Sizable Enhancement Research Articles

Quasi-particle interaction in nuclear matter from chiral pion–nucleon dynamics

Based on a recent chiral approach to nuclear matter we calculate the in-medium interaction of nucleons at the Fermi surface | p → 1 , 2 | = k f . The isotropic part of this quasi-particle interaction is characterized by four density-dependent (dimensionful) Fermi-liquid parameters: f 0 ( k f ) , f 0 ′ ( k f ) , g 0 ( k f ) and g 0 ′ ( k f ) . In the approximation to 1 π-exchange and iterated 1 π-exchange (which as such leads already to a good nuclear matter equation of state) we find a spin–isospin interaction strength of g 0 ′ ( 2 m π ) = 1.14 fm 2 , compatible with existing empirical values. The consistency relations to the nuclear matter compressibility K and the spin/isospin asymmetry energies serve as a check on our perturbative calculation. In the next step we include systematically the contributions from 2 π-exchange with virtual Δ ( 1232 ) -isobar excitation which have been found important for good single-particle properties and spin-stability of nuclear matter. Without any additional short-distance terms (contributing proportional to k f 2 ) the spin-dependent Fermi-liquid parameters g 0 ( k f 0 ) and g 0 ′ ( k f 0 ) come out far too large. Estimates of these short-distance parameters from realistic NN-potentials go in the right direction, but sizeable enhancement factors are still needed to reproduce the empirical values of g 0 ( k f 0 ) and g 0 ′ ( k f 0 ) . This points towards the importance of higher order iterations subsumed in the induced interaction. We consider also the tensor part of the quasi-nucleon interaction at the Fermi surface. In comparison to the leading 1 π-exchange tensor interaction we find from the 2 π-exchange corrections almost a doubling of the isoscalar tensor strength h 0 ( k f ) , whereas the isovector tensor strength h 0 ′ ( k f ) is much less affected. These features are not changed by the inclusion of the chiral πNΔ-dynamics. The l = 1 tensor Fermi-liquid parameters h 1 ( k f ) and h 1 ′ ( k f ) follow a similar pattern.

Relativistic effects in neutrino–Fermi gas interactions

We study neutrino interactions in a hadron gas within a relativistic framework. The hadron matter is described by a non-interacting Fermi gas in beta equilibrium. We show that the introduction of relativistic effects causes a sizable enhancement of the neutrino-scattering cross sections.

Organic thin-film transistor sensors: Interface dependent and gate bias enhanced responses

Organic thin film transistors are a new class of sensors potentially capable of outperforming chemiresistors. They can be operated at room temperature, offer the advantage of remarkable response repeatability and can function as multi-parameter sensors. In this paper, evidence of OTFT response dependence on important parameters such as the chemical nature of the organic semiconductor active layer and the gate-dielectric/organic-semiconductor interface are produced. A sizable response enhancement of an OTFT sensor operated in the enhancement mode is also presented indicating that an OTFT can in principle lead to a lower detection limit than a resistor-type sensor with the same organic semiconductor.

Anomaly inYBa2Cu4O8charge distribution belowTc: A zero-field muon spin relaxation study

Zero-field $\mu$SR measurements in $^{63}$Cu isotope enriched and natural YBa$_2$Cu$_4$O$_8$ powders are presented. The temperature dependence of the $\mu^+$ relaxation rate is characterized by a sizeable enhancement below T$_c$. The comparison of the asymmetry decay in the two samples reveals that the $\mu^+$ relaxation is driven by nuclear dipole interaction from 300 K down to 4.2 K. It is argued that the increase in the relaxation below T$_c$ originates from a change in $\mu^+$ site, possibly due to a modification in the charge distribution within CuO chains.

