealed F8BT thin films and the smaller mobility anisotropy (mu( parallel)/mu( perpendicular)) measured for electrons in aligned films (i.e. 5-7 compared to 10-15 for holes).

Electrical and thermal transport in the quasiatomic limit of coupled Luttinger liquids

NASA Astrophysics Data System (ADS)

Szasz, Aaron; Ilan, Roni; Moore, Joel E.

2017-02-01

We introduce a new model for quasi-one-dimensional materials, motivated by intriguing but not yet well-understood experiments that have shown two-dimensional polymer films to be promising materials for thermoelectric devices. We consider a two-dimensional material consisting of many one-dimensional systems, each treated as a Luttinger liquid, with weak (incoherent) coupling between them. This approximation of strong interactions within each one-dimensional chain and weak coupling between them is the "quasiatomic limit." We find integral expressions for the (interchain) transport coefficients, including the electrical and thermal conductivities and the thermopower, and we extract their power law dependencies on temperature. Luttinger liquid physics is manifested in a violation of the Wiedemann-Franz law; the Lorenz number is larger than the Fermi liquid value by a factor between γ2 and γ4, where γ ≥1 is a measure of the electron-electron interaction strength in the system.

Coupled antiferromagnetic spin- 1 2 chains in green dioptase Cu 6 [ Si 6 O 18 ] · 6 H 2 O

DOE PAGES

Podlesnyak, Andrey A; Larry M. Anovitz; Kolesnikov, Alexander I; ...

2016-02-01

Inmore » this paper, we report inelastic neutron scattering measurements of the magnetic excitations of green dioptase Cu 6[Si 6O 18]∙6H 2O. The observed spectrum contains two magnetic modes and a prominent spin gap that is consistent with the ordered ground state of Cu moments coupled antiferromagnetically in spiral chains along the c axis and ferromagnetically in ab planes on the hexagonal cell. The data are in excellent agreement with a spin- 1 2 Hamiltonian that includes antiferromagnetic nearest-neighbor intrachain coupling J c=10.6(1) meV, ferromagnetic interchain coupling J ab=₋1.2 (1) meV, and exchange anisotropy ΔJ c=0.14(1) meV. We calculated the sublattice magnetization to be strongly reduced, ~0.39μ B. This appears compatible with a reduced Néel temperature, T N=14.5K

Understanding the nano- and macromechanical behaviour, the failure and fatigue mechanisms of advanced and natural polymer fibres by Raman/IR microspectrometry

NASA Astrophysics Data System (ADS)

Colomban, Philippe

2013-03-01

The coupled mechanical and Raman/infrared (IR) analysis of the (nano)structure and texture of synthetic and natural polymer fibres (polyamides (PA66), polyethylene terephthalate (PET), polypropylene (PP), poly(paraphenylene benzobisoxazole) (PBO), keratin/hair, Bombyx mori, Gonometa rufobrunea/postica Antheraea/Tussah silkworms and Nephila Madagascarensis spider silks) is applied so as to differentiate between crystalline and amorphous macromolecules. Bonding is very similar in the two cases but a broader distribution of conformations is observed for the amorphous macromolecules. These conclusions are then used to discuss the modifications induced by the application of a tensile or compressive stress, including the effects of fatigue. Detailed attention is paid to water and the inter-chain coupling for which the importance of hydrogen bonding is reconsidered. The significant role of the ‘amorphous’ bonds/domains in the process of fracture/fatigue is shown. Invited talk at the 6th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2012, 30 October-2 November 2012, Ha Long, Vietnam.

Structural analysis of an intact monoclonal antibody by online electrochemical reduction of disulfide bonds and Fourier transform ion cyclotron resonance mass spectrometry.

PubMed

Nicolardi, Simone; Deelder, André M; Palmblad, Magnus; van der Burgt, Yuri E M

2014-06-03

Structural confirmation and quality control of recombinant monoclonal antibodies (mAbs) by top-down mass spectrometry is still challenging due to the size of the proteins, disulfide content, and post-translational modifications such as glycosylation. In this study we have applied electrochemistry (EC) to overcome disulfide bridge complexity in top-down analysis of mAbs. To this end, an electrochemical cell was coupled directly to an electrospray ionization (ESI) source and a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer (MS) equipped with a 15 T magnet. By performing online EC-assisted reduction of interchain disulfide bonds in an intact mAb, the released light chains could be selected for tandem mass spectrometry (MS/MS) analysis without interference from heavy-chain fragments. Moreover, the acquisition of full MS scans under denaturing conditions allowed profiling of all abundant mAb glycoforms. Ultrahigh-resolution FTICR-MS measurements provided fully resolved isotopic distributions of intact mAb and enabled the identification of the most abundant adducts and other interfering species. Furthermore, it was found that reduction of interchain disulfide bonds occurs in the ESI source dependent on capillary voltage and solvent composition. This phenomenon was systematically evaluated and compared with the results obtained from reduction in the electrochemical cell.

Short-Range Order and Collective Dynamics of DMPC Bilayers: A Comparison between Molecular Dynamics Simulations, X-Ray, and Neutron Scattering Experiments

PubMed Central

Hub, Jochen S.; Salditt, Tim; Rheinstädter, Maikel C.; de Groot, Bert L.

2007-01-01

We present an extensive comparison of short-range order and short wavelength dynamics of a hydrated phospholipid bilayer derived by molecular dynamics simulations, elastic x-ray, and inelastic neutron scattering experiments. The quantities that are compared between simulation and experiment include static and dynamic structure factors, reciprocal space mappings, and electron density profiles. We show that the simultaneous use of molecular dynamics and diffraction data can help to extract real space properties like the area per lipid and the lipid chain ordering from experimental data. In addition, we assert that the interchain distance can be computed to high accuracy from the interchain correlation peak of the structure factor. Moreover, it is found that the position of the interchain correlation peak is not affected by the area per lipid, while its correlation length decreases linearly with the area per lipid. This finding allows us to relate a property of the structure factor quantitatively to the area per lipid. Finally, the short wavelength dynamics obtained from the simulations and from inelastic neutron scattering are analyzed and compared. The conventional interpretation in terms of the three-effective-eigenmode model is found to be only partly suitable to describe the complex fluid dynamics of lipid chains. PMID:17631531

Consequences of Energetic Frustration on the Ligand-Coupled Folding/Dimerization Dynamics of Allosteric Protein S100A12.

PubMed

Ren, Weitong; Li, Wenfei; Wang, Jun; Zhang, Jian; Wang, Wei

2017-10-26

Allosteric proteins are featured by energetic degeneracy of two (or more) functionally relevant conformations, therefore their energy landscapes are often locally frustrated. How such frustration affects the protein folding/binding dynamics is not well understood. Here, by using molecular simulations we study the consequences of local frustration in the dimerization dynamics of allosteric proteins based on a homodimer protein S100A12. Despite of the structural symmetry of the two EF-hand motifs in the three-dimensional structures, the S100A12 homodimer shows allosteric behaviors and local frustration only in half of its structural elements, i.e., the C-terminal EF-hand. We showed that such spatially asymmetric location of frustration leads to asymmetric dimerization pathways, in which the dimerization is dominantly initiated by the interchain binding of the minimally frustrated N-terminal EF-hands, achieving optimal balance between the requirements of rapid conformational switching and interchain assembling to the energy landscapes. We also showed that the local frustration, as represented by the double-basin topography of the energy landscape, gives rise to multiple cross-linked dimerization pathways, in which the dimerization is coupled with the allosteric motions of the C-terminal EF-hands. Binding of metal ions tends to reshape the energy landscape and modulate the dimerization pathways. In addition, by employing the frustratometer method, we showed that the highly frustrated residue-pairs in the C-terminal EF-hand are partially unfolded during the conformational transitions of the native homodimer, leading to lowing of free energy barrier. Our results revealed tight interplay between the local frustration of the energy landscape and the dimerization dynamics for allosteric proteins.

Relative stabilities of IgG1 and IgG4 Fab domains: Influence of the light–heavy interchain disulfide bond architecture

PubMed Central

Heads, James T; Adams, Ralph; D'Hooghe, Lena E; Page, Matt J T; Humphreys, David P; Popplewell, Andrew G; Lawson, Alastair D; Henry, Alistair J

2012-01-01

The stability of therapeutic antibodies is a prime pharmaceutical concern. In this work we examined thermal stability differences between human IgG1 and IgG4 Fab domains containing the same variable regions using the thermofluor assay. It was found that the IgG1 Fab domain is up to 11°C more stable than the IgG4 Fab domain containing the same variable region. We investigated the cause of this difference with the aim of developing a molecule with the enhanced stability of the IgG1 Fab and the biological properties of an IgG4 Fc. We found that replacing the seven residues, which differ between IgG1 CH1 and IgG4 CH1 domains, while retaining the native IgG1 light-heavy interchain disulfide (L–H) bond, did not affect thermal stability. Introducing the IgG1 type L–H interchain disulfide bond (DSB) into the IgG4 Fab resulted in an increase in thermal stability to levels observed in the IgG1 Fab with the same variable region. Conversely, replacement of the IgG1 L–H interchain DSB with the IgG4 type L–H interchain DSB reduced the thermal stability. We utilized the increased stability of the IgG1 Fab and designed a hybrid antibody with an IgG1 CH1 linked to an IgG4 Fc via an IgG1 hinge. This construct has the expected biophysical properties of both the IgG4 Fc and IgG1 Fab domains and may therefore be a pharmaceutically relevant format. PMID:22761163

Use of a small molecule as an initiator for interchain staudinger reaction: A new ATP sensing platform using product fluorescence.

PubMed

Yu, Huan; Zheng, Jing; Yang, Sheng; Asiri, Abdullah M; Alamry, Khalid A; Sun, Mingtai; Zhang, Kui; Wang, Suhua; Yang, Ronghua

2018-02-01

We demonstrated that a small molecule induced interchain Staudinger reaction can be employed for highly selective detection of adenosine triphosphate (ATP), an important energy-storage biomolecule. A designed ATP split aptamer (A1) was first functionalized with a weakly fluorescent coumarin derivative due to an azide group (azido-coumarin). The second DNA strand (A2) was covalently linked with triphenylphosphine, which could selectively and efficiently reduce azido to amino group through the Staudinger reaction. The A2 was then hybridized with a half of another designed longer DNA strand (T1). The second half of T1 was a split aptamer and selectively recognized ATP with A1 to form a sandwich structure. The specific interaction between ATP and the aptamers drew the two functionalized DNA strands (A1 and A2) together to initiate the interchain Staudinger reduction at fmol-nmol concentration level, hence produced fluorescent 7-aminocoumarin which could be used as an indicator for the presence of trace ATP. The reaction process had a concentration dependent manner with ATP in a large concentration range. Such a strategy of interchain Staudinger reaction can be extended to construct biosensors for other small functional molecules on the basis of judiciously designed aptamers. Copyright © 2017 Elsevier B.V. All rights reserved.

Absolute Side-chain Structure at Position 13 Is Required for the Inhibitory Activity of Bromein*

PubMed Central

Sawano, Yoriko; Hatano, Ken-ichi; Miyakawa, Takuya; Tanokura, Masaru

2008-01-01

Bromelain isoinhibitor (bromein), a cysteine proteinase inhibitor from pineapple stem, has a unique double-chain structure. The bromein precursor protein includes three homologous inhibitor domains, each containing an interchain peptide between the light and heavy chains. The interchain peptide in the single-chain precursor is immediately processed by bromelain, a target proteinase. In the present study, to clarify the essential inhibitory site of bromein, we constructed 44 kinds of site-directed and deletion mutants and investigated the inhibitory activity of each toward bromelain. As a result, the complete chemical structure of Leu13 in the light chain was revealed to be essential for inhibition. Pro12 prior to the leucine residue was also involved in the inhibitory activity and would control the location of the leucine side chain by the fixed φ dihedral angle of proline. Furthermore, the five-residue length of the interchain peptide was strictly required for the inhibitory activity. On the other hand, no inhibitory activity against bromelain was observed by the substitution of proline for the N terminus residue Thr15 of the interchain peptide. In summary, these mutational analyses of bromein demonstrated that the appropriate position and conformation of Leu13 are absolutely crucial for bromelain inhibition. PMID:18948264

Fused electron deficient semiconducting polymers for air stable electron transport.

PubMed

Onwubiko, Ada; Yue, Wan; Jellett, Cameron; Xiao, Mingfei; Chen, Hung-Yang; Ravva, Mahesh Kumar; Hanifi, David A; Knall, Astrid-Caroline; Purushothaman, Balaji; Nikolka, Mark; Flores, Jean-Charles; Salleo, Alberto; Bredas, Jean-Luc; Sirringhaus, Henning; Hayoz, Pascal; McCulloch, Iain

2018-01-29

Conventional semiconducting polymer synthesis typically involves transition metal-mediated coupling reactions that link aromatic units with single bonds along the backbone. Rotation around these bonds contributes to conformational and energetic disorder and therefore potentially limits charge delocalisation, whereas the use of transition metals presents difficulties for sustainability and application in biological environments. Here we show that a simple aldol condensation reaction can prepare polymers where double bonds lock-in a rigid backbone conformation, thus eliminating free rotation along the conjugated backbone. This polymerisation route requires neither organometallic monomers nor transition metal catalysts and offers a reliable design strategy to facilitate delocalisation of frontier molecular orbitals, elimination of energetic disorder arising from rotational torsion and allowing closer interchain electronic coupling. These characteristics are desirable for high charge carrier mobilities. Our polymers with a high electron affinity display long wavelength NIR absorption with air stable electron transport in solution processed organic thin film transistors.

A Thermochromic Superhydrophobic Surface

PubMed Central

Cataldi, Pietro; Bayer, Ilker S.; Cingolani, Roberto; Marras, Sergio; Chellali, Ryad; Athanassiou, Athanassia

2016-01-01

Highly enhanced solid-state thermochromism is observed in regioregular poly(3-hexylthiophene), P3HT, when deposited on a superhydrophobic polymer-SiO2 nanocomposite coating. The conformal P3HT coating on the nanocomposite surface does not alter or reduce superhydrophicity while maintaining its reversible enhanced thermochromism. The polymeric matrix of the superhydrophobic surface is comprised of a blend of poly(vinylidene fluoride-co-hexafluoropropylene) copolymer and an acrylic adhesive. Based on detailed X-ray diffraction measurements, this long-lasting, repeatable and hysteresis-free thermochromic effect is attributed to the enhancement of the Bragg peak associated with the d-spacing of interchain directional packing (100) which remains unaltered during several heating-cooling cycles. We propose that the superhydrophobic surface confines π–π interchain stacking in P3HT with uniform d-spacing into its nanostructured texture resulting in better packing and reduction in face-on orientation. The rapid response of the system to sudden temperature changes is also demonstrated by water droplet impact and bounce back on heated surfaces. This effect can be exploited for embedded thin film temperature sensors for metal coatings. PMID:27301422

Approaching Intra- and Interchain Charge Transport of Conjugated Polymers Facilely by Topochemical Polymerized Single Crystals.

PubMed

Yao, Yifan; Dong, Huanli; Liu, Feng; Russell, Thomas P; Hu, Wenping

2017-08-01

Charge transport of small molecules is measured well with scanning tunneling microscopy, conducting atomic force microscopy, break junction, nanopore, and covalently bridging gaps. However, the manipulation and measurement of polymer chains remain a long-standing fundamental issue in conjugated polymers and full of challenge since conjugated polymers are naturally disordered materials. Here, a fundamental breakthrough in generating high-quality conjugated-polymer nanocrystals with extended conjugation and exceptionally high degrees of order using a surface-supported topochemical polymerization method is demonstrated. In the crystal the conjugated-polymer chains are extended along the long axis of the crystal with the side chains perpendicular to the long axis. Devices with conducting channels along the polymer chains show efficient charge transport, nearly two orders of magnitude greater than the interchain charge transport along the π-π stacking direction. This is the first example to clarify intra- and interchain charge transport based on an individual single crystal of conjugated polymers, and demonstrate the importance of intrachain charge transport in plastic electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optically detected magnetic resonance studies on pi-conjugated polymers and novel carbon allotropes

NASA Astrophysics Data System (ADS)

Partee, Jonathan Farel

1997-12-01

The photophysics of poly(p-phenylene)-type ladder polymers (m-LPPP) and 2,5-dibutoxy poly(p-phenylene ethynylene) (DBO-PPE) films and solutions were studied by X-band photoluminescence detected magnetic resonance (PLDMR). Frequency resolved PLDMR measurements on LPPP, DBO-PPE, poly(3-hexylthiophene) (P3HT), poly(p-phenylene-vinylene) (PPV), and Csb{70} are also reported and discussed. All the polymer samples exhibit three distinct features when excited at wavelengths lambda≥ 458nm: (i) A narrow PL-enhancing spin-1/2 polaron resonance, (ii) broad full- and (iii) half-field spin-1 triplet exciton powder patterns due to the Deltamsbs = 1 and Deltamsbs = 2 transitions among the triplet sublevels, respectively. The full-width at half maximum (FWHM) of the spin-1/2 resonance in LPPP decreased from film to solution. However, the FWHM of that resonance in PPE was identical at all concentrations. This spin-1/2 resonance is assigned to the magnetic resonance enhancement of the recombination of both interchain and intrachain-intersegment polaron pairs which quench singlet exciton recombination. In solid m-LPPP samples, the aggregate PL gives rise to a proportionally higher magnetic resonance effect than other parts of the PL spectrum. In DBO-PPE and m-LPPP solutions, the triplet resonance decreased with decreasing concentration. This suggests that the triplet state is an intrinsic long-lived (˜30mus) trapped state localized on a phenylene ring and stabilized by coupling to a unit of an adjacent chain. Frequency resolved measurements of the lifetime of the species affected by the resonance conditions for all the polymers are described and discussed. The lifetimes appeared to include: (i) fast (9mus ≤ tausb1 ≤ 40mus) and (ii) slow (575mus\\ ≤ tausb2≤ 1868mus) components. The lifetimes increased with increasing concentration of the polymers in toluene solutions. These results can be interpreted to provide support for the interchain/intersegment polaron model or a distribution of lifetimes model.

Correlation between Photovoltaic Performance and Interchain Ordering Induced Delocalization of Electronics States in Conjugated Polymer Blends.

PubMed

Chandrasekaran, Naresh; Gann, Eliot; Jain, Nakul; Kumar, Anshu; Gopinathan, Sreelekha; Sadhanala, Aditya; Friend, Richard H; Kumar, Anil; McNeill, Christopher R; Kabra, Dinesh

2016-08-10

In this paper we correlate the solar cell performance with bimolecular packing of donor:acceptor bulk heterojunction (BHJ) organic solar cells (OSCs), where interchain ordering of the donor molecule and its influence on morphology, optical properties, and charge carrier dynamics of BHJ solar cells are studied in detail. Solar cells that are fabricated using more ordered defect free 100% regioregular poly(3-hexylthiophene) (DF-P3HT) as the donor polymer show ca. 10% increase in the average power conversion efficiency (PCE) when compared to that of the solar cell fabricated using 92% regioregularity P3HT, referred to as rr-P3HT. EQE and UV-vis absorption spectrum show a clear increase in the 607 nm vibronic shoulder of the DF-P3HT blend suggesting better interchain ordering which was also reflected in the less Urbach energy (Eu) value for this system. The increase in ordering inside the blend has enhanced the hole-mobility which is calculated from the single carrier device J-V characteristics. Electroluminance (EL) studies on the DF-P3HT system showed a red-shifted peak when compared to rr-P3HT-based devices suggesting low CT energy states in DF-P3HT. The morphologies of the blend films are studied using AFM and grazing-incidence wide-angle X-ray scattering (GIWAXS) suggesting increase in the roughness and phase segregation which could enhance the internal scattering of the light inside the device and improvement in the crystallinity along alkyl and π-stacking direction. Hence, higher PCE, lower Eu, red-shifted EL emission, high hole-mobility, and better crystallinity suggest improved interchain ordering has facilitated a more delocalized HOMO state in DF-P3HT-based BHJ solar cells.

Effect of PEO molecular weight on the miscibility and dynamics in epoxy/PEO blends.

PubMed

Lu, Shoudong; Zhang, Rongchun; Wang, Xiaoliang; Sun, Pingchuan; Lv, Weifeng; Liu, Qingjie; Jia, Ninghong

2015-11-01

In this work, the effect of poly(ethylene oxide) (PEO) molecular weight in blends of epoxy (ER) and PEO on the miscibility, inter-chain weak interactions and local dynamics were systematically investigated by multi-frequency temperature modulation DSC and solid-state NMR techniques. We found that the molecular weight (M(w)) of PEO was a crucial factor in controlling the miscibility, chain dynamics and hydrogen bonding interactions between PEO and ER. A critical PEO molecular weight (M(crit)) around 4.5k was found. PEO was well miscible with ER when the molecular weight was below M(crit), where the chain motion of PEO was restricted due to strong inter-chain hydrogen bonding interactions. However, for the blends with high molecular weight PEO (M(w) > M(crit)), the miscibility between PEO and ER was poor, and most of PEO chains were considerably mobile. Finally, polarization inversion spin exchange at magic angle (PISEMA) solid-state NMR experiment further revealed the different mobility of the PEO in ER/PEO blends with different molecular weight of PEO at molecular level. Based on the DSC and NMR results, a tentative model was proposed to illustrate the miscibility in ER/PEO blends.

Comment on ‘Oxygen vacancy-induced magnetic moment in edge-sharing CuO2 chains of Li2CuO2’

NASA Astrophysics Data System (ADS)

Kuzian, R. O.; Klingeler, R.; Lorenz, W. E. A.; Wizent, N.; Nishimoto, S.; Nitzsche, U.; Rosner, H.; Milosavljevic, D.; Hozoi, L.; Yadav, R.; Richter, J.; Hauser, A.; Geck, J.; Hayn, R.; Yushankhai, V.; Siurakshina, L.; Monney, C.; Schmitt, T.; Thar, J.; Roth, G.; Ito, T.; Yamaguchi, H.; Matsuda, M.; Johnston, S.; Málek, J.; Drechsler, S.-L.

2018-05-01

In a recent work devoted to the magnetism of Li2CuO2, Shu et al (2017 New J. Phys. 19, 023026) have proposed a ‘simplified’ unfrustrated microscopic model that differs considerably from the models refined through decades of prior work. We show that the proposed model is at odds with known experimental data, including the reported magnetic susceptibility χ(T) data up to 550 K. Using an 8th order high-temperature expansion for χ(T), we show that the experimental data for Li2CuO2 are consistent with the prior model derived from inelastic neutron scattering studies. We also establish the T-range of validity for a Curie–Weiss law for the real frustrated magnetic system. We argue that the knowledge of the long-range ordered magnetic structure for T < T N and of χ(T) in a restricted T-range provides insufficient information to extract all of the relevant couplings in frustrated magnets; the saturation field and INS data must also be used to determine several exchange couplings, including the weak but decisive frustrating antiferromagnetic interchain couplings.

Synthesis, magnetic properties and electronic structure of the S  =  ½ uniform spin chain system InCuPO5

NASA Astrophysics Data System (ADS)

Koteswararao, B.; Hazra, Binoy K.; Rout, Dibyata; Srinivasarao, P. V.; Srinath, S.; Panda, S. K.

2017-07-01

We have studied the structural and magnetic properties and electronic structure of the compound InCuPO5 synthesized by a solid state reaction method. The structure of InCuPO5 comprises S  =  ½ uniform spin chains formed by corner-shared CuO4 units. Magnetic susceptibility (χ(T)) data show a broad maximum at about 65 K, a characteristic feature of one-dimensional (1D) magnetism. The χ(T) data are fitted to the coupled S  =  ½ Heisenberg antiferromagnetic (HAFM) uniform chain model that gives the intra-chain coupling (J/k B) between nearest-neighbor Cu2+ ions as  -100 K and the ratio of inter-chain to intra-chain coupling (J‧/J) as about 0.07. The exchange couplings estimated from the magnetic data analysis are in good agreement with the values computed from the electronic structure calculations based on the density functional theory  +  Hubbard U (DFT  +  U) approach. The combination of theoretical and experimental analysis confirms that InCuPO5 is a candidate material for weakly coupled S  = ½ uniform chains. A detailed theoretical analysis of the electronic structure further reveals that the system is insulating with a gap of 2.4 eV and a local moment of 0.70 µ B/Cu.

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

Peng, Hua; College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024; Kioussis, Nicholas, E-mail: nick.kioussis@csun.edu

Using ab initio based calculations, we have calculated the intrinsic lattice thermal conductivity of chiral tellurium. We show that the interplay between the strong covalent intrachain and weak van der Waals interchain interactions gives rise to the phonon band gap between the lower and higher optical phonon branches. The underlying mechanism of the large anisotropy of the thermal conductivity is the anisotropy of the phonon group velocities and of the anharmonic interatomic force constants (IFCs), where large interchain anharmonic IFCs are associated with the lone electron pairs. We predict that tellurium has a large three-phonon scattering phase space that resultsmore » in low thermal conductivity. The thermal conductivity anisotropy decreases under applied hydrostatic pressure.« less

PSMA-targeted bispecific Fab conjugates that engage T cells.

PubMed

Patterson, James T; Isaacson, Jason; Kerwin, Lisa; Atassi, Ghazi; Duggal, Rohit; Bresson, Damien; Zhu, Tong; Zhou, Heyue; Fu, Yanwen; Kaufmann, Gunnar F

2017-12-15

Bioconjugate formats provide alternative strategies for antigen targeting with bispecific antibodies. Here, PSMA-targeted Fab conjugates were generated using different bispecific formats. Interchain disulfide bridging of an αCD3 Fab enabled installation of either the PSMA-targeting small molecule DUPA (SynFab) or the attachment of an αPSMA Fab (BisFab) by covalent linkage. Optimization of the reducing conditions was critical for selective interchain disulfide reduction and good bioconjugate yield. Activity of αPSMA/CD3 Fab conjugates was tested by in vitro cytotoxicity assays using prostate cancer cell lines. Both bispecific formats demonstrated excellent potency and antigen selectivity. Copyright © 2017. Published by Elsevier Ltd.

A unifying model for elongational flow of polymer melts and solutions based on the interchain tube pressure concept

NASA Astrophysics Data System (ADS)

Wagner, Manfred Hermann; Rolón-Garrido, Víctor Hugo

2015-04-01

An extended interchain tube pressure model for polymer melts and concentrated solutions is presented, based on the idea that the pressures exerted by a polymer chain on the walls of an anisotropic confinement are anisotropic (M. Doi and S. F. Edwards, The Theory of Polymer Dynamics, Oxford University Press, New York, 1986). In a tube model with variable tube diameter, chain stretch and tube diameter reduction are related, and at deformation rates larger than the inverse Rouse time τR, the chain is stretched and its confining tube becomes increasingly anisotropic. Tube diameter reduction leads to an interchain pressure in the lateral direction of the tube, which is proportional to the 3rd power of stretch (G. Marrucci and G. Ianniruberto. Macromolecules 37, 3934-3942, 2004). In the extended interchain tube pressure (EIP) model, it is assumed that chain stretch is balanced by interchain tube pressure in the lateral direction, and by a spring force in the longitudinal direction of the tube, which is linear in stretch. The scaling relations established for the relaxation modulus of concentrated solutions of polystyrene in oligomeric styrene (M. H. Wagner, Rheol. Acta 53, 765-777, 2014, M. H. Wagner, J. Non-Newtonian Fluid Mech. http://dx.doi.org/10.1016/j.jnnfm.2014.09.017, 2014) are applied to the solutions of polystyrene (PS) in diethyl phthalate (DEP) investigated by Bhattacharjee et al. (P. K. Bhattacharjee et al., Macromolecules 35, 10131-10148, 2002) and Acharya et al. (M. V. Acharya et al. AIP Conference Proceedings 1027, 391-393, 2008). The scaling relies on the difference ΔTg between the glass-transition temperatures of the melt and the glass-transition temperatures of the solutions. ΔTg can be inferred from the reported zero-shear viscosities, and the BSW spectra of the solutions are obtained from the BSW spectrum of the reference melt with good accuracy. Predictions of the EIP model are compared to the steady-state elongational viscosity data of PS/DEP solutions. Except for a possible influence of solvent quality, linear and nonlinear viscoelasticity of entangled polystyrene solutions can thus be obtained from the linear-viscoelastic characteristics of a reference polymer melt and the shift of the glass transition temperature between melt and solution.

Interchain hydrophobic clustering promotes rigidity in HIV-1 protease flap dynamics: new insights from molecular dynamics.

PubMed

Meher, Biswa Ranjan; Kumar, Mattaparthi Venkata Satish; Bandyopadhyay, Pradipta

2014-01-01

The dynamics of HIV-1 protease (HIV-pr), a drug target for HIV infection, has been studied extensively by both computational and experimental methods. The flap dynamics of HIV-pr is considered to be more important for better ligand binding and enzymatic actions. Moreover, it has been demonstrated that the drug-induced mutations can change the flap dynamics of HIV-pr affecting the binding affinity of the ligands. Therefore, detailed understanding of flap dynamics is essential for designing better inhibitors. Previous computational investigations observed significant variation in the flap opening in nanosecond time scale indicating that the dynamics is highly sensitive to the simulation protocols. To understand the sensitivity of the flap dynamics on the force field and simulation protocol, molecular dynamics simulations of HIV-pr have been performed with two different AMBER force fields, ff99 and ff02. Two different trajectories (20 ns each) were obtained using the ff99 and ff02 force field. The results showed polarizable force field (ff02) make the flap tighter than the nonpolarizable force field (ff99). Some polar interactions and hydrogen bonds involving flap residues were found to be stronger with ff02 force field. The formation of interchain hydrophobic cluster (between flap tip of one chain and active site wall of another chain) was found to be dominant in the semi-open structures obtained from the simulations irrespective of the force field. It is proposed that an inhibitor, which will promote this interchain hydrophobic clustering, may make the flaps more rigid, and presumably the effect of mutation would be small on ligand binding.

An optimized chemical synthesis of human relaxin-2.

PubMed

Barlos, Kostas K; Gatos, Dimitrios; Vasileiou, Zoe; Barlos, Kleomenis

2010-04-01

Human gene 2 relaxin (RLX) is a member of the insulin superfamily and is a multi-functional factor playing a vital role in pregnancy, aging, fibrosis, cardioprotection, vasodilation, inflammation, and angiogenesis. RLX is currently applied in clinical trials to cure among others acute heart failure, fibrosis, and preeclampsia. The synthesis of RLX by chemical methods is difficult because of the insolubility of its B-chain and the required laborious and low yielding site-directed combination of its A (RLXA) and B (RLXB) chains. We report here that oxidation of the Met(25) residue of RLXB improves its solubility, allowing its effective solid-phase synthesis and application in random interchain combination reactions with RLXA. Linear Met(O)(25)-RLX B-chain (RLXBO) reacts with a mixture of isomers of bicyclic A-chain (bcRLXA) giving exclusively the native interchain combination. Applying this method Met(O)(25)-RLX (RLXO) was obtained in 62% yield and was easily converted to RLX in 78% yield, by reduction with ammonium iodide. Copyright (c) 2010 European Peptide Society and John Wiley & Sons, Ltd.

Magnetic Structure and Exchange Interactions in Quasi-One-Dimensional MnCl 2(urea) 2

DOE PAGES

Manson, Jamie L.; Huang, Qing-zhen; Brown, Craig M.; ...

2015-12-08

MnCl 2(urea) 2 is a new linear chain coordination polymer that exhibits slightly counter-rotated Mn 2Cl 2 rhomboids along the chain-axis. The material crystallizes in the noncentrosymmetric orthorhombic space group Iba2, with each Mn(II) ion equatorially surrounded by four Cl – that lead to bibridged ribbons. Additionally, urea ligands coordinate via O atoms in the axial positions. Hydrogen bonds of the Cl···H–N and O···H–N type link the chains into a quasi-3D network. Magnetic susceptibility data reveal a broad maximum at 9 K that is consistent with short-range magnetic order. Pulsed-field magnetization measurements conducted at 0.6 K show that a fullymore » polarized magnetic state is achieved at B sat = 19.6 T with another field-induced phase transition occurring at 2.8 T. Zero-field neutron diffraction studies made on a powdered sample of MnCl 2(urea) 2 reveal that long-range magnetic order occurs below T N = 3.2(1) K. Additional Bragg peaks due to antiferromagnetic (AFM) ordering can be indexed according to the Ib'a2' magnetic space group and propagation vector τ = [0, 0, 0]. Rietveld profile analysis of these data revealed a Néel-type collinear ordering of Mn(II) ions with an ordered magnetic moment of 4.06(6) μ B (5 μ B is expected for isotropic S = 5/2) oriented along the b-axis, i.e., perpendicular to the chain-axis that runs along the c-direction. Owing to the potential for spatial exchange anisotropy and the pitfalls in modeling bulk magnetic data, we analyzed inelastic neutron scattering data to retrieve the exchange constants: J c = 2.22 K (intrachain), J a = -0.10 K (interchain), and D = -0.14 K with J > 0 assigned to AFM coupling. Lastly, this J configuration is most unusual and contrasts the more commonly observed AFM interchain coupling of 1D chains.« less

Heteronuclear NMR assignments and secondary structure of the coiled coil trimerization domain from cartilage matrix protein in oxidized and reduced forms.

PubMed Central

Wiltscheck, R.; Kammerer, R. A.; Dames, S. A.; Schulthess, T.; Blommers, M. J.; Engel, J.; Alexandrescu, A. T.

1997-01-01

The C-terminal oligomerization domain of chicken cartilage matrix protein is a trimeric coiled coil comprised of three identical 43-residue chains. NMR spectra of the protein show equivalent magnetic environments for each monomer, indicating a parallel coiled coil structure with complete threefold symmetry. Sequence-specific assignments for 1H-, 15N-, and 13C-NMR resonances have been obtained from 2D 1H NOESY and TOCSY spectra, and from 3D HNCA, 15N NOESY-HSQC, and HCCH-TOCSY spectra. A stretch of alpha-helix encompassing five heptad repeats (35 residues) has been identified from intra-chain HN-HN and HN-H alpha NOE connectivities. 3JHNH alpha coupling constants, and chemical shift indices. The alpha-helix begins immediately downstream of inter-chain disulfide bonds between residues Cys 5 and Cys 7, and extends to near the C-terminus of the molecule. The threefold symmetry of the molecule is maintained when the inter-chain disulfide bonds that flank the N-terminus of the coiled coil are reduced. Residues Ile 21 through Glu 36 show conserved chemical shifts and NOE connectivities, as well as strong protection from solvent exchange in the oxidized and reduced forms of the protein. By contrast, residues Ile 10 through Val 17 show pronounced chemical shift differences between the oxidized and reduced protein. Strong chemical exchange NOEs between HN resonances and water indicate solvent exchange on time scales faster than 10 s, and suggests a dynamic fraying of the N-terminus of the coiled coil upon reduction of the disulfide bonds. Possible roles for the disulfide crosslinks of the oligomerization domain in the function of cartilage matrix protein are proposed. PMID:9260286

Br...Br and van der Waals interactions along a homologous series: crystal packing of 1,2-dibromo-4,5-dialkoxybenzenes.

PubMed

Suarez, Sebastián A; Muller, Federico; Gutiérrez Suburu, Matías E; Fonrouge, Ana; Baggio, Ricardo F; Cukiernik, Fabio D

2016-10-01

The crystalline structures of four homologues of the 1,2-dibromo-4,5-dialkoxybenzene series [Br 2 C 6 H 2 (OC n H 2n + 1 ) 2 for n = 2, 12, 14 and 18] have been solved by means of single-crystal crystallography. Comparison along the series, including the previously reported n = 10 and n = 16 derivatives, shows a clear metric trend (b and c essentially fixed along the series and a growing linearly with n), in spite of some subtle differences in space groups and/or packing modes. A uniform packing pattern for the aliphatic chains has been found for the n = 12 to 18 homologues, which slightly differs from that of the n = 10 derivative. The crystalline structures of all the higher homologues (n = 10-18) seem to arise from van der Waals interchain interactions and, to a lesser extent, type II Br...Br interactions. The dominant role of interchain interactions provides direct structural support for the usual interpretation of melting point trends like that found along this series. Atoms in Molecules (AIM) analysis allows a comparison of the relative magnitude of the interchain and Br...Br interactions, an analysis validated by the measured melting enthalpies.

Symmetry-Breaking Phase Transition without a Peierls Instability in Conducting Monoatomic Chains

NASA Astrophysics Data System (ADS)

Blumenstein, C.; Schäfer, J.; Morresi, M.; Mietke, S.; Matzdorf, R.; Claessen, R.

2011-10-01

The one-dimensional (1D) model system Au/Ge(001), consisting of linear chains of single atoms on a surface, is scrutinized for lattice instabilities predicted in the Peierls paradigm. By scanning tunneling microscopy and electron diffraction we reveal a second-order phase transition at 585 K. It leads to charge ordering with transversal and vertical displacements and complex interchain correlations. However, the structural phase transition is not accompanied by the electronic signatures of a charge density wave, thus precluding a Peierls instability as origin. Instead, this symmetry-breaking transition exhibits three-dimensional critical behavior. This reflects a dichotomy between the decoupled 1D electron system and the structural elements that interact via the substrate. Such substrate-mediated coupling between the wires thus appears to have been underestimated also in related chain systems.

Interplay of localized pyrene chromophores and π-conjugation in novel poly(2,7-pyrene) ladder polymers

NASA Astrophysics Data System (ADS)

Rudnick, Alexander; Kass, Kim-Julia; Preis, Eduard; Scherf, Ullrich; Bässler, Heinz; Köhler, Anna

2017-05-01

We present a detailed spectroscopic study, along with the synthesis, of conjugated, ladder-type 2,7-linked poly(pyrene)s. We observe a delocalization of the first singlet excited state along the polymer backbone, i.e., across the 2,7 linkage in the pyrene moiety, in contrast to earlier studies on conjugated 2,7-linked poly(pyrene)s without ladder structure. The electronic signature of the pyrene unit is, however, manifested in an increased lifetime and reduced oscillator strength as well as a modified vibronic progression in absorption of the singlet state compared to a ladder-type poly(para-phenylene) (MeLPPP). Furthermore, the reduced oscillator strength and increased lifetime slow down Förster-type energy transfer in films, where this transfer occurs to sites with increasing inter-chain coupling of H-type nature.

Kinetics and reaction coordinates of the reassembly of protein fragments via forward flux sampling.

PubMed

Borrero, Ernesto E; Contreras Martínez, Lydia M; DeLisa, Matthew P; Escobedo, Fernando A

2010-05-19

We studied the mechanism of the reassembly and folding process of two fragments of a split lattice protein by using forward flux sampling (FFS). Our results confirmed previous thermodynamics and kinetics analyses that suggested that the disruption of the critical core (of an unsplit protein that folds by a nucleation mechanism) plays a key role in the reassembly mechanism of the split system. For several split systems derived from a parent 48-mer model, we estimated the reaction coordinates in terms of collective variables by using the FFS least-square estimation method and found that the reassembly transition is best described by a combination of the total number of native contacts, the number of interchain native contacts, and the total conformational energy of the split system. We also analyzed the transition path ensemble obtained from FFS simulations using the estimated reaction coordinates as order parameters to identify the microscopic features that differentiate the reassembly of the different split systems studied. We found that in the fastest folding split system, a balanced distribution of the original-core amino acids (of the unsplit system) between protein fragments propitiates interchain interactions at early stages of the folding process. Only this system exhibits a different reassembly mechanism from that of the unsplit protein, involving the formation of a different folding nucleus. In the slowest folding system, the concentration of the folding nucleus in one fragment causes its early prefolding, whereas the second fragment tends to remain as a detached random coil. We also show that the reassembly rate can be either increased or decreased by tuning interchain cooperativeness via the introduction of a single point mutation that either strengthens or weakens one of the native interchain contacts (prevalent in the transition state ensemble). Copyright (c) 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

The stability of cellulose: a statistical perspective from a coarse-grained model of hydrogen-bond networks.

PubMed

Shen, Tongye; Gnanakaran, S

2009-04-22

A critical roadblock to the production of biofuels from lignocellulosic biomass is the efficient degradation of crystalline microfibrils of cellulose to glucose. A microscopic understanding of how different physical conditions affect the overall stability of the crystalline structure of microfibrils could facilitate the design of more effective protocols for their degradation. One of the essential physical interactions that stabilizes microfibrils is a network of hydrogen (H) bonds: both intrachain H-bonds between neighboring monomers of a single cellulose polymer chain and interchain H-bonds between adjacent chains. We construct a statistical mechanical model of cellulose assembly at the resolution of explicit hydrogen-bond networks. Using the transfer matrix method, the partition function and the subsequent statistical properties are evaluated. With the help of this lattice-based model, we capture the plasticity of the H-bond network in cellulose due to frustration and redundancy in the placement of H-bonds. This plasticity is responsible for the stability of cellulose over a wide range of temperatures. Stable intrachain and interchain H-bonds are identified as a function of temperature that could possibly be manipulated toward rational destruction of crystalline cellulose.

The Contribution of Interchain Salt Bridges to Triple-Helical Stability in Collagen

PubMed Central

Gurry, Thomas; Nerenberg, Paul S.; Stultz, Collin M.

2010-01-01

Abstract Studies on collagen and collagen-like peptides suggest that triple-helical stability can vary along the amino acid chain. In this regard, it has been shown that lysine residues in the Y position and acidic residues in the X′ position of (GPO)3GXYGX′Y′(GPO)3 peptides lead to triple-helical structures with melting temperatures similar to (GPO)8 (where O is hydroxyproline), which is generally regarded as the most stable collagen-like sequence of this length. This enhanced stability has been attributed to the formation of salt bridges between adjacent collagen chains. In this study, we explore the relationship between interchain salt bridge formation and triple-helical stability using detailed molecular simulations. Although our results confirm that salt bridges promote triple-helical stability, we find that not all salt bridges are created equal. In particular, lysine-glutamate salt bridges are most stabilizing when formed between residues in the middle strand (B) and the trailing strand (C), whereas lysine-aspartate salt bridges are most stabilizing when formed between residues in the leading (A) and middle (B) strand—the latter observation being consistent with recent NMR data on a heterotrimeric model peptide. Overall, we believe these data clarify the role of salt bridges in modulating triple-helical stability and can be used to guide the design of collagen-like peptides that have specific interchain interactions. PMID:20513408

Survival condition for low-frequency quasi-one-dimensional breathers in a two-dimensional strongly anisotropic crystal

NASA Astrophysics Data System (ADS)

Savin, A. V.; Zubova, E. A.; Manevitch, L. I.

2005-06-01

We investigate a two-dimensional (2D) strongly anisotropic crystal (2D SAC) on substrate: 2D system of coupled linear chains of particles with strong intrachain and weak interchain interactions, each chain being subjected to the sine background potential. Nonlinear dynamics of one of these chains when the rest of them are fixed is reduced to the well known Frenkel-Kontorova (FK) model. Depending on strengh of the substrate, the 2D SAC models a variety of physical systems: polymer crystals with identical chains having light side groups, an array of inductively coupled long Josephson junctions, anisotropic crystals having light and heavy sublattices. Continuum limit of the FK model, the sine-Gordon (sG) equation, allows two types of soliton solutions: topological solitons and breathers. It is known that the quasi-one-dimensional topological solitons can propagate also in a chain of 2D system of coupled chains and even in a helix chain in a three-dimensional model of polymer crystal. In contrast to this, numerical simulation shows that the long-living breathers inherent to the FK model do not exist in the 2D SAC with weak background potential. The effect changes scenario of kink-antikink collision with small relative velocity: at weak background potential the collision always results only in intensive phonon radiation while kink-antikink recombination in the FK model results in long-living low-frequency sG breather creation. We found the survival condition for breathers in the 2D SAC on substrate depending on breather frequency and strength of the background potential. The survival condition bears no relation to resonances between breather frequency and frequencies of phonon band—contrary to the case of the FK model.

Electronic and spin dynamics in the insulating iron pnictide NaFe0.5Cu0.5As

NASA Astrophysics Data System (ADS)

Zhang, Shunhong; He, Yanjun; Mei, Jia-Wei; Liu, Feng; Liu, Zheng

2017-12-01

NaFe0.5Cu0.5As represents a rare exception in the metallic iron pnictide family, in which a small insulating gap is opened. Based on first-principles study, we provide a comprehensive theoretical characterization of this insulating compound. The Fe3 + spin degree of freedom is quantified as a quasi-one-dimensional (1D) S =5/2 Heisenberg model. The itinerant As hole state is downfolded to a px y-orbital hopping model on a square lattice. An orbital-dependent Hund's coupling between the spin and the hole is revealed. Several important material properties are analyzed, including (a) the factors affecting the small p -d charge-transfer gap; (b) the role of extra interchain Fe atoms; and (c) quasi-1D spin excitation in the Fe chains. The experimental manifestations of these properties are discussed.

One-dimensional magnetic fluctuations in the spin-2 triangular lattice alpha-NaMnO2.

PubMed

Stock, C; Chapon, L C; Adamopoulos, O; Lappas, A; Giot, M; Taylor, J W; Green, M A; Brown, C M; Radaelli, P G

2009-08-14

The S=2 anisotropic triangular lattice alpha-NaMnO2 is studied by neutron inelastic scattering. Antiferromagnetic order occurs at T< or =45 K with opening of a spin gap. The spectral weight of the magnetic dynamics above the gap (Delta approximately equal to 7.5 meV) has been analyzed by the single-mode approximation. Excellent agreement with the experiment is achieved when a dominant exchange interaction (|J|/k(B) approximately 73 K), along the monoclinic b axis and a sizable easy-axis magnetic anisotropy (|D|/k(B) approximately 3 K) are considered. Despite earlier suggestions for two-dimensional spin interactions, the dynamics illustrate strongly coupled antiferromagnetic S=2 chains and cancellation of the interchain exchange due to the lattice topology. alpha-NaMnO2 therefore represents a model system where the geometric frustration is resolved through the lowering of the dimensionality of the spin interactions.

Coupled antiferromagnetic spin-1/2 chains in green dioptase, Cu6 [Si6O18.6] H2O

NASA Astrophysics Data System (ADS)

Podlesnyak, Andrey; Anovitz, L. M.; Kolesnikov, A. I.; Matsuda, M.; Prisk, T. R.; Ehlers, G.; Toth, S.

Gem crystals of natural dioptase with colors ranging from emerald-green to bluish have delighted people since ancient times and still attract attention of mineral collectors around the globe. The crystal structure of green dioptase (space group R 3) consists of corrugated silicate rings Si6O<18 interconnected by Cu2+ ions. Oxygen atoms form axially-elongated octahedral of CuO4(H2O)2. The magnetic ground state of green dioptase remains controversial. We report inelastic neutron scattering measurements of the magnetic excitations of green dioptase Cu6 [ Si6O18.6 ] H2O. The observed spectrum contains two magnetic modes and a prominent spin gap that is consistent with the ordered ground state of Cu moments coupled antiferromagnetically in spiral chains along the c axis and ferromagnetically in ab planes on the hexagonal cell. The data are in excellent agreement with a spin-1/2 Hamiltonian that includes AFM nearest-neighbor intra-chain coupling Jc = 10 . 6 (1) meV, ferromagnetic inter-chain coupling Jab = - 1 . 2 (1) meV and exchange anisotropy ΔJc = 0 . 14 (1) meV. This appears compatible with reduced Nèel temperature, TN = 14 . 5 K <

A Novel Method of Extraction of Blend Component Structure from SANS Measurements of Homopolymer Bimodal Blends.

PubMed

Smerdova, Olga; Graham, Richard S; Gasser, Urs; Hutchings, Lian R; De Focatiis, Davide S A

2014-05-01

A new method is presented for the extraction of single-chain form factors and interchain interference functions from a range of small-angle neutron scattering (SANS) experiments on bimodal homopolymer blends. The method requires a minimum of three blends, made up of hydrogenated and deuterated components with matched degree of polymerization at two different chain lengths, but with carefully varying deuteration levels. The method is validated through an experimental study on polystyrene homopolymer bimodal blends with [Formula: see text]. By fitting Debye functions to the structure factors, it is shown that there is good agreement between the molar mass of the components obtained from SANS and from chromatography. The extraction method also enables, for the first time, interchain scattering functions to be produced for scattering between chains of different lengths. [Formula: see text].

Tuning of chain chirality by interchain stacking forces and the structure-property relationship in coordination systems constructed by meridional FeIII cyanide and MnIII Schiff bases.

PubMed

Sohn, Ah Ram; Lim, Kwang Soo; Kang, Dong Won; Song, Jeong Hwa; Koh, Eui Kwan; Moon, Dohyun; Hong, Chang Seop

2016-12-06

We synthesized six Fe(iii)-Mn(iii) bimetallic compounds by self-assembling the newly developed mer-Fe cyanide PPh 4 [Fe(Clqpa)(CN) 3 ]·H 2 O (1) and PPh 4 [Fe(Brqpa)(CN) 3 ]·H 2 O (2) with Mn Schiff base Mn(5-Xsalen) + cations. These compounds include [Fe(Xqpa)(CN) 3 ][Mn(5-Ysalen)]·pMeOH·qH 2 O [qpaH 2 = N-(quinolin-8-yl)picolinamide; salen = N,N'-ethylenebis(salicylideneiminato) dianion; X = Cl, Y = H (3); X = Cl, Y = Br (4); X = Br, Y = H (5); X = Br, Y = F (6); X = Br, Y = Cl (7); X = Br, Y = Br (8)]. When precursor 1 was used, compounds 3 and 4 were isolated to give a dinuclear entity and a linear chain structure, respectively. The reaction of precursor 2 with the Schiff bases afforded four linear Fe(iii)-Mn(iii) chain complexes. Chain chirality with P- and M-helicity emerges in 4, 7, and 8, while 5 exhibits chain helicity opposite to the previous chain complexes and 6 presents no chain helicity. Such a structural feature is heavily dependent on the interchain π-π contacts and the Fe precursor bridging unit. Chiral induction from a local ethylenediamine link of Y-salen is propagated over the chain via noncovalent π-π interactions. All the bimetallic compounds show antiferromagnetic interactions transmitted by the cyanide linkage. A field-induced metamagnetic transition is involved in 4, 7, and 8, while a field-induced two-step transition is evident in 6. From a magnetostructural viewpoint, the coupling constant is primarily governed by the Mn-N ax -C ax angle (ax = axial) in the bimetallic chain complexes composed of mer-Fe(iii) tricyanides, although the torsion angle plays a role.

Magneto-structural correlation in a series of bimetallic alternating chain complexes of [CrIIIL(CN)4]n[MnIII(salpn)]n.nsolvents (L=2,2'-bipy or 9,10-phen, salpn=substituted salicyldehyde, solvents=water and methanol).

PubMed

Pan, Feng; Wang, Zhe-Ming; Gao, Song

2007-11-26

Five chain compounds based on the building block of [Cr(L)(CN)4]- (L=2,2'-bipy, 1-4; L=9,10-phen, 5) and [Mn(salpn)]+ (salpn=substituted salicyldehyde-type Schiff base in Scheme 1) have been prepared and characterized structurally and magnetically. The four compounds (1-4) consisting of [Cr(bipy)(CN)4]- units possess straight bimetallic chains as the [Cr(bpy)(CN)4]- unit links the two neighbor [Mn(salpn)]+ units with the two trans-cyanide ligands, while in 5 the chain is zigzag because the [Cr(phen)(CN)4]- unit connects the [Mn(salpn)]+ units with its two cis-cyanide ligands. The bond angles of Mn-N-C-Cr are adjusted by different coligands of salpn and bipy/phen. The chains are stacking via mainly the aromatic pi-pi-type interactions. All compounds show 3D antiferromagnetic ordering with Néel temperatures ranging from 3.7 to 8.1 K, and they are metamagnets displaying antiferromagnetic to ferrimagnetic transition at critical fields of 4.0-13.1 kOe at 1.9 K. This is due to weak interchain antiferromagnetic interactions between the ferrimagnetic bimetallic chains in the materials. The intrachain couplings (J, in cm(-1)) in the materials, between cyanide-bridged CrIII and MnIII ions, from -1.84 to -5.35 cm(-1), follow a linear relationship (J=-33+0.18alpha) to the Mn-N-C angles (alpha, in deg). In addition, the weak interchain antiferromagnetic interactions and critical fields for antiferromagnetic-ferrimagnetic transition are closely related to some of their structural factors, which were studied very superficially only referring to the separations of nearest chains in each material.

Membrane Disruption Mechanism of a Prion Peptide (106-126) Investigated by Atomic Force Microscopy, Raman and Electron Paramagnetic Resonance Spectroscopy.

PubMed

Pan, Jianjun; Sahoo, Prasana K; Dalzini, Annalisa; Hayati, Zahra; Aryal, Chinta M; Teng, Peng; Cai, Jianfeng; Rodriguez Gutierrez, Humberto; Song, Likai

2017-05-18

A fragment of the human prion protein spanning residues 106-126 (PrP106-126) recapitulates many essential properties of the disease-causing protein such as amyloidogenicity and cytotoxicity. PrP106-126 has an amphipathic characteristic that resembles many antimicrobial peptides (AMPs). Therefore, the toxic effect of PrP106-126 could arise from a direct association of monomeric peptides with the membrane matrix. Several experimental approaches are employed to scrutinize the impacts of monomeric PrP106-126 on model lipid membranes. Porous defects in planar bilayers are observed by using solution atomic force microscopy. Adding cholesterol does not impede defect formation. A force spectroscopy experiment shows that PrP106-126 reduces Young's modulus of planar lipid bilayers. We use Raman microspectroscopy to study the effect of PrP106-126 on lipid atomic vibrational dynamics. For phosphatidylcholine lipids, PrP106-126 disorders the intrachain conformation, while the interchain interaction is not altered; for phosphatidylethanolamine lipids, PrP106-126 increases the interchain interaction, while the intrachain conformational order remains similar. We explain the observed differences by considering different modes of peptide insertion. Finally, electron paramagnetic resonance spectroscopy shows that PrP106-126 progressively decreases the orientational order of lipid acyl chains in magnetically aligned bicelles. Together, our experimental data support the proposition that monomeric PrP106-126 can disrupt lipid membranes by using similar mechanisms found in AMPs.

Membrane Disruption Mechanism of a Prion Peptide (106-126) Investigated by Atomic Force Microscopy, Raman and Electron Paramagnetic Resonance Spectroscopy

PubMed Central

Pan, Jianjun; Sahoo, Prasana K.; Dalzini, Annalisa; Hayati, Zahra; Aryal, Chinta M.; Teng, Peng; Cai, Jianfeng; Gutierrez, Humberto Rodriguez; Song, Likai

2018-01-01

A fragment of the human prion protein spanning residues 106-126 (PrP106-126) recapitulates many essential properties of the disease-causing protein such as amyloidogenicity and cytotoxicity. PrP106-126 has an amphipathic characteristic that resembles many antimicrobial peptides (AMPs). Therefore, the toxic effect of PrP106-126 could arise from a direct association of monomeric peptides with membrane matrix. Several experimental approaches are employed to scrutinize the impacts of monomeric PrP106-126 on model lipid membranes. Porous defects in planar bilayers are observed by using solution atomic force microscopy. Adding cholesterol does not impede defect formation. Force spectroscopy experiment shows that PrP106-126 reduces Young’s modulus of planar lipid bilayers. We use Raman microspectroscopy to study the effect of PrP106-126 on lipid vibrational dynamics. For phosphatidylcholine lipids, PrP106-126 disorders the intra-chain conformation, while the inter-chain interaction is not altered; for phosphatidylethanolamine lipids, PrP106-126 increases the inter-chain interaction, while the intra-chain conformational order remains similar. We explain the observed differences by considering different modes of peptide insertion. Finally, electron paramagnetic resonance spectroscopy shows that PrP106-126 progressively decreases the orientational order of lipid acyl chains in magnetically aligned bicelles. Together, our experimental data support the proposition that monomeric PrP106-126 can disrupt lipid membranes by using similar mechanisms found in AMPs. PMID:28459565

Interchain coupled chain dynamics of poly(ethylene oxide) in blends with poly(methyl methacrylate): coupling model analysis.

PubMed

Ngai, K L; Wang, Li-Min

2011-11-21

Quasielastic neutron scattering and molecular dynamics simulation data from poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blends found that for short times the self-dynamics of PEO chain follows the Rouse model, but at longer times past t(c) = 1-2 ns it becomes slower and departs from the Rouse model in dependences on time, momentum transfer, and temperature. To explain the anomalies, others had proposed the random Rouse model (RRM) in which each monomer has different mobility taken from a broad log-normal distribution. Despite the success of the RRM, Diddens et al. [Eur. Phys. Lett. 95, 56003 (2011)] extracted the distribution of friction coefficients from the MD simulations of a PEO/PMMA blend and found that the distribution is much narrower than expected from the RRM. We propose a simpler alternative explanation of the data by utilizing alone the observed crossover of PEO chain dynamics at t(c). The present problem is just a special case of a general property of relaxation in interacting systems, which is the crossover from independent relaxation to coupled many-body relaxation at some t(c) determined by the interaction potential and intermolecular coupling/constraints. The generality is brought out vividly by pointing out that the crossover also had been observed by neutron scattering from entangled chains relaxation in monodisperse homopolymers, and from the segmental α-relaxation of PEO in blends with PMMA. The properties of all the relaxation processes in connection with the crossover are similar, despite the length scales of the relaxation in these systems are widely different.

Interchain coupled chain dynamics of poly(ethylene oxide) in blends with poly(methyl methacrylate): Coupling model analysis

NASA Astrophysics Data System (ADS)

Ngai, K. L.; Wang, Li-Min

2011-11-01

Quasielastic neutron scattering and molecular dynamics simulation data from poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) blends found that for short times the self-dynamics of PEO chain follows the Rouse model, but at longer times past tc = 1-2 ns it becomes slower and departs from the Rouse model in dependences on time, momentum transfer, and temperature. To explain the anomalies, others had proposed the random Rouse model (RRM) in which each monomer has different mobility taken from a broad log-normal distribution. Despite the success of the RRM, Diddens et al. [Eur. Phys. Lett. 95, 56003 (2011)] extracted the distribution of friction coefficients from the MD simulations of a PEO/PMMA blend and found that the distribution is much narrower than expected from the RRM. We propose a simpler alternative explanation of the data by utilizing alone the observed crossover of PEO chain dynamics at tc. The present problem is just a special case of a general property of relaxation in interacting systems, which is the crossover from independent relaxation to coupled many-body relaxation at some tc determined by the interaction potential and intermolecular coupling/constraints. The generality is brought out vividly by pointing out that the crossover also had been observed by neutron scattering from entangled chains relaxation in monodisperse homopolymers, and from the segmental α-relaxation of PEO in blends with PMMA. The properties of all the relaxation processes in connection with the crossover are similar, despite the length scales of the relaxation in these systems are widely different.

Exciton transport in π-conjugated polymers with conjugation defects.

PubMed

Meng, Ruixuan; Li, Yuan; Li, Chong; Gao, Kun; Yin, Sun; Wang, Luxia

2017-09-20

In π-conjugated polymers for photovoltaic applications, intrinsic conjugation defects are known to play crucial roles in impacting exciton transport after photoexcitation. However, the understanding of the associated microscopic processes still remains limited. Here, we present a theoretical investigation of the effects of different conjugation defects on the dynamics of exciton transport in two linearly coupled poly(p-phenylene vinylene) (PPV) molecules. The model system is constructed by employing an extended version of the Su-Schrieffer-Heeger model and the exciton behaviors are simulated by means of a quantum nonadiabatic dynamics. We identify two types of conjugation defects, i.e., weakening conjugation and strengthening conjugation, which are demonstrated to play different roles in impacting the dynamics of exciton transport in the system. The weakening conjugation acts as an energy well inclined to trap a moving exciton, while the strengthening conjugation acts as an energy barrier inclined to block the exciton. We also systematically simulate both intrachain and interchain dynamics of exciton transport, and find that an exciton could experience a "short-time delaying", "trapping", "blocking", or "hopping" process, which is determined by the defect type, strength, and position. These findings provide a microscopic understanding of how the exciton transport dynamics can be impacted by conjugation defects in an actual polymer system.

Rupture luminescence from natural fibers

NASA Astrophysics Data System (ADS)

Li, W.; Haneman, D.

1999-12-01

Fibers of cotton and wool, and samples of paper, have been ruptured in tension in vacuum and in air, and give detectable luminescence in the visible range. All have a common emission peak at around 2.0 eV, which is ascribed to the deexcitation of states excited by the rupture of organic chain molecule bonds. Rubber bands give stronger emission in air, but no emission in vacuum, suggesting the material breaks only at weak interchain bonds. Mohair, cat, and horse hair also give emission in air. The phenomena reveal effects that would occur widely in nature.

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

Kung, Y. F.; Bazin, C.; Wohlfeld, K.

Using determinant quantum Monte Carlo (DQMC) simulations, we systematically study the doping dependence of the crossover from one to two dimensions and its impact on the magnetic properties of the Hubbard model. A square lattice of chains is used, in which the dimensionality can be tuned by varying the interchain coupling t ⊥. The dynamical spin structure factor and static quantities, such as the static spin susceptibility and nearest-neighbor spin correlation function, are characterized in the one- and two-dimensional limits as a benchmark. When the dimensionality is tuned between these limits, the magnetic properties, while evolving smoothly from one tomore » two dimensions, drastically change regardless of the doping level. This suggests that the spin excitations in the two-dimensional Hubbard model, even in the heavily doped case, cannot be explained using the spinon picture known from one dimension. In conclusion, the DQMC calculations are complemented by cluster perturbation theory studies to form a more complete picture of how the crossover occurs as a function of doping and how doped holes impact magnetic order.« less

Disorder-induced Revival of the Bose-Einstein Condensation at High Magnetic Fields in Ni(Cl1-xBrx)2- 4SC(NH2)2

NASA Astrophysics Data System (ADS)

Laflorencie, Nicolas; Dupont, Maxime; Capponi, Sylvain

Building on recent NMR experiments, we theoretically investigate the high magnetic field regime of the disordered quasi-one-dimensional S = 1 antiferromagnetic material Ni(Cl1-xBrx)2- 4SC(NH2)2. The interplay between disorder, chemically controlled by Br-doping, interactions, and the external magnetic field, leads to a very rich phase diagram. Beyond the well-known antiferromagnetically ordered regime, analog of a Bose condensate of magnons, which disappears when H >= 12 . 3 T, we unveil a resurgence of phase coherence at higher field H 13 . 6 T, induced by the doping. Interchain couplings stabilize finite temperature long-range order whose extension in the field - temperature space is governed by the concentration of impurities x. Such a ``mini-condensation'' contrasts with previously reported Bose-glass physics in the same regime by Yu et al., and should be accessible to future experiments. Work supported by the French ANR program BOLODISS and by Region Midi-Pyrenees.

Symmetry protected topological Luttinger liquids and the phase transition between them

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

None

2018-01-01

We show that a doped spin-1/2 ladder with antiferromagnetic intra-chain and ferromagnetic inter-chain coupling is a symmetry protected topologically non-trivial Luttinger liquid. Turning on a large easy-plane spin anisotropy drives the system to a topologically-trivial Luttinger liquid. Both phases have full spin gaps and exhibit power-law superconducting pair correlation. The Cooper pair symmetry is singletmore » $$d_{xy}$$ in the non-trivial phase and triplet $$S_z=0$$ in the trivial phase. The topologically non-trivial Luttinger liquid exhibits gapless spin excitations in the presence of a boundary, and it has no non-interacting or mean-field theory analog even when the fluctuating phase in the charge sector is pinned. As a function of the strength of spin anisotropy there is a topological phase transition upon which the spin gap closes. We speculate these Luttinger liquids are relevant to the superconductivity in metalized integer spin ladders or chains.« less

Large exchange anisotropy in quasi-one-dimensional spin-1/2 fluoride antiferromagnets with a d (z2)1 ground state

NASA Astrophysics Data System (ADS)

Kurzydłowski, D.; Grochala, W.

2017-10-01

Hybrid density functional calculations are performed for a variety of systems containing d9 ions (C u2 + and A g2 + ) and exhibiting quasi-one-dimensional magnetic properties. In particular, we study fluorides containing these ions in a rarely encountered compressed octahedral coordination that forces the unpaired electron into the local d (z2) orbital. We predict that such systems should exhibit exchange anisotropies surpassing that of S r2Cu O3 , one of the best realizations of a one-dimensional system known to date. In particular, we predict that the interchain coupling in the A g2 + -containing [AgF ] [B F4 ] system should be nearly four orders of magnitude smaller than the intrachain interaction. Our results indicate that quasi-one-dimensional spin-1/2 systems containing chains with spin sites in the d (z2)1 local ground state could constitute a versatile model for testing modern theories of quantum many-body physics in the solid state.

The nature of hydrogen-bonding interactions in nonsteroidal anti-inflammatory drugs revealed by polarized IR spectroscopy

NASA Astrophysics Data System (ADS)

Hachuła, Barbara

2018-01-01

The influence of hydrogen-bonding interactions in the solid phase on the IR spectroscopic pattern of the νOsbnd H band of nonsteroidal anti-inflammatory drugs (NSAIDs) was studied experimentally by IR spectroscopy with the use of polarized light at two temperatures (293 K and 77 K) and in isotopic dilution. The neat and deuterated crystals of (S)-naproxen ((S)-NPX), (R)-flurbiprofen ((R)-FBP), (RS)-flurbiprofen ((RS)-FBP) and (RS)-ketoprofen ((RS)-KTP) were obtained by melt crystallization between the two squeezed CaF2 plates. The vibrational spectra of selected α-aryl propionic acid derivatives (2APAs) reflected the characteristics of their hydrogen-bond networks, i.e., 2APAs were characterized by the chain ((S)-NPX, (R)-FBP) and by dimeric ((RS)-FBP, (RS)-KTP) arrangement of hydrogen bonds in the crystal lattice. Spectroscopic results showed that the interchain (through-space) exciton coupling, between two laterally-spaced hydrogen bonds, dominates in the crystals of four NSAIDs. The same exciton coupled hydrogen bonds were also responsible for the H/D isotopic recognition mechanism in the crystalline spectra of deuterated 2APAs. The presented spectral results may help to predict the hydrogen bond motifs in the crystalline NSAIDs, which structures are not yet known, based on their IR spectra of hydrogen bond in the crystals.

Labeling of monoclonal antibodies with a 67Ga-phenolic aminocarboxylic acid chelate. Part II. Comparison of immunoreactivity and biodistribution of monoclonal antibodies labeled with the 67Ga-chelate or with 131I.

PubMed

Matzku, S; Schuhmacher, J; Kirchgessner, H; Brüggen, J

1986-01-01

Coupling of the 67Ga-P-EDDHA chelate via carbodiimide to the anti-melanoma monoclonal antibody (Mab) M.2.9.4 resulted in a low degree of oligomerization, but a considerable degree of intra-molecular (inter-chain) cross-linking. However, this did not impair immunoreactivity, nor did the half-life in vivo differ substantially from that of 131I-M.2.9.4. Biodistribution analysis in normal mice showed Ga:I ratios near 1 in the blood and other tissues not involved in degradation and label excretion. In tissues of the reticulo-endothelial system (RES) and the kidneys, Ga:I ratios up to 2.51 were reached within 4 days of administration. In antigen-positive MeWo tumor tissue, retention of 67Ga also excreted that of 131I, so that tumor; organ ratios (except tumor:liver) were superior for the 67Ga-labeled MAb. It is concluded that the method of coupling pre-established 67Ga-P-EDDHA chelate to antibody results in a functionally intact tracer molecule, whose persistence in vivo is not significantly impaired. The major difference to I-labeled MAbs may be a prolonged retention of Ga in tissues (cells) physiologically involved in antibody catabolism.

Modification of Side Chains of Conjugated Molecules and Polymers for Charge Mobility Enhancement and Sensing Functionality.

PubMed

Liu, Zitong; Zhang, Guanxin; Zhang, Deqing

2018-06-19

Organic semiconductors have received increasing attentions in recent years because of their promising applications in various optoelectronic devices. The key performance metric for organic semiconductors is charge carrier mobility, which is governed by the electronic structures of conjugated backbones and intermolecular/interchain π-π interactions and packing in both microscopic and macroscopic levels. For this reason, more efforts have been paid to the design and synthesis of conjugated frameworks for organic semiconductors with high charge mobilities. However, recent studies manifest that appropriate modifications of side chains that are linked to conjugated frameworks can improve the intermolecular/interchain packing order and boost charge mobilities. In this Account, we discuss our research results in context of modification of side chains in organic semiconductors for charge mobility enhancement. These include the following: (i) The lengths of alkyl chains in sulfur-rich thiepin-fused heteroacences can dramatically influence the intermolecular arrangements and orbital overlaps, ushering in different hole mobilities. Inversely, the lamellar stacking modes of alkyl chains in naphthalene diimide (NDI) derivatives with tetrathiafulvalene (TTF) units are affected by the structures of conjugated cores. (ii) The steric hindrances owing to the bulky branching chains can be weakened by partial replacement of the branching alkyl chains with linear ones for diketopyrrolopyrrole (DPP)-based D (donor)-A (acceptor) conjugated polymers. Such modification of side chains makes the polymer backbones more planar and thus interchain packing order and charge mobilities are improved. The incorporation of hydrophilic tri(ethylene glycol) (TEG) chains into the polymers also leads to improved interchain packing order. In particular, the polymer in which TEG side chains are distributed uniformly exhibits relatively high charge mobility without thermal annealing. (iii) The incorporation of urea groups in the side chains induces the polymer chains to pack more orderly and form large domains because of the additional H-bonding among urea groups. Accordingly, thin film mobilities of the conjugated D-A polymers with side chains entailing urea groups are largely boosted in comparison with those of polymers of the same backbones with either branching alkyl chains or branching/linear alkyl chains. (iv) The torsions of branching alkyl chains in conjugated D-A polymers can be inhibited to some extent upon incorporation of tiny amount of NMe 4 I in the thin film. As a result, the polymer thin films with NMe 4 I exhibit improved crystallinity, and charge mobilities can be boosted by more than 20 times. (v) Side chains with functional groups in the conjugated polymers can endow the thin film field-effect transistors (FETs) with sensing functionality. FETs with the conjugated polymer with -COOH groups in the side chains show sensitive, selective, and fast responses toward ammonia and amines, while FETs with the ultrathin films of the polymer containing tetra(ethylene glycol) (TEEG) in the side chains can sense alcohol vapors (in particular ethanol vapor) sensitively and selectively with fast response.

Counterion adsorption theory of dilute polyelectrolyte solutions: Apparent molecular weight, second virial coefficient, and intermolecular structure factor

PubMed Central

Muthukumar, M.

2012-01-01

Polyelectrolyte chains are well known to be strongly correlated even in extremely dilute solutions in the absence of additional strong electrolytes. Such correlations result in severe difficulties in interpreting light scattering measurements in the determination of the molecular weight, radius of gyration, and the second virial coefficient of charged macromolecules at lower ionic strengths from added strong electrolytes. By accounting for charge-regularization of the polyelectrolyte by the counterions, we present a theory of the apparent molecular weight, second virial coefficient, and the intermolecular structure factor in dilute polyelectrolyte solutions in terms of concentrations of the polymer and the added strong electrolyte. The counterion adsorption of the polyelectrolyte chains to differing levels at different concentrations of the strong electrolyte can lead to even an order of magnitude discrepancy in the molecular weight inferred from light scattering measurements. Based on counterion-mediated charge regularization, the second virial coefficient of the polyelectrolyte and the interchain structure factor are derived self-consistently. The effect of the interchain correlations, dominating at lower salt concentrations, on the inference of the radius of gyration and on molecular weight is derived. Conditions for the onset of nonmonotonic scattering wave vector dependence of scattered intensity upon lowering the electrolyte concentration and interpretation of the apparent radius of gyration are derived in terms of the counterion adsorption mechanism. PMID:22830728

The effects of vibronic coupling on the photophysics of pi-conjugated oligomers and polymers

NASA Astrophysics Data System (ADS)

Yamagata, Hajime

A theoretical model describing photophysics of pi-conjugated aggregates, such as molecular crystals and polymer thin films, is developed. A Holstein-like Hamiltonian expressed with a multi-particle basis set is used to evaluate absorption and photoluminescence (PL) spectra. An analysis with line strength ratio proves to be a powerful diagnostic tool to obtain additional spectral signatures with which to distinguish H- vs. J-aggregation. For the H-aggregates absorption peak ratio, A 0-0/A 0-1, diminishes as the excitonic coupling increases. Also the PL peak ratio, I 0-0/I 0-1, is zero at T=0K with no disorder and the value increases as temperature and disorder increase. By contrast the J-aggregates show the opposite trends. Furthermore we will show the PL peak ratio provides a direct measurement of the exciton coherence length for a linear J-aggregate and could be expressed as I0-0/I 0-1 = Ncoh/gamma2. We will also show that it is inversely proportional to square root of temperature (T-1/2). Applying our theory to the herringbone style oligoacene molecular crystals, we show the lowest singlet exciton states are highly influenced by charge transfer (CT) states and the well known energetic gap in two polarized absorption spectra, so called Davydov Splitting (DS), is a product of the interaction. We have successfully reproduced the DS for all three oligoacenes without any free parameters. Inspired by the CT contribution in oligoacene crystals, we further develop Wannier-Mott exciton model and apply to disorder-free polydiacetylene (PDA) quantum wires, which have been shown to be extremely emissive. We will show the quantum wire is a J-aggregate and we once again derive the peak ratio and the coherence size relation, I0-0/I 0-1 = kappaNcoh/gamma 2, where kappa is a prefactor close to unity. Typical photophysical properties of polymer pi-stacks such as those occurring in P3HT films are well explained by the simple linear H-aggregate model. However several groups have started seeing more J-like behaviors amongst "improved" (less disordered) polymer films such as increased values of A 0-0/A 0-1 and I 0-0/I 0-1 and higher radiative rates. With the new perception of a single polymer chain being a J-aggregate, we apply our new theory to pi-stack of polymer chains. We call this HJ-aggregate model since the interchain interaction induces H-aggregation. In the study we show a competition between intrachain and interchain interactions that leads to unique photophysical features. The new model is capable of explaining a wide range of polymer systems and most importantly the theory uncovers the mechanism of the improved polymer films; reducing disorder urges increasing intrachain reactions within each chain, thus enhancing more J-like spectral features.

