Large Coupling Constant Research Articles

Vortex Phases of Rotating Superfluids

We report on the first mathematically rigorous proofs of a transition to a giant vortex state of a superfluid in rotating anharmonic traps. The analysis is carried out within two-dimensional Gross-Pitaevskii theory at large coupling constant and large rotational velocity and is based on precise asymptotic estimates on the ground state energy. An interesting aspect is a significant difference between 'soft' anharmonic traps (like a quartic plus quadratic trapping potential) and traps with a fixed boundary. In the former case vortices persist in the bulk until the width of the annulus becomes comparable to the size of the vortex cores. In the second case the transition already takes place in a parameter regime where the size of vortices is very small relative to the width of the annulus. Moreover, the density profiles in the annulus are different in the two cases. In both cases rotational symmetry of the density in a true ground state is broken, even though a symmetric variational ansatz gives an excellent approximation to the energy.

An A 4 × $ {{\mathbb{Z}}_4} $ model for neutrino mixing

The A4 x U(1) flavor model of He, Keum, and Volkas is extended to provide a minimal modification to tribimaximal mixing that accommodates a nonzero reactor angle theta13 ~ 0.1. The sequestering problem is circumvented by forbidding superheavy scales and large coupling constants which would otherwise generate sizable RG flows. The model is compatible with (but does not require) a stable or metastable dark matter candidate in the form of a complex scalar field with unit charge under a discrete subgroup Z4 of the U(1) flavor symmetry.

Nonperturbative Master Equation Solution of Central Spin Dephasing Dynamics

We solve the long-standing central spin problem for a general set of inhomogeneous bath couplings and a large class of initial bath states. We compute the time evolution of the coherence of a central spin coupled to a spin bath by resumming all orders of the time-convolutionless master equation, thus avoiding the need to assume weak coupling to the bath. The fully quantum, non-markovian solution is obtained in the large-bath limit and is valid up to a time scale set by the largest coupling constant. Our result captures the full decoherence of an electron spin qubit coupled to a nuclear spin bath in a GaAs quantum dot for experimentally relevant parameters. In addition, our solution is quite compact and can readily be used to make quantitative predictions for the decoherence process and to guide the design of nuclear state preparation protocols.

Redox-Active Scandium Oxide Cluster inside a Fullerene Cage: Spectroscopic, Voltammetric, Electron Spin Resonance Spectroelectrochemical, and Extended Density Functional Theory Study of Sc4O2@C80 and Its Ion Radicals

The clusterfullerene Sc(4)O(2)@C(80) with a mixed redox state of scandium was found to be an exciting molecule for endohedral electrochemistry as demonstrated by means of an in situ electron spin resonance (ESR) spectroelectrochemical study of the spin density distribution in its electrochemically generated cation and anion radicals. The compound exhibits two reversible reduction and oxidation steps with a relatively small electrochemical gap of 1.10 V. The ESR spectra of the ion radicals have a rich hyperfine structure caused by two pairs of equivalent Sc atoms. The Sc-based hyperfine structure with large hyperfine coupling constants shows that both oxidation and reduction of Sc(4)O(2)@C(80) are in cavea redox processes, which is the subject of endohedral electrochemistry. The assignment of the experimentally determined a((45)Sc) values to the two types of Sc atoms in the Sc(4)O(2) cluster was accomplished by extended density functional theory and molecular dynamics simulations. Sc atoms adopting a divalent state in the neutral Sc(4)O(2)@C(80) exhibited an especially large coupling constant of 150.4 G in the cation radical, which is the record high a((45)Sc) value for Sc-based endohedral metallofullerenes. Such a high value is explained by the nature of the highest occupied molecular orbital (HOMO) localized on the six-atom Sc(4)O(2) cluster. This HOMO is a Sc-Sc bonding MO and hence has large contributions from the 4s atomic orbitals of Sc(II). We claim that ESR spectroelectrochemistry is an invaluable experimental tool in the studies of metal-metal bonding in endohedral metallofullerenes and in endohedral electrochemistry.