Interface and gate bias dependence responses of sensing organic thin-film transistors

The effects of the exposure of organic thin-film transistors, comprising different organic semiconductors and gate dielectrics, to 1-pentanol are investigated. The transistor sensors exhibited an increase or a decrease of the transient source-drain current in the presence of the analyte, most likely as a result of a trapping or of a doping process of the organic active layer. The occurrence of these two effects, that can also coexist, depend on the gate-dielectric/organic semiconductor interface and on the applied gate field. Evidence of a systematic and sizable response enhancement for an OTFT sensor operated in the enhanced mode is also presented.

Inclusive production of single hadrons with finite transverse momenta in deep-inelastic scattering at next-to-leading order

We calculate the cross section for the inclusive production of single hadrons with finite transverse momenta in deep-inelastic scattering at next-to-leading order (NLO), i.e., through O ( α s 2 ) , in the parton model of QCD endowed with non-perturbative parton distribution functions (PDFs) and fragmentation functions (FFs). The NLO correction is found to produce a sizeable enhancement in cross section, of up to one order of magnitude, bringing the theoretical prediction to good agreement with recent measurements for neutral pions and charged hadrons at DESY HERA. This provides a useful test for the universality and the scaling violations of the FFs predicted by the factorization theorem.

Organic Thin-Film Transistor Sensors: Interface Dependent and Gate Bias Enhanced Responses

AbstractOrganic Thin Film Transistors are a new class of sensors potentially capable of outperforming chemiresistors. They can be operated at room temperature, offer the advantage of remarkable response repeatability and can function as multi-parameter sensors. In this paper evidence of OTFT response dependence on important parameters such as the chemical nature of the organic semiconductor active layer and the gate-dielectric/organic-semiconductor interface are produced. A sizable response enhancement of an OTFT sensor operated in the enhancement mode is also presented indicating that an OTFT can in principle lead to a lower detection limit than a resistor-type sensor with the same organic semiconductor.

Consistent description of quantum Brownian motors operating at strong friction

A quantum Smoluchowski equation is put forward that consistently describes thermal quantum states. In particular, it notably does not induce a violation of the second law of thermodynamics. This so modified kinetic equation is applied to study analytically directed quantum transport at strong friction in arbitrarily shaped ratchet potentials that are driven by nonthermal two-state noise. Depending on the mutual interplay of quantum tunneling and quantum reflection these quantum corrections can induce both, a sizable enhancement or a suppression of transport. Moreover, the threshold for current reversals becomes markedly shifted due to such quantum fluctuations.

Field-controlled domain-wall resistance in magnetic nanojunctions

The electrical resistance of a constrained domain wall in a nanojunction is investigated using micromagnetic modeling and ballistic conductance calculations. The nanojunction represents two ferromagnetic electrodes connected by a ferromagnetic wire of 10 nm in length and of a few nanometers in cross section. We find that the anisotropy of the electrodes favors a localization of the domain wall within the constriction (wire) revealing a positive domain-wall resistance. An applied magnetic field moves the domain wall toward one of the electrodes and reduces its width. This compression of the domain wall leads to a sizeable enhancement of the domain-wall resistance.

Anisotropy of the incommensurate fluctuations in Sr2RuO4: a study with polarized neutrons.

The anisotropy of the magnetic incommensurate fluctuations in Sr2RuO4 has been studied by inelastic neutron scattering with polarized neutrons. We find a sizable enhancement of the out-of-plane component by a factor of 2 for intermediate energy transfer, which appears to decrease for higher energies. Our results qualitatively confirm calculations of the spin-orbit coupling, but the experimental anisotropy and its energy dependence are weaker than predicted.