Characterization and Higher-Order Structure Assessment of an Interchain Cysteine-Based ADC: Impact of Drug Loading and Distribution on the Mechanism of Aggregation.

PubMed

Guo, Jianxin; Kumar, Sandeep; Chipley, Mark; Marcq, Olivier; Gupta, Devansh; Jin, Zhaowei; Tomar, Dheeraj S; Swabowski, Cecily; Smith, Jacquelynn; Starkey, Jason A; Singh, Satish K

2016-03-16

The impact of drug loading and distribution on higher order structure and physical stability of an interchain cysteine-based antibody drug conjugate (ADC) has been studied. An IgG1 mAb was conjugated with a cytotoxic auristatin payload following the reduction of interchain disulfides. The 2-D LC-MS analysis shows that there is a preference for certain isomers within the various drug to antibody ratios (DARs). The physical stability of the unconjugated monoclonal antibody, the ADC, and isolated conjugated species with specific DAR, were compared using calorimetric, thermal, chemical denaturation and molecular modeling techniques, as well as techniques to assess hydrophobicity. The DAR was determined to have a significant impact on the biophysical properties and stability of the ADC. The CH2 domain was significantly perturbed in the DAR6 species, which was attributable to quaternary structural changes as assessed by molecular modeling. At accelerated storage temperatures, the DAR6 rapidly forms higher molecular mass species, whereas the DAR2 and the unconjugated mAb were largely stable. Chemical denaturation study indicates that DAR6 may form multimers while DAR2 and DAR4 primarily exist in monomeric forms in solution at ambient conditions. The physical state differences were correlated with a dramatic increase in the hydrophobicity and a reduction in the surface tension of the DAR6 compared to lower DAR species. Molecular modeling of the various DAR species and their conformers demonstrates that the auristatin-based linker payload directly contributes to the hydrophobicity of the ADC molecule. Higher order structural characterization provides insight into the impact of conjugation on the conformational and colloidal factors that determine the physical stability of cysteine-based ADCs, with implications for process and formulation development.

Self-organization of glucose oxidase-polymer surfactant nanoconstructs in solvent-free soft solids and liquids.

PubMed

Sharma, Kamendra P; Zhang, Yixiong; Thomas, Michael R; Brogan, Alex P S; Perriman, Adam W; Mann, Stephen

2014-10-02

An anisotropic glucose oxidase-polymer surfactant nanoconjugate is synthesized and shown to exhibit complex temperature-dependent phase behavior in the solvent-free state. At close to room temperature, the nanoconjugate crystallizes as a mesolamellar soft solid with an expanded interlayer spacing of ca. 12 nm and interchain correlation lengths consistent with alkyl tail-tail and PEO-PEO ordering. The soft solid displays a birefringent spherulitic texture and melts at 40 °C to produce a solvent-free liquid protein without loss of enzyme secondary structure. The nanoconjugate melt exhibits a birefringent dendritic texture below the conformation transition temperature (Tc) of glucose oxidase (58 °C) and retains interchain PEO-PEO ordering. Our results indicate that the shape anisotropy of the protein-polymer surfactant globular building block plays a key role in directing mesolamellar formation in the solvent-free solid and suggests that the microstructure observed in the solvent-free liquid protein below Tc is associated with restrictions in the intramolecular motions of the protein core of the nanoconjugate.

Carrier transport and luminescence properties of nanocomposites of poly[2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene] and dehydrated nanotubes titanic acid.

PubMed

Zhang, Ting; Xu, Zheng; Liu, Ran; Teng, Feng; Wang, Yongsheng; Xu, Xurong

2007-12-01

The carrier transport capability and luminescence efficiency of poly(2-methoxy-5-(2-ethyl hexyloxy)-p-phenylene vinylene) (MEH-PPV) films are enhanced by doping with dehydrated nanotubed titanic acid (DNTA). MEH-PPV molecules, either wrapped on the outer surface of or encapsulated into DNTA pores, have a more open, straighter conformation than undoped molecules, which induces a longer conjugated backbone and stronger interchain interactions, thereby, enhancing carrier mobility. MEH-PPV molecules within DNTA pores have higher exciton recombination efficiency owing to quantum confinement and the antenna effect.

Measurements of amplified spontaneous emission in π-conjugated polymer films with different morphology

NASA Astrophysics Data System (ADS)

Wang, Yuchen; Yang, Xiao; Wang, Ruizhi; Sheng, Chuanxiang

2014-09-01

π-conjugated polymers (PCPs) are attractive candidates as gain media in laser applications due to their high photoluminescence quantum efficiency in broad spectral range. However, the self-absorption of long-lived excited states was considered to be a limitation for achieving more effective organic lasers. Moreover, the morphology of films is found to be crucial to their optical and electrical properties recently. In this work, we studied amplified spontaneous emission (ASE) of a typical PCP, namely, Poly [2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) films with a 10 ns 532 nm pulse laser focused by a cylindrical lens for obtaining an excitation area in the form of a 100 μm wide and 1 cm long stripe. In an as cast MEH-PPV film, the thresholds increase with the temperatures increase due to the thermal torsion and vibration mode shorten the conjugation chain. On the other hand, a MEH-PPV film which is annealed in Nitrogen at 350 K of half hour, the ASE is not observed at both 300 K and 77 K, for annealing will form π- stacks which increase the interchain interaction. Further analysis suggests that interchain excimers instead of intrachain excitons may be more primary to optical properties in annealed MEH-PPV film. Our measurements suggest that the morphology of the film instead of long lived photoexcitation with lifetime sensitive to the temperature is more crucial to threshold of ASE, as well as, to PCPs lasers.

The nature of hydrogen-bonding interactions in nonsteroidal anti-inflammatory drugs revealed by polarized IR spectroscopy.

PubMed

Hachuła, Barbara

2018-01-05

The influence of hydrogen-bonding interactions in the solid phase on the IR spectroscopic pattern of the ν OH band of nonsteroidal anti-inflammatory drugs (NSAIDs) was studied experimentally by IR spectroscopy with the use of polarized light at two temperatures (293K and 77K) and in isotopic dilution. The neat and deuterated crystals of (S)-naproxen ((S)-NPX), (R)-flurbiprofen ((R)-FBP), (RS)-flurbiprofen ((RS)-FBP) and (RS)-ketoprofen ((RS)-KTP) were obtained by melt crystallization between the two squeezed CaF 2 plates. The vibrational spectra of selected α-aryl propionic acid derivatives (2APAs) reflected the characteristics of their hydrogen-bond networks, i.e., 2APAs were characterized by the chain ((S)-NPX, (R)-FBP) and by dimeric ((RS)-FBP, (RS)-KTP) arrangement of hydrogen bonds in the crystal lattice. Spectroscopic results showed that the interchain (through-space) exciton coupling, between two laterally-spaced hydrogen bonds, dominates in the crystals of four NSAIDs. The same exciton coupled hydrogen bonds were also responsible for the H/D isotopic recognition mechanism in the crystalline spectra of deuterated 2APAs. The presented spectral results may help to predict the hydrogen bond motifs in the crystalline NSAIDs, which structures are not yet known, based on their IR spectra of hydrogen bond in the crystals. Copyright © 2017 Elsevier B.V. All rights reserved.

Numerically exploring the 1D-2D dimensional crossover on spin dynamics in the doped Hubbard model

DOE PAGES

Kung, Y. F.; Bazin, C.; Wohlfeld, K.; ...

2017-11-02

Using determinant quantum Monte Carlo (DQMC) simulations, we systematically study the doping dependence of the crossover from one to two dimensions and its impact on the magnetic properties of the Hubbard model. A square lattice of chains is used, in which the dimensionality can be tuned by varying the interchain coupling t ⊥. The dynamical spin structure factor and static quantities, such as the static spin susceptibility and nearest-neighbor spin correlation function, are characterized in the one- and two-dimensional limits as a benchmark. When the dimensionality is tuned between these limits, the magnetic properties, while evolving smoothly from one tomore » two dimensions, drastically change regardless of the doping level. This suggests that the spin excitations in the two-dimensional Hubbard model, even in the heavily doped case, cannot be explained using the spinon picture known from one dimension. In conclusion, the DQMC calculations are complemented by cluster perturbation theory studies to form a more complete picture of how the crossover occurs as a function of doping and how doped holes impact magnetic order.« less

Superconductor-insulator transition in quasi-one-dimensional single-crystal Nb₂PdS₅ nanowires.

PubMed

Ning, Wei; Yu, Hongyan; Liu, Yequn; Han, Yuyan; Wang, Ning; Yang, Jiyong; Du, Haifeng; Zhang, Changjin; Mao, Zhiqiang; Liu, Ying; Tian, Mingliang; Zhang, Yuheng

2015-02-11

Superconductor-insulator transition (SIT) in one-dimensional (1D) nanowires attracts great attention in the past decade and remains an open question since contrasting results were reported in nanowires with different morphologies (i.e., granular, polycrystalline, or amorphous) or environments. Nb2PdS5 is a recently discovered low-dimensional superconductor with typical quasi-1D chain structure. By decreasing the wire diameter in the range of 100-300 nm, we observed a clear SIT with a 1D transport character driven by both the cross-sectional area and external magnetic field. We also found that the upper critical magnetic field (Hc2) decreases with the reduction of nanowire cross-sectional area. The temperature dependence of the resistance below Tc can be described by the thermally activated phase slip (TAPS) theory without any signature of quantum phase slips (QPS). These findings demonstrated that the enhanced Coulomb interactions with the shrinkage of the wire diameter competes with the interchain Josephson-like coupling may play a crucial role on the SIT in quasi-1D system.

Exciton–exciton annihilation as a probe of interchain interactions in PPV–oligomer aggregates

DOE PAGES

Peteanu, Linda A.; Chowdhury, Sanchari; Wildeman, Jurjen; ...

2017-01-20

One measure of exciton mobility in an aggregate is the efficiency of exciton–exciton annihilation (EEA). Both exciton mobilities and EEA are enhanced for aggregate morphologies in which the distances between chromophores and their relative orientations are favorable for Förster energy transfer. Here this principle is applied to gauge the strength of interchain interactions in aggregates of two substituted PPV oligomers of 7 (OPPV7) and 13 (OPPV13) phenylene rings. These are models of the semiconducting conjugated polymer MEH–PPV. The aggregates were formed by adding a poor solvent (methanol or water) to the oligomers dissolved in a good solvent. Aggregates formed frommore » the longer-chain oligomer and/or by addition of the more polar solvent showed the largest contribution of EEA in their emission decay dynamics. This was found to correlate with the degree to which the steady-state emission spectrum of the monomer is altered by aggregation. Furthermore, the wavelength dependence of the EEA signal was also shown to be useful in differentiating emission features due to monomeric and aggregated chains when their spectra overlap significantly.« less

Ab initio modeling of excitonic and charge-transfer states in organic semiconductors: the PTB1/PCBM low band gap system.

PubMed

Borges, Itamar; Aquino, Adélia J A; Köhn, Andreas; Nieman, Reed; Hase, William L; Chen, Lin X; Lischka, Hans

2013-12-11

A detailed quantum chemical simulation of the excitonic and charge-transfer (CT) states of a bulk heterojunction model containing poly(thieno[3,4-b]thiophene benzodithiophene) (PTB1)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is reported. The largest molecular model contains two stacked PTB1 trimer chains interacting with C60 positioned on top of and lateral to the (PTB1)3 stack. The calculations were performed using the algebraic diagrammatic construction method to second order (ADC(2)). One main result of the calculations is that the CT states are located below the bright inter-chain excitonic state, directly accessible via internal conversion processes. The other important aspects of the calculations are the formation of discrete bands of CT states originating from the lateral C60's and the importance of inter-chain charge delocalization for the stability of the CT states. A simple model for the charge separation step is also given, revealing the energetic feasibility of the overall photovoltaic process.

Exciton-Exciton Annihilation as a Probe of Interchain Interactions in PPV-Oligomer Aggregates.

PubMed

Peteanu, Linda A; Chowdhury, Sanchari; Wildeman, Jurjen; Sfeir, Matthew Y

2017-02-23

One measure of exciton mobility in an aggregate is the efficiency of exciton-exciton annihilation (EEA). Both exciton mobilities and EEA are enhanced for aggregate morphologies in which the distances between chromophores and their relative orientations are favorable for Förster energy transfer. Here this principle is applied to gauge the strength of interchain interactions in aggregates of two substituted PPV oligomers of 7 (OPPV7) and 13 (OPPV13) phenylene rings. These are models of the semiconducting conjugated polymer MEH-PPV. The aggregates were formed by adding a poor solvent (methanol or water) to the oligomers dissolved in a good solvent. Aggregates formed from the longer-chain oligomer and/or by addition of the more polar solvent showed the largest contribution of EEA in their emission decay dynamics. This was found to correlate with the degree to which the steady-state emission spectrum of the monomer is altered by aggregation. The wavelength dependence of the EEA signal was also shown to be useful in differentiating emission features due to monomeric and aggregated chains when their spectra overlap significantly.

Single-crystal EPR spectra of the first alternating bimetallic chain compound MnCu(obp)(H2O)3·H2O (obp=oxamido bis(n,n‧-propionato))

NASA Astrophysics Data System (ADS)

Gatteschi, Dante; Zanchini, Claudia; Kahn, Olivier; Pei, Yu

1989-08-01

Single-crystal EPR spectra of the heterobimetallic alternating double-chain compound MnCu(obp) (H 2O) 3·H 2O (obp=oxamido bis (N,N'-propionato)) were recorded in the 300-20 K range. Analysis of the spectra indicate a substantially dipolar-determined linewidth with enhancement of the secular term of the second moment due to spin diffusion effects. The anisotropic shifts in the resonance field observed in low-temperature spectra revealed that interchain interactions are relevant in determining the preferred spin orientations.

Structure and thermodynamic properties of (C5H12N)CuBr3: a new weakly coupled antiferromagnetic spin-1/2 chain complex lying in the 1D-3D dimensional cross-over regime.

PubMed

Pan, Bingying; Wang, Yang; Zhang, Lijuan; Li, Shiyan

2014-04-07

Single crystals of a metal organic complex (C5H12N)CuBr3 (C5H12N = piperidinium, pipH for short) have been synthesized, and the structure was determined by single-crystal X-ray diffraction. (pipH)CuBr3 crystallizes in the monoclinic group C2/c. Edging-sharing CuBr5 units link to form zigzag chains along the c axis, and the neighboring Cu(II) ions with spin-1/2 are bridged by bibromide ions. Magnetic susceptibility data down to 1.8 K can be well fitted by the Bonner-Fisher formula for the antiferromagnetic spin-1/2 chain, giving the intrachain magnetic coupling constant J ≈ -17 K. At zero field, (pipH)CuBr3 shows three-dimensional (3D) order below TN = 1.68 K. Calculated by the mean-field theory, the interchain coupling constant J' = -0.91 K is obtained and the ordered magnetic moment m0 is about 0.23 μB. This value of m0 makes (pipH)CuBr3 a rare compound suitable to study the 1D-3D dimensional cross-over problem in magnetism, since both 3D order and one-dimensional (1D) quantum fluctuations are prominent. In addition, specific heat measurements reveal two successive magnetic transitions with lowering temperature when external field μ0H ≥ 3 T is applied along the a' axis. The μ0H-T phase diagram of (pipH)CuBr3 is roughly constructed.

Inhibition of botulinum neurotoxins interchain disulfide bond reduction prevents the peripheral neuroparalysis of botulism.

PubMed

Zanetti, Giulia; Azarnia Tehran, Domenico; Pirazzini, Marcon; Binz, Thomas; Shone, Clifford C; Fillo, Silvia; Lista, Florigio; Rossetto, Ornella; Montecucco, Cesare

2015-12-01

Botulinum neurotoxins (BoNTs) form a growing family of metalloproteases with a unique specificity either for VAMP, SNAP25 or syntaxin. The BoNTs are grouped in seven different serotypes indicated by letters from A to G. These neurotoxins enter the cytosol of nerve terminals via a 100 kDa chain which binds to the presynaptic membrane and assists the translocation of a 50 kDa metalloprotease chain. These two chains are linked by a single disulfide bridge which plays an essential role during the entry of the metalloprotease chain in the cytosol, but thereafter it has to be reduced to free the proteolytic activity. Its reduction is mediated by thioredoxin which is continuously regenerated by its reductase. Here we show that inhibitors of thioredoxin reductase or of thioredoxin prevent the specific proteolysis of VAMP by the four VAMP-specific BoNTs: type B, D, F and G. These compounds are effective not only in primary cultures of neurons, but also in preventing the in vivo mouse limb neuroparalysis. In addition, one of these inhibitors, Ebselen, largely protects mice from the death caused by a systemic injection. Together with recent results obtained with BoNTs specific for SNAP25 and syntaxin, the present data demonstrate the essential role of the thioredoxin-thioredoxin reductase system in reducing the interchain disulfide during the nerve intoxication mechanism of all serotypes. Therefore its inhibitors should be considered for a possible use to prevent botulism and for treating infant botulism. Copyright © 2015 Elsevier Inc. All rights reserved.

Quantum vibrational polarons: Crystalline acetanilide revisited

NASA Astrophysics Data System (ADS)

Hamm, Peter; Edler, Julian

2006-03-01

We discuss a refined theoretical description of the peculiar spectroscopy of crystalline acetanilide (ACN). Acetanilide is a molecular crystal with quasi-one-dimensional chains of hydrogen-bonded units, which is often regarded as a model system for the vibrational spectroscopy of proteins. In linear spectroscopy, the CO stretching (amide I) band of ACN features a double-peak structure, the lower of which shows a pronounced temperature dependence which has been discussed in the context of polaron theory. In nonlinear spectroscopy, both of these peaks respond distinctly differently. The lower-frequency band exhibits the anharmonicity expected from polaron theory, while the higher-frequency band responds as if it were quasiharmonic. We have recently related the response of the higher-frequency band to that of a free exciton [J. Edler and P. Hamm, J. Chem. Phys. 117, 2415 (2002)]. However, as discussed in the present paper, the free exciton is not an eigenstate of the full quantum version of the Holstein polaron Hamiltonian, which is commonly used to describe these phenomena. In order to resolve this issue, we present a numerically exact solution of the Holstein polaron Hamiltonian in one dimension (1D) and 3D. In 1D, we find that the commonly used displaced oscillator picture remains qualitatively correct, even for relatively large exciton coupling. However, the result is not in agreement with the experiment, as it fails to explain the free-exciton band. In contrast, when taking into account the 3D nature of crystalline acetanilide, certain parameter regimes exist where the displaced oscillator picture breaks down and states appear in the spectrum that indeed exhibit the characteristics of a free exciton. The appearance of these states is a speciality of vibrational polarons, whose source of exciton coupling is transition dipole coupling which is expected to have opposite signs of interchain and intrachain coupling.

Cleavage of the interchain disulfide bonds in rituximab increases its affinity for FcγRIIIA.

PubMed

Suzuki, Mami; Yamanoi, Ayaka; Machino, Yusuke; Kobayashi, Eiji; Fukuchi, Kaori; Tsukimoto, Mitsutoshi; Kojima, Shuji; Kohroki, Junya; Akimoto, Kazunori; Masuho, Yasuhiko

2013-07-05

The Fc region of human IgG1 mediates effector function via binding to Fcγ receptors and complement activation. The H and L chains of IgG1 antibodies are joined by four interchain disulfide bonds. In this study, these bonds within the therapeutic IgG1 rituximab (RTX) were cleaved either by mild reduction followed by alkylation or by mild S-sulfonation; consequently, two modified RTXs - A-RTX (alkylated) and S-RTX (S-sulfonated) - were formed, and both were almost as potent as unmodified RTX when binding CD20 antigen. Unexpectedly, each modified RTX had a higher binding affinity for FcγRIIIA (CD16A) than did unmodified RTX. However, S-RTX and A-RTX were each less potent than RTX in an assay of antibody-dependent cellular cytotoxicity (ADCC). In this ADCC assay, each modified RTX showed decreased secretion of granzyme B, but no change in perforin secretion, from effector cells. These results provide significant information on the structures within IgG1 that are involved in binding FcγRIIIA, and they may be useful in the development of therapeutic antagonists for FcγRIIIA. Copyright © 2013 Elsevier Inc. All rights reserved.

Disulfide Bond Formation and ToxR Activity in Vibrio cholerae

PubMed Central

Fengler, Vera H. I.; Boritsch, Eva C.; Tutz, Sarah; Seper, Andrea; Ebner, Hanna; Roier, Sandro; Schild, Stefan; Reidl, Joachim

2012-01-01

Virulence factor production in Vibrio cholerae is complex, with ToxRS being an important part of the regulatory cascade. Additionally, ToxR is the transcriptional regulator for the genes encoding the major outer membrane porins OmpU and OmpT. ToxR is a transmembrane protein and contains two cysteine residues in the periplasmic domain. This study addresses the influence of the thiol-disulfide oxidoreductase system DsbAB, ToxR cysteine residues and ToxR/ToxS interaction on ToxR activity. The results show that porin production correlates with ToxR intrachain disulfide bond formation, which depends on DsbAB. In contrast, formation of ToxR intrachain or interchain disulfide bonds is dispensable for virulence factor production and in vivo colonization. This study further reveals that in the absence of ToxS, ToxR interchain disulfide bond formation is facilitated, whereat cysteinyl dependent homo- and oligomerization of ToxR is suppressed if ToxS is coexpressed. In summary, new insights into gene regulation by ToxR are presented, demonstrating a mechanism by which ToxR activity is linked to a DsbAB dependent intrachain disulfide bond formation. PMID:23144706

Hydrogen-Bonding Network and OH Stretch Vibration of Cellulose: Comparison of Computational Modeling with Polarized IR and SFG Spectra.

PubMed

Lee, Christopher M; Kubicki, James D; Fan, Bingxin; Zhong, Linghao; Jarvis, Michael C; Kim, Seong H

2015-12-10

Hydrogen bonds play critical roles in noncovalent directional interactions determining the crystal structure of cellulose. Although diffraction studies accurately determined the coordinates of carbon and oxygen atoms in crystalline cellulose, the structural information on hydrogen atoms involved in hydrogen-bonding is still elusive. This could be complemented by vibrational spectroscopy; but the assignment of the OH stretch peaks has been controversial. In this study, we performed calculations using density functional theory with dispersion corrections (DFT-D2) for the cellulose Iβ crystal lattices with the experimentally determined carbon and oxygen coordinates. DFT-D2 calculations revealed that the OH stretch vibrations of cellulose are highly coupled and delocalized through intra- and interchain hydrogen bonds involving all OH groups in the crystal. Additionally, molecular dynamics (MD) simulations of a single cellulose microfibril showed that the conformations of OH groups exposed at the microfibril surface are not well-defined. Comparison of the computation results with the experimentally determined IR dichroism of uniaxially aligned cellulose microfibrils and the peak positions of various cellulose crystals allowed unambiguous identification of OH stretch modes observed in the vibrational spectra of cellulose.

Frequency dispersion of sound propagation in Rouse polymer melts via generalized dynamic random phase approximation.

PubMed

Erukhimovich, I Ya; Kudryavtsev, Ya V

2003-08-01

An extended generalization of the dynamic random phase approximation (DRPA) for L-component polymer systems is presented. Unlike the original version of the DRPA, which relates the (LxL) matrices of the collective density-density time correlation functions and the corresponding susceptibilities of concentrated polymer systems to those of the tracer macromolecules and so-called broken-links system (BLS), our generalized DRPA solves this problem for the (5xL) x (5xL) matrices of the coupled susceptibilities and time correlation functions of the component number, kinetic energy and flux densities. The presented technique is used to study propagation of sound and dynamic form-factor in disentangled (Rouse) monodisperse homopolymer melt. The calculated ultrasonic velocity and absorption coefficient reveal substantial frequency dispersion. The relaxation time tau is proportional to the degree of polymerization N, which is N times less than the Rouse time and evidences strong dynamic screening because of interchain interaction. We discuss also some peculiarities of the Brillouin scattering in polymer melts. Besides, a new convenient expression for the dynamic structure function of the single Rouse chain in (q,p) representation is found.

New Mononuclear Cu(II) Complexes and 1D Chains with 4-Amino-4H-1,2,4-triazole

PubMed Central

Dîrtu, Marinela M.; Boland, Yves; Gillard, Damien; Tinant, Bernard; Robeyns, Koen; Safin, Damir A.; Devlin, Eamonn; Sanakis, Yiannis; Garcia, Yann

2013-01-01

The crystal structures of two mononuclear Cu(II) NH2trz complexes [Cu(NH2trz)4(H2O)](AsF6)2 (I) and [Cu(NH2trz)4(H2O)](PF6)2 (II) as well as two coordination polymers [Cu(μ2-NH2trz)2Cl]Cl·H2O (III) and [Cu(μ2-NH2trz)2Cl] (SiF6)0.5·1.5H2O (IV) are presented. Cationic 1D chains with bridging bis-monodentate μ2-coordinated NH2trz and bridging μ2-coordinated chloride ligands are present in III and IV. In these coordination polymers, the Cu(II) ions are strongly antiferromagnetically coupled with J = −128.4 cm−1 for III and J = −143 cm−1 for IV (H = −J∑SiSi+1), due to the nature of the bridges between spin centers. Inter-chain interactions present in the crystal structures were taken into consideration, as well as g factors, which were determined experimentally, for the quantitative modeling of their magnetic properties. PMID:24300095

Evidence for side-chain π-delocalization in a planar substituted benzene: an experimental and theoretical charge density study on 2,5-dimethoxybenzaldehyde thiosemicarbazone.

PubMed

Farrugia, Louis J; Khalaji, Aliakbar Dehno

2011-11-17

The charge density in 2,5-dimethoxybenzaldehyde thiosemicarbazone (1) has been studied experimentally using Mo-K(α) X-ray diffraction at 100 K, and by theory using DFT calculations at the B3LYP/6-311++G(2d,2p) level. The quantum theory of atoms in molecules (QTAIM) was used to investigate the extent of π-delocalization in the thioamide side-chain, which is virtually coplanar with the benzene ring. The experimental and theoretical ellipticity profiles along the bond paths were in excellent agreement, and showed that some of the formal single bonds in the side-chain have significant π-bond character. This view was supported by the magnitudes of the topological bond orders and by the delocalization indices δ(Ω(A), Ω(B)). An orbital decomposition of δ(Ω(A), Ω(B)) demonstrated that there was significant π-character in all the interchain non-H chemical bonds. On the other hand, the source function referenced at the interchain bond critical points could not provide any evidence for π-delocalization, showing instead only limited σ-delocalization between nearest neighbors. Overall, the topological evidence and the atomic graphs of the oxygen atoms did not provide convincing evidence for π-delocalization involving the methoxy substituents.

On the molecular origins of biomass recalcitrance: the interaction network and solvation structures of cellulose microfibrils.

PubMed

Gross, Adam S; Chu, Jhih-Wei

2010-10-28

Biomass recalcitrance is a fundamental bottleneck to producing fuels from renewable sources. To understand its molecular origin, we characterize the interaction network and solvation structures of cellulose microfibrils via all-atom molecular dynamics simulations. The network is divided into three components: intrachain, interchain, and intersheet interactions. Analysis of their spatial dependence and interaction energetics indicate that intersheet interactions are the most robust and strongest component and do not display a noticeable dependence on solvent exposure. Conversely, the strength of surface-exposed intrachain and interchain hydrogen bonds is significantly reduced. Comparing the interaction networks of I(β) and I(α) cellulose also shows that the number of intersheet interactions is a clear descriptor that distinguishes the two allomorphs and is consistent with the observation that I(β) is the more stable form. These results highlight the dominant role of the often-overlooked intersheet interactions in giving rise to biomass recalcitrance. We also analyze the solvation structures around the surfaces of microfibrils and show that the structural and chemical features at cellulose surfaces constrict water molecules into specific density profiles and pair correlation functions. Calculations of water density and compressibility in the hydration shell show noticeable but not drastic differences. Therefore, specific solvation structures are more prominent signatures of different surfaces.

Exploring ways to control the properties of polymer thin films

NASA Astrophysics Data System (ADS)

Clough, Andrew R.

Understanding the causes of deviations from bulk-like properties observed in polymer thin films is of interest both from a fundamental standpoint and in order to tailor the properties of polymer thin films used by industry as coatings and in the production of microelectronic devices. As thicknesses are decreased below 100 nm, interfacial effects start to become important. In addition, a confinement effect occurs when the film thickness becomes comparable to the unperturbed size of the polymer chain. In this thesis, we modify polymer films in a controllable way in order to study how some of these properties may be related and potentially adjusted. One of these properties is the glass transition temperature, which is seen to vary with the film thickness for films thinner than 100 nm. While there appears to be a consensus that the variation is attributable to the interactions the polymer has with the film interfaces, important questions concerning how the observed changes may affect the onset of large scale, liquid-like motions in the films have been seldom investigated. We modify the substrate interface with grafted polymer chains, which is known to instill interfacial slippage, to investigate the relation, if any, between the glass transition temperature and large scale chain motions in the films. As another part of the effort to find ways to control the properties of polymer films, we study the effect of swelling films with solvents of different qualities. Studies have shown that modifying the solvent quality used when preparing films by spin-coating, in which solvent from a polymer solution is rapidly removed to form thin uniform films, can affect some properties by modifying the degree of inter-chain entanglement in the film. As it is often difficult to spin-coat films when the solvent is poor, we investigate whether solvent swelling can also be used to modify this entanglement. We find that solvent swelling is able to modify the degree of entanglement in the films. Most importantly, swelling with a poor solvent allows us to reduce the degree of inter-chain entanglement, bringing the film further from equilibrium.

Side-chain Engineering of Benzo[1,2-b:4,5-b’]dithiophene Core-structured Small Molecules for High-Performance Organic Solar Cells

PubMed Central

Yin, Xinxing; An, Qiaoshi; Yu, Jiangsheng; Guo, Fengning; Geng, Yongliang; Bian, Linyi; Xu, Zhongsheng; Zhou, Baojing; Xie, Linghai; Zhang, Fujun; Tang, Weihua

2016-01-01

Three novel small molecules have been developed by side-chain engineering on benzo[1,2-b:4,5-b’]dithiophene (BDT) core. The typical acceptor-donor-acceptor (A-D-A) structure is adopted with 4,8-functionalized BDT moieties as core, dioctylterthiophene as π bridge and 3-ethylrhodanine as electron-withdrawing end group. Side-chain engineering on BDT core exhibits small but measurable effect on the optoelectronic properties of small molecules. Theoretical simulation and X-ray diffraction study reveal the subtle tuning of interchain distance between conjugated backbones has large effect on the charge transport and thus the photovoltaic performance of these molecules. Bulk-heterojunction solar cells fabricated with a configuration of ITO/PEDOT:PSS/SM:PC71BM/PFN/Al exhibit a highest power conversion efficiency (PCE) of 6.99% after solvent vapor annealing. PMID:27140224

Side-chain Engineering of Benzo[1,2-b:4,5-b']dithiophene Core-structured Small Molecules for High-Performance Organic Solar Cells.

PubMed

Yin, Xinxing; An, Qiaoshi; Yu, Jiangsheng; Guo, Fengning; Geng, Yongliang; Bian, Linyi; Xu, Zhongsheng; Zhou, Baojing; Xie, Linghai; Zhang, Fujun; Tang, Weihua

2016-05-03

Three novel small molecules have been developed by side-chain engineering on benzo[1,2-b:4,5-b']dithiophene (BDT) core. The typical acceptor-donor-acceptor (A-D-A) structure is adopted with 4,8-functionalized BDT moieties as core, dioctylterthiophene as π bridge and 3-ethylrhodanine as electron-withdrawing end group. Side-chain engineering on BDT core exhibits small but measurable effect on the optoelectronic properties of small molecules. Theoretical simulation and X-ray diffraction study reveal the subtle tuning of interchain distance between conjugated backbones has large effect on the charge transport and thus the photovoltaic performance of these molecules. Bulk-heterojunction solar cells fabricated with a configuration of ITO/PEDOT:PSS/SM:PC71BM/PFN/Al exhibit a highest power conversion efficiency (PCE) of 6.99% after solvent vapor annealing.

A triple-bridged azido-Cu(II) chain compound fine-tuned by mixed carboxylate/ethanol linkers displays slow-relaxation and ferromagnetic order: synthesis, crystal structure, magnetic properties and DFT calculations.

PubMed

Liu, Xiangyu; Chen, Sanping; Grancha, Thais; Pardo, Emilio; Ke, Hongshan; Yin, Bing; Wei, Qing; Xie, Gang; Gao, Shengli

2014-11-07

A new azido-Cu(II) compound, [Cu(4-fba)(N3)(C2H5OH)] (4-fba = 4-fluorobenzoic acid) (1), has been synthesized and characterized. The X-ray crystal structure analysis demonstrates that only one crystallographically independent Cu(II) ion in the asymmetric unit of 1 exhibits a stretched octahedral geometry in which two azido N atoms and two carboxylic O atoms locate in the equatorial square, while two ethanol O atoms occupy the apical positions, forming a 1D Cu(II) chain with an alternating triple-bridge of EO-azido, syn,syn-carboxylate, and μ2-ethanol. The title compound consists of ferromagnetically interacting ferromagnetic chains, which exhibit ferromagnetic order (T(c) = 7.0 K). The strong ferromagnetic coupling between adjacent Cu(II) ions within each chain is due to the countercomplementarity of the super-exchange pathways, whereas the ferromagnetic interchain interactions--responsible for the long-range magnetic ordering--are most likely due to the presence of coordinated ethanol molecules establishing hydrogen bonds with neighboring chains. DFT calculations have been performed on compound 1 to offer a qualitative theoretical explanation of the magnetic behavior.

Crystal growth and magnetic anisotropy in the spin-chain ruthenate Na2RuO4

NASA Astrophysics Data System (ADS)

Balodhi, Ashiwini; Singh, Yogesh

2018-02-01

We report single-crystal growth, electrical resistivity ρ , anisotropic magnetic susceptibility χ , and heat capacity Cp measurements on the one-dimensional spin-chain ruthenate Na2RuO4 . We observe variable range hopping (VRH) behavior in ρ (T ) . The magnetic susceptibility with magnetic field perpendicular (χ⊥) and parallel (χ∥) to the spin chains is reported. The magnetic properties are anisotropic with χ⊥>χ∥ in the temperature range of measurements T ≈2 -305 K with χ⊥/χ∥≈1.4 at 305 K. From an analysis of the χ (T ) data we attempt to estimate the anisotropy in the g factor and Van Vleck paramagnetic contribution. An anomaly in χ (T ) and a corresponding step-like anomaly in Cp at TN=37 K confirms long-range antiferromagnetic ordering. This temperature is an order of magnitude smaller than the Weiss temperature θ ≈-250 K and points to suppression of long-range magnetic order due to low dimensionality. A fit of the experimental χ (T ) by a one-dimensional spin-chain model gave an estimate of the intrachain exchange interaction 2 J ≈-85 K and the magnitude of the interchain coupling |2 J⊥|≈3 K.

Depolymerization of cellulose into high-value chemicals by using synergy of zinc chloride hydrate and sulfate ion promoted titania catalyst.

PubMed

Wei, Weiqi; Wu, Shubin

2017-10-01

Experiments for cellulose depolymerization by synergy of zinc chloride hydrate (ZnCl 2 ·RH 2 O) and sulfated titania catalyst (SO 4 2- /TiO 2 ) were investigated in this study. The results showed the introduction of sulfate into the TiO 2 significantly enhanced the catalyst acid amount, especially for Brønsted acid site, which is beneficial for subsequent cellulose depolymerization. ZnCl 2 ·RH 2 O hydrate, only a narrow composition range of water, specifically 3.0≤R≤4.0, can dissolve cellulose, which finally resulted the cellulose with low crystallinity and weak intrachain and interchain hydrogen bond network. Coupling of ZnCl 2 ·RH 2 O hydrate and SO 4 2- /TiO 2 catalyst as a mixed reaction system promoted cellulose depolymerization, and the products can be adjusted by the control of reaction conditions, the low temperature (80-100°C) seemed beneficial for glucose formation (maximal yield 50.5%), and the high temperature (120-140°C) favored to produce levulinic acid (maximal yield 43.1%). Besides, the addition of organic co-solvent making HMF as the main product (maximal yield 38.3%). Copyright © 2017 Elsevier Ltd. All rights reserved.

Site-specific covalent modifications of human insulin by catechol estrogens: Reactivity and induced structural and functional changes

NASA Astrophysics Data System (ADS)

Ku, Ming-Chun; Fang, Chieh-Ming; Cheng, Juei-Tang; Liang, Huei-Chen; Wang, Tzu-Fan; Wu, Chih-Hsing; Chen, Chiao-Chen; Tai, Jung-Hsiang; Chen, Shu-Hui

2016-06-01

Proteins, covalently modified by catechol estrogens (CEs), were identified recently from the blood serum of diabetic patients and referred to as estrogenized proteins. Estrogenization of circulating insulin may occur and affect its molecular functioning. Here, the chemical reactivity of CEs towards specific amino acid residues of proteins and the structural and functional changes induced by the estrogenization of insulin were studied using cyclic voltammetry, liquid chromatography-mass spectrometry, circular dichroism spectroscopy, molecular modeling, and bioassays. Our results indicate that CEs, namely, 2- and 4-hydroxyl estrogens, were thermodynamically and kinetically more reactive than the catechol moiety. Upon co-incubation, intact insulin formed a substantial number of adducts with one or multiple CEs via covalent conjugation at its Cys 7 in the A or B chain, as well as at His10 or Lys29 in the B chain. Such conjugation was coupled with the cleavage of inter-chain disulfide linkages. Estrogenization on these sites may block the receptor-binding pockets of insulin. Insulin signaling and glucose uptake levels were lower in MCF-7 cells treated with modified insulin than in cells treated with native insulin. Taken together, our findings demonstrate that insulin molecules are susceptible to active estrogenization, and that such modification may alter the action of insulin.

Crystal and Molecular Structure of a Collagen-Like Peptide at 1.9 overset{circ}{A} Resolution

NASA Astrophysics Data System (ADS)

Bella, Jordi; Eaton, Mark; Brodsky, Barbara; Berman, Helen M.

1994-10-01

The structure of a protein triple helix has been determined at 1.9 angstrom resolution by x-ray crystallographic studies of a collagen-like peptide containing a single substitution of the consensus sequence. This peptide adopts a triple-helical structure that confirms the basic features determined from fiber diffraction studies on collagen: supercoiling of polyproline II helices and interchain hydrogen bonding that follows the model II of Rich and Crick. In addition, the structure provides new information concerning the nature of this protein fold. Each triple helix is surrounded by a cylinder of hydration, with an extensive hydrogen bonding network between water molecules and peptide acceptor groups. Hydroxyproline residues have a critical role in this water network. The interaxial spacing of triple helices in the crystal is similar to that in collagen fibrils, and the water networks linking adjacent triple helices in the crystal structure are likely to be present in connective tissues. The breaking of the repeating (X-Y-Gly)_n pattern by a Gly-->Ala substitution results in a subtle alteration of the conformation, with a local untwisting of the triple helix. At the substitution site, direct interchain hydrogen bonds are replaced with interstitial water bridges between the peptide groups. Similar conformational changes may occur in Gly-->X mutated collagens responsible for the diseases osteogenesis imperfecta, chondrodysplasias, and Ehlers-Danlos syndrome IV.

Functionalization-induced changes in the structural and physical properties of amorphous polyaniline: a first-principles and molecular dynamics study.

PubMed

Chen, X P; Liang, Q H; Jiang, J K; Wong, Cell K Y; Leung, Stanley Y Y; Ye, H Y; Yang, D G; Ren, T L

2016-02-09

In this paper, we present a first-principles and molecular dynamics study to delineate the functionalization-induced changes in the local structure and the physical properties of amorphous polyaniline. The results of radial distribution function (RDF) demonstrate that introducing -SO3(-)Na(+) groups at phenyl rings leads to the structural changes in both the intrachain and interchain ordering of polyaniline at shorter distances (≤5 Å). An unique RDF feature in 1.8-2.1 Å regions is usually observed in both the interchain and intrachain RDF profiles of the -SO3(-)Na(+) substituted polymer (i.e. Na-SPANI). Comparative studies of the atom-atom pairs, bond structures, torsion angles and three-dimensional structures show that EB-PANI has much better intrachain ordering than that of Na-SPANI. In addition, investigation of the band gap, density of states (DOS), and absorption spectra indicates that the derivatization at ring do not substantially alter the inherent electronic properties but greatly change the optical properties of polyaniline. Furthermore, the computed diffusion coefficient of water in Na-SPANI is smaller than that of EB-PANI. On the other hand, the Na-SPANI shows a larger density than that of EB-PANI. The computed RDF profiles, band gaps, absorption spectra, and diffusion coefficients are in quantitative agreement with the experimental data.

Removal of a C-terminal serine residue proximal to the inter-chain disulfide bond of a human IgG1 lambda light chain mediates enhanced antibody stability and antibody dependent cell-mediated cytotoxicity

PubMed Central

Shen, Yang; Zeng, Lin; Zhu, Aiping; Blanc, Tim; Patel, Dipa; Pennello, Anthony; Bari, Amtul; Ng, Stanley; Persaud, Kris; Kang, Yun (Kenneth); Balderes, Paul; Surguladze, David; Hindi, Sagit; Zhou, Qinwei; Ludwig, Dale L.; Snavely, Marshall

2013-01-01

Optimization of biophysical properties is a critical success factor for the developability of monoclonal antibodies with potential therapeutic applications. The inter-domain disulfide bond between light chain (Lc) and heavy chain (Hc) in human IgG1 lends structural support for antibody scaffold stability, optimal antigen binding, and normal Fc function. Recently, human IgG1λ has been suggested to exhibit significantly greater susceptibility to reduction of the inter Lc-Hc disulfide bond relative to the same disulfide bond in human IgG1κ. To understand the molecular basis for this observed difference in stability, the sequence and structure of human IgG1λ and human IgG1κ were compared. Based on this Lc comparison, three single mutations were made in the λ Lc proximal to the cysteine residue, which forms a disulfide bond with the Hc. We determined that deletion of S214 (dS) improved resistance of the association between Lc and Hc to thermal stress. In addition, deletion of this terminal serine from the Lc of IgG1λ provided further benefit, including an increase in stability at elevated pH, increased yield from transient transfection, and improved in vitro antibody dependent cell-mediated cytotoxicity (ADCC). These observations support the conclusion that the presence of the terminal serine of the λ Lc creates a weaker inter-chain disulfide bond between the Lc and Hc, leading to slightly reduced stability and a potential compromise in IgG1λ function. Our data from a human IgG1λ provide a basis for further investigation of the effects of deleting terminal serine from λLc on the stability and function of other human IgG1λ antibodies. PMID:23567210

Numerical investigation of electron localization in polymer chains

NASA Astrophysics Data System (ADS)

Paulsson, Magnus; Stafström, Sven

1998-01-01

Using finite-size scaling, we have calculated the localization-delocalization phase diagrams for electronic wave functions in different disordered polymeric systems. The disorder considered here simulates finite polymer chain lengths, breaks in the conjugation, and disorder in an external potential. It is shown that a system of interacting chains, even at rather weak interchain interactions, allows for enough flexibility for the scattered waves to avoid dephasing and localization. Localization and the metal-insulator transition in highly conducting polymers are discussed in view of these results.

The structure of a β-(1→6)-d-glucan from yeast cell walls

PubMed Central

Manners, David J.; Masson, Alan J.; Patterson, James C.; Björndal, Håkan; Lindberg, Bengt

1973-01-01

By selective enzymolysis, or chemical fractionation, a minor polysaccharide component has been isolated from yeast (Saccharomyces cerevisiae) glucan. This minor component has a degree of polymerization of about 130–140, a highly branched structure, and a high proportion of β-(1→6)-glucosidic linkages. The molecules also contain a smaller proportion of β-(1→3)-glucosidic linkages that serve mainly as interchain linkages, but some may also be inter-residue linkages. PMID:4590991

Predictive study of charge transport in disordered semiconducting polymers.

PubMed

Athanasopoulos, Stavros; Kirkpatrick, James; Martínez, Diego; Frost, Jarvist M; Foden, Clare M; Walker, Alison B; Nelson, Jenny

2007-06-01

We present a theoretical study of charge transport in disordered semiconducting polymers that relates the charge mobility to the chemical structure and the physical morphology in a novel multiscale approach. Our studies, focusing on poly(9,9-dioctylfluorene) (PFO), show that the charge mobility is dominated by pathways with the highest interchain charge-transfer rates. We also find that disorder is not always detrimental to charge transport. We find good agreement with experimental time-of-flight mobility data in highly aligned PFO films.

Deuteration as a Means to Tune Crystallinity of Conducting Polymers

DOE PAGES

Jakowski, Jacek; Huang, Jingsong; Garashchuk, Sophya; ...

2017-08-25

The effects of deuterium isotope substitution on conjugated polymer chain stacking of poly(3-hexylthiophene) is studied in this paper experimentally by X-ray diffraction (XRD) in combination with gel permeation chromatography and theoretically using density functional theory and quantum molecular dynamics. For four P3HT materials with different levels of deuteration (pristine, main-chain deuterated, side-chain deuterated, and fully deuterated), the XRD measurements show that main-chain thiophene deuteration significantly reduces crystallinity, regardless of the side-chain deuteration. The reduction of crystallinity due to the main-chain deuteration is a quantum nuclear effect resulting from a static zero-point vibrational energy combined with a dynamic correlation of themore » dipole fluctuations. The quantum molecular dynamics simulations confirm the interchain correlation of the proton–proton and deuteron–deuteron motions but not of the proton–deuteron motion. Thus and finally, isotopic purity is an important factor affecting stability and properties of conjugated polymer crystals, which should be considered in the design of electronic and spintronic devices.« less

Deuteration as a Means to Tune Crystallinity of Conducting Polymers

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

Jakowski, Jacek; Huang, Jingsong; Garashchuk, Sophya

The effects of deuterium isotope substitution on conjugated polymer chain stacking of poly(3-hexylthiophene) is studied in this paper experimentally by X-ray diffraction (XRD) in combination with gel permeation chromatography and theoretically using density functional theory and quantum molecular dynamics. For four P3HT materials with different levels of deuteration (pristine, main-chain deuterated, side-chain deuterated, and fully deuterated), the XRD measurements show that main-chain thiophene deuteration significantly reduces crystallinity, regardless of the side-chain deuteration. The reduction of crystallinity due to the main-chain deuteration is a quantum nuclear effect resulting from a static zero-point vibrational energy combined with a dynamic correlation of themore » dipole fluctuations. The quantum molecular dynamics simulations confirm the interchain correlation of the proton–proton and deuteron–deuteron motions but not of the proton–deuteron motion. Thus and finally, isotopic purity is an important factor affecting stability and properties of conjugated polymer crystals, which should be considered in the design of electronic and spintronic devices.« less

Structural study of quasi-one-dimensional vanadium pyroxene LiVSi{sub 2}O{sub 6} single crystals

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

Ishii, Yuto; Matsushita, Yoshitaka; Oda, Migaku

Single crystals of quasi-one-dimensional vanadium pyroxene LiVSi{sub 2}O{sub 6} were synthesized and the crystal structures at 293 K and 113 K were studied using X-ray diffraction experiments. We found a structural phase transition from the room-temperature crystal structure with space group C2/c to a low-temperature structure with space group P2{sub 1}/c, resulting from a rotational displacement of SiO{sub 4} tetrahedra. The temperature dependence of magnetic susceptibility shows a broad maximum around 116 K, suggesting an opening of the Haldane gap expected for one-dimensional antiferromagnets with S=1. However, an antiferromagnetic long-range order was developed below 24 K, probably caused by amore » weak inter-chain magnetic coupling in the compound. - Graphical abstract: Low temperature crystal structure of LiVSi{sub 2}O{sub 6} and an orbital arrangement within the V-O zig-zag chain along the c-axis. - Highlights: • A low temperature structure of LiVSi{sub 2}O{sub 6} was determined by single crystal X-ray diffraction measurements. • The origin of the structural transition is a rotational displacement of SiO{sub 4} tetrahedra. • The uniform orbital overlap in the V-O zigzag chain makes the system a quasi one-dimensional antiferromagnet.« less

1D spin chain of Cu2+ in Sr3CuPtO6 with possible Haldane physics

NASA Astrophysics Data System (ADS)

Leiner, Jonathan; Oh, Joosung; Kolesnikov, Alexander; Stone, Matthew; Le, Manh Duc; Cheong, Sang-Wook; Park, Je-Geun

Antiferromagnetic spin chain systems have attracted considerable attention since the discovery of fractional spinon excitations in spin-half chain systems and Haldane gap phases in spin-one chain systems. It has been reported from bulk susceptibility and heat capacity measurements that the magnetic Cu2+ ions in Sr3CuPtO6 exhibit S=1/2 Heisenberg spin chain behavior with a substantial amount of AFM interchain coupling. Using the modern time-of-flight inelastic neutron scattering spectrometer SEQUOIA at the SNS, we have probed the magnetic excitation spectrum for a polycrystalline sample of Sr3CuPtO6. Modeling with linear spin wave theory accounts for the major features of the spinwave spectra, including a nondispersive intense magnon band at 8meV. The magnetic excitations broaden considerably as temperature is increased, persisting up to above 100K and displaying a broad transition as previously seen in the susceptibility data. No spin gap is observed in the dispersive spin excitations at low momentum transfer, which we argue is consistent with Haldane physics in an ideal uniform S=1/2 spin-chain system. The work at the IBS CCES (South Korea) was supported by the research program of the Institute for Basic Science (IBS-R009-G1). Research at the Spallation Neutron Source was sponsored by the Scientific User Facilities Division, US Department of Energy.

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

Brambleby, Jamie; Manson, Jamie L.; Goddard, Paul A.

The magnetic ground state of the quasi-one-dimensional spin-1 antiferromagnetic chain is sensitive to the relative sizes of the single-ion anisotropy (D) and the intrachain (J) and interchain (J') exchange interactions. The ratios D/J and J' /J dictate the material's placement in one of three competing phases: a Haldane gapped phase, a quantum paramagnet, and an XY-ordered state, with a quantum critical point at their junction. We have identified [Ni(HF 2)(pyz) 2] SbF 6, where pyz = pyrazine, as a rare candidate in which this behavior can be explored in detail. Combining neutron scattering (elastic and inelastic) in applied magnetic fieldsmore » of up to 10 tesla and magnetization measurements in fields of up to 60 tesla with numerical modeling of experimental observables, we are able to obtain accurate values of all of the parameters of the Hamiltonian [D = 13.3(1) K, J = 10.4(3) K, and J' = 1.4(2) K], despite the polycrystalline nature of the sample. Density-functional theory calculations result in similar couplings (J = 9.2 K, J' = 1.8 K) and predict that the majority of the total spin population resides on the Ni(II) ion, while the remaining spin density is delocalized over both ligand types. Finally, the general procedures outlined in this paper permit phase boundaries and quantum-critical points to be explored in anisotropic systems for which single crystals are as yet unavailable.« less

Radiation inactivation of ricin occurs with transfer of destructive energy across a disulfide bridge

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

Haigler, H.T.; Woodbury, D.J.; Kempner, E.S.

1985-08-01

The ionizing radiation sensitivity of ricin, a disulfide-linked heterodimeric protein, was studied as a model to determine the ability of disulfide bonds to transmit destructive energy. The radiation-dependent loss of A chain enzymatic activity after irradiation of either intact ricin or ricin in which the interchain disulfide bond was disrupted gave target sizes corresponding to the molecular size of dimeric ricin or monomeric A chain, respectively. These results clearly show that a disulfide bond can transmit destructive energy between protein subunits.

Determining single-ion and spatial exchange anisotropies by pulsed-field magnetometry

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

Manson, J. L.; Villa, J. A.; Singleton, John

2017-02-13

The magnetic ground-state of the Q1D S = 1 antiferromagnetic (AFM) chain is sensitive to the single-ion anisotropy (D) and the relative strength of intra- (J) and interchain (J’) exchange interactions. The ratios D/J and J’/J dictate the material’s placement on the phase diagram for which three competing phases are known to theoretically exist: Haldane, XY and quantum paramagnetic. We identified [Ni(HF 2)(pyz) 2]SbF 6 (pyz = pyrazine) as a candidate in which to explore proximity to these phases.

Thin film construction and characterization and gas-sensing performances of a tailored phenylene-thienylene copolymer.

PubMed

Naso, Francesco; Babudri, Francesco; Colangiuli, Donato; Farinola, Gianluca M; Quaranta, Fabio; Rella, Roberto; Tafuro, Raffaele; Valli, Ludovico

2003-07-30

An alternating copolymer, poly(2,5-dioctyloxy-1,4-phenylene-alt-2,5-thienylene), has been synthesized and used in this research. The behavior of the floating film at the air-water interface has been investigated by measuring surface pressure versus area Langmuir isotherms and contemporaneously by reflection spectroscopy and Brewster angle microscopy. The floating films were transferred by the Langmuir-Schäfer (horizontal lifting) method onto various substrates. It is apparent from these analyses that the effective conjugation length is larger than those in other electroactive polymers and that a strong coplanarity and interchain association takes place above all in the floating film on the water surface and in the transferred multilayers. Such films were used as the active layers in resistive chemical gas sensor devices, thus revealing excellent sensitivity toward NO(2), reversibility, and time stability of the response.

Crystal structure and magnetic properties of a unique 3D coordination polymer constructed from flexible aliphatic tricarballylic acid ligands featuring linear trimeric Manganese(II)-based, metal carboxylate chains

NASA Astrophysics Data System (ADS)

Zou, Hua-Hong; Zhang, Shu-Hua; Zeng, Ming-Hua; Zhou, Yan-Ling; Liang, Hong

2008-08-01

A novel linear trimeric-based, Mn(II)-carboxylate chain well separated by long-linking flexible aliphatic tricarballylic acid ligands in a 3D coordination polymer [Mn 3(C 6H 5O 6) 2(H 2O) 4] n ( 1, C 6H 5O 6dbnd CH (COO -)(CH 2COO -) 2, TCA) exhibits low-dimensional antiferromagnetic order at 3.0 K. Such magnetic behavior is arises from the alternate Antiferro-Antiferro-Antiferro' ( J1J1J2) repeating interactions sequence, based on the nature of the binding modes of Mn(II)-carboxylate chain and the effect of interchains arrangement of 1. The reported carboxylate-bridged metal chain systems display a new structurally authenticated example of linear homometallic spin arranged antiferromagnet among metal carboxylates.

Study of montmorillonite nanoparticles and electron beam irradiation interaction of ethylene vinyl acetate (EVA)/de-vulcanized waste rubber thermoplastic composites

NASA Astrophysics Data System (ADS)

Bee, Soo-Tueen; Sin, Lee Tin; Hoe, Tie Teck; Ratnam, C. T.; Bee, Soo Ling; Rahmat, A. R.

2018-05-01

The purpose of this work was to investigate the effects of montmorillonite (MMT) loading level and electron beam irradiation on the physical-mechanical properties and thermal stability of ethylene vinyl acetate (EVA)- devulcanised waste rubber blends. The addition of MMT particles has significantly increased the d-spacing and interchain separation of deflection peak (0 0 2) of MMT particles. This indicates that MMT particles have effectively intercalated in polymer matrix of EVA-devulcanised waste rubber blends. Besides, the application of electron beam irradiation dosages <150 kGy could also significantly induce the effective intercalation effect of MMT particles in polymer matrix by introducing crosslinking networks. The increasing of electron beam irradiation dosages up to 250 kGy has gradually increased the gel content of all EVA-devulcanized rubber blends by inducing the formation of crosslinking networks in polymer matrix. Also, the tensile strength of all EVA-devulcanized waste rubber blends was gradually increased when irradiated up to 150 kGy. This is due to the occurrence of crosslinking networks by irradiation could significantly provide reinforcement effect to polymer matrix by effectively transferring the stress applied on polymer matrix throughout the whole polymer matrix.

Diketopyrrolopyrrole-Based Conjugated Polymer Entailing Triethylene Glycols as Side Chains with High Thin-Film Charge Mobility without Post-Treatments

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

Yang, Si-Fen; Liu, Zi-Tong; Cai, Zheng-Xu

Side chain engineering of conjugated donor-acceptor polymers is a new way to manipulate their optoelectronic properties. Two new diketopyrrolopyrrole (DPP)-terthiophene-based conjugated polymers PDPP3T-1 and PDPP3T-2, with both hydrophilic triethylene glycol (TEG) and hydrophobic alkyl chains, are reported. It is demonstrated that the incorporation of TEG chains has a significant effect on the interchain packing and thin-film morphology with noticeable effect on charge transport. Polymer chains of PDPP3T-1 in which TEG chains are uniformly distributed can self-assemble spontaneously into a more ordered thin film. As a result, the thin film of PDPP3T-1 exhibits high saturated hole mobility up to 2.6 cm(2)more » V-1 s(-1) without any post-treatment. This is superior to those of PDPP3T with just alkyl chains and PDPP3T-2. Moreover, the respective field effect transistors made of PDPP3T-1 can be utilized for sensing ethanol vapor with high sensitivity (down to 100 ppb) and good selectivity.« less

Molecular cloning and biochemical characterization of rabbit factor XI.

PubMed Central

Sinha, Dipali; Marcinkiewicz, Mariola; Gailani, David; Walsh, Peter N

2002-01-01

Human factor XI, a plasma glycoprotein required for normal haemostasis, is a homodimer (160 kDa) formed by a single interchain disulphide bond linking the Cys-321 of each Apple 4 domain. Bovine, porcine and murine factor XI are also disulphide-linked homodimers. Rabbit factor XI, however, is an 80 kDa polypeptide on non-reducing SDS/PAGE, suggesting that rabbit factor XI exists and functions physiologically either as a monomer, as does prekallikrein, a structural homologue to factor XI, or as a non-covalent homodimer. We have investigated the structure and function of rabbit factor XI to gain insight into the relation between homodimeric structure and factor XI function. Characterization of the cDNA sequence of rabbit factor XI and its amino acid translation revealed that in the rabbit protein a His residue replaces the Cys-321 that forms the interchain disulphide linkage in human factor XI, explaining why rabbit factor XI is a monomer in non-reducing SDS/PAGE. On size-exclusion chromatography, however, purified plasma rabbit factor XI, like the human protein and unlike prekallikrein, eluted as a dimer, demonstrating that rabbit factor XI circulates as a non-covalent dimer. In functional assays rabbit factor XI and human factor XI behaved similarly. Both monomeric and dimeric factor XI were detected in extracts of cells expressing rabbit factor XI. We conclude that the failure of rabbit factor XI to form a covalent homodimer due to the replacement of Cys-321 with His does not impair its functional activity because it exists in plasma as a non-covalent homodimer and homodimerization is an intracellular process. PMID:12084014

Salt bridge residues between I-Ak dimer of dimers alpha-chains modulate antigen presentation.

PubMed

Yadati, S; Nydam, T; Demian, D; Wade, T K; Gabriel, J L; Barisas, B G; Wade, W F

1999-03-15

Class II dimers of dimers are predicted to have functional significance in antigen presentation. The putative contact amino acids of the I-Ak class II dimer of dimers have been identified by molecular modeling based on the DR1 crystal structure (Nydam et al., Int. Immunol. 10, 1237,1998). We have previously reported the role in antigen presentation of dimer of dimers contact amino acids located in the C-terminal domains of the alpha- and beta-chains of class II. Our calculations show that residues Ealpha89 and Ralpha145 in the alpha2-domain form an inter alpha-chain salt bridge between pairs of alphabeta-heterodimers. Other residues, Qalpha92 and Nalpha115, may be involved in close association in that part of the alpha-chain. We investigated the role of these amino acids on class II expression and antigen presentation. Class II composed of an Ealpha89K substituted alpha-chain paired with a wt beta-chain exhibited inhibited antigen presentation and expression of alpha-chain serologic epitopes. In contrast, mutation of Ralpha145E had less affect on antigen presentation and did not affect I-Ak serologic epitopes. Interchanging charges of the salt bridge residues by expressing both Ralpha145E and Ealpha89K on the same chain obviated the large negative effect of the Ealpha89K mutation on antigen presentation but not on the serologic epitopes. Our results are similar for those reported for mutation of DR3's inter-chain salt bridge with the exception that double mutants did not moderate the DR3 defect. Interestingly, the amino acids differences between I-A and DR change the location of the inter-chain salt bridges. In DR1 these residues are located at positions Ealpha88 and Kalpha111; in I-Ak these residues are located at position Ealpha89 and Ralpha145. Inter alpha-chain salt bridges are thus maintained in various class II molecules by amino acids located in different parts of the alpha2-domain. This conservation of structure suggests that considerable functional importance may attach to the ionic interactions.

Hofmeister effect on thermo-responsive poly(propylene oxide): Role of polymer molecular weight and concentration.

PubMed

Moghaddam, Saeed Zajforoushan; Thormann, Esben

2016-03-01

Although a vast amount of research has been dedicated to investigate the Hofmeister effect on the stability of polymer solutions, a clear understanding of the role of polymer properties in this phenomenon is still missing. Here, the Hofmeister effect of NaCl (destabilizing) and NaSCN (stabilizing) salts on aqueous solutions of poly(propylene oxide) (PPO) is studied. Four different molecular weights of PPO were investigated, to determine how the variation in the polymer coil size affects the Hofmeister effect. The investigation was further conducted for different PPO concentrations, in order to understand the effect of inter-chain interactions on the response to addition of salt. The temperature-driven phase separation of the solutions was monitored by differential scanning calorimetry, which provides the precise value of the phase separation temperature, as well as the enthalpy change accompanied with the transition. It was observed that increasing the molecular weight weakens the effect of the both salts, which is interpreted in terms of a scaling law between the molecular weight and the accessible surface area of the polymers. Increasing the PPO concentration further diminished the NaCl effect, but amplified the NaSCN effect. This difference is attributed to an electrostatic stabilization mechanism in the case of NaSCN. Copyright © 2015 Elsevier Inc. All rights reserved.

A computer model of molecular arrangement in a n-paraffinic liquid

NASA Astrophysics Data System (ADS)

Vacatello, Michele; Avitabile, Gustavo; Corradini, Paolo; Tuzi, Angela

1980-07-01

A computer model of a bulk liquid polymer was built to investigate the problem of local order. The model is made of C30 n-alkane molecules; it is not a lattice model, but it allows for a continuous variability of torsion angles and interchain distances, subject to realistic intra- and intermolecular potentials. Experimental x-ray scattering curves and radial distribution functions are well reproduced. Calculated properties like end-to-end distances, distribution of torsion angles, radial distribution functions, and chain direction correlation parameters, all indicate a random coil conformation and no tendency to form bundles of parallel chains.

Evidence for SrHo2O4 and SrDy2O4 as model J1-J2 zigzag chain materials

NASA Astrophysics Data System (ADS)

Fennell, A.; Pomjakushin, V. Y.; Uldry, A.; Delley, B.; Prévost, B.; Désilets-Benoit, A.; Bianchi, A. D.; Bewley, R. I.; Hansen, B. R.; Klimczuk, T.; Cava, R. J.; Kenzelmann, M.

2014-06-01

Neutron diffraction and inelastic spectroscopy is used to characterize the magnetic Hamiltonian of SrHo2O4 and SrDy2O4. Through a detailed computation of the crystal-field levels we find site-dependent anisotropic single-ion magnetism in both materials, and diffraction measurements show the presence of strong one-dimensional spin correlations. Our measurements indicate that competing interactions of the zigzag chain, combined with frustrated interchain interactions, play a crucial role in stabilizing spin-liquid type correlations in this series.

Enhanced electrochemical performance of amorphous carbon nanotube-manganese-di-oxide-poly-pyrrole ternary nanohybrid

NASA Astrophysics Data System (ADS)

Pahari, D.; Das, N. S.; Das, B.; Howli, P.; Chattopadhyay, K. K.; Banerjee, D.

2017-12-01

Amorphous carbon nanotubes (a-CNTs) manganese di oxide (MnO2)-poly pyrrole (PPy) ternary nanocomposites have been synthesized by a simple chemical route. The as prepared samples have been characterized with different characterization tools that include field emission scanning and high resolution transmission electron microscopy, Raman, Fourier transformed infrared as well as UV-Vis spectroscopy. The electrochemical performance of all the as prepared pure and hybrid samples have been studied in detail. It has been seen that the ternary hybrid shows efficient electrochemical performance with high value of specific capacitance with good stability even up to 2000 cycles. The superior performance of the hybrid samples can be attributed to the strong synergistic effect between the components resulting electron shuttling along PPy main chains and inter-chain raising built-in continuous conductive network. The ternary composite approach offers an effective solution to enhance the device performance of metal-oxide based supercapacitors for long cycling applications. These studies can well speculate the existence of another supercapacitor hybrid for the use in environment friendly electrode and thus a pollution free nature.

Combining microscopic and macroscopic probes to untangle the single-ion anisotropy and exchange energies in an S =1 quantum antiferromagnet

NASA Astrophysics Data System (ADS)

Brambleby, Jamie; Manson, Jamie L.; Goddard, Paul A.; Stone, Matthew B.; Johnson, Roger D.; Manuel, Pascal; Villa, Jacqueline A.; Brown, Craig M.; Lu, Helen; Chikara, Shalinee; Zapf, Vivien; Lapidus, Saul H.; Scatena, Rebecca; Macchi, Piero; Chen, Yu-sheng; Wu, Lai-Chin; Singleton, John

2017-04-01

The magnetic ground state of the quasi-one-dimensional spin-1 antiferromagnetic chain is sensitive to the relative sizes of the single-ion anisotropy (D ) and the intrachain (J ) and interchain (J') exchange interactions. The ratios D /J and J'/J dictate the material's placement in one of three competing phases: a Haldane gapped phase, a quantum paramagnet, and an X Y -ordered state, with a quantum critical point at their junction. We have identified [Ni (HF2) (pyz) 2] SbF6 , where pyz = pyrazine, as a rare candidate in which this behavior can be explored in detail. Combining neutron scattering (elastic and inelastic) in applied magnetic fields of up to 10 tesla and magnetization measurements in fields of up to 60 tesla with numerical modeling of experimental observables, we are able to obtain accurate values of all of the parameters of the Hamiltonian [D =13.3 (1 ) K, J =10.4 (3 ) K, and J'=1.4 (2 ) K], despite the polycrystalline nature of the sample. Density-functional theory calculations result in similar couplings (J =9.2 K, J'=1.8 K) and predict that the majority of the total spin population resides on the Ni(II) ion, while the remaining spin density is delocalized over both ligand types. The general procedures outlined in this paper permit phase boundaries and quantum-critical points to be explored in anisotropic systems for which single crystals are as yet unavailable.

A chimeric anti-CEA antibody with heavy interchain disulfide bonds deleted: molecular characterization and biodistributions in normal and tumor bearing mice.

PubMed

Neumaier, M; Gaida, F J; Lewis, M R; Hefta, L J; Shively, L E; Raubitschek, A; Shively, J E

1999-01-01

We have deleted the interchain disulfide bonds in a chimeric anti-CEA antibody (chT84.66) by mutating two cysteines in the heavy chain to glycine residues. The resulting antibody delta SSchT84.66 was expressed in high yield in a bioreactor and purified to homogeneity in a single step on an anti-idiotypic antibody affinity column. The molecular size of the antibody was 150 kDa as judged by gel filtration, SDS gel electrophoresis under non-reducing conditions, and MALDI-TOF/MS. The 150 kDa antibody had nearly identical kinetic (Kon = 1.53 x 10(6) M-1 s-1, .koff = 1.14 x 10(-5) s-1) and affinity constants (Kaff = 1.34 x 10(11) M-1) compared to the parent murine (Kaff = 1.25 x 10(11) M-1) and chimeric (Kaff = 1.16 x 10(11) M-1) antibodies when tested on biosensor chips. When delta SSchT84.66 was conjugated to the isothiocynato derivative of DTPA, radiolabeled with 111In, and injected into either normal or nude mice bearing tumor xenografts, it gave nearly identical biodistributions to chT84.66. delta SSchT84.66 and chT84.66 antibodies gave a maximum tumor uptake of 48 and 74% ID/g, and tumor to blood ratios of 5.3 and 6.2 at 48 h, respectively. We conclude that delta SSchT84.66 irreversibly associates into H2L2 dimers after concentration, that the dimers are stable under both the in vitro and in vivo conditions used in this study, and the properties of the antibody are virtually indistinguishable from the parent chT84.66 antibody.

Optimal expression of a Fab-effector fusion protein in Escherichia coli by removing the cysteine residues responsible for an interchain disulfide bond of a Fab molecule.

PubMed

Kang, Hyeon-Ju; Kim, Hye-Jin; Jung, Mun-Sik; Han, Jae-Kyu; Cha, Sang-Hoon

2017-04-01

Development of novel bi-functional or even tri-functional Fab-effector fusion proteins would have a great potential in the biomedical sciences. However, the expression of Fab-effector fusion proteins in Escherichia coli is problematic especially when a eukaryotic effector moiety is genetically linked to a Fab due to the lack of proper chaperone proteins and an inappropriate physicochemical environment intrinsic to the microbial hosts. We previously reported that a human Fab molecule, referred to as SL335, reactive to human serum albumin has a prolonged in vivo serum half-life in rats. We, herein, tested six discrete SL335-human growth hormone (hGH) fusion constructs as a model system to define an optimal Fab-effector fusion format for E. coli expression. We found that one variant, referred to as HserG/Lser, outperformed the others in terms of a soluble expression yield and functionality in that HserG/Lser has a functional hGH bioactivity and possesses an serum albumin-binding affinity comparable to SL335. Our results clearly demonstrated that the genetic linkage of an effector domain to the C-terminus of Fd (V H +C H1 ) and the removal of cysteine (Cys) residues responsible for an interchain disulfide bond (IDB) ina Fab molecule optimize the periplasmic expression of a Fab-effector fusion protein in E. coli. We believe that our approach can contribute the development of diverse bi-functional Fab-effector fusion proteins by providing a simple strategy that enables the reliable expression of a functional fusion proteins in E. coli. Copyright © 2017 European Federation of Immunological Societies. Published by Elsevier B.V. All rights reserved.

Spin-1/2 Heisenberg antiferromagnet on an anisotropic triangular lattice

NASA Astrophysics Data System (ADS)

Starykh, Oleg

2007-03-01

The Triangular lattice spin-1/2 Heisenberg AntiFerromagnet (TAF) is a prototypical model of frustrated quantum magnetism. While it is believed to exhibit long-range order in the isotropic limit, changes such as spatial anisotropy can alter the delicate balance amongst competing ground states. I will describe the static and dynamic properties of the spatially anisotropic TAF, with inter-chain diagonal exchange J' much weaker than the intrachain exchange J. Treating J' as a perturbation of decoupled Heisenberg spin-1/2 chains, I find that the ground state is spontaneously dimerized in a four-fold degenerate zig-zag pattern. This dimerization instability is driven by quantum fluctuations, which are dramatically enhanced here by the frustrated nature of inter-chain exchange. A magnetic field partially relieves frustration, by canting the spins along the field direction, and causes a quantum phase transition into a magnetically-ordered spin-density-wave phase. This is followed by cone and, finally, fully polarized (saturated) phases, as a function of increasing magnetic field. I show that many of these features are in fact observed in experiments on the celebrated material Cs2CuCl4 (J'/J =1/3). I will also discuss the significant modification of the phase diagram by symmetry-breaking anisotropic Dzyaloshinskii-Moriya (DM) interactions, present in this interesting magnet. In addition to static and thermodynamic properties, the proposed ``one-dimensional'' approach offers a compelling explanation of the unusual experimentally measured dynamical structure factor of Cs2CuCl4 in terms of descendants of one-dimensional spinons. Quite generally, I find characteristic features of a momentum-dependent spinon bound state and a dispersing incoherent excitation in the structure factor, in agreement with experiments.