Synthesis of ferrocenyl chalcones of the abietane series

Two isomeric ferrocenyl chalcones having an abietane fragment were synthesized. Accessibility of various ferrocene derivatives, their high chemical stability, and penetrating ability toward membranes make them promising as substrates for conjugation with biomolecules. In recent time, interest in ferrocene derivatives as alternative drugs for chemotherapy of malignant tumors has increased considerably [1]. Some ferrocene derivatives were found to be active against cervix adenocarcinoma HeLa, melanoma Fem-x, and myelogenous leukemia K562 cell lines [2]. In addition, modifications of drugs used in clinical practice with ferrocenyl fragments were reported [3]. Among other ferrocene derivatives, ferrocenylsubstituted chalcones were synthesized [4]. Ferrocenyl derivatives of diterpenes were described in [5], and chalcones containing a dehydroabietic acid residue were reported in [6]. There are no published data on ferrocenyl chalcones linked to diterpene fragments. In the present communication we describe the synthesis of ferrocenyl chalcones of the abietane series and their cytotoxic activity. By condensation of ferrocenecarbaldehyde (I) with methyl (1R,4aS,10aR)-6-acetyl-7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,9,10,10a-octahydrophenantrene-1carboxylate (II, 12-acetyldehydroabietic acid methyl ester) [7] according to Claisen–Schmidt (KOH in methanol) we obtained chalcone III in 35% yield (Scheme 1). Pure trans isomer III was isolated by column chromatography on silica gel, followed by recrystallization from methanol. Its configuration followed from the large coupling constant (J ≈ 15 Hz) for the vinylic protons. Isomeric chalcone VI was synthesized in 4% yield from acetylferrocene (IV) and methyl (1R,4aS,10aR)6-formyl-7-isopropyl-1,4a-dimethyl-1,2,3,4,4a,9,10,10aoctahydrophenanthrene-1-carboxylate (V, 12-formyldehydroabietic acid methyl ester) [8]. Aldehyde V was prepared in turn by the Sommelet reaction of 12-chloromethyl derivative VII [9] (Scheme 2). The low yield of VI may be rationalized by steric hindrances created by the isopropyl group to nucleoDOI: 10.1134/S1070428012060152

Oncocalyxone A: electrochemical, spectroscopic investigation and studies of its interaction with DNA, nucleobases and N-acetylcysteine

The formation of paramagnetic species from oncocalyxone A in aprotic medium was confirmed by performing in situ electrochemical-electron spin resonance (E-ESR) experiments. The high delocalization of the radical generated at the first reduction potential is clearly evidenced by the hyperfine coupling of H-9 with the larger coupling constant, besides the couplings at the H-3 (close to quinone) and H-7 (far from the quinone nucleus) positions. In protic medium, together with pH dependence experiments, oncocalyxone A showed to be DNA-reactive through experiments with DNA sensors. Its reaction with N-acetylcysteine, with structural characterization of the addition products, proved its ability as Michael acceptor. Both aspects are important in terms of biological/pharmacological activities and indicate the present models as important tools in the screening of biologically active compounds.

Multifractal dimensions for all moments for certain critical random-matrix ensembles in the strong multifractality regime

We construct perturbation series for the qth moment of eigenfunctions of various critical random-matrix ensembles in the strong multifractality regime close to localization. Contrary to previous investigations, our results are valid in the region q<1/2. Our findings allow one to verify, at first leading orders in the strong multifractality limit, the symmetry relation for anomalous fractal dimensions Δ(q)=Δ(1-q), recently conjectured for critical models where an analog of the metal-insulator transition takes place. It is known that this relation is verified at leading order in the weak multifractality regime. Our results thus indicate that this symmetry holds in both limits of small and large coupling constant. For general values of the coupling constant we present careful numerical verifications of this symmetry relation for different critical random-matrix ensembles. We also present an example of a system closely related to one of these critical ensembles, but where the symmetry relation, at least numerically, is not fulfilled.

Anharmonic Josephson current in junctions with an interface pair breaking

Planar superconducting junctions with a large effective Josephson coupling constant and a pronounced interface pair breaking are shown to represent weak links with small critical currents and strongly anharmonic current-phase relations. The supercurrent near Tc is described taking into account the interface pair breaking as well as the current depairing and the Josephson coupling-induced pair breaking of arbitrary strengths. A new analytical expression for the anharmonic supercurrent, which is in excellent agreement with the numerical data presented, is obtained. In junctions with a large effective Josephson coupling constant and a pronounced interface pair breaking, the current-induced depairing is substantially enhanced in the vicinity of the interface thus having a crucial influence on the current-phase relation despite a small depairing in the bulk.

