Weak Pair Research Articles

Electronic Tuning and Uniform Superconductivity inCeCoIn5

We report a globally reversible effect of electronic tuning on the magnetic phase diagram in CeCoIn(5) driven by electron (Pt and Sn) and hole (Cd, Hg) doping. Consequently, we are able to extract the superconducting pair breaking component for hole and electron dopants with pressure and codoping studies, respectively. We find that these nominally nonmagnetic dopants have a remarkably weak pair breaking effect for a d-wave superconductor. The pair breaking is weaker for hole dopants, which induce magnetic moments, than for electron dopants. Furthermore, both Pt and Sn doping have a similar effect on superconductivity despite being on different dopant sites, arguing against the notion that superconductivity lives predominantly in the CeIn(3) planes of these materials. In addition, we shed qualitative understanding on the doping dependence with density functional theory calculations.

Coupling quantum interpretative techniques: another look at chemical mechanisms in organic reactions.

A cross ELF-NCI analysis is tested over prototypical organic reactions. The synergetic use of ELF and NCI enables the understanding of reaction mechanisms since each method can respectively identify regions of strong and weak electron pairing. Chemically intuitive results are recovered and enriched by the identification of new features. Non covalent interactions are found to foresee the evolution of the reaction from the initial steps. Within NCI, no topological catastrophe is observed as changes are continuous to such an extent that future reaction steps can be predicted from the evolution of the initial NCI critical points. Indeed, strong convergences through the reaction paths between ELF and NCI critical points enable to identify key interactions at the origin of the bond formation. VMD scripts enabling the automatic generation of movies depicting the cross NCI/ELF analysis along a reaction path (or following a Born-Oppenheimer molecular dynamics trajectory) are provided as S.I.

An ultra low noise telecom wavelength free running single photon detector using negative feedback avalanche diode

It is challenging to implement genuine free running single-photon detectors for the 1550 nm wavelength range with simultaneously high detection efficiency (DE), low dark noise, and good time resolution. We report a novel read out system for the signals from a negative feedback avalanche diode (NFAD) [M. A. Itzler, X. Jiang, B. Nyman, and K. Slomkowski, "Quantum sensing and nanophotonic devices VI," Proc. SPIE 7222, 72221K (2009); X. Jiang, M. A. Itzler, K. ODonnell, M. Entwistle, and K. Slomkowski, "Advanced photon counting techniques V," Proc. SPIE 8033, 80330K (2011); M. A. Itzler, X. Jiang, B. M. Onat, and K. Slomkowski, "Quantum sensing and nanophotonic devices VII," Proc. SPIE 7608, 760829 (2010)], which allows useful operation of these devices at a temperature of 193 K and results in very low darkcounts (∼100 counts per second (CPS)), good time jitter (∼30 ps), and good DE (∼10%). We characterized two NFADs with a time-correlation method using photons generated from weak coherent pulses and photon pairs produced by spontaneous parametric down conversion. The inferred detector efficiencies for both types of photon sources agree with each other. The best noise equivalent power of the device is estimated to be 8.1 × 10(-18) W Hz(-1/2), more than 10 times better than typical InP/InGaAs single photon avalanche diodes (SPADs) show in free running mode. The afterpulsing probability was found to be less than 0.1% per ns at the optimized operating point. In addition, we studied the performance of an entanglement-based quantum key distribution (QKD) using these detectors and develop a model for the quantum bit error rate that incorporates the afterpulsing coefficients. We verified experimentally that using these NFADs it is feasible to implement QKD over 400 km of telecom fiber. Our NFAD photon detector system is very simple, and is well suited for single-photon applications where ultra-low noise and free-running operation is required, and some afterpulsing can be tolerated.