The effect of divalent salt in chondroitin sulfate solutions

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

Aranghel, D., E-mail: daranghe@nipne.ro; Extreme Light Intrastructure Nuclear Physics; Badita, C. R.

Chondroitin-4 sulfate (CS4) is the main glycosaminoglycan extracted from bovine trachea. CS4 play an important role in osteoarthritis treatment, anticoagulant activity, reduces the degradation of cartilage matrix components, reduces necrosis and apoptosis of chondrocytes and reduces the activity of collagenase. Chondroitin sulfate is also responsible for proteoglycans degradation. Chondroitin sulfate can bind calcium ions with different affinities, depending on their sulfation position. The purpose of this study was to determine the structural properties and the influence of Ca{sup 2+} cations. We carried out measurements on CS4 solutions and mixtures of liquid CS4 with Ca{sup 2+} by Small-Angle Neutron Scattering (SANS).more » CS4 have a mass fractal behavior and the addition of a salt (CaCl{sub 2}) in CS4 solutions generates the appearance of a correlation peak due to local ordering between adjacent chains with inter-chain distances between 483 Å and 233 Å for a calcium concentration of 0.01% w/w.« less

The effect of divalent salt in chondroitin sulfate solutions

NASA Astrophysics Data System (ADS)

Aranghel, D.; Badita, C. R.; Radulescu, A.; Moldovan, L.; Craciunescu, O.; Balasoiu, M.

2016-03-01

Chondroitin-4 sulfate (CS4) is the main glycosaminoglycan extracted from bovine trachea. CS4 play an important role in osteoarthritis treatment, anticoagulant activity, reduces the degradation of cartilage matrix components, reduces necrosis and apoptosis of chondrocytes and reduces the activity of collagenase. Chondroitin sulfate is also responsible for proteoglycans degradation. Chondroitin sulfate can bind calcium ions with different affinities, depending on their sulfation position. The purpose of this study was to determine the structural properties and the influence of Ca2+ cations. We carried out measurements on CS4 solutions and mixtures of liquid CS4 with Ca2+ by Small-Angle Neutron Scattering (SANS). CS4 have a mass fractal behavior and the addition of a salt (CaCl2) in CS4 solutions generates the appearance of a correlation peak due to local ordering between adjacent chains with inter-chain distances between 483 Å and 233 Å for a calcium concentration of 0.01% w/w.

Ionic Borate-Based Covalent Organic Frameworks: Lightweight Porous Materials for Lithium-Stable Solid State Electrolytes

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

Black, Hayden T.; Harrison, Katharine Lee

2016-10-01

The synthesis and characterization of the first polyelectrolyte of intrinsic microporosity (PEIM) is described. The novel material was synthesized via reaction between the nitrile group in the polymer backbone and n-butyl lithium, effectively anchoring an imine anion to the porous framework while introducing a mobile lithium counterion. The PEIM was characterized by 13C, 1H, and 7Li NMR experiments, revealing quantitative conversion of the nitrile functionality to the anionic imine. Variable temperature 7Li NMR analysis of the dry PEIM and the electrolyteswollen PEIM revealed that lithium ion transport within the dry PEIM was largely due to interchain hopping of the Limore » + ions, and that the mobility of polymer associated Li + was reduced after swelling in electrolyte solution. Meanwhile, the swollen PEIM supported efficient transport of dissolved Li + within the expanded pores. These results are discussed in the context of developing novel solid or solid-like lithium ion electrolytes using the new PEIM material.« less

Neutron diffraction and μ SR studies of two polymorphs of nickel niobate NiNb 2 O 6

DOE PAGES

Munsie, T. J. S.; Wilson, M. N.; Millington, A.; ...

2017-10-13

Neutron diffraction and muon spin relaxation (μSR) studies are presented in this paper for the newly characterized polymorph of NiNb 2O 6 (β-NiNb 2O 6) with space group P4 2/n and μSR data only for the previously known columbite structure polymorph with space group Pbcn. The magnetic structure of the P4 2/n form was determined from neutron diffraction using both powder and single-crystal data. Powder neutron diffraction determined an ordering wave vector →k=( 1/ 2, 1/ 2, 1/ 2). Single-crystal data confirmed the same →k vector and showed that the correct magnetic structure consists of antiferromagnetically coupled chains running alongmore » the a or b axis in adjacent Ni 2+ layers perpendicular to the c axis, which is consistent with the expected exchange interaction hierarchy in this system. The refined magnetic structure is compared with the known magnetic structures of the closely related trirutile phases, NiSb 2O 6 and NiTa 2O 6. μSR data finds a transition temperature of T N~15K for this system, while the columbite polymorph exhibits a lower T N=5.7(3) K. Our μSR measurements also allowed us to estimate the critical exponent of the order parameter β for each polymorph. We found β =0.25(3) and 0.16(2) for the β and columbite polymorphs, respectively. The single-crystal neutron scattering data give a value for the critical exponent β =0.28(3) for β-NiNb 2O 6, in agreement with the μSR value. While both systems have β values less than 0.3, which is indicative of reduced dimensionality, this effect appears to be much stronger for the columbite system. Finally, in other words, although both systems appear to be well described by S=1 spin chains, the interchain interactions in the β polymorph are likely much larger.« less

Neutron diffraction and μ SR studies of two polymorphs of nickel niobate NiNb2O6

NASA Astrophysics Data System (ADS)

Munsie, T. J. S.; Wilson, M. N.; Millington, A.; Thompson, C. M.; Flacau, R.; Ding, C.; Guo, S.; Gong, Z.; Aczel, A. A.; Cao, H. B.; Williams, T. J.; Dabkowska, H. A.; Ning, F.; Greedan, J. E.; Luke, G. M.

2017-10-01

Neutron diffraction and muon spin relaxation (μ SR ) studies are presented for the newly characterized polymorph of NiNb2O6 (β -NiNb2O6) with space group P4 2/n and μ SR data only for the previously known columbite structure polymorph with space group P b c n . The magnetic structure of the P4 2/n form was determined from neutron diffraction using both powder and single-crystal data. Powder neutron diffraction determined an ordering wave vector k ⃗=(1/2 ,1/2 ,1/2 ) . Single-crystal data confirmed the same k ⃗ vector and showed that the correct magnetic structure consists of antiferromagnetically coupled chains running along the a or b axis in adjacent Ni2 + layers perpendicular to the c axis, which is consistent with the expected exchange interaction hierarchy in this system. The refined magnetic structure is compared with the known magnetic structures of the closely related trirutile phases, NiSb2O6 and NiTa2O6 . μ SR data finds a transition temperature of TN˜15 K for this system, while the columbite polymorph exhibits a lower TN=5.7 (3 ) K. Our μ SR measurements also allowed us to estimate the critical exponent of the order parameter β for each polymorph. We found β =0.25 (3 ) and 0.16(2) for the β and columbite polymorphs, respectively. The single-crystal neutron scattering data give a value for the critical exponent β =0.28 (3 ) for β -NiNb2O6 , in agreement with the μ SR value. While both systems have β values less than 0.3, which is indicative of reduced dimensionality, this effect appears to be much stronger for the columbite system. In other words, although both systems appear to be well described by S =1 spin chains, the interchain interactions in the β polymorph are likely much larger.

Neutron diffraction and μ SR studies of two polymorphs of nickel niobate NiNb 2 O 6

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

Munsie, T. J. S.; Wilson, M. N.; Millington, A.

Neutron diffraction and muon spin relaxation (μSR) studies are presented in this paper for the newly characterized polymorph of NiNb 2O 6 (β-NiNb 2O 6) with space group P4 2/n and μSR data only for the previously known columbite structure polymorph with space group Pbcn. The magnetic structure of the P4 2/n form was determined from neutron diffraction using both powder and single-crystal data. Powder neutron diffraction determined an ordering wave vector →k=( 1/ 2, 1/ 2, 1/ 2). Single-crystal data confirmed the same →k vector and showed that the correct magnetic structure consists of antiferromagnetically coupled chains running alongmore » the a or b axis in adjacent Ni 2+ layers perpendicular to the c axis, which is consistent with the expected exchange interaction hierarchy in this system. The refined magnetic structure is compared with the known magnetic structures of the closely related trirutile phases, NiSb 2O 6 and NiTa 2O 6. μSR data finds a transition temperature of T N~15K for this system, while the columbite polymorph exhibits a lower T N=5.7(3) K. Our μSR measurements also allowed us to estimate the critical exponent of the order parameter β for each polymorph. We found β =0.25(3) and 0.16(2) for the β and columbite polymorphs, respectively. The single-crystal neutron scattering data give a value for the critical exponent β =0.28(3) for β-NiNb 2O 6, in agreement with the μSR value. While both systems have β values less than 0.3, which is indicative of reduced dimensionality, this effect appears to be much stronger for the columbite system. Finally, in other words, although both systems appear to be well described by S=1 spin chains, the interchain interactions in the β polymorph are likely much larger.« less

Helically assembled π-conjugated polymers with circularly polarized luminescence.

PubMed

Watanabe, Kazuyoshi; Akagi, Kazuo

2014-08-01

We review the recent progress in the field of helically assembled π -conjugated polymers, focusing on aromatic conjugated polymers with interchain helical π -stacking that exhibit circularly polarized luminescence (CPL). In Part 1, we discuss optically active polymers with white-colored CPL and the amplification of the circular polarization through liquid crystallinity. In Part 2, we focus on the stimuli-responsive CPL that results from changes in the conformation and aggregation state of π -conjugated molecules and polymers. In Part 3, we discuss the self-assembly of achiral cationic π -conjugated polymers into circularly polarized luminescent supramolecular nanostructures with the aid of other chiral molecules.

The structure of a β-(1→3)-d-glucan from yeast cell walls

PubMed Central

Manners, David J.; Masson, Alan J.; Patterson, James C.

1973-01-01

Yeast glucan as normally prepared by various treatments of yeast (Saccharomyces cerevisiae) cell walls to remove mannan and glycogen is still heterogeneous. The major component (about 85%) is a branched β-(1→3)-glucan of high molecular weight (about 240000) containing 3% of β-(1→6)-glucosidic interchain linkages. The minor component is a branched β-(1→6)-glucan. A comparison of our results with those of other workers suggests that different glucan preparations may differ in the degree of heterogeneity and that the major β-(1→3)-glucan component may vary considerably in degree of branching. PMID:4359920

Isolation, biochemical characterization and antibiofilm effect of a lectin from the marine sponge Aplysina lactuca.

PubMed

Carneiro, Rômulo Farias; Lima, Paulo Henrique Pinheiro de; Chaves, Renata Pinheiro; Pereira, Rafael; Pereira, Anna Luísa; de Vasconcelos, Mayron Alves; Pinheiro, Ulisses; Teixeira, Edson Holanda; Nagano, Celso Shiniti; Sampaio, Alexandre Holanda

2017-06-01

A new lectin was isolated from the marine sponge Aplysina lactuca (ALL) by combining ammonium sulfate precipitation and affinity chromatography on guar gum matrix. ALL showed affinity for the disaccharides α-lactose, β-lactose and lactulose (Ka=12.5, 31.9 and 145.5M -1 , respectively), as well as the glycoprotein porcine stomach mucin. Its hemagglutinating activity was stable in neutral acid pH values and temperatures below 60°C. ALL is a dimeric protein formed by two covalently linked polypeptide chains. The average molecular mass, as determined by Electrospray Ionization Mass Spectrometry (ESI-MS), was 31,810±2Da. ESI-MS data also indicated the presence of three cysteines involved in one intrachain and one interchain disulfide bond. The partial amino acid sequence of ALL was determined by tandem mass spectrometry. Eight tryptic peptides presented similarity with lectin I isolated from Axinella polypoides. Its secondary structure is predominantly β-sheet, as indicated by circular dichroism (CD) spectroscopy. ALL agglutinated gram-positive and gram-negative bacterial cells, and it were able to significantly reduce the biomass of the bacterial biofilm tested at dose- dependent effect. Copyright © 2017 Elsevier B.V. All rights reserved.

Trimerization and Triple Helix Stabilization of the Collagen XIX NC2 Domain*

PubMed Central

Boudko, Sergei P.; Engel, Jürgen; Bächinger, Hans Peter

2008-01-01

The mechanisms of chain selection and assembly of fibril-associated collagens with interrupted triple helices (FACITs) must differ from that of fibrillar collagens, since they lack the characteristic C-propeptide. We analyzed two carboxyl-terminal noncollagenous domains, NC2 and NC1, of collagen XIX as potential trimerization units and found that NC2 forms a stable trimer and substantially stabilizes a collagen triple helix attached to either end. In contrast, the NC1 domain requires formation of an adjacent collagen triple helix to form interchain disulfide bridges. The NC2 domain of collagen XIX and probably of other FACITs is responsible for chain selection and trimerization. PMID:18845531

Strain effects on the anisotropic thermal transport in crystalline polyethylene

NASA Astrophysics Data System (ADS)

He, Jixiong; Kim, Kyunghoon; Wang, Yangchao; Liu, Jun

2018-01-01

Thermal transport in the axial direction of polymers has been extensively studied, while the strain effect on the thermal conductivity, especially in the radial direction, remains unknown. In this work, we calculated the thermal conductivity in the radial direction of a crystalline polyethylene model and simulated the uniaxial strain effect on the thermal conductivity tensor by molecular dynamics simulations. We found a strong size effect of the thermal transport in the radial direction and estimated that the phonon mean free path can be much larger than the prediction from the classic kinetic theory. We also found that the thermal conductivity in the axial direction increases dramatically with strain, while the thermal conductivity in the radial direction decreases with uniaxial strain. We attribute the reduction of thermal conductivity in the radial direction to the decreases in inter-chain van der Waals forces with strains. The facts that the chains in the crystalline polyethylene became stiffer and more ordered along the chain direction could be the reasons for the increasing thermal conductivity in the axial direction during stretching. Besides, we observed longer phonon lifetime in acoustic branches and higher group velocity in optical branches after uniaxial stretching. Our work provides fundamental understandings on the phonon transport in crystalline polymers, the structure-property relationship in crystalline polymers, and the strain effect in highly anisotropic materials.

Remarkable enhancement of charge carrier mobility of conjugated polymer field-effect transistors upon incorporating an ionic additive

PubMed Central

Luo, Hewei; Yu, Chenmin; Liu, Zitong; Zhang, Guanxin; Geng, Hua; Yi, Yuanping; Broch, Katharina; Hu, Yuanyuan; Sadhanala, Aditya; Jiang, Lang; Qi, Penglin; Cai, Zhengxu; Sirringhaus, Henning; Zhang, Deqing

2016-01-01

Organic semiconductors with high charge carrier mobilities are crucial for flexible electronic applications. Apart from designing new conjugated frameworks, different strategies have been explored to increase charge carrier mobilities. We report a new and simple approach to enhancing the charge carrier mobility of DPP-thieno[3,2-b]thiophene–conjugated polymer by incorporating an ionic additive, tetramethylammonium iodide, without extra treatments into the polymer. The resulting thin films exhibit a very high hole mobility, which is higher by a factor of 24 than that of thin films without the ionic additive under the same conditions. On the basis of spectroscopic grazing incidence wide-angle x-ray scattering and atomic force microscopy studies as well as theoretical calculations, the remarkable enhancement of charge mobility upon addition of tetramethylammonium iodide is attributed primarily to an inhibition of the torsion of the alkyl side chains by the presence of the ionic species, facilitating a more ordered lamellar packing of the alkyl side chains and interchain π-π interactions. PMID:27386541

Overexpression of avenin-like b proteins in bread wheat (Triticum aestivum L.) improves dough mixing properties by their incorporation into glutenin polymers.

PubMed

Ma, Fengyun; Li, Miao; Li, Tingting; Liu, Wei; Liu, Yunyi; Li, Yin; Hu, Wei; Zheng, Qian; Wang, Yaqiong; Li, Kexiu; Chang, Junli; Chen, Mingjie; Yang, Guangxiao; Wang, Yuesheng; He, Guangyuan

2013-01-01

Avenin-like b proteins are a small family of wheat storage proteins, each containing 18 or 19 cysteine residues. The role of these proteins, with high numbers of cysteine residues, in determining the functional properties of wheat flour is unclear. In the present study, two transgenic lines of the bread wheat overexpressing avenin-like b gene were generated to investigate the effects of Avenin-like b proteins on dough mixing properties. Sodium dodecyl sulfate sedimentation (SDSS) test and Mixograph analysis of these lines demonstrated that overexpression of Avenin-like b proteins in both transgenic wheat lines significantly increased SDSS volume and improved dough elasticity, mixing tolerance and resistance to extension. These changes were associated with the increased proportion of polymeric proteins due to the incorporation of overexpressed Avenin-like b proteins into the glutenin polymers. The results of this study were critical to confirm the hypothesis that Avenin-like b proteins could be integrated into glutenin polymers by inter-chain disulphide bonds, which could help understand the mechanism behind strengthening wheat dough strength.

Overexpression of Avenin-Like b Proteins in Bread Wheat (Triticum aestivum L.) Improves Dough Mixing Properties by Their Incorporation into Glutenin Polymers

PubMed Central

Ma, Fengyun; Li, Miao; Li, Tingting; Liu, Wei; Liu, Yunyi; Li, Yin; Hu, Wei; Zheng, Qian; Wang, Yaqiong; Li, Kexiu; Chang, Junli; Chen, Mingjie; Yang, Guangxiao; Wang, Yuesheng; He, Guangyuan

2013-01-01

Avenin-like b proteins are a small family of wheat storage proteins, each containing 18 or 19 cysteine residues. The role of these proteins, with high numbers of cysteine residues, in determining the functional properties of wheat flour is unclear. In the present study, two transgenic lines of the bread wheat overexpressing avenin-like b gene were generated to investigate the effects of Avenin-like b proteins on dough mixing properties. Sodium dodecyl sulfate sedimentation (SDSS) test and Mixograph analysis of these lines demonstrated that overexpression of Avenin-like b proteins in both transgenic wheat lines significantly increased SDSS volume and improved dough elasticity, mixing tolerance and resistance to extension. These changes were associated with the increased proportion of polymeric proteins due to the incorporation of overexpressed Avenin-like b proteins into the glutenin polymers. The results of this study were critical to confirm the hypothesis that Avenin-like b proteins could be integrated into glutenin polymers by inter-chain disulphide bonds, which could help understand the mechanism behind strengthening wheat dough strength. PMID:23843964

Improved growth response of antibody/receptor chimera attained by the engineering of transmembrane domain.

PubMed

Kawahara, Masahiro; Ogo, Yuko; Ueda, Hiroshi; Nagamune, Teruyuki

2004-10-01

Structure-based design of antibody/cytokine receptor chimeras has permitted a growth signal transduction in response to non-natural ligands such as fluorescein-conjugated BSA as mimicry of cytokine-cytokine receptor systems. However, while tight on/off regulation is observed in the natural cytokine receptor systems, many chimeras constructed to date showed residual growth-promoting activity in the absence of ligands. Here we tried to reduce the basal growth signal intensity from a chimera by engineering the transmembrane domain (TM) that is thought to be involved in the interchain interaction of natural cytokine receptors. When the retroviral vectors encoding the chimeras with either the wild-type erythropoietin receptor (EpoR) TM or the one bearing two mutations in the leucine zipper motif were transduced to non-strictly interleukin-6-dependent 7TD1 cells, a tight antigen-dependent on/off regulation was attained, also demonstrating the first antigen-mediated genetically modified cell amplification of non-strictly factor-dependent cells. The results clearly indicate that the TM mutation is an effective means to improve the growth response of the antibody/receptor chimera.

Local structural effects in Sr 3NiRhO 6 across magnetic transitions

DOE PAGES

Singh, Navneet; Khalid, S.; Bindu, R.

2016-04-06

Here, we investigate the temperature dependence of the structural parameters of quasi-one-dimensional Sr 3NiRhO 6 across the region of magnetic phase transitions using Ni K-edge and Sr K-edge x-ray absorption spectroscopy (XAS). The features in the x-ray absorption near-edge region are identified using multiple scattering calculations. The temperature-dependent extended x-ray absorption fine structure (EXAFS) studies show that the setting of the intra-chain super exchange interaction starts at ~200 K, which is well above the first transition temperature (45 K) revealed by magnetic susceptibility studies. The onset of the inter-chain super–super exchange interaction appears to be at ~125 K. Interestingly, themore » role played by direct exchange interaction between the Ni 3d and Rh 4d states in stabilising the magnetic interaction is less significant. The present results shed light on the generic features exhibited by isostructural compounds and may help in identifying the magnetic exchange pathways useful for understanding the unusual properties exhibited by such compounds.« less

Mode of de-esterification of alkaline and acidic pectin methyl esterases at different pH conditions.

PubMed

Duvetter, Thomas; Fraeye, Ilse; Sila, Daniel N; Verlent, Isabel; Smout, Chantal; Hendrickx, Marc; Van Loey, Ann

2006-10-04

Highly esterified citrus pectin was de-esterified at pH 4.5 and 8.0 by a fungal pectin methyl esterase (PME) that was shown to have an acidic isoelectric pH (pI) and an acidic pH optimum and by a plant PME that was characterized by an alkaline pI and an alkaline pH optimum. Interchain and intrachain de-esterification patterns were studied by digestion of the pectin products with endo-polygalacturonase and subsequent analysis using size exclusion and anion-exchange chromatography. No effect of pH was observed on the de-esterification mode of either of the two enzymes. Acidic, fungal PME converted pectin according to a multiple-chain mechanism, with a limited degree of multiple attack at the intrachain level, both at pH 4.5 and at pH 8.0. A multiple-attack mechanism, with a high degree of multiple attack, was more appropriate to describe the action mode of alkaline, plant PME, both at pH 4.5 and at pH 8.0.

Metal ion reactive thin films using spray electrostatic LbL assembly.

PubMed

Krogman, Kevin C; Lyon, Katharine F; Hammond, Paula T

2008-11-20

By using the spray-layer-by-layer (Spray-LbL) technique, the number of metal counterions trapped within LbL coatings is significantly increased by kinetically freezing the film short of equilibrium, potentially limiting interchain penetration and forcing chains to remain extrinsically compensated to a much greater degree than observed in the traditional dipped LbL technique. The basis for the enhanced entrapment of metal ions such as Cu2+, Fe2+, and Ag+ is addressed, including the equilibrium driving force for extrinsic compensation by soft versus hard metal ions and the impact of Spray-LbL on the kinetics of polymer-ion complexation. These polymer-bound metal-ion coatings are also demonstrated to be effective treatments for air filtration, functionalizing existing filters with the ability to strongly bind toxic industrial compounds such as ammonia or cyanide gases, as well as chemical warfare agent simulants such as chloroethyl ethyl sulfide. On the basis of results reported here, future work could extend this method to include other toxic soft-base ligands such as carbon monoxide, benzene, or organophosphate nerve agents.

Morphology dependent amplified spontaneous emission in π-conjugated polymer

NASA Astrophysics Data System (ADS)

Wang, Yuchen; Yang, Xiao; Wang, Ruizhi; Li, Li; Li, Heng

2015-08-01

The amplified spontaneous emission (ASE) spectra of a π-conjugated polymer Poly [2-methoxy-5-(2‧-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) are studied in as-cast film, annealed film, 1 mg/ml solution and 2.5 mg/ml solution, respectively, using a 10 ns pulsed laser as an excitation source. We found that for annealed film (420 K), the ASE is hardly achieved compared to the as-cast film, which is consistent with the formation of the aggregation; whereas the film's temperature had much less effect on its ASE threshold. In solution, the ASE spectra show both 0-0 peak and 0-1 peak in 1 mg/ml solution, but only 0-1 peak in 2.5 mg/ml one. When the temperature of solution increases slightly from 300 K to 330 K, the ASE threshold increases dramatically in 1 mg/ml solution but slightly in 2.5 mg/ml one. Our results show the important role the morphology played in the ASE spectra in both film and solution. Therefore, controlling the interchain interaction in PCPs may be the key factor for performance of the organic lasers.

Conjugated foldamers with unusually high space-charge-limited current hole mobilities.

PubMed

Li, Yong; Dutta, Tanmoy; Gerasimchuk, Nikolay; Wu, Shijie; Shetye, Kuldeep; Jin, Lu; Wang, Ruixin; Zhu, Da-Ming; Peng, Zhonghua

2015-05-13

Charge carrier mobility and its optimization play a critical role in the development of cutting-edge organic electronic and optoelectronic devices. Even though space-charge-limited current (SCLC) hole mobilities as high as 1.4 cm(2) V(-1) s(-1) have been reported for microscopically sized highly ordered liquid-crystalline conjugated small molecules, the SCLC hole mobility of device-sized thin films of conjugated polymers is still much lower, ranging from 10(-6) to 10(-3) cm(2) V(-1) s(-1). Herein, we report the synthesis, characterizations, and thin-film SCLC mobility of three discotic conjugated polymers, INDT-TT, INDT-BT, and INDT-NDT. Optical studies indicate that polymer INDT-NDT adopts a folded conformation in solutions of good or poor solvents, whereas polymer INDT-TT stays as random monomeric chains in good solvents and interchain aggregates in poor solvents. INDT-BT polymer chains, however, stay as foldamers in dilute solutions of good solvents but interchain aggregates in concentrated solutions or poor solvents. Circular dichroism spectroscopy provides clear evidence for the helical folding of INDT-NDT in solutions. Thin films spin-coated from 1,2-dichlorobenzene solutions of the polymers show SCLC hole mobility of 2.20 × 10(-6), 8.79 × 10(-5), and 2.77 × 10(-2) cm(2) V(-1) s(-1) for INDT-TT, INDT-BT, and INDT-NDT, respectively. HRTEM and powder XRD measurements show that INDT-NDT pristine thin films contain nanocrystalline domains, whereas the INDT-TT and INDT-BT films are amorphous. Thin films of INDT-NDT:PC71BM blends show increased crystallinity and further improved SCLC hole mobility up to 1.29 × 10(-1) cm(2) V(-1) s(-1), one of the highest SCLC mobility values ever recorded on solution-processed organic semiconducting thin films. The persistent folding conformation of INDT-NDT is believed to be responsible for the high crystallinity of its thin films and its high SCLC mobilities.

Glutathione and thioredoxin systems contribute to recombinant monoclonal antibody interchain disulfide bond reduction during bioprocessing.

PubMed

Handlogten, Michael W; Zhu, Min; Ahuja, Sanjeev

2017-07-01

Antibody interchain disulfide bond reduction during biopharmaceutical manufacturing has received increased attention since it was first reported in 2010. Antibody reduction leads to loss of product and reduced product stability. It is therefore critical to understand the underlying mechanisms of reduction. To date, the thioredoxin system has been reported as the sole contributor to antibody reduction during bioprocessing. In this work, we show that the glutathione system, in addition to the thioredoxin system, is involved in reducing antibody molecules and the contributions of the two systems can vary depending upon the cell culture process. The roles of the glutathione and thioredoxin systems were evaluated for three molecules with different IgG subclass where reduction was observed during manufacturing: mAb A, mAb B, and mAb C representing an IgG 1 , IgG 2 , and IgG 4, respectively. The expression of enzymes for both the thioredoxin and glutathione systems were confirmed in all three cell lines. Inhibitors were evaluated using purified mammalian reductases to evaluate their specificity. The optimized experimental conditions enabled both the determination of reductase activity contributed from as well as the amount of antibody reduced by each enzymatic system. Our results demonstrate that the underlying enzymatic mechanisms are different depending upon the cell culture process; one of the two systems may be the dominant mechanism, or both enzymatic systems may be involved. Specifically, the glutathione system was found to be the major contributor to mAb A reduction while the thioredoxin system was the major contributor to mAb C reduction. Intriguingly, mAb B experienced significant reduction from both enzymatic systems. In summary, we have demonstrated that in addition to the thioredoxin pathway, the glutathione system is a second major pathway contributing to antibody reduction and this knowledge can be leveraged to develop more specific antibody reduction mitigation strategies targeted at the dominant reduction mechanism. Biotechnol. Bioeng. 2017;114: 1469-1477. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Rate Kinetics and Molecular Dynamics of the Structural Transitions in Amyloidogenic Proteins

NASA Astrophysics Data System (ADS)

Steckmann, Timothy M.

Amyloid fibril aggregation is associated with several horrific diseases such as Alzheimer's, Creutzfeld-Jacob, diabetes, Parkinson's and others. The process of amyloid aggregation involves forming myriad different metastable intermediate aggregates. Amyloid fibrils are composed of proteins that originate in an innocuous alpha-helix or random-coil structure. The alpha-helices convert their structure to beta-strands that aggregate into beta-sheets, and then into protofibrils, and ultimately into fully formed amyloid fibrils. On the basis of experimental data, I have developed a mathematical model for the kinetics of the reaction pathways and determined rate parameters for peptide secondary structural conversion and aggregation during the entire fibrillogenesis process from random coil to fibrils, including the molecular species that accelerate the conversions. The specific steps of the model and the rate constants that are determined by fitting to experimental data provide insight on the molecular species involved in the fibril formation process. To better understand the molecular basis of the protein structural transitions and aggregation, I report on molecular dynamics (MD) computational studies on the formation of amyloid protofibrillar structures in the small model protein ccbeta, which undergoes many of the structural transitions of the larger, naturally occurring amyloid forming proteins. Two different structural transition processes involving hydrogen bonds are observed for aggregation into fibrils: the breaking of intrachain hydrogen bonds to allow beta-hairpin proteins to straighten, and the subsequent formation of interchain hydrogen bonds during aggregation into amyloid fibrils. For my MD simulations, I found that the temperature dependence of these two different structural transition processes results in the existence of a temperature window that the ccbeta protein experiences during the process of forming protofibrillar structures. Both the mathematical modeling of the kinetics and the MD simulations show that molecular structural heterogeneity is a major factor in the process. The MD simulations also show that intrachain and interchain hydrogen bonds breaking and forming is strongly correlated to the process of amyloid formation.

Correlation between microstructure and charge transport in poly(2,5-dimethoxy- p -phenylenevinylene) thin films

NASA Astrophysics Data System (ADS)

Sims, M.; Tuladhar, S. M.; Nelson, J.; Maher, R. C.; Campoy-Quiles, M.; Choulis, S. A.; Mairy, M.; Bradley, D. D. C.; Etchegoin, P. G.; Tregidgo, C.; Suhling, K.; Richards, D. R.; Massiot, P.; Nielsen, C. B.; Steinke, J. H. G.

2007-11-01

We report a study of thin films of poly(2,5-dimethoxy- p -phenylenevinylene) (PDMeOPV) prepared by a precursor route. Conversion at two different temperatures, namely, 120 and 185°C , produces partially and fully converted films. We study the structural, optical, and charge transport characteristics of these samples in order to relate transport properties to microstructure. Micro-Raman mapping and photoluminescence (PL) imaging reveal the existence of coarse, depth-averaged domains of around 50μm in lateral extent, with more pronounced contrast for conversion at the higher temperature. The contrast in both micro-Raman and PL maps can be attributed to fluctuations in film density. Spectroscopic ellipsometry studies of the films indicate that the average film density is approximately 15% higher for conversion at the higher temperature. Time-of-flight photocurrent transients, recorded here in PDMeOPV films, are typically dispersive but yield hole mobilities in excess of 10-4cm2/Vs at modest applied fields (˜1.2×105V/cm) in the fully converted films. To our knowledge, these are amongst the highest reported mobility values for a poly( p -phenylenevinylene) derivative. Fully converted films, while yielding higher hole mobilities, exhibit a stronger dependence on electric field than partially converted ones. The higher mobility can be attributed to the almost complete conversion of the flexible saturated subunits within precursor chains to conjugated vinylene moieties at elevated temperature. This results in a correspondingly higher packing density, an improvement in intrachain transport, and a reduction in the smallest interchain hopping distance. We suggest that the stronger electric field dependence is due to the increasing influence of intermolecular electrostatic interactions with decreasing interchain separation. We propose that a greater proportion of chains in the fully converted films packs in a three-dimensional, interdigitated arrangement similar to that described previously for crystalline samples of PDMeOPV [J. H. F. Martens , Synth. Met. 55, 449 (1993)].

Water as an agent for the morphology modification of metal oxalate materials on the nanoscale: from sheets to rods

PubMed Central

Kim, Minog; Kim, YooJin; Kwon, WonJong; Yoon, Sungho

2016-01-01

A number of approaches have been used to control the shape of metal oxalates, which often used as precursors for metal oxide nanomaterials. However, attempts to use water as a regulator have not been reported. Here in we report systematic studies on related topics: nanosheets, composed of 1-dimensional [M(C2O4)(EG)] (M = Zn or Co) polymeric structure, could be transformed into nanorods by using water as a shape-shifting agent because water can readily substitute EG ligand, leading alternation of inter-chain hydrogen bonding interactions. In addition, heat-treatment of these nanomaterials with diverse morphologies resulted in porous metal oxides with high degrees of shape retention. PMID:26763973

Novel half-magnetization plateau and nematiclike transition in the S =1 skew chain Ni2V2O7

NASA Astrophysics Data System (ADS)

Ouyang, Z. W.; Sun, Y. C.; Wang, J. F.; Yue, X. Y.; Chen, R.; Wang, Z. X.; He, Z. Z.; Xia, Z. C.; Liu, Y.; Rao, G. H.

2018-04-01

A quantized magnetization plateau is usually not expected when a classic spin-flop transition occurs in a low-dimensional antiferromagnet. Here, we report an experimental observation of a spin-flop transition followed by a wide half-magnetization plateau in the S =1 skew-chain system Ni2V2O7 . This plateau, which is stabilized in fields of 8-30 T, is realized through an exotic nematiclike phase transition for magnetic fields applied along all three crystallographic axes, resulting in rich anisotropic phase diagrams. We discuss a possible mechanism whereby the magnetic frustration and interchain interactions may cause this half-magnetization plateau, which is in agreement with our exact diagonalization result.

Anisotropic dependence of the magnetic transition on uniaxial pressure in the Kondo semiconductors Ce T2A l10 (T =Ru and Os)

NASA Astrophysics Data System (ADS)

Hayashi, K.; Umeo, K.; Takeuchi, T.; Kawabata, J.; Muro, Y.; Takabatake, T.

2017-12-01

We have measured the strain, magnetization, and specific heat of the antiferromagnetic (AFM) Kondo semiconductors Ce T2A l10 (T =Ru and Os) under uniaxial pressures applied along the orthorhombic axes. We found a linear dependence of TN on the b -axis parameter for both compounds under uniaxial pressure P ∥b and hydrostatic pressure. This relation indicates that the distance between the Ce-T layers along the b axis is the key structural parameter determining TN. Furthermore, the pressure dependence of the spin-flop transition field indicates that Ce-Ce interchain interactions stabilize the AFM state with the ordered moments pointing to the c axis.

Combining microscopic and macroscopic probes to untangle the single-ion anisotropy and exchange energies in an S = 1 quantum antiferromagnet [Combining micro- and macroscopic probes to untangle single-ion and spatial exchange anisotropies in a S = 1 quantum antiferromagnet

DOE PAGES

Brambleby, Jamie; Manson, Jamie L.; Goddard, Paul A.; ...

2017-04-20

The magnetic ground state of the quasi-one-dimensional spin-1 antiferromagnetic chain is sensitive to the relative sizes of the single-ion anisotropy (D) and the intrachain (J) and interchain (J') exchange interactions. The ratios D/J and J' /J dictate the material's placement in one of three competing phases: a Haldane gapped phase, a quantum paramagnet, and an XY-ordered state, with a quantum critical point at their junction. We have identified [Ni(HF 2)(pyz) 2] SbF 6, where pyz = pyrazine, as a rare candidate in which this behavior can be explored in detail. Combining neutron scattering (elastic and inelastic) in applied magnetic fieldsmore » of up to 10 tesla and magnetization measurements in fields of up to 60 tesla with numerical modeling of experimental observables, we are able to obtain accurate values of all of the parameters of the Hamiltonian [D = 13.3(1) K, J = 10.4(3) K, and J' = 1.4(2) K], despite the polycrystalline nature of the sample. Density-functional theory calculations result in similar couplings (J = 9.2 K, J' = 1.8 K) and predict that the majority of the total spin population resides on the Ni(II) ion, while the remaining spin density is delocalized over both ligand types. Finally, the general procedures outlined in this paper permit phase boundaries and quantum-critical points to be explored in anisotropic systems for which single crystals are as yet unavailable.« less

Discovery and characterization of antibody variants using mass spectrometry-based comparative analysis for biosimilar candidates of monoclonal antibody drugs.

PubMed

Li, Wenhua; Yang, Bin; Zhou, Dongmei; Xu, Jun; Ke, Zhi; Suen, Wen-Chen

2016-07-01

Liquid chromatography mass spectrometry (LC-MS) is the most commonly used technique for the characterization of antibody variants. MAb-X and mAb-Y are two approved IgG1 subtype monoclonal antibody drugs recombinantly produced in Chinese hamster ovary (CHO) cells. We report here that two unexpected and rare antibody variants have been discovered during cell culture process development of biosimilars for these two approved drugs through intact mass analysis. We then used comprehensive mass spectrometry-based comparative analysis including reduced light, heavy chains, and domain-specific mass as well as peptide mapping analysis to fully characterize the observed antibody variants. The "middle-up" mass comparative analysis demonstrated that the antibody variant from mAb-X biosimilar candidate was caused by mass variation of antibody crystalline fragment (Fc), whereas a different variant with mass variation in antibody antigen-binding fragment (Fab) from mAb-Y biosimilar candidate was identified. Endoproteinase Lys-C digested peptide mapping and tandem mass spectrometry analysis further revealed that a leucine to glutamine change in N-terminal 402 site of heavy chain was responsible for the generation of mAb-X antibody variant. Lys-C and trypsin coupled non-reduced and reduced peptide mapping comparative analysis showed that the formation of the light-heavy interchain trisulfide bond resulted in the mAb-Y antibody variant. These two cases confirmed that mass spectrometry-based comparative analysis plays a critical role for the characterization of monoclonal antibody variants, and biosimilar developers should start with a comprehensive structural assessment and comparative analysis to decrease the risk of the process development for biosimilars. Copyright © 2016 Elsevier B.V. All rights reserved.

Bismuth chalcohalides and oxyhalides as optoelectronic materials

DOE PAGES

Du, Mao -Hua; Shi, Hongliang; Ming, Wenmei

2016-03-29

Several Tl and Pb based halides and chalcohalides have recently been discovered as promising optoelectronic materials [i.e., photovoltaic (PV) and gamma-ray detection materials]. Efficient carrier transport in these materials is attributed partly to the special chemistry of ns 2 ions (e.g., Tl +, Pb 2+, and Bi 3+). However, the toxicity of Tl and Pb is challenging to the development and the wide use of Tl and Pb based materials. In this paper, we investigate materials that contain Bi 3+, which is also an ns 2 ion. By combining Bi halides with Bi chalcogenides or oxides, the resulting ternary compoundsmore » exhibit a wide range of band gaps, offering opportunities in various optoelectronic applications. Density functional calculations of electronic structure, dielectric properties, optical properties, and defect properties are performed on selected Bi 3+ based chalcohalides and oxyhalides, i.e., BiSeBr, BiSI, BiSeI, and BiOBr. We propose different applications for these Bi compounds based on calculated properties, i.e., n-BiSeBr, p-BiSI, and p-BiSeI as PV materials, BiSeBr and BiSI as room-temperature radiation detection materials, and BiOBr as a p-type transparent conducting material. BiSeBr, BiSI, and BiSeBr have chain structures while BiOBr has a layered structure. However, in BiSI, BiSeI, and BiOBr, significant valence-band dispersion is found in the directions perpendicular to the atomic chain or layer because the valence-band edge states are dominated by the halogen states that have strong interchain or interlayer coupling. We find significantly enhanced Born effective charges and anomalously large static dielectric constants of the Bi compounds, which should reduce carrier scattering and trapping and promote efficient carrier transport in these materials. The strong screening and the small anion coordination numbers in Bi chalcohalides should lead to weak potentials for electron localization at anion vacancies. As a result, defect calculations indeed show that the anion vacancies (Se and Br vacancies) in BiSeBr are shallow, which is beneficial to efficient electron transport.« less

A fused-ring acceptor unit in d-a copolymers benefits photovoltaic performance.

PubMed

Zuo, Chuantian; Cao, Jiamin; Ding, Liming

2014-08-01

Pentacyclic lactam acceptor unit TPTI invented by our group is proved to be a good building block for efficient D-A copolymers used in organic solar cells. Here, two D-A copolymers PBTTPTI and PTTTPTI are developed by copolymerizing TPTI with 2,2'-bithiophene (BT) or thieno[3,2-b]thiophene (TT). PBTTPTI and PTTTPTI exhibit good solubility and strong interchain π-π interaction even in dilute solution. They possess deep HOMO levels (ca. -5.3 eV), partial crystallinity, and good hole mobilities. Blending with PC71 BM, PBTTPTI and PTTTPTI give decent power conversion efficiencies (PCE) up to 6.83% and 5.86%, with outstanding fill factors (FF) of 74.3% and 71.3%, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Long-range exciton transport in conjugated polymer nanofibers prepared by seeded growth

NASA Astrophysics Data System (ADS)

Jin, Xu-Hui; Price, Michael B.; Finnegan, John R.; Boott, Charlotte E.; Richter, Johannes M.; Rao, Akshay; Menke, S. Matthew; Friend, Richard H.; Whittell, George R.; Manners, Ian

2018-05-01

Easily processed materials with the ability to transport excitons over length scales of more than 100 nanometers are highly desirable for a range of light-harvesting and optoelectronic devices. We describe the preparation of organic semiconducting nanofibers comprising a crystalline poly(di-n-hexylfluorene) core and a solvated, segmented corona consisting of polyethylene glycol in the center and polythiophene at the ends. These nanofibers exhibit exciton transfer from the core to the lower-energy polythiophene coronas in the end blocks, which occurs in the direction of the interchain π-π stacking with very long diffusion lengths (>200 nanometers) and a large diffusion coefficient (0.5 square centimeters per second). This is made possible by the uniform exciton energetic landscape created by the well-ordered, crystalline nanofiber core.

Disulphide bonds in casein micelle from milk.

PubMed

Bouguyon, Edwige; Beauvallet, Christian; Huet, Jean-Claude; Chanat, Eric

2006-05-05

Mammary epithelial cells synthesised and secreted caseins, the major milk proteins in most mammals, as large aggregates called micelles into the alveolar lumen they surround. We investigated the implication of the highly conserved cysteine(s) of kappa-casein in disulphide bond formation in casein micelles from several species. Dimers were found in all milks studied, confirming previous observation in ruminants. More importantly, the study of interchain disulphide bridges in mouse and rat casein micelles revealed that any casein possessing a cysteine is engaged in disulphide bond interchange; these species express four or five cysteine-containing caseins, respectively. We found that the main rodent caseins form both homo- and heterodimers. Additionally, disulphide bond formation among milk proteins was specific since the interaction of the caseins with cysteine-containing whey proteins was not observed in native casein micelles.

Effect of silica nanoparticle filler on microscopic polymer α-relaxation dynamics

NASA Astrophysics Data System (ADS)

Saito, Makina; Mashita, Ryo; Kishimoto, Hiroyuki; Masuda, Ryo; Yoda, Yoshitaka; Seto, Makoto

2017-11-01

Tyre rubber has been continuously developed to improve its performance, but the microscopic mechanisms behind these improvements, e.g. by adding nanoparticles to the rubber, are still not fully understood. We study the microscopic polymer dynamics of a rubber nanocomposite system consisting of polymer polybutadiene with 20 volume% of silica nanoparticles with diameters of 100 nm via quasi-elastic scattering experiments using gamma-ray time-domain interferometry. The result shows that the presence of silica nanoparticles caused the inter-chain α-relaxation dynamics to slow down in a shallowly supercooled state suggesting that the presence of the nanoparticles that came in contact with the polymer controlled the timescale of the polymer's α-relaxation dynamics. Conversely, the presence of nanoparticles less affects the dynamics in a lower temperature region near T g. It is consistent with the result of the differential scanning calorimetry study showing negligible T g difference among the pure polymer and the nanocomposite system. It also shows that the quasi-elastic scattering experiment can be used to reveal the polymer dynamics in nanocomposites and is appropriate for characterising their microscopic dynamics for the purpose of improving tyre performance.

Effect of a small amount of sodium carbonate on konjac glucomannan-induced changes in wheat starch gel.

PubMed

Zhou, Yun; Zhao, Dan; Winkworth-Smith, Charles G; Foster, Tim J; Nirasawa, Satoru; Tatsumi, Eizo; Cheng, Yongqiang

2015-02-13

Wheat starch gels were produced with konjac glucomannan (KGM) and low concentrations of Na2CO3 (0.1-0.2 wt% of starch) using a rapid viscosity analyzer (RVA). The gelling properties of wheat starch in varying ratios of KGM and Na2CO3 were characterized by differential scanning calorimetry (DSC), rheometry and confocal laser scanning microscopy (CLSM). A small amount of Na2CO3 resulted in gels with increased elasticity whereas structural ordering during retrogradation was insignificantly affected. Comparison of CLSM images of composite gels revealed that Na2CO3 at 0.2 wt% of starch allowed the formation of fiber-like extensions around scattered swollen granules by KGM and amylose interaction, making swollen granules disperse within the micro phase, which was not typical in CLSM images of gels in the absence of Na2CO3. Dynamic storage modulus and dynamic power law exponent were substantially higher than those observed for the same concentration of KGM in the presence of Na2CO3, supporting the hypothesis that Na2CO3 could promote strong interchain associations between KGM and starch components. Copyright © 2014 Elsevier Ltd. All rights reserved.

Different redox sensitivity of endoplasmic reticulum associated degradation clients suggests a novel role for disulphide bonds in secretory proteins.

PubMed

Medraño-Fernandez, Iria; Fagioli, Claudio; Mezghrani, Alexandre; Otsu, Mieko; Sitia, Roberto

2014-04-01

To maintain proteostasis in the endoplasmic reticulum (ER), terminally misfolded secretory proteins must be recognized, partially unfolded, and dislocated to the cytosol for proteasomal destruction, in a complex process called ER-associated degradation (ERAD). Dislocation implies reduction of inter-chain disulphide bonds. When in its reduced form, protein disulphide isomerase (PDI) can act not only as a reductase but also as an unfoldase, preparing substrates for dislocation. PDI oxidation by Ero1 favours substrate release and transport across the ER membrane. Here we addressed the redox dependency of ERAD and found that DTT stimulates the dislocation of proteins with DTT-resistant disulphide bonds (i.e., orphan Ig-μ chains) but stabilizes a ribophorin mutant (Ri332) devoid of them. DTT promotes the association of Ri332, but not of Ig-µ, with PDI. This discrepancy may suggest that disulphide bonds in cargo proteins can be utilized to oxidize PDI, hence facilitating substrate detachment and degradation also in the absence of Ero1. Accordingly, Ero1 silencing retards Ri332 degradation, but has little if any effect on Ig-µ. Thus, some disulphides can increase the stability and simultaneously favour quality control of secretory proteins.

Effect of chain structure on hydrogen bonding in vinyl acetate - vinyl alcohol copolymers

NASA Astrophysics Data System (ADS)

Merekalova, Nadezhda D.; Bondarenko, Galina N.; Denisova, Yuliya I.; Krentsel, Liya B.; Litmanovich, Arkadiy D.; Kudryavtsev, Yaroslav V.

2017-04-01

FTIR spectroscopy and semi-empirical AM1 method are used to study hydrogen bonding in multiblock and random equimolar copolymers of vinyl acetate and vinyl alcohol. An energetically beneficial zip-holder complex, built on multiple inter- and intrachain hydroxyl-hydroxyl bonds and an intrachain hydroxyl-acetyloxy bond, can be formed between two vinyl alcohol sequences. As a result, multiblock copolymers reveal stronger degree of association that affects crystallinity, as well as various rheological and relaxation properties discussed in the literature. Macromolecular complexes in random copolymers are weak and tend to be destroyed in the presence of residual DMF solvent and adsorbed water. Nevertheless, a rather stable interchain quaternary complex can be formed that includes vinyl alcohol and vinyl acetate units and DMF and water molecules. For a single chain it is shown that an H-bond between neighboring vinyl alcohol and vinyl acetate monomer units mostly engages a carbonyl oxygen atom of the vinyl acetate, if the vinyl alcohol belongs to a short (<5 units) sequence, and an ether oxygen atom in the other case. On the whole, the quantum chemistry calculations shed much light on the origin of distinctions in the copolymer FTIR spectra, which may seem subtle when considered standalone.

Influence of particle arrangement on the permittivity of an elastomeric composite

NASA Astrophysics Data System (ADS)

Tsai, Peiying J.; Nayak, Suchitra; Ghosh, Suvojit; Puri, Ishwar K.

2017-01-01

Elastomers are used as dielectric layers contained between the parallel conductive plates of capacitors. The introduction of filler particles into an elastomer changes its permittivity ɛ. When particle organization in a composite is intentionally varied, this alters its capacitance. Using numerical simulations, we examine how conductive particle chains introduced into polydimethylsiloxane (PDMS) alter ɛ. The effects of filler volume fraction ψ, interparticle d and interchain spacing a, zigzag angle θ between adjacent particles and overall chain orientation, particle size r, and clearance h between particles and the conductive plates are characterized. When filler particles are organized into chainlike structures rather than being just randomly distributed in the elastomer matrix, ɛ increases by as much as 85%. When particles are organized into chainlike forms, ɛ increases with increasing ψ and a, but decreases with increasing d and θ. A composite containing smaller particles has a higher ɛ when ψ <9 % while larger particles provide greater enhancement when ψ is larger than that value. To enhance ɛ, adjacent particles must be interconnected and the overall chain direction should be oriented perpendicular to the conductive plates. These results are useful for additive manufacturing on electrical applications of elastomeric composites.

Nuclearity controlled cyanide-bridged bimetallic CrIII-MnII compounds: synthesis, crystal structures, magnetic properties and theoretical calculations.

PubMed

Toma, Luminita; Lescouëzec, Rodrigue; Vaissermann, Jacqueline; Delgado, Fernando S; Ruiz-Pérez, Catalina; Carrasco, Rosa; Cano, Juan; Lloret, Francesc; Julve, Miguel

2004-11-19

The preparation, X-ray crystallography and magnetic investigation of the compounds PPh4[Cr(bipy)(CN)4].2 CH3CN.H2O (1) (mononuclear), [[Cr(bipy)(CN)4]2Mn-(H2O)4].4H2O (2) (trinuclear), [[Cr(bipy)(CN)4]2Mn(H2O)2] (3) (chain) and [[Cr(bipy)(CN)4]2Mn(H2O)].H2O.CH3CN (4) (double chain) [bipy=2,2'-bipyridine; PPh4 (+)=tetraphenylphosphonium] are described herein. The [Cr(bipy)(CN)4]- unit act either as a monodentate (2) or bis-monodentate (3) ligand toward the manganese atom through one (2) or two (3) of its four cyanide groups. The manganese atom is six-coordinate with two (2) or four (3) cyanide nitrogens and four (2) or two (3) water molecules building a distorted octahedral environment. In 4, two chains of 3 are pillared through interchain Mn-N-C-Cr links which replace one of the two trans-coordinated water molecules at the manganese atom to afford a double chain structure where bis- and tris-monodenate coordination modes of [Cr(bipy)(CN)4]- coexist. The magnetic properties of 1-4 were investigated in the temperature range 1.9-300 K. A Curie law behaviour for a magnetically isolated spin quartet is observed for 1. A significant antiferromagnetic interaction between CrIII and MnII through the single cyanide bridge [J=-6.2 cm(-1), the Hamiltonian being defined as H=-J(SCr1.SMn+SCr2.SMn] occurs in 2 leading to a low-lying spin doublet which is fully populated at T <5 K. A metamagnetic behaviour is observed for 3 and 4 [the values of the critical field Hc being ca. 3000 (3) and 1500 Oe (4)] which is associated to the occurrence of weak interchain antiferromagnetic interactions between ferrimagnetic Cr2III MnII chains. The analysis of the exchange pathways in 2-4 through DFT type calculations together with the magnetic bevaviour simulation using the quantum Monte Carlo methodology provided a good understanding of their magnetic properties.

Effect of Salt Concentration on the pH Responses of Strong and Weak Polyelectrolyte Brushes.

PubMed

Zhang, Jian; Kou, Ran; Liu, Guangming

2017-07-11

Strong polyelectrolyte brushes (SPB) and weak polyelectrolyte brushes (WPB) have different origins with response to pH, which makes their pH-responsive properties sensitive to salt concentration in different ways. Herein, we have employed poly[2-(methacryloyloxy)ethyl trimethylammonium chloride] (PMETAC) and poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) brushes as model systems for SPB and WPB, respectively, to investigate the effect of salt concentration on the pH responses of SPB and WPB using several surface-sensitive techniques. The pH-responsive properties of the PMETAC brushes are governed by the reorganization of the interchain hydrogen bonds between the grafted chains, whereas the pH response of the PDMAEMA brushes is controlled by the charge of the grafted chains. The response of the properties of the PMETAC brushes including hydration, conformation, and surface wettability becomes weaker with increasing salt concentration induced by the competitive adsorption of counterions to the brushes between OH - and Cl - . The weakening of the pH response of the PMETAC brushes is more remarkable at the relatively high pH values. The pH response of the PDMAEMA brushes also exhibits a salt-concentration dependence. As the salt concentration increases, the weakening of the pH response of the PDMAEMA brushes is attributed to the decrease in osmotic pressure within the brushes at relatively low pH values.

Some photophysical properties of new oligomer obtained from anodic oxidation of 4,4‧-dimethoxychalcone

NASA Astrophysics Data System (ADS)

Ghomrasni, S.; Aribi, I.; Chemek, M.; Said, A. Haj; Alimi, K.

2018-04-01

Some photopysical properties of a new oligomer obtained from the anodic oxidation of the 4,4‧-dimethoxy-chalcone were investigated using different and complementary techniques. Firstly, TGA analysis and X-Ray diffraction experiments showed that the oligomer is thermally stable up to 500 K and partially organized at the solid state, respectively. Secondly, the optical properties of the oligomer were studied in solution and in the solid state. The optical band gap was estimated to be 3.17 eV in solution state and 2.70 eV in film state. What's more, the fluorescence decay is determined showing a considerably faster in the film state (0.183 ns) than in solution state (1.606 ns), due to the rapid non-radiative decay at inter-chain trap sites.

Lattice model simulation of interchain protein interactions and the folding dynamics and dimerization of the GCN4 Leucine zipper

NASA Astrophysics Data System (ADS)

Liu, Yanxin; Chapagain, Prem P.; Parra, Jose L.; Gerstman, Bernard S.

2008-01-01

The highest level in the hierarchy of protein structure and folding is the formation of protein complexes through protein-protein interactions. We have made modifications to a well established computer lattice model to expand its applicability to two-protein dimerization and aggregation. Based on Brownian dynamics, we implement translation and rotation moves of two peptide chains relative to each other, in addition to the intrachain motions already present in the model. We use this two-chain model to study the folding dynamics of the yeast transcription factor GCN4 leucine zipper. The calculated heat capacity curves agree well with experimental measurements. Free energy landscapes and median first passage times for the folding process are calculated and elucidate experimentally measured characteristics such as the multistate nature of the dimerization process.

Surface crystallographic structures of cellulose nanofiber films and overlayers of pentacene

NASA Astrophysics Data System (ADS)

Nakayama, Yasuo; Mori, Toshiaki; Tsuruta, Ryohei; Yamanaka, Soichiro; Yoshida, Koki; Imai, Kento; Koganezawa, Tomoyuki; Hosokai, Takuya

2018-03-01

Cellulose nanofibers or nanocellulose is a promising recently developed biomass and biodegradable material used for various applications. In order to utilize this material as a substrate in organic electronic devices, thorough understanding of the crystallographic structures of the surfaces of the nanocellulose composites and of their interfaces with organic semiconductor molecules is essential. In this work, surface crystallographic structures of nanocellulose films (NCFs) and overlayers of pentacene were investigated by two-dimensional grazing-incidence X-ray diffraction. The NCFs are found to crystallize on solid surfaces with the crystal lattice preserving the same structure of the known bulk phase, whereas distortion of interchain packing toward the surface normal direction is suggested. The pentacene overlayers on the NCFs are found to form the thin-film phase with an in-plane mean crystallite size of over 10 nm.

Skin Membrane Electrical Impedance Properties under the Influence of a Varying Water Gradient

PubMed Central

Björklund, Sebastian; Ruzgas, Tautgirdas; Nowacka, Agnieszka; Dahi, Ihab; Topgaard, Daniel; Sparr, Emma; Engblom, Johan

2013-01-01

The stratum corneum (SC) is an effective permeability barrier. One strategy to increase drug delivery across skin is to increase the hydration. A detailed description of how hydration affects skin permeability requires characterization of both macroscopic and molecular properties and how they respond to hydration. We explore this issue by performing impedance experiments on excised skin membranes in the frequency range 1 Hz to 0.2 MHz under the influence of a varying gradient in water activity (aw). Hydration/dehydration induces reversible changes of membrane resistance and effective capacitance. On average, the membrane resistance is 14 times lower and the effective capacitance is 1.5 times higher when the outermost SC membrane is exposed to hydrating conditions (aw = 0.992), as compared to the case of more dehydrating conditions (aw = 0.826). Molecular insight into the hydration effects on the SC components is provided by natural-abundance 13C polarization transfer solid-state NMR and x-ray diffraction under similar hydration conditions. Hydration has a significant effect on the dynamics of the keratin filament terminals and increases the interchain spacing of the filaments. The SC lipids are organized into lamellar structures with ∼ 12.6 nm spacing and hexagonal hydrocarbon chain packing with mainly all-trans configuration of the acyl chains, irrespective of hydration state. Subtle changes in the dynamics of the lipids due to mobilization and incorporation of cholesterol and long-chain lipid species into the fluid lipid fraction is suggested to occur upon hydration, which can explain the changes of the impedance response. The results presented here provide information that is useful in explaining the effect of hydration on skin permeability. PMID:23790372

The RING 2.0 web server for high quality residue interaction networks.

PubMed

Piovesan, Damiano; Minervini, Giovanni; Tosatto, Silvio C E

2016-07-08

Residue interaction networks (RINs) are an alternative way of representing protein structures where nodes are residues and arcs physico-chemical interactions. RINs have been extensively and successfully used for analysing mutation effects, protein folding, domain-domain communication and catalytic activity. Here we present RING 2.0, a new version of the RING software for the identification of covalent and non-covalent bonds in protein structures, including π-π stacking and π-cation interactions. RING 2.0 is extremely fast and generates both intra and inter-chain interactions including solvent and ligand atoms. The generated networks are very accurate and reliable thanks to a complex empirical re-parameterization of distance thresholds performed on the entire Protein Data Bank. By default, RING output is generated with optimal parameters but the web server provides an exhaustive interface to customize the calculation. The network can be visualized directly in the browser or in Cytoscape. Alternatively, the RING-Viz script for Pymol allows visualizing the interactions at atomic level in the structure. The web server and RING-Viz, together with an extensive help and tutorial, are available from URL: http://protein.bio.unipd.it/ring. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

Structural plasticity of 4-α-helical bundles exemplified by the puzzle-like molecular assembly of the Rop protein

PubMed Central

Amprazi, Maria; Kotsifaki, Dina; Providaki, Mary; Kapetaniou, Evangelia G.; Fellas, Georgios; Kyriazidis, Ioannis; Pérez, Javier; Kokkinidis, Michael

2014-01-01

The dimeric Repressor of Primer (Rop) protein, a widely used model system for the study of coiled-coil 4-α-helical bundles, is characterized by a remarkable structural plasticity. Loop region mutations lead to a wide range of topologies, folding states, and altered physicochemical properties. A protein-folding study of Rop and several loop variants has identified specific residues and sequences that are linked to the observed structural plasticity. Apart from the native state, native-like and molten-globule states have been identified; these states are sensitive to reducing agents due to the formation of nonnative disulfide bridges. Pro residues in the loop are critical for the establishment of new topologies and molten globule states; their effects, however, can be in part compensated by Gly residues. The extreme plasticity in the assembly of 4-α-helical bundles reflects the capacity of the Rop sequence to combine a specific set of hydrophobic residues into strikingly different hydrophobic cores. These cores include highly hydrated ones that are consistent with the formation of interchain, nonnative disulfide bridges and the establishment of molten globules. Potential applications of this structural plasticity are among others in the engineering of bio-inspired materials. PMID:25024213

Challenges in Laser Sintering of Melt-Processable Thermoset Imide Resin

NASA Technical Reports Server (NTRS)

Chuang, Kathy C.; Gornet, Timothy; Koerner, Hilmar

2016-01-01

Polymer Laser Sintering (LS) is an additive manufacturing technique that builds 3D models layer by layer using a laser to selectively melt cross sections in powdered polymeric materials, following sequential slices of the CAD model. LS generally uses thermoplastic polymeric powders, such as polyamides (i.e. Nylon), and the resultant 3D objects are often weaker in their strength compared to traditionally processed materials, due to the lack of polymer inter-chain connection in the z-direction. The objective of this project is to investigate the possibility of printing a melt-processable RTM370 imide resin powder terminated with reactive phenylethynyl groups by LS, followed by a postcure in order to promote additional crosslinking to achieve higher temperature (250-300 C) capability. A preliminary study to build tensile specimens by LS and the corresponding DSC and rheology study of RTM370 during LS process is presented.

Challenges in Laser Sintering of Thermoset Imide Resin

NASA Technical Reports Server (NTRS)

Chuang, Kathy C.; Gornet, Timothy; Koerner, Hilmar

2016-01-01

Polymer Laser Sintering (LS) is an additive manufacturing technique that builds 3D models layer by layer using a laser to selectively melt cross sections in powdered polymeric materials, following sequential slices of the CAD model. LS generally uses thermoplastic polymeric powders, such as polyamides (i.e. Nylon), and the resultant 3D objects are often weaker in their strength compared to traditionally processed materials, due to the lack of polymer inter-chain connection in the z-direction. The objective of this project is to investigate the possibility of printing a melt-processable RTM370 imide resin powder terminated with reactive phenylethynyl groups by LS, followed by a postcure in order to promote additional crosslinking to achieve higher temperature (250-300 C) capability. A preliminary study to build tensile specimens by LS and the corresponding DSC and rheology study of RTM370 during LS process is presented.

Field-induced States and Excitations in the Quasicritical Spin-1 /2 Chain Linarite

NASA Astrophysics Data System (ADS)

Cemal, Eron; Enderle, Mechthild; Kremer, Reinhard K.; Fâk, Björn; Ressouche, Eric; Goff, Jon P.; Gvozdikova, Mariya V.; Zhitomirsky, Mike E.; Ziman, Tim

2018-02-01

The mineral linarite, PbCuSO4(OH )2 , is a spin-1 /2 chain with frustrating nearest-neighbor ferromagnetic and next-nearest-neighbor antiferromagnetic exchange interactions. Our inelastic neutron scattering experiments performed above the saturation field establish that the ratio between these exchanges is such that linarite is extremely close to the quantum critical point between spin-multipolar phases and the ferromagnetic state. We show that the predicted quantum multipolar phases are fragile and actually suppressed by a tiny orthorhombic exchange anisotropy and weak interchain interactions in favor of a dipolar fan phase. Including this anisotropy in classical simulations of a nearly critical model explains the field-dependent phase sequence of the phase diagram of linarite, its strong dependence of the magnetic field direction, and the measured variations of the wave vector as well as the staggered and the uniform magnetizations in an applied field.

Monomer/Dimer Transition of the Caspase-Recruitment Domain of Human Nod1

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

Srimathi,T.; Robbins, S.; Dubas, R.

2008-01-01

Nod1 is an essential cytoplasmic sensor for bacterial peptidoglycans in the innate immune system. The caspase-recruitment domain of Nod1 (Nod1{_}CARD) is indispensable for recruiting a downstream kinase, receptor-interacting protein 2 (RIP2), that activates nuclear factor-?B (NF-?B). The crystal structure of human Nod1{_}CARD at 1.9 Angstroms resolution reveals a novel homodimeric conformation. Our structural and biochemical analysis shows that the homodimerization of Nod1{_}CARD is achieved by swapping the H6 helices at the carboxy termini and stabilized by forming an interchain disulfide bond between the Cys39 residues of the two monomers in solution and in the crystal. In addition, we present experimentalmore » evidence for a pH-sensitive conformational change of Nod1{_}CARD. Our results suggest that the pH-sensitive monomer/dimer transition is a unique molecular property of Nod1{_}CARD.« less

Imaging phospholipid conformational disorder and packing in giant multilamellar liposome by confocal Raman microspectroscopy

NASA Astrophysics Data System (ADS)

Noothalapati, Hemanth; Iwasaki, Keita; Yoshimoto, Chikako; Yoshikiyo, Keisuke; Nishikawa, Tomoe; Ando, Masahiro; Hamaguchi, Hiro-o.; Yamamoto, Tatsuyuki

2017-12-01

Liposomes are closed phospholipid bilayer systems that have profound applications in fundamental cell biology, pharmaceutics and medicine. Depending on the composition (pure or mixture of phospholipids, presence of cholesterol) and preparation protocol, intra- and inter-chain molecular interactions vary leading to changes in the quality (order and packing) of liposomes. So far it is not possible to image conformational disorders and packing densities within a liposome in a straightforward manner. In this study, we utilized confocal Raman microspectroscopy to visualize structural disorders and packing efficiency within a giant multilamellar liposome model by focusing mainly on three regions in the vibrational spectrum (Csbnd C stretching, Csbnd H deformation and Csbnd H stretching). We estimated properties such as trans/gauche isomers and lateral packing probability. Interestingly, our Raman imaging studies revealed gel phase rich domains and heterogeneous lateral packing within the giant multilamellar liposome.

Synthesis, Crystal Structure, and Magnetic Properties of the Linear-Chain Cobalt Oxide Sr 5Pb 3CoO 12

NASA Astrophysics Data System (ADS)

Yamaura, K.; Huang, Q.; Takayama-Muromachi, E.

2002-02-01

The novel spin-chain cobalt oxide Sr5Pb3CoO12 [Poverline6×2m, a=10.1093(2) Å and c=3.562 51(9) Å at 295 K] is reported. A polycrystalline sample of the compound was studied by neutron diffraction (at 6 and 295 K) and magnetic susceptibility measurements (5 to 390 K). The cobalt oxide was found to be analogous to the copper oxide Sr5Pb3CuO12, which is comprised of magnetic-linear chains at an interchain distance of 10 Å. Although the cobalt oxide chains (μeff of 3.64 μB per Co) are substantially antiferromagnetic (θW=-38.8 K), neither low-dimensional magnetism nor long-range ordering has been found; a local-structure disorder in the chains might have an impact on the magnetism. This compound is highly electrically insulating.

Multi-barrier field-emission behavior in PBTTT thin films at low temperatures

PubMed Central

Kang, Evan S. H.; Kim, Eunseong

2015-01-01

We investigated the low-temperature transport mechanism for poly[2,5-bis(3-alkylthiophen-2-yl)thieno(3,2-b)thiophene] (PBTTT). The temperature-dependent transport behavior was studied by varying the drain–source electric field and gate bias. The results suggest that low-temperature charge transport is dominated by direct tunneling at low electric fields, while field emission is prevailing for high electric fields with high carrier densities. However, the obtained barrier heights are remarkably greater than expected in a conventional field emission. We propose a simplified model of field emission through quasi-one-dimensional path with multiple barriers which shows good agreement with the results more clearly. Field emission across the domain boundaries may assist in overcoming the transport barriers induced by the interchain disorder, which results in the weak temperature dependence of conductivities and nonlinear current–voltage relation at low temperatures. PMID:25670532

Collagenolytic Matrix Metalloproteinase Structure-Function Relationships: Insights From Molecular Dynamics Studies.

PubMed

Karabencheva-Christova, Tatyana G; Christov, Christo Z; Fields, Gregg B

2017-01-01

Several members of the zinc-dependent matrix metalloproteinase (MMP) family catalyze collagen degradation. Experimental data reveal a collaboration between different MMP domains in order to achieve efficient collagenolysis. Molecular dynamics (MD) simulations have been utilized to provide atomistic details of the collagenolytic process. The triple-helical structure of collagen exhibits local regions of flexibility, with modulation of interchain salt bridges and water bridges contributing to accessibility of individual chains by the enzyme. In turn, the hemopexin-like (HPX) domain of the MMP initially binds the triple helix and facilitates the presentation of individual strands to active site in the catalytic (CAT) domain. Extensive positive and negative correlated motions are observed between the CAT and HPX domains when collagen is bound. Ultimately, the MD simulation studies have complemented structural (NMR spectroscopy, X-ray crystallography) and kinetic analyses to provide a more detailed mechanistic view of MMP-catalyzed collagenolysis. © 2017 Elsevier Inc. All rights reserved.

Molecular association of 2-(n-alkylamino)-1,4-naphthoquinone derivatives: Electrochemical, DFT studies and antiproliferative activity against leukemia cell lines

NASA Astrophysics Data System (ADS)

Patil, Rishikesh; Bhand, Sujit; Konkimalla, V. Badireenath; Banerjee, Priyabrata; Ugale, Bharat; Chadar, Dattatray; Saha, Sourav Kr.; Praharaj, Prakash Priyadarshi; Nagaraja, C. M.; Chakrovarty, Debamitra; Salunke-Gawali, Sunita

2016-12-01

Molecular structures and their molecular association of 2-(n-alkylamino)-1,4-naphthoquinone, viz., LH-3; propyl, LH-4; butyl and LH-8; octyl derivatives were studied by single crystal X-ray diffraction studies. Synthesis and characterization of 2-octylamino-1,4-naphthoquinone; LH-8 was discussed. The molecule of LH-3 crystallizes in orthorhombic space group P21/c, while the LH-4 and LH-8 molecule crystallizes in triclinic space group P-1. LH-3, LH-4 and LH-8 showed intermolecular N-H⋯O and C-H⋯O interactions, LH-3 showed unique C(3)-H(3)⋯O(1) interaction. Interchain π-π stacking, slipped π-π stacking and C⋯O close contacts was respectively observed in LH-3, LH-4 and LH-8. Electrochemical studies were performed on first eight members of homologous series of 2-(n-alkylamino)-1,4-naphthoquinone (LH-1 to LH-8) by cyclic voltammetry. Naphthoquinone to naphthosemiquinone reversible redox couple was observed in all compounds ∼ E1/2 = -0.657 ± 0.05 V. HOMO-LUMO band gap was determined for the neutral form as well as the monoanionic radical form viz. naphthosemiquinone form of selected derivatives by DFT studies. It has been observed that the electron density is delocalized in the naphthoquinone ring in both neutral as well as one electron reduced form of compounds. Antiproliferative activity of LH-1 to LH-8 was evaluated against two cancer cell lines, THP1(acute monocytic leukemia) and K562(human immortalized myelogenous leukemia cell line) cells. It was observed that, in THP1 cells, compounds LH-2 and LH-3 are very active while LH-1, LH-4 and LH-6 were moderately active and LH-5, LH-7 and LH-8 were totally inactive. Contrastingly, in K562 cells all of the compounds were moderately active.

[Fe(III)(dmbpy)(CN)4]-: a new building block for designing single-chain magnets.