The interaction between tea polyphenols and rice starch during gelatinization

The interaction between tea polyphenols (TPLs) and rice starch (RS) during gelatinization has been studied. In the RVA analysis, TPLs-fortified RS exhibited no clearly defined peak viscosity and hot paste viscosity. After excluding other factors, irregular viscosity changes were attributed to the strong interactions between RS and TPLs during pasting/gelatinization. Subsequently, the coupling constants of samples A (the gelatinized sample of the blend of 16% TPLs and RS) and B (the blend of 16% TPLs and gelatinized RS sample) in (1)H-NMR measurements were found to be the difference. Sample A had two coupling constants, (26h)J(HH) = 82.08, 100.77 Hz and (6h)J(HH) = 35.57 Hz, whereas Sample B had one larger coupling constant, (9h)J(HH) = 140.24 Hz. This implied that these two samples differed in H-H interaction and interaction strength of sample A may be stronger than that of sample B. More important is, sample A had clearly broadened O-H stretching and frequency red-shifts of C-O-H bending as compared with sample B in quantitative FT-IR analysis. The overall results indicate that TPLs and RS can have hydrogen bonding interaction during gelatinization.

Rotating superfluids in anharmonic traps: From vortex lattices to giant vortices

We study a superfluid in a rotating anharmonic trap and explicate a rigorous proof of a transition from a vortex lattice to a giant vortex state as the rotation is increased beyond a limiting speed determined by the interaction strength. The transition is characterized by the disappearance of the vortices from the annulus where the bulk of the superfluid is concentrated due to centrifugal forces while a macroscopic phase circulation remains. The analysis is carried out within two-dimensional Gross-Pitaevskii theory at large coupling constant and reveals significant differences between 'soft' anharmonic traps (like a quartic plus quadratic trapping potential) and traps with a fixed boundary: In the latter case the transition takes place in a parameter regime where the size of vortices is very small relative to the width of the annulus whereas in 'soft' traps the vortex lattice persists until the width of the annulus becomes comparable to the vortex cores. Moreover, the density profile in the annulus where the bulk is concentrated is, in the 'soft' case, approximately gaussian with long tails and not of the Thomas-Fermi type like in a trap with a fixed boundary.

EPR study of radical annihilation kinetics of γ-ray-irradiated acrylic (PMMA) at elevated temperatures

High-energy irradiations of polymers may cause bond cleavage or crosslinking and change the structures and physical properties of the polymers, which may offer various applications. Despite wide investigation, relationship between the kinetics and mechanism of annihilation after irradiations and the structure and some physical properties of irradiated polymers is still poorly established. We have been exploring such possible relationship and report herein investigation of the kinetics of radical annihilation of γ-ray irradiated acrylic, i.e., poly(methylmethacrylate) or PMMA, at elevated temperatures with EPR spectroscopy. The EPR spectra consist of three components, a quintet Ra, a quartet Rb, and a broad singlet Rc. Ra and Rb follow second-order annihilation kinetics, while the decay of the radical Rc is comprised of at least two parallel kinetic processes, a slow second-order pathway and a fast pathway which can be equally well fitted to first- or second-order kinetics. The kinetics is analogous to that for the radical decays in irradiated 2-hydroxyethyl methacrylate copolymer. On the basis of the large hyperfine coupling constant of 2.3 mT, Ra may be assigned to a radical adjacent to two groups of protons, such as a doublet of quartet with similar coupling constants due to an anti-methylene proton and a methyl group; the Rb signal, possibly a methyl radical; and the broad singlet Rc, a magnetically coupled combination species. Alternative assignments of the radicals have also been suggested. The rate constant increases with increasing dose for each radical at a given temperature, possibly due to increase in radical concentrations at higher doses. The rate constants satisfy the Arrhenius equation, suggesting a single mechanistic pathway for the annihilation process in the temperature range; wherein the activation energy decreases with increasing dose for all radicals, possibly due to higher concentrations of free radicals in close proximity produced at higher doses.