Tuning Smart Microgel Swelling and Responsive Behavior through Strong and Weak Polyelectrolyte Pair Assembly

The layer-by-layer (LbL) assembly of polyelectrolyte pairs on temperature and pH-sensitive cross-linked poly(N-isopropylacrylamide)-co-(methacrylic acid), poly(NIPAAm-co-MAA), microgels enabled a fine-tuning of the gel swelling and responsive behavior according to the mobility of the assembled polyelectrolyte (PE) pair and the composition of the outermost layer. Microbeads with well-defined morphology were initially prepared by synthesis in supercritical carbon dioxide. Upon LbL assembly of polyelectrolytes, interactions between the multilayers and the soft porous microgel led to differences in swelling and thermoresponsive behavior. For the weak PE pairs, namely poly(L-lysine)/poly(L-glutamic acid) and poly(allylamine hydrochloride)/poly(acrylic acid), polycation-terminated microgels were less swollen and more thermoresponsive than native microgel, whereas polyanion-terminated microgels were more swollen and not significantly responsive to temperature, in a quasi-reversible process with consecutive PE assembly. For the strong PE pair, poly(diallyldimethylammonium chloride)/poly(sodium styrene sulfonate), the differences among polycation and polyanion-terminated microgels are not sustained after the first PE bilayer due to extensive ionic cross-linking between the polyelectrolytes. The tendencies across the explored systems became less noteworthy in solutions with larger ionic strength due to overall charge shielding of the polyelectrolytes and microgel. ATR FT-IR studies correlated the swelling and responsive behavior after LbL assembly on the microgels with the extent of H-bonding and alternating charge distribution within the gel. Thus, the proposed LbL strategy may be a simple and flexible way to engineer smart microgels in terms of size, surface chemistry, overall charge and permeability.

Nonexpansive retracts and weak compatible pairs in metric Spaces

In this article, we introduce a new approach to common fixed point theory for a weak compatible pair. We first introduce the concepts of R-pair and NR-pair and establish some new common fixed point theorems for a weak compatible pair in hyperconvex metric spaces and uniformly convex metric spaces. We shall also establish the well-known De Marr's theorem for a family of weak compatible pairs in a hyperconvex metric space [0,1] and show by an example that it fails to hold in general hyperconvex metric spaces.Mathematics Subject Classification (2000): Primary 06F30, 46B20, 47E10.

Topologicald-wave pairing structures in Jain states

We discuss d-wave topological (broken time reversal symmetry) pairing structures in unpolarized and polarized Jain states. We demonstrate pairing in the Jain spin singlet state by rewriting it in an explicit pairing form, in which we can recognize d-wave weak pairing of underlying quasiparticles - neutral fermions. We find and describe the root configuration of the Jain spin singlet state and its connection with neutral excitations of the Haldane-Rezayi state, and study the transition between these states via exact diagonalization. We find high overlaps with the Jain spin singlet state upon a departure from the hollow core model for which the Haldane-Rezayi state is the exact ground state. Due to a proven algebraic identity we were able to extend the analysis of topological d-wave pairing structures to polarized Jain states and integer quantum Hall states, and discuss its consequences.

Gutzwiller projected wave functions in the fermionic theory ofS=1spin chains

We study in this paper a series of Gutzwiller Projected wavefunctions for S=1 spin chains obtained from a fermionic mean-field theory for general S>1/2 spin systems [Phys. Rev. B 81, 224417] applied to the bilinear-biquadratic (J-K) model. The free-fermion mean field states before the projection are 1D paring states. By comparing the energies and correlation functions of the projected pairing states with those obtained from known results, we show that the optimized Gutzwiller projected wavefunctions are very good trial ground state wavefunctions for the antiferromagnetic bilinear-biquadratic model in the regime K<J, (J>0). We find that different topological phases of the free-fermion paring states correspond to different spin phases: the weak pairing (topologically non-trivial) state gives rise to the Haldane phase, whereas the strong pairing (topologically trivial) state gives rise to the dimer phase. In particular the mapping between the Haldane phase and Gutwziller wavefunction is exact at the AKLT point K=1/3. The transition point between the two phases determined by the optimized Gutzwiller Projected wavefunction is in good agreement with the known result. The effect of Z2 gauge fluctuations above the mean field theory is analyzed.