PubMed

Toma, Luminita Marilena; Pasán, Jorge; Ruiz-Pérez, Catalina; Lloret, Francesc; Julve, Miguel

2012-11-28

We herein present the synthesis and magneto-structural study of a new family of heterobimetallic chains of general formula {[Fe(III)(dmbpy)(CN)(4)](2)M(II)(H(2)O)(2)}(n)·pnH(2)O [dmbpy = 4,4'-dimethyl-2,2'-bipyridine; M = Mn (2), Cu (3), Ni (4) and Co (5) with p = 4 (2), 3 (3), 9 (4) and 3.5 (5)] which were prepared by using the mononuclear PPh(4)[Fe(III)(dmbpy)(CN)(4)]·3H(2)O (1) building block (PPh(4)(+) = tetraphenylphosphonium) as a ligand toward fully solvated M(II) ions. The structure of 1 consists of discrete [Fe(III)(dmbpy)(CN)(4)](-) anions, tetraphenylphosphonium cations and noncoordinated water molecules. Complexes 2-5 are isostructural compounds whose structure consists of neutral 4,2-wave like heterobimetallic chains of formula {[Fe(III)(dmbpy)(CN)(4)](2)M(II)(H(2)O)(2)}(n) where the [Fe(III)(dmbpy)(CN)(4)](-) entity adopts a bis-monodentate coordination mode toward trans-[M(II)(H(2)O)(2)] units through two of its four cyanide groups in cis positions. 1 exhibits the magnetic behaviour of magnetically isolated six-coordinate low-spin Fe(III) complexes with an important orbital contribution. 2 behaves as ferrimagnetic Fe(III)(2)Mn(II) chains, whereas 3-5 exhibit intrachain ferromagnetic couplings between the low-spin Fe(III) and either Cu(II) (3), Ni (4) or Co(II) (5) as well as frequency-dependence of the out-of-phase ac susceptibility signals below 3.0 (3), 5.5 (4) and 5.0 K (5). The relaxation time and the energy to reverse the magnetization of 3-5 are related to the anisotropy of the M(II) center and to the intra- and interchain magnetic interactions. Unprecedentedly in the world of cyanide-bearing complexes, 5 exhibits a double slow relaxation of the magnetization.

Self-assembled monolayers of n-alkanethiols suppress hydrogen evolution and increase the efficiency of rechargeable iron battery electrodes.

PubMed

Malkhandi, Souradip; Yang, Bo; Manohar, Aswin K; Prakash, G K Surya; Narayanan, S R

2013-01-09

Iron-based rechargeable batteries, because of their low cost, eco-friendliness, and durability, are extremely attractive for large-scale energy storage. A principal challenge in the deployment of these batteries is their relatively low electrical efficiency. The low efficiency is due to parasitic hydrogen evolution that occurs on the iron electrode during charging and idle stand. In this study, we demonstrate for the first time that linear alkanethiols are very effective in suppressing hydrogen evolution on alkaline iron battery electrodes. The alkanethiols form self-assembled monolayers on the iron electrodes. The degree of suppression of hydrogen evolution by the alkanethiols was found to be greater than 90%, and the effectiveness of the alkanethiol increased with the chain length. Through steady-state potentiostatic polarization studies and impedance measurements on high-purity iron disk electrodes, we show that the self-assembly of alkanethiols suppressed the parasitic reaction by reducing the interfacial area available for the electrochemical reaction. We have modeled the effect of chain length of the alkanethiol on the surface coverage, charge-transfer resistance, and double-layer capacitance of the interface using a simple model that also yields a value for the interchain interaction energy. We have verified the improvement in charging efficiency resulting from the use of the alkanethiols in practical rechargeable iron battery electrodes. The results of battery tests indicate that alkanethiols yield among the highest faradaic efficiencies reported for the rechargeable iron electrodes, enabling the prospect of a large-scale energy storage solution based on low-cost iron-based rechargeable batteries.

Two isotypic diphosphates LiM{sub 2}H{sub 3}(P{sub 2}O{sub 7}){sub 2} (M=Ni, Co) containing ferromagnetic zigzag MO{sub 6} chains

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

Yang Tao; Yang Sihai; Liao Fuhui

2008-06-15

Two new isotypic phosphates LiNi{sub 2}H{sub 3}(P{sub 2}O{sub 7}){sub 2} (1) and LiCo{sub 2}H{sub 3}(P{sub 2}O{sub 7}){sub 2} (2) have been hydrothermally synthesized and structurally characterized by the single-crystal X-ray diffraction technique. They crystallize in the monoclinic space group C2/c with the lattice: a=10.925(2) A, b=12.774(3) A, c=8.8833(18) A, {beta}=123.20(3){sup o} for 1 and a=10.999(2) A, b=12.863(3) A, c=8.9419(18) A, {beta}=123.00(3){sup o} for 2. The transition metal atoms are octahedrally coordinated, whereas the lithium and phosphorus atoms are all tetrahedrally coordinated. As the lithium-induced derivatives of MH{sub 2}P{sub 2}O{sub 7} (M=Ni, Co), 1 and 2 possess the same structure withmore » MH{sub 2}P{sub 2}O{sub 7} in terms of topology, comprising the MO{sub 6} zigzag chains and P{sub 2}O{sub 7} as the interchain groups. The magnetisms of 1 and 2 could be interpreted by adopting a quasi-one-dimensional (1D) zigzag chain model as that in their parent compounds: both 1 and 2 have ferromagnetic (FM) NiO{sub 6}/CoO{sub 6} chains; 1 shows a FM cluster glass behavior at low temperatures, which is originated from the possible antiferromagnetic (AFM) next-nearest-neighbour intrachain interactions; 2 shows a AFM ordering at T{sub N}=2.6 K and a metamagnetic transition at H{sub C}=4.2 kOe at 1.8 K. - Graphical abstract: LiNi{sub 2}H{sub 3}(P{sub 2}O{sub 7}){sub 2} (1) and LiCo{sub 2}H{sub 3}(P{sub 2}O{sub 7}){sub 2} (2) have been hydrothermally synthesized and structurally characterized. The MO{sub 6} octahedra share edges forming zigzag chains with P{sub 2}O{sub 7} as the interchain groups. Both of them are quasi-one-dimensional magnets and have ferromagnetic MO{sub 6} chains; 1 is a ferromagnet, whereas 2 is a metamagnet.« less

The pH-dependent elastic properties of nanoscale DNA films and the resultant bending signals for microcantilever biosensors.

PubMed

Zhou, Mei-Hong; Meng, Wei-Lie; Zhang, Cheng-Yin; Li, Xiao-Bin; Wu, Jun-Zheng; Zhang, Neng-Hui

2018-04-25

The diverse mechanical properties of nanoscale DNA films on solid substrates have a close correlation with complex detection signals of micro-/nano-devices. This paper is devoted to formulating several multiscale models to study the effect of pH-dependent ionic inhomogeneity on the graded elastic properties of nanoscale DNA films and the resultant bending deflections of microcantilever biosensors. First, a modified inverse Debye length is introduced to improve the classical Poisson-Boltzmann equation for the electrical potential of DNA films to consider the inhomogeneous effect of hydrogen ions. Second, the graded characteristics of the particle distribution are taken into consideration for an improvement in Parsegian's mesoscopic potential for both attraction-dominated and repulsion-dominated films. Third, by the improved interchain interaction potential and the thought experiment about the compression of a macroscopic continuum DNA bar, we investigate the diversity of the elastic properties of single-stranded DNA (ssDNA) films due to pH variations. The relevant theoretical predictions quantitatively or qualitatively agree well with the relevant DNA experiments on the electrical potential, film thickness, condensation force, elastic modulus, and microcantilever deflections. The competition between attraction and repulsion among the fixed charges and the free ions endows the DNA film with mechanical properties such as a remarkable size effect and a non-monotonic behavior, and a negative elastic modulus is first revealed in the attraction-dominated ssDNA film. There exists a transition between the pH-sensitive parameter interval and the pH-insensitive one for the bending signals of microcantilevers, which is predominated by the initial stress effect in the DNA film.

Small-angle neutron scattering study of a monoclonal antibody using free-energy constraints.

PubMed

Clark, Nicholas J; Zhang, Hailiang; Krueger, Susan; Lee, Hyo Jin; Ketchem, Randal R; Kerwin, Bruce; Kanapuram, Sekhar R; Treuheit, Michael J; McAuley, Arnold; Curtis, Joseph E

2013-11-14

Monoclonal antibodies (mAbs) contain hinge-like regions that enable structural flexibility of globular domains that have a direct effect on biological function. A subclass of mAbs, IgG2, have several interchain disulfide bonds in the hinge region that could potentially limit structural flexibility of the globular domains and affect the overall configuration space available to the mAb. We have characterized human IgG2 mAb in solution via small-angle neutron scattering (SANS) and interpreted the scattering data using atomistic models. Molecular Monte Carlo combined with molecular dynamics simulations of a model mAb indicate that a wide range of structural configurations are plausible, spanning radius of gyration values from ∼39 to ∼55 Å. Structural ensembles and representative single structure solutions were derived by comparison of theoretical SANS profiles of mAb models to experimental SANS data. Additionally, molecular mechanical and solvation free-energy calculations were carried out on the ensemble of best-fitting mAb structures. The results of this study indicate that low-resolution techniques like small-angle scattering combined with atomistic molecular simulations with free-energy analysis may be helpful to determine the types of intramolecular interactions that influence function and could lead to deleterious changes to mAb structure. This methodology will be useful to analyze small-angle scattering data of many macromolecular systems.

Physics and capabilities of terahertz spectroscopy to study the water-biomolecule interaction

NASA Astrophysics Data System (ADS)

Vezzoli, G. C.

2007-09-01

We have conducted the first study of the use of terahertz radiation to precisely identify pre-melting, melting, polymerization, depolymerization and the influence of polar water in sulfur by scanning frequency as a parametric function of temperature, and including identifying precursor and intermediate states. This spectroscopic study has also identified the orthorhombic-monoclinic phase transformation, and the melting of the superheated orthorhombic phase. This work also reports detection of a water absorption indicating a perturbation of the water molecules, associated with solvation spheres of the inter-chain dynamics, as a precursor to a transition, and supporting our earlier results showing the transducing capabilities of conglomerates of water molecules. Through a study of the fine structure of the water absorption, we are able to determine information about local polarization effects which contribute to the transducing properties of water relative to a ligand. The above inorganic polymer study is applied to the understanding of the response of biomolecules to thermal and chemical influences, and data are included giving optical, electrical, and pH properties of the DNA-water system, showing a major conformational transition at ~43°C, and various forms of reconformation of DNA macromolecule due to chemical perturbation. Our results include findings aimed at complementing existing inhibitors that are intended to prevent retrovirus/phage invasion of the host cell DNA.

Dynamics of CO2 scattering off a perfluorinated self-assembled monolayer. Influence of the incident collision energy, mass effects, and use of different surface models.

PubMed

Nogueira, Juan J; Vázquez, Saulo A; Mazyar, Oleg A; Hase, William L; Perkins, Bradford G; Nesbitt, David J; Martínez-Núñez, Emilio

2009-04-23

The dynamics of collisions of CO2 with a perfluorinated alkanethiol self-assembled monolayer (F-SAM) on gold were investigated by classical trajectory calculations using explicit atom (EA) and united atom (UA) models to represent the F-SAM surface. The CO2 molecule was directed perpendicularly to the surface at initial collision energies of 1.6, 4.7, 7.7, and 10.6 kcal/mol. Rotational distributions of the scattered CO2 molecules are in agreement with experimental distributions determined for collisions of CO2 with liquid surfaces of perfluoropolyether. The agreement is especially good for the EA model. The role of the mass in the efficiency of the energy transfer was investigated in separate simulations in which the mass of the F atoms was replaced by either that of hydrogen or chlorine, while keeping the potential energy function unchanged. The calculations predict the observed trend that less energy is transferred to the surface as the mass of the alkyl chains increases. Significant discrepancies were found between results obtained with the EA and UA models. The UA surface leads to an enhancement of the energy transfer efficiency in comparison with the EA surface. The reason for this is in the softer structure of the UA surface, which facilitates transfer from translation to interchain vibrational modes.

Structural study of the effects of mutations in proteins to identify the molecular basis of the loss of local structural fluidity leading to the onset of autoimmune diseases.

PubMed

Ali, Ananya; Ghosh, Semanti; Bagchi, Angshuman

2017-02-26

Protein-Protein Interactions (PPIs) are crucial in most of the biological processes and PPI dysfunctions are known to be associated with the onsets of various diseases. One of such diseases is the auto-immune disease. Auto-immune diseases are one among the less studied group of diseases with very high mortality rates. Thus, we tried to correlate the appearances of mutations with their probable biochemical basis of the molecular mechanisms leading to the onset of the disease phenotypes. We compared the effects of the Single Amino Acid Variants (SAVs) in the wild type and mutated proteins to identify any structural deformities that might lead to altered PPIs leading ultimately to disease onset. For this we used Relative Solvent Accessibility (RSA) as a spatial parameter to compare the structural perturbation in mutated and wild type proteins. We observed that the mutations were capable to increase intra-chain PPIs whereas inter-chain PPIs would remain mostly unaltered. This might lead to more intra-molecular friction causing a deleterious alteration of protein's normal function. A Lyapunov exponent analysis, using the altered RSA values due to polymorphic and disease causing mutations, revealed polymorphic mutations have a positive mean value for the Lyapunov exponent while disease causing mutations have a negative mean value. Thus, local spatial stochasticity has been lost due to disease causing mutations, indicating a loss of structural fluidity. The amino acid conversion plot also showed a clear tendency of altered surface patch residue conversion propensity than polymorphic conversions. So far, this is the first report that compares the effects of different kinds of mutations (disease and non-disease causing polymorphic mutations) in the onset of autoimmune diseases. Copyright © 2017 Elsevier Inc. All rights reserved.

The role of strong electrostatic interactions at the dimer interface of human glutathione synthetase.

PubMed

De Jesus, Margarita C; Ingle, Brandall L; Barakat, Khaldoon A; Shrestha, Bisesh; Slavens, Kerri D; Cundari, Thomas R; Anderson, Mary E

2014-10-01

The obligate homodimer human glutathione synthetase (hGS) provides an ideal system for exploring the role of protein-protein interactions in the structural stability, activity and allostery of enzymes. The two active sites of hGS, which are 40 Å apart, display allosteric modulation by the substrate γ-glutamylcysteine (γ-GC) during the synthesis of glutathione, a key cellular antioxidant. The two subunits interact at a relatively small dimer interface dominated by electrostatic interactions between S42, R221, and D24. Alanine scans of these sites result in enzymes with decreased activity, altered γ-GC affinity, and decreased thermal stability. Molecular dynamics simulations indicate these mutations disrupt interchain bonding and impact the tertiary structure of hGS. While the ionic hydrogen bonds and salt bridges between S42, R221, and D24 do not mediate allosteric communication in hGS, these interactions have a dramatic impact on the activity and structural stability of the enzyme.

Few Ramachandran Angle Changes Provide Interaction Strength Increase in Aβ42 versus Aβ40 Amyloid Fibrils

NASA Astrophysics Data System (ADS)

Bastidas, Oscar H.; Green, Benjamin; Sprague, Mary; Peters, Michael H.

2016-11-01

The pathology of Alzheimer’s disease can ultimately be traced to the increased aggregation stability of Aβ42 peptides which possess two extra residues (Ile 41 & Ala 42) that the non-pathological strain (Aβ40) lacks. We have found Aβ42 fibrils to exhibit stronger energies in inter-chain interactions and we have also identified the cause for this increase to be the result of different Ramachandran angle values in certain residues of the Aβ42 strain compared to Aβ40. These unique angle configurations result in the peptide planes in the fibril structures to be more vertical along the fibril axis for Aβ42 which thus reduces the inter-atomic distance between interacting atoms on vicinal peptide chains thereby increasing the electrostatic interaction energies. We lastly postulate that these different Ramachandran angle values could possibly be traced to the unique conformational folding avenues sampled by the Aβ42 peptide owing to the presence of its two extra residues.

Process for preparing essentially colorless polyimide film containing phenoxy-linked diamines

NASA Technical Reports Server (NTRS)

Stclair, A. K.; Stclair, T. L.

1986-01-01

A polyimide film that is approximately 90% transparent at 500 nm, useful for thermal protective coatings and solar cells, and the processes for preparing the same by thermal and chemical conversion are disclosed. An essential feature for achieving maximum optical transparency films requires utilizing recrystallized and/or sublimated specific aromatic diamines and dianhydride monomers and introducing phenoxy or thiophenyl separator groups and isomeric m,m' or o,p'-oriented diamines into the polymer molecular structure. The incorporation of these groups in the polymer structure serves to separate the chromaphoric centers and reduce the formation of inter-chain and intra-chain charge transfer complexes which normally cause absorptions in the UV-visible range. The films may be obtained by hand, brushing, casting, or spraying a layer of polyamic acid solutions onto a surface and thermally converting the applied layer to the polyimide, or the polyamic acid solution can be chemically converted to the polyimide, subsequentially dissolved in an organic solvent, and applied as a polyimide film layer with the solvent therein thermally removed.

Structure of Se-Te glasses studied using neutron, X-ray diffraction and reverse Monte Carlo modelling

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

Itoh, Keiji, E-mail: itoh@okayama-u.ac.jp; Research Reactor Institute, Kyoto University, Kumatori, Osaka 590-0494

Pulsed neutron diffraction and synchrotron X-ray diffraction measurements were performed on Se{sub 100-x}Te{sub x} bulk glasses with x=10, 20, 30 and 40. The coordination numbers obtained from the diffraction results demonstrate that Se and Te atoms are twofold coordinated and the glass structure is formed by the chain network. The three-dimensional structure model for Se{sub 60}Te{sub 40} glass obtained by using reverse Monte Carlo modelling shows that the alternating arrangements of Se and Te atoms compose the major part of the chain clusters but several other fragments such as Se{sub n} chains and Te-Te dimers are also present in largemore » numbers. The chain clusters have geometrically disordered forms and the interchain atomic order is different from those in the crystal structures of trigonal Se and trigonal Te. - Graphical abstract: Coordination environment in Se{sub 60}Te{sub 40} glass.« less

Dual chain perturbation theory: A new equation of state for polyatomic molecules

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

Marshall, Bennett D., E-mail: bennett.d.marshall@exxonmobil.com

In the development of equations of state for polyatomic molecules, thermodynamic perturbation theory (TPT) is widely used to calculate the change in free energy due to chain formation. TPT is a simplification of a more general and exact multi-density cluster expansion for associating fluids. In TPT, all contributions to the cluster expansion which contain chain–chain interactions are neglected. That is, all inter-chain interactions are treated at the reference fluid level. This allows for the summation of the cluster theory in terms of reference system correlation functions only. The resulting theory has been shown to be accurate and has been widelymore » employed as the basis of many engineering equations of state. While highly successful, TPT has many handicaps which result from the neglect of chain–chain contributions. The subject of this document is to move beyond the limitations of TPT and include chain–chain contributions to the equation of state.« less

Comparative study on the freeze stability of yeast and chemical leavened steamed bread dough.

PubMed

Wang, Pei; Yang, Runqiang; Gu, Zhenxin; Xu, Xueming; Jin, Zhengyu

2017-04-15

The present study comparatively evaluated the evolution of yeast and chemical leavened steamed bread dough (YLD/CLD) quality during freeze/thaw (FT) cycles. The steamed bread quality of CLD was more freeze-stable than that of the YLD after 3 FT cycles. Decreased yeast viability contributed to the loss of gassing power in YLD while no significant differences were observed for CLD during FT cycles. However, faster gas release rate in frozen CLD indicated gas retention loss due to the distortion of gluten network. Glutenin macropolymers (GMP) depolymerization via breakage of inter-chain disulfide (SS) bonds and conversions of α-helix and β-turn to β-sheet structures were the main indicators of gluten deterioration. Gluten network was more vulnerable in frozen YLD, resulting in detectable loss of viscoelasticity. The results suggested that supplement of chemical leavener contributed to a more freeze-tolerant gluten network besides its stable gassing power. Copyright © 2016 Elsevier Ltd. All rights reserved.

A switch in disulfide linkage during minicollagen assembly in Hydra nematocysts.

PubMed

Engel, U; Pertz, O; Fauser, C; Engel, J; David, C N; Holstein, T W

2001-06-15

The smallest known collagens with only 14 Gly-X-Y repeats referred to as minicollagens are the main constituents of the capsule wall of nematocysts. These are explosive organelles found in Hydra, jellyfish, corals and other Cnidaria. Minicollagen-1 of Hydra recombinantly expressed in mammalian 293 cells contains disulfide bonds within its N- and C-terminal Cys-rich domains but no interchain cross-links. It is soluble and self-associates through non-covalent interactions to form 25-nm-long trimeric helical rod-like molecules. We have used a polyclonal antibody prepared against the recombinant protein to follow the maturation of minicollagens from soluble precursors present in the endoplasmic reticulum and post-Golgi vacuoles to the disulfide-linked insoluble assembly form of the wall. The switch from intra- to intermolecular disulfide bonds is associated with 'hardening' of the capsule wall and provides an explanation for its high tensile strength and elasticity. The process is comparable to disulfide reshuffling between the NC1 domains of collagen IV in mammalian basement membranes.

Magnetic behavior of the ferromagnetic quantum chain systems (C6H11NH3)CuCl3 (CHAC) and (C6H11NH3)CuBr3 (CHAB)

NASA Astrophysics Data System (ADS)

Kopinga, A.; Tinus, A. M. C.; de Jonge, W. J. M.

1982-04-01

Heat-capacity measurements on (C6H11NH3)CuBr3 (CHAB) in the region 0.45 < T<55 K are presented. Three-dimensional ordering is observed at Tc=1.50 K. The data are analyzed together with previously reported measurements on (C6H11NH3)CuCl3 (CHAC). Both compounds appear to be very good approximations of a ferromagnetic S=12 Heisenberg linearchain system with Jk~50 K. From the data it is inferred that the intrachain interaction of CHAC contains about 2% uniaxial anisotropy, whereas CHAB contains about 5% easy-plane anisotropy. The results are corroborated by magnetization measurements on CHAB below Tc, which also reveal a metamagnetic transition for H-->∥b (Hc=210Oe). From the value of Hc and the location of the tricitical point the interchain interactions in CHAB were found as zAFJAFk=-0.03 K, zFJFk~0.08 K.

Radiation processing of thermoplastic starch by blending aromatic additives: Effect of blend composition and radiation parameters

NASA Astrophysics Data System (ADS)

Khandal, Dhriti; Mikus, Pierre-Yves; Dole, Patrice; Coqueret, Xavier

2013-03-01

This paper reports on the effects of electron beam (EB) irradiation on poly α-1,4-glucose oligomers (maltodextrins) in the presence of water and of various aromatic additives, as model blends for gaining a better understanding at a molecular level the modifications occurring in amorphous starch-lignin blends submitted to ionizing irradiation for improving the properties of this type of bio-based thermoplastic material. A series of aromatic compounds, namely p-methoxy benzyl alcohol, benzene dimethanol, cinnamyl alcohol and some related carboxylic acids namely cinnamic acid, coumaric acid, and ferulic acid, was thus studied for assessing the ability of each additive to counteract chain scission of the polysaccharide and induce interchain covalent linkages. Gel formation in EB-irradiated blends comprising of maltodextrin was shown to be dependent on three main factors: the type of aromatic additive, presence of glycerol, and irradiation dose. The chain scission versus grafting phenomenon as a function of blend composition and dose were studied using Size Exclusion Chromatography by determining the changes in molecular weight distribution (MWD) from Refractive Index (RI) chromatograms and the presence of aromatic grafts onto the maltodextrin chains from UV chromatograms. The occurrence of crosslinking was quantified by gel fraction measurements allowing for ranking the cross-linking efficiency of the additives. When applying the method to destructurized starch blends, gel formation was also shown to be strongly affected by the moisture content of the sample submitted to irradiation. The results demonstrate the possibility to tune the reactivity of tailored blend for minimizing chain degradation and control the degree of cross-linking.

Higher Molecular Weight Leads to Improved Photoresponsivity Charge Transport and Interfacial Ordering in a Narrow Bandgap Semiconducting Polymer

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

M Tong; S Cho; J Rogers

2011-12-31

Increasing the molecular weight of the low-bandgap semiconducting copolymer, poly[(4,4-didoecyldithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl], Si-PDTBT, from 9 kDa to 38 kDa improves both photoresponsivity and charge transport properties dramatically. The photocurrent measured under steady state conditions is 20 times larger in the higher molecular weight polymer (HM{sub n} Si-PDTBT). Different decays of polarization memory in transient photoinduced spectroscopy measurements are consistent with more mobile photoexcitations in HM{sub n} Si-PDTBT relative to the lower molecular weight counterpart (LM{sub n} Si-PDTBT). Analysis of the current-voltage characteristics of field effect transistors reveals an increase in the mobility by a factor of 700 for HM{sub n} Si-PDTBT. Nearmore » edge X-ray absorption fine structure (NEXAFS) spectroscopy and grazing incidence small angle X-ray scattering (GISAXS) measurements demonstrate that LM{sub n} Si-PDTBT forms a disordered morphology throughout the depth of the film, whereas HM{sub n} Si-PDTBT exhibits pronounced {pi}-{pi} stacking in an edge-on configuration near the substrate interface. Increased interchain overlap between polymers in the edge-on configuration in HM{sub n} Si-PDTBT results in the higher carrier mobility. The improved optical response, transport mobility, and interfacial ordering highlight the subtle role that the degree of polymerization plays on the optoelectronic properties of conjugated polymer based organic semiconductors.« less

Ordered bimetallic ferromagnets of chromium(III): [Cr(NH 3) 6][Cr(CN) 6], [Cr(H 2O)(NH 3) 5][Cr(CN) 6], and trans-[Cr(en) 2(H 2O) 2]trans-[Cr(en) 2(OH)F] 2(CIO 4) 5·2H 2O

NASA Astrophysics Data System (ADS)

Burriel, Ramón; Casabó, Jaime; Pons, Josefina; Carnegie, David W.; Carlin, Richard L.

1985-07-01

The magnetic bahavior of the isomorphous compounds [Cr(NH 3) 6][Cr(CN) 6] and [Cr(H 2O)(NH 3) 5][Cr(CN) 6] has been studied by means of zero-field susceptibility measurements. The materials order ferromagnetically at 0.60 and 0.38K, respectively. The compounds behave as examples of the ferromagnetic ( S=3/2) Heisenberg body-center-cubic lattice. The susceptibilities have been analyzed and compared to the Padé approximants of the high-temperature series expansion for this model, a remarkably good fit being obtained with exchange constants 0.042 and 0.022 K, respectively. Another bimetallic substance, trans-[Cr(en) 2(H 2O) 2] trans-[Cr(en) 2(OH)F] 2(CIO 4) 5·2H 2O, with a dominant Heisenberg ferromagnetic interaction J/ kB=0.122 K in one dimension, orders antiferromagnetically at 0.14 K due to a weaker interchain interaction with exchange constant z‧ J‧/ kB=-0.019 K. The three sets of measurements have been carried out on powdered samples for which demagnetization effects are important. The exchange interactions are remarkably weak for such concentrated magnetic materials, yet they are stronger than those found in a number of other such Cr/Cr compounds.

Top-Down Charge Transfer Dissociation (CTD) of Gas-Phase Insulin: Evidence of a One-Step, Two-Electron Oxidation Mechanism

NASA Astrophysics Data System (ADS)

Li, Pengfei; Kreft, Iris; Jackson, Glen P.

2018-02-01

Top-down analyses of protonated insulin cations of charge states of 4+, 5+, or 6+ were performed by exposing the isolated precursor ions to a beam of helium cations with kinetic energy of more than 6 keV, in a technique termed charge transfer dissociation (CTD). The 100 ms charge transfer reaction resulted in approximately 20% conversion efficiency to other intact charge exchange products (CTnoD), and a range of low abundance fragment ions. To increase backbone and sulfide cleavages, and to provide better structural information than straightforward MS2 CTD, the CTnoD oxidized products were isolated and subjected to collisional activation at the MS3 level. The MS3 CTD/CID reaction effectively broke the disulfide linkages, separated the two chains, and yielded more structurally informative fragment ions within the inter-chain cyclic region. CTD also provided doubly oxidized intact product ions at the MS2 level, and resonance ejection of the singly oxidized product ion revealed that the doubly oxidized product originates directly from the isolated precursor ion and not from consecutive CTD reactions of a singly oxidized intermediate. MS4 experiments were employed to help identify potential radical cations and diradical cations, but the results were negative or inconclusive. Nonetheless, the two-electron oxidation process is a demonstration of the very large potential energy (>20 eV) available through CTD, and is a notable capability for a 3D ion trap platform.

Collagen Gly missense mutations: Effect of residue identity on collagen structure and integrin binding.

PubMed

Qiu, Yimin; Mekkat, Arya; Yu, Hongtao; Yigit, Sezin; Hamaia, Samir; Farndale, Richard W; Kaplan, David L; Lin, Yu-Shan; Brodsky, Barbara

2018-05-11

Gly missense mutations in type I collagen, which replace a conserved Gly in the repeating (Gly-Xaa-Yaa) n sequence with a larger residue, are known to cause Osteogenesis Imperfecta (OI). The clinical consequences of such mutations range from mild to lethal, with more serious clinical severity associated with larger Gly replacement residues. Here, we investigate the influence of the identity of the residue replacing Gly within and adjacent to the integrin binding 502 GFPGER 507 sequence on triple-helix structure, stability and integrin binding using a recombinant bacterial collagen system. Recombinant collagens were constructed with Gly substituted by Ala, Ser or Val at four positions within the integrin binding region. All constructs formed a stable triple-helix structure with a small decrease in melting temperature. Trypsin was used to probe local disruption of the triple helix, and Gly to Val replacements made the triple helix trypsin sensitive at three of the four sites. Any mutation at Gly505, eliminated integrin binding, while decreased integrin binding affinity was observed in the replacement of Gly residues at Gly502 following the order Val > Ser > Ala. Molecular dynamics simulations indicated that all Gly replacements led to transient disruption of triple-helix interchain hydrogen bonds in the region of the Gly replacement. These computational and experimental results lend insight into the complex molecular basis of the varying clinical severity of OI. Copyright © 2018. Published by Elsevier Inc.

Effect of chitosan and thiolated chitosan coating on the inhibition behaviour of PIBCA nanoparticles against intestinal metallopeptidases

NASA Astrophysics Data System (ADS)

Bravo-Osuna, Irene; Vauthier, Christine; Farabollini, Alessandra; Millotti, Gioconda; Ponchel, Gilles

2008-12-01

Surface modified nanoparticles composed of poly(isobutylcyanoacrylate) (PIBCA) cores surrounded by a chitosan and thiolated chitosan gel layer were prepared and characterized in previous works. The presence of such biopolymers on the nanoparticle surface conferred those nanosystems interesting characteristics that might partially overcome the gastrointestinal enzymatic barrier, improving the oral administration of pharmacologically active peptides. In the present work, the antiprotease behaviour of this family of core-shell nanoparticles was in vitro tested against two model metallopeptidases present in the gastrointestinal tract (GIT): Carboxypeptidase A -CP A- (luminal protease) and Leucine Aminopeptidase M -LAP M- (membrane protease). As previous step, the zinc-binding capacity of these nanoparticles was evaluated. Interestingly, an improvement of both the zinc-binding capacity and the antiprotease effect of chitosan was observed when the biopolymers (chitosan and thiolated chitosan) were used as coating component of the core-shell nanoparticles, in comparison with their behaviour in solution, thanks to the different biopolymer chains rearrangement. The presence of amino, hydroxyl and thiol groups on the nanoparticle surface promoted zinc binding and hence the inhibition of the metallopeptidases analysed. On the contrary, the occurrence of a cross-linked structure in the gel layer surrounding the PIBCA cores of thiolated formulations, due to the formation of interchain and intrachain disulphide bonds, partially limited the inhibition of the proteases. The low accessibility of cations to the active groups of the cross-linked polymeric shell was postulated as a possible explanation of this behaviour. Results obtained in this work make this family of surface-modified nanocarriers promising candidates for the successfull administration of pharmacologically active peptides and proteins by the oral route.

Effect of regioregularity on recombination dynamics in inverted bulk heterojunction organic solar cells

NASA Astrophysics Data System (ADS)

Chandrasekaran, Naresh; Liu, Amelia C. Y.; Kumar, Anil; McNeill, Christopher R.; Kabra, Dinesh

2018-01-01

The effect of polymer regioregularity on the charge transport properties and bimolecular recombination rates of polymer-based solar cells is studied in detail using transient photovoltaic techniques. We compare organic solar cells fabricated with an ITO/ZnO/PEIE/P3HT:PCBM/MoO3/Ag structure using either 100% regioregular poly(3-hexylthiophene) (DF-P3HT) yielding an average power conversion efficiency (PCE) of 3.8  ±  0.3% or 92% regioregular P3HT (rr-P3HT) that yields an average PCE of 3.28  ±  0.4%. Transient photocurrent measurements reveal the presence of less mobile photoinduced charges in rr-P3HT:PCBM cells when compared to DF-P3HT:PCBM solar cells. Transient photovoltage measurements are used to establish the relationship between regioregularity and bimolecular recombination rate constant (k) finding that under 1 Sun, devices with high regioregularity have a longer τ despite having a higher k. The high value of k for the DF-P3HT:PCBM system as compared to the rr-P3HT:PCBM system is attributed to enhanced mobility and better charge transport of mobile charges in the DF-P3HT:PCBM system, consistent with enhanced fibrillar order in DF-P3HT films observed with transmission electron microscopy. We also note a slight decrease in cell open circuit voltage with increase in polymer regioregularity, which is due to the increase in k. Other recombination mechanisms such as trap-assisted recombination are found to be important in the lower regioregular P3HT device compounded by the reduced mobility and poor inter-chain ordering.

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

Peteanu, Linda A.; Chowdhury, Sanchari; Wildeman, Jurjen

One measure of exciton mobility in an aggregate is the efficiency of exciton–exciton annihilation (EEA). Both exciton mobilities and EEA are enhanced for aggregate morphologies in which the distances between chromophores and their relative orientations are favorable for Förster energy transfer. Here this principle is applied to gauge the strength of interchain interactions in aggregates of two substituted PPV oligomers of 7 (OPPV7) and 13 (OPPV13) phenylene rings. These are models of the semiconducting conjugated polymer MEH–PPV. The aggregates were formed by adding a poor solvent (methanol or water) to the oligomers dissolved in a good solvent. Aggregates formed frommore » the longer-chain oligomer and/or by addition of the more polar solvent showed the largest contribution of EEA in their emission decay dynamics. This was found to correlate with the degree to which the steady-state emission spectrum of the monomer is altered by aggregation. Furthermore, the wavelength dependence of the EEA signal was also shown to be useful in differentiating emission features due to monomeric and aggregated chains when their spectra overlap significantly.« less

Heterogeneity in iota-carrageenan molecular structure: insights for polymorph II→III transition in the presence of calcium ions

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

Janaswamy, Srinivas; Chandrasekaran, Rengaswami

2008-06-24

Iota-carrageenan is used in pharmaceutical and food applications due to its ability to complex with other hydrocolloids and proteins. Six distinct cation dependent allomorphs, consistent with its versatile functionality, have so far been observed in the solid state. In this contribution, X-ray structural details of calcium iota-carrageenan (form III) are reported. The polysaccharide retains the half-staggered, parallel, 3-fold, right-handed double helix stabilized by interchain hydrogen bonds from O-2H and O-6H in the Galp units. Results show that there are four helices, rather than one in I or three in II, organized in a larger pseudo-trigonal unit cell of dimensions a=27.44,more » c=13.01 A, and gamma=120 degrees . The four helices have similar core structures, but their sulfate group orientations are quite different. Fifteen calcium ions and 64 water molecules hold the helices together and promote helix-helix interactions. The results portray how the helices would shuffle around in an orchestrated manner to yield calcium iota-carrageenan III from II.« less

Nano-Assemblies of Modified Cyclodextrins and Their Complexes with Guest Molecules: Incorporation in Nanostructured Membranes and Amphiphile Nanoarchitectonics Design

PubMed Central

Zerkoune, Leïla; Angelova, Angelina; Lesieur, Sylviane

2014-01-01

A variety of cyclodextrin-based molecular structures, with substitutions of either primary or secondary faces of the natural oligosaccharide macrocycles of α-, β-, or γ-cyclodextrins, have been designed towards innovative applications of self-assembled cyclodextrin nanomaterials. Amphiphilic cyclodextrins have been obtained by chemical or enzymatic modifications of their macrocycles using phospholipidyl, peptidolipidyl, cholesteryl, and oligo(ethylene oxide) anchors as well as variable numbers of grafted hydrophobic hydrocarbon or fluorinated chains. These novel compounds may self-assemble in an aqueous medium into different types of supramolecular nanoassemblies (vesicles, micelles, nanorods, nanospheres, and other kinds of nanoparticles and liquid crystalline structures). This review discusses the supramolecular nanoarchitectures, which can be formed by amphiphilic cyclodextrin derivatives in mixtures with other molecules (phospholipids, surfactants, and olygonucleotides). Biomedical applications are foreseen for nanoencapsulation of drug molecules in the hydrophobic interchain volumes and nanocavities of the amphiphilic cyclodextrins (serving as drug carriers or pharmaceutical excipients), anticancer phototherapy, gene delivery, as well as for protection of instable active ingredients through inclusion complexation in nanostructured media. PMID:28344245

Universal ultrafast signatures of photoexcitations in conjugated polymers: excitons and charge-transfer polarons

NASA Astrophysics Data System (ADS)

McBranch, Duncan W.; Kraabel, Brett; Xu, Su; Wang, Hsing-Lin; Klimov, Victor I.

1999-12-01

Using subpicosecond transient absorption spectroscopy, we have investigated the primary photoexcitations in thin films and solution of several phenylene-based conjugated polymers and an oligomer. We identify two features in the transient absorption spectra and dynamics that are common to all of the materials which we have studied from this family. The first spectral feature is a photoinduced absorption (PA) band peaking near 1 eV which has intensity-dependent dynamics which match the stimulated emission dynamics exactly over two orders of magnitude in excitation density. This band is associated with singlet intrachain excitons. The second spectral feature (observed only in thin films and aggregated solutions) is a PA band peaking near 1.8 eV, which is longer-lived than the 1 eV exciton PA band, and which has dynamics that are independent (or weakly-dependent) on excitation density. This feature is attributed to charge separated (interchain) excitations. These excitations are generated through a bimolecular process. By comparing to samples in which charged excitations are created deliberately by doping with C6O, we assign these secondary species as bound polarons.

Cellulose microfibril formation within a coarse grained molecular dynamics

NASA Astrophysics Data System (ADS)

Nili, Abdolmadjid; Shklyaev, Oleg; Crespi, Vincent; Zhao, Zhen; Zhong, Linghao; CLSF Collaboration

2014-03-01

Cellulose in biomass is mostly in the form of crystalline microfibrils composed of 18 to 36 parallel chains of polymerized glucose monomers. A single chain is produced by cellular machinery (CesA) located on the preliminary cell wall membrane. Information about the nucleation stage can address important questions about intermediate region between cell wall and the fully formed crystalline microfibrils. Very little is known about the transition from isolated chains to protofibrils up to a full microfibril, in contrast to a large body of studies on both CesA and the final crystalline microfibril. In addition to major experimental challenges in studying this transient regime, the length and time scales of microfibril nucleation are inaccessible to atomistic molecular dynamics. We have developed a novel coarse grained model for cellulose microfibrils which accounts for anisotropic interchain interactions. The model allows us to study nucleation, kinetics, and growth of cellulose chains/protofibrils/microfibrils. This work is supported by the US Department of Energy, Office of Basic Energy Sciences as part of The Center for LignoCellulose Structure and Formation, an Energy Frontier Research Center.

Dual responsive supramolecular hydrogel with electrochemical activity.

PubMed

Du, Ping; Liu, Jianghua; Chen, Guosong; Jiang, Ming

2011-08-02

Supramolecular materials with reversible responsiveness to environmental changes are of particular research interest in recent years. Inclusion complexation between cyclodextrin (CD) and ferrocene (Fc) is well-known and extensively studied because of its reversible association-dissociation controlled by the redox state of Fc. Although there are quite a few reported nanoscale materials incorporating this host-guest pair, polymeric hydrogels with electrochemical activity based on this interactive pair are still rare. Taking advantage of our previous reported hybrid inclusion complex (HIC) hydrogel structure, a new Fc-HIC was designed and obtained with β-CD-modified quantum dots as the core and Fc-ended diblock co-polymer p(DMA-b-NIPAM) as the shell, to achieve an electrochemically active hydrogel at elevated temperatures. Considering the two independent cross-linking strategies in the network structure, i.e., the interchain aggregation of pNIPAM and inclusion complexation between CD and Fc on the surface of the quantum dots, the hydrogel was fully thermo-reversible and its gel-sol transition was achieved after the addition of either an oxidizing agent or a competitive guest to Fc.

Two mannose-binding lectin homologues and an MBL-associated serine protease are expressed in the gut epithelia of the urochordate species Ciona intestinalis.

PubMed

Skjoedt, Mikkel-Ole; Palarasah, Yaseelan; Rasmussen, Karina; Vitved, Lars; Salomonsen, Jan; Kliem, Anette; Hansen, Soren; Koch, Claus; Skjodt, Karsten

2010-01-01

The lectin complement pathway has important functions in vertebrate host defence and accumulating evidence of primordial complement components trace its emergence to invertebrate phyla. We introduce two putative mannose-binding lectin homologues (CioMBLs) from the urochordate species Ciona intestinalis. The CioMBLs display similarities with vertebrate MBLs and comprise a collagen-like region, alpha-helical coiled-coils and a carbohydrate recognition domain (CRD) with conserved residues involved in calcium and carbohydrate binding. Structural analysis revealed an oligomerization through interchain disulphide bridges between N-terminal cysteine residues and cysteines located between the neck region and the CRD. RT-PCR showed a tissue specific expression of CioMBL in the gut and by immunohistochemistry analysis we also demonstrated that CioMBL co-localize with an MBL-associated serine protease in the epithelia cells lining the stomach and intestine. In conclusion we present two urochordate MBLs and identify an associated serine protease, which support the concept of an evolutionary ancient origin of the lectin complement pathway.

Absence of long range order in SrDy2O4 frustrated magnet due to trapped defects from a dimensionality crossover

NASA Astrophysics Data System (ADS)

Gauthier, Nicolas; Fennell, Amy; Uldry, Anne-Christine; Delley, Bernard; Sibille, Romain; White, Jonathan; Niedermayer, Christof; Pomjakushin, Vladimir; Kenzelmann, Michel; Prevost, Bobby; Desilets-Benoit, Alexandre; Bianchi, Andrea D.; Dabkowska, Hanna A.; Nilsen, Goran; Regnault, Louis-Pierre

The simultaneous occurence of geometrical frustration and low dimensionality can lead to strongly correlated fluctuating ground states. In the SrLn2O4 compounds, the Ln magnetic ions form one-dimensional (1D) zig-zag chains that have both of these characteristics, offering a playground to study novel states of matter. In SrDy2O4, the two inequivalent Dy3+ sites are Ising-like with perpendicular easy-axes, favouring the decoupling of neighbouring zig-zag chains. No long range order is observed down to T = 60 mK in zero field but diffuse neutron scattering indicates short range correlations that are consistent with those of the 1D Ising zig-zag chain model. AC susceptibility measurements indicate a slowing down of the fluctuations at low temperatures. We attribute this behaviour to the domain walls in the zig-zag chains. Experimental evidence of a dimensionality crossover at low temperatures in SrDy2O4 suggest that the domains walls are trapped because of interchain interactions, precluding long-range order to the lowest temperatures.

[Co5(mu3-OH)2(btec)2(bpp)]n: a three-dimensional homometallic molecular metamagnet built from the mixed hydroxide/carboxylate-bridged ferrimagnetic-like chains.

PubMed

Jia, Hong-Peng; Li, Wei; Ju, Zhan-Feng; Zhang, Jie

2007-09-07

A three-dimensional homometallic complex [Co(5)(mu(3)-OH)(2)(btec)(2)(bpp)](n) is built from the mixed hydroxide/carboxylate bridged cobalt(ii) chains linked by the 1,2,4,5-benzenetetracarboxylate (btec(4-)) anion and 1,3-bis(4-pyridyl)-propane molecule (bpp). Within each chain, two mu(3)-OH-bridged metal triangles connect to each other by sharing a common vertex to give rise to a bow-tie type Co(5)(mu(3)-OH)(2) subunit, which is joined to adjacent subunits by four mu(1,1)-carboxylate bridges to form a step-like metal-oxygen backbone. The magnetic studies revealed that the coexistence of ferromagnetic and antiferrimagnetic interactions resulted in a ferrimagnetic-like behavior of the homometallic chains. Below a critical temperature (T(N) = 12.5 K), bulk antiferromagnetic ordering was observed at low field due to the weak interchain antiferromagnetic interactions. A metamagnetic transition occurred at a magnetic field of ca. 5 kOe at 2 K.

Bridging disulfides for stable and defined antibody drug conjugates.

PubMed

Badescu, George; Bryant, Penny; Bird, Matthew; Henseleit, Korinna; Swierkosz, Julia; Parekh, Vimal; Tommasi, Rita; Pawlisz, Estera; Jurlewicz, Kosma; Farys, Monika; Camper, Nicolas; Sheng, XiaoBo; Fisher, Martin; Grygorash, Ruslan; Kyle, Andrew; Abhilash, Amrita; Frigerio, Mark; Edwards, Jeff; Godwin, Antony

2014-06-18

To improve both the homogeneity and the stability of ADCs, we have developed site-specific drug-conjugating reagents that covalently rebridge reduced disulfide bonds. The new reagents comprise a drug, a linker, and a bis-reactive conjugating moiety that is capable of undergoing reaction with both sulfur atoms derived from a reduced disulfide bond in antibodies and antibody fragments. A disulfide rebridging reagent comprising monomethyl auristatin E (MMAE) was prepared and conjugated to trastuzumab (TRA). A 78% conversion of antibody to ADC with a drug to antibody ratio (DAR) of 4 was achieved with no unconjugated antibody remaining. The MMAE rebridging reagent was also conjugated to the interchain disulfide of a Fab derived from proteolytic digestion of TRA, to give a homogeneous single drug conjugated product. The resulting conjugates retained antigen-binding, were stable in serum, and demonstrated potent and antigen-selective cell killing in in vitro and in vivo cancer models. Disulfide rebridging conjugation is a general approach to prepare stable ADCs, which does not require the antibody to be recombinantly re-engineered for site-specific conjugation.

Crystal structure and magnetic properties of cyclohexylammonium trichlorocuprate(II): A quasi 1d Heisenberg S = {1}/{2} ferromagnet

NASA Astrophysics Data System (ADS)

Groenendijk, H. A.; Blöte, H. W. J.; van Duyneveldt, A. J.; Gaura, R. M.; Landee, C. P.; Willett, R. D.

1981-06-01

The crystal structure of [C 6H 11NH 3] CuCl 3, cyclohexylammonium trichlorocuprate(II) (CHAC), is orthorhombic, space group P2 12 12 1 with a = 19.441(5), b = 8.549(2) and c = 6.190(1) Å. The salt contains chains of CuCl -3 ions along the c axis. From magnetization and susceptibility measurements it is found that the compound behaves as a one-dimensional S = {1}/{2} Heisenberg ferromagnet with J1/ k = 70(2) K. Antiferromagnetic ordering with a weak ferromagnetic moment along the a axis occurs below T c = 2.18(2) K. From the metamagnetic phase diagram the interchain interactions are derived using mean field theory: z2J2/ z1J1 = 1.1 × 10 -3 and z3J3/ z1J1 = -1.0 × 10 -4. Also a small anisotropy ( J|/ J⊥ ≈ 0.01) is found in the intrachain interaction. The measurements indicate that CHAC is one of the best approximations to the 1d Heisenberg ferromagnet known to date.

Conformational Dynamics of Insulin

PubMed Central

Hua, Qing-Xin; Jia, Wenhua; Weiss, Michael A.

2011-01-01

We have exploited a prandial insulin analog to elucidate the underlying structure and dynamics of insulin as a monomer in solution. A model was provided by insulin lispro (the active component of Humalog®; Eli Lilly and Co.). Whereas NMR-based modeling recapitulated structural relationships of insulin crystals (T-state protomers), dynamic anomalies were revealed by amide-proton exchange kinetics in D2O. Surprisingly, the majority of hydrogen bonds observed in crystal structures are only transiently maintained in solution, including key T-state-specific inter-chain contacts. Long-lived hydrogen bonds (as defined by global exchange kinetics) exist only at a subset of four α-helical sites (two per chain) flanking an internal disulfide bridge (cystine A20–B19); these sites map within the proposed folding nucleus of proinsulin. The anomalous flexibility of insulin otherwise spans its active surface and may facilitate receptor binding. Because conformational fluctuations promote the degradation of pharmaceutical formulations, we envisage that “dynamic re-engineering” of insulin may enable design of ultra-stable formulations for humanitarian use in the developing world. PMID:22649374

Biosynthesis of D-alanyl-lipoteichoic acid by Lactobacillus casei: interchain transacylation of D-alanyl ester residues

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

Childs, W.C. 3d.; Taron, D.J.; Neuhaus, F.C.

Lipoteichoic acid (LTA) from Lactobacillus casei contains poly(glycerophosphate) substituted with D-alanyl ester residues. The distribution of these residues in the in vitro-synthesized polymer is uniform. Esterification of LTA with D-alanine may occur in one of two modes: (i) addition at random or (ii) addition at a defined locus in the poly(glycerophosphate) chain followed by redistribution of the ester residues. A time-dependent transacylation of these residues from D-(/sup 14/C)alanyl-lipophilic LTA to hydrophilic acceptor was observed. The hydrophilic acceptor was characterized as D-alanyl-hydrophilic LTA. This transacylation requires neither ATP nor the D-alanine incorporation system, i.e., the D-alanine activating enzyme and D-alanine:membrane acceptormore » ligase. No evidence for an enzyme-catalyzed transacylation reaction was observed. The authors propose that this process of transacylation may be responsible for the redistribution of D-alanyl residues after esterification to the poly(glycerophosphate). As a result, it is difficult to distinguish between these proposed modes of addition.« less

Multi-disciplinary coupling effects for integrated design of propulsion systems

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Singhal, S. N.

1993-01-01

Effective computational simulation procedures are described for modeling the inherent multi-disciplinary interactions which govern the accurate response of propulsion systems. Results are presented for propulsion system responses including multi-disciplinary coupling effects using coupled multi-discipline thermal, structural, and acoustic tailoring; an integrated system of multi-disciplinary simulators; coupled material behavior/fabrication process tailoring; sensitivities using a probabilistic simulator; and coupled materials, structures, fracture, and probabilistic behavior simulator. The results demonstrate that superior designs can be achieved if the analysis/tailoring methods account for the multi-disciplinary coupling effects. The coupling across disciplines can be used to develop an integrated coupled multi-discipline numerical propulsion system simulator.

Effect of hydrostatic pressure on water penetration and rotational dynamics in phospholipid-cholesterol bilayers.

PubMed Central

Bernsdorff, C; Wolf, A; Winter, R; Gratton, E

1997-01-01

The effect of high hydrostatic pressure on the lipid bilayer hydration, the mean order parameter, and rotational dynamics of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) cholesterol vesicles has been studied by time-resolved fluorescence spectroscopy up to 1500 bar. Whereas the degree of hydration in the lipid headgroup and interfacial region was assessed from fluorescence lifetime data using the probe 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH), the corresponding information in the upper acyl chain region was estimated from its effect on the fluorescence lifetime of and 3-(diphenylhexatrienyl)propyl-trimethylammonium (TMAP-DPH). The lifetime data indicate a greater level of interfacial hydration for DPPC bilayers than for POPC bilayers, but there is no marked difference in interchain hydration of the two bilayer systems. The addition of cholesterol at levels from 30 to 50 mol% to DPPC has a greater effect on the increase of hydrophobicity in the interfacial region of the bilayer than the application of hydrostatic pressure of several hundred to 1000 bar. Although the same trend is observed in the corresponding system, POPC/30 mol% cholesterol, the observed effects are markedly less pronounced. Whereas the rotational correlation times of the fluorophores decrease in passing the pressure-induced liquid-crystalline to gel phase transition of DPPC, the wobbling diffusion coefficient remains essentially unchanged. The wobbling diffusion constant of the two fluorophores changes markedly upon incorporation of 30 mol% cholesterol, and increases at higher pressures, also in the case of POPC/30 mol% cholesterol. The observed effects are discussed in terms of changes in the rotational characteristics of the fluorophores and the phase-state of the lipid mixture. The results demonstrate the ability of cholesterol to adjust the structural and dynamic properties of membranes composed of different phospholipid components, and to efficiently regulate the motional freedom and hydrophobicity of membranes, so that they can withstand even drastic changes in environmental conditions, such as high external hydrostatic pressure. PMID:9138572

Threshold and flavor effects in the renormalization group equations of the MSSM: Dimensionless couplings

NASA Astrophysics Data System (ADS)

Box, Andrew D.; Tata, Xerxes

2008-03-01

In a theory with broken supersymmetry, gaugino couplings renormalize differently from gauge couplings, as do higgsino couplings from Higgs boson couplings. As a result, we expect the gauge (Higgs boson) couplings and the corresponding gaugino (higgsino) couplings to evolve to different values under renormalization group evolution. We reexamine the renormalization group equations (RGEs) for these couplings in the minimal supersymmetric standard model (MSSM). To include threshold effects, we calculate the β functions using a sequence of (nonsupersymmetric) effective theories with heavy particles decoupled at the scale of their mass. We find that the difference between the SM couplings and their SUSY cousins that is ignored in the literature may be larger than two-loop effects which are included, and further that renormalization group evolution induces a nontrivial flavor structure in gaugino interactions. We present here the coupled set of RGEs for these dimensionless gauge and Yukawa-type couplings. The RGEs for the dimensionful soft-supersymmetry-breaking parameters of the MSSM will be presented in a companion paper.

Structural study of the effects of mutations in proteins to identify the molecular basis of the loss of local structural fluidity leading to the onset of autoimmune diseases

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

Ali, Ananya; Ghosh, Semanti; Bagchi, Angshuman

Protein-Protein Interactions (PPIs) are crucial in most of the biological processes and PPI dysfunctions are known to be associated with the onsets of various diseases. One of such diseases is the auto-immune disease. Auto-immune diseases are one among the less studied group of diseases with very high mortality rates. Thus, we tried to correlate the appearances of mutations with their probable biochemical basis of the molecular mechanisms leading to the onset of the disease phenotypes. We compared the effects of the Single Amino Acid Variants (SAVs) in the wild type and mutated proteins to identify any structural deformities that mightmore » lead to altered PPIs leading ultimately to disease onset. For this we used Relative Solvent Accessibility (RSA) as a spatial parameter to compare the structural perturbation in mutated and wild type proteins. We observed that the mutations were capable to increase intra-chain PPIs whereas inter-chain PPIs would remain mostly unaltered. This might lead to more intra-molecular friction causing a deleterious alteration of protein's normal function. A Lyapunov exponent analysis, using the altered RSA values due to polymorphic and disease causing mutations, revealed polymorphic mutations have a positive mean value for the Lyapunov exponent while disease causing mutations have a negative mean value. Thus, local spatial stochasticity has been lost due to disease causing mutations, indicating a loss of structural fluidity. The amino acid conversion plot also showed a clear tendency of altered surface patch residue conversion propensity than polymorphic conversions. So far, this is the first report that compares the effects of different kinds of mutations (disease and non-disease causing polymorphic mutations) in the onset of autoimmune diseases. - Highlights: • Protein-Protein Interaction. • Changes in Relative Solvent Accessibility (RSA). • Amino acid conversion matrix. • Polymorphic mutations. • Disease causing mutations.« less

Understanding Melt-Memory of Commercial Polyolefins

NASA Astrophysics Data System (ADS)

Alamo, Rufina

Self-nucleation (SN) or controlling self-generated seeds in a polymer melt is an avenue to increase the rate of solidification of semicrystalline polymers of commercial relevance. Self-nuclei are remains in the melt of the segmental self-assembly to form polymer crystallites providing a path to enhance primary crystal nucleation. SN has been extensively studied in homopolymers such as iPP. Recently, a strong memory effect of crystallization has been observed in melts of random ethylene copolymers well above the equilibrium melting temperature. The melt memory is associated with clusters or seeds that remain in the melt from the copolymer's sequence length partitioning. Cooling from progressively lower self-seeded melt temperatures, ethylene copolymers with a broad inter-chain comonomer composition (1 - 15 mol%) display first the expected accelerated crystallization, followed by a decrease in the rate in a range of melt temperatures where narrow copolymers show a continuous acceleration of the rate. This unusual inversion of the crystallization rate was postulated to arise from the onset of liquid-liquid phase separation (LLPS) between comonomer-rich and comonomer-poor components of the broad copolymer. The UCST type phase diagram of these commercial copolymers has been documented via SANS using a blend of components, some deuterated, to reproduce the broad distribution. Furthermore, the components that contribute to LLPS have been identified by the crystallization behavior of molar mass fractions. The influence of long chain branching on the topology of copolymer melts has been analyzed using model 3-arm stars hydrogenated polybutadienes. The effect of melt viscosity on strength of melt memory is also evident when SN data of random ethylene copolymers are compared with those of propylene-ethylene copolymers. The strong dependence of melt viscosity on melt memory, and a critical threshold crystallinity level to observe the effect of melt memory on crystallization rate, support the kinetic nature of the SN phenomenon. Support from NSF, DMR-1105129 and DMR-1607786 is gratefully acknowledged.

The Effects of Three Methods of Observation on Couples in Interactional Research.

ERIC Educational Resources Information Center

Carpenter, Linda J.; Merkel, William T.

1988-01-01

Assessed the effects of three different methods of observation of couples (one-way mirror, audio recording, and video recording) on 30 volunteer, nonclinical married couples. Results suggest that types of observation do not produce significantly different effects on nonclinical couples. (Author/ABL)

Charge Mobility Enhancement for Conjugated DPP-Selenophene Polymer by Simply Replacing One Bulky Branching Alkyl Chain with Linear One at Each DPP Unit

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

Wang, Zhijie; Liu, Zitong; Ning, Lu

Here, we demonstrate a simple, but efficient, approach for improving the semiconducting performances of DPP-based conjugated D-A polymers. This approach involves the replacement of one bulky branching alkyl chain with the linear one at each DPP unit in regular polymer PDPPSe-10 and PDPPSe-12. The UV–vis absorption, Raman spectra, PDS data, and theoretical calculations support that the replacement of bulky branching chains with linear ones can weaken the steric hindrance, and accordingly conjugated backbones become more planar and rigid. GIWAXS data show that the incorporation of linear alkyl chains as in PDPPSe-10 and PDPPSe-12 is beneficial for side-chain interdigitation and interchainmore » dense packing, leading to improvement of interchain packing order and thin film crystallinity by comparing with PDPPSe, which contains branching alkyl chains. On the basis of field-effect transistor (FET) studies, charge mobilities of PDPPSe-10 and PDPPSe-12 are remarkably enhanced. Hole mobilities of PDPPSe-10 and PDPPSe-12 in air are boosted to 8.1 and 9.4 cm 2 V –1 s –1, which are about 6 and 7 times, respectively, than that of PDPPSe (1.35 cm 2 V –1 s –1). Furthermore, both PDPPSe-10 and PDPPSe-12 behave as ambipolar semiconductors under a nitrogen atmosphere with increased hole/electron mobilities up to 6.5/0.48 cm 2 V –1 s –1 and 7.9/0.79 cm 2 V –1 s –1, respectively.« less

Investigation of the effect of erythrosine B on amyloid beta peptide using molecular modeling.

PubMed

Lee, Juho; Kwon, Inchan; Jang, Seung Soon; Cho, Art E

2016-04-01

Neurotoxic plaques composed of 39 to 42 residue-long amyloid beta peptides (Aβs) are copiously present in the brains of patients with Alzheimer's disease (AD). Erythrosine B (ER), a xanthene food dye, inhibits the formation of Aβ fibrils and Aβ-associated cytotoxicity in vitro. Here, in an attempt to elucidate the inhibition mechanism, we performed molecular dynamics (MD) simulations to demonstrate the conformational change of Aβ40 induced by ER molecules in atomistic detail. During the simulation, the ER bound to the surfaces of both N-terminus and C-terminus regions of Aβ40. Our result shows that ER interacts with the aromatic side chains at the N-terminus region resulting in destabilization of the inter-chain stacking of Aβ40. Moreover, the stablility of the helical structures at the residues from 13 to 16 suggests that ER disturbs conformational transition of Aβ40. At the C-terminus region, the bound ER blocks water molecules and stabilizes the α-helical structure. Regardless of the number of ER molecules used, the interruption of the formation of the salt-bridge between aspartic acid 23 and lysine 28 occurred. To further validate our analysis, binding free energies of ER at each binding site were evaluated. The finding of stronger binding energy at the N-terminus region supports an inhibition mechanism induced by stacking interaction between ER and phenylalanine. These findings could aid present and future treatment studies for AD by clarifying the inhibition mechanism of ER on the conformational transition of Aβ40 at the molecular level.

Charge Mobility Enhancement for Conjugated DPP-Selenophene Polymer by Simply Replacing One Bulky Branching Alkyl Chain with Linear One at Each DPP Unit

DOE PAGES

Wang, Zhijie; Liu, Zitong; Ning, Lu; ...

2018-04-17

Here, we demonstrate a simple, but efficient, approach for improving the semiconducting performances of DPP-based conjugated D-A polymers. This approach involves the replacement of one bulky branching alkyl chain with the linear one at each DPP unit in regular polymer PDPPSe-10 and PDPPSe-12. The UV–vis absorption, Raman spectra, PDS data, and theoretical calculations support that the replacement of bulky branching chains with linear ones can weaken the steric hindrance, and accordingly conjugated backbones become more planar and rigid. GIWAXS data show that the incorporation of linear alkyl chains as in PDPPSe-10 and PDPPSe-12 is beneficial for side-chain interdigitation and interchainmore » dense packing, leading to improvement of interchain packing order and thin film crystallinity by comparing with PDPPSe, which contains branching alkyl chains. On the basis of field-effect transistor (FET) studies, charge mobilities of PDPPSe-10 and PDPPSe-12 are remarkably enhanced. Hole mobilities of PDPPSe-10 and PDPPSe-12 in air are boosted to 8.1 and 9.4 cm 2 V –1 s –1, which are about 6 and 7 times, respectively, than that of PDPPSe (1.35 cm 2 V –1 s –1). Furthermore, both PDPPSe-10 and PDPPSe-12 behave as ambipolar semiconductors under a nitrogen atmosphere with increased hole/electron mobilities up to 6.5/0.48 cm 2 V –1 s –1 and 7.9/0.79 cm 2 V –1 s –1, respectively.« less

Controllable nonlinearity in a dual-coupling optomechanical system under a weak-coupling regime

NASA Astrophysics Data System (ADS)

Zhu, Gui-Lei; Lü, Xin-You; Wan, Liang-Liang; Yin, Tai-Shuang; Bin, Qian; Wu, Ying

2018-03-01

Strong quantum nonlinearity gives rise to many interesting quantum effects and has wide applications in quantum physics. Here we investigate the quantum nonlinear effect of an optomechanical system (OMS) consisting of both linear and quadratic coupling. Interestingly, a controllable optomechanical nonlinearity is obtained by applying a driving laser into the cavity. This controllable optomechanical nonlinearity can be enhanced into a strong coupling regime, even if the system is initially in the weak-coupling regime. Moreover, the system dissipation can be suppressed effectively, which allows the appearance of phonon sideband and photon blockade effects in the weak-coupling regime. This work may inspire the exploration of a dual-coupling optomechanical system as well as its applications in modern quantum science.

Research on the Treatment of Couple Distress

ERIC Educational Resources Information Center

Lebow, Jay L.; Chambers, Anthony L.; Christensen, Andrew; Johnson, Susan M.

2012-01-01

This article reviews the research on couple therapy over the last decade. The research shows that couple therapy positively impacts 70% of couples receiving treatment. The effectiveness rates of couple therapy are comparable to the effectiveness rates of individual therapies and vastly superior to control groups not receiving treatment. The…

Multi-disciplinary coupling for integrated design of propulsion systems

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Singhal, S. N.

1993-01-01

Effective computational simulation procedures are described for modeling the inherent multi-disciplinary interactions for determining the true response of propulsion systems. Results are presented for propulsion system responses including multi-discipline coupling effects via (1) coupled multi-discipline tailoring, (2) an integrated system of multidisciplinary simulators, (3) coupled material-behavior/fabrication-process tailoring, (4) sensitivities using a probabilistic simulator, and (5) coupled materials/structures/fracture/probabilistic behavior simulator. The results show that the best designs can be determined if the analysis/tailoring methods account for the multi-disciplinary coupling effects. The coupling across disciplines can be used to develop an integrated interactive multi-discipline numerical propulsion system simulator.

Communication and Contraceptive Practices in Adolescent Couples.

ERIC Educational Resources Information Center

Polit-O'Hara, Denise; Kahn, Janet R.

1985-01-01

Presents a descriptive analysis of couple communication among stable, sexually active adolescent couples (N=83) and the effect of communication on actual contraceptive practices. Results showed couples with good communication were more likely to practice effective contraception. (BH)

Global Effects of SuperParameterization on Hydro-Thermal Land-Atmosphere Coupling on Multiple Timescales and an Amplification of the Bowen Ratio

NASA Astrophysics Data System (ADS)

Qin, H.; Pritchard, M. S.; Kooperman, G. J.; Parishani, H.

2017-12-01

Conventional General Circulation Models (GCMs) in the Global Land-Atmosphere Coupling Experiment (GLACE) tend to produce overly strong Land-Atmosphere coupling (L-A coupling) strength. We investigate the effects of cloud SuperParameterization (SP) on L-A coupling on timescales longer than the diurnal where it has been previously shown to have a strong effect. Using the Community Atmosphere Model v3.5 (CAM3.5) and its SuperParameterized counterpart SPCAM3.5, we conducted experiments following the GLACE and Atmospheric Model Intercomparison Project (AMIP) protocols. On synoptic-to-subseasonal timescales, SP significantly mutes hydrologic L-A coupling on a global scale, through the atmospheric segment. But on longer seasonal timescales, SP does not exhibit detectable effects on hydrologic L-A coupling. Two regional effects of SP on thermal L-A coupling are also discovered and explored. Over the Arabian Peninsula, SP strikingly reduces thermal L-A coupling due to a control by mean regional rainfall reduction. Over the Southwestern US and Northern Mexico, however, SP remarkably enhances the thermal L-A coupling independent of rainfall or soil moisture. We argue that the cause may be a previously unrecognized effect of SP to amplify the simulated Bowen ratio. Not only does this help reconcile a puzzling local enhancement of thermal L-A coupling over the Southwestern US, but it is also demonstrated to be a robust, global effect of SP over land that is independent of model version and experiment design, and that has important consequences for climate change prediction.

Ordering and Excitations in the Field-Induced Magnetic Phase of Cs3Cr2Br9

NASA Astrophysics Data System (ADS)

Grenier, Beatrice

2006-03-01

Cs3Cr2Br9 is an interesting example of interacting spin-dimer system. As in other isotropic antiferromagnets such as Haldane or alternating chains and ladders, the ground state in zero field is a total spin singlet separated from the excited triplet by an energy gap. In a magnetic field H, a phase transition occurs at a critical field Hc1, where the gap to the lowest component of the Zeeman-split triplet closes. Above Hc1, field-induced magnetic order (FIMO) for spin components perpendicular to H is induced by inter-dimer or inter-chain couplings. The FIMO transition may be considered as a Bose-Einstein Condensation. Cs3Cr2Br9 differs from other dimer systems currently studied (e.g. PHCC, TlCuCl3) in two main ways: each Cr^3+ ion of the dimer has spin 3/2 rather than 1/2 for Cu-based systems and the arrangement of the dimers is hexagonal. This gives rise to anisotropy and frustration in a 3D lattice, respectively. The possibility of studying the magnetic ordering and the spin dynamics in a FIMO with sufficient detail to bring out features of frustration and anisotropy motivated the present neutron scattering study in Cs3Cr2Br9*. Two field orientations have been exploited, perpendicular and parallel to the easy axis c (direction of the dimers). First, I present the diffraction study: the FIMO displays large hysteresis incommensurability, showing the importance of frustration. The impact of anisotropy is seen in the magnetic structure, whose nature strongly depends on the field direction. Second, I focus on spin dynamics: it quantifies the presence of anisotropy and shows its crucial role on the energy gap at Hc1, which is measurably open or not, depending on whether H is perpendicular or parallel to c. Third, an explanation is proposed for the large value of the gap at higher field: it involves the mixing of higher order states (extended-FIMO), reflected by the absence of magnetization plateaus. Comparison with the sister Cs3Cr2Cl9 compound provides a test of this hypothesis. *B. Grenier et al., Phys. Rev. Lett. 92, 177202 (2004)

Effects of relationship education on couple communication and satisfaction: A randomized controlled trial with low-income couples.

PubMed

Williamson, Hannah C; Altman, Noemi; Hsueh, JoAnn; Bradbury, Thomas N

2016-02-01

Although preventive educational interventions for couples have been examined in more than 100 experimental studies, the value of this work is limited by reliance on economically advantaged populations and by an absence of data on proposed mediators and moderators. Data from the Supporting Healthy Marriage Project-a randomized, controlled trial of relationship education for couples living with low incomes-were therefore analyzed to test whether intervention effects on relationship satisfaction would be mediated by observational assessments of relationship communication and whether any such effects would be moderated by couples' pretreatment risk. Within the larger sample of Supporting Healthy Marriage Project couples randomized to a relationship education or no-treatment control condition, the present analyses focus on the 1,034 couples who provided (a) data on sociodemographic risk at baseline, (b) observational data on couple communication 12 months after randomization, and (c) reports of relationship satisfaction 30 months after randomization. Intervention couples reported higher satisfaction at 30 months than control couples, regardless of their level of pretreatment risk. Among higher risk couples, the intervention improved observed communication as well. Contrary to prediction, treatment effects on satisfaction were not mediated by improvements in communication, and improvements in communication did not translate into greater satisfaction. Relationship education programs produce small improvements in relationship satisfaction and communication, particularly for couples at elevated sociodemographic risk. The absence of behavioral effects on satisfaction indicates, however, that the mechanisms by which couples may benefit from relationship education are not yet well understood. (c) 2016 APA, all rights reserved).

Interactions between sodium dodecyl sulphate and non-ionic cellulose derivatives studied by size exclusion chromatography with online multi-angle light scattering and refractometric detection.

PubMed

Wittgren, Bengt; Stefansson, Morgan; Porsch, Bedrich

2005-08-05

The novel approach described allows to characterise the surfactant-polymer interaction under several sodium dodecyl sulphate (SDS) concentrations (0-20 mM) using size exclusion chromatography (SEC) with online multi-angle light scattering (MALS) and refractometric (RI) detection. Three different cellulose derivatives, hydroxypropyl cellulose (HPC), hydroxypropyl methyl cellulose (HPMC) and hydroxyethyl cellulose (HEC), have been studied in solution containing 10 mM NaCl and various concentrations of sodium dodecyl sulphate. It is shown that this approach is well suited for successful application of both Hummel-Dreyer and multi-component light scattering principles and yields reliable molecular masses of both the polymer complex and the polymer itself within the complex, the amount of surfactant bound into the complex as well as appropriate values of the refractive index increment (dn/dc)micro, of both the complex and the polymer in question. The more hydrophobic derivatives HPC and HPMC adsorbed significantly more SDS than HEC. The inter-chain interactions close to critical aggregation concentration (cac) were clearly seen for HPC and HPMC as an almost two-fold average increase in polymer molecular mass contained in the complex.

Electrostatic forces govern the binding mechanism of intrinsically disordered histone chaperones

PubMed Central

Liu, Chuanbo; Wang, Tianshu; Bai, Yawen; Wang, Jin

2017-01-01

A unified picture to understand the protein recognition and function must include the native binding complex structure ensembles and the underlying binding mechanisms involved in specific biological processes. However, quantifications of both binding complex structures and dynamical mechanisms are still challenging for IDP. In this study, we have investigated the underlying molecular mechanism of the chaperone Chz1 and histone H2A.Z-H2B association by equilibrium and kinetic stopped-flow fluorescence spectroscopy. The dependence of free energy and kinetic rate constant on electrolyte mean activity coefficient and urea concentration are uncovered. Our results indicate a previous unseen binding kinetic intermediate. An initial conformation selection step of Chz1 is also revealed before the formation of this intermediate state. Based on these observations, a mixed mechanism of three steps including both conformation selection and induced fit is proposed. By combination of the ion- and denaturant-induced experiments, we demonstrate that electrostatic forces play a dominant role in the recognition of bipolar charged intrinsically disordered protein Chz1 to its preferred partner H2A.Z-H2B. Both the intra-chain and inter-chain electrostatic interactions have direct impacts on the native collapsed structure and binding mechanism. PMID:28552960

A new 1D manganese(II) coordination polymer with end-to-end azide bridge and isonicotinoylhydrazone Schiff base ligand: Crystal structure, Hirshfeld surface, NBO and thermal analyses

NASA Astrophysics Data System (ADS)

Khani, S.; Montazerozohori, M.; Masoudiasl, A.; White, J. M.