Higgs boson couplings to quarks with supersymmetric CP and flavor violations

In minimal supersymmetric model (SUSY) with a light Higgs sector, explicit CP violation and most general flavor mixings in the sfermion sector, integration of the superpartners out of the spectrum induces potentially large contributions to the Yukawa couplings of light quarks via those of the heavier ones. These corrections can be sizeable even for moderate values of tanβ, and remain nonvanishing even if all superpartners decouple. When the SUSY breaking scale is close to the electroweak scale, the Higgs exchange effects can compete with the gauge boson and box diagram contributions to rare processes, and their partial cancellations can lead to relaxation of the existing bounds on flavor violation sources. In this case there exist sizeable enhancements in flavor-changing Higgs decays. When the superpartners completely decouple, however, the Higgs mediation becomes the dominant SUSY contribution to rare processes the saturation of which, without a strong suppression of the flavor mixings, prefers large tanβ and certain ranges for the CP-odd phases. The decay rate of the lightest Higgs into light down quarks becomes comparable with that into the bottom quark. Moreover, the Higgs decay into the up quark is significantly enhanced. There are observable implications for rare processes, atomic electric dipole moments, and collider searches for Higgs bosons.

Thermodynamics of a trapped Bose-Fermi mixture

By using the Hartree-Fock-Bogoliubov equations within the Popov approximation, we investigate the thermodynamic properties of a dilute binary Bose-Fermi mixture confined in an isotropic harmonic trap. For mixtures with an attractive Bose-Fermi interaction we find a sizable enhancement of the condensate fraction and of the critical temperature of Bose-Einstein condensation with respect to the predictions for a pure interacting Bose gas. Conversely, the influence of the repulsive Bose-Fermi interaction is less pronounced. The possible relevance of our results in current experiments on trapped $^{87}{\rm Rb}-^{40}${\rm K} mixtures is discussed.

Polaronic features in the Su–Schrieffer–Heeger model

A diagrammatic perturbative study of (i) effective mass and (ii) electron spectral function versus the adiabatic parameter in the Su–Schrieffer–Heeger model is presented. When zone boundary phonons energetically compete with band electrons we observe a sizeable mass enhancement. In two dimensions, a spread of the spectral weight signals the onset of polaron formation.

Sizeable enhancement of anti-weak localization effect in In 2O 3− x thin film caused by H 2 gas mixing in N 2 gas atmosphere on heat treatment

Through magneto-conductance measurements, we have observed sizeable enhancement of anti-weak localization (AWL) effect in In 2O 3− x thin film ( 60 nm ) caused by H 2 gas mixing (10%) in N 2 gas (90%) atmosphere on the heat treatment (HT). In case of the HT in pure N 2 gas, the AWL effect is recognized, but is very small. With respect to those experimental results, we conclude that interstitial indium atoms in In 2O 3− x are effectively generated and the AWL effect due to the spin–orbit interaction is come up.

Calix[4]arene, calix[4]resorcarene, and cyclodextrin derivatives and their lanthanide complexes as chiral NMR shift reagents.

Calix[4]arenes, calix[4]resorcarenes, and anionic cyclodextrin derivatives were examined as chiral NMR solvating agents. The calix[4]arenes were prepared by attachment of amino acids through the hydroxyl groups of the phenol rings. Chloroform-, methanol-, and water-soluble derivatives were prepared and tested with a range of substrates. Chloroform-soluble chiral calix[4]resorcarenes were prepared by attachment of chiral primary and secondary amines and examined in NMR applications with a variety of substrates. Sulfated and carboxymethylated beta-cyclodextrin are effective at causing enantiomeric discrimination in the (1)H NMR spectra of organic cations. Lanthanide ions associate at the carboxymethyl groups and cause sizeable shifts and enhancements in enantiomeric discrimination in the spectra of organic cations. The enhancements caused by the lanthanide ion are large enough that much lower concentrations of the cyclodextrin can be used as compared to conventional analyses.

Weak production of strangeness at threshold with polarization observables

The differential cross section for the charged current electroweak reaction e→+p→ν→e+Λ→ at threshold with polarization observables is presented. The form of the cross section at threshold for the reaction is simplified compared to higher energy. An expression is given for the invariant matrix element appropriate for the reaction when the incident electron is polarized, and the final state hyperon polarization is determined. The energy dependence of the resulting cross section is shown near threshold. Under the right kinematic conditions, there can be a sizeable enhancement in the cross section, making an experimental measurement of the weak axial-vector form factor feasible.