Shallow water equations: viscous solutions and inviscid limit

We establish the inviscid limit of the viscous shallow water equations to the Saint-Venant system. For the viscous equations, the viscosity terms are more degenerate when the shallow water is close to the bottom, in comparison with the classical Navier-Stokes equations for barotropic gases; thus, the analysis in our earlier work for the classical Navier-Stokes equations does not apply directly, which require new estimates to deal with the additional degeneracy. We first introduce a notion of entropy solutions to the viscous shallow water equations and develop an approach to establish the global existence of such solutions and their uniform energy-type estimates with respect to the viscosity coefficient. These uniform estimates yield the existence of measure-valued solutions to the Saint-Venant system generated by the viscous solutions. Based on the uniform energy-type estimates and the features of the Saint-Venant system, we further establish that the entropy dissipation measures of the viscous solutions for weak entropy-entropy flux pairs, generated by compactly supported C2 test-functions, are confined in a compact set in H−1, which yields that the measure-valued solutions are confined by the Tartar-Murat commutator relation. Then, the reduction theorem established in Chen and Perepelitsa [5] for the measure-valued solutions with unbounded support leads to the convergence of the viscous solutions to a finite-energy entropy solution of the Saint-Venant system with finite-energy initial data, which is relative with respect to the different end-states of the bottom topography of the shallow water at infinity. The analysis also applies to the inviscid limit problem for the Saint-Venant system in the presence of friction.

Topology of septics with the set of singularities [formula omitted] and [formula omitted]-equivalent weak Zariski pairs

We study the topology of the moduli space of septics with the set of singularities B4,4⊕2A3⊕5A1. In particular, we construct a new π1-equivalent weak Zariski pair.

Constructing an ample monoid from a weak Loganathan pair

This paper is based on a categorical approach to the study of inverse monoids. The main idea is to extend this to the class called ample monoids (type A monoids). We generalise the notion of a Loganathan category pair to obtain what we call a weak Loganathan category pair and take two categories associated with an ample monoid and examine their properties. We prove that each of these categories together with its subcategory of idempotents forms a weak Loganathan category pair. Then we construct an ample monoid from them.

Finite symmetry transformation group of the Konopelchenko—Dubrovsky equation from its Lax pair

Starting from a weak Lax pair, the general Lie point symmetry group of the Konopelchenko—Dubrovsky equation is obtained by using the general direct method. And the corresponding Lie algebra structure is proved to be a Kac—Moody—Virasoro type. Furthermore, a new multi-soliton solution for the Konopelchenko—Dubrovsky equation is also given from this symmetry group and a known solution.

Monte Carlo predictions of phase equilibria and structure for dimethyl ether + sulfur dioxide and dimethyl ether + carbon dioxide

A new force field for dimethyl ether (DME) based on the Lennard-Jones (LJ) 12-6 plus point charge functional form is presented in this work. This force field reproduces experimental saturated liquid and vapor densities, vapor pressures, heats of vaporization, and critical properties to within the statistical uncertainty of the combined experimental and simulation measurements for temperatures between the normal boiling and critical point. Critical parameters and normal boiling point are predicted to within 0.1% of experiment. This force field is used in grand canonical histogram reweighting Monte Carlo simulations to predict the pressure composition diagrams for the binary mixtures DME + SO(2) at 363.15 K and DME + CO(2) at 335.15 and 308.15 K. For the DME + SO(2) mixture, simulation is able to qualitatively reproduce the minimum pressure azeotropy observed experimentally for this mixture, but quantitative errors exist, suggesting that multibody effects may be important in this system. For the DME + CO(2) mixture, simulation is able to predict the pressure-composition behavior within 1% of experimental data. Simulations in the isobaric-isothermal ensemble are used to determine the microstructure of DME + SO(2) and DME + CO(2) mixtures. The DME + SO(2) shows weak pairing between DME and SO(2) molecules, while no specific pairing or aggregation is observed for mixtures of DME + CO(2).

Self-consistent pairing interaction and collective motion in nuclei: a semiclassical approach

The solutions of the semiclassical time–dependent Hartree–Fock-Bogoliubov equations of motion are studied in a linear approximation in which the pairing field is allowed to oscillate and to become complex. The pairing field fluctuations are derived from the self–consistent relation (the gap equation of the BCS type), while the static pairing field is approximated with a phenomenological constant Δ. The self–consistent pairing-field fluctuations introduce possibility of new collective modes of the system. We have found out the dispersion relation which determines possible collective modes of the system generated by the pairing interaction. The obvious solution of our dispersion relation at ω=0 corresponds to the Anderson–Goldstone–Nambu mode and is related to gauge symmetry. The solutions of dispersion relation have been studied in a simple model, in which nuclei are represented as homogeneous spheres of symmetric nuclear matter characterized by parameters (size, density, pairing gap) typical of heavy nuclei. We have found that the dispersion relation has approximate solution at ħω≈2Δ for the monopole channel. Our semiclassical approach is valid for both weak and strong pairing. Here we focus on weak pairing which is suitable for systems with size and pairing parameter appropriated to nuclei.