2018-02-01

A new manganese (II) coordination polymer, [MnL2 (μ-1,3-N3)2]n, with co-ligands including azide anion and Schiff base based on isonicotinoylhydrazone has been synthesized and characterized. The crystal structure determination shows that the azide ligand acts as end-to-end (EE) bridging ligand and generates a one-dimensional coordination polymer. In this compound, each manganes (II) metal center is hexa-coordinated by four azide nitrogens and two pyridinic nitrogens for the formation of octahedral geometry. The analysis of crystal packing indicates that the 1D chain of [MnL2 (μ-1,3-N3)2]n, is stabilized as a 3D supramolecular network by intra- and inter-chain intermolecular interactions of X-H···Y (X = N and C, Y = O and N). Hirshfeld surface analysis and 2D fingerprint plots have been used for a more detailed investigation of intermolecular interactions. Also, natural bond orbital (NBO) analysis was performed to get information about atomic charge distributions, hybridizations and the strength of interactions. Finally, thermal analysis of compound showed its complete decomposition during three thermal steps.

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

Monney, Claude; Bisogni, Valentina; Zhou, Ke-Jin

Cuprate materials, such as those hosting high-temperature superconductivity, represent a famous class of materials where the correlations between the strongly entangled charges and spins produce complex phase diagrams. Several years ago, the Zhang-Rice singlet was proposed as a natural quasiparticle in hole-doped cuprates. The occurrence and binding energy of this quasiparticle, consisting of a pair of bound holes with antiparallel spins on the same CuO 4 plaquette, depends on the local electronic interactions, which are fundamental quantities for understanding the physics of the cuprates. Here, we employ state-of-the-art resonant inelastic x-ray scattering (RIXS) to probe the correlated physics of themore » CuO 4 plaquettes in the quasi-one-dimensional chain cuprate Li 2CuO 2. By tuning the incoming photon energy to the O K edge, we populate bound states related to the Zhang-Rice quasiparticles in the RIXS process. Both intra- and interchain Zhang-Rice singlets are observed and their occurrence is shown to depend on the nearest-neighbor spin-spin correlations, which are readily probed in this experiment. Finally, we also extract the binding energy of the Zhang-Rice singlet and identify the Zhang-Rice triplet excitation in the RIXS spectra.« less

Crystal structure of poly[[μ-4-(hy-droxy-meth-yl)pyridine-κ(2) N:O][4-(hy-droxy-meth-yl)pyridine-κN](μ-thio-cyanato-κ(2) N:S)(thio-cyanato-κN)cadmium].

PubMed

Werner, Julia; Jess, Inke; Näther, Christian

2015-06-01

The crystal structure of the title compound, [Cd(NCS)2(C6H7NO)2] n is made up of Cd(2+) cations that are coordinated by three thio-cyanate ligands and three 4-(hy-droxy-meth-yl)pyridine ligands within distorted N4OS octa-hedra. The asymmetric unit consists of one Cd(2+) cation, two thio-cyanate anions and two 4-(hy-droxy-meth-yl)pyridine ligands in general positions. Two Cd(2+) cations are linked by two μ-1,3 N- and S-bonding thio-ycanate anions into dimers which are further linked into branched chains along [100] by two μ-1,6 N- and O-bonding 4-(hy-droxy-meth-yl)pyridine ligands. One additional N-bonded 4-(hy-droxy-meth-yl)pyridine ligand and one additional N-bonded thio-cyanate anion are only terminally bonded to the metal cation. Inter-chain O-H⋯S hydrogen bonds between the hy-droxy H atoms and one of the thio-cyanate S atoms connect the chains into a three-dimensional network.

Rapid assessment of oxidation via middle-down LCMS correlates with methionine side-chain solvent-accessible surface area for 121 clinical stage monoclonal antibodies.

PubMed

Yang, Rong; Jain, Tushar; Lynaugh, Heather; Nobrega, R Paul; Lu, Xiaojun; Boland, Todd; Burnina, Irina; Sun, Tingwan; Caffry, Isabelle; Brown, Michael; Zhi, Xiaoyong; Lilov, Asparouh; Xu, Yingda

Susceptibility of methionine to oxidation is an important concern for chemical stability during the development of a monoclonal antibody (mAb) therapeutic. To minimize downstream risks, leading candidates are usually screened under forced oxidation conditions to identify oxidation-labile molecules. Here we report results of forced oxidation on a large set of in-house expressed and purified mAbs with variable region sequences corresponding to 121 clinical stage mAbs. These mAb samples were treated with 0.1% H 2 O 2 for 24 hours before enzymatic cleavage below the hinge, followed by reduction of inter-chain disulfide bonds for the detection of the light chain, Fab portion of heavy chain (Fd) and Fc by liquid chromatography-mass spectrometry. This high-throughput, middle-down approach allows detection of oxidation site(s) at the resolution of 3 distinct segments. The experimental oxidation data correlates well with theoretical predictions based on the solvent-accessible surface area of the methionine side-chains within these segments. These results validate the use of upstream computational modeling to predict mAb oxidation susceptibility at the sequence level.

An Experimental Study of the Ising Chain Statistics under the Magnetic Field

NASA Astrophysics Data System (ADS)

Takeda, Kazuyoshi; Wada, Masaru

1981-11-01

The first experimental study of the statistics of a quasi-one-dimensional Ising system under the magnetic field Hα, described by the Hamiltonian \\includegraphics{dummy.eps} has been performed, where J1 and J2 are the intra- and the inter-chain exchange constants, respectively. A single crystal of the compound (CH3)3NHCoCl3\\cdot2H2O has been used as a model sample of the ferromagnetic system with J1/kB{=}14.2 K and J2/kB{=}0.20 K. It has been revealed that the experimental values of the magnetic heat capacity under the field Hα>2J2/gzμB (≈0.8 kOe) applied along the spin preferential axis are excellently reproduced by the values calculated for the isolated Ising chain under the longitudinal field (α{=}z; gz{=}6.54). For the temperature higher than 7 K (≈J1/2kB), the experimental values of the magnetic heat capacity under the field along the spin hard axis have also agreed with the theoretical values for the isolated Ising chain under the transverse field (α{=}y; gy{=}3.90).

In depth analysis of the quenching of three fluorene-phenylene-based cationic conjugated polyelectrolytes by DNA and DNA bases.

PubMed

Davies, Matthew L; Douglas, Peter; Burrows, Hugh D; Martincigh, Bice; Miguel, Maria da Graça; Scherf, Ullrich; Mallavia, Ricardo; Douglas, Alastair

2014-01-16

The interaction of three cationic poly {9,9-bis[N,N-(trimethylammonium)hexyl]fluorene-co-1,4-phenylene} polymers with average chain lengths of ∼6, 12, and 100 repeat units (PFP-NR36(I),12(Br),100(Br)) with both double and single stranded, short and long, DNA and DNA bases have been studied by steady state and time-resolved fluorescence techniques. Fluorescence of PFP-NR3 polymers is quenched with high efficiency by DNA (both double and single stranded) and DNA bases. The resulting quenching plots are sigmoidal and are not accurately described by using a Stern-Volmer quenching mechanism. Here, the quenching mechanism is well modeled in terms of an equilibrium in which a PFP-NR3/DNA aggregate complex is formed which brings polymer chains into close enough proximity to allow interchain excitation energy migration and quenching at aggregate or DNA base traps. Such an analysis gives equilibrium constants of 8.4 × 10(6) (±1.2 × 10(6)) M(-1) for short-dsDNA and 8.6 × 10(6) (±1.7 × 10(6)) M(-1) for short-ssDNA with PFP-NR36(I).

Disentangling the Role of Entanglement Density and Molecular Alignment in the Mechanical Response of Glassy Polymers

NASA Astrophysics Data System (ADS)

O'Connor, Thomas; Robbins, Mark

Glassy polymers are a ubiquitous part of modern life, but much about their mechanical properties remains poorly understood. Since chains in glassy states are hindered from exploring their conformational entropy, they can't be understood with common entropic network models. Additionally, glassy states are highly sensitive to material history and nonequilibrium distributions of chain alignment and entanglement can be produced during material processing. Understanding how these far-from equilibrium states impact mechanical properties is analytically challenging but essential to optimizing processing methods. We use molecular dynamics simulations to study the yield and strain hardening of glassy polymers as separate functions of the degree of molecular alignment and inter-chain entanglement. We vary chain alignment and entanglement with three different preparation protocols that mimic common processing conditions in and out of solution. We compare our results to common mechanical models of amorphous polymers and assess their applicability to different experimental processing conditions. This research was performed within the Center for Materials in Extreme Dynamic Environments (CMEDE) under the Hopkins Extreme Materials Institute at Johns Hopkins University. Financial support was provided by Grant W911NF-12-2-0022.

Difference in the structures of alanine tri- and tetra-peptides with antiparallel β-sheet assessed by X-ray diffraction, solid-state NMR and chemical shift calculations by GIPAW.

PubMed

Asakura, Tetsuo; Yazawa, Koji; Horiguchi, Kumiko; Suzuki, Furitsu; Nishiyama, Yusuke; Nishimura, Katsuyuki; Kaji, Hironori

2014-01-01

Alanine oligomers provide a key structure for silk fibers from spider and wild silkworms.We report on structural analysis of L-alanyl-L-alanyl-L-alanyl-L-alanine (Ala)4 with anti-parallel (AP) β-structures using X-ray and solid-state NMR. All of the Ala residues in the (Ala)4 are in equivalent positions, whereas for alanine trimer (Ala)3 there are two alternative locations in a unit cell as reported previously (Fawcett and Camerman, Acta Cryst., 1975, 31, 658-665). (Ala)4 with AP β-structure is more stable than AP-(Ala)3 due to formation of the stronger hydrogen bonds. The intermolecular structure of (Ala)4 is also different from polyalanine fiber structure, indicating that the interchain arrangement of AP β-structure changes with increasing alanine sequencelength. Furthermore the precise (1)H positions, which are usually inaccesible by X-ray diffraction method, are determined by high resolution (1)H solid state NMR combined with the chemical shift calculations by the gauge-including projector augmented wave method. Copyright © 2013 Wiley Periodicals, Inc.

Aggregation and Gelation of Aromatic Polyamides with Parallel and Anti-parallel Alignment of Molecular Dipole Along the Backbone

NASA Astrophysics Data System (ADS)

Zhu, Dan; Shang, Jing; Ye, Xiaodong; Shen, Jian

2016-12-01

The understanding of macromolecular structures and interactions is important but difficult, due to the facts that a macromolecules are of versatile conformations and aggregate states, which vary with environmental conditions and histories. In this work two polyamides with parallel or anti-parallel dipoles along the linear backbone, named as ABAB (parallel) and AABB (anti-parallel) have been studied. By using a combination of methods, the phase behaviors of the polymers during the aggregate and gelation, i.e., the forming or dissociation processes of nuclei and fibril, cluster of fibrils, and cluster-cluster aggregation have been revealed. Such abundant phase behaviors are dominated by the inter-chain interactions, including dispersion, polarity and hydrogen bonding, and correlatd with the solubility parameters of solvents, the temperature, and the polymer concentration. The results of X-ray diffraction and fast-mode dielectric relaxation indicate that AABB possesses more rigid conformation than ABAB, and because of that AABB aggregates are of long fibers while ABAB is of hairy fibril clusters, the gelation concentration in toluene is 1 w/v% for AABB, lower than the 3 w/v% for ABAB.

Iodination of insulin in aqueous and organic solvents

PubMed Central

Massaglia, A.; Rosa, U.; Rialdi, G.; Rossi, C. A.

1969-01-01

1. The iodination of insulin was studied under various experimental conditions in aqueous media and in some organic solvents, by measuring separately the uptake of iodine by the four tyrosyl groups and the relative amounts of monoiodotyrosine and di-iodotyrosine that are formed. In aqueous media from pH1 to pH9 the iodination occurs predominantly on the tyrosyl groups of the A chain. Some organic solvents increase the iodine uptake of the B-chain tyrosyl groups. Their efficacy in promoting iodination of Tyr-B-16 and Tyr-B-26 is in the order: ethylene glycol and propylene glycol≃methanol and ethanol>dioxan>8m-urea. 2. It is suggested that each of the four tyrosyl groups in insulin has a different environment: Tyr-A-14 is fully exposed to the solvent; Tyr-A-19 is sterically influenced by the environmental structure, possibly by the vicinity of a disulphide interchain bond; Tyr-B-16 is embedded into a non-polar area whose stability is virtually independent of the molecular conformation; Tyr-B-26 is probably in a situation similar to Tyr-B-16 with the difference that its non-polar environment depends on the preservation of the native structure. PMID:5346365

Optical-Electrical-Chemical Engineering of PEDOT:PSS by Incorporation of Hydrophobic Nafion for Efficient and Stable Perovskite Solar Cells.

PubMed

Ma, Shuang; Qiao, Wenyuan; Cheng, Tai; Zhang, Bing; Yao, Jianxi; Alsaedi, Ahmed; Hayat, Tasawar; Ding, Yong; Tan, Zhan'ao; Dai, Songyuan

2018-01-31

In PIN-type perovskite solar cells (PSCs), the hydroscopicity and acidity of the poly(3,4-ethylenedioxythiophene)-poly(styrene-sulfonate) (PEDOT:PSS) hole transport layer (HTL) have critical influences on the device stability. To eliminate these problems, Nafion, the hydrophobic perfluorosulfonic copolymer, is incorporated into PEDOT:PSS by a simple spin-coating process. For the modified film, Nafion/PSSH (poly(styrene sulfonate) acid) acts as an electron-blocking layer on the surface and the PEDOT-rich domain tends to gather into larger particles with better interchain charge transfer inside the film. Consequently, the modified PEDOT:PSS HTL shows enhanced conductivity and light transmittance as well as more favorable work function, ending up with the increased short-circuit current density (J sc ) and open-circuit voltage (V oc ) of the device. Finally, PSCs with Nafion-modified HTLs achieve the best power conversion efficiency of 16.72%, with 23.76% improvement compared with PEDOT:PSS-only devices (13.51%). Most importantly, the device stability is obviously enhanced because of the hydrophobicity and chemical and mechanical stability of the Nafion polymer that is enriched on the surface of the PEDOT:PSS film.

Structural and optical properties improvements of PVP/gelatin blends induced by neutron irradiation

NASA Astrophysics Data System (ADS)

Basha, Mohammad Ahmad-Fouad; Hassan, Mohamed Ahmed

2018-05-01

Blends of polyvinylpyrrolidone and gelatin were prepared in three different concentrations to study the modifications in their structural and optical properties induced by neutron irradiations with different neutron fluence values from 108 up to 1011 neutron/cm2. X-ray spectroscopy revealed that the irradiation has induced a recrystallization phenomenon in the studied blends and the crystallinity index increased by increasing the neutron fluence due to the breaking of the crystallites. Fourier-transform infrared spectroscopy came to confirm the existence of interactions between interchain groups and a higher compatibility for the irradiated blends. The irradiation induced defects inside the material were responsible for the change in their optical and structural properties. The creation of free radicals or ions inside the conduction bands has led to the increase in the number of carriers on localized states; this has caused the increase in optical conductivity of the irradiated blends as a result of decreasing the energy gaps by increasing the neutron fluence. Results may widen the applications of the gelatin based blends to include optoelectronic devices, organic light emitting devices, solar selective and anti-reflectance bio-coatings, optical organic glass and lenses.

Initial adhesive screening of novel polyamide-imides and their copolymers

NASA Technical Reports Server (NTRS)

Progar, Donald J.; Dezern, James F.

1988-01-01

Continued interest by the research community in thermally stable, tough, high temperature adhesives has resulted in the investigation by Langley Research Center of two linear aromatic polyamide-imide (PAI) homopolymers and two linear aromatic PAI copolymers. The homopolymers were made with either 3,3'=DABA or 4,4'-DABA and BTDA. The two polymers were prepared with a monomer ratio of 0.75 DABP:0.25 DABA:1.00 BTDA. These aromatic PAIs possess high thermal stability because of intermolecular hydrogen bonding and chain stiffness. Lap shear strength (LSS) was the main criteria used to evaluate the polymers as adhesives. LSS of bonded Ti-6Al-4V was determined at room temperature (RT), 177, 204 and 232 C. The glass transition temperature and the type of bond failure were also determined. The best LSS values of the four adhesive systems investigated were obtained with the PAI copolymer identified in the report as LARC-TPI (25 percent 3,3'-DABA); however, it did not produce LSSs nearly as high as LARC-TPI. The poor flow properties observed appear to be due to a combination of high molecular weight and the increased interchain electronic interactions associated with the amide group.

Solution Phase Exciton Diffusion Dynamics of a Charge-Transfer Copolymer PTB7 and a Homopolymer P3HT

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

Cho, Sung; Rolczynski, Brian S.; Xu, Tao

2015-06-18

Using ultrafast polarization-controlled transient absorption (TA) measurements, dynamics of the initial exciton states were investigated on the time scale of tens of femtoseconds to about 80 ps in two different types of conjugated polymers extensively used in active layers of organic photovoltaic devices. These polymers are poly(3-fluorothienothiophenebenzodithiophene) (PTB7) and poly-3-hexylthiophene (P3HT), which are charge-transfer polymers and homopolymers, respectively. In PTB7, the initial excitons with excess vibrational energy display two observable ultrafast time constants, corresponding to coherent exciton diffusion before the vibrational relaxation, and followed by incoherent exciton diffusion processes to a neighboring local state after the vibrational relaxation. In contrast,more » P3HT shows only one exciton diffusion or conformational motion time constant of 34 ps, even though its exciton decay kinetics are multiexponential. Based on the experimental results, an exciton dynamics mechanism is conceived taking into account the excitation energy and structural dependence in coherent and incoherent exciton diffusion processes, as well as other possible deactivation processes including the formation of the pseudo-charge-transfer and charge separate states, as well as interchain exciton hopping or coherent diffusion.« less

Solution Phase Exciton Diffusion Dynamics of a Charge-Transfer Copolymer PTB7 and a Homopolymer P3HT.

PubMed

Cho, Sung; Rolczynski, Brian S; Xu, Tao; Yu, Luping; Chen, Lin X

2015-06-18

Using ultrafast polarization-controlled transient absorption (TA) measurements, dynamics of the initial exciton states were investigated on the time scale of tens of femtoseconds to about 80 ps in two different types of conjugated polymers extensively used in active layers of organic photovoltaic devices. These polymers are poly(3-fluorothienothiophenebenzodithiophene) (PTB7) and poly-3-hexylthiophene (P3HT), which are charge-transfer polymers and homopolymers, respectively. In PTB7, the initial excitons with excess vibrational energy display two observable ultrafast time constants, corresponding to coherent exciton diffusion before the vibrational relaxation, and followed by incoherent exciton diffusion processes to a neighboring local state after the vibrational relaxation. In contrast, P3HT shows only one exciton diffusion or conformational motion time constant of 34 ps, even though its exciton decay kinetics are multiexponential. Based on the experimental results, an exciton dynamics mechanism is conceived taking into account the excitation energy and structural dependence in coherent and incoherent exciton diffusion processes, as well as other possible deactivation processes including the formation of the pseudo-charge-transfer and charge separate states, as well as interchain exciton hopping or coherent diffusion.

Unexpected Competition between Antiferromagnetic and Ferromagnetic States in Hf2MnRu5B2: Predicted and Realized.

PubMed

Shankhari, Pritam; Zhang, Yuemei; Stekovic, Dejan; Itkis, Mikhail E; Fokwa, Boniface P T

2017-11-06

Materials "design" is increasingly gaining importance in the solid-state materials community in general and in the field of magnetic materials in particular. Density functional theory (DFT) predicted the competition between ferromagnetic (FM) and antiferromagnetic (AFM) ground states in a ruthenium-rich Ti 3 Co 5 B 2 -type boride (Hf 2 MnRu 5 B 2 ) for the first time. Vienna ab initio simulation package (VASP) total energy calculations indicated that the FM model was marginally more stable than one of the AFM models (AFM1), indicating very weak interactions between magnetic 1D Mn chains that can be easily perturbated by external means (magnetic field or composition). The predicted phase was then synthesized by arc-melting and characterized as Hf 2 Mn 1-x Ru 5+x B 2 (x = 0.27). Vibrating-scanning magnetometry shows an AFM ground state with T N ≈ 20 K under low magnetic field (0.005 T). At moderate-to-higher fields, AFM ordering vanishes while FM ordering emerges with a Curie temperature of 115 K. These experimental outcomes confirm the weak nature of the interchain interactions, as predicted by DFT calculations.

Aeromechanical stability of helicopters with composite rotor blades in forward flight

NASA Technical Reports Server (NTRS)

Smith, Edward C.; Chopra, Inderjit

1992-01-01

The aeromechanical stability, including air resonance in hover, air resonance in forward flight, and ground resonance, of a helicopter with elastically tailored composite rotor blades is investigated. Five soft-inplane hingeless rotor configurations, featuring elastic pitch-lag, pitch-flap and extension-torsion couplings, are analyzed. Elastic couplings introduced through tailored composite blade spars can have a powerful effect on both air and ground resonance behavior. Elastic pitch-flap couplings (positive and negative) strongly affect body, rotor and dynamic inflow modes. Air resonance stability is diminished by elastic pitch-flap couplings in hover and forward flight. Negative pitch-lag elastic coupling has a stabilizing effect on the regressive lag mode in hover and forward flight. The negative pitch-lag coupling has a detrimental effect on ground resonance stability. Extension-torsion elastic coupling (blade pitch decreases due to tension) decreases regressive lag mode stability in both airborne and ground contact conditions. Increasing thrust levels has a beneficial influence on ground resonance stability for rotors with pitch-flap and extension-torsion coupling and is only marginally effective in improving stability of rotors with pitch-lag coupling.

Air and ground resonance of helicopters with elastically tailored composite rotor blades

NASA Technical Reports Server (NTRS)

Smith, Edward C.; Chopra, Inderjit

1993-01-01

The aeromechanical stability, including air resonance in hover, air resonance in forward flight, and ground resonance, of a helicopter with elastically tailored composite rotor blades is investigated. Five soft-inplane hingeless rotor configurations, featuring elastic pitch-lag, pitch-flap and extension-torsion couplings, are analyzed. Elastic couplings introduced through tailored composite blade spars can have a powerful effect on both air and ground resonance behavior. Elastic pitch-flap couplings (positive and negative) strongly affect body, rotor and dynamic inflow modes. Air resonance stability is diminished by elastic pitch-flap couplings in hover and forwrad flight. Negative pitch-lag elastic coupling has a stabilizing effect on the regressive lag mode in hover and forward flight. The negative pitch-lag coupling has a detrimental effect on ground resonance stability. Extension-torsion elastic coupling (blade pitch decreases due to tension) decreases regressive lag mode stability in both airborne and ground contact conditions. Increasing thrust levels has a beneficial influence on ground resonance stability for rotors with pitch-flap and extension-torsion coupling and is only marginally effective in improving stability of rotors with pitch-lag coupling.

Coupled tensorial forms of the second-order effective Hamiltonian for open-subshell atoms in jj-coupling

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

Jursenas, Rytis, E-mail: Rytis.Jursenas@tfai.vu.l; Merkelis, Gintaras

2011-01-15

General expressions for the second-order effective atomic Hamiltonian are derived for open-subshell atoms in jj-coupling. The expansion terms are presented as N-body (N=0,1,2,3) effective operators given in the second quantization representation in coupled tensorial form. Two alternative coupled tensorial forms for each expansion term have been developed. To reduce the number of expressions of the effective Hamiltonian, the reduced matrix elements of antisymmetric two-particle wavefunctions are involved in the consideration. The general expressions presented allow the determination of the spin-angular part of expansion terms when studying correlation effects dealing with a number of problems in atomic structure calculations.

Study on the Vehicle Dynamic Load Considering the Vehicle-Pavement Coupled Effect

NASA Astrophysics Data System (ADS)

Xu, H. L.; He, L.; An, D.

2017-11-01

The vibration of vehicle-pavement interaction system is sophisticated random vibration process and the vehicle-pavement coupled effect was not considered in the previous study. A new linear elastic model of the vehicle-pavement coupled system was established in the paper. The new model was verified with field measurement which could reflect the real vibration between vehicle and pavement. Using the new model, the study on the vehicle dynamic load considering the vehicle-pavement coupled effect showed that random forces (centralization) between vehicle and pavement were influenced largely by vehicle-pavement coupled effect. Numerical calculation indicated that the maximum of random forces in coupled model was 2.4 times than that in uncoupled model. Inquiring the reason, it was found that the main vibration frequency of the vehicle non-suspension system was similar with that of the vehicle suspension system in the coupled model and the resonance vibration lead to vehicle dynamic load increase significantly.

Experimental determination of the effective strong coupling constant

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

Alexandre Deur; Volker Burkert; Jian-Ping Chen

2007-07-01

We extract an effective strong coupling constant from low Q{sup 2} data on the Bjorken sum. Using sum rules, we establish its Q{sup 2}-behavior over the complete Q{sup 2}-range. The result is compared to effective coupling constants extracted from different processes and to calculations based on Schwinger-Dyson equations, hadron spectroscopy or lattice QCD. Although the connection between the experimentally extracted effective coupling constant and the calculations is not clear, the results agree surprisingly well.

Couple-Focused Prevention at the Transition to Parenthood, a Randomized Trial: Effects on Coparenting, Parenting, Family Violence, and Parent and Child Adjustment.

PubMed

Feinberg, Mark E; Jones, Damon E; Hostetler, Michelle L; Roettger, Michael E; Paul, Ian M; Ehrenthal, Deborah B

2016-08-01

The transition to parenthood is a stressful period for most parents as individuals and as couples, with variability in parent mental health and couple relationship functioning linked to children's long-term emotional, mental health, and academic outcomes. Few couple-focused prevention programs targeting this period have been shown to be effective. The purpose of this study was to test the short-term efficacy of a brief, universal, transition-to-parenthood intervention (Family Foundations) and report the results of this randomized trial at 10 months postpartum. This was a randomized controlled trial; 399 couples expecting their first child were randomly assigned to intervention or control conditions after pretest. Intervention couples received a manualized nine-session (five prenatal and four postnatal classes) psychoeducational program delivered in small groups. Intent-to-treat analyses indicated that intervention couples demonstrated better posttest levels than control couples on more than two thirds of measures of coparenting, parent mental health, parenting, child adjustment, and family violence. Program effects on family violence were particularly large. Of eight outcome variables that did not demonstrate main effects, seven showed moderated intervention impact; such that, intervention couples at higher levels of risk during pregnancy showed better outcomes than control couples at similar levels of risk. These findings replicate a prior smaller study of Family Foundations, indicating that the Family Foundations approach to supporting couples making the transition to parenthood can have broad impact for parents, family relationships, and children's adjustment. Program effects are consistent and benefit all families, with particularly notable effects for families at elevated prenatal risk.

Quantification of causal couplings via dynamical effects: A unifying perspective

NASA Astrophysics Data System (ADS)

Smirnov, Dmitry A.

2014-12-01

Quantitative characterization of causal couplings from time series is crucial in studies of complex systems of different origin. Various statistical tools for that exist and new ones are still being developed with a tendency to creating a single, universal, model-free quantifier of coupling strength. However, a clear and generally applicable way of interpreting such universal characteristics is lacking. This work suggests a general conceptual framework for causal coupling quantification, which is based on state space models and extends the concepts of virtual interventions and dynamical causal effects. Namely, two basic kinds of interventions (state space and parametric) and effects (orbital or transient and stationary or limit) are introduced, giving four families of coupling characteristics. The framework provides a unifying view of apparently different well-established measures and allows us to introduce new characteristics, always with a definite "intervention-effect" interpretation. It is shown that diverse characteristics cannot be reduced to any single coupling strength quantifier and their interpretation is inevitably model based. The proposed set of dynamical causal effect measures quantifies different aspects of "how the coupling manifests itself in the dynamics," reformulating the very question about the "causal coupling strength."

Surface thermochemical effects on TPS-coupled aerothermodynamics in hypersonic Martian gas flow

NASA Astrophysics Data System (ADS)

Yang, Xiaofeng; Gui, Yewei; Tang, Wei; Du, Yanxia; Liu, Lei; Xiao, Guangming; Wei, Dong

2018-06-01

This paper deals with the surface thermochemical effects on TPS-coupled aerothermodynamics in hypersonic Martian gas flow. An interface condition with finite-rate thermochemistry was established to balance the three-dimensional Navier-Stokes solver and TPS thermal response solver, and a series of coupled simulations of chemical non-equilibrium aerothermodynamics and structure heat transfer with various surface catalycities were performed for hypersonic Mars entries. The analysis of surface thermochemistry reveals that the surface chemical reactions have great contribution to aerodynamic heating, and the temperature-dependence of finite-rate catalysis highly influences the evolution of the coupling aerodynamic heating in the coupling process. For fixed free stream parameters with proper catalytic excitation energy, a "leap" phenomenon of the TPS-coupled heat flux with the coupling time appears in the initial stage of the coupling process, due to the strong thermochemical effects on the TPS surface.

MOTIVATING ACTION AND MAINTAINING CHANGE: THE TIME-VARYING ROLE OF HOMEWORK FOLLOWING A BRIEF COUPLES INTERVENTION

PubMed Central

Hawrilenko, Matt; Fleming, CJ Eubanks; Goldstein, Alana; Cordova, James V.

2015-01-01

Studies regarding the effectiveness of homework assignments in cognitive-behavioral treatments have demonstrated mixed results. This study investigated predictors of compliance with homework recommendations and the time-varying relationship of recommendation completion with treatment response in a brief couples intervention (N=108). More satisfied couples and couples with more motivation to change completed more recommendations, whereas couples with children completed fewer. The association between recommendation completion and treatment response varied with the passage of time, with the strongest effect observed six-months after the intervention, but no discernible differences at one year post-intervention. Couples that completed more recommendations experienced more rapid treatment gains, but even those couples doing substantially fewer recommendations ultimately realized equivalent treatment effects, although they progressed more slowly. Implications are discussed. PMID:26456167

Couples groups for parents of preschoolers: ten-year outcomes of a randomized trial*

PubMed Central

Cowan, Carolyn Pape; Cowan, Philip A.; Barry, Jason

2011-01-01

This paper reports the results of a 10-year follow-up of two variations of a couples group preventive intervention offered to couples in the year before their oldest child made the transition to kindergarten. 100 couples were randomly assigned to (1) a low-dose control condition, (2) a couples group meeting for 16 weeks that focused more on couple relationship issues among other family topics, or (3) a couples group meeting for 16 weeks that focused more on parenting issues among other family issues, with an identical curriculum to condition (2). Earlier papers reported that both variations of the intervention produced positive results on parent-child relationships and on the children’s adaptation to kindergarten and 1st grade, and that the groups emphasizing couple relationships also had additional positive effects on couple interaction quality. The present paper uses growth curve analyses to examine intervention effects extending from the children’s transition to kindergarten to the transition to high school – ten years after the couples groups ended. There were 6-year positive effects of the pre-kindergarten interventions on observed couple interaction and 10-year positive effects on both parents’ marital satisfaction and the children’s adaptation (hyperactivity and aggression). Discussion includes a focus on the implications of these results for family policy, clinical practice, and the need to include a couples focus in preventive interventions to strengthen family relationships and enhance children’s adaptation to school. PMID:21480703

A Wide Band Gap Polymer with a Deep Highest Occupied Molecular Orbital Level Enables 14.2% Efficiency in Polymer Solar Cells.

PubMed

Li, Sunsun; Ye, Long; Zhao, Wenchao; Yan, Hongping; Yang, Bei; Liu, Delong; Li, Wanning; Ade, Harald; Hou, Jianhui

2018-05-21

To simultaneously achieve low photon energy loss ( E loss ) and broad spectral response, the molecular design of the wide band gap (WBG) donor polymer with a deep HOMO level is of critical importance in fullerene-free polymer solar cells (PSCs). Herein, we developed a new benzodithiophene unit, i.e., DTBDT-EF, and conducted systematic investigations on a WBG DTBDT-EF-based donor polymer, namely, PDTB-EF-T. Due to the synergistic electron-withdrawing effect of the fluorine atom and ester group, PDTB-EF-T exhibits a higher oxidation potential, i.e., a deeper HOMO level (ca. -5.5 eV) than most well-known donor polymers. Hence, a high open-circuit voltage of 0.90 V was obtained when paired with a fluorinated small molecule acceptor (IT-4F), corresponding to a low E loss of 0.62 eV. Furthermore, side-chain engineering demonstrated that subtle side-chain modulation of the ester greatly influences the aggregation effects and molecular packing of polymer PDTB-EF-T. With the benefits of the stronger interchain π-π interaction, the improved ordering structure, and thus the highest hole mobility, the most symmetric charge transport and reduced recombination are achieved for the linear decyl-substituted PDTB-EF-T (P2)-based PSCs, leading to the highest short-circuit current density and fill factor (FF). Due to the high Flory-Huggins interaction parameter (χ), surface-directed phase separation occurs in the P2:IT-4F blend, which is supported by X-ray photoemission spectroscopy results and cross-sectional transmission electron microscope images. By taking advantage of the vertical phase distribution of the P2:IT-4F blend, a high power conversion efficiency (PCE) of 14.2% with an outstanding FF of 0.76 was recorded for inverted devices. These results demonstrate the great potential of the DTBDT-EF unit for future organic photovoltaic applications.

Solvent Additive-Assisted Anisotropic Assembly and Enhanced Charge Transport of π-Conjugated Polymer Thin Films.

PubMed

Jeong, Jae Won; Jo, Gyounglyul; Choi, Solip; Kim, Yoong Ahm; Yoon, Hyeonseok; Ryu, Sang-Wan; Jung, Jaehan; Chang, Mincheol

2018-05-30

Charge transport in π-conjugated polymer films involves π-π interactions within or between polymer chains. Here, we demonstrate a facile solution processing strategy that provides enhanced intra- and interchain π-π interactions of the resultant polymer films using a good solvent additive with low volatility. These increased interactions result in enhanced charge transport properties. The effect of the good solvent additive on the intra- and intermolecular interactions, morphologies, and charge transport properties of poly(3-hexylthiophene) (P3HT) films is systematically investigated. We found that the good solvent additive facilitates the self-assembly of P3HT chains into crystalline fibrillar nanostructures by extending the solvent drying time during thin-film formation. As compared to the prior approach using a nonsolvent additive with low volatility, the solvent blend system containing a good solvent additive results in enhanced charge transport in P3HT organic field-effect transistor (OFET) devices [from ca. 1.7 × 10 -2 to ca. 8.2 × 10 -2 cm 2 V -1 s -1 for dichlorobenzene (DCB) versus 4.4 × 10 -2 cm 2 V -1 s -1 for acetonitrile]. The mobility appears to be maximized over a broad spectrum of additive concentrations (1-7 vol %), indicative of a wide processing window. Detailed analysis results regarding the charge injection and transport characteristics of the OFET devices reveal that a high-boiling-point solvent additive decreases both the contact resistance ( R c ) and channel resistance ( R ch ), contributing to the mobility enhancement of the devices. Finally, the platform presented here is proven to be applicable to alternative good solvent additives with low volatility, such as chlorobenzene (CB) and trichlorobenzene (TCB). Specifically, the mobility enhancement of the resultant P3HT films increases in the order CB (bp 131 °C) < DCB (bp 180 °C) < TCB (bp 214 °C), suggesting that solvent additives with higher boiling points provide resultant films with preferable molecular ordering and morphologies for efficient charge transport.

Simulated E-Bomb Effects on Electronically Equipped Targets

DTIC Science & Technology

2009-09-01

coupling model program (CEMPAT), pursuing a feasible geometry of attack, practical antennas, best coupling approximations of ground conductivity and...procedure to determine these possible effects is to estimate the electromagnetic coupling from first principles and simulations using a coupling model ...Applications .................................... 16 B. SYSTEM OF INTEREST MODEL AS A TARGET ............................. 16 1. Shielding Methods, as

Coupling effects in 3D plasmonic structures templated by Morpho butterfly wings.

PubMed

He, Jiaqing; Shen, Qingchen; Yang, Shuai; He, Gufeng; Tao, Peng; Song, Chengyi; Wu, Jianbo; Deng, Tao; Shang, Wen

2018-01-03

This paper presents the study of the coupling effects of three dimensional (3D) plasmonic nanostructures templated by Morpho butterfly wings. Different from the random deposition of metallic nanoparticles (NPs) or conformal coating of metallic layers on butterfly wings reported previously, the 3D plasmonic nanostructures studied in this work consist of gold (Au) nanostrips quasi-periodically arranged in 3D, which allows us to investigate the plasmonic coupling effects. Through refractive index (RI) matching, the plasmonic coupling can be differentiated from the optical contribution of butterfly wings. By tuning the deposition thickness of Au from 30 to 90 nm, the plasmonic coupling effects between the 3D Au nanostrips are gradually enhanced. In particular, the near-field coupling results in two resonant modes and enhances the surface-enhanced Raman scattering (SERS) signals.

Structural and hydrodynamic properties of an intrinsically disordered region of a germ cell-specific protein on phase separation

PubMed Central

Brady, Jacob P.; Farber, Patrick J.; Sekhar, Ashok; Lin, Yi-Hsuan; Huang, Rui; Bah, Alaji; Chan, Hue Sun; Forman-Kay, Julie D.; Kay, Lewis E.

2017-01-01

Membrane encapsulation is frequently used by the cell to sequester biomolecules and compartmentalize their function. Cells also concentrate molecules into phase-separated protein or protein/nucleic acid “membraneless organelles” that regulate a host of biochemical processes. Here, we use solution NMR spectroscopy to study phase-separated droplets formed from the intrinsically disordered N-terminal 236 residues of the germ-granule protein Ddx4. We show that the protein within the concentrated phase of phase-separated Ddx4, Ddx4cond, diffuses as a particle of 600-nm hydrodynamic radius dissolved in water. However, NMR spectra reveal sharp resonances with chemical shifts showing Ddx4cond to be intrinsically disordered. Spin relaxation measurements indicate that the backbone amides of Ddx4cond have significant mobility, explaining why high-resolution spectra are observed, but motion is reduced compared with an equivalently concentrated nonphase-separating control. Observation of a network of interchain interactions, as established by NOE spectroscopy, shows the importance of Phe and Arg interactions in driving the phase separation of Ddx4, while the salt dependence of both low- and high-concentration regions of phase diagrams establishes an important role for electrostatic interactions. The diffusion of a series of small probes and the compact but disordered 4E binding protein 2 (4E-BP2) protein in Ddx4cond are explained by an excluded volume effect, similar to that found for globular protein solvents. No changes in structural propensities of 4E-BP2 dissolved in Ddx4cond are observed, while changes to DNA and RNA molecules have been reported, highlighting the diverse roles that proteinaceous solvents play in dictating the properties of dissolved solutes. PMID:28894006

Replacement of Asp-162 by Ala prevents the cooperative transition by the substrates while enhancing the effect of the allosteric activator ATP on E. coli aspartate transcarbamoylase

PubMed Central

Fetler, L.; Tauc, P.; Baker, D.P.; Macol, C.P.; Kantrowitz, E.R.; Vachette, P.

2002-01-01

The available crystal structures of Escherichia coli aspartate transcarbamoylase (ATCase) show that the conserved residue Asp-162 from the catalytic chain interacts with essentially the same residues in both the T- and R-states. To study the role of Asp-162 in the regulatory properties of the enzyme, this residue has been replaced by alanine. The mutant D162A shows a 7700-fold reduction in the maximal observed specific activity, a twofold decrease in the affinity for aspartate, a loss of homotropic cooperativity, and decreased activation by the nucleotide effector adenosine triphosphate (ATP) compared with the wild-type enzyme. Small-angle X-ray scattering (SAXS) measurements reveal that the unliganded mutant enzyme adopts the T-quaternary structure of the wild-type enzyme. Most strikingly, the bisubstrate analog N-phosphonacetyl-L-aspartate (PALA) is unable to induce the T to R quaternary structural transition, causing only a small alteration of the scattering pattern. In contrast, addition of the activator ATP in the presence of PALA causes a significant increase in the scattering amplitude, indicating a large quaternary structural change, although the mutant does not entirely convert to the wild-type R structure. Attempts at modeling this new conformation using rigid body movements of the catalytic trimers and regulatory dimers did not yield a satisfactory solution. This indicates that intra- and/or interchain rearrangements resulting from the mutation bring about domain movements not accounted for in the simple model. Therefore, Asp-162 appears to play a crucial role in the cooperative structural transition and the heterotropic regulatory properties of ATCase. PMID:11967364

Acidic pH retards the fibrillization of human Islet Amyloid Polypeptide due to electrostatic repulsion of histidines.

PubMed

Li, Yang; Xu, Weixin; Mu, Yuguang; Zhang, John Z H

2013-08-07

The human Islet Amyloid Polypeptide (hIAPP) is the major constituent of amyloid deposits in pancreatic islets of type-II diabetes. IAPP is secreted together with insulin from the acidic secretory granules at a low pH of approximately 5.5 to the extracellular environment at a neutral pH. The increased accumulation of extracellular hIAPP in diabetes indicates that changes in pH may promote amyloid formation. To gain insights and underlying mechanisms of the pH effect on hIAPP fibrillogenesis, all-atom molecular dynamics simulations in explicit solvent model were performed to study the structural properties of five hIAPP protofibrillar oligomers, under acidic and neutral pH, respectively. In consistent with experimental findings, simulation results show that acidic pH is not conducive to the structural stability of these oligomers. This provides a direct evidence for a recent experiment [L. Khemtemourian, E. Domenech, J. P. F. Doux, M. C. Koorengevel, and J. A. Killian, J. Am. Chem. Soc. 133, 15598 (2011)], which suggests that acidic pH inhibits the fibril formation of hIAPP. In addition, a complementary coarse-grained simulation shows the repulsive electrostatic interactions among charged His18 residues slow down the dimerization process of hIAPP by twofold. Besides, our all-atom simulations reveal acidic pH mainly affects the local structure around residue His18 by destroying the surrounding hydrogen-bonding network, due to the repulsive interactions between protonated interchain His18 residues at acidic pH. It is also disclosed that the local interactions nearby His18 operating between adjacent β-strands trigger the structural transition, which gives hints to the experimental findings that the rate of hIAPP fibril formation and the morphologies of the fibrillar structures are strongly pH-dependent.

Extending lead-free hybrid photovoltaic materials to new structures: thiazolium, aminothiazolium and imidazolium iodobismuthates.

PubMed

Li, Tianyue; Wang, Qifei; Nichol, Gary S; Morrison, Carole A; Han, Hongwei; Hu, Yue; Robertson, Neil

2018-05-09

We report on the synthesis, crystal structures, optoelectronic properties and solar cell device studies of three novel organic-inorganic iodobismuthates - [C3H4NS]3[Bi2I9] ([TH]3[Bi2I9]), [C3H4N2]3[Bi2I9] ([IM]3[Bi2I9]) and [C3H5N2S][BiI4] ([AT][BiI4]) as lead-free light harvesters. [TH]3[Bi2I9] and [IM]3[Bi2I9] show zero-dimensional structures, whereas a one-dimensional edge-sharing chain structure of BiI6-octahedra was observed in [AT][BiI4], with interchain short II contacts also giving rise to the possibility of three-dimensional charge transport ability. Accordingly, greater energy dispersion in the band structure of [AT][BiI4] can be observed, and less contribution from the organic moities at the conduction band minimum in [AT][BiI4] than [TH]3[Bi2I9] have been confirmed by density functional theory calculations. Moreover, bandgap values are redshifted from 2.08 eV for [TH]3[Bi2I9] and 2.00 eV for [IM]3[Bi2I9] to 1.78 eV for [AT][BiI4], determined by UV-Vis reflectance spectroscopy. Power conversion efficiency of 0.47% has been achieved by using ([AT][BiI4]) as the light absorber in a hole-conductor-free, fully printable solar cell, with relatively good reproducibility. We also note the observation of a capacitance effect for the first time in a photovoltaic device with bismuth-based solar absorber, which may be related to the mesoporous carbon counter-electrode.

Fabrication and characterization of hydrothermal cross-linked chitosan porous scaffolds for cartilage tissue engineering applications.

PubMed

Shamekhi, Mohammad Amin; Rabiee, Ahmad; Mirzadeh, Hamid; Mahdavi, Hamid; Mohebbi-Kalhori, Davod; Baghaban Eslaminejad, Mohamadreza

2017-11-01

The use of various chemical cross-linking agents for the improvement of scaffolds physical and mechanical properties is a common practical method, which is limited by cytotoxicity effects. Due to exerting contract type forces, chondrocytes are known to implement shrinkage on the tissue engineered constructs, which can be avoided by the scaffold cross-linking. In the this research, chitosan scaffolds are cross-linked with hydrothermal treatment with autoclave sterilization time of 0, 10, 20 and 30min, to avoid the application of the traditional chemical toxic materials. The optimization studies with gel content and crosslink density measurements indicate that for 20min sterilization time, the gel content approaches to ~80%. The scaffolds are fully characterized by the conventional techniques such as SEM, porosity and permeability, XRD, compression, thermal analysis and dynamic mechanical thermal analysis (DMTA). FT-IR studies shows that autoclave inter-chain cross-linking reduces the amine group absorption at 1560cm -1 and increase the absorption of N-acetylated groups at 1629cm -1 . It is anticipated, that this observation evidenced by chitosan scaffold browning upon autoclave cross-linking is an indication of the familiar maillard reaction between amine moieties and carbonyl groups. The biodegradation rate analysis shows that chitosan scaffolds with lower concentrations, possess suitable degradation rate for cartilage tissue engineering applications. In addition, cytotoxicity analysis shows that fabricated scaffolds are biocompatible. The human articular chondrocytes seeding into 3D cross-linked scaffolds shows a higher viability and proliferation in comparison with the uncross-linked samples and 2D controls. Investigation of cell morphology on the scaffolds by SEM, shows a more spherical morphology of chondrocytes on the cross-linked scaffolds for 21days of in vitro culture. Copyright © 2017. Published by Elsevier B.V.

Effects of pH on the association between the inhibitor cystatin and the proteinase chymopapain.

PubMed

Reyes-Espinosa, Francisco; Arroyo-Reyna, Alfonso; Garcia-Gutierrez, Ponciano; Serratos, Iris N; Zubillaga, Rafael A

2014-01-01

Cysteine proteinases are involved in many aspects of physiological regulation. In humans, some cathepsins have shown another function in addition to their role as lysosomal proteases in intracellular protein degradation; they have been implicated in the pathogenesis of several heart and blood vessel diseases and in cancer development. In this work, we present a fluorometric and computational study of the binding of one representative plant cysteine proteinase, chymopapain, to one of the most studied inhibitors of these proteinases: chicken cystatin. The binding equilibrium constant, Kb, was determined in the pH range between 3.5 and 10.0, revealing a maximum in the affinity at pH 9.0. We constructed an atomic model for the chymopapain-cystatin dimer by docking the individual 3D protein structures; subsequently, the model was refined using a 100 ns NPT molecular dynamics simulation in explicit water. Upon scrutiny of this model, we identified 14 ionizing residues at the interface of the complex using a cutoff distance of 5.0 Å. Using the pKa values predicted with PROPKA and a modified proton-linkage model, we performed a regression analysis on our data to obtain the composite pKavalues for three isoacidic residues. We also calculated the electrostatic component of the binding energy (ΔGb,elec) at different pH values using an implicit solvent model and APBS software. The pH profile of this calculated energy compares well with the experimentally obtained binding energy, ΔGb. We propose that the residues that form an interchain ionic pair, Lys139A from chymopapain and Glu19B from cystatin, as well as Tyr61A and Tyr67A from chymopapain are the main residues responsible for the observed pH dependence in the chymopapain- cystatin affinity.

The effect of tensile stress on the conformational free energy landscape of disulfide bonds.

PubMed

Anjukandi, Padmesh; Dopieralski, Przemyslaw; Ribas-Arino, Jordi; Marx, Dominik

2014-01-01

Disulfide bridges are no longer considered to merely stabilize protein structure, but are increasingly recognized to play a functional role in many regulatory biomolecular processes. Recent studies have uncovered that the redox activity of native disulfides depends on their C-C-S-S dihedrals, χ2 and χ'2. Moreover, the interplay of chemical reactivity and mechanical stress of disulfide switches has been recently elucidated using force-clamp spectroscopy and computer simulation. The χ2 and χ'2 angles have been found to change from conformations that are open to nucleophilic attack to sterically hindered, so-called closed states upon exerting tensile stress. In view of the growing evidence of the importance of C-C-S-S dihedrals in tuning the reactivity of disulfides, here we present a systematic study of the conformational diversity of disulfides as a function of tensile stress. With the help of force-clamp metadynamics simulations, we show that tensile stress brings about a large stabilization of the closed conformers, thereby giving rise to drastic changes in the conformational free energy landscape of disulfides. Statistical analysis shows that native TDi, DO and interchain Ig protein disulfides prefer open conformations, whereas the intrachain disulfide bridges in Ig proteins favor closed conformations. Correlating mechanical stress with the distance between the two a-carbons of the disulfide moiety reveals that the strain of intrachain Ig protein disulfides corresponds to a mechanical activation of about 100 pN. Such mechanical activation leads to a severalfold increase of the rate of the elementary redox S(N)2 reaction step. All these findings constitute a step forward towards achieving a full understanding of functional disulfides.

Cognitive-Behavioral Couple Therapies: Review of the Evidence for the Treatment of Relationship Distress, Psychopathology, and Chronic Health Conditions.

PubMed

Fischer, Melanie S; Baucom, Donald H; Cohen, Matthew J

2016-09-01

Cognitive-behavioral couple therapy (CBCT) is an approach to assisting couples that has strong empirical support for alleviating relationship distress. This paper provides a review of the empirical status of CBCT along with behavioral couple therapy (BCT), as well as the evidence for recent applications of CBCT principles to couple-based interventions for individual psychopathology and medical conditions. Several meta-analyses and major reviews have confirmed the efficacy of BCT and CBCT across trials in the United States, Europe, and Australia, and there is little evidence to support differential effectiveness of various forms of couple therapy derived from behavioral principles. A much smaller number of effectiveness studies have shown that successful implementation in community settings is possible, although effect sizes tend to be somewhat lower than those evidenced in randomized controlled trials. Adapted for individual problems, cognitive-behavioral couple-based interventions appear to be at least as effective as individual cognitive behavioral therapy (CBT) across a variety of psychological disorders, and often more effective, especially when partners are substantially involved in treatment. In addition, couple-based interventions tend to have the unique added benefit of improving relationship functioning. Findings on couple-based interventions for medical conditions are more varied and more complex to interpret given the greater range of target outcomes (psychological, relational, and medical variables). © 2016 Family Process Institute.

A Review of the Research in Emotionally Focused Therapy for Couples.

PubMed

Wiebe, Stephanie A; Johnson, Susan M

2016-09-01

Emotionally Focused Therapy for Couples (EFT) is a brief evidence-based couple therapy based in attachment theory. Since the development of EFT, efficacy and effectiveness research has accumulated to address a range of couple concerns. EFT meets or exceeds the guidelines for classification as an evidence-based couple therapy outlined for couple and family research. Furthermore, EFT researchers have examined the process of change and predictors of outcome in EFT. Future research in EFT will continue to examine the process of change in EFT and test the efficacy and effectiveness of EFT in new applications and for couples of diverse backgrounds and concerns. © 2016 Family Process Institute.

A Meta-Analytic Study of Couple Interventions during the Transition to Parenthood

ERIC Educational Resources Information Center

Pinquart, Martin; Teubert, Daniela

2010-01-01

The present meta-analysis integrates results of 21 controlled couple-focused interventions with expectant and new parents. The interventions had, on average, small effects on couple communication (d = 0.28 standard deviation units) and psychological well-being (d = 0.21), as well as very small effects on couple adjustment (d = 0.09). Stronger…

Rotational excitation of symmetric top molecules by collisions with atoms: Close coupling, coupled states, and effective potential calculations for NH3-He

NASA Technical Reports Server (NTRS)

Green, S.

1976-01-01

The formalism for describing rotational excitation in collisions between symmetric top rigid rotors and spherical atoms is presented both within the accurate quantum close coupling framework and also the coupled states approximation of McGuire and Kouri and the effective potential approximation of Rabitz. Calculations are reported for thermal energy NH3-He collisions, treating NH3 as a rigid rotor and employing a uniform electron gas (Gordon-Kim) approximation for the intermolecular potential. Coupled states are found to be in nearly quantitative agreement with close coupling results while the effective potential method is found to be at least qualitatively correct. Modifications necessary to treat the inversion motion in NH3 are discussed.

Dual-earner couples' weekend recovery support, state of recovery, and work engagement: Work-linked relationship as a moderator.

PubMed

Park, YoungAh; Haun, Verena C

2017-10-01

Despite growing recovery research, little is known about couple-dyadic processes of recovery from work. Given that dual-earner couples experience most of their recovery opportunities during nonwork times when they are together, partners in a couple relationship may substantially affect recovery and work engagement. In this study, we propose a couple-dyadic model in which weekend partner recovery support (reported by the recipient partner) is positively related to the recipient partner's state of recovery after the weekend which, in turn, increases the recipient's work engagement the following week (actor-actor mediation effect). We also test the effect of one's state of recovery on the partner's subsequent work engagement (partner effect). Additionally, work-linked relationship status is tested as a moderator of the partner effect. Actor-partner interdependence mediation modeling is used to analyze the data from 167 dual-earner couples who answered surveys on 4 measurement occasions. The results support the indirect effect of partner recovery support on work engagement through the postweekend state of recovery. Multigroup analysis results reveal that the partner effect of state of recovery on work engagement is significant for work-linked couples only and is absent for non-work-linked couples. Theoretical and practical implications, limitations, and future research directions are discussed. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Health behaviour change interventions for couples: A systematic review.

PubMed

Arden-Close, Emily; McGrath, Nuala

2017-05-01

Partners are a significant influence on individuals' health, and concordance in health behaviours increases over time in couples. Several theories suggest that couple-focused interventions for health behaviour change may therefore be more effective than individual interventions. A systematic review of health behaviour change interventions for couples was conducted. Systematic search methods identified randomized controlled trials (RCTs) and non-randomized interventions of health behaviour change for couples with at least one member at risk of a chronic physical illness, published from 1990-2014. We identified 14 studies, targeting the following health behaviours: cancer prevention (6), obesity (1), diet (2), smoking in pregnancy (2), physical activity (1) and multiple health behaviours (2). In four out of seven trials couple-focused interventions were more effective than usual care. Of four RCTs comparing a couple-focused intervention to an individual intervention, two found that the couple-focused intervention was more effective. The studies were heterogeneous, and included participants at risk of a variety of illnesses. In many cases the intervention was compared to usual care for an individual or an individual-focused intervention, which meant the impact of the couplebased content could not be isolated. Three arm studies could determine whether any added benefits of couple-focused interventions are due to adding the partner or specific content of couple-focused interventions. Statement of contribution What is already known on this subject? Health behaviours and health behaviour change are more often concordant across couples than between individuals in the general population. Couple-focused interventions for chronic conditions are more effective than individual interventions or usual care (Martire, Schulz, Helgeson, Small, & Saghafi, ). What does this study add? Identified studies targeted a variety of health behaviours, with few studies in any one area. Further assessment of the effectiveness of couple-focused versus individual interventions for those at risk is needed. Three-arm study designs are needed to determine benefits of targeting couples versus couple-focused intervention content. © 2017 The Authors. British Journal of Health Psychology published by John Wiley & Sons Ltd on behalf of the British Psychological Society.

Stiffness Characteristics of Composite Rotor Blades With Elastic Couplings

NASA Technical Reports Server (NTRS)

Piatak, David J.; Nixon, Mark W.; Kosmatka, John B.

1997-01-01

Recent studies on rotor aeroelastic response and stability have shown the beneficial effects of incorporating elastic couplings in composite rotor blades. However, none of these studies have clearly identified elastic coupling limits and the effects of elastic couplings on classical beam stiffnesses of representative rotor blades. Knowledge of these limits and effects would greatly enhance future aeroelastic studies involving composite rotor blades. The present study addresses these voids and provides a preliminary design database for investigators who may wish to study the effects of elastic couplings on representative blade designs. The results of the present study should provide a basis for estimating the potential benefits associated with incorporating elastic couplings without the need for first designing a blade cross section and then performing a cross-section analysis to obtain the required beam section properties as is customary in the usual one-dimensional beam-type approach.

Sex-specific effects of intranasal oxytocin on autonomic nervous system and emotional responses to couple conflict

PubMed Central

Nater, Urs M.; Schaer, Marcel; La Marca, Roberto; Bodenmann, Guy; Ehlert, Ulrike; Heinrichs, Markus

2013-01-01

Unhappy couple relationships are associated with impaired individual health, an effect thought to be mediated through ongoing couple conflicts. Little is known, however, about the underlying mechanisms regulating psychobiological stress, and particularly autonomic nervous system (ANS) reactivity, during negative couple interaction. In this study, we tested the effects of the neuropeptide oxytocin on ANS reactivity during couple conflict in a standardized laboratory paradigm. In a double-blind, placebo-controlled design, 47 heterosexual couples (total n = 94) received oxytocin or placebo intranasally prior to instructed couple conflict. Participants’ behavior was videotaped and salivary alpha-amylase (sAA), a measure of sympathetic activity, and emotional arousal were repeatedly measured during the experiment. Oxytocin significantly reduced sAA during couple conflict in women, whereas men showed increases in sAA levels (sex × group interaction: B = −49.36, t = −2.68, P = 0.009). In men, these increases were related to augmented emotional arousal (r = 0.286, P = 0.028) and more positive behavior (r = 0.291, P = 0.026), whereas there was no such association in women. Our results imply sex-specific effects of oxytocin on sympathetic activity, to negative couple interaction, with the neuropeptide reducing sAA responses and emotional arousal in women while increasing them in men. PMID:22842905

Effect of Propellant Feed System Coupling and Hydraulic Parameters on Analysis of Chugging

NASA Technical Reports Server (NTRS)

Wood, Don J.; Dorsch, Robert G.

1967-01-01

A digital distributed parameter model was used to study the effects of propellant-feed- system coupling and various hydraulic parameters on the analytical prediction of chugging instabilities. Coupling between the combustion chamber and feed system was controlled by varying the compliance of the injector-dome region. The coupling with the feed system above the pump was varied by changing the amount of cavitation compliance at the pump inlet. The stability limits and chugging frequencies proved to be strongly dependent on the degree of feed-system coupling. The maximum stability condition occurred with intermediate coupling. Under conditions of a high degree of feed-system-combustor coupling, the stability limits and chugging frequencies were primarily dependent on the feed-system characteristics; the responses were characterized by beating patterns. For the system analyzed, the pump suction line had little effect on the stability limits or chugging frequencies. Beating, present under the condition of near zero injector -dome compliance, was eliminated when the suction line was decoupled by employing a sufficiently high value of pump-inlet compliance. Under conditions of maximum feed-system coupling, the magnitude and distribution of line losses in the discharge line had a significant effect on the stability limits but had negligible effect on the chugging frequency and beating characteristics. Also, the length of the discharge line greatly affected the stability limits, chugging frequency, and beating characteristics. The length of the suction line, however, had little effect on the stability limits and chugging frequency but did influence the beating pattern. A resistive-shunt device attached to the pump discharge line to suppress chugging was investigated. The analysis showed that the device was effective under conditions of high feed-system coupling.

Coupled effects of solution chemistry and hydrodynamics on the mobility and transport of quantum dot nanomaterials in the Vadose Zone

USDA-ARS?s Scientific Manuscript database

To investigate the coupled effects of solution chemistry and vadose zone processes on the mobility of quantum dot (QD) nanoparticles, laboratory scale transport experiments were performed. The complex coupled effects of ionic strength, size of QD aggregates, surface tension, contact angle, infiltrat...

Immediate effect of couple relationship education on low-satisfaction couples: a randomized clinical trial plus an uncontrolled trial replication.

PubMed

Kim Halford, W; Pepping, Christopher A; Hilpert, Peter; Bodenmann, Guy; Wilson, Keithia L; Busby, Dean; Larson, Jeffry; Holman, Thomas

2015-05-01

Couple relationship education (RE) usually is conceived of as relationship enhancement for currently satisfied couples, with a goal of helping couples sustain satisfaction. However, RE also might be useful as a brief, accessible intervention for couples with low satisfaction. Two studies were conducted that tested whether couples with low relationship satisfaction show meaningful gains after RE. Study 1 was a three-condition randomized controlled trial in which 182 couples were randomly assigned to RELATE with Couple CARE (RCC), a flexible delivery education program for couples, or one of two control conditions. Couples with initially low satisfaction receiving RCC showed a moderate increase in relationship satisfaction (d=0.50) relative to the control. In contrast, couples initially high in satisfaction showed little change and there was no difference between RCC and the control conditions. Study 2 was an uncontrolled trial of the Couple Coping Enhancement Training (CCET) administered to 119 couples. Couples receiving CCET that had initially low satisfaction showed a moderate increase in satisfaction (g=.44), whereas initially highly satisfied couples showed no change. Brief relationship education can assist somewhat distressed couples to enhance satisfaction, and has potential as a cost-effective way of enhancing the reach of couple interventions. Copyright © 2015. Published by Elsevier Ltd.

Clausius inequality beyond the weak-coupling limit: the quantum Brownian oscillator.

PubMed

Kim, Ilki; Mahler, Günter

2010-01-01

We consider a quantum linear oscillator coupled at an arbitrary strength to a bath at an arbitrary temperature. We find an exact closed expression for the oscillator density operator. This state is noncanonical but can be shown to be equivalent to that of an uncoupled linear oscillator at an effective temperature T*(eff) with an effective mass and an effective spring constant. We derive an effective Clausius inequality deltaQ*(eff)< or =T*(eff)dS , where deltaQ*(eff) is the heat exchanged between the effective (weakly coupled) oscillator and the bath, and S represents a thermal entropy of the effective oscillator, being identical to the von-Neumann entropy of the coupled oscillator. Using this inequality (for a cyclic process in terms of a variation of the coupling strength) we confirm the validity of the second law. For a fixed coupling strength this inequality can also be tested for a process in terms of a variation of either the oscillator mass or its spring constant. Then it is never violated. The properly defined Clausius inequality is thus more robust than assumed previously.

Motivating Action and Maintaining Change: The Time-Varying Role of Homework Following a Brief Couples' Intervention.

PubMed

Hawrilenko, Matt; Eubanks Fleming, C J; Goldstein, Alana S; Cordova, James V

2016-07-01

Studies regarding the effectiveness of homework assignments in cognitive-behavioral treatments have demonstrated mixed results. This study investigated predictors of compliance with homework recommendations and the time-varying relationship of recommendation completion with treatment response in a brief couples' intervention (N = 108). More satisfied couples and couples with more motivation to change completed more recommendations, whereas couples with children completed fewer. The association between recommendation completion and treatment response varied with the passage of time, with the strongest effect observed 6 months after the intervention, but no discernible differences at 1 year postintervention. Couples that completed more recommendations experienced more rapid treatment gains, but even those couples doing substantially fewer recommendations ultimately realized equivalent treatment effects, although they progressed more slowly. Implications are discussed. © 2015 American Association for Marriage and Family Therapy.

All-optical measurement of interlayer exchange coupling in Fe/Pt/FePt thin films

NASA Astrophysics Data System (ADS)

Berk, C.; Ganss, F.; Jaris, M.; Albrecht, M.; Schmidt, H.

2018-01-01

Time Resolved Magneto Optic Kerr Effect spectroscopy was used to all-optically study the dynamics in exchange coupled Fe(10 nm)/Pt(x = 0-5 nm)/FePt (10 nm) thin films. As the Pt spacer decreases, the effective magnetization of the layers is seen to evolve towards the strong coupling limit where the two films can be described by a single effective magnetization. The coupling begins at x = 1.5 nm and reaches a maximum exchange coupling constant of 2.89 erg/cm2 at x = 0 nm. The films are ferromagnetically coupled at all Pt thicknesses in the exchange coupled regime (x ≤ 1.5 nm). A procedure for extracting the interlayer exchange constant by measuring the magnetic precession frequencies at multiple applied fields and angles is outlined. The dynamics are well reproduced using micromagnetic simulations.

Field experiment and numerical simulation of coupling non-Darcy flow caused by curtain and pumping well in foundation pit dewatering

NASA Astrophysics Data System (ADS)

Wang, Jianxiu; Liu, Xiaotian; Wu, Yuanbin; Liu, Shaoli; Wu, Lingao; Lou, Rongxiang; Lu, Jiansheng; Yin, Yao

2017-06-01

High-velocity non-Darcy flow produced larger drawdown than Darcy flow under the same pumping rate. When the non-Darcy flow caused by curtain met non-Darcy flow caused by pumping wells, superposition and amplification effect occurred in the coupling area, the non-Darcy flow was defined as coupling non-Darcy flow. The coupling non-Darcy flow can be produced and controlled using different combination of curtain and pumping wells in foundation pit dewatering to obtain the maximum drawdown using the minimum pumping rate. The Qianjiang Century City Station foundation pit of Hangzhou subway, China, was selected as background. Field experiments were performed to observe the coupling non-Darcy flow in round gravel. A generalized conceptual model was established to study the coupling effect under different combination of curtain and pumping wells. Numerical simulations of the coupling non-Darcy flow in foundation pit dewatering were carried out based on the Forchheimer equation. The non-Darcy flow area and flow velocity were influenced by the coupling effect. Short filter tube, large pumping rate, small horizontal distance between filter tube and diaphragm wall, and small vertical distance between the filter tube and confined aquifer roof effectively strengthened the coupling effect and obtained a large drawdown. The pumping wells installed close to a curtain was an intentional choice designed to create coupling non-Darcy flow and obtain the maximize drawdown. It can be used in the dewatering of a long and narrow foundation pit, such as a subway foundation pit.

Global Effects of Superparameterization on Hydrothermal Land-Atmosphere Coupling on Multiple Timescales

NASA Astrophysics Data System (ADS)

Qin, Hongchen; Pritchard, Michael S.; Kooperman, Gabriel J.; Parishani, Hossein

2018-02-01

Many conventional General Circulation Models (GCMs) in the Global Land-Atmosphere Coupling Experiment (GLACE) tend to produce what is now recognized as overly strong land-atmosphere (L-A) coupling. We investigate the effects of cloud Superparameterization (SP) on L-A coupling on timescales beyond diurnal where it has been recently shown to have a favorable muting effect hydrologically. Using the Community Atmosphere Model v3.5 (CAM3.5) and its Superparameterized counterpart SPCAM3.5, we conducted soil moisture interference experiments following the GLACE and Atmospheric Model Intercomparison Project (AMIP) protocols. The results show that, on weekly-to-subseasonal timescales, SP also mutes hydrologic L-A coupling. This is detectable globally, and happens through the evapotranspiration-precipitation segment. But on seasonal timescales, SP does not exhibit detectable effects on hydrologic L-A coupling. Two robust regional effects of SP on thermal L-A coupling have also been explored. Over the Arabian Peninsula, SP reduces thermal L-A coupling through a straightforward control by mean rainfall reduction. More counterintuitively, over the Southwestern US and Northern Mexico, SP enhances the thermal L-A coupling in a way that is independent of rainfall and soil moisture. This signal is associated with a systematic and previously unrecognized effect of SP that produces an amplified Bowen ratio, and is detectable in multiple SP model versions and experiment designs. In addition to amplifying the present-day Bowen ratio, SP is found to amplify the climate sensitivity of Bowen ratio as well, which likely plays a role in influencing climate change predictions at the L-A interface.

The Effects of Partnered Exercise on Physical Intimacy in Couples Coping with Prostate Cancer

PubMed Central

Lyons, Karen S.; Winters-Stone, Kerri M.; Bennett, Jill A.; Beer, Tomasz M.

2015-01-01

Objective The study examined whether couples coping with prostate cancer participating in a partnered exercise program - Exercising Together (ET) - experienced higher levels of physical intimacy (i.e., affectionate & sexual behavior) than couples in a usual care (UC) control group. Method Men and their wives (n=64 couples) were randomly assigned to either the ET or UC group. Couples in the ET group engaged in partnered strength-training twice weekly for six months. Multilevel modeling was used to explore the effects of ET on husband and wife engagement in both affectionate and sexual behaviors over time. Results Controlling for relationship quality, wives in ET showed significant increases in engagement in affectionate behaviors compared to wives in UC. No intervention effects were found for husbands. Conclusion Couple-based approaches to physical intimacy, after a cancer diagnosis, that facilitate collaborative engagement in non-sexual physical activities for the couple have potential to be effective for wives. More research is needed in this area to determine couples most amenable to such exercise strategies, optimal timing in the cancer trajectory, and the benefits of combining partnered exercise with more traditional relationship-focused strategies. PMID:26462060

Traditional Versus Integrative Behavioral Couple Therapy for Significantly and Chronically Distressed Married Couples.

ERIC Educational Resources Information Center

Christensen, Andrew; Atkins, David C.; Berns, Sara; Wheeler, Jennifer; Baucom, Donald H.; Simpson, Lorelei E.

2004-01-01

A randomized clinical trial compared the effects of traditional behavioral couple therapy (TBCT) and integrative behavioral couple therapy (IBCT) on 134 seriously and chronically distressed married couples, stratified into moderately and severely distressed groups. Couples in IBCT made steady improvements in satisfaction throughout the course of…

Coupling time constants of striated and copper-plated coated conductors and the potential of striation to reduce shielding-current-induced fields in pancake coils

NASA Astrophysics Data System (ADS)

Amemiya, Naoyuki; Tominaga, Naoki; Toyomoto, Ryuki; Nishimoto, Takuma; Sogabe, Yusuke; Yamano, Satoshi; Sakamoto, Hisaki

2018-07-01

The shielding-current-induced field is a serious concern for the applications of coated conductors to magnets. The striation of the coated conductor is one of the countermeasures, but it is effective only after the decay of the coupling current, which is characterised with the coupling time constant. In a non-twisted striated coated conductor, the coupling time constant is determined primarily by its length and the transverse resistance between superconductor filaments, because the coupling current could flow along its entire length. We measured and numerically calculated the frequency dependences of magnetisation losses in striated and copper-plated coated conductors with various lengths and their stacks at 77 K and determined their coupling time constants. Stacked conductors simulate the turns of a conductor wound into a pancake coil. Coupling time constants are proportional to the square of the conductor length. Stacking striated coated conductors increases the coupling time constants because the coupling currents in stacked conductors are coupled to one another magnetically to increase the mutual inductances for the coupling current paths. We carried out the numerical electromagnetic field analysis of conductors wound into pancake coils and determined their coupling time constants. They can be explained by the length dependence and mutual coupling effect observed in stacked straight conductors. Even in pancake coils with practical numbers of turns, i.e. conductor lengths, the striation is effective to reduce the shielding-current-induced fields for some dc applications.

A control approach to cross-coupling compensation of piezotube scanners in tapping-mode atomic force microscope imaging.

PubMed

Wu, Ying; Shi, Jian; Su, Chanmin; Zou, Qingze

2009-04-01

In this article, an approach based on the recently developed inversion-based iterative control (IIC) to cancel the cross-axis coupling effect of piezoelectric tube scanners (piezoscanners) in tapping-mode atomic force microscope (AFM) imaging is proposed. Cross-axis coupling effect generally exists in piezoscanners used for three-dimensional (x-y-z axes) nanopositioning in applications such as AFM, where the vertical z-axis movement can be generated by the lateral x-y axes scanning. Such x/y-to-z cross-coupling becomes pronounced when the scanning is at large range and/or at high speed. In AFM applications, the coupling-caused position errors, when large, can generate various adverse effects, including large imaging and topography distortions, and damage of the cantilever probe and/or the sample. This paper utilizes the IIC technique to obtain the control input to precisely track the coupling-caused x/y-to-z displacement (with sign-flipped). Then the obtained input is augmented as a feedforward control to the existing feedback control in tapping-mode imaging, resulting in the cancellation of the coupling effect. The proposed approach is illustrated through two exemplary applications in industry, the pole-tip recession examination, and the nanoasperity measurement on hard-disk drive. Experimental results show that the x/y-to-z coupling effect in large-range (20 and 45 microm) tapping-mode imaging at both low to high scan rates (2, 12.2 to 24.4 Hz) can be effectively removed.

Melt structure and self-nucleation of ethylene copolymers

NASA Astrophysics Data System (ADS)

Alamo, Rufina G.