Dimensionality effects on the Su–Schrieffer–Heeger model

A low order diagrammatic study of the dimension-dependent Su–Schrieffer–Heeger model Hamiltonian in the weak electron–phonon coupling regime is presented. Exact computation of both the charge carrier effective mass and the electron spectral function shows that electrons are good quasi-particles in the anti-adiabatic limit but new features emerge in the adiabatic and intermediate regime, where the phonons and the electrons compare on the energy scale. Here we find: (i) a sizeable mass enhancement over the bare band value, (ii) the appearance of many transition peaks in the band bottom spectral function together with a growing loss of spectral weight at larger e–ph couplings. The onset of a polaronic state is favoured in two-dimensions.

The hemostatic agent ethamsylate enhances P-selectin membrane expression in human platelets and cultured endothelial cells

Ethamsylate possesses antihemorrhagic properties, but whether or not it directly activates blood platelets is unclear. Here we investigated the platelet activation potential of ethamsylate, by measuring membrane P-selectin expression with flow cytometry in human whole blood and also by immunofluorescence imaging of isolated human platelets. Moreover, we measured membrane P-selectin expression in the SV40-transformed aortic rat endothelial cell line (SVAREC) and 14C-ethamsylate membrane binding and/or uptake in platelets and endothelial cells. Whole blood flow cytometry showed a modest, but statistically significant increase by ethamsylate in the percentage of platelets expressing P-selectin (from 2% to 4–5%, p<0.05). Immunofluorescence showed a sizable (39%) and significant ( p<0.01) enhancement of P-selectin expression at the lowest concentration of ethamsylate tested (1 μM), with maximal enhancement of P-selectin expression (75–90%) at 10 μM ethamsylate. Similar results were obtained in SVAREC endothelial cells. 14C-ethamsylate specifically bound to platelets and endothelial cell membranes, without significant uptake into the cell interior. In conclusion, ethamsylate enhances membrane P-selectin expression in human platelets and in cultured endothelial cells. Ethamsylate specifically binds to some protein receptor in platelet and endothelial cell membranes, receptor which can signal for membrane P-selectin expression. These results support the view that ethamsylate acts on the first step of hemostasis, by improving platelet adhesiveness and restoring capillary resistance.

Generalized semirigid vibrating rotor target model for atom–poly reaction: Inclusion of umbrella mode for H+CH4 reaction

In this work, we present a generalized version of the semirigid vibrating rotor target (SVRT) model by including additional vibrational modes explicitly in the SVRT Hamiltonian. The inclusion of additional vibrational modes eliminates the uncertainty of fixing certain geometries of the target molecule as required in the basic SVRT model. This generalized SVRT (GSVRT) model was employed to study the benchmark reaction H+CH4 by including the umbrella mode of CH4. Influence of the umbrella mode of the reagent on reactivity is investigated. It is concluded that the inclusion of the umbrella vibrational mode of CH4 has only a small effect on the reaction from the ground state of the reagent, and essentially no effect from the excited C–H stretching vibrational state of the reagent. However, the initial excitation of the umbrella mode does give a sizable enhancement of reaction and reduces the reaction barrier by about 1.1 kcal/mol.

Spectral properties of the Su–Schrieffer–Heeger model

We present a study of the one dimensional Su–Schrieffer–Heeger model Hamiltonian by a diagrammatic perturbative method in the weak electron–phonon (e–ph) coupling regime. Exact computation of both the charge carrier effective mass and the electron spectral function shows that electrons are good quasiparticles in the adiabatic and antiadiabatic limits but novel features emerge in the intermediate regime, where the phonons and the electrons compare on the energy scale. Together with a sizeable mass enhancement we observe, in the latter regime, a spread of the spectral weight (among several transition peaks) associated with an increased relevance of multiphonons contributions at larger e–ph couplings. Accordingly electrons cease to be the good quasiparticles and an onset of polaron formation is favoured.