Explanation of a strange bulk-edge equality

In the infrared limit the N-particle ground-state wavefunctions of the bulk happen to be exactly equal to the N-point space-time correlation functions for certain topological superconductors. We explain this (1), beginning with the p+ip state in D=2+1. We write Z(J), the generating function for wavefunctions, as a path Euclidean integral. Varying the chemical potential as a function of Euclidean time between weak and strong pairing states is shown to extract the wavefunction. Upon a Euclidean rotation that exchanges time and space, approximate Lorentz invariance converts the system to one with a spatial edge and Z(J) to the generator of spacetime correlation functions for the edge fields. We also provide a D=3+1 example, superfluid 3 He- B, and a p- wave superfluid in D=1+1. Our method works only when particle number is not conserved, as in superconductors. 1 Life at the edge The boundaries or edges of condensed matter systems re- ceived scant attention until recent developments showed them to be fertile areas of research both in the Fractional Quantum Hall E ect (FQHE) (1-3). and in topological in- sulators and superconductors (4,5,7,6,8-10). These works established that in certain topological insulators (which in- cludes superconductors because they are gapped in the bulk) the edges or boundaries carry gapless excitations which are unusual. The edge modes are saved from acquiring a gap due to various impurities because of the underlying topo- logical quantum number. The edge modes in a d 1 dimen- sional boundary of a bulk system in d dimensions cannot exist in generic d 1 dimensional systems that were not boundaries. For example the edge state at the d = 2 sur- face of a certain d = 3 insulator is described at low ener- gies by a single Dirac cone, while a generic d = 2 system

Effective Field Theory for Top and Weak Boson Physics

Effective field theory is the ideal framework for discussing top and weak boson properties. We discuss the application of this framework to top physics at both tree level and one loop. We consider weak boson pair production within an effective field theory framework, and argue that one need not be concerned with the violation of unitarity bounds at energies beyond the region where there are data.

Base-pairing selectivity of a ureido-linked phenyl-2′-deoxycytidine derivative

Incorporation of modified nucleotides into nucleic acid strands often produces conformational constraints and steric hindrances that may change the property of base pairing. In this study, we investigated a 2'-deoxycytidine derivative that tethers a phenyl moiety to the exocyclic amino group of cytosine linked through a ureido group. This derivative compound is structurally similar to the carbamoylated DNA base lesions produced in cells. The thermodynamic and structural studies showed that the modified dC formed the base pair with dG in the complementary strand, but the base-pairing selectivity toward dG was decreased under poly(ethylene glycol)-mediated osmotic stress. The phenyl group and the ureido linker attached to dC provided selectivity for the formation of base pairing exclusively with dG in a wide range of pH conditions, whereas unmodified dC stabilized the pairings with dA or dC in acidic solutions. Moreover, this modified base could not form self-pairing through intermolecular hydrogen bonds. We suggest that formation of weak pairing and protonation of the cytosine base are hindered due to the base modification. These data provide insights into the pairing selectivity of carbamoylated cytosine lesions produced in cells, and suggest applications of the 2'-deoxycytidine derivatives in medical technologies, molecular biology experiments, and synthesis of a supramolecular network of DNA strands.