A strong memory effect of crystallization has been observed in melts of random ethylene copolymers well above the equilibrium melting temperature. These studies have been carried out by DSC, x-ray, TEM and optical microscopy on a large number of model, narrow, and broad copolymers with different comonomer types and contents. Melt memory is correlated with self-seeds that increase the crystallization rate of ethylene copolymers. The seeds are associated with molten ethylene sequences from the initial crystals that remain in close proximity and lower the nucleation barrier. Diffusion of all sequences to a randomized melt state is a slow process, restricted by topological chain constraints (loops, knots, and other entanglements) that build in the intercrystalline region during crystallization. Self-seeds dissolve above a critical melt temperature that demarcates homogeneity of the copolymer melt. There is a critical threshold level of crystallinity to observe the effect of melt memory on crystallization rate, thus supporting the correlation between melt memory and the change in melt structure during copolymer crystallization. Unlike binary blends, commercial ethylene-1-alkene copolymers with a range in inter-chain comonomer composition between 1 and about 15 mol % display an inversion of the crystallization rate in a range of melt temperatures where narrow copolymers show a continuous acceleration of the rate. With decreasing the initial melt temperature, broadly distributed copolymers show enhanced crystallization followed by a decrease of crystallization rate. The inversion demarcates the onset of liquid-liquid phase separation (LLPS) and a reduction of self-nuclei due to the strong thermodynamic drive for molecular segregation inside the binodal. The strong effect of melt memory on crystallization rate can be used to identify liquid-liquid phase separation in broadly distributed copolymers, and offers strategies to control the state of copolymer melts in ways of technological relevance for melt processing of LLDPE and other random olefin copolymers. References: B. O. Reid, et al., Macromolecules 46, 6485-6497, 2013 H. Gao, et al., Macromolecules 46, 6498-6506, 2013 A. Mamun et al., Macromolecules 47, 7958-7970, 2014 X. Chen et al., Macromol. Chem. Phys. 216, 1220 -1226, 2015 M. Ren et al., Macromol. Symp. 356, 131-141, 2015 Work supported by the NSF (DMR1105129).

Effects of a Randomized Couple-Based Intervention on Quality of Life of Breast Cancer Patients and Their Partners

ERIC Educational Resources Information Center

Kayser, Karen; Feldman, Barry N.; Borstelmann, Nancy A.; Daniels, Ann A.

2010-01-01

The purpose of this study was to determine the effectiveness of a couple-based intervention on the quality of life (QOL) of early-stage breast cancer patients and their partners. A randomized controlled design was used to assign couples to either the hospital standard social work services (SSWS) or a couple-based intervention, the Partners in…

Quantification of strain and charge co-mediated magnetoelectric coupling on ultra-thin Permalloy/PMN-PT interface.

PubMed

Nan, Tianxiang; Zhou, Ziyao; Liu, Ming; Yang, Xi; Gao, Yuan; Assaf, Badih A; Lin, Hwaider; Velu, Siddharth; Wang, Xinjun; Luo, Haosu; Chen, Jimmy; Akhtar, Saad; Hu, Edward; Rajiv, Rohit; Krishnan, Kavin; Sreedhar, Shalini; Heiman, Don; Howe, Brandon M; Brown, Gail J; Sun, Nian X

2014-01-14

Strain and charge co-mediated magnetoelectric coupling are expected in ultra-thin ferromagnetic/ferroelectric multiferroic heterostructures, which could lead to significantly enhanced magnetoelectric coupling. It is however challenging to observe the combined strain charge mediated magnetoelectric coupling, and difficult in quantitatively distinguish these two magnetoelectric coupling mechanisms. We demonstrated in this work, the quantification of the coexistence of strain and surface charge mediated magnetoelectric coupling on ultra-thin Ni0.79Fe0.21/PMN-PT interface by using a Ni0.79Fe0.21/Cu/PMN-PT heterostructure with only strain-mediated magnetoelectric coupling as a control. The NiFe/PMN-PT heterostructure exhibited a high voltage induced effective magnetic field change of 375 Oe enhanced by the surface charge at the PMN-PT interface. Without the enhancement of the charge-mediated magnetoelectric effect by inserting a Cu layer at the PMN-PT interface, the electric field modification of effective magnetic field was 202 Oe. By distinguishing the magnetoelectric coupling mechanisms, a pure surface charge modification of magnetism shows a strong correlation to polarization of PMN-PT. A non-volatile effective magnetic field change of 104 Oe was observed at zero electric field originates from the different remnant polarization state of PMN-PT. The strain and charge co-mediated magnetoelectric coupling in ultra-thin magnetic/ferroelectric heterostructures could lead to power efficient and non-volatile magnetoelectric devices with enhanced magnetoelectric coupling.

Coupling and decoupling of the accelerating units for pulsed synchronous linear accelerator

NASA Astrophysics Data System (ADS)

Shen, Yi; Liu, Yi; Ye, Mao; Zhang, Huang; Wang, Wei; Xia, Liansheng; Wang, Zhiwen; Yang, Chao; Shi, Jinshui; Zhang, Linwen; Deng, Jianjun

2017-12-01

A pulsed synchronous linear accelerator (PSLA), based on the solid-state pulse forming line, photoconductive semiconductor switch, and high gradient insulator technologies, is a novel linear accelerator. During the prototype PSLA commissioning, the energy gain of proton beams was found to be much lower than expected. In this paper, the degradation of the energy gain is explained by the circuit and cavity coupling effect of the accelerating units. The coupling effects of accelerating units are studied, and the circuit topologies of these two kinds of coupling effects are presented. Two methods utilizing inductance and membrane isolations, respectively, are proposed to reduce the circuit coupling effects. The effectiveness of the membrane isolation method is also supported by simulations. The decoupling efficiency of the metal drift tube is also researched. We carried out the experiments on circuit decoupling of the multiple accelerating cavity. The result shows that both circuit decoupling methods could increase the normalized voltage.

An investigation of the effects of pitch-roll (de)-coupling on helicopter handling qualities

NASA Technical Reports Server (NTRS)

Ockier, C. J.; Pausder, H. J.; Blanken, C. L.

1995-01-01

An investigation of the effects of pitch-roll coupling on helicopter handling qualities was performed by the US Army and DLR, using a NASA ground-based and a DLR inflight simulator. Over 90 different coupling configurations were evaluated using a roll-axis tracking task. The results show that although the current ADS-33C coupling criterion discriminates against those types of coupling typical of conventionally controlled helicopters, it not always suited for the prediction of handling qualities of helicopters with modern control systems. Based on the observation that high frequency inputs during tracking are used to alleviate coupling, a frequency domain pitch-roll coupling criterion that uses the average coupling ratio between the bandwidth and neutral stability frequency is formulated. This criterion provides a more comprehensive coverage with respect to the different types of coupling and shows excellent consistency.

The Effectiveness of Emotionally Focused Couples Therapy on Sexual Satisfaction and Marital Adjustment of Infertile Couples with Marital Conflicts

PubMed Central

Soleimani, Ali Akbar; Najafi, Maryam; Ahmadi, Khodabakhsh; Javidi, Nasirudin; Hoseini Kamkar, Elnaz; Mahboubi, Mohamad

2015-01-01

Background The purpose of this investigation is to determine the efficacy of emotionally focused couples therapy (EFT-C) on enhancement of marital adjustment in infertile couples. Materials and Methods This was a semi-experimental study with a pre- and post-test design. We selected 30 infertile couples (60 subjects) by purposive sampling. Couples were randomly assigned to two groups, sample and control. Each group consisted of 15 couples who had marital maladjustment and low sexual satisfaction. Couples answered the marital adjustment and sexual satisfaction questionnaires at baseline after which the sample group received 10 sessions of EFT-C. Results Results of pre-test and post-test showed that EFT-C significantly impacted marital adjustment and sexual satisfaction. Conclusion EFT-C had a significant effect on enhancement of satisfaction, cohesion and affectional expression. This approach impacted physical and emotional sexual satisfaction of infertile couples. PMID:26644864

Tracking the coupling of two electroencephalogram series in the isoflurane and remifentanil anesthesia.

PubMed

Liang, Zhenhu; Liang, Shujuan; Wang, Yinghua; Ouyang, Gaoxiang; Li, Xiaoli

2015-02-01

Coupling in multiple electroencephalogram (EEG) signals provides a perspective tool to understand the mechanism of brain communication. In this study, we propose a method based on permutation cross-mutual information (PCMI) to investigate whether or not the coupling between EEG series can be used to quantify the effect of specific anesthetic drugs (isoflurane and remifentanil) on brain activities. A Rössler-Lorenz system and surrogate analysis was first employed to compare histogram-based mutual information (HMI) and PCMI for estimating the coupling of two nonlinear systems. Then, the HMI and the PCMI indices of EEG recordings from two sides of the forehead of 12 patients undergoing combined remifentanil and isoflurane anesthesia were demonstrated for tracking the effect of drug on the coupling of brain activities. Performance of all indices was assessed by the correlation coefficients (Rij) and relative coefficient of variation (CV). The PCMI can track the coupling strength of two nonlinear systems, and it is sensitive to the phase change of the coupling systems. Compared to the HMI, the PCMI has a better correlation with the coupling strength in nonlinear systems. The PCMI could track the effect of anesthesia and distinguish the consciousness state from the unconsciousness state. Moreover, at the embedding dimension m=4 and lag τ=1, the PCMI had a better performance than HMI in tracking the effect of anesthesia drugs on brain activities. As a measure of coupling, the PCMI was able to reflect the state of consciousness from two EEG recordings. The PCMI is a promising new coupling measure for estimating the effect of isoflurane and remifentanil anesthetic drugs on the brain activity. Copyright © 2014 International Federation of Clinical Neurophysiology. All rights reserved.

Thermal coupling and effect of subharmonic synchronization in a system of two VO2 based oscillators

NASA Astrophysics Data System (ADS)

Velichko, Andrey; Belyaev, Maksim; Putrolaynen, Vadim; Perminov, Valentin; Pergament, Alexander

2018-03-01

We explore a prototype of an oscillatory neural network (ONN) based on vanadium dioxide switching devices. The model system under study represents two oscillators based on thermally coupled VO2 switches. Numerical simulation shows that the effective action radius RTC of coupling depends both on the total energy released during switching and on the average power. It is experimentally and numerically proved that the temperature change ΔT commences almost synchronously with the released power peak and T-coupling reveals itself up to a frequency of about 10 kHz. For the studied switching structure configuration, the RTC value varies over a wide range from 4 to 45 μm, depending on the external circuit capacitance C and resistance Ri, but the variation of Ri is more promising from the practical viewpoint. In the case of a "weak" coupling, synchronization is accompanied by attraction effect and decrease of the main spectra harmonics width. In the case of a "strong" coupling, the number of effects increases, synchronization can occur on subharmonics resulting in multilevel stable synchronization of two oscillators. An advanced algorithm for synchronization efficiency and subharmonic ratio calculation is proposed. It is shown that of the two oscillators the leading one is that with a higher main frequency, and, in addition, the frequency stabilization effect is observed. Also, in the case of a strong thermal coupling, the limit of the supply current parameters, for which the oscillations exist, expands by ∼10%. The obtained results have a universal character and open up a new kind of coupling in ONNs, namely, T-coupling, which allows for easy transition from 2D to 3D integration. The effect of subharmonic synchronization hold promise for application in classification and pattern recognition.

Mental distress predicts divorce over 16 years: the HUNT study.

PubMed

Idstad, Mariann; Torvik, Fartein Ask; Borren, Ingrid; Rognmo, Kamilla; Røysamb, Espen; Tambs, Kristian

2015-04-01

The association between mental distress and divorce is well established in the literature. Explanations are commonly classified within two different frameworks; social selection (mentally distressed people are selected out of marriage) and social causation (divorce causes mental distress). Despite a relatively large body of literature on this subject, selection effects are somewhat less studied, and research based on data from both spouses is scarce. The purpose of the present study is to investigate selection effects both at the individual level and the couple level. The current study is based on couple-level data from a Norwegian representative sample including 20,233 couples. Long-term selection effects were tested for by means of Cox proportional hazard models, using mental distress in both partners at baseline as predictors of divorce the next 16 years. Three identical sets of analyses were run. The first included the total sample, whereas the second and third excluded couples who divorced within the first 4 or 8 years after baseline, respectively. An interaction term between mental distress in husband and in wife was specified and tested. Hazard of divorce was significantly higher in couples with one mentally distressed partner than in couples with no mental distress in all analyses. There was also a significant interaction effect showing that the hazard of divorce for couples with two mentally distressed partners was higher than for couples with one mentally distressed partner, but lower than what could be expected from the combined main effects of two mentally distressed partners. Our results suggest that mentally distressed individuals are selected out of marriage. We also found support for a couple-level effect in which spouse similarity in mental distress to a certain degree seems to protect against divorce.

Mutual Coupling and Compensation in FMCW MIMO Radar Systems

NASA Astrophysics Data System (ADS)

Schmid, Christian M.; Feger, Reinhard; Wagner, Christoph; Stelzer, Andreas

2011-09-01

This paper deals with mutual coupling, its effects and the compensation thereof in frequency-modulated continuous-wave (FMCW) multiple-input multiple-output (MIMO) array radar systems. Starting with a signal model we introduce mutual coupling and its primary sources in FMCW MIMO systems. We also give a worst-case boundary of the effects that mutual coupling can have on the side lobe level of an array. A method of dealing with and compensating for these effects is covered in this paper and verified by measurements from a 77-GHz FMCW radar system.

Magnitude of finite-nucleus-size effects in relativistic density functional computations of indirect NMR nuclear spin-spin coupling constants.

PubMed

Autschbach, Jochen

2009-09-14

A spherical Gaussian nuclear charge distribution model has been implemented for spin-free (scalar) and two-component (spin-orbit) relativistic density functional calculations of indirect NMR nuclear spin-spin coupling (J-coupling) constants. The finite nuclear volume effects on the hyperfine integrals are quite pronounced and as a consequence they noticeably alter coupling constants involving heavy NMR nuclei such as W, Pt, Hg, Tl, and Pb. Typically, the isotropic J-couplings are reduced in magnitude by about 10 to 15 % for couplings between one of the heaviest NMR nuclei and a light atomic ligand, and even more so for couplings between two heavy atoms. For a subset of the systems studied, viz. the Hg atom, Hg(2) (2+), and Tl--X where X=Br, I, the basis set convergence of the hyperfine integrals and the coupling constants was monitored. For the Hg atom, numerical and basis set calculations of the electron density and the 1s and 6s orbital hyperfine integrals are directly compared. The coupling anisotropies of TlBr and TlI increase by about 2 % due to finite-nucleus effects.

Higgs boson self-coupling from two-loop analysis

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

Alhendi, H. A.; National Center for Mathematics and Physics, KACST P. O. Box 6086, Riyadh 11442; Barakat, T.

2010-09-01

The scale invariant of the effective potential of the standard model at two loop is used as a boundary condition under the assumption that the two-loop effective potential approximates the full effective potential. This condition leads with the help of the renormalization-group functions of the model at two loop to an algebraic equation of the scalar self-coupling with coefficients that depend on the gauge and the top quark couplings. It admits only two real positive solutions. One of them, in the absence of the gauge and top quark couplings, corresponds to the nonperturbative ultraviolet fixed point of the scalar renormalization-groupmore » function and the other corresponds to the perturbative infrared fixed point. The dependence of the scalar coupling on the top quark and the strong couplings at two-loop radiative corrections is analyzed.« less

Communication and contraceptive practices in adolescent couples.

PubMed

Polit-O'Hara, D; Kahn, J R

1985-01-01

This study presents a descriptive analysis of the content, frequency, and timing of couple communication regarding birth control among stable, sexually active adolescent couples, and the effect of communication on actual contraceptive practices. The sample consisted of 83 couples in which the female partner was 15-18 years old. All couples had been sexually active at least two months prior to the interview. The majority of couples had discussed birth control on at least one occasion, but discussions prior to first intercourse were atypical. Couples with good communication patterns were more likely to practice effective contraception. One-fourth of the respondents felt that contraception had not been adequately discussed, and these individuals were found to be most at risk to an unintended pregnancy.

Chimera states: Effects of different coupling topologies

NASA Astrophysics Data System (ADS)

Bera, Bidesh K.; Majhi, Soumen; Ghosh, Dibakar; Perc, Matjaž

2017-04-01

Collective behavior among coupled dynamical units can emerge in various forms as a result of different coupling topologies as well as different types of coupling functions. Chimera states have recently received ample attention as a fascinating manifestation of collective behavior, in particular describing a symmetry breaking spatiotemporal pattern where synchronized and desynchronized states coexist in a network of coupled oscillators. In this perspective, we review the emergence of different chimera states, focusing on the effects of different coupling topologies that describe the interaction network connecting the oscillators. We cover chimera states that emerge in local, nonlocal and global coupling topologies, as well as in modular, temporal and multilayer networks. We also provide an outline of challenges and directions for future research.

Theoretical and numerical evaluation of polarimeter using counter-circularly-polarized-probing-laser under the coupling between Faraday and Cotton-Mouton effect.

PubMed

Imazawa, Ryota; Kawano, Yasunori; Itami, Kiyoshi

2016-04-01

This study evaluated an effect of an coupling between the Faraday and Cotton-Mouton effect to a measurement signal of the Dodel-Kunz method which uses counter-circular-polarized probing-laser for measuring the Faraday effect. When the coupling is small (the Faraday effect is dominant and the characteristic eigenmodes are approximately circularly polarized), the measurement signal can be algebraically expressed and it is shown that the finite effect of the coupling is still significant. When the Faraday effect is not dominant, a numerical calculation is necessary. The numerical calculation under an ITER-like condition (Bt = 5.3 T, Ip = 15 MA, a = 2 m, ne = 10(20) m(-3) and λ = 119 μm) showed that difference between the pure Faraday rotation and the measurement signal of the Dodel-Kunz method was an order of one degree, which exceeds allowable error of ITER poloidal polarimeter. In conclusion, similar to other polarimeter techniques, the Dodel-Kunz method is not free from the coupling between the Faraday and Cotton-Mouton effect.

More mental health problems after divorce in couples with high pre-divorce alcohol consumption than in other divorced couples: results from the HUNT-study.

PubMed

Rognmo, Kamilla; Torvik, Fartein A; Idstad, Mariann; Tambs, Kristian

2013-09-17

Divorce is associated with mental health problems, and heavy drinking is related to higher risk of divorce. Less is known about the effects of divorce in couples where one or both drinks heavily. There are, however, reasons to expect different consequences of divorce in heavy risk using couples compared to other couples. Spouses of abusers may experience the divorce as a relief, whereas abusers may find it extra difficult to be left single. The aim of the study is to compare the effect of divorce on mental health in heavy drinking couples to the effect in couples who drink less. Registry data were matched with data from the Nord-Trøndelag Health Study (HUNT 1 (T1) and 2 (T2)), enabling longitudinal analyses of approximately 11,000 couples. Interaction terms between 1) alcohol use on T1 and divorce between T1 and T2 (11 year time lag), and 2) alcohol use on T1 and time since divorce at T2 for all divorced couples were tested to examine changes in mental health between T1 and T2 for a) spouses of high-risk compared to low-risk users, and b) high-risk compared to low-risk users themselves. Data were analyzed using multivariate analysis of variance. There was a general effect of divorce on change in mental health between T1 and T2. We observed a significantly stronger worsening in mental health in female high-risk users and their spouses than in divorced low-risk users and their spouses. The results also suggest that the strain after divorce lasts longer in women with a high alcohol consumption and their spouses. Divorce seems to affect couples where one or both drink heavily more than couples with a low consumption. Also there was some evidence of a slower healing of mental health problems after divorce in alcohol exposed couples than in other couples. The results only reached significance for female high consumers and their spouses, but due to limited statistical power, safe conclusions about gender specific effects cannot be drawn.

Quantum phase transitions in effective spin-ladder models for graphene zigzag nanoribbons

NASA Astrophysics Data System (ADS)

Koop, Cornelie; Wessel, Stefan

2017-10-01

We examine the magnetic correlations in quantum spin models that were derived recently as effective low-energy theories for electronic correlation effects on the edge states of graphene nanoribbons. For this purpose, we employ quantum Monte Carlo simulations to access the large-distance properties, accounting for quantum fluctuations beyond mean-field-theory approaches to edge magnetism. For certain chiral nanoribbons, antiferromagnetic interedge couplings were previously found to induce a gapped quantum disordered ground state of the effective spin model. We find that the extended nature of the intraedge couplings in the effective spin model for zigzag nanoribbons leads to a quantum phase transition at a large, finite value of the interedge coupling. This quantum critical point separates the quantum disordered region from a gapless phase of stable edge magnetism at weak intraedge coupling, which includes the ground states of spin-ladder models for wide zigzag nanoribbons. To study the quantum critical behavior, the effective spin model can be related to a model of two antiferromagnetically coupled Haldane-Shastry spin-half chains with long-ranged ferromagnetic intrachain couplings. The results for the critical exponents are compared also to several recent renormalization-group calculations for related long-ranged interacting quantum systems.

Synchronization properties of network motifs: Influence of coupling delay and symmetry

NASA Astrophysics Data System (ADS)

D'Huys, O.; Vicente, R.; Erneux, T.; Danckaert, J.; Fischer, I.

2008-09-01

We investigate the effect of coupling delays on the synchronization properties of several network motifs. In particular, we analyze the synchronization patterns of unidirectionally coupled rings, bidirectionally coupled rings, and open chains of Kuramoto oscillators. Our approach includes an analytical and semianalytical study of the existence and stability of different in-phase and out-of-phase periodic solutions, complemented by numerical simulations. The delay is found to act differently on networks possessing different symmetries. While for the unidirectionally coupled ring the coupling delay is mainly observed to induce multistability, its effect on bidirectionally coupled rings is to enhance the most symmetric solution. We also study the influence of feedback and conclude that it also promotes the in-phase solution of the coupled oscillators. We finally discuss the relation between our theoretical results on delay-coupled Kuramoto oscillators and the synchronization properties of networks consisting of real-world delay-coupled oscillators, such as semiconductor laser arrays and neuronal circuits.

Ab initio study of dynamical E × e Jahn-Teller and spin-orbit coupling effects in the transition-metal trifluorides TiF3, CrF3, and NiF3

NASA Astrophysics Data System (ADS)

Mondal, Padmabati; Opalka, Daniel; Poluyanov, Leonid V.; Domcke, Wolfgang

2012-02-01

Multiconfiguration ab initio methods have been employed to study the effects of Jahn-Teller (JT) and spin-orbit (SO) coupling in the transition-metal trifluorides TiF3, CrF3, and NiF3, which possess spatially doubly degenerate excited states (ME) of even spin multiplicities (M = 2 or 4). The ground states of TiF3, CrF3, and NiF3 are nondegenerate and exhibit minima of D3h symmetry. Potential-energy surfaces of spatially degenerate excited states have been calculated using the state-averaged complete-active-space self-consistent-field method. SO coupling is described by the matrix elements of the Breit-Pauli operator. Linear and higher order JT coupling constants for the JT-active bending and stretching modes as well as SO-coupling constants have been determined. Vibronic spectra of JT-active excited electronic states have been calculated, using JT Hamiltonians for trigonal systems with inclusion of SO coupling. The effect of higher order (up to sixth order) JT couplings on the vibronic spectra has been investigated for selected electronic states and vibrational modes with particularly strong JT couplings. While the weak SO couplings in TiF3 and CrF3 are almost completely quenched by the strong JT couplings, the stronger SO coupling in NiF3 is only partially quenched by JT coupling.

Evaluation of an effective multifaceted implementation strategy for elective single-embryo transfer after in vitro fertilization.

PubMed

Kreuwel, I A M; van Peperstraten, A M; Hulscher, M E J L; Kremer, J A M; Grol, R P T M; Nelen, W L D M; Hermens, R P M G

2013-02-01

What is the relationship between the rate of elective single-embryo transfer (eSET) and couples' exposure to different elements of a multifaceted implementation strategy? Additional elements in a multifaceted implementation strategy do not result in an increased eSET rate. A multifaceted eSET implementation strategy with four different elements is effective in increasing the eSET rate by 11%. It is unclear whether every strategy element contributes equally to the strategy's effectiveness. An observational study was performed among 222 subfertile couples included in a previously performed randomized controlled trial. Of the 222 subfertile couples included, 109 couples received the implementation strategy and 113 couples received standard IVF care. A multivariate regression analysis assessed the effectiveness of four different strategy elements on the decision about the number embryos to be transferred. Questionnaires evaluated the experiences of couples with the different elements. Of the couples who received the implementation strategy, almost 50% (52/109) were exposed to all the four elements of the strategy. The remaining 57 couples who received two or three elements of the strategy could be divided into two further classes of exposure. Our analysis demonstrated that additional elements do not result in an increased eSET rate. In addition to the physician's advice, couples rated a decision aid and a counselling session as more important for their decision to transfer one or two embryos, compared with a phone call and a reimbursement offer (P < 0.001). The differences in eSET rate between exposure groups failed to reach significance, probably because of the small numbers of couples in each exposure group. Adding more elements to an implementation strategy does not always result in an increased effectiveness, which is in concordance with recent literature. This in-depth evaluation of a multifaceted intervention strategy could therefore help to modify strategies, by making them more effective and less expensive.

Role of Near Substrate and Bulk Polymer Morphology on Out-of-Plane Space-Charge Limited Hole Mobility.

PubMed

Turner, Johnathan; Gadisa, Abay

2016-12-07

Charge transport is a central issue in all types of organic electronic devices. In organic films, charge transport is crucially limited by film microstructure and the nature of the substrate/organic interface interactions. In this report, we discuss the influence of active layer thickness on space-charge limited hole transport in pristine polymer and polymer/fullerene bulk heterojunction thin films (∼15-300 nm) in a diode structure. According to the results, the out-of-plane hole mobility in pristine polymers is sensitive to the degree of polymer chain aggregation. Blending the polymers with a fullerene molecule does not change the trend of hole mobility if the polymer tends to make an amorphous structure. However, employing an aggregating polymer in a bulk heterojunction blend gives rise to a marked difference in charge carrier transport behavior compared to the pristine polymer and this difference is sensitive to active layer thickness. In aggregating polymer films, the thickness-dependent interchain interaction was found to have direct impact on hole mobility. The thickness-dependent mobility trend was found to correspond well with the trend of fill factors of corresponding bulk heterojunction solar cells. This investigation has a vital implication for material design and the development of efficient organic electronic devices, including solar cells and light-emitting diodes.

Crystal Structures of Beta- and Gammaretrovirus Fusion Proteins Reveal a Role for Electrostatic Stapling in Viral Entry

PubMed Central

Aydin, Halil; Cook, Jonathan D.

2014-01-01

Membrane fusion is a key step in the life cycle of all envelope viruses, but this process is energetically unfavorable; the transmembrane fusion subunit (TM) of the virion-attached glycoprotein actively catalyzes the membrane merger process. Retroviral glycoproteins are the prototypical system to study pH-independent viral entry. In this study, we determined crystal structures of extramembrane regions of the TMs from Mason-Pfizer monkey virus (MPMV) and xenotropic murine leukemia virus-related virus (XMRV) at 1.7-Å and 2.2-Å resolution, respectively. The structures are comprised of a trimer of hairpins that is characteristic of class I viral fusion proteins and now completes a structural library of retroviral fusion proteins. Our results allowed us to identify a series of intra- and interchain electrostatic interactions in the heptad repeat and chain reversal regions. Mutagenesis reveals that charge-neutralizing salt bridge mutations significantly destabilize the postfusion six-helix bundle and abrogate retroviral infection, demonstrating that electrostatic stapling of the fusion subunit is essential for viral entry. Our data indicate that salt bridges are a major stabilizing force on the MPMV and XMRV retroviral TMs and likely provide the key energetics for viral and host membrane fusion. PMID:24131724

Formation and decay of charge carriers in aggregate nanofibers consisting of poly(3-hexylthiophene)-coated gold nanoparticles.

PubMed

Lee, Dongki; Lee, Jaewon; Song, Ki-Hee; Rhee, Hanju; Jang, Du-Jeon

2016-01-21

Thin nanofibers (NFs) of J-dominant aggregates with a thickness of 15 nm and thick NFs of H-dominant aggregates with a thickness of 25 nm were fabricated by the self-assembly of poly(3-hexylthiophene)-coated gold nanoparticles. The formation and decay dynamics of the charge carriers, which are dependent on the aggregate types of NFs, was investigated by time-resolved emission and transient-absorption spectroscopy. With increasing excitation energy, the fraction of the fast emission decay component decreased, suggesting that the fast formation of polaron pairs (PP), localized (LP), and delocalized polarons (DP) results from higher singlet exciton states produced by the singlet fusion. The faster decay dynamics of DP and LP in the thick NFs than in thin NFs is due to the increased delocalization of DP and LP. As the interchain aggregation is weaker than intrachain aggregation, PP decays faster in thin NFs than in thick NFs. In both thin and thick NFs, although triplet (T1) excitons were barely observed with excitation at 532 nm on a nanosecond time scale, they were observed with excitation at 355 nm, showing that T1 excitons within NFs are generated mainly through the singlet fission from a higher singlet exciton state rather than through intersystem crossing.

A further insight into the adsorption mechanism of protein on hydroxyapatite by FTIR-ATR spectrometry

NASA Astrophysics Data System (ADS)

Lin, Zhongyu; Hu, Ren; Zhou, Jianzhang; Ye, Yiwen; Xu, Zhaoxi; Lin, Changjian

2017-02-01

The adsorption mechanism of bovine serum albumin (BSA) on hydroxyapatite (HA) for different time intervals has been studied by Fourier transform infrared (FTIR)-attenuated total internal reflectance (ATR) spectrometry in this paper. The difference spectra obtained in HA and BSA frequency regions demonstrate that the binding of Pdbnd O, from the phosphate (PO43 -) of HA, to the hydrogen of methyl (- CH3), methene (- CH2) and amideII (- CNH) in the protein appears to be much faster and stronger than that of the Psbnd O group. In addition, Ca2 + must serve as a key role in the interaction of BSA with HA. The binding of Ca2 + to the oxygen of the peptide bond seems to induce a significant reconformation of polypeptide backbones from β-pleated sheet to α-helix and β-turn of helical circles. This alteration seems to have been accompanied by much hydrogen of polypeptides driven to bind PO43 - and OH- of the HA actively and much -C = O and Hsbnd Nsbnd groups of the peptide bond freed from inter-chain hydrogen bonding to react on Ca2 + and combine strongly with the HA surface. This might be well expected to promote the HA biomineralization.

Engineered fluorescent proteins illuminate the bacterial periplasm

PubMed Central

Dammeyer, Thorben; Tinnefeld, Philip

2012-01-01

The bacterial periplasm is of special interest whenever cell factories are designed and engineered. Recombinantely produced proteins are targeted to the periplasmic space of Gram negative bacteria to take advantage of the authentic N-termini, disulfide bridge formation and easy accessibility for purification with less contaminating cellular proteins. The oxidizing environment of the periplasm promotes disulfide bridge formation - a prerequisite for proper folding of many proteins into their active conformation. In contrast, the most popular reporter protein in all of cell biology, Green Fluorescent Protein (GFP), remains inactive if translocated to the periplasmic space prior to folding. Here, the self-catalyzed chromophore maturation is blocked by formation of covalent oligomers via interchain disulfide bonds in the oxidizing environment. However, different protein engineering approaches addressing folding and stability of GFP resulted in improved proteins with enhanced folding properties. Recent studies describe GFP variants that are not only active if translocated in their folded form via the twin-arginine translocation (Tat) pathway, but actively fold in the periplasm following general secretory pathway (Sec) and signal recognition particle (SRP) mediated secretion. This mini-review highlights the progress that enables new insights into bacterial export and periplasmic protein organization, as well as new biotechnological applications combining the advantages of the periplasmic production and the Aequorea-based fluorescent reporter proteins. PMID:24688673

Growth control of genetically modified cells using an antibody/c-Kit chimera.

PubMed

Kaneko, Etsuji; Kawahara, Masahiro; Ueda, Hiroshi; Nagamune, Teruyuki

2012-05-01

Gene therapy has been regarded as an innovative potential treatment against serious congenital diseases. However, applications of gene therapy remain limited, partly because its clinical success depends on therapeutic gene-transduced cells acquiring a proliferative advantage. To address this problem, we have developed the antigen-mediated genetically modified cell amplification (AMEGA) system, which uses chimeric receptors to enable the selective proliferation of gene-transduced cells. In this report, we describe mimicry of c-Kit signaling and its application to the AMEGA system. We created an antibody/c-Kit chimera in which the extracellular domain of c-Kit is replaced with an anti-fluorescein single-chain Fv antibody fragment and the extracellular D2 domain of the erythropoietin receptor. A genetically modified mouse pro-B cell line carrying this chimera showed selective expansion in the presence of fluorescein-conjugated BSA (BSA-FL) as a growth inducer. By further engineering the transmembrane domain of the chimera to reduce interchain interaction we attained stricter ligand-dependency. Since c-Kit is an important molecule in the expansion of hematopoietic stem cells (HSCs), this antibody/c-Kit chimera could be a promising tool for gene therapy targeting HSCs. Copyright © 2011 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

CRYSTAL STRUCTURE OF CLOSTRIDIUM BOTULINUM NEUROTOXIN SEROTYPE B.

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

SWAMINATHAN,S.; ESWARAMOORTHY,S.

2001-11-19

The toxigenic strains of Clostridium botulinum produce seven serologically distinct types of neurotoxins labeled A - G (EC 3.4.24.69), while Clostridium tetani produces tetanus neurotoxin (EC 3.4.24.68). Botulinum and tetanus neurotoxins (BoNTs and TeNT) are produced as single inactive chains of molecular mass of approximately 150 kDa. Most of these neurotoxins are released after being cleaved into two chains, a heavy chain (HI) of 100 kDa and a light chain (L) of 50 kDa held together by an interchain disulfide bond, by tissue proteinases. BoNT/E is released as a single chain but cleaved by host proteinases [1]. Clostvidium botulinum neurotoxinsmore » are extremely poisonous proteins with their LD{sub 50} for humans in the range of 0.1 - 1 ng kg{sup -1} [2]. Botulinum neurotoxins are responsible for neuroparalytic syndromes of botulism characterized by serious neurological disorders and flaccid paralysis. BoNTs block the release of acetylcholine at the neuromuscular junction causing flaccid paralysis while TeNT blocks the release of neurotransmitters like glycine and {gamma}-aminobutyric acid (GABA) in the inhibitory interneurons of the spinal cord resulting in spastic paralysis. In spite of different clinical symptoms, their aetiological agents intoxicate neuronal cells in the same way and these toxins have similar structural organization [3].« less

Probing inter- and intrachain Zhang-Rice excitons in Li 2 CuO 2 and determining their binding energy

DOE PAGES

Monney, Claude; Bisogni, Valentina; Zhou, Ke-Jin; ...

2016-10-10

Cuprate materials, such as those hosting high-temperature superconductivity, represent a famous class of materials where the correlations between the strongly entangled charges and spins produce complex phase diagrams. Several years ago, the Zhang-Rice singlet was proposed as a natural quasiparticle in hole-doped cuprates. The occurrence and binding energy of this quasiparticle, consisting of a pair of bound holes with antiparallel spins on the same CuO 4 plaquette, depends on the local electronic interactions, which are fundamental quantities for understanding the physics of the cuprates. Here, we employ state-of-the-art resonant inelastic x-ray scattering (RIXS) to probe the correlated physics of themore » CuO 4 plaquettes in the quasi-one-dimensional chain cuprate Li 2CuO 2. By tuning the incoming photon energy to the O K edge, we populate bound states related to the Zhang-Rice quasiparticles in the RIXS process. Both intra- and interchain Zhang-Rice singlets are observed and their occurrence is shown to depend on the nearest-neighbor spin-spin correlations, which are readily probed in this experiment. Finally, we also extract the binding energy of the Zhang-Rice singlet and identify the Zhang-Rice triplet excitation in the RIXS spectra.« less

Molecular mechanism of melting of a helical polymer crystal: Role of conformational order, packing and mobility of polymers

NASA Astrophysics Data System (ADS)

Cheerla, Ramesh; Krishnan, Marimuthu

2018-03-01

The molecular mechanism of melting of a superheated helical polymer crystal has been investigated using isothermal-isobaric molecular dynamics simulation that allows anisotropic deformation of the crystal lattice. A detailed microscopic analysis of the onset and progression of melting and accompanying changes in the polymer conformational order, translational, and orientation order of the solid along the melting pathway is presented. Upon gradual heating from room temperature to beyond the melting point at ambient pressure, the crystal exhibits signatures of premelting well below the solid-to-liquid melting transition at the melting point. The melting transition is manifested by abrupt changes in the crystal volume, lattice energy, polymer conformation, and dynamical properties. In the premelting stage, the crystal lattice structure and backbone orientation of the polymer chains are retained but with the onset of weakening of long-range helical order and interchain packing of polymers perpendicular to the fibre axis of the crystal. The premelting also marks the onset of conformational defects and anisotropic solid-state diffusion of polymers along the fibre axis. The present study underscores the importance of the interplay between intermolecular packing, interactions, and conformational dynamics at the atomic level in determining the macroscopic melting behavior of polymer crystals.

Psychosocial Predictors of Life Quality: How Are They Affected by Infertility, Gender, and Parenthood?

ERIC Educational Resources Information Center

Abbey, Antonia; And Others

1994-01-01

Longitudinally examined effects of infertility on marital and global life quality with 174 infertile couples and 74 fertile couples. By third interview, 42% of infertile couples and 36% of fertile couples were parents. Psychosocial predictors of life quality were highly similar for members of infertile and fertile couples and for couples with and…

Effect of interface reaction and diffusion on stress-oxidation coupling at high temperature

NASA Astrophysics Data System (ADS)

Yue, Mengkun; Dong, Xuelin; Fang, Xufei; Feng, Xue

2018-04-01

High-temperature structural materials undergo oxidation during the service, and stress would generate in the oxide film. Understanding the coupling effect between stress and oxidation contributes to the understanding of material degradation and failure during the oxidation process. Here, we propose a model to investigative the coupling effect of stress and oxidation at high temperature by considering the three-stage oxidation process, where both the interface reaction and the diffusion process are present. The governing equations including the oxidation kinetics and stress equilibrium for isothermal oxidation under stress-oxidation coupling effect have been derived. The theory is validated by comparing with the experimental results of SiO2 grown on Si substrate. Results show that the coupling of stress and oxidation influences the growth of the oxide film by affecting all three stages of the oxidation process.

Structural Couple Therapy in the Treatment of Inhibited Sexual Drive.

ERIC Educational Resources Information Center

Fish, Linda Stone; And Others

1994-01-01

Examined structural couple therapy approach to treatment of inhibited sexual desire (ISD). Results from clinical sample of 19 couples with ISD suggest that structural couple therapy approach to ISD is effective in reducing symptoms of sexual disorder and in increasing couple satisfaction. (Author/NB)

The Numerical Simulation of Coupling Behavior of Soil with Chemical Pollutant Effects

NASA Astrophysics Data System (ADS)

Liu, Z. J.; Li, X. K.; Tang, L. Q.

2010-05-01

The coupling behavior of clay plays a role in the integrity of clay barriers used in landfills. The clay barriers are subjected to mechanical and thermal effects coupled with hydraulic behavior, also, if the leachates become in contact with the clay liner, chemical effects may lead to some drastic changes in the properties of the clay. A numerical method to simulate the coupling behavior of soil with chemical pollutant effects is presented. Within the framework of Gens-Alonso model describing the constitutive behavior of unsaturated clay presented in reference[1], basing on the work of Wu[2] and Hueckel[3], a constitutive model describing the chemo-thermo-hydro-mechanical(CTHM) coupling behavior of clays in contact with a single organic contaminant is presented. The thermical softening and chemical softening is considered in the presented model. The strain arising in the material due to chemical and thermical effects can be decomposed into two parts: elastic expansion and plastic compaction. The chemical effects are described in terms of the mass concentration of the contaminant. The increases in temperature and contaminant concentration cause decreases of the pre-consolidation pressure and the cohesion. The mechanisms are called thermical softening and chemical softening. The presented coupled CTHM constitutive model has been integrated into the coupled thermo-hydro-mechanical mathematical model including contaminant transport in porous media. To solve the equilibrium equations, the grogram of finite element methods is developed with a stagger algorithm. The mechanisms taking place due to the coupling behaviour of the clay with a single contaminant solute are analysed with the presented numerical method.

Effectiveness of the 'Hold me Tight' Relationship Enhancement Program in a Self-referred and a Clinician-referred Sample: An Emotionally Focused Couples Therapy-Based Approach.

PubMed

Conradi, Henk Jan; Dingemanse, Pieter; Noordhof, Arjen; Finkenauer, Catrin; Kamphuis, Jan H

2017-09-04

While evidence-based couple therapies are available, only a minority of troubled couples seek help and they often do this too late. To reach more couples earlier, the couple relationship education (CRE) group program "Hold me Tight" (HmT) based on Emotionally Focused Couples Therapy (EFCT) was developed. This study is the first to examine the effectiveness of HmT. Using a three-wave (waiting period, treatment, and follow-up) within-subject design, HmT was delivered to 79 self-referred couples and 50 clinician-referred couples. We applied a comprehensive outcome measure battery. Our main findings were that (1) self-referred couples significantly improved during HmT on all measures, that is relationship satisfaction, security of partner-bond, forgiveness, daily coordination, maintenance behavior, and psychological complaints, with a moderate-to-large mean effect size (d = .63), which was maintained (d = .57) during the 3.5 month follow-up; (2) in clinician-referred couples, who were vulnerable in terms of insecure attachment status and psychopathology, the improvement during HmT was moderate (d = .42), but this was reduced during the 3.5-month follow-up to a small effect (d = .22); (3) emotional functioning (typical HmT target) as well as behavioral functioning (typical Behavioral Couples Therapy-based CRE target) improved during HmT; and (4) individual psychological complaints, although not specifically targeted, were reduced during HmT. These findings suggest that HmT is a promising intervention for enhancement of relationship functioning. Clinical implications are discussed. © 2017 Family Process Institute.

The bright-bright and bright-dark mode coupling-based planar metamaterial for plasmonic EIT-like effect

NASA Astrophysics Data System (ADS)

Yu, Wei; Meng, Hongyun; Chen, Zhangjie; Li, Xianping; Zhang, Xing; Wang, Faqiang; Wei, Zhongchao; Tan, Chunhua; Huang, Xuguang; Li, Shuti

2018-05-01

In this paper, we propose a novel planar metamaterial structure for the electromagnetically induced transparency (EIT)-like effect, which consists of a split-ring resonator (SRR) and a pair of metal strips. The simulated results indicate that a single transparency window can be realized in the symmetry situation, which originates from the bright-bright mode coupling. Further, a dual-band EIT-like effect can be achieved in the asymmetry situation, which is due to the bright-bright mode coupling and bright-dark mode coupling, respectively. Different EIT-like effect can be simultaneously achieved in the proposed structure with the different situations. It is of certain significance for the study of EIT-like effect.

The psychological effects of work experiences and disagreements about gender role beliefs in dual-earner couples: a longitudinal study.

PubMed

James, J B; Barnett, R C; Brennan, R T

1998-01-01

Using an economically diverse random sample of 300 full-time employed men and women in dual-earner couples from two communities in the Northeast, we estimated the relation between the direction and magnitude of disagreement about gender role ideology (GRI) within couples and psychological distress. We conceptualized GRI within couples as both the couple mean or stable gender-role ideology (the "couple ideology") and as each partner's deviation from the other partner's score. Moreover, for each partner, we estimated the relation between both the stable (i.e., mean) component and the change (i.e., time-varying) component of GRI and distress. Finally, for each partner we estimated the moderating effect of GRI on the relation between job-role quality and distress. Findings are: (a) the more egalitarian the husband's average GRI is relative to his wife's, the less distressed he is; (b) if over time a wife's GRI becomes less egalitarian relative to her husband's, then her distress will be more affected by changes in her job-role quality; (c) for husbands, as the couple's average GRI becomes more egalitarian over time, the effect of job-role quality on distress is lessened; and (d) for a man in a couple with a more egalitarian stable GRI, the effects of change in job-role quality on distress are less pronounced than for a man in a couple with a less egalitarian stable GRI. Results are discussed in terms of new conceptions of GRI revealing the dynamic interaction of within-couples' gender-role ideologies.

Communication: Localized molecular orbital analysis of the effect of electron correlation on the anomalous isotope effect in the NMR spin-spin coupling constant in methane

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

Zarycz, M. Natalia C., E-mail: mnzarycz@gmail.com; Provasi, Patricio F., E-mail: patricio@unne.edu.ar; Sauer, Stephan P. A., E-mail: sauer@kiku.dk

2014-10-21

We discuss the effect of electron correlation on the unexpected differential sensitivity (UDS) in the {sup 1}J(C–H) coupling constant of CH{sub 4} using a decomposition into contributions from localized molecular orbitals and compare with the {sup 1}J(N–H) coupling constant in NH{sub 3}. In particular, we discuss the well known fact that uncorrelated coupled Hartree-Fock (CHF) calculations are not able to reproduce the UDS in methane. For this purpose we have implemented for the first time a localized molecular orbital analysis for the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes—SOPPA(CCSD) in the DALTON program. Comparing themore » changes in the localized orbital contributions at the correlated SOPPA and SOPPA(CCSD) levels and at the uncorrelated CHF level, we find that the latter overestimates the effect of stretching the bond between the coupled atoms on the contribution to the coupling from the localized bonding orbital between these atoms. This disturbs the subtle balance between the molecular orbital contributions, which lead to the UDS in methane.« less

Effects of Coulomb Coupling on the Stopping Power of Plasmas

NASA Astrophysics Data System (ADS)

Bernstein, David; Daligault, Jerome; Baalrud, Scott

2017-10-01

Stopping power of charged particles in plasma is important for a detailed understanding of particle and energy transport in plasmas, such as those found in fusion applications. Although stopping power is rather well understood for weakly coupled plasmas, this is less the case for strongly coupled plasmas. In order to shed light on the effects of strong Coulomb coupling, we have conducted detailed molecular dynamics simulations of the stopping power of a One-Component Plasma (OCP) across a wide range of conditions. The OCP allows first-principle computations that are not possible with more complex models, enabling rigorous tests of analytical theories. The molecular dynamics simulations were compared to two analytical theories that attempt to extend traditional weakly-coupled theories into the strong coupling regime. The first is based on the binary approximation, which accounts for strong coupling via an effective scattering cross section derived from the effective potential theory. The second is based on the dielectric function formulation with the inclusion of a local field corrections. Work supported by LANL LDRD project 20150520ER and ir Force Office of Scientific Research under Award Number FA9550-16-1-0221.

Homework assignments in couple and family therapy.

PubMed

Dattilio, Frank M

2002-05-01

Homework has been cited as an integral part of a number of theoretical orientations and therapy formats; unfortunately, very little has been written about its use with couples and families. This is despite the fact that many couple and family therapists espouse the use of homework or out-of-session assignments in order to help the effects of therapy jell. This article reviews some of the empirical literature on homework assignments and their effectiveness in the domain of therapy for families and couples. It also highlights the effectiveness of and the need for out-of-session assignments in treatment. A case illustration is used to demonstrate how homework assignments may be used as a significant change agent in couple and family treatment. Copyright 2002 Wiley Periodicals, Inc.

Bang-bang control of a qubit coupled to a quantum critical spin bath

NASA Astrophysics Data System (ADS)

Rossini, D.; Facchi, P.; Fazio, R.; Florio, G.; Lidar, D. A.; Pascazio, S.; Plastina, F.; Zanardi, P.

2008-05-01

We analytically and numerically study the effects of pulsed control on the decoherence of a qubit coupled to a quantum spin bath. When the environment is critical, decoherence is faster and we show that the control is relatively more effective. Two coupling models are investigated, namely, a qubit coupled to a bath via a single link and a spin-star model, yielding results that are similar and consistent.

Zero-point fluctuations in naphthalene and their effect on charge transport parameters.

PubMed

Kwiatkowski, Joe J; Frost, Jarvist M; Kirkpatrick, James; Nelson, Jenny

2008-09-25

We calculate the effect of vibronic coupling on the charge transport parameters in crystalline naphthalene, between 0 and 400 K. We find that nuclear fluctuations can cause large changes in both the energy of a charge on a molecule and on the electronic coupling between molecules. As a result, nuclear fluctuations cause wide distributions of both energies and couplings. We show that these distributions have a small temperature dependence and that, even at high temperatures, vibronic coupling is dominated by the effect of zero-point fluctuations. Because of the importance of zero-point fluctuations, we find that the distributions of energies and couplings have substantial width, even at 0 K. Furthermore, vibronic coupling with high energy modes may be significant, even though these modes are never thermally activated. Our results have implications for the temperature dependence of charge mobilities in organic semiconductors.

Effects of modal truncation and condensation methods on the Frequency Response Function of a stage reducer connected by rigid coupling to a planetary gear system

NASA Astrophysics Data System (ADS)

Bouslema, Marwa; Frikha, Ahmed; Abdennadhar, Moez; Fakhfakh, Tahar; Nasri, Rachid; Haddar, Mohamed

2017-12-01

The present paper is aimed at the application of a substructure methodology, based on the Frequency Response Function (FRF) simulation technique, to analyze the vibration of a stage reducer connected by a rigid coupling to a planetary gear system. The computation of the vibration response was achieved using the FRF-based substructuring method. First of all, the two subsystems were analyzed separately and their FRF were obtained. Then the coupled model was analyzed indirectly using the substructuring technique. A comparison between the full system response and the coupled model response using the FRF substructuring was investigated to validate the coupling method. Furthermore, a parametric study of the effect of the shaft coupling stiffness on the FRF was discussed and the effects of modal truncation and condensation methods on the FRF of subsystems were analyzed.

Comparison of internet and mailing methods to recruit couples into research on unaided smoking cessation.

PubMed

Derrick, Jaye L; Eliseo-Arras, Rebecca K; Hanny, Courtney; Britton, Maggie; Haddad, Sana

2017-12-01

In smoking cessation studies with restrictive criteria (e.g., single-smoker couples), thousands of potential participants might need to be screened to obtain a reasonable sample size. Consideration of recruitment methodology is critical because recruitment methods influence both the success and cost effectiveness of recruitment. Although traditional recruitment methods are often used to recruit participants into smoking cessation research, newer technologies, such as paid Facebook advertising, might offer more cost-effective alternatives for recruitment. The current analysis compares two versions of paid Facebook advertising and a specialized mass mailing method used to recruit single-smoker couples into an intensive three-week study of unaided smoking cessation. The three methods are compared in terms of demographic characteristics, eligibility, and cost-effectiveness. Although Facebook's "Promote Your Page" mechanism achieved the fastest recruitment rate (2.75 couples per month; 498 USD per couple), Facebook's "Send People to Your Website" mechanism was the least expensive and provided the most demographically diverse sample (1.64 couples per month; 181 USD per couple). The specialized mailing method was not productive or cost-effective (0.80 couples per month; 454 USD per couple). Paid Facebook advertising fared better as a recruitment method than a specialized mailing method often used in survey research. Studies that have less restrictive eligibility criteria, that draw from a larger local population, or that recruit for a less intense study might find paid Facebook advertising to be quite feasible. Copyright © 2017 Elsevier Ltd. All rights reserved.

Asymptotics of QCD traveling waves with fluctuations and running coupling effects

NASA Astrophysics Data System (ADS)

Beuf, Guillaume

2008-09-01

Extending the Balitsky-Kovchegov (BK) equation independently to running coupling or to fluctuation effects due to pomeron loops is known to lead in both cases to qualitative changes of the traveling-wave asymptotic solutions. In this paper we study the extension of the forward BK equation, including both running coupling and fluctuations effects, extending the method developed for the fixed coupling case [E. Brunet, B. Derrida, A.H. Mueller, S. Munier, Phys. Rev. E 73 (2006) 056126, cond-mat/0512021]. We derive the exact asymptotic behavior in rapidity of the probabilistic distribution of the saturation scale.

Effects of the electron-phonon coupling activation in collision cascades

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

Zarkadoula, Eva; Samolyuk, German; Weber, William J.

Using the two-temperature (2T-MD) model in molecular dynamics simulations, here we investigate the condition of switching the electronic stopping term off when the electron-phonon coupling is activated in the damage production due to 50 keV Ni ion cascades in Ni and equiatomic NiFe. Additionally we investigate the effect of the electron-phonon coupling activation time in the damage production. We find that the switching condition has negligible effect in the produced damage, while the choice of the activation time of the electron-phonon coupling can affect the amount of surviving damage.

Experimental investigation of yawing-rolling coupling effects on unsteady aerodynamic characteristics of an aircraft

NASA Astrophysics Data System (ADS)

Shen, Lin; Huang, Da; Wu, Genxing

2018-05-01

In this paper, an aircraft model was tested in the wind tunnel with different degrees of yaw-roll coupling at different angles of attack. The dynamic increments of yawing and rolling moments are compared to study the coupling effects on damping characteristics. The characteristic time constants are calculated to study the changes of flow field structure related to coupling ratios. The damping characteristics and time lag effects of aerodynamic loads calculated by dynamic derivative method are also compared with experimental results to estimate the applicability of linear superposition principle at large angles of attack.

Effects of the electron-phonon coupling activation in collision cascades

DOE PAGES

Zarkadoula, Eva; Samolyuk, German; Weber, William J.

2017-04-20

Using the two-temperature (2T-MD) model in molecular dynamics simulations, here we investigate the condition of switching the electronic stopping term off when the electron-phonon coupling is activated in the damage production due to 50 keV Ni ion cascades in Ni and equiatomic NiFe. Additionally we investigate the effect of the electron-phonon coupling activation time in the damage production. We find that the switching condition has negligible effect in the produced damage, while the choice of the activation time of the electron-phonon coupling can affect the amount of surviving damage.

Eddy-current effect on resonant magnetoelectric coupling in magnetostrictive-piezoelectric laminated composites

NASA Astrophysics Data System (ADS)

Liu, Guoxi; Zhang, Chunli; Chen, Weiqiu; Dong, Shuxiang

2013-07-01

An analytical model of resonant magnetoelectric (ME) coupling in magnetostrictive (MS)-piezoelectric (PE) laminated composites in consideration of eddy-current effect in MS layer using equivalent circuit method is presented. Numerical calculations show that: (1) the eddy-current has a strong effect on ME coupling in MS-PE laminated composites at resonant frequency; and (2) the resonant ME coupling is then significantly dependent on the sizes of ME laminated composites, which were neglected in most previous theoretical analyses. The achieved results provide a theoretical guidance for the practice engineering design, manufacture, and application of ME laminated composites and devices.

Effect of Coriolis coupling in chemical reaction dynamics.

PubMed

Chu, Tian-Shu; Han, Ke-Li

2008-05-14

It is essential to evaluate the role of Coriolis coupling effect in molecular reaction dynamics. Here we consider Coriolis coupling effect in quantum reactive scattering calculations in the context of both adiabaticity and nonadiabaticity, with particular emphasis on examining the role of Coriolis coupling effect in reaction dynamics of triatomic molecular systems. We present the results of our own calculations by the time-dependent quantum wave packet approach for H + D2 and F(2P3/2,2P1/2) + H2 as well as for the ion-molecule collisions of He + H2 +, D(-) + H2, H(-) + D2, and D+ + H2, after reviewing in detail other related research efforts on this issue.

Coupled mode effects on energy transfer in weakly coupled, two-temperature plasmas

NASA Astrophysics Data System (ADS)

Vorberger, J.; Gericke, D. O.

2009-08-01

The effects of collective modes on the temperature relaxation in fully ionized, weakly coupled plasmas are investigated. A coupled mode (CM) formula for the electron-ion energy transfer is derived within the random phase approximation and it is shown how it can be evaluated using standard methods. The CM rates are considerably smaller than rates based on Fermi's golden rule for some parameters and identical for others. It is shown how the CM effects are connected to the occurrence of ion acoustic modes and when they occur. Interestingly, CM effects occur also for plasmas with very high electron temperatures; a regime, where the Landau-Spitzer approach is believed to be accurate.

Coupling effects for separate spatial solitons in a biased series centrosymmetric photorefractive crystal circuit considering grey solitons

NASA Astrophysics Data System (ADS)

Katti, Aavishkar; Yadav, Ram Anjore

2018-02-01

The existence and coupling of grey-grey, grey-bright and grey-dark separate spatial solitons in a biased series centrosymmetric photorefractive crystal circuit is investigated for the first time. The numerical solution of the separate spatial solitons is presented. The coupling between the two separate spatial solitons is analysed for all three cases of separate coupled solitons, namely grey-grey, grey-bright, and grey-dark. Changing the intensity of the soliton in one crystal affects the soliton in both crystals due to flow of the light induced current through the circuit. The effect of the background intensity of each crystal on both the spatial solitons is investigated. Also, the effect of changing the temperature of one crystal affects the soliton in both crystals due to the coupling effect. The soliton width dependence on the temperature is different for each crystal.

Current in nanojunctions: Effects of reservoir coupling

NASA Astrophysics Data System (ADS)

Yadalam, Hari Kumar; Harbola, Upendra

2018-07-01

We study the effect of system reservoir coupling on currents flowing through quantum junctions. We consider two simple double-quantum dot configurations coupled to two external fermionic reservoirs and study the net current flowing between the two reservoirs. The net current is partitioned into currents carried by the eigenstates of the system and by the coherences between the eigenstates induced due to coupling with the reservoirs. We find that current carried by populations is always positive whereas current carried by coherences are negative for large couplings. This results in a non-monotonic dependence of the net current on the coupling strength. We find that in certain cases, the net current can vanish at large couplings due to cancellation between currents carried by the eigenstates and by the coherences. These results provide new insights into the non-trivial role of system-reservoir couplings on electron transport through quantum dot junctions. In the presence of weak coulomb interactions, net current as a function of system reservoir coupling strength shows similar trends as for the non-interacting case.

Synchronization of coupled active rotators by common noise

NASA Astrophysics Data System (ADS)

Dolmatova, Anastasiya V.; Goldobin, Denis S.; Pikovsky, Arkady

2017-12-01

We study the effect of common noise on coupled active rotators. While such a noise always facilitates synchrony, coupling may be attractive (synchronizing) or repulsive (desynchronizing). We develop an analytical approach based on a transformation to approximate angle-action variables and averaging over fast rotations. For identical rotators, we describe a transition from full to partial synchrony at a critical value of repulsive coupling. For nonidentical rotators, the most nontrivial effect occurs at moderate repulsive coupling, where a juxtaposition of phase locking with frequency repulsion (anti-entrainment) is observed. We show that the frequency repulsion obeys a nontrivial power law.

Electrical Tuning of Exciton-Plasmon Polariton Coupling in Monolayer MoS2 Integrated with Plasmonic Nanoantenna Lattice.

PubMed

Lee, Bumsu; Liu, Wenjing; Naylor, Carl H; Park, Joohee; Malek, Stephanie C; Berger, Jacob S; Johnson, A T Charlie; Agarwal, Ritesh

2017-07-12

Active control of light-matter interactions in semiconductors is critical for realizing next generation optoelectronic devices with real-time control of the system's optical properties and hence functionalities via external fields. The ability to dynamically manipulate optical interactions by applied fields in active materials coupled to cavities with fixed geometrical parameters opens up possibilities of controlling the lifetimes, oscillator strengths, effective mass, and relaxation properties of a coupled exciton-photon (or plasmon) system. Here, we demonstrate electrical control of exciton-plasmon coupling strengths between strong and weak coupling limits in a two-dimensional semiconductor integrated with plasmonic nanoresonators assembled in a field-effect transistor device by electrostatic doping. As a result, the energy-momentum dispersions of such an exciton-plasmon coupled system can be altered dynamically with applied electric field by modulating the excitonic properties of monolayer MoS 2 arising from many-body effects. In addition, evidence of enhanced coupling between charged excitons (trions) and plasmons was also observed upon increased carrier injection, which can be utilized for fabricating Fermionic polaritonic and magnetoplasmonic devices. The ability to dynamically control the optical properties of a coupled exciton-plasmonic system with electric fields demonstrates the versatility of the coupled system and offers a new platform for the design of optoelectronic devices with precisely tailored responses.

Reactions to framing of cessation messages: insights from dual-smoker couples.

PubMed

Lipkus, Isaac M; Ranby, Krista W; Lewis, Megan A; Toll, Benjamin

2013-12-01

Couples in which both members smoke (dual-smoker couples) have not been the explicit target of cessation interventions. Quit rates are lower and relapse rates are higher among individuals in dual-smoker couples. A potentially effective strategy to motivate dual-smoker couples to quit is to convey messages that highlight how the positive outcomes of quitting (gain frame) or the negative outcomes of continued smoking (loss frame) affect the couple rather than the individual smoker. We explored whether dual-smoker couples' smoking behaviors (e.g., amount smoked) and desire to quit would differ as a function of message frame (gain vs. loss) or outcome focus (individual vs. couple). Dual-smoker couples (N = 40) completed a baseline survey and were then randomized to review gain- or loss-framed messages that varied whether the outcomes influenced the individual or the couple. Main outcomes were desire to quit after reading messages and smoking behaviors at a 1-month follow-up. Couple-focused messages produced the strongest desire to quit and decreased amount of cigarettes smoked at follow-up. The latter effect was mediated by desire to quit. Loss-framed messages produced inconsistent effects on desire to quit. There were no significant interactions between outcome focus and message framing. Findings suggest that messages emphasizing how smoking affects both partners can motivate cessation among dual-smoker couples. Contrary to findings showing that gain-framed messages motivate cessation targeting individual smokers, results suggest that loss-framed messages may be more persuasive than gain-framed messages when the target of the outcome involves significant others.

Impact of vegetation on land-atmosphere coupling strength and its implication for desertification mitigation over East Asia

NASA Astrophysics Data System (ADS)

Myoung, Boksoon; Choi, Yong-Sang; Choi, Suk-Jin; Park, Seon Ki

2012-06-01

Desertification of the East Asian drylands and the consequent dust transport have been serious concerns for adjacent Asian countries as well as the western United States. Tree planting has been considered one applicable strategy to mitigate the desertification. However, the desired effect of the tree planting would not be brought to fruition unless the newly planted trees change the coupling characteristics between the land and the atmosphere. Based on this perception, we attempt to clarify the effects of vegetation on the coupling strength between the atmosphere and land surface, and we suggest the most efficient areas of tree planting for desertification mitigation in East Asia. Using regional vegetation-atmosphere coupled model simulations, coupling strength with and without vegetation was computed and compared with each other. An increased vegetation fraction reduces the coupling strength in June, July, and August (JJA), primarily due to decreased evapotranspiration variability. This effect is pronounced over the Manchurian Plains and the highly populated areas of Beijing and Tianjin. The reduced coupling strength tends to weaken feedback between soil moisture and precipitation as a maintenance mechanism of warm season droughts in the midlatitudes and subsequently decrease the probability of droughts, a finding that is reflected in the enhanced JJA mean soil moisture. However, some drylands like the eastern edges of the Gobi desert present marginal or even opposite changes in coupling strength, meaning a limited effect of vegetation on relieving droughts. Therefore, given limited financial and human resources, acupuncture-like afforestation, i.e., concentrated tree planting in a particular region where the coupling strength can be substantially reduced by vegetation, is an effective strategy to secure long-standing desertification mitigation.

Couples with Intimate Partner Violence Seeking Relationship Help: Associations and Implications for Self-Help and Online Interventions.

PubMed

Roddy, McKenzie K; Georgia, Emily J; Doss, Brian D

2017-04-20

In-person conjoint treatments for relationship distress are effective at increasing relationship satisfaction, and newly developed online programs are showing promising results. However, couples reporting even low levels intimate partner violence (IPV) are traditionally excluded from these interventions. To improve the availability of couple-based treatment for couples with IPV, the present study sought to determine whether associations with IPV found in community samples generalized to couples seeking help for their relationship and whether web-based interventions for relationship distressed worked equally well for couples with IPV. In the first aim, in a sample of 2,797 individuals who were seeking online help for their relationship, the levels and correlates of both low-intensity and clinically significant IPV largely matched what is found in community samples. In the second aim, in a sample of 300 couples who were randomly assigned to a web-based intervention or a waitlist control group, low-impact IPV did not moderate the effects of the intervention for relationship distress. Therefore, web-based interventions may be an effective (and easily accessible) intervention for relationship distress for couples with low-intensity IPV. © 2017 Family Process Institute.

Optomechanical coupling in phoxonic–plasmonic slab cavities with periodic metal strips

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

Lin, Tzy-Rong; Institute of Optoelectronic Sciences, National Taiwan Ocean University, Keelung 20224, Taiwan; Huang, Yin-Chen

2015-05-07

We theoretically investigate the optomechanical (OM) coupling of submicron cavities formed in one-dimensional phoxonic–plasmonic slabs. The phoxonic–plasmonic slabs are structured by depositing periodic Ag strips onto the top surfaces of dielectric GaAs slabs to produce dual band gaps for both electromagnetic and acoustic waves, thereby inducing the coupling of surface plasmons with photons for tailoring the OM coupling. We quantify the OM coupling by calculating the temporal modulation of the optical resonance wavelength with the acoustic phonon-induced photoelastic (PE) and moving-boundary (MB) effects. We also consider the appearance of a uniform Ag layer on the bottom surface of the slabsmore » to modulate the photonic–plasmonic coupling. The results show that the PE and MB effects can be constructive or destructive in the overall OM coupling, and their magnitudes depend not only on the quality factors of the resonant modes but also on the mode area, mode overlap, and individual symmetries of the photonic–phononic mode pairs. Lowering the mode area could be effective for enhancing the OM coupling of subwavelength photons and phonons. This study introduces possible engineering applications to achieve enhanced interaction between photons and phonons in nanoscale OM devices.« less

A Simple Model for Fine Structure Transitions in Alkali-Metal Noble-Gas Collisions

DTIC Science & Technology

2015-03-01

63 33 Effect of Scaling the VRG(R) Radial Coupling Fit Parameter, V0, for KHe, KNe, and KAr...64 ix Figure Page 34 Effect of Scaling the VRG(R) Radial Coupling Fit Parameter, V0, for RbHe, RbNe, and...RbAr . . . . . . . . . . . . . . . . . . . . . . . . . 64 35 Effect of Scaling the VRG(R) Radial Coupling Fit Parameter, V0, for CsHe, CsNe, and CsAr

The Effectiveness of PREP with Lower-Income Racial/Ethnic Minority Couples

ERIC Educational Resources Information Center

Owen, Jesse; Quirk, Kelley; Bergen, Carrie; Inch, Leslie J.; France, Tiffany

2012-01-01

The current study examined the effectiveness of the Prevention and Relationship Enhancement Program (PREP) with lower-income and racial/ethnic minority (African American and Latino/a) couples. Additionally, we tested whether relationship outcomes varied based on the delivery format (i.e., group format vs. couple format). The sample included 321…

Nonlinear vibrations analysis of rotating drum-disk coupling structure

NASA Astrophysics Data System (ADS)

Chaofeng, Li; Boqing, Miao; Qiansheng, Tang; Chenyang, Xi; Bangchun, Wen

2018-04-01

A dynamic model of a coupled rotating drum-disk system with elastic support is developed in this paper. By considering the effects of centrifugal and Coriolis forces as well as rotation-induced hoop stress, the governing differential equation of the drum-disk is derived by Donnell's shell theory. The nonlinear amplitude-frequency characteristics of coupled structure are studied. The results indicate that the natural characteristics of the coupling structure are sensitive to the supporting stiffness of the disk, and the sensitive range is affected by rotating speeds. The circumferential wave numbers can affect the characteristics of the drum-disk structure. If the circumferential wave number n = 1 , the vibration response of the drum keeps a stable value under an unbalanced load of the disk, there is no coupling effect if n ≠ 1 . Under the excitation, the nonlinear hardening characteristics of the forward traveling wave are more evident than that of the backward traveling wave. Moreover, because of the coupling effect of the drum and the disk, the supporting stiffness of the disk has certain effect on the nonlinear characteristics of the forward and backward traveling waves. In addition, small length-radius and thickness-radius ratios have a significant effect on the nonlinear characteristics of the coupled structure, which means nonlinear shell theory should be adopted to design rotating drum's parameter for its specific structural parameters.

Honey, I got fired! A longitudinal dyadic analysis of the effect of unemployment on life satisfaction in couples.

PubMed

Luhmann, Maike; Weiss, Pola; Hosoya, Georg; Eid, Michael

2014-07-01

Previous research on unemployment and life satisfaction has focused on the effects of unemployment on individuals but neglected the effects on their partners. In the present study, we used dyadic multilevel models to analyze longitudinal data from 2,973 couples selected from a German representative panel study to examine the effects of unemployment on life satisfaction in couples over several years. We found that unemployment decreases life satisfaction in both members of the couple, but the effect is more pronounced for those who become unemployed (actors) than for the other couple members (partners). In both couple members, the reaction is attenuated if they share the same labor status after the job loss: Actors experienced a greater drop in life satisfaction if their partners were employed than if they were unemployed at the time of the job loss, and partners reacted negatively to the job loss only if they were employed or inactive in the workforce, but not if they were unemployed themselves. With respect to couple-level moderator variables, we found that both actors and partners reacted more negatively to unemployment if they had children. The reaction was also more negative in male actors than in female actors, but there was no difference between male and female partners. In sum, these findings indicate that changes in life satisfaction can be caused by major life events experienced by significant others.

Inversed Vernier effect based single-mode laser emission in coupled microdisks

PubMed Central

Li, Meng; Zhang, Nan; Wang, Kaiyang; Li, Jiankai; Xiao, Shumin; Song, Qinghai

2015-01-01

Recently, on-chip single-mode laser emissions in coupled microdisks have attracted considerable research attention due to their wide applications. While most of single-mode lasers in coupled microdisks or microrings have been qualitatively explained by either Vernier effect or inversed Vernier effect, none of them have been experimentally confirmed. Here, we studied the mechanism of single-mode laser operation in coupled microdisks. We found that the mode numbers had been significantly reduced to nearly single-mode within a large pumping power range from threshold to gain saturation. The detail laser spectra showed that the largest gain and the first lasing peak were mainly generated by one disk and the laser intensity was proportional to the wavelength detuning of two set of modes. The corresponding theoretical analysis showed that the experimental observations were dominated by internal coupling within one cavity, which was similar to the recently explored inversed Vernier effect in two coupled microrings. We believe our finding will be important for understanding the previous experimental findings and the development of on-chip single-mode laser. PMID:26330218

Interfacial thermal transport with strong system-bath coupling: A phonon delocalization effect

NASA Astrophysics Data System (ADS)

He, Dahai; Thingna, Juzar; Cao, Jianshu

2018-05-01

We study the effect of system-bath coupling strength on quantum thermal transport through the interface of two weakly coupled anharmonic molecular chains by using a quantum self-consistent phonon approach. The approach inherently assumes that the two segments (anharmonic molecular chains) are approximately in local thermal equilibrium with respect to the baths that they are connected to and transforms the strongly anharmonic system into an effective harmonic one with a temperature-dependent transmission. Despite the approximations, the approach is ideal for our setup, wherein the weak interfacial coupling guarantees an approximate local thermal equilibrium of each segment and short chain length (less than the phonon mean-free path) ensues from the effective harmonic approximation. Remarkably, the heat current shows a resonant to bi-resonant transition due to the variations in the interfacial coupling and temperature, which is attributed to the delocalization of phonon modes. Delocalization occurs only in the strong system-bath coupling regime and we utilize it to model a thermal rectifier whose ratio can be nonmonotonically tuned not only with the intrinsic system parameters but also with the external temperature.

Autaptic effects on synchrony of neurons coupled by electrical synapses

NASA Astrophysics Data System (ADS)

Kim, Youngtae

2017-07-01

In this paper, we numerically study the effects of a special synapse known as autapse on synchronization of population of Morris-Lecar (ML) neurons coupled by electrical synapses. Several configurations of the ML neuronal populations such as a pair or a ring or a globally coupled network with and without autapses are examined. While most of the papers on the autaptic effects on synchronization have used networks of neurons of same spiking rate, we use the network of neurons of different spiking rates. We find that the optimal autaptic coupling strength and the autaptic time delay enhance synchronization in our neural networks. We use the phase response curve analysis to explain the enhanced synchronization by autapses. Our findings reveal the important relationship between the intraneuronal feedback loop and the interneuronal coupling.

Excitement and synchronization of small-world neuronal networks with short-term synaptic plasticity.

PubMed

Han, Fang; Wiercigroch, Marian; Fang, Jian-An; Wang, Zhijie

2011-10-01

Excitement and synchronization of electrically and chemically coupled Newman-Watts (NW) small-world neuronal networks with a short-term synaptic plasticity described by a modified Oja learning rule are investigated. For each type of neuronal network, the variation properties of synaptic weights are examined first. Then the effects of the learning rate, the coupling strength and the shortcut-adding probability on excitement and synchronization of the neuronal network are studied. It is shown that the synaptic learning suppresses the over-excitement, helps synchronization for the electrically coupled network but impairs synchronization for the chemically coupled one. Both the introduction of shortcuts and the increase of the coupling strength improve synchronization and they are helpful in increasing the excitement for the chemically coupled network, but have little effect on the excitement of the electrically coupled one.