DNA Sequence Context Conceals α-Anomeric Lesions

DNA sequence context has long been known to modulate detection and repair of DNA damage. Recent studies using experimental and computational approaches have sought to provide a basis for this observation. We have previously shown that an α-anomeric adenosine (αA) flanked by cytosines (5′CαAC-3′) resulted in a kinked DNA duplex with an enlarged minor groove. Comparison of different flanking sequences revealed that a DNA duplex containing a 5′CαAG-3′ motif exhibits unique substrate properties. However, this substrate was not distinguished by unusual thermodynamic properties. To understand the structural basis of the altered recognition, we have determined the solution structure of a DNA duplex with a 5′CαAG-3′ core, using an extensive set of restraints including dipolar couplings and backbone torsion angles. The NMR structure exhibits an excellent agreement with the data (total RX <5.3%). The αA base is intrahelical, in a reverse Watson–Crick orientation, and forms a weak base pair with a thymine of the opposite strand. In comparison to the DNA duplex with a 5′CαAC-3′ core, we observe a significant reduction of the local perturbation (backbone, stacking, tilt, roll, and twist), resulting in a straighter DNA with narrower minor groove. Overall, these features result in a less perturbed DNA helix and obscure the presence of the lesion compared to the 5′CαAC-3′ sequence. The improved stacking of the 5′CαAG-3′ core also affects the energetics of the DNA deformation that is required to form a catalytically competent complex. These traits provide a rationale for the modulation of the recognition by endonuclease IV.

Pair bonding and lateral neck-resting preferences in captive Caribbean flamingos (Phoenicopterus ruber)

When flamingos rest, they typically lay their head on their back and curve their neck to either the right or left of their body, with both individual and population-level lateral preferences for rightward neck resting when preferences are tracked over time (Anderson, Williams, & O'Brien, 2009). The present study attempted to replicate these previous neck-resting preferences, to examine how they changed over time, and to examine the possibility of a relationship between lateral neck-resting preference and pair bonding in captive Caribbean flamingos (Phoenicopterus ruber) housed at the Philadelphia Zoo (Philadelphia, PA, USA). Results successfully replicated the individual- and population-level lateral preferences for rightward neck resting, and demonstrated that these preferences were stable over time. Moreover, individual flamingos that demonstrated stronger pair bond strengths tended to differ less from their partners in terms of neck-resting preference than did those birds displaying weaker pair bond strengths, suggesting a relationship between laterality and social cohesion.

Densities, Viscosities [from (278.15 to 318.15) K], and Electrical Conductivities (at 298.15 K) of Aqueous Solutions of Choline Chloride and Chloro-Choline Chloride

Data for the electrical conductivity (at 298.15 K), density, and viscosity [both at (278.15, 288.15, 298.15, 308.15, and 318.15) K] of aqueous solutions of choline chloride (ChCl) and chloro-choline chloride (Cl-ChCl) are reported for solute molalities m ≲ 2.0 mol·kg–1 (ChCl) and ≲ 2.1 mol·kg–1 (Cl-ChCl), respectively. From the densities apparent molar volumes were calculated, and the limiting partial molar volumes and Hepler's constants of ChCl(aq) and Cl-ChCl(aq) were evaluated. From the viscosities Arrhenius activation energies of viscous flow were determined. While apparent molar volumes suggest at best weak ion pairing for ChCl(aq) and Cl-ChCl(aq), the Walden product obtained for 25 °C hints at significant ion–ion interactions and/or changes in ion hydration with increasing concentration.

An efficient local coupled cluster method for accurate thermochemistry of large systems

An efficient local coupled cluster method with single and double excitation operators and perturbative treatment of triple excitations [DF-LCCSD(T)] is described. All required two-electron integrals are evaluated using density fitting approximations. These have a negligible effect on the accuracy but reduce the computational effort by 1-2 orders of magnitude, as compared to standard integral-direct methods. Excitations are restricted to local subsets of non-orthogonal virtual orbitals (domain approximation). Depending on distance criteria, the correlated electron pairs are classified into strong, close, weak, and very distant pairs. Only strong pairs, which typically account for more than 90% of the correlation energy, are optimized in the LCCSD treatment. The remaining close and weak pairs are approximated by LMP2 (local second-order Mo̸ller-Plesset perturbation theory); very distant pairs are neglected. It is demonstrated that the accuracy of this scheme can be significantly improved by including the close pair LMP2 amplitudes in the LCCSD equations, as well as in the perturbative treatment of the triples excitations. Using this ansatz for the wavefunction, the evaluation and transformation of the two-electron integrals scale cubically with molecular size. If local density fitting approximations are activated, this is reduced to linear scaling. The LCCSD iterations scale quadratically, but linear scaling can be achieved by neglecting some terms involving contractions of single excitations. The accuracy and efficiency of the method is systematically tested using various approximations, and calculations for molecules with up to 90 atoms and 2636 basis functions are presented.