Effects on Calculated Half-Widths and Shifts from the Line Coupling for Asymmetric-Top Molecules

NASA Technical Reports Server (NTRS)

Ma, Q.; Boulet, C.; Tipping, R. H.

2014-01-01

The refinement of the Robert-Bonamy formalism by considering the line coupling for linear molecules developed in our previous studies [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013); 140, 104304 (2014)] have been extended to asymmetric-top molecules. For H2O immersed in N2 bath, the line coupling selection rules applicable for the pure rotational band to determine whether two specified lines are coupled or not are established. Meanwhile, because the coupling strengths are determined by relative importance of off-diagonal matrix elements versus diagonal elements of the operator -iS1 -S2, quantitative tools are developed with which one is able to remove weakly coupled lines from consideration. By applying these tools, we have found that within reasonable tolerances, most of the H2O lines in the pure rotational band are not coupled. This reflects the fact that differences of energy levels of the H2O states are pretty large. But, there are several dozen strongly coupled lines and they can be categorized into different groups such that the line couplings occur only within the same groups. In practice, to identify those strongly coupled lines and to confine them into sub-linespaces are crucial steps in considering the line coupling. We have calculated half-widths and shifts for some groups, including the line coupling. Based on these calculations, one can conclude that for most of the H2O lines, it is unnecessary to consider the line coupling. However, for several dozens of lines, effects on the calculated half-widths from the line coupling are small, but remain noticeable and reductions of calculated half-widths due to including the line coupling could reach to 5%. Meanwhile, effects on the calculated shifts are very significant and variations of calculated shifts could be as large as 25%.

Effects on calculated half-widths and shifts from the line coupling for asymmetric-top molecules

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

Ma, Q.; Boulet, C.; Tipping, R. H.

2014-06-28

The refinement of the Robert-Bonamy formalism by considering the line coupling for linear molecules developed in our previous studies [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013); 140, 104304 (2014)] have been extended to asymmetric-top molecules. For H{sub 2}O immersed in N{sub 2} bath, the line coupling selection rules applicable for the pure rotational band to determine whether two specified lines are coupled or not are established. Meanwhile, because the coupling strengths are determined by relative importance of off-diagonal matrix elements versus diagonal elements of the operator −iS{sub 1} − S{sub 2}, quantitative toolsmore » are developed with which one is able to remove weakly coupled lines from consideration. By applying these tools, we have found that within reasonable tolerances, most of the H{sub 2}O lines in the pure rotational band are not coupled. This reflects the fact that differences of energy levels of the H{sub 2}O states are pretty large. But, there are several dozen strongly coupled lines and they can be categorized into different groups such that the line couplings occur only within the same groups. In practice, to identify those strongly coupled lines and to confine them into sub-linespaces are crucial steps in considering the line coupling. We have calculated half-widths and shifts for some groups, including the line coupling. Based on these calculations, one can conclude that for most of the H{sub 2}O lines, it is unnecessary to consider the line coupling. However, for several dozens of lines, effects on the calculated half-widths from the line coupling are small, but remain noticeable and reductions of calculated half-widths due to including the line coupling could reach to 5%. Meanwhile, effects on the calculated shifts are very significant and variations of calculated shifts could be as large as 25%.« less

More mental health problems after divorce in couples with high pre-divorce alcohol consumption than in other divorced couples: results from the HUNT-study

PubMed Central

2013-01-01

Background Divorce is associated with mental health problems, and heavy drinking is related to higher risk of divorce. Less is known about the effects of divorce in couples where one or both drinks heavily. There are, however, reasons to expect different consequences of divorce in heavy risk using couples compared to other couples. Spouses of abusers may experience the divorce as a relief, whereas abusers may find it extra difficult to be left single. The aim of the study is to compare the effect of divorce on mental health in heavy drinking couples to the effect in couples who drink less. Methods Registry data were matched with data from the Nord-Trøndelag Health Study (HUNT 1 (T1) and 2 (T2)), enabling longitudinal analyses of approximately 11,000 couples. Interaction terms between 1) alcohol use on T1 and divorce between T1 and T2 (11 year time lag), and 2) alcohol use on T1 and time since divorce at T2 for all divorced couples were tested to examine changes in mental health between T1 and T2 for a) spouses of high-risk compared to low-risk users, and b) high-risk compared to low-risk users themselves. Data were analyzed using multivariate analysis of variance. Results There was a general effect of divorce on change in mental health between T1 and T2. We observed a significantly stronger worsening in mental health in female high-risk users and their spouses than in divorced low-risk users and their spouses. The results also suggest that the strain after divorce lasts longer in women with a high alcohol consumption and their spouses. Conclusions Divorce seems to affect couples where one or both drink heavily more than couples with a low consumption. Also there was some evidence of a slower healing of mental health problems after divorce in alcohol exposed couples than in other couples. The results only reached significance for female high consumers and their spouses, but due to limited statistical power, safe conclusions about gender specific effects cannot be drawn. PMID:24040831

The Consequences of Spin-Orbit Coupling on the 5d3 Electronic Configuration

NASA Astrophysics Data System (ADS)

Christianson, A. D.

The impact of spin-orbit coupling on collective properties of matter is of considerable interest. The most intensively investigated materials in this regard are Iridium-based transition metal oxides which exhibit a host of interesting ground states that originate from a 5d5 Jeff = 1/2 electronic configuration. Moving beyond the Jeff = 1/2 paradigm to other electronic configurations where spin-orbit coupling plays a prominent role is a key objective of ongoing research. Here we focus on several Osmium-based transition metal oxides such as NaOsO3, Cd2Os2O7, Ca3LiOsO6, Sr2ScOsO6, Ba2YOsO6, and Sr2FeOsO6, which are nominally in the 5d3 electronic configuration. Within the LS coupling picture and a strong octahedral crystal field, the 5d3 configuration is expected to be an orbital singlet and spin-orbit effects should be minimal. Nevertheless, our neutron and x-ray scattering investigations of these materials as well as investigations by other groups show dramatic effects of spin-orbit coupling including reduced moment magnetic order, enhanced spin-phonon coupling, and large spin gaps. In particular, the anisotropy induced by spin-orbit coupling tips the balance of the frustrated interactions and drives the selection of particular magnetic ground states. To understand the mechanism driving the spin-orbit effects, we have explored the ground state t2g manifold with resonant inelastic x-ray scattering and observe a spectrum inexplicable by an LS coupling picture. On the other hand, an intermediate coupling approach reveals that the ground state wave function is a J =3/2 configuration which answers the question of how strong spin-orbit coupling effects arise in 5d3 systems.

Stress spillover, African Americans' couple and health outcomes, and the stress-buffering effect of family-centered prevention.

PubMed

Barton, Allen W; Beach, Steven R H; Bryant, Chalandra M; Lavner, Justin A; Brody, Gene H

2018-03-01

This study investigated (a) the stress spillover pathways linking contextual stressors, changes in couple relationship functioning and depressive symptoms, and changes in individuals' physical health, and (b) the stress-buffering effect of participation in an efficacious, family centered prevention program designed to protect couples from the deleterious effects of stressors. The sample consisted of 346 rural African American couples (63% married) who participated in a randomized controlled trial of the Protecting Strong African American Families (ProSAAF) program. Participants were assessed at three time points across 17 months. Results examining stress spillover within the control group indicated that elevated current, but not prior, financial hardship was associated with decreased effective communication, relationship satisfaction, and relationship confidence as well as increased depressive symptoms; current levels of racial discrimination also predicted greater depressive symptoms. Relationship confidence and relationship satisfaction, but not communication or depressive symptoms, in turn predicted declines in self-reported physical health. Results examining stress-buffering effects suggested that participation in ProSAAF protected individuals' relationship confidence from declines associated with elevated financial hardship. In addition, the indirect effect linking financial hardship to declines in physical health through relationship confidence that emerged among participants in the control group was no longer evident for ProSAAF couples. Results highlight the effect of contextual stressors on African Americans' couple and individual well-being and the potential for the ProSAAF program to provide a constructed resilience resource, protecting couple's confidence in their relationship from the negative effects of financial hardship and, consequently, promoting physical health. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Multiferroic magnetoelectric coupling effect of bilayer La1.2Sr1.8Mn2O7/PbZr0.3Ti0.7O3 complex thin film

NASA Astrophysics Data System (ADS)

Liang, K.; Zhou, P.; Ma, Z. J.; Qi, Y. J.; Mei, Z. H.; Zhang, T. J.

2017-05-01

Magnetoelectric (ME) coupling effect of 2-2-type ferromagnetic/ferroelectric bi-layer multiferroic epitaxial thin film (La1.2Sr1.8Mn2O7/PbZr0.3Ti0.7O3, LSMO/PZT) on SrRuO3 (SRO) substrate is investigated systematically by using Landau-Ginzburg-Devonshire (LGD) thermodynamic theory and modified constitutive equations. The calculating results clarify the detail relationships between ME coupling response and the residual strain, the volume fraction of constituent phases, the interface coupling coefficients, the magnetic field and the temperature. It also shows that improved ME coupling response can be modulated by these parameters. External magnetic fields (H1) induced ME coupling effect could be enhanced around Curie Temperature (Tc) of ferromagnetic phase and ME voltage coefficient (αE31) approaches a maximum at H1 ∼ 4.5 kOe near Tc. The remarkable variations of ME coupling response can be used to provide useful guidelines on the design of multifunctional devices.

Effect of Silane Coupling Agent on Tribological Properties of Hemp Fiber-Reinforced Plant-Derived Polyamide 1010 Biomass Composites

PubMed Central

Kajiyama, Tetsuto; Yamanaka, Toshiyuki

2017-01-01

We have studied the effects of silane coupling agents used for the surface treatment of fiber on the tribological properties of hemp fiber (HF) reinforced plant-derived polyamide 1010 (PA1010) biomass composites. Hemp fibers were surface-treated by two surface treatment methods: (a) alkali treatment by sodium hydroxide solution and (b) surface treatment by silane coupling agents. Three types of silane coupling agents, namely aminosilane, epoxysilane and ureidosilane were used. These HF/PA1010 biomass composites were extruded using a twin extruder, and injection-molded. The mechanical and tribological properties were evaluated by the ring-on-plate type sliding wear test. It was found that tribological properties of HF/PA1010 biomass composites improved with the surface treatment by the silane coupling agent. This may be attributed to the change in the mode of friction and wear mechanism by the interfacial adhesion between fiber and matrix polymer according to the type of silane coupling agent used. In particular, the ureidosilane coupling agent showed the best improvement effect for the tribological properties of these biomass composites in this study. PMID:28872624

Quantum Phase Transitions in Cavity Coupled Dot systems

NASA Astrophysics Data System (ADS)

Kasisomayajula, Vijay; Russo, Onofrio

2011-03-01

We investigate a Quantum Dot System, in which the transconductance, in part, is due to spin coupling, with each dot subjected to a biasing voltage. When this system is housed in a QED cavity, the cavity dot coupling alters the spin coupling of the coupled dots significantly via the Purcell Effect. In this paper we show the extent to which one can control the various coupling parameters: the inter dot coupling, the individual dots coupling with the cavity and the coupled dots coupling with the cavity as a single entity. We show that the dots coupled to each other and to the cavity, the spin transport can be controlled selectively. We derive the conditions for such control explicitly. Further, we discuss the Quantum phase transition effects due to the charge and spin transport through the dots. The electron transport through the dots, electron-electron spin interaction and the electron-photon interaction are treated using the Non-equilibrium Green's Function Formalism. http://publish.aps.org/search/field/author/Trif_Mircea (Trif Mircea), http://publish.aps.org/search/field/author/Golovach_Vitaly_N (Vitaly N. Golovach), and http://publish.aps.org/search/field/author/Loss_Daniel (Daniel Loss), Phys. Rev. B 75, 085307 (2007)

Hydrodynamics of Normal Atomic Gases with Spin-orbit Coupling

PubMed Central

Hou, Yan-Hua; Yu, Zhenhua

2015-01-01

Successful realization of spin-orbit coupling in atomic gases by the NIST scheme opens the prospect of studying the effects of spin-orbit coupling on many-body physics in an unprecedentedly controllable way. Here we derive the linearized hydrodynamic equations for the normal atomic gases of the spin-orbit coupling by the NIST scheme with zero detuning. We show that the hydrodynamics of the system crucially depends on the momentum susceptibilities which can be modified by the spin-orbit coupling. We reveal the effects of the spin-orbit coupling on the sound velocities and the dipole mode frequency of the gases by applying our formalism to the ideal Fermi gas. We also discuss the generalization of our results to other situations. PMID:26483090

Hydrodynamics of Normal Atomic Gases with Spin-orbit Coupling.

PubMed

Hou, Yan-Hua; Yu, Zhenhua

2015-10-20

Successful realization of spin-orbit coupling in atomic gases by the NIST scheme opens the prospect of studying the effects of spin-orbit coupling on many-body physics in an unprecedentedly controllable way. Here we derive the linearized hydrodynamic equations for the normal atomic gases of the spin-orbit coupling by the NIST scheme with zero detuning. We show that the hydrodynamics of the system crucially depends on the momentum susceptibilities which can be modified by the spin-orbit coupling. We reveal the effects of the spin-orbit coupling on the sound velocities and the dipole mode frequency of the gases by applying our formalism to the ideal Fermi gas. We also discuss the generalization of our results to other situations.

Time Delay Effect in a Living Coupled Oscillator System with the Plasmodium of Physarum polycephalum

NASA Astrophysics Data System (ADS)

Takamatsu, Atsuko; Fujii, Teruo; Endo, Isao

2000-08-01

A living coupled oscillator system was constructed by a cell patterning method with a plasmodial slime mold, in which parameters such as coupling strength and distance between the oscillators can be systematically controlled. Rich oscillation phenomena between the two-coupled oscillators, namely, desynchronizing and antiphase/in-phase synchronization were observed according to these parameters. Both experimental and theoretical approaches showed that these phenomena are closely related to the time delay effect in interactions between the oscillators.

Preheating after multifield inflation with nonminimal couplings. III. Dynamical spacetime results

NASA Astrophysics Data System (ADS)

DeCross, Matthew P.; Kaiser, David I.; Prabhu, Anirudh; Prescod-Weinstein, Chanda; Sfakianakis, Evangelos I.

2018-01-01

This paper concludes our semianalytic study of preheating in inflationary models comprised of multiple scalar fields coupled nonminimally to gravity. Using the covariant framework of paper I in this series, we extend the rigid-spacetime results of paper II by considering both the expansion of the Universe during preheating, as well as the effect of the coupled metric perturbations on particle production. The adiabatic and isocurvature perturbations are governed by different effective masses that scale differently with the nonminimal couplings and evolve differently in time. The effective mass for the adiabatic modes is dominated by contributions from the coupled metric perturbations immediately after inflation. The metric perturbations contribute an oscillating tachyonic term that enhances an early period of significant particle production for the adiabatic modes, which ceases on a time scale governed by the nonminimal couplings ξI . The effective mass of the isocurvature perturbations, on the other hand, is dominated by contributions from the fields' potential and from the curvature of the field-space manifold (in the Einstein frame), the balance between which shifts on a time scale governed by ξI. As in papers I and II, we identify distinct behavior depending on whether the nonminimal couplings are small [ξI≲O (1 ) ], intermediate [ξI˜O (1 -10 ) ], or large (ξI≥100 ).

A multi-scale and multi-field coupling nonlinear constitutive theory for the layered magnetoelectric composites

NASA Astrophysics Data System (ADS)

Xu, Hao; Pei, Yongmao; Li, Faxin; Fang, Daining

2018-05-01

The magnetic, electric and mechanical behaviors are strongly coupled in magnetoelectric (ME) materials, making them great promising in the application of functional devices. In this paper, the magneto-electro-mechanical fully coupled constitutive behaviors of ME laminates are systematically studied both theoretically and experimentally. A new probabilistic domain switching function considering the surface ferromagnetic anisotropy and the interface charge-mediated effect is proposed. Then a multi-scale multi-field coupling nonlinear constitutive model for layered ME composites is developed with physical measureable parameters. The experiments were performed to compare the theoretical predictions with the experimental data. The theoretical predictions have a good agreement with experimental results. The proposed constitutive relation can be used to describe the nonlinear multi-field coupling properties of both ME laminates and thin films. Several novel coupling experimental phenomena such as the electric-field control of magnetization, and the magnetic-field tuning of polarization are observed and analyzed. Furthermore, the size-effect of the electric tuning behavior of magnetization is predicted, which demonstrates a competition mechanism between the interface strain-mediated effect and the charge-driven effect. Our study offers deep insight into the coupling microscopic mechanism and macroscopic properties of ME layered composites, which is benefit for the design of electromagnetic functional devices.

Better Homes and Families: Housing Markets and Young Couple Stability in Sweden

ERIC Educational Resources Information Center

Lauster, Nathanael T.

2008-01-01

I model the relationship between aspects of the housing market influenced by housing policy and couple stability for cohabiting couples in Sweden. Using data on 3,851 cohabiting couples obtained from the Swedish Family Survey of 1992, I examine the effects of housing market characteristics on couple outcomes. I focus on three housing variables,…

Acquired Immune Deficiency Syndrome: A Preliminary Examination of the Effects on Gay Couples and Coupling.

ERIC Educational Resources Information Center

Carl, Douglas

1986-01-01

The Acquired Immune Deficiency Syndrome (AIDS) epidemic significantly influences attitudes about life and lifestyles. Homosexuals have to give increased consideration to coupling, the nature of coupled relationships, sex and intimacy, and death long before the normal time. Discusses impact of AIDS on the early stages of gay coupling and on the…

A Dyadic Approach to Infertility Stress, Marital Adjustment, and Depression on Quality of Life in Infertile Couples.

PubMed

Kim, Ju Hee; Shin, Hye Sook; Yun, Eun Kyoung

2018-03-01

This study was conducted to examine the level of infertility stress, marital adjustment, depression, and quality of life in infertile couples and assess the actor and partner effects in these areas using the actor-partner interdependence model. Cross-sectional study. Participants were 121 infertile couples. After pilot study, data were collected from November 2012 to March 2013 using the following questionnaires: the Fertility Quality of Life, Fertility Problem Inventory, Revised Dyadic Adjustment Scale, and Beck Depression Inventory. There was a gender difference in infertility stress, depression, and quality of life. Infertility stress had actor and partner effects on the quality of life. Marital adjustment had an actor effect on the quality of life for the wives. Depression had actor and partner effects on quality of life for the wives, but only an actor effect for the husbands. This study found that there were actor and partner effects of infertility stress, marital adjustment, and depression on the quality of life in infertile couples. These findings may help nurses be aware of such effects and can be used as a baseline data in the development of nursing interventions for infertile couples.

On MIMO-UFMC in the Presence of Phase Noise and Antenna Mutual Coupling

NASA Astrophysics Data System (ADS)

Chen, Xiaoming; Zhang, Shuai; Zhang, Anxue

2017-11-01

The universal filtered multicarrier (UFMC) technique has been proposed as a waveform candidate for the fifth generation (5G) communications and beyond 5G. Compared with conventional orthogonal frequency division multiplexing (OFDM), UFMC has lower out-of-band emission and is also compatible with the multiple-input multiple-output (MIMO) technique. However, like other multicarrier waveforms, it suffers from phase noise of imperfect oscillator. In contrast to the rich literature on phase noise effect on MIMO-OFDM (where the antenna mutual coupling effect is usually omitted though), there is little work investigating the phase noise effect on MIMO-UFMC. In this paper, we study the MIMO-UFMC systems in the presence of phase noise and with/without mutual coupling effect. A phase noise mitigation scheme for MIMO-UFMC systems is presented. The scheme does not require detailed knowledge of the phase noise statistics and can effectively mitigate the phase noise within each UFMC symbol. Moreover, it is shown that at small antenna separations, the performance of the MIMO-UFMC system taking the mutual coupling effect into account is better than that when the mutual coupling effect is overlooked.

Planning for Coupling Effects in Bitoric Mixed Astigmatism Ablative Treatments.

PubMed

Alpins, Noel; Ong, James K Y; Stamatelatos, George

2017-08-01

To demonstrate how to determine the historical coupling adjustments of bitoric mixed astigmatism ablative treatments and how to use these historical coupling adjustments to adjust future bitoric treatments. The individual coupling adjustments of the myopic and hyperopic cylindrical components of a bitoric treatment were derived empirically from a retrospective study where the theoretical combined treatment effect on spherical equivalent was compared to the actual change in refractive spherical equivalent. The coupling adjustments that provided the best fit in both mean and standard deviation were determined to be the historical coupling adjustments. Theoretical treatments that incorporated the historical coupling adjustments were then calculated. The actual distribution of postoperative spherical equivalent errors was compared to the theoretically adjusted distribution. The study group comprised 242 eyes and included 118 virgin right eyes and 124 virgin left eyes of 155 individuals. For the laser used, the myopic coupling adjustment was -0.02 and the hyperopic coupling adjustment was 0.30, as derived by global nonlinear optimization. This implies that almost no adjustment of the myopic component of the bitoric treatment is necessary, but that the hyperopic component of the bitoric treatment generates a large amount of unintended spherical shift. The theoretically adjusted treatments targeted zero mean spherical equivalent error, as intended, and the distribution of the theoretical spherical equivalent errors had the same spread as the distribution of actual postoperative spherical equivalent errors. Bitoric mixed astigmatism ablative treatments may display non-trivial coupling effects. Historical coupling adjustments should be taken into consideration when planning mixed astigmatism treatments to improve surgical outcomes. [J Refract Surg. 2017;33(8):545-551.]. Copyright 2017, SLACK Incorporated.

Medium effect on the characteristics of the coupled seismic and electromagnetic signals.

PubMed

Huang, Qinghua; Ren, Hengxin; Zhang, Dan; Chen, Y John

2015-01-01

Recently developed numerical simulation technique can simulate the coupled seismic and electromagnetic signals for a double couple point source or a finite fault planar source. Besides the source effect, the simulation results showed that both medium structure and medium property could affect the coupled seismic and electromagnetic signals. The waveform of coupled signals for a layered structure is more complicated than that for a simple uniform structure. Different from the seismic signals, the electromagnetic signals are sensitive to the medium properties such as fluid salinity and fluid viscosity. Therefore, the co-seismic electromagnetic signals may be more informative than seismic signals.

Medium effect on the characteristics of the coupled seismic and electromagnetic signals

PubMed Central

HUANG, Qinghua; REN, Hengxin; ZHANG, Dan; CHEN, Y. John

2015-01-01

Recently developed numerical simulation technique can simulate the coupled seismic and electromagnetic signals for a double couple point source or a finite fault planar source. Besides the source effect, the simulation results showed that both medium structure and medium property could affect the coupled seismic and electromagnetic signals. The waveform of coupled signals for a layered structure is more complicated than that for a simple uniform structure. Different from the seismic signals, the electromagnetic signals are sensitive to the medium properties such as fluid salinity and fluid viscosity. Therefore, the co-seismic electromagnetic signals may be more informative than seismic signals. PMID:25743062

Analysing home-ownership of couples: the effect of selecting couples at the time of the survey.

PubMed

Mulder, C H

1996-09-01

"The analysis of events encountered by couple and family households may suffer from sample selection bias when data are restricted to couples existing at the moment of interview. The paper discusses the effect of sample selection bias on event history analyses of buying a home [in the Netherlands] by comparing analyses performed on a sample of existing couples with analyses of a more complete sample including past as well as current partner relationships. The results show that, although home-buying in relationships that have ended differs clearly from behaviour in existing relationships, sample selection bias is not alarmingly large." (SUMMARY IN FRE) excerpt

Size and location of defects at the coupling interface affect lithotripter performance.

PubMed

Li, Guangyan; Williams, James C; Pishchalnikov, Yuri A; Liu, Ziyue; McAteer, James A

2012-12-01

Study Type--Therapy (case series) Level of Evidence 4. What's known on the subject? and What does the study add? In shock wave lithotripsy air pockets tend to get caught between the therapy head of the lithotripter and the skin of the patient. Defects at the coupling interface hinder the transmission of shock wave energy into the body, reducing the effectiveness of treatment. This in vitro study shows that ineffective coupling not only blocks the transmission of acoustic pulses but also alters the properties of shock waves involved in the mechanisms of stone breakage, with the effect dependent on the size and location of defects at the coupling interface. • To determine how the size and location of coupling defects caught between the therapy head of a lithotripter and the skin of a surrogate patient (i.e. the acoustic window of a test chamber) affect the features of shock waves responsible for stone breakage. • Model defects were placed in the coupling gel between the therapy head of a Dornier Compact-S electromagnetic lithotripter (Dornier MedTech, Kennesaw, GA, USA) and the Mylar (biaxially oriented polyethylene terephthalate) (DuPont Teijin Films, Chester, VA, USA) window of a water-filled coupling test system. • A fibre-optic probe hydrophone was used to measure acoustic pressures and map the lateral dimensions of the focal zone of the lithotripter. • The effect of coupling conditions on stone breakage was assessed using gypsum model stones. • Stone breakage decreased in proportion to the area of the coupling defect; a centrally located defect blocking only 18% of the transmission area reduced stone breakage by an average of almost 30%. • The effect on stone breakage was greater for defects located on-axis and decreased as the defect was moved laterally; an 18% defect located near the periphery of the coupling window (2.0 cm off-axis) reduced stone breakage by only ~15% compared to when coupling was completely unobstructed. • Defects centred within the coupling window acted to narrow the focal width of the lithotripter; an 8.2% defect reduced the focal width ~30% compared to no obstruction (4.4 mm vs 6.5 mm). • Coupling defects located slightly off centre disrupted the symmetry of the acoustic field; an 18% defect positioned 1.0 cm off-axis shifted the focus of maximum positive pressure ~1.0 mm laterally. • Defects on and off-axis imposed a significant reduction in the energy density of shock waves across the focal zone. • In addition to blocking the transmission of shock-wave energy, coupling defects also disrupt the properties of shock waves that play a role in stone breakage, including the focal width of the lithotripter and the symmetry of the acoustic field • The effect is dependent on the size and location of defects, with defects near the centre of the coupling window having the greatest effect. • These data emphasize the importance of eliminating air pockets from the coupling interface, particularly defects located near the centre of the coupling window. © 2012 BJU INTERNATIONAL.

Numerical simulation of aerodynamic performance of a couple multiple units high-speed train

NASA Astrophysics Data System (ADS)

Niu, Ji-qiang; Zhou, Dan; Liu, Tang-hong; Liang, Xi-feng

2017-05-01

In order to determine the effect of the coupling region on train aerodynamic performance, and how the coupling region affects aerodynamic performance of the couple multiple units trains when they both run and pass each other in open air, the entrance of two such trains into a tunnel and their passing each other in the tunnel was simulated in Fluent 14.0. The numerical algorithm employed in this study was verified by the data of scaled and full-scale train tests, and the difference lies within an acceptable range. The results demonstrate that the distribution of aerodynamic forces on the train cars is altered by the coupling region; however, the coupling region has marginal effect on the drag and lateral force on the whole train under crosswind, and the lateral force on the train cars is more sensitive to couple multiple units compared to the other two force coefficients. It is also determined that the component of the coupling region increases the fluctuation of aerodynamic coefficients for each train car under crosswind. Affected by the coupling region, a positive pressure pulse was introduced in the alternating pressure produced by trains passing by each other in the open air, and the amplitude of the alternating pressure was decreased by the coupling region. The amplitude of the alternating pressure on the train or on the tunnel was significantly decreased by the coupling region of the train. This phenomenon did not alter the distribution law of pressure on the train and tunnel; moreover, the effect of the coupling region on trains passing by each other in the tunnel is stronger than that on a single train passing through the tunnel.

Effects of Coping-Oriented Couples Therapy on Depression: A Randomized Clinical Trial

ERIC Educational Resources Information Center

Bodenmann, Guy; Plancherel, Bernard; Beach, Steven R. H.; Widmer, Kathrin; Gabriel, Barbara; Meuwly, Nathalie; Charvoz, Linda; Hautzinger, Martin; Schramm, Elisabeth

2008-01-01

The aim of this study was to evaluate the effectiveness of treating depression with coping-oriented couples therapy (COCT) as compared with cognitive-behavioral therapy (CBT; A. T. Beck, C. Ward, & M. Mendelson, 1961) and interpersonal psychotherapy (IPT; M. M. Weissman, J. C. Markowitz, & G. L. Klerman, 2000). Sixty couples, including 1…

Short-Term-Effectiveness of a Relationship Education Program for Distressed Military Couples, in the Context of Foreign Assignments for the German Armed Forces. Preliminary Findings From a Randomized Controlled Study.

PubMed

Kröger, Christoph; Kliem, Sören; Zimmermann, Peter; Kowalski, Jens

2018-04-01

This study examines the short-term effectiveness of a relationship education program designed for military couples. Distressed couples were randomly placed in either a wait-list control group or an intervention group. We conducted training sessions before a 3-month foreign assignment, and refresher courses approximately 6-week post-assignment. We analyzed the dyadic data of 32 couples, using hierarchical linear modeling in a two-level model. Reduction in unresolved conflicts was found in the intervention group, with large pre-post effects for both partners. Relationship satisfaction scores were improved, with moderate-to-large effects only for soldiers, rather than their partners. Post-follow-up effect sizes suggested further improvement in the intervention group. Future research should examine the long-term effectiveness of this treatment. © 2017 American Association for Marriage and Family Therapy.

Elastic interaction among transition metals in one-dimensional spin-crossover solids

NASA Astrophysics Data System (ADS)

Boukheddaden, K.; Miyashita, S.; Nishino, M.

2007-03-01

We present an exact examination of a one-dimensional (1D) spin-phonon model describing the thermodynamical properties of spin-crossover (SC) solids. This model has the advantage of giving a physical mechanism for the interaction between the SC units. The origin of the interaction comes from the fact that the elastic constant of the spring linking two atoms depends on their electronic states. This leads to local variation of the elastic constant. Up to now, all the statistical studies of this model have been performed in the frame of the mean-field (MF) approach, which is not adequate to describe 1D systems with short-range interactions. An alternative method, based on the variational approach and taking into account the short-range correlations between neighboring molecules, was also suggested, but it consists in an extension of the previous MF approximation. Here, we solve exactly this Hamiltonian in the frame of classical statistical mechanics using the transfer-matrix technique. The temperature dependence of the high spin fraction and that of the total energy are obtained analytically. Our results clearly show that there is a clear tendency to a sharp transition when we tune the elastic constants adequately, which indicates that first-order phase transition takes place at higher dimensions. In addition, we demonstrate the existence of an interesting isomorphism between the present model and Ising model under effective interaction and effective ligand field energy, in which both depend linearly on temperature and both come from the phonon contribution. We have also studied the effect of the pressure (the tension) on the thermodynamical properties of the high spin (HS) fraction and have found a nontrivial pressure effect that while for weak tension values, the low spin state is stabilized for the pressure above a threshold value, it enhances the interaction between the HS states. Finally, we have also introduced elastic interactions between the chains. Treating exactly (in mean field) the intrachain (interchain) contributions, we found that our model leads us to obtain first-order spin transitions when both short- and long-range interactions are ferroelastic. We show also that competing (antiferroelastic short-range and ferroelastic long-range) interactions between spin-state ions reproduce qualitatively the two-step-like spin-crossover transitions.

A 2-DOF microstructure-dependent model for the coupled torsion/bending instability of rotational nanoscanner

NASA Astrophysics Data System (ADS)

Keivani, M.; Abadian, N.; Koochi, A.; Mokhtari, J.; Abadyan, M.

2016-10-01

It has been well established that the physical performance of nanodevices might be affected by the microstructure. Herein, a two-degree-of-freedom model base on the modified couple stress theory is developed to incorporate the impact of microstructure in the torsion/bending coupled instability of rotational nanoscanner. Effect of microstructure dependency on the instability parameters is determined as a function of the microstructure parameter, bending/torsion coupling ratio, van der Waals force parameter and geometrical dimensions. It is found that the bending/torsion coupling substantially affects the stable behavior of the scanners especially those with long rotational beam elements. Impact of microstructure on instability voltage of the nanoscanner depends on coupling ratio and the conquering bending mode over torsion mode. This effect is more highlighted for higher values of coupling ratio. Depending on the geometry and material characteristics, the presented model is able to simulate both hardening behavior (due to microstructure) and softening behavior (due to torsion/bending coupling) of the nanoscanners.

[Effects on couples' communication, intimacy, conflict and quality of life by foot massage between immigrants].

PubMed

Uhm, Dong-choon

2010-08-01

The purpose of this study was to evaluate the effects on immigrant couples' communication, intimacy, conflict and quality of life when using foot massage. The research design consisted of pre-and-post test consecutive experimental design through a nonequivalent control group. Data were collected July 6, 2009 to February 27, 2010. The 36 couples were divided into two groups, experimental and control with 18 couples in each group. Foot massage was applied twice a week for 6 weeks by the couples in the experimental group. There were statistically significant increases in communication (p=.011), intimacy (p<.001), quality of life (p=.017) between the couples in the experimental group compared to the control group. There was also a statistically significant decrease in conflict (p=.003) between the couples in the experimental group compared to the control group. Foot massage can be applied as a nursing intervention for improvement of marital relationship in immigrant couples.

Optical spectroscopy and system-bath interactions in molecular aggregates with full configuration interaction Frenkel exciton model

NASA Astrophysics Data System (ADS)

Seibt, Joachim; Sláma, Vladislav; Mančal, Tomáš

2016-12-01

Standard application of the Frenkel exciton model neglects resonance coupling between collective molecular aggregate states with different number of excitations. These inter-band coupling terms are, however, of the same magnitude as the intra-band coupling between singly excited states. We systematically derive the Frenkel exciton model from quantum chemical considerations, and identify it as a variant of the configuration interaction method. We discuss all non-negligible couplings between collective aggregate states, and provide compact formulae for their calculation. We calculate absorption spectra of molecular aggregate of carotenoids and identify significant band shifts as a result of inter-band coupling. The presence of inter-band coupling terms requires renormalization of the system-bath coupling with respect to standard formulation, but renormalization effects are found to be weak. We present detailed discussion of molecular dimer and calculate its time-resolved two-dimensional Fourier transformed spectra to find weak but noticeable effects of peak amplitude redistribution due to inter-band coupling.

Study of gain-coupled distributed feedback laser based on high order surface gain-coupled gratings

NASA Astrophysics Data System (ADS)

Gao, Feng; Qin, Li; Chen, Yongyi; Jia, Peng; Chen, Chao; Cheng, LiWen; Chen, Hong; Liang, Lei; Zeng, Yugang; Zhang, Xing; Wu, Hao; Ning, Yongqiang; Wang, Lijun

2018-03-01

Single-longitudinal-mode, gain-coupled distributed feedback (DFB) lasers based on high order surface gain-coupled gratings are achieved. Periodic surface metal p-contacts with insulated grooves realize gain-coupled mechanism. To enhance gain contrast in the quantum wells without the introduction of effective index-coupled effect, groove length and depth were well designed. Our devices provided a single longitudinal mode with the maximum CW output power up to 48.8 mW/facet at 971.31 nm at 250 mA without facet coating, 3dB linewidth (<3.2 pm) and SMSR (>39 dB). Optical bistable characteristic was observed with a threshold current difference. Experimentally, devices with different cavity lengths were contrasted on power-current and spectrum characteristics. Due to easy fabrication technique and stable performance, it provides a method of fabricating practical gain-coupled distributed feedback lasers for commercial applications.

When gentlemen are first and ladies are last: effects of gender stereotypes on the order of romantic partners' names.

PubMed

Hegarty, Peter; Watson, Nila; Fletcher, Laura; McQueen, Grant

2011-03-01

A preference to name stereotypically masculine before stereotypically feminine individuals explains why men are typically named before women, as on the Internet, for example (Study 1). Heterosexual couples are named with men's names first more often when such couples are imagined to conform to gender stereotypes (Studies 2 and 3). First-named partners of imaginary same-sex couples are attributed more stereotypically masculine attributes (Study 4). Familiarity bounds these effects of stereotypes on name order. People name couples they know well with closer people first (Study 5), and consequently name familiar heterosexual couples with members of their own gender first (Study 6). These studies evidence a previously unknown effect of the semantics of gender stereotypes on sentence structure in the everyday use of English. ©2010 The British Psychological Society.

Antisymmetric Spin-Orbit Coupling in a d-p Model on a Zigzag Chain

DOE PAGES

Sugita, Yusuke; Hayami, Satoru; Motome, Yukitoshi

2015-12-29

In this paper, we theoretically investigate how an antisymmetric spin-orbit coupling emerges in electrons moving on lattice structures which are centrosymmetric but break the spatial inversion symme- try at atomic positions. We construct an effective d-p model on the simplest lattice structure, a zigzag chain of edge-sharing octahedra, with taking into account the crystalline electric field, the spin-orbit coupling, and on-site and inter-site d-p hybridizations. We show that an effective antisymmetric spin-orbit coupling arises in the sublattice-dependent form, which results in a hidden spin polarization in the band structure. Finally, we explicitly derive the effective antisymmetric spin-orbit coupling for dmore » electrons, which not only explains the hidden spin polarization but also indicates how to enhance it.« less

A spin-orbit coupling for a neutral particle from Lorentz symmetry breaking effects in the CPT-odd sector of the Standard Model Extension

NASA Astrophysics Data System (ADS)

Belich, H.; Bakke, K.

2015-07-01

We start by investigating the arising of a spin-orbit coupling and a Darwin-type term that stem from Lorentz symmetry breaking effects in the CPT-odd sector of the Standard Model Extension. Then, we establish a possible scenario of the violation of the Lorentz symmetry that gives rise to a linear confining potential and an effective electric field in which determines the spin-orbit coupling for a neutral particle analogous to the Rashba coupling [E. I. Rashba, Sov. Phys. Solid State 2, 1109 (1960)]. Finally, we confine the neutral particle to a quantum dot [W.-C. Tan and J. C. Inkson, Semicond. Sci. Technol. 11, 1635 (1996)] and analyze the influence of the linear confining potential and the spin-orbit coupling on the spectrum of energy.

Antisymmetric Spin-Orbit Coupling in a d-p Model on a Zigzag Chain

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

Sugita, Yusuke; Hayami, Satoru; Motome, Yukitoshi

In this paper, we theoretically investigate how an antisymmetric spin-orbit coupling emerges in electrons moving on lattice structures which are centrosymmetric but break the spatial inversion symme- try at atomic positions. We construct an effective d-p model on the simplest lattice structure, a zigzag chain of edge-sharing octahedra, with taking into account the crystalline electric field, the spin-orbit coupling, and on-site and inter-site d-p hybridizations. We show that an effective antisymmetric spin-orbit coupling arises in the sublattice-dependent form, which results in a hidden spin polarization in the band structure. Finally, we explicitly derive the effective antisymmetric spin-orbit coupling for dmore » electrons, which not only explains the hidden spin polarization but also indicates how to enhance it.« less

Directly Characterizing the Relative Strength and Momentum Dependence of Electron-Phonon Coupling Using Resonant Inelastic X-Ray Scattering

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

Devereaux, T. P.; Shvaika, A. M.; Wu, K.

The coupling between lattice and charge degrees of freedom in condensed matter materials is ubiquitous and can often result in interesting properties and ordered phases, including conventional superconductivity, charge-density wave order, and metal-insulator transitions. Angle-resolved photoemission spectroscopy and both neutron and nonresonant x-ray scattering serve as effective probes for determining the behavior of appropriate, individual degrees of freedom—the electronic structure and lattice excitation, or phonon dispersion, respectively. However, each provides less direct information about the mutual coupling between the degrees of freedom, usually through self-energy effects, which tend to renormalize and broaden spectral features precisely where the coupling is strong,more » impacting one’s ability to quantitatively characterize the coupling. Here, we demonstrate that resonant inelastic x-ray scattering, or RIXS, can be an effective tool to directly determine the relative strength and momentum dependence of the electron-phonon coupling in condensed matter systems. Using a diagrammatic approach for an eight-band model of copper oxides, we study the contributions from the lowest-order diagrams to the full RIXS intensity for a realistic scattering geometry, accounting for matrix element effects in the scattering cross section, as well as the momentum dependence of the electron-phonon coupling vertex. A detailed examination of these maps offers a unique perspective into the characteristics of electron-phonon coupling, which complements both neutron and nonresonant x-ray scattering, as well as Raman and infrared conductivity.« less

Directly Characterizing the Relative Strength and Momentum Dependence of Electron-Phonon Coupling Using Resonant Inelastic X-Ray Scattering

DOE PAGES

Devereaux, T. P.; Shvaika, A. M.; Wu, K.; ...

2016-10-25

The coupling between lattice and charge degrees of freedom in condensed matter materials is ubiquitous and can often result in interesting properties and ordered phases, including conventional superconductivity, charge-density wave order, and metal-insulator transitions. Angle-resolved photoemission spectroscopy and both neutron and nonresonant x-ray scattering serve as effective probes for determining the behavior of appropriate, individual degrees of freedom—the electronic structure and lattice excitation, or phonon dispersion, respectively. However, each provides less direct information about the mutual coupling between the degrees of freedom, usually through self-energy effects, which tend to renormalize and broaden spectral features precisely where the coupling is strong,more » impacting one’s ability to quantitatively characterize the coupling. Here, we demonstrate that resonant inelastic x-ray scattering, or RIXS, can be an effective tool to directly determine the relative strength and momentum dependence of the electron-phonon coupling in condensed matter systems. Using a diagrammatic approach for an eight-band model of copper oxides, we study the contributions from the lowest-order diagrams to the full RIXS intensity for a realistic scattering geometry, accounting for matrix element effects in the scattering cross section, as well as the momentum dependence of the electron-phonon coupling vertex. A detailed examination of these maps offers a unique perspective into the characteristics of electron-phonon coupling, which complements both neutron and nonresonant x-ray scattering, as well as Raman and infrared conductivity.« less

Can we predict failure in couple therapy early enough to enhance outcome?

PubMed

Pepping, Christopher A; Halford, W Kim; Doss, Brian D

2015-02-01

Feedback to therapists based on systematic monitoring of individual therapy progress reliably enhances therapy outcome. An implicit assumption of therapy progress feedback is that clients unlikely to benefit from therapy can be detected early enough in the course of therapy for corrective action to be taken. To explore the possibility of using feedback of therapy progress to enhance couple therapy outcome, the current study tested whether weekly therapy progress could detect off-track clients early in couple therapy. In an effectiveness trial of couple therapy, 136 couples were monitored weekly on relationship satisfaction and an expert derived algorithm was used to attempt to predict eventual therapy outcome. As expected, the algorithm detected a significant proportion of couples who did not benefit from couple therapy at Session 3, but prediction was substantially improved at Session 4 so that eventual outcome was accurately predicted for 70% of couples, with little improvement of prediction thereafter. More sophisticated algorithms might enhance prediction accuracy, and a trial of the effects of therapy progress feedback on couple therapy outcome is needed. Copyright © 2015 Elsevier Ltd. All rights reserved.

An investigation of the effects of pitch-roll (de)coupling on helicopter handling qualities

NASA Technical Reports Server (NTRS)

Blanken, C. L.; Pausder, H. J.; Ockier, C. J.

1995-01-01

An extensive investigation of the effects of pitch-roll coupling on helicopter handling qualities was performed by the U.S. Army and Deutsche Forschungsanstalt fur Luft- und Raumfahrt (DLR), using a NASA ground-based and a DLR in-flight simulator. Over 90 different coupling configurations were evaluated using a high gain roll-axis tracking task. The results show that although the current ADS-33C coupling criterion discriminates against those types of coupling typical of conventionally controlled helicopters, it is not always suited for the prediction of handling qualities of helicopters with modern control systems. Based on the observation that high frequency inputs during tracking are used to alleviate coupling, a frequency domain pitch-roll coupling criterion that uses the average coupling ratio between the bandwidth and neutral stability frequency is formulated. This criterion provides a more comprehensive coverage with respect to the different types of coupling, shows excellent consistency, and has the additional benefit that compliance testing data are obtained from the bandwidth/phase delay tests, so that no additional flight testing is needed.

Effects of large vessel on temperature distribution based on photothermal coupling interaction model

NASA Astrophysics Data System (ADS)

Li, Zhifang; Zhang, Xiyang; Li, Zuoran; Li, Hui

2016-10-01

This paper is based on the finite element analysis method for studying effects of large blood vessel on temperature based on photothermal coupling interaction model, and it couples the physical field of optical transmission with the physical field of heat transfer in biological tissue by using COMSOL Multiphysics 4.4 software. The results demonstrate the cooling effect of large blood vessel, which can be potential application for the treatment of liver tumors.

Hall effects on peristaltic flow of couple stress fluid in a vertical asymmetric channel

NASA Astrophysics Data System (ADS)

Maninaga Kumar, P.; Kavitha, A.; Saravana, R.

2017-11-01

The influence of Hall effect on peristaltic transport of a couple stress fluid in a vertical asymmetric channel is examined. The problem is solved under the assumptions of low Reynolds number and long wavelength. The velocity, temperature and concentration are obtained by using analytical solutions. Effect of Hall parameter, couple stress fluid parameter, Froude number, Hartmann number and the phase difference on the pumping characteristics, temperature and concentration are discussed graphically.

Coupling influence on the sensitivity of microfiber resonator sensors

NASA Astrophysics Data System (ADS)

Guo, Wei; Chen, Ye; Kou, Jun-long; Xu, Fei; Lu, Yan-qing

2011-12-01

By modifying the resonant condition of microfiber resonator sensors while taking the coupling effect into account, we theoretically investigate coupling influence on the resonant wavelength and sensitivity. Numerical calculation shows significant difference in resonant wavelength and sensitivity with different coupling strength. Tuning the coupling can shift the resonant position as far as several nanometers and change the sensitivity as large as 30 nm/RIU in an all-coupling microfiber coil resonator.

Doxorubicin coupled to lactosaminated albumin: Effects on rats with liver fibrosis and cirrhosis.

PubMed

Di Stefano, G; Fiume, L; Domenicali, M; Busi, C; Chieco, P; Kratz, F; Lanza, M; Mattioli, A; Pariali, M; Bernardi, M

2006-06-01

The conjugate of doxorubicin with lactosaminated human albumin has the potential of increasing the doxorubicin efficacy in the treatment of hepatocellular carcinomas expressing the asialoglycoprotein receptor. However, coupled doxorubicin also accumulates in the liver, which might damage hepatocytes. To verify whether coupled doxorubicin impairs liver function in rats with liver fibrosis and cirrhosis. Coupled doxorubicin was administered using the same schedule which exerted an antineoplastic effect on rat hepatocellular carcinomas (4-weekly injections of doxorubicin at 1 microg/g). Liver fibrosis/cirrhosis was produced by carbon tetrachloride (CCl4) poisoning. Liver samples were studied histologically. Serum parameters of liver function and viability were determined. In normal rats, administration of coupled doxorubicin neither caused microscopic changes of hepatocytes nor modified serum liver parameters. In rats with fibrosis/cirrhosis, although a selective doxorubicin accumulation within the liver followed coupled doxorubicin administration, the drug did not have a detrimental effect on the histology of the liver and, among serum liver tests, only alanine aminotransferase and aspartate aminotransferase levels were moderately modified. Coupled doxorubicin can be administered to rats with liver fibrosis/cirrhosis without inducing a severe liver damage. If further studies will confirm the efficacy and safety of this compound, coupled doxorubicin therapy may open a new perspective in the treatment of hepatocellular carcinoma.

The Lightning Electromagnetic Pulse Coupling Effect Inside the Shielding Enclosure With Penetrating Wire

NASA Astrophysics Data System (ADS)

Jiao, Xue; Yang, Bo

2017-10-01

To study the lightning electromagnetic pulse (LEMP) coupling and protection problems of shielding enclosure with penetrating wire, we adopt the model with proper size which is close to the practical engineering and the two-step finite-difference time-domain (FDTD) method is used for calculation in this paper. It is shown that the coupling voltage on the circuit lead inside the enclosure increases about 34 dB, when add 1.0 m long penetrating wire at the aperture, comparing with the case without penetrating wire. Meanwhile, the waveform, has the same wave outline as the lightning current source, shows that the penetrating wire brings a large number of low frequency component into the enclosure. The coupling effect in the enclosure will reduce greatly when penetrating wire has electrical connection with the enclosure at the aperture and the coupling voltage increase only about 12 dB than the case without penetrating wire. Moreover, the results show that though the waveguide pipe can reduce the coupling effect brought by the penetrating wire, the exposing part of penetrating wire can increase the coupling when the penetrating wire outside the enclosure is longer than the waveguide pipe and the longer the exposing part is, the stronger the coupling is.

Robust magnon-photon coupling in a planar-geometry hybrid of inverted split-ring resonator and YIG film.

PubMed

Bhoi, Biswanath; Kim, Bosung; Kim, Junhoe; Cho, Young-Jun; Kim, Sang-Koog

2017-09-20

We experimentally demonstrate strongly enhanced coupling between excited magnons in an Yttrium Iron Garnet (YIG) film and microwave photons in an inverted pattern of split-ring resonator (noted as ISRR). The anti-crossing effects of the ISRR's photon mode and the YIG's magnon modes were found from |S 21 |-versus-frequency measurements for different strengths and directions of externally applied magnetic fields. The spin-number-normalized coupling strength (i.e. single spin-photon coupling) [Formula: see text] was determined to 0.194 Hz ([Formula: see text] = 90 MHz) at 3.7 GHz frequency. Furthermore, we found that additional fine features in the anti-crossing region originate from the excitation of different spin-wave modes (such as the magnetostatic surface and the backward-volume magnetostatic spin-waves) rather than the Kittel-type mode. These spin-wave modes, as coupled with the ISRR mode, modify the anti-crossing effect as well as their coupling strength. An equivalent circuit model very accurately reproduced the observed anti-crossing effect and its coupling strength variation with the magnetic field direction in the planar-geometry ISRR/YIG hybrid system. This work paves the way for the design of new types of high-gain magnon-photon coupling systems in planar geometry.

Analog quantum simulation of the Rabi model in the ultra-strong coupling regime.

PubMed

Braumüller, Jochen; Marthaler, Michael; Schneider, Andre; Stehli, Alexander; Rotzinger, Hannes; Weides, Martin; Ustinov, Alexey V

2017-10-03

The quantum Rabi model describes the fundamental mechanism of light-matter interaction. It consists of a two-level atom or qubit coupled to a quantized harmonic mode via a transversal interaction. In the weak coupling regime, it reduces to the well-known Jaynes-Cummings model by applying a rotating wave approximation. The rotating wave approximation breaks down in the ultra-strong coupling regime, where the effective coupling strength g is comparable to the energy ω of the bosonic mode, and remarkable features in the system dynamics are revealed. Here we demonstrate an analog quantum simulation of an effective quantum Rabi model in the ultra-strong coupling regime, achieving a relative coupling ratio of g/ω ~ 0.6. The quantum hardware of the simulator is a superconducting circuit embedded in a cQED setup. We observe fast and periodic quantum state collapses and revivals of the initial qubit state, being the most distinct signature of the synthesized model.An analog quantum simulation scheme has been explored with a quantum hardware based on a superconducting circuit. Here the authors investigate the time evolution of the quantum Rabi model at ultra-strong coupling conditions, which is synthesized by slowing down the system dynamics in an effective frame.

Electronic Equalization of Multikilometer 10-Gb/s Multimode Fiber Links: Mode-Coupling Effects

NASA Astrophysics Data System (ADS)

Balemarthy, Kasyapa; Polley, Arup; Ralph, Stephen E.

2006-12-01

This paper investigates the ability of electronic equalization to compensate for modal dispersion in the presence of mode coupling in multimode fibers (MMFs) at 10 Gb/s. Using a new time-domain experimental method, mode coupling is quantified in MMF. These results, together with a comprehensive link model, allow to determine the impact of mode coupling on the performance of MMF. The equalizer performance on links from 300 m to 8 km is quantified with and without modal coupling. It is shown that the mode-coupling effects are influenced by the specific index profile and increase the equalizer penalty by as much as 1 dBo for 1-km links and 2.3 dBo for 2-km links when using a standard model of fiber profiles at 1310 nm.

The Bodenmann Couples Coping Enhancement Training (CCET): A New Approach to Prevention of Marital Distress Based upon Stress and Coping

ERIC Educational Resources Information Center

Bodenmann, Guy; Shantinath, S. D.

2004-01-01

We describe a distress prevention training program for couples and three empirical studies that support its effectiveness. The program, Couples Coping Enhancement Training (CCET), is based both upon stress and coping theory and research on couples. In addition to traditional elements of couples programs (e.g., communication and problem-solving…

A Randomized Controlled Trial of a Couple Relationship and Coparenting Program (Couple CARE for Parents) for High- and Low-Risk New Parents

ERIC Educational Resources Information Center

Petch, Jemima F.; Halford, W. Kim; Creedy, Debra K.; Gamble, Jenny

2012-01-01

Objective: This study evaluated the effectiveness of couple relationship education in assisting couples to sustain relationship functioning and parenting sensitivity, and whether benefits were moderated by risk of maladjustment in the transition to parenthood ("risk"). Method: Two hundred fifty couples expecting their first child were assessed on…

Influence of electrical coupling on early afterdepolarizations in ventricular myocytes.

PubMed

Saiz, J; Ferrero, J M; Monserrat, M; Ferrero, J M; Thakor, N V

1999-02-01

Computer modeling is used to study the effect of electrical coupling between a myocardial zone where early afterdepolarizations (EAD's) can develop and the normal neighboring tissue. The effects of such coupling on EAD development and on the likelihood of EAD propagation as an ectopic beat are studied. The influence on EAD formation is investigated by approximating two partially coupled myocardial zones modeled as two active elements coupled by a junctional resistance R. For R values lower than 800 omega cm2, the action potentials are transmitted to the coupled element, and for R values higher than 850 omega cm2 they are blocked. In both ranges of R, when the electrical coupling increases, the EAD's appear at more negative takeoff potentials with higher amplitudes and upstrokes. The EAD's are not elicited if the electrical coupling is too high. In a separate model of two one-dimensional cardiac fiber segments partially coupled by a resistance R, critical R values exist, between 42 and 54 omega cm2, that facilitate EAD propagation. These results demonstrate that in myocardial zones favorable to the formation of EAD, the electrical coupling dramatically affects initiation of EAD and its spread to the neighboring tissue.

Interface coupling-induced enhancement of magnetoimpedance effect in heterogeneous nanobrush by adjusting textures of Co nanowires

PubMed Central

2013-01-01

Interface coupling-induced and interface coupling-enhanced magnetoimpedance (MI) effect in heterogeneous nanobrush has been investigated. The nanobrush is composed of Fe25Ni75 nanofilm and textured hexagonal close-packed cobalt nanowire array, respectively fabricated by RF magnetron sputtering and electrochemical deposition. The design of this structure is based on the vortex distribution of magnetic moments in thin film, which can be induced by the exchange coupling effect at the interfaces of the nanobrush. The texture of nanowires plays an important role in the MI effect of the nanobrush, which is regulated by controlling the pH values and temperatures of the deposition process. The ‘parallel’ and ‘perpendicular’ coupling models were used to explain the different MI results of the nanobrush with cobalt nanowires, which have (100) and (002) textures, respectively. The optimized MI effect of the nanobrush brought by (100) nanowires can be magnified by 300% with more than 80%/Oe magnetic sensitivity at a low frequency, which has great application potentials in low-frequency MI sensors. PMID:24207011

Tunable plasmon-induced absorption effects in a graphene-based waveguide coupled with graphene ring resonators

NASA Astrophysics Data System (ADS)

Huang, Pei-Nian; Xia, Sheng-Xuan; Fu, Guang-Lai; Liang, Mei-Zhen; Qin, Meng; Zhai, Xiang; Wang, Ling-Ling

2018-03-01

In this paper, we propose a structure composed of two graphene waveguides and dual coupled graphene ring resonators (GRRs) to achieve a plasmon-induced absorption (PIA) effect. A three-level plasmonic system and a temporal coupled mode theory (CMT) are utilized to verify the simulation results. Moreover, a double-window-PIA effect can be conveniently attained by introducing another GRR with proper parameters to meet more specific acquirement in optical modulation process. The pronounced PIA resonances can be tuned in a number of ways, such as by adjusting the coupling distance between the GRRs and the couplings between the GRR and the waveguide, and tuning the radius and the Fermi energy of the GRRs. Besides, the produced PIA effect shows a high group delay up to - 1 . 87 ps, exhibiting a particularly prominent fast-light feature. Our results have potential applications in the realization of THz-integrated spectral control and graphene plasmonic devices such as sensors, filters, ultra-fast optical switches and so on.

Couple Relationship Functioning as a Source or Mitigator of HIV Risk: Associations Between Relationship Quality and Sexual Risk Behavior in Peri-urban Uganda.

PubMed

Ruark, Allison; Kajubi, Phoebe; Ruteikara, Sam; Green, Edward C; Hearst, Norman

2018-04-01

Despite evidence that a greater focus on couples could strengthen HIV prevention efforts, little health-related research has explored relationship functioning and relationship quality among couples in Africa. Using data from 162 couples (324 individuals) resident in a peri-urban Ugandan community, we assessed actor and partner effects of sexual risk behaviors on relationship quality, using psychometric measures of dyadic adjustment, sexual satisfaction, commitment, intimacy, and communication. For women and men, poor relationship quality was associated with having concurrent sexual partners and suspecting that one's partner had concurrent sexual partners (actor effects). Women's poor relationship quality was also associated with men's sexual risk behaviors (partner effects), although the inverse partner effect was not observed. These findings suggest that relationship quality is linked to HIV risk, particularly through the pathway of concurrent sexual partnerships, and that positive relationship attributes such as sexual satisfaction, intimacy, and constructive communication can help couples to avoid risk.

Domain size and structure in exchange coupled [Co/Pt]/NiO/[Co/Pt] multilayers.

PubMed

Baruth, A; Adenwalla, S

2011-09-21

We investigate the competing effects of interlayer exchange coupling and magnetostatic coupling in the magnetic heterostructure ([Co/Pt]/NiO/[Co/Pt]) with perpendicular magnetic anisotropy (PMA). This particular heterostructure is unique among coupled materials with PMA in directly exhibiting both ferromagnetic and antiferromagnetic coupling, oscillating between the two as a function of spacer layer thickness. By systematically tuning the coupling interactions via a wedge-shaped NiO spacer layer, we explore the energetics that dictate magnetic domain formation using high resolution magnetic force microscopy coupled with the magneto-optical Kerr effect. This technique probes the microscopic and macroscopic magnetic behavior as a continuous function of thickness and the interlayer exchange coupling, including the regions where interlayer coupling goes through zero. We see significant changes in domain structure based on the sign of coupling, and also show that magnetic domain size is directly related to the magnitude of the interlayer exchange coupling energy, which generally dominates over the magnetostatic interactions. When magnetostatic interactions become comparable to the interlayer exchange coupling, a delicate interplay between the differing energy contributions is apparent and energy scales are extracted. The results are of intense interest to the magnetic recording industry and also illustrate a relatively new avenue of undiscovered physics, primarily dealing with the delicate balance of energies in the formation of magnetic domains for coupled systems with PMA, defining limits on domain size as well as the interplay between roughness, domains and magnetic coupling.

Emotional Awareness and Couples' Relationship Satisfaction

ERIC Educational Resources Information Center

Croyle, Kristin L.; Waltz, Jennifer

2002-01-01

This study examined the role of emotional awareness in couples' relationships and the effects of a tendency to respond to difficult couples' situations with "soft" emotions (including sadness and fear) versus "hard" emotions (including anger and resentment). Participants were 56 heterosexual couples who completed a measure of relationship…

Size and Location of Defects at the Coupling Interface Affect Lithotripter Performance

PubMed Central

Li, Guangyan; Williams, James C.; Pishchalnikov, Yuri A.; Liu, Ziyue; McAteer, James A.

2012-01-01

OBJECTIVE To determine how the size and location of coupling defects caught between the therapy head of a lithotripter and the skin of a surrogate patient (acoustic window of a test chamber) affect the features of shock waves responsible for stone breakage. METHODS Model defects were placed in the coupling gel between the therapy head of a Dornier Compact-S electromagnetic lithotripter and the Mylar window of a water-filled coupling test system. A fiber-optic hydrophone was used to measure acoustic pressures and map the lateral dimensions of the focal zone of the lithotripter. The effect of coupling conditions on stone breakage was assessed using Gypsum model stones. RESULTS Stone breakage decreased in proportion to the area of the coupling defect; a centrally located defect blocking only 18% of the transmission area reduced stone breakage by an average of almost 30%. The effect on stone breakage was greater for defects located on-axis and decreased as the defect was moved laterally; an 18% defect located near the periphery of the coupling window (2.0 cm off-axis) reduced stone breakage by only ~15% compared to when coupling was completely unobstructed. Defects centered within the coupling window acted to narrow the focal width of the lithotripter; an 8.2% defect reduced the focal width ~30% compared to no obstruction (4.4 mm versus 6.5 mm). Coupling defects located slightly off center disrupted the symmetry of the acoustic field; an 18% defect positioned 1.0 cm off-axis shifted the focus of maximum positive pressure ~1.0 mm laterally. Defects on and off-axis imposed a significant reduction in the energy density of shock waves across the focal zone. CONCLUSIONS In addition to blocking the transmission of shock wave energy, coupling defects also disrupt the properties of shock waves that play a role in stone breakage, including the focal width of the lithotripter and the symmetry of the acoustic field; the effect is dependent on the size and location of defects, with defects near the center of the coupling window having the greatest effect. These data emphasize the importance of eliminating air pockets from the coupling interface, particularly defects located near the center of the coupling window. PMID:22938566

Integration of a waveguide self-electrooptic effect device and a vertically coupled interconnect waveguide

DOEpatents

Vawter, G Allen [Corrales, NM

2008-02-26

A self-electrooptic effect device ("SEED") is integrated with waveguide interconnects through the use of vertical directional couplers. Light initially propagating in the interconnect waveguide is vertically coupled to the active waveguide layer of the SEED and, if the SEED is in the transparent state, the light is coupled back to the interconnect waveguide.

Effects of shear coupling on shear properties of wood

Treesearch

Jen Y. Liu

2000-01-01

Under pure shear loading, an off-axis element of orthotropic material such as pure wood undergoes both shear and normal deformations. The ratio of the shear strain to a normal strain is defined as the shear coupling coefficient associated with the direction of the normal strain. The effects of shear coupling on shear properties of wood as predicted by the orthotropic...

Design and development of ultra-wideband 3 dB hybrid coupler for Ion cyclotron resonance frequency heating in tokamak.

PubMed

Yadav, Rana Pratap; Kumar, Sunil; Kulkarni, S V

2014-04-01

Design and development of a high power ultra-wideband, 3 dB tandem hybrid coupler is presented and its application in ICRF heating of the tokamak is discussed. In order to achieve the desired frequency band of 38-112 MHz and 200 kW power handling capability, the 3 dB hybrid coupler is developed using two 3-element 8.34 ± 0.2 dB coupled lines sections in tandem. In multi-element coupled lines, junctions are employed for the joining of coupled elements that produce the undesirable reactance called junction discontinuity effect. The effect becomes prominent in the high power multi-element coupled lines for high frequency (HF) and very high frequency(VHF) applications because of larger structural dimensions. Junction discontinuity effect significantly deteriorates coupling and output performance from the theoretical predictions. For the analysis of junction discontinuity effect and its compensation, a theoretical approach has been developed and generalized for n-element coupled lines section. The theory has been applied in the development of the 3 dB hybrid coupler. The fabricated hybrid coupler has been experimentally characterized using vector network analyzer and obtained results are found in good agreement with developed theory.

Many-body effects and ultraviolet renormalization in three-dimensional Dirac materials

NASA Astrophysics Data System (ADS)

Throckmorton, Robert; Hofmann, Johannes; Barnes, Edwin

We develop a theory for electron-electron interaction-induced many-body effects in three dimensional (3D) Weyl or Dirac semimetals, including interaction corrections to the polarizability, electron self-energy, and vertex function, up to second order in the effective fine structure constant of the Dirac material. These results are used to derive the higher-order ultraviolet renormalization of the Fermi velocity, effective coupling, and quasiparticle residue, revealing that the corrections to the renormalization group (RG) flows of both the velocity and coupling counteract the leading-order tendencies of velocity enhancement and coupling suppression at low energies. This in turn leads to the emergence of a critical coupling above which the interaction strength grows with decreasing energy scale. In addition, we identify a range of coupling strengths below the critical point in which the Fermi velocity varies non-monotonically as the low-energy, non-interacting fixed point is approached. Furthermore, we find that while the higher-order correction to the flow of the coupling is generally small compared to the leading order, the corresponding correction to the velocity flow carries an additional factor of the Dirac cone flavor number relative to the leading-order result. Supported by LPS-MPO-CMTC.

Coupling UV-H2O2 to accelerate dimethyl phthalate (DMP) biodegradation and oxidation.

PubMed

Chen, Bin; Song, Jiaxiu; Yang, Lihui; Bai, Qi; Li, Rongjie; Zhang, Yongming; Rittmann, Bruce E

2015-11-01

Dimethyl phthalate (DMP), an important industrial raw material, is an endocrine disruptor of concern for human and environmental health. DMP exhibits slow biodegradation, and its coupled treatment by means of advanced oxidation may enhance its biotransformation and mineralization. We evaluated two ways of coupling UV-H2O2 advanced oxidation to biodegradation: sequential coupling and intimate coupling in an internal circulation baffled biofilm reactor (ICBBR). During sequential coupling, UV-H2O2 pretreatment generated carboxylic acids that depressed the pH, and subsequent biodegradation generated phthalic acid; both factors inhibited DMP biodegradation. During intimately coupled UV-H2O2 with biodegradation, carboxylic acids and phthalic acid (PA) did not accumulate, and the biodegradation rate was 13 % faster than with biodegradation alone and 78 % faster than with biodegradation after UV-H2O2 pretreatment. Similarly, DMP oxidation with intimate coupling increased by 5 and 39 %, respectively, compared with biodegradation alone and sequential coupling. The enhancement effects during intimate coupling can be attributed to the rapid catabolism of carboxylic acids, which generated intracellular electron carriers that directly accelerated di-oxygenation of PA and relieved the inhibition effect of PA and low pH. Thus, intimate coupling optimized the impacts of energy input from UV irradiation used together with biodegradation.

RF verification tasks underway at the Harris Corporation for multiple aperture reflector system

NASA Technical Reports Server (NTRS)

Gutwein, T. A.

1982-01-01

Mesh effects on gain and patterns and adjacent aperture coupling effects for "pie" and circular apertures are discussed. Wire effects for Harris model with Langley scale model results included for assessing D/lamda effects, and wire effects with adjacent aperture coupling were determined. Reflector surface distortion effects (pillows and manufacturing roughness) were studied.

Tools and techniques for estimating high intensity RF effects

NASA Astrophysics Data System (ADS)

Zacharias, Richard L.; Pennock, Steve T.; Poggio, Andrew J.; Ray, Scott L.

1992-01-01

Tools and techniques for estimating and measuring coupling and component disturbance for avionics and electronic controls are described. A finite-difference-time-domain (FD-TD) modeling code, TSAR, used to predict coupling is described. This code can quickly generate a mesh model to represent the test object. Some recent applications as well as the advantages and limitations of using such a code are described. Facilities and techniques for making low-power coupling measurements and for making direct injection test measurements of device disturbance are also described. Some scaling laws for coupling and device effects are presented. A method for extrapolating these low-power test results to high-power full-system effects are presented.

FAST TRACK COMMUNICATION: Interlayer exchange coupling across a ferroelectric barrier

NASA Astrophysics Data System (ADS)

Zhuravlev, M. Ye; Vedyayev, A. V.; Tsymbal, E. Y.

2010-09-01

A new magnetoelectric effect is predicted originating from the interlayer exchange coupling between two ferromagnetic layers separated by an ultrathin ferroelectric barrier. It is demonstrated that ferroelectric polarization switching driven by an external electric field leads to a sizable change in the interlayer exchange coupling. The effect occurs in asymmetric ferromagnet/ferroelectric/ferromagnet junctions due to a change in the electrostatic potential profile across the junction affecting the interlayer coupling. The predicted phenomenon indicates the possibility of switching the magnetic configuration by reversing the polarization of the ferroelectric barrier layer.

Conductor disc used to suppress spurious mode and enhance electric coupling in a dielectric loaded combline resonator

NASA Astrophysics Data System (ADS)

Pholele, T. M.; Chuma, J. M.

2016-03-01

The effects of conductor disc in a dielectric loaded combline resonator on its spurious performance, unloaded quality factor (Qu), and coupling coefficients are analysed using a commercial electromagnetic software package CST Microwave Studio (CST MWS). The disc improves the spurious free band but simultaneously deteriorates the Qu. The presence of the disc substantially improves the electric coupling by a factor of 1.891 for an aperture opening of 12 mm, while it has insignificant effect on the magnetic coupling.

Normal-Mode Splitting in a Weakly Coupled Optomechanical System

NASA Astrophysics Data System (ADS)

Rossi, Massimiliano; Kralj, Nenad; Zippilli, Stefano; Natali, Riccardo; Borrielli, Antonio; Pandraud, Gregory; Serra, Enrico; Di Giuseppe, Giovanni; Vitali, David

2018-02-01

Normal-mode splitting is the most evident signature of strong coupling between two interacting subsystems. It occurs when two subsystems exchange energy between themselves faster than they dissipate it to the environment. Here we experimentally show that a weakly coupled optomechanical system at room temperature can manifest normal-mode splitting when the pump field fluctuations are antisquashed by a phase-sensitive feedback loop operating close to its instability threshold. Under these conditions the optical cavity exhibits an effectively reduced decay rate, so that the system is effectively promoted to the strong coupling regime.

On the Nonequilibrium Interface Kinetics of Rapid Coupled Eutectic Growth

NASA Astrophysics Data System (ADS)

Dong, H.; Chen, Y. Z.; Shan, G. B.; Zhang, Z. R.; Liu, F.

2017-08-01

Nonequilibrium interface kinetics (NEIK) is expected to play an important role in coupled growth of eutectic alloys, when solidification velocity is high and intermetallic compound or topologically complex phases form in the crystallized product. In order to quantitatively evaluate the effect of NEIK on the rapid coupled eutectic growth, in this work, two nonequilibrium interface kinetic effects, i.e., atom attachment and solute trapping at the solid-liquid interface, were incorporated into the analyses of the coupled eutectic growth under the rapid solidification condition. First, a coupled growth model incorporating the preceding two nonequilibrium kinetic effects was derived. On this basis, an expression of kinetic undercooling (Δ T k), which is used to characterize the NEIK, was defined. The calculations based on the as-derived couple growth model show good agreement with the reported experimental results achieved in rapidly solidified eutectic Al-Sm alloys consisting of a solid solution phase ( α-Al) and an intermetallic compound phase (Al11Sm3). In terms of the definition of Δ T k defined in this work, the role of NEIK in the coupled growth of the Al-Sm eutectic system was analyzed. The results show that with increasing the coupled growth velocity, Δ T k increases continuously, and its ratio to the total undercooling reaches 0.32 at the maximum growth velocity for coupled eutectic growth. Parametric analyses on two key alloy parameters that influence Δ T k, i.e., interface kinetic parameter ( μ i ) and solute distribution coefficient ( k e ), indicate that both μ i and k e influence the NEIK significantly and the decrease of either these two parameters enhances the NEIK effect.

The recent progress in research on effects of anesthetics and analgesics on G protein-coupled receptors.

PubMed

Minami, Kouichiro; Uezono, Yasuhito

2013-04-01

The exact mechanisms of action behind anesthetics and analgesics are still unclear. Much attention was focused on ion channels in the central nervous system as targets for anesthetics and analgesics in the 1980s. During the 1990s, major advances were made in our understanding of the physiology and pharmacology of G protein coupled receptor (GPCR) signaling. Thus, several lines of studies have shown that G protein coupled receptors (GPCRs) are one of the targets for anesthetics and analgesics and especially, that some of them inhibit the functions of GPCRs, i.e,, muscarinic receptors and substance P receptors. However, these studies had been focused on only G(q) coupled receptors. There has been little work on G(s)- and G(i)-coupled receptors. In the last decade, a new assay system, using chimera G(i/o)-coupled receptor fused to Gq(i5), has been established and the effects of anesthetics and analgesics on the function of G(i)-coupled receptors is now more easily studied. This review highlights the recent progress of the studies regarding the effects of anesthetics and analgesics on GPCRs.

40 CFR 201.15 - Standard for car coupling operations.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 25 2011-07-01 2011-07-01 false Standard for car coupling operations... Interstate Rail Carrier Operations Standards § 201.15 Standard for car coupling operations. Effective January 15, 1984, no carrier subject to this regulation shall conduct car coupling operations that exceed an...

40 CFR 201.15 - Standard for car coupling operations.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 26 2013-07-01 2013-07-01 false Standard for car coupling operations... Interstate Rail Carrier Operations Standards § 201.15 Standard for car coupling operations. Effective January 15, 1984, no carrier subject to this regulation shall conduct car coupling operations that exceed an...

40 CFR 201.15 - Standard for car coupling operations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 25 2014-07-01 2014-07-01 false Standard for car coupling operations... Interstate Rail Carrier Operations Standards § 201.15 Standard for car coupling operations. Effective January 15, 1984, no carrier subject to this regulation shall conduct car coupling operations that exceed an...

40 CFR 201.15 - Standard for car coupling operations.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 26 2012-07-01 2011-07-01 true Standard for car coupling operations... Interstate Rail Carrier Operations Standards § 201.15 Standard for car coupling operations. Effective January 15, 1984, no carrier subject to this regulation shall conduct car coupling operations that exceed an...

40 CFR 201.15 - Standard for car coupling operations.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Standard for car coupling operations... Interstate Rail Carrier Operations Standards § 201.15 Standard for car coupling operations. Effective January 15, 1984, no carrier subject to this regulation shall conduct car coupling operations that exceed an...

On coupling NEC-violating matter to gravity

DOE PAGES

Chatterjee, Saugata; Parikh, Maulik; van der Schaar, Jan Pieter

2015-03-16

We show that effective theories of matter that classically violate the null energy condition cannot be minimally coupled to Einstein gravity without being inconsistent with both string theory and black hole thermodynamics. We argue however that they could still be either non-minimally coupled or coupled to higher-curvature theories of gravity.

The precarious couple effect: verbally inhibited men + critical, disinhibited women = bad chemistry.

PubMed

Swann, William B; Rentfrow, Peter J; Gosling, Samuel D

2003-12-01

When critical, verbally disinhibited women are paired with verbally inhibited men, relationship quality suffers, rendering the relationship precarious. This effect theoretically emerges when (a). verbally disinhibited women pair with relatively inhibited men (man-more-inhibited couples) and (b). the disinhibition of women in man-more-inhibited couples amplifies women's criticalness and alienates men. Three studies (Ns=437, 300, and 564) provided evidence that relationship quality suffered in man-more-inhibited couples; a 4th study (N=168) showed that the criticalness of women in man-more-inhibited couples did indeed undermine relationship quality. Implications for understanding the impact of gender expectations on relationships and for integrating behavioral and personological approaches to close relationships are discussed.

Synchronization behaviors of coupled neurons under electromagnetic radiation

NASA Astrophysics Data System (ADS)

Ma, Jun; Wu, Fuqiang; Wang, Chunni

2017-01-01

Based on an improved neuronal model, in which the effect of magnetic flux is considered during the fluctuation and change of ion concentration in cells, the transition of synchronization is investigated by imposing external electromagnetic radiation on the coupled neurons, and networks, respectively. It is found that the synchronization degree depends on the coupling intensity and the intensity of external electromagnetic radiation. Indeed, appropriate intensity of electromagnetic radiation could be effective to realize intermittent synchronization, while stronger intensity of electromagnetic radiation can induce disorder of coupled neurons and network. Neurons show rhythm synchronization in the electrical activities by increasing the coupling intensity under electromagnetic radiation, and spatial patterns can be formed in the network under smaller factor of synchronization.

A Randomized Controlled Trial of the Web-Based OurRelationship Program: Effects on Relationship and Individual Functioning

PubMed Central

Doss, Brian D.; Cicila, Larisa N.; Georgia, Emily J.; Roddy, McKenzie K.; Nowlan, Kathryn M.; Benson, Lisa A.; Christensen, Andrew

2016-01-01

Objective Within the United States, one-third of married couples are distressed and almost half of first marriages (and more than half of unmarried cohabiting relationships) end in divorce/separation. Additionally, relationship distress has been linked to mental and physical health problems in partners and their children. Although couple therapy is effective in reducing relationship distress, it is utilized by less than one third of divorcing couples. Therefore, more accessible interventions for relationship distress are needed. Method This study tests the efficacy of the OurRelationship (OR) program, an eight-hour online program adapted from an empirically-based, in-person couple therapy. In the program, couples complete online activities and have four, 15-minute calls with project staff. Nationwide, 300 heterosexual couples (N = 600 participants) participated; couples were generally representative of the US in terms of race, ethnicity, and education. Couples were randomly assigned to begin the program immediately or to a two month waitlist control group. Results Compared to the waitlist group, intervention couples reported significant improvements in relationship satisfaction (Cohen’s d=0.69), relationship confidence (d=0.47), and negative relationship quality (d=0.57). Additionally, couples reported significant improvements in multiple domains of individual functioning, especially when individuals began the program with difficulties in that domain: depressive (d=0.71) and anxious symptoms (d=0.94), perceived health (d=0.51), work functioning (d=0.57), and quality of life (d=0.44). Conclusions In a nationally-representative sample of couples, the OR program was effective in significantly improving both relationship and individual functioning, suggesting it can substantially increase the reach of current interventions through its low-cost, web-based format. PMID:26999504

Triple-effect absorption refrigeration system with double-condenser coupling

DOEpatents

DeVault, R.C.; Biermann, W.J.

1993-04-27

A triple effect absorption refrigeration system is provided with a double-condenser coupling and a parallel or series circuit for feeding the refrigerant-containing absorbent solution through the high, medium, and low temperature generators utilized in the triple-effect system. The high temperature condenser receiving vaporous refrigerant from the high temperature generator is double coupled to both the medium temperature generator and the low temperature generator to enhance the internal recovery of heat within the system and thereby increase the thermal efficiency thereof.

Triple-effect absorption refrigeration system with double-condenser coupling

DOEpatents

DeVault, Robert C.; Biermann, Wendell J.

1993-01-01

A triple effect absorption refrigeration system is provided with a double-condenser coupling and a parallel or series circuit for feeding the refrigerant-containing absorbent solution through the high, medium, and low temperature generators utilized in the triple-effect system. The high temperature condenser receiving vaporous refrigerant from the high temperature generator is double coupled to both the medium temperature generator and the low temperature generator to enhance the internal recovery of heat within the system and thereby increase the thermal efficiency thereof.

Determination of coupling coefficients at various zenith angles of the basis of the cosmic ray azimuth effect

NASA Technical Reports Server (NTRS)

Belskiy, S. A.; Dmitriev, B. A.; Romanov, A. M.

1975-01-01

The value of EW asymmetry and coupling coefficients at different zenith angles were measured by means of a double coincidence crossed telescope which gives an opportunity to measure simultaneously the intensity of the cosmic ray hard component at zenith angles from 0 to 84 deg in opposite azimuths. The advantages of determining the coupling coefficients by the cosmic ray azimuth effect as compared to their measurement by the latitudinal effect are discussed.

Cyclic Voltammetric Wave-Shapes for Microdisk Electrodes: Coupled Effects of Solution Resistance, Double-Layer Capacitance, and Finite Electrochemical Kinetics

DTIC Science & Technology

1991-05-01

vaveshapea. While the use of high scan rates enhances the effect of electrode kinetics upon the voltametry , the deleterious coupled influence of pa 20...waveshapes. While the use of high scan rates enhances the effect of electrode kinetics upon the voltametry , the deleterious coupled influence of P...2 1 󈧚 Aoki et al have in- 23 vestigated linear sweep voltammetry at microdisks in the reversible case, and Zoski and co-workers have developed

The effect of hot phonons and coupled phonon-plasmon modes on scattering-induced NDR in quantum wells

NASA Astrophysics Data System (ADS)

Ridley, B. K.; Al-Mudares, M.

1988-04-01

We have extended our Monte Carlo simulation of scattering-induced NDR in Al. 8Ga 2As/GaAs quantum wells by including (a) the effect of hot phonons (b) coupled phonon-plasmon modes (c) degeneracy. Hot phonons were modelled using a phenomenological lifetime which we ranged from 3ps to 10ps. Coupled modes were modelled in the antiscreening approximation. Bulk-like modes were assumed in both cases. NDR is quenched if the phonon lifetime exceeds 7ps, but is little affected if the lifetime is 3ps. The effect of coupled modes is appreciable at a doping density of 10 18cm -3, virtually eliminating NDR, but at 10 17cm -3 the effect is much smaller. Including degeneracy has only a small effect on the results. We conclude that NDR is still possible at electron densities around 10 17cm -3.

The Experience of Couples in the Process of Treatment of Pathological Gambling: Couple vs. Individual Therapy.

PubMed

Tremblay, Joël; Dufour, Magali; Bertrand, Karine; Blanchette-Martin, Nadine; Ferland, Francine; Savard, Annie-Claude; Saint-Jacques, Marianne; Côté, Mélissa

2017-01-01

Context: Couple treatment for pathological gambling is an innovative strategy. There are some results supporting its potential effectiveness, but little is known about the subjective experiences of the participants. Objective: The aim of this article is to document the experiences of gamblers and their partners participating in one of two treatments, namely individual or couple. Method: In a study aiming to evaluate the efficacy of the Integrative Couple Treatment for Pathological Gambling (ICT-PG), couples who were entering specialized treatment for the addiction of one member who was a pathological gambler were randomly assigned to individual or ICT-PG. Nine months after their admission to treatment, gamblers and partners ( n = 21 couples; n = 13 ICT-PG; n = 8 individual treatment) were interviewed in semi-structured interviews. A sequenced thematization method was used to extract the major themes. Results: This study highlighted five major themes in the therapeutic process noted by the gamblers and their partners mainly after the couple treatment but also partly through the individual therapy. These were: (1) the gamblers' anxiety about having to reveal their gambling problems in couple therapy; (2) the wish to develop a mutually beneficial understanding of gambling and its effects on the partners in the two types of treatments; (3) the transformation of negative attributions through a more effective intra-couple communication fostered by the couple therapy; (4) the partners' contribution to changes in gambling behavior and prevention of relapses, which were both better supported in couple therapy; and (5) the interpersonal nature of gambling and its connections with the couples' relationship. However, gamblers who were in individual treatment were more likely to mention that their partners' involvement was not necessary. Participants likewise made a few recommendations about the conditions underlying the choice of one treatment method or the other. Discussion: Participants reported satisfaction with both treatment models, but their experience was more positive in couple treatment. Complementary benefits emerged from each form of treatment, which points to future treatments involving both types. Future research should explore both the couple processes associated with attempts to stop pathological gambling and the various ways of involving partners in the gamblers' treatment.

The Experience of Couples in the Process of Treatment of Pathological Gambling: Couple vs. Individual Therapy

PubMed Central

Tremblay, Joël; Dufour, Magali; Bertrand, Karine; Blanchette-Martin, Nadine; Ferland, Francine; Savard, Annie-Claude; Saint-Jacques, Marianne; Côté, Mélissa

2018-01-01

Context: Couple treatment for pathological gambling is an innovative strategy. There are some results supporting its potential effectiveness, but little is known about the subjective experiences of the participants. Objective: The aim of this article is to document the experiences of gamblers and their partners participating in one of two treatments, namely individual or couple. Method: In a study aiming to evaluate the efficacy of the Integrative Couple Treatment for Pathological Gambling (ICT-PG), couples who were entering specialized treatment for the addiction of one member who was a pathological gambler were randomly assigned to individual or ICT-PG. Nine months after their admission to treatment, gamblers and partners (n = 21 couples; n = 13 ICT-PG; n = 8 individual treatment) were interviewed in semi-structured interviews. A sequenced thematization method was used to extract the major themes. Results: This study highlighted five major themes in the therapeutic process noted by the gamblers and their partners mainly after the couple treatment but also partly through the individual therapy. These were: (1) the gamblers' anxiety about having to reveal their gambling problems in couple therapy; (2) the wish to develop a mutually beneficial understanding of gambling and its effects on the partners in the two types of treatments; (3) the transformation of negative attributions through a more effective intra-couple communication fostered by the couple therapy; (4) the partners' contribution to changes in gambling behavior and prevention of relapses, which were both better supported in couple therapy; and (5) the interpersonal nature of gambling and its connections with the couples' relationship. However, gamblers who were in individual treatment were more likely to mention that their partners' involvement was not necessary. Participants likewise made a few recommendations about the conditions underlying the choice of one treatment method or the other. Discussion: Participants reported satisfaction with both treatment models, but their experience was more positive in couple treatment. Complementary benefits emerged from each form of treatment, which points to future treatments involving both types. Future research should explore both the couple processes associated with attempts to stop pathological gambling and the various ways of involving partners in the gamblers' treatment. PMID:29416520

Who’s Asking the Important Questions? Sexual Topics Discussed among Young Pregnant Couples

PubMed Central

Albritton, Tashuna; Day, Kyla M.; Divney, Anna; Gordon, Derrick; Magriples, Urania; Kershaw, Trace S.

2013-01-01

Purpose The aim was to examine gender differences in sexual risk communication among young couples and factors influencing communication. Methods Sample consisted of 296 young pregnant couples. We assessed individual, interpersonal, and community factors on sexual risk communication. The Actor-Partner Independence Model was used to assess actor and partner effects on sexual risk communication. Results For actor effects, being female, older, not being Hispanic, and higher condom use self-efficacy was associated with sexual risk communication. The significant partner effect was avoidant romantic attachment. Gender interactions were significant for high risk behaviors and family functioning. High risk behaviors and family functioning were associated with sexual risk communication for females but not for males. Conclusion The study emphasizes the need to promote sexual risk communication among young high risk couples, particularly for males. Family support could serve as a catalyst for sexual risk communication and other sexual protective behaviors among young couples. PMID:24043405

Protecting coherence by environmental decoherence: a solvable paradigmatic model

NASA Astrophysics Data System (ADS)

Torres, Juan Mauricio; Seligman, Thomas H.

2017-11-01

We consider a particularly simple exactly solvable model for a qubit coupled to sequentially nested environments. The purpose is to exemplify the coherence conserving effect of a central system, that has been reported as a result of increasing the coupling between near and far environment. The paradigmatic example is the Jaynes-Cummings Hamiltonian, which we introduce into a Kossakowski-Lindblad master equation using alternatively the lowering operator of the oscillator or its number operator as Lindblad operators. The harmonic oscillator is regarded as the near environment of the qubit, while effects of a far environment are accounted for by the two options for the dissipative part of the master equation. The exact solution allows us to cover the entire range of coupling strength from the perturbative regime to strong coupling analytically. The coherence conserving effect of the coupling to the far environment is confirmed throughout.

Is Communication a Mechanism of Relationship Education Effects among Rural African Americans?

PubMed

Barton, Allen W; Beach, Steven R H; Lavner, Justin A; Bryant, Chalandra M; Kogan, Steven M; Brody, Gene H

2017-10-01

Enhancing communication as a means of promoting relationship quality has been increasingly questioned, particularly for couples at elevated sociodemographic risk. In response, the current study investigated communication change as a mechanism accounting for changes in relationship satisfaction and confidence among 344 rural, predominantly low-income African American couples with an early adolescent child who participated in a randomized controlled trial of the Protecting Strong African American Families (ProSAAF) program. Approximately 9 months after baseline assessment, intent-to-treat analyses indicated ProSAAF couples demonstrated improved communication, satisfaction, and confidence compared with couples in the control condition. Improvements in communication mediated ProSAAF effects on relationship satisfaction and confidence; conversely, neither satisfaction nor confidence mediated intervention effects on changes in communication. These results underscore the short-term efficacy of a communication-focused, culturally sensitive prevention program and suggest that communication is a possible mechanism of change in relationship quality among low-income African American couples.

Effects of (un)employment on young couples' health and life satisfaction.

PubMed

Haid, Marja-Lena; Seiffge-Krenke, Inge

2013-01-01

This study investigated effects of employed and unemployed job status on health outcomes with questionnaires in 50 young couples. Analysis of variance revealed higher pessimism, higher stress levels, and lower life satisfaction in couples in which one partner was unemployed. These couples also exhibited more health risk behaviours compared to couples in which both partners were working. The dyadic analysis of data, using an actor-partner interdependence model, demonstrated strong actor and partner effects for male partner's job status. Being unemployed was significantly associated not only with male partner's life satisfaction but also with the life satisfaction of his female partner. In addition, male partner's pessimism was identified as a significant variable which mediates between male partner's job status and female partner's life satisfaction. The study highlights the relevance of the accomplishment of tasks in the domains of work and partnership during young adulthood and it emphasises the gender specific importance.

Assisting couples to develop healthy relationships: effects of couples relationship education on cortisol.

PubMed

Ditzen, Beate; Hahlweg, Kurt; Fehm-Wolfsdorf, Gabriele; Baucom, Don

2011-06-01

Couple conflict in unhappy marriages is suggested to impair individual health via chronic psychophysiological stress reactions in couples' everyday lives. As a consequence, we hypothesized that standard couples relationship education (CRE) would decrease psychophysiological stress, namely salivary cortisol levels, during couple conflict in the laboratory as compared to a standard psychological stress paradigm. We considered cortisol to be of particular interest in this context, as it mediates endocrine and immune responses to stress, and thus might influence couples' health. Salivary cortisol was repeatedly investigated in 61 couples during (a) a standard psychological stress test with no relevance for the couples, and (b) a standard couple conflict discussion in the laboratory before and after CRE. In addition, increases in self-evaluated relationship quality were analyzed with regard to their influence on salivary cortisol. Data were analyzed using multilevel modeling. Cortisol responses to the couple-external psychological stress test were unaffected by CRE, but specifically cortisol responses during the couple conflict discussion were significantly reduced following CRE compared to pre-intervention levels. Moreover, cortisol decreases during conflict were partially mediated by increases in self-reported relationship quality following CRE. These data suggest that CRE might buffer the harmful effects of repeated conflict in close relationships. Rather than ameliorating overall stress resilience, CRE might thus specifically improve individual health through increased relationship quality and reduced HPA axis activity during couple conflict. Copyright © 2010 Elsevier Ltd. All rights reserved.

Round window stimulation with the Vibrant Soundbridge: Comparison of direct and indirect coupling.

PubMed

Olszewski, Lukasz; Jedrzejczak, W Wiktor; Piotrowska, Anna; Skarzynski, Henryk

2017-12-01

The purpose of this study was to measure the degree of coupling between the floating mass transducer (FMT) and the round window membrane (RWM) in patients with conductive and mixed hearing loss implanted with the Vibrant Soundbridge (VSB) device. The efficiency of direct and indirect coupling of the FMT to the RWM was compared by measuring differences between the initial prescription targets and the final settings of the VSB audio processor after fine-tuning. Retrospective study. Investigation of a group of subjects with either conductive or mixed hearing loss implanted with the VSB, a device that uses a FMT coupled to the RWM. There were two subgroups: subjects in which coupling was direct (no interposed material) or indirect (interposed material). The functional gain, insertion gain, and compression characteristics of the device were measured to assess the efficiency of coupling and to investigate the proximity of the fitting to prescriptive targets. Coupling for the subgroup with indirect coupling of the RWM was higher (better) than for the subgroup with direct coupling. The gain deviation from prescriptive targets was smaller for the subgroup with indirect coupling. The coupling method can have an effect on the coupling efficiency and the final electroacoustic settings of the device. The prescription targets were not accurate for the majority of subjects from either subgroup. Indirect coupling appears to provide more effective stimulation of the cochlea. 4. Laryngoscope, 127:2843-2849, 2017. © 2017 The American Laryngological, Rhinological and Otological Society, Inc.

Divorce and subsequent increase in uptake of antidepressant medication: a Finnish registry-based study on couple versus individual effects.

PubMed

Monden, Christiaan W S; Metsä-Simola, Niina; Saarioja, Saska; Martikainen, Pekka

2015-02-19

There is an average negative mental health effect for individuals who experience divorce. Little is known whether the pattern of such divorce effects varies within couples. We study whether the husband and wife experience similar harmful effects of divorce, whether they experience opposite effects, or whether divorce effects are purely individual. We use Finnish registry data to compare changes over a period of 5 years in antidepressant use of husbands and wives from 4,558 divorcing couples to 108,637 continuously married pairs aged 40-64, all of whom were healthy at baseline. In the period three years before and after divorce antidepressant use increases substantially. However, the likelihood of uptake of antidepressant medication during this process of divorce by one partner appears to be independent of medication uptake in the other partner. In contrast, among continuously married couples there is a clear pattern of convergence: If one partner starts to use antidepressants this increases the likelihood of uptake of antidepressant medication in the other partner. Our findings suggest that divorce effects on antidepressant use are individual and show no pattern of either convergence or divergence at the level of the couple. The increased incidence of antidepressant use associated with divorce occurs in individuals independent of what happens to their ex-partner.

Effect of capping layer on interlayer coupling in synthetic spin valves

NASA Astrophysics Data System (ADS)

Li, Kebin; Qiu, Jinjun; Han, Guchang; Guo, Zaibing; Zheng, Yuankai; Wu, Yihong; Li, Jinshan

2005-01-01

The magnetic and transport properties of high quality synthetic spin-valves with the structure of Ta/NiFe/IrMn/CoFe/Ru/CoFe/NOL/CoFe/Cu/CoFe/CL were studied by using magnetoresistance measurements. Here Ti, Hf, and Al are used as the capping layer. It is found that both the thickness and materials properties of the capping layers can affect the interlayer coupling field. The interlayer coupling field oscillates weakly with respect to the thickness of the Ti and Hf capping layers. Extremely strong ferromagnetic coupling has been observed when the thickness of the Al capping layer is in a certain range where resonant exchange coupling takes place. The strength of the interlayer coupling is inversely proportional to the square of the thickness of the spacer. It is a typical characteristic of quantum size effect.

Cooperative effect of random and time-periodic coupling strength on synchronization transitions in one-way coupled neural system: mean field approach.

PubMed

Jiancheng, Shi; Min, Luo; Chusheng, Huang

2017-08-01

The cooperative effect of random coupling strength and time-periodic coupling strengh on synchronization transitions in one-way coupled neural system has been investigated by mean field approach. Results show that cooperative coupling strength (CCS) plays an active role for the enhancement of synchronization transitions. There exist an optimal frequency of CCS which makes the system display the best CCS-induced synchronization transitions, a critical frequency of CCS which can not further affect the CCS-induced synchronization transitions, and a critical amplitude of CCS which can not occur the CCS-induced synchronization transitions. Meanwhile, noise intensity plays a negative role for the CCS-induced synchronization transitions. Furthermore, it is found that the novel CCS amplitude-induced synchronization transitions and CCS frequency-induced synchronization transitions are found.

Coupling Resonances of Surface Plasmon in Gold Nanorod/Copper Chalcogenide Core-Shell Nanostructures and Their Enhanced Photothermal Effect.

PubMed

Li, Yingying; Pan, Guiming; Liu, Qiyu; Ma, Liang; Xie, Ying; Zhou, Li; Hao, Zhonghua; Wang, Ququan

2018-06-04

Dual plasmonic Au@Cu 2-x S core-shell nanorods (NRs) have been fabricated by using a hydrothermal method and plasmon-coupled effect between the Au core and Cu 2-x S shell in the near-infrared (NIR) region. The extinction spectrum of Au@Cu 2-x S NRs is dominated by the surface plasmon resonance (SPR) of the Cu 2-x S shell, the transverse surface plasmon resonance (TSPR), and the longitudinal surface plasmon resonance (LSPR) of the Au NRs. With the Cu 2-x S shell increasing (fixed Au NRs), the TSPR peak slightly redshifts and the LSPR and SPR peaks blueshift, owing to competition between the redshift of the refractive index effect and blueshift from the plasmon coupled effect. Although, for Au@Cu 2 S NRs, only TSPR and LSPR peaks can be seen and a redshift arises with the increasing Cu 2 S shell thickness, implying that no plasmonic coupling between Au NRs and Cu 2 S shell occurred. The extinction spectrum of the Au@Cu 2-x S NRs with three coupled resonance peaks is simulated by using the FDTD method, taking into account the electron-transfer effect. The dispersion properties of the coupling of Au@Cu 2-x S NRs with the LSPR of the initial Au core are studied experimentally by changing the length of the Au NRs, which are explained theoretically by the coupled harmonic oscillator model. The calculated coupled coefficients between SPR of the Cu 2-x S shell and LSPR of the Au NRs is 180 meV, which is much stronger than that of TSPR of Au NRs of 55 meV. Finally, the enhanced photothermal effect of Au@Cu 2-x S NRs has been demonstrated. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A general analysis of Wtb anomalous couplings

NASA Astrophysics Data System (ADS)

Cao, Qing-Hong; Yan, Bin; Yu, Jiang-Hao; Zhang, Chen

2017-06-01

We investigate new physics effects on the Wtb effective couplings in a model-independent framework. The new physics effects can be parametrized by four independent couplings, , , and . We further introduce a set of parameters x 0, x m , x p and x 5 which exhibit a linear relation to the single top production cross sections. Using recent data for the t-channel single top production cross section σ t , tW associated production cross section σ tW, s-channel single top production cross section σ s , and W-helicity fractions F 0, F L and F R collected at the 8 TeV LHC and Tevatron, we perform a global fit to impose constraints on the top quark effective couplings. Our global fitting results show that the top quark effective couplings are strongly correlated. We show that (i) improving the measurements of σ t and σ tW is important in constraining the correlation of (,) and (,); (ii) and are anti-correlated, and are sensitive to all the four experiments; (iii) and are also anti-correlated, and are sensitive to the F 0 and F L measurements; (iv) the correlation between and is sensitive to the precision of the σ t , σ tW and F 0 measurements. The effective Wtb couplings are studied in three kinds of new physics models: the G(221) = SU(2)1 ⊗ SU(2)2 ⊗ U(1) X models, the vector-like quark models and the Littlest Higgs model with and without T-parity. We show that the Wtb couplings in the left-right model and the un-unified model are sensitive to the ratio of gauge couplings when the new heavy gauge boson’s mass (M W‧) is less than several hundred GeV, but the constraint is loose if M W‧ > 1 TeV. Furthermore, the Wtb couplings in vector-like quark models and the Littlest Higgs models are sensitive to the mixing angles of new heavy particles and SM particles. Supported by National Science Foundation of China (11275009, 11675002, 11635001), National Science Foundation (PHY-1315983, PHY-1316033) and DOE (DE- SC0011095)

Molecular aspect ratio and anchoring strength effects in a confined Gay-Berne liquid crystal

NASA Astrophysics Data System (ADS)

Cañeda-Guzmán, E.; Moreno-Razo, J. A.; Díaz-Herrera, E.; Sambriski, E. J.

2014-04-01

Phase diagrams for Gay-Berne (GB) fluids were obtained from molecular dynamics simulations for GB(2, 5, 1, 2) (i.e. short mesogens) and GB(3, 5, 1, 2) (i.e. long mesogens), which yield isotropic, nematic, and smectic-B phases. The long-mesogen fluid also yields the smectic-A phase. Ordered phases of the long-mesogen fluid form at higher temperatures and lower densities when compared to those of the short-mesogen fluid. The effect of confinement under weak and strong substrate couplings in slab geometry was investigated. Compared to the bulk, the isotropic-nematic transition does not shift in temprature significantly for the weakly coupled substrate in either mesogen fluid. However, the strongly coupled substrate shifts the transition to lower temperature. Confinement induces marked stratification in the short-mesogen fluid. This effect diminishes with distance from the substrate, yielding bulk-like behaviour in the slab central region. Fluid stratification is very weak for the long-mesogen fluid, but the strongly coupled substrate induces 'smectisation', an ordering effect that decays with distance. Orientation of the fluid on the substrate depends on the mesogen. There is no preferred orientation in a plane parallel to the substrate for the weakly coupled case. In the strongly coupled case, the mesogen orientation mimics that of adjacent fluid layers. Planar anchoring is observed with a broad distribution of orientations in the weakly coupled case. In the strongly coupled case, the distribution leans toward planar orientations for the short-mesogen fluid, while a marginal preference for tilting persists in the long-mesogen fluid.

Effects of system-bath coupling on a photosynthetic heat engine: A polaron master-equation approach

NASA Astrophysics Data System (ADS)

Qin, M.; Shen, H. Z.; Zhao, X. L.; Yi, X. X.

2017-07-01

Stimulated by suggestions of quantum effects in energy transport in photosynthesis, the fundamental principles responsible for the near-unit efficiency of the conversion of solar to chemical energy became active again in recent years. Under natural conditions, the formation of stable charge-separation states in bacteria and plant reaction centers is strongly affected by the coupling of electronic degrees of freedom to a wide range of vibrational motions. These inspire and motivate us to explore the effects of the environment on the operation of such complexes. In this paper, we apply the polaron master equation, which offers the possibilities to interpolate between weak and strong system-bath coupling, to study how system-bath couplings affect the exciton-transfer processes in the Photosystem II reaction center described by a quantum heat engine (QHE) model over a wide parameter range. The effects of bath correlation and temperature, together with the combined effects of these factors are also discussed in detail. We interpret these results in terms of noise-assisted transport effect and dynamical localization, which correspond to two mechanisms underpinning the transfer process in photosynthetic complexes: One is resonance energy transfer and the other is the dynamical localization effect captured by the polaron master equation. The effects of system-bath coupling and bath correlation are incorporated in the effective system-bath coupling strength determining whether noise-assisted transport effect or dynamical localization dominates the dynamics and temperature modulates the balance of the two mechanisms. Furthermore, these two mechanisms can be attributed to one physical origin: bath-induced fluctuations. The two mechanisms are manifestations of the dual role played by bath-induced fluctuations depending on the range of parameters. The origin and role of coherence are also discussed. It is the constructive interplay between noise and coherent dynamics, rather than the mere presence or absence of coherence or noise, that is responsible for the optimal heat engine performance. In addition, we find that the effective voltage of QHE exhibits superior robustness against the bath noise as long as the system-bath coupling is not very strong.

Cannabis agonist injection effect on the coupling architecture in cortex of WAG/Rij rats during absence seizures

NASA Astrophysics Data System (ADS)

Sysoeva, Marina V.; Kuznetsova, Galina D.; van Rijn, Clementina M.; Sysoev, Ilya V.

2016-04-01

WAG/Rij rats are well known genetic model of absence epilepsy, which is traditionally considered as a nonconvulsive generalised epilepsy of unknown aetiology. In current study the effect of (R)-(+)-WIN 55,212-2 (cannabis agonist) injection on the coupling between different parts of cortex was studied on 27 male 8 month old rats using local field potentials. Recently developed non-linear adapted Granger causality approach was used as a primary method. It was shown that first 2 hours after the injection the coupling between most channel pairs rises in comparison with the spontaneous activity, whilst long after the injection (2-6 hours) it drops down. The coupling increase corresponds to the mentioned before treatment effect, when the number and the longitude of seizures significantly decreases. However the subsequent decrease of the coupling in the cortex is accompanied by the dramatic increase of the longitude and the number of seizures. This assumes the hypothesis that a relatively higher coupling in the cortical network can prevent the seizure propagation and generalisation.

20 CFR 416.2020 - Federally administered supplementary payments.

Code of Federal Regulations, 2010 CFR

2010-04-01

... for couples) for each title in effect for January 1972: (1) Since a State with a title XVI program had... disabled), the couple (both of whom are aged, blind, or disabled). (2) Other States could supplement up to...) Aged Individual, (ii) Aged Couple, (iii) Blind Individual, (iv) Blind Couple, (v) Disabled Individual...

Modeling of inter-neuronal coupling medium and its impact on neuronal synchronization

PubMed Central

Iqbal, Muhammad; Hong, Keum-Shik

2017-01-01

In this paper, modeling of the coupling medium between two neurons, the effects of the model parameters on the synchronization of those neurons, and compensation of coupling strength deficiency in synchronization are studied. Our study exploits the inter-neuronal coupling medium and investigates its intrinsic properties in order to get insight into neuronal-information transmittance and, there from, brain-information processing. A novel electrical model of the coupling medium that represents a well-known RLC circuit attributable to the coupling medium’s intrinsic resistive, inductive, and capacitive properties is derived. Surprisingly, the integration of such properties reveals the existence of a natural three-term control strategy, referred to in the literature as the proportional integral derivative (PID) controller, which can be responsible for synchronization between two neurons. Consequently, brain-information processing can rely on a large number of PID controllers based on the coupling medium properties responsible for the coherent behavior of neurons in a neural network. Herein, the effects of the coupling model (or natural PID controller) parameters are studied and, further, a supervisory mechanism is proposed that follows a learning and adaptation policy based on the particle swarm optimization algorithm for compensation of the coupling strength deficiency. PMID:28486505

High fidelity CFD-CSD aeroelastic analysis of slender bladed horizontal-axis wind turbine

NASA Astrophysics Data System (ADS)

Sayed, M.; Lutz, Th.; Krämer, E.; Shayegan, Sh.; Ghantasala, A.; Wüchner, R.; Bletzinger, K.-U.

2016-09-01

The aeroelastic response of large multi-megawatt slender horizontal-axis wind turbine blades is investigated by means of a time-accurate CFD-CSD coupling approach. A loose coupling approach is implemented and used to perform the simulations. The block- structured CFD solver FLOWer is utilized to obtain the aerodynamic blade loads based on the time-accurate solution of the unsteady Reynolds-averaged Navier-Stokes equations. The CSD solver Carat++ is applied to acquire the blade elastic deformations based on non-linear beam elements. In this contribution, the presented coupling approach is utilized to study the aeroelastic response of the generic DTU 10MW wind turbine. Moreover, the effect of the coupled results on the wind turbine performance is discussed. The results are compared to the aeroelastic response predicted by FLOWer coupled to the MBS tool SIMPACK as well as the response predicted by SIMPACK coupled to a Blade Element Momentum code for aerodynamic predictions. A comparative study among the different modelling approaches for this coupled problem is discussed to quantify the coupling effects of the structural models on the aeroelastic response.

Artificial dispersion via high-order homogenization: magnetoelectric coupling and magnetism from dielectric layers

PubMed Central

Liu, Yan; Guenneau, Sébastien; Gralak, Boris

2013-01-01

We investigate a high-order homogenization (HOH) algorithm for periodic multi-layered stacks. The mathematical tool of choice is a transfer matrix method. Expressions for effective permeability, permittivity and magnetoelectric coupling are explored by frequency power expansions. On the physical side, this HOH uncovers a magnetoelectric coupling effect (odd-order approximation) and artificial magnetism (even-order approximation) in moderate contrast photonic crystals. Comparing the effective parameters' expressions of a stack with three layers against that of a stack with two layers, we note that the magnetoelectric coupling effect vanishes while the artificial magnetism can still be achieved in a centre-symmetric periodic structure. Furthermore, we numerically check the effective parameters through the dispersion law and transmission property of a stack with two dielectric layers against that of an effective bianisotropic medium: they are in good agreement throughout the low-frequency (acoustic) band until the first stop band, where the analyticity of the logarithm function of the transfer matrix () breaks down. PMID:24101891

A Tightly Coupled Non-Equilibrium Magneto-Hydrodynamic Model for Inductively Coupled RF Plasmas

DTIC Science & Technology

2016-02-29

development a tightly coupled magneto-hydrodynamic model for Inductively Coupled Radio- Frequency (RF) Plasmas. Non Local Thermodynamic Equilibrium (NLTE...for Inductively Coupled Radio-Frequency (RF) Plasmas. Non Local Thermodynamic Equilibrium (NLTE) effects are described based on a hybrid State-to-State... thermodynamic variable. This choice allows one to hide the non-linearity of the gas (total) thermal conductivity κ and can partially alle- 2 viate numerical

Copper-catalyzed oxidative homo- and cross-coupling of Grignard reagents using diaziridinone.

PubMed

Zhu, Yingguang; Xiong, Tao; Han, Wenyong; Shi, Yian

2014-12-05

Transition-metal-catalyzed cross-coupling reactions are among the most powerful synthetic transformations. This paper describes an efficient copper-catalyzed homo- and cross-coupling of Grignard reagents with di-tert-butyldiaziridinone as oxidant under mild conditions, giving the coupling products in good to excellent yields. The reaction process has a broad substrate scope and is also effective for the C(sp)-C(sp(3)) coupling.

AUV Positioning Method Based on Tightly Coupled SINS/LBL for Underwater Acoustic Multipath Propagation.

PubMed

Zhang, Tao; Shi, Hongfei; Chen, Liping; Li, Yao; Tong, Jinwu

2016-03-11

This paper researches an AUV (Autonomous Underwater Vehicle) positioning method based on SINS (Strapdown Inertial Navigation System)/LBL (Long Base Line) tightly coupled algorithm. This algorithm mainly includes SINS-assisted searching method of optimum slant-range of underwater acoustic propagation multipath, SINS/LBL tightly coupled model and multi-sensor information fusion algorithm. Fuzzy correlation peak problem of underwater LBL acoustic propagation multipath could be solved based on SINS positional information, thus improving LBL positional accuracy. Moreover, introduction of SINS-centered LBL locating information could compensate accumulative AUV position error effectively and regularly. Compared to loosely coupled algorithm, this tightly coupled algorithm can still provide accurate location information when there are fewer than four available hydrophones (or within the signal receiving range). Therefore, effective positional calibration area of tightly coupled system based on LBL array is wider and has higher reliability and fault tolerance than loosely coupled. It is more applicable to AUV positioning based on SINS/LBL.

AUV Positioning Method Based on Tightly Coupled SINS/LBL for Underwater Acoustic Multipath Propagation

PubMed Central

Zhang, Tao; Shi, Hongfei; Chen, Liping; Li, Yao; Tong, Jinwu

2016-01-01

This paper researches an AUV (Autonomous Underwater Vehicle) positioning method based on SINS (Strapdown Inertial Navigation System)/LBL (Long Base Line) tightly coupled algorithm. This algorithm mainly includes SINS-assisted searching method of optimum slant-range of underwater acoustic propagation multipath, SINS/LBL tightly coupled model and multi-sensor information fusion algorithm. Fuzzy correlation peak problem of underwater LBL acoustic propagation multipath could be solved based on SINS positional information, thus improving LBL positional accuracy. Moreover, introduction of SINS-centered LBL locating information could compensate accumulative AUV position error effectively and regularly. Compared to loosely coupled algorithm, this tightly coupled algorithm can still provide accurate location information when there are fewer than four available hydrophones (or within the signal receiving range). Therefore, effective positional calibration area of tightly coupled system based on LBL array is wider and has higher reliability and fault tolerance than loosely coupled. It is more applicable to AUV positioning based on SINS/LBL. PMID:26978361

The Multi-Domain Fibroblast/Myocyte Coupling in the Cardiac Tissue: A Theoretical Study.

PubMed

Greisas, Ariel; Zlochiver, Sharon

2016-09-01

Cardiac fibroblast proliferation and concomitant collagenous matrix accumulation (fibrosis) develop during multiple cardiac pathologies. Recent studies have demonstrated direct electrical coupling between myocytes and fibroblasts in vitro, and assessed the electrophysiological implications of such coupling. However, in the living tissues, such coupling has not been demonstrated, and only indirect coupling via the extracellular space is likely to exist. In this study we employed a multi-domain model to assess the modulation of the cardiac electrophysiological properties by neighboring fibroblasts assuming only indirect coupling. Numerical simulations in 1D and 2D human atrial models showed that extracellular coupling sustains a significant impact on conduction velocity (CV) and a less significant effect on the action potential duration. Both CV and the slope of the CV restitution increased with increasing fibroblast density. This effect was more substantial for lower extracellular conductance. In 2D, spiral waves exhibited reduced frequency with increasing fibroblast density, and the propensity of wavebreaks and complex dynamics at high pacing rates significantly increased.

Visual information underpinning skilled anticipation: The effect of blur on a coupled and uncoupled in situ anticipatory response.

PubMed

Mann, David L; Abernethy, Bruce; Farrow, Damian

2010-07-01

Coupled interceptive actions are understood to be the result of neural processing-and visual information-which is distinct from that used for uncoupled perceptual responses. To examine the visual information used for action and perception, skilled cricket batters anticipated the direction of balls bowled toward them using a coupled movement (an interceptive action that preserved the natural coupling between perception and action) or an uncoupled (verbal) response, in each of four different visual blur conditions (plano, +1.00, +2.00, +3.00). Coupled responses were found to be better than uncoupled ones, with the blurring of vision found to result in different effects for the coupled and uncoupled response conditions. Low levels of visual blur did not affect coupled anticipation, a finding consistent with the comparatively poorer visual information on which online interceptive actions are proposed to rely. In contrast, some evidence was found to suggest that low levels of blur may enhance the uncoupled verbal perception of movement.

Computations of the chirality-sensitive effect induced by an antisymmetric indirect spin–spin coupling

NASA Astrophysics Data System (ADS)

Garbacz, Piotr

2018-05-01

Results of quantum mechanical computations of the antisymmetric part of the indirect spin-spin coupling tensor, ?, performed using the coupled-cluster method, the second-order polarisation propagator approximation, and the density functional theory for 25 molecules and nearly 100 spin-spin couplings are reported. These results are used for an estimation of the magnitude of the recently proposed liquid-state nuclear magnetic resonance chirality-sensitive effect, which allows to determine the molecular chirality directly, i.e. without the need for the application of any chiral agent. The following were found: (i) the antisymmetry J⋆ is usually larger for the coupling between spins separated by two chemical bonds in comparison with the coupling through one bond, (ii) promising samples are those which contain fluorine, and (iii) the antisymmetry of the spin-spin coupling tensor is of the order of a few hertz for commercially available chemical compounds. Therefore, the relevant property of the experiment, the pseudoscalar Jc, for them is of the order of 1 nHz m/V.

A Dyadic Analysis of Relationships and Health: Does Couple-Level Context Condition Partner Effects?

PubMed Central

Barr, Ashley B.; Simons, Ronald L.

2014-01-01

Adding to the growing literature explicating the links between romantic relationships and health, this study examined how both couple-level characteristics, particularly union type (e.g. dating, cohabiting, or marriage) and interracial pairing, and interpersonal characteristics (e.g. partner strain and support) predicted young adults’ physical and mental health. Using dyadic data from a sample of 249 young, primarily African American couples, we hypothesized and found support for the importance of couple-level context, partner behavior, and their interaction in predicting health. Interracial couples (all Black/non-Black pairings) reported worse health than monoracial Black couples. Union type, however, did not directly predict health but was a significant moderator of partner strain. That is, the negative association between partner strain and self-reported health was stronger for cohabiting and married couples versus their dating counterparts, suggesting that coresidence more so than marital status may be important for understanding partner effects on physical health. For psychological distress, however, partner support proved equally beneficial across union types. PMID:25090254

A dyadic analysis of relationships and health: does couple-level context condition partner effects?

PubMed

Barr, Ashley B; Simons, Ronald L

2014-08-01

Adding to the growing literature explicating the links between romantic relationships and health, this study examined how both couple-level characteristics, particularly union type (e.g., dating, cohabiting, or marriage) and interracial pairing, and interpersonal characteristics (e.g., partner strain and support), predicted young adults' physical and mental health. Using dyadic data from a sample of 249 young, primarily Black couples, we hypothesized and found support for the importance of couple-level context, partner behavior, and their interaction in predicting health. Interracial couples (all Black/non-Black pairings) reported worse health than monoracial Black couples. Union type, however, did not directly predict health but was a significant moderator of partner strain. That is, the negative association between partner strain and self-reported health was stronger for cohabiting and married couples versus their dating counterparts, suggesting that coresidence, more so than marital status, may be important for understanding partner effects on physical health. For psychological distress, however, partner support proved equally beneficial across union types.

Effect of inter-tissue inductive coupling on multi-frequency imaging of intracranial hemorrhage by magnetic induction tomography

NASA Astrophysics Data System (ADS)

Xiao, Zhili; Tan, Chao; Dong, Feng

2017-08-01

Magnetic induction tomography (MIT) is a promising technique for continuous monitoring of intracranial hemorrhage due to its contactless nature, low cost and capacity to penetrate the high-resistivity skull. The inter-tissue inductive coupling increases with frequency, which may lead to errors in multi-frequency imaging at high frequency. The effect of inter-tissue inductive coupling was investigated to improve the multi-frequency imaging of hemorrhage. An analytical model of inter-tissue inductive coupling based on the equivalent circuit was established. A set of new multi-frequency decomposition equations separating the phase shift of hemorrhage from other brain tissues was derived by employing the coupling information to improve the multi-frequency imaging of intracranial hemorrhage. The decomposition error and imaging error are both decreased after considering the inter-tissue inductive coupling information. The study reveals that the introduction of inter-tissue inductive coupling can reduce the errors of multi-frequency imaging, promoting the development of intracranial hemorrhage monitoring by multi-frequency MIT.

Effects of dyes, gold nanocrystals, pH, and metal ions on plasmonic and molecular resonance coupling.

PubMed

Ni, Weihai; Chen, Huanjun; Su, Jing; Sun, Zhenhua; Wang, Jianfang; Wu, Hongkai

2010-04-07

The effects of various factors on the resonance coupling between elongated Au nanocrystals and organic dyes have been systematically investigated through the preparation of hybrid nanostructures between Au nanocrystals and the electrostatically adsorbed dye molecules. A nanocrystal sample is chosen for each dye to match the longitudinal plasmon resonance wavelength with the absorption peak wavelength of the dye as close as possible so that the resonance coupling strength can be maximized. The resonance coupling strength is found to approximately increase as the molecular volume-normalized absorptivity is increased. It is mainly determined by the plasmon resonance energy of the Au nanocrystals instead of their shapes and sizes. Moreover, the resonance coupling can be reversibly controlled if the dye in the hybrid nanostructures is pH-sensitive. The coupling can also be weakened in the presence of metal ions. These results will be highly useful for designing resonance coupling-based sensing devices and for plasmon-enhanced spectroscopy.

Magnetization switching behavior with competing anisotropies in epitaxial Co3FeN /MnN exchange-coupled bilayers

NASA Astrophysics Data System (ADS)

Hajiri, T.; Yoshida, T.; Jaiswal, S.; Filianina, M.; Borie, B.; Ando, H.; Asano, H.; Zabel, H.; Kläui, M.

2016-11-01

We report unusual magnetization switching processes and angular-dependent exchange bias effects in fully epitaxial Co3FeN /MnN bilayers, where magnetocrystalline anisotropy and exchange coupling compete, probed by longitudinal and transverse magneto-optic Kerr effect (MOKE) magnetometry. The MOKE loops show multistep jumps corresponding to the nucleation and propagation of 90∘ domain walls in as-grown bilayers. By inducing exchange coupling, we confirm changes of the magnetization switching process due to the unidirectional anisotropy field of the exchange coupling. Taking into account the experimentally obtained values of the fourfold magnetocrystalline anisotropy, the unidirectional anisotropy field, the exchange-coupling constant, and the uniaxial anisotropy including its direction, the calculated angular-dependent exchange bias reproduces the experimental results. These results demonstrate the essential role of the competition between magnetocrystalline anisotropy and exchange coupling for understanding and tailoring exchange-coupling phenomena usable for engineering switching in fully epitaxial bilayers made of tailored materials.

One-electron versus electron-electron interaction contributions to the spin-spin coupling mechanism in nuclear magnetic resonance spectroscopy: Analysis of basic electronic effects

NASA Astrophysics Data System (ADS)

Gräfenstein, Jürgen; Cremer, Dieter

2004-12-01

For the first time, the nuclear magnetic resonance (NMR) spin-spin coupling mechanism is decomposed into one-electron and electron-electron interaction contributions to demonstrate that spin-information transport between different orbitals is not exclusively an electron-exchange phenomenon. This is done using coupled perturbed density-functional theory in conjunction with the recently developed J-OC-PSP [=J-OC-OC-PSP: Decomposition of J into orbital contributions using orbital currents and partial spin polarization)] method. One-orbital contributions comprise Ramsey response and self-exchange effects and the two-orbital contributions describe first-order delocalization and steric exchange. The two-orbital effects can be characterized as external orbital, echo, and spin transport contributions. A relationship of these electronic effects to zeroth-order orbital theory is demonstrated and their sign and magnitude predicted using simple models and graphical representations of first order orbitals. In the case of methane the two NMR spin-spin coupling constants result from totally different Fermi contact coupling mechanisms. 1J(C,H) is the result of the Ramsey response and the self-exchange of the bond orbital diminished by external first-order delocalization external one-orbital effects whereas 2J(H,H) spin-spin coupling is almost exclusively mitigated by a two-orbital steric exchange effect. From this analysis, a series of prediction can be made how geometrical deformations, electron lone pairs, and substituent effects lead to a change in the values of 1J(C,H) and 2J(H,H), respectively, for hydrocarbons.

Soft thermal contributions to 3-loop gauge coupling

NASA Astrophysics Data System (ADS)

Laine, M.; Schicho, P.; Schröder, Y.

2018-05-01

We analyze 3-loop contributions to the gauge coupling felt by ultrasoft ("magnetostatic") modes in hot Yang-Mills theory. So-called soft/hard terms, originating from dimension-six operators within the soft effective theory, are shown to cancel 1097/1098 of the IR divergence found in a recent determination of the hard 3-loop contribution to the soft gauge coupling. The remaining 1/1098 originates from ultrasoft/hard contributions, induced by dimension-six operators in the ultrasoft effective theory. Soft 3-loop contributions are likewise computed, and are found to be IR divergent, rendering the ultrasoft gauge coupling non-perturbative at relative order O({α}s^{3/2}) . We elaborate on the implications of these findings for effective theory studies of physical observables in thermal QCD.

Global constraints on vector-like WIMP effective interactions

DOE PAGES

Blennow, Mattias; Coloma, Pilar; Fernandez-Martinez, Enrique; ...

2016-04-07

In this work we combine information from relic abundance, direct detection, cosmic microwave background, positron fraction, gamma rays, and colliders to explore the existing constraints on couplings between Dark Matter and Standard Model constituents when no underlying model or correlation is assumed. For definiteness, we include independent vector-like effective interactions for each Standard Model fermion. Our results show that low Dark Matter masses below 20 GeV are disfavoured at the 3 σ  level with respect to higher masses, due to the tension between the relic abundance requirement and upper constraints on the Dark Matter couplings. Lastly, large couplings are typically onlymore » allowed in combinations which avoid effective couplings to the nuclei used in direct detection experiments.« less

Localization and delocalization of a one-dimensional system coupled with the environment

NASA Astrophysics Data System (ADS)

Zhu, Hong-Jun; Xiong, Shi-Jie

2010-03-01

We investigate several models of a one-dimensional chain coupling with surrounding atoms to elucidate disorder-induced delocalization in quantum wires, a peculiar behaviour against common wisdom. We show that the localization length is enhanced by disorder of side sites in the case of strong disorder, but in the case of weak disorder there is a plateau in this dependence. The above behaviour is the conjunct influence of the coupling to the surrounding atoms and the antiresonant effect. We also discuss different effects and their physical origin of different types of disorder in such systems. The numerical results show that coupling with the surrounding atoms can induce either the localization or delocalization effect depending on the values of parameters.

Cluster synchronization induced by one-node clusters in networks with asymmetric negative couplings

NASA Astrophysics Data System (ADS)

Zhang, Jianbao; Ma, Zhongjun; Zhang, Gang

2013-12-01

This paper deals with the problem of cluster synchronization in networks with asymmetric negative couplings. By decomposing the coupling matrix into three matrices, and employing Lyapunov function method, sufficient conditions are derived for cluster synchronization. The conditions show that the couplings of multi-node clusters from one-node clusters have beneficial effects on cluster synchronization. Based on the effects of the one-node clusters, an effective and universal control scheme is put forward for the first time. The obtained results may help us better understand the relation between cluster synchronization and cluster structures of the networks. The validity of the control scheme is confirmed through two numerical simulations, in a network with no cluster structure and in a scale-free network.

The interplay between interpersonal stress and psychological intimate partner violence over time for young at-risk couples.

PubMed

Shortt, Joann Wu; Capaldi, Deborah M; Kim, Hyoun K; Tiberio, Stacey S

2013-04-01

The substantial number of young people in romantic relationships that involve intimate partner violence, a situation deleterious to physical and mental health, has resulted in increased attention to understanding the links between risk factors and course of violence. The current study examined couples' interpersonal stress related to not liking partners' friends and not getting along with parents as contextual factors associated with couples' psychological partner violence and determined whether and when couples' friend and parent stress increased the likelihood of couples' psychological partner violence. A linear latent growth curve modeling approach was used with multiwave measures of psychological partner violence, friend stress, parent stress, and relationship satisfaction obtained from 196 men at risk for delinquency and their women partners over a 12-year period. At the initial assessment, on average, the men were age 21.5 years and the women were age 21 years. Findings indicated that couples experiencing high levels of friend and parent stress were more likely to engage in high levels of psychological partner violence and that increases in couples' friend stress predicted increases in couples' partner violence over time, even when accounting for the couples' relationship satisfaction, marital status, children in the home, and financial strain. Interactive effects were at play when the couples were in their early 20s, with couples being most at risk for increases in psychological partner violence if they experienced both high friend stress and low relationship satisfaction. Couples' friend stress had the greatest effect on psychological partner violence when the couples were in their early to mid 20s when levels of friend stress were high. As the couples reached their 30s, low relationship satisfaction became the leading predictor of couples' psychological partner violence.

Dynamic analysis of pretwisted elastically-coupled rotor blades

NASA Technical Reports Server (NTRS)

Nixon, Mark W.; Hinnant, Howard E.

1994-01-01

The accuracy of using a one-dimensional analysis to predict frequencies of elastically-coupled highly-twisted rotor blades is addressed. Degrees of freedom associated with shear deformation are statically condensed from the formulation, so the analysis uses only those degrees of freedom associated with classical beam theory. The effects of cross section deformation (warping) are considered, and are shown to become significant for some types of elastic coupling. Improved results are demonstrated for highly-coupled blade structures through account of warping in a local cross section analysis, without explicit inclusion of these effects in the beam analysis. A convergence study is also provided which investigates the potential for improving efficiency of elastically-coupled beam analysis through implementation of a p-version beam finite element.

Wheat glutenin: the "tail" of the 1By protein subunits.

PubMed

Nunes-Miranda, Júlio D; Bancel, Emmanuelle; Viala, Didier; Chambon, Christophe; Capelo, José L; Branlard, Gérard; Ravel, Catherine; Igrejas, Gilberto

2017-10-03

Gluten-forming storage proteins play a major role in the viscoelastic properties of wheat dough through the formation of a continuous proteinaceous network. The high-molecular-weight glutenin subunits represent a functionally important subgroup of gluten proteins by promoting the formation of large glutenin polymers through interchain disulphide bonds between glutenin subunits. Here, we present evidences that y-type glutenin subunits encoded at the Glu-B1 locus are prone to proteolytic processing at the C-terminus tail, leading to the loss of the unique cysteine residue present at the C-terminal domain. Results obtained by intact mass measurement and immunochemistry for each proteoform indicate that the proteolytic cleavage appears to occur at the carboxyl-side of two conserved asparagine residues at the C-terminal domain start. Hence, we hypothesize that the responsible enzymes are a class of cysteine endopeptidases - asparaginyl endopeptidases - described in post-translational processing of other storage proteins in wheat. Biological significance The reported study provides new insights into wheat storage protein maturation. In view of the importance of gluten proteins on dough viscoelastic properties and end-product quality, the reported C-terminal domain cleavage of high-molecular-weight glutenin subunits is of particular interest, since this domain possesses a unique conserved cysteine residue which is assumed to participate in gluten polymerization. Copyright © 2017 Elsevier B.V. All rights reserved.

Sequence Directionality Dramatically Affects LCST Behavior of Elastin-Like Polypeptides.

PubMed

Li, Nan K; Roberts, Stefan; Quiroz, Felipe Garcia; Chilkoti, Ashutosh; Yingling, Yaroslava G

2018-04-30

Elastin-like polypeptides (ELP) exhibit an inverse temperature transition or lower critical solution temperature (LCST) transition phase behavior in aqueous solutions. In this paper, the thermal responsive properties of the canonical ELP, poly(VPGVG), and its reverse sequence poly(VGPVG) were investigated by turbidity measurements of the cloud point behavior, circular dichroism (CD) measurements, and all-atom molecular dynamics (MD) simulations to gain a molecular understanding of mechanism that controls hysteretic phase behavior. It was shown experimentally that both poly(VPGVG) and poly(VGPVG) undergo a transition from soluble to insoluble in aqueous solution upon heating above the transition temperature ( T t ). However, poly(VPGVG) resolubilizes upon cooling below its T t , whereas the reverse sequence, poly(VGPVG), remains aggregated despite significant undercooling below the T t . The results from MD simulations indicated that a change in sequence order results in significant differences in the dynamics of the specific residues, especially valines, which lead to extensive changes in the conformations of VPGVG and VGPVG pentamers and, consequently, dissimilar propensities for secondary structure formation and overall structure of polypeptides. These changes affected the relative hydrophilicities of polypeptides above T t , where poly(VGPVG) is more hydrophilic than poly(VPGVG) with more extended conformation and larger surface area, which led to formation of strong interchain hydrogen bonds responsible for stabilization of the aggregated phase and the observed thermal hysteresis for poly(VGPVG).

Photophysical and morphological implications of single-strand conjugated polymer folding in solution

DOE PAGES

Fauvell, Thomas J.; Zheng, Tianyue; Jackson, Nicholas E.; ...

2016-04-08

Organic semiconductors have garnered substantial interest in optoelectronics, but their device performances exhibit strong dependencies on material crystallinity and packing. In an effort to understand the interactions dictating the morphological and photophysical properties of a high-performing photovoltaic polymer, PTB7, a series of short oligomers and low molecular weight polymers of PTB7 were synthesized. Chain-length dependent optical studies of these oligomers demonstrate that PTB7’s low-energy visible absorption is largely due to self-aggregation-induced ordering, rather than in-chain charge transfer, as previously thought. By examining molecular weight and concentration dependent optical properties, supplemented by molecular dynamics simulations, we attribute polymeric PTB7’s unique midgapmore » fluorescence and concentration independent absorption spectrum to an interplay between low molecular weight unaggregated strands and high-molecular weight self-aggregated (folded) strands. Specifically, we propose that the onset of PTB7 self-folding occurs between 7 and 13 repeat units, but the aggregates characteristic of polymeric PTB7 only develop at lengths of ~30 repeat units. Atomistic molecular dynamics simulations of PTB7 corroborate these conclusions, and a simple relation is proposed which quantifies the free-energy of conjugated polymer folding. Lastly, this study provides detailed guidance in the design of intra- and interchain contributions to the photophysical and morphological properties of polymeric semiconductors.« less

NIR-laser tissue welding in an in vivo guinea pig animal model

NASA Astrophysics Data System (ADS)

Sriramoju, Vidyasagar; Savage, Howard E.; Katz, A.; Chakraverty, Rahul; Budansky, Yuri; Podder, Rakhi; Davatgarzadeh, Naghmeh; Kartazayev, Uladzimir; Rosen, Richard B.; Alfano, R. R.

2008-02-01

Near infrared laser tissue welding (LTW) is achieved by subjecting the closely approximated surgically incised tissues to a laser beam at a wavelength that is absorbed by water in the tissue. Full thickness welds are accomplished with optimum laser power and penetration depths appropriate for the thickness of welded tissues. No extrinsic cross-linking or bonding materials are used. The absorbed laser energy increases the entropy of collagen in the tissue. In LTW, tissue water temperatures transiently rises to approximately 60° C, causing partial denaturing of collagen and other structural proteins due to breaking of hydrogen bonds, electrostatic interactions and some interchain covalent bonds for a short duration of time. This is followed by cross linking of proteins on either side of weld line, with reformation of the above mentioned bonds as the tissue cools, resulting in the formation of water tight full thickness welds. In this study, a cw fiber laser emitting at 1455 nm, corresponding to absorption by a water vibrational overtone, is used for in vivo LTW of surgical incisions made in the skin of guinea pigs under general anesthesia. The tensile strength and healing rates of the welded incisions are compared to suturing of similar incisions. Laser parameters, including power, scanning rates, exposure area, and exposure duration, are optimized to reduce thermal damage while maintaining tensile strength.

Molecular dynamics characterization of the SAMHD1 Aicardi-Goutières Arg145Gln mutant: structural determinants for the impaired tetramerization.

PubMed

Cardamone, Francesca; Falconi, Mattia; Desideri, Alessandro

2018-05-01

Aicardi-Goutières syndrome, a rare genetic disorder characterized by calcification of basal ganglia, results in psychomotor delays and epilepsy states from the early months of children life. This disease is caused by mutations in seven different genes encoding proteins implicated in the metabolism of nucleic acids, including SAMHD1. Twenty SAMHD1 gene variants have been discovered and in this work, a structural characterization of the SAMHD1 Aicardi-Goutières Arg145Gln mutant is reported by classical molecular dynamics simulation. Four simulations have been carried out and compared. Two concerning the wild-type SAMHD1 form in presence and absence of cofactors, in order to explain the role of cofactors in the SAMHD1 assembly/disassembly process and, two concerning the Arg145Gln mutant, also in presence and absence of cofactors, in order to have an accurate comparison with the corresponding native forms. Results show the importance of native residue Arg145 in maintaining the tetramer, interacting with GTP cofactor inside allosteric sites. Replacement of arginine in glutamine gives rise to a loosening of GTP-protein interactions, when cofactors are present in allosteric sites, whilst in absence of cofactors, the occurrence of intra and inter-chain interactions is observed in the mutant, not seen in the native enzyme, making energetically unfavourable the tetramerization process.

Molecular dynamics characterization of the SAMHD1 Aicardi-Goutières Arg145Gln mutant: structural determinants for the impaired tetramerization

NASA Astrophysics Data System (ADS)

Cardamone, Francesca; Falconi, Mattia; Desideri, Alessandro

2018-05-01

Aicardi-Goutières syndrome, a rare genetic disorder characterized by calcification of basal ganglia, results in psychomotor delays and epilepsy states from the early months of children life. This disease is caused by mutations in seven different genes encoding proteins implicated in the metabolism of nucleic acids, including SAMHD1. Twenty SAMHD1 gene variants have been discovered and in this work, a structural characterization of the SAMHD1 Aicardi-Goutières Arg145Gln mutant is reported by classical molecular dynamics simulation. Four simulations have been carried out and compared. Two concerning the wild-type SAMHD1 form in presence and absence of cofactors, in order to explain the role of cofactors in the SAMHD1 assembly/disassembly process and, two concerning the Arg145Gln mutant, also in presence and absence of cofactors, in order to have an accurate comparison with the corresponding native forms. Results show the importance of native residue Arg145 in maintaining the tetramer, interacting with GTP cofactor inside allosteric sites. Replacement of arginine in glutamine gives rise to a loosening of GTP-protein interactions, when cofactors are present in allosteric sites, whilst in absence of cofactors, the occurrence of intra and inter-chain interactions is observed in the mutant, not seen in the native enzyme, making energetically unfavourable the tetramerization process.

Molecular dynamics characterization of the SAMHD1 Aicardi-Goutières Arg145Gln mutant: structural determinants for the impaired tetramerization

NASA Astrophysics Data System (ADS)

Cardamone, Francesca; Falconi, Mattia; Desideri, Alessandro

2018-03-01

Aicardi-Goutières syndrome, a rare genetic disorder characterized by calcification of basal ganglia, results in psychomotor delays and epilepsy states from the early months of children life. This disease is caused by mutations in seven different genes encoding proteins implicated in the metabolism of nucleic acids, including SAMHD1. Twenty SAMHD1 gene variants have been discovered and in this work, a structural characterization of the SAMHD1 Aicardi-Goutières Arg145Gln mutant is reported by classical molecular dynamics simulation. Four simulations have been carried out and compared. Two concerning the wild-type SAMHD1 form in presence and absence of cofactors, in order to explain the role of cofactors in the SAMHD1 assembly/disassembly process and, two concerning the Arg145Gln mutant, also in presence and absence of cofactors, in order to have an accurate comparison with the corresponding native forms. Results show the importance of native residue Arg145 in maintaining the tetramer, interacting with GTP cofactor inside allosteric sites. Replacement of arginine in glutamine gives rise to a loosening of GTP-protein interactions, when cofactors are present in allosteric sites, whilst in absence of cofactors, the occurrence of intra and inter-chain interactions is observed in the mutant, not seen in the native enzyme, making energetically unfavourable the tetramerization process.

The thioredoxin reductase--Thioredoxin redox system cleaves the interchain disulphide bond of botulinum neurotoxins on the cytosolic surface of synaptic vesicles.

PubMed

Pirazzini, Marco; Azarnia Tehran, Domenico; Zanetti, Giulia; Lista, Florigio; Binz, Thomas; Shone, Clifford C; Rossetto, Ornella; Montecucco, Cesare

2015-12-01

Botulinum neurotoxins (BoNTs) are Janus toxins, as they are at the same time the most deadly substances known and one of the safest drugs used in human therapy. They specifically block neurotransmission at peripheral nerves through the proteolysis of SNARE proteins, i.e. the essential proteins which are the core of the neuroexocytosis machinery. Even if BoNTs are traditionally known as seven main serotypes, their actual number is much higher as each serotype exists in many different subtypes, with individual biological properties and little antigenic relations. Since BoNTs can be used as biological weapons, and the only currently available therapy is based on immunological approaches, the existence of so many different subtypes is a major safety problem. Nevertheless, all BoNT isoforms are structurally similar and intoxicate peripheral nerve endings via a conserved mechanism. They consist of two chains linked by a unique disulphide bond which must be reduced to enable their toxicity. We found that thioredoxin 1 and its reductase compose the cell redox system responsible for this reduction, and its inhibition via specific chemicals significantly reduces BoNTs activity, in vitro as well as in vivo. Such molecules can be considered as lead compounds for the development of pan-inhibitors. Copyright © 2015 Elsevier Ltd. All rights reserved.

A functional dual-coated (FDC) microtiter plate method to replace the botulinum toxin LD50 test.

PubMed

Liu, Yvonne Y B; Rigsby, Peter; Sesardic, Dorothea; Marks, James D; Jones, Russell G A

2012-06-01

Conventional capture ("Sandwich") ELISAs equally detect denatured inactive and native active botulinum type A toxin. Light chain endoprotease activity assays also fail to distinguish between various inactive molecules including partially denatured and fragmented material still retaining this protease activity. By co-coating microtiter plates with SNAP25 substrate and a monoclonal antibody specific for a conformational epitope of the toxin's Hc domain, it was possible to develop a highly sensitive (130 aM LoD), precise (1.4% GCV) new assay specific for the biologically active toxin molecule. Capture was performed in phosphate buffer with a fixed optimal concentration of chaotropic agent (e.g., 1.2 M urea) to differentially isolate functional toxin molecules. Addition of enzymatically favorable buffer containing zinc and DTT reduced the interchain disulfide bond releasing and activating the captured L-chain with subsequent specific cleavage of the SNAP25(1-206) substrate. A neoepitope antibody specific for the newly exposed Q(197) epitope was used to quantify the cleaved SNAP25(1-197). The assay's requirement for the intact toxin molecule was demonstrated with pre-reduced toxin (heavy and light chains), recombinant LHn fragments, and stressed samples containing partially or fully denatured material. This is the first known immunobiochemical assay that correlates with in vivo potency and provides a realistic alternative. Copyright © 2012 Elsevier Inc. All rights reserved.

CFD-CAA Coupled Calculations of a Tandem Cylinder Configuration to Assess Facility Installation Effects

NASA Technical Reports Server (NTRS)

Redonnet, Stephane; Lockard, David P.; Khorrami, Mehdi R.; Choudhari, Meelan M.

2011-01-01

This paper presents a numerical assessment of acoustic installation effects in the tandem cylinder (TC) experiments conducted in the NASA Langley Quiet Flow Facility (QFF), an open-jet, anechoic wind tunnel. Calculations that couple the Computational Fluid Dynamics (CFD) and Computational Aeroacoustics (CAA) of the TC configuration within the QFF are conducted using the CFD simulation results previously obtained at NASA LaRC. The coupled simulations enable the assessment of installation effects associated with several specific features in the QFF facility that may have impacted the measured acoustic signature during the experiment. The CFD-CAA coupling is based on CFD data along a suitably chosen surface, and employs a technique that was recently improved to account for installed configurations involving acoustic backscatter into the CFD domain. First, a CFD-CAA calculation is conducted for an isolated TC configuration to assess the coupling approach, as well as to generate a reference solution for subsequent assessments of QFF installation effects. Direct comparisons between the CFD-CAA calculations associated with the various installed configurations allow the assessment of the effects of each component (nozzle, collector, etc.) or feature (confined vs. free jet flow, etc.) characterizing the NASA LaRC QFF facility.

Quantum stream instability in coupled two-dimensional plasmas

NASA Astrophysics Data System (ADS)

Akbari-Moghanjoughi, M.

2014-08-01

In this paper the quantum counter-streaming instability problem is studied in planar two-dimensional (2D) quantum plasmas using the coupled quantum hydrodynamic (CQHD) model which incorporates the most important quantum features such as the statistical Fermi-Dirac electron pressure, the electron-exchange potential and the quantum diffraction effect. The instability is investigated for different 2D quantum electron systems using the dynamics of Coulomb-coupled carriers on each plasma sheet when these plasmas are both monolayer doped graphene or metalfilm (corresponding to 2D Dirac or Fermi electron fluids). It is revealed that there are fundamental differences between these two cases regarding the effects of Bohm's quantum potential and the electron-exchange on the instability criteria. These differences mark yet another interesting feature of the effect of the energy band dispersion of Dirac electrons in graphene. Moreover, the effects of plasma number-density and coupling parameter on the instability criteria are shown to be significant. This study is most relevant to low dimensional graphene-based field-effect-transistor (FET) devices. The current study helps in understanding the collective interactions of the low-dimensional coupled ballistic conductors and the nanofabrication of future graphene-based integrated circuits.

First example of a high-level correlated calculation of the indirect spin-spin coupling constants involving tellurium: tellurophene and divinyl telluride.

PubMed

Rusakov, Yury Yu; Krivdin, Leonid B; Østerstrøm, Freja F; Sauer, Stephan P A; Potapov, Vladimir A; Amosova, Svetlana V

2013-08-21

This paper documents the very first example of a high-level correlated calculation of spin-spin coupling constants involving tellurium taking into account relativistic effects, vibrational corrections and solvent effects for medium sized organotellurium molecules. The (125)Te-(1)H spin-spin coupling constants of tellurophene and divinyl telluride were calculated at the SOPPA and DFT levels, in good agreement with experimental data. A new full-electron basis set, av3z-J, for tellurium derived from the "relativistic" Dyall's basis set, dyall.av3z, and specifically optimized for the correlated calculations of spin-spin coupling constants involving tellurium was developed. The SOPPA method shows a much better performance compared to DFT, if relativistic effects calculated within the ZORA scheme are taken into account. Vibrational and solvent corrections are next to negligible, while conformational averaging is of prime importance in the calculation of (125)Te-(1)H spin-spin couplings. Based on the performed calculations at the SOPPA(CCSD) level, a marked stereospecificity of geminal and vicinal (125)Te-(1)H spin-spin coupling constants originating in the orientational lone pair effect of tellurium has been established, which opens a new guideline in organotellurium stereochemistry.

Multiple plasmonically induced transparency for chip-scale bandpass filters in metallic nanowaveguides

NASA Astrophysics Data System (ADS)

Lu, Hua; Yue, Zengqi; Zhao, Jianlin

2018-05-01

We propose and investigate a new kind of bandpass filters based on the plasmonically induced transparency (PIT) effect in a special metal-insulator-metal (MIM) waveguide system. The finite element method (FEM) simulations illustrate that the obvious PIT response can be generated in the metallic nanostructure with the stub and coupled cavities. The lineshape and position of the PIT peak are particularly dependent on the lengths of the stub and coupled cavities, the waveguide width, as well as the coupling distance between the stub and coupled cavities. The numerical simulations are in accordance with the results obtained by the temporal coupled-mode theory. The multi-peak PIT effect can be achieved by integrating multiple coupled cavities into the plasmonic waveguide. This PIT response contributes to the flexible realization of chip-scale multi-channel bandpass filters, which could find crucial applications in highly integrated optical circuits for signal processing.

Topological Hall Effect from Strong to Weak Coupling

NASA Astrophysics Data System (ADS)

Nakazawa, Kazuki; Bibes, Manuel; Kohno, Hiroshi

2018-03-01

The topological Hall effect (THE) of electrons coupled to a noncoplanar spin texture has been studied so far for the strong- and weak-coupling regimes separately; the former in terms of the Berry phase and the latter by perturbation theory. In this letter, we present a unified treatment in terms of spin gauge field by considering not only the adiabatic (Berry phase) component of the gauge field but also the nonadiabatic component. While only the adiabatic contribution is important in the strong-coupling regime, it is completely canceled by a part of the nonadiabatic contribution in the weak-coupling regime, where the THE is governed by the remaining nonadiabatic terms. We found a new weak-coupling region that cannot be accessed by a simple perturbation theory, where the Hall conductivity is proportional to M, with 2M being the exchange splitting of the electron spectrum.