Cp*(PiPr3)RuOTf: A Reagent for Access to Ruthenium Silylene Complexes

The ruthenium triflate complex Cp*(PiPr3)RuOTf (1) was generated from the reaction of Cp*(PiPr3)RuCl with Me3SiOTf in dibutyl ether. Complex 1 reacted with primary and secondary silanes to produce a family of Ru(IV) silyl dihydride complexes of the type Cp*(PiPr3)Ru(H)2(SiRR′OTf) (3–12). Structural analyses of complexes 8 (R = R′ = Ph) and 12 (R = R′ = fluorenyl) revealed the presence of a tetrahedral silicon center and a four-legged piano stool geometry about ruthenium. Anion abstraction from Cp*(PiPr3)Ru(H)2(SiHROTf) by [Et3Si·toluene][B(C6F5)4] afforded hydrogen-substituted cationic ruthenium silylene complexes [Cp*(PiPr3)Ru(H)2(═SiHR)][B(C6F5)4] (R = Mes (13), R = Si(SiMe3) (14)) that display a significant Ru–H···Si interaction, as indicated by relatively large 2JSiH coupling constants (2JSiH = 58.2 Hz (13), 2JSiH = 37.1 Hz (14)). The syntheses of secondary silylene complexes [Cp*(PiPr3)Ru(H)2(═SiRR′)][B(C6F5)4] (R = R′ = Ph (15); R = Ph, R′ = Me (16), R = R′ = fluorenyl (17)) were also achieved by anion abstraction with [Et3Si·toluene][B(C6F5)4]. Complexes 15–17 do not display strong Ru–H···Si secondary interactions, as indicated by very small 2JSiH coupling constant values.

Factors That Regulate the Conformation of m‐Benziporphodimethene Complexes: Agostic Metal–Arene Interaction, Hydrogen Bonding, and η2,π Coordination

Group 12 and silver(I) tetramethyl-m-benziporphodimethene (TMBPDM) complexes with phenyl, methylbenzoate, or nitrophenyl groups as meso substituents were synthesized and fully characterized. The dimeric silver(I) complex displays an unusual η(2),π coordination from the β-pyrrolic C=C bond to the silver ion. All of the complexes displayed a close contact between the metal ion and the inner C(22)-H(22) on the m-phenylene ring. The downfield chemical shifts of H(22) and large coupling constants between Cd(II) and H(22) strongly support the presence of an agostic interaction between the metal ion and inner C(22)-H(22). Crystal structures revealed that the syn form is the predominant conformation for TMBPDM complexes. This is distinctively different from the exclusive anti conformation observed in m-benziporphyrin and tetraphenyl-m-benziporphodimethene (TPBPDM) complexes. Evidently, intramolecular hydrogen-bonding interactions between axial chloride and methyl groups stabilize syn conformations. Unlike the merely syn conformation observed in the solid-state structures of TMBPDM complexes that contain an axial chloride, in solution these complexes display highly solvent- and temperature-dependent syn/anti ratio changes. The observation of dynamic (1)H NMR spectroscopic scrambling between syn and anti conformations from the titration of chloride ion into the solution of the TMBPDM complex suggests that axial ligand exchange is a likely pathway for the conversion between syn and anti forms. Theoretical calculations revealed that intermolecular hydrogen-bonding interactions between the axial chloride and CHCl(3) stabilizes the anti conformation, which explains the increased ratio for the anti form when dichloromethane or chloroform was used as the solvent.

New Phenylpropanoid Glycosides from Eurya emarginata (Thunb.) Makino

Eurya emarginata (Thunb.) Makino belonging to Theaceae is an evergreen branched shrub with coriaceous and emarginated leaves. These trees are distributed along the coastal regions in the southern parts of Korea including Jeju Island. The genus Eurya contains more than 100 species worldwide, but only two species have been described in Korea. The leaves of E. emarginata and E. japonica have been used in Korean traditional medicine to treat arthritis. Previous biological studies of the extract of E. emarginata reported the anti-cancer, anti-inflammation and radiation protection activities, and identified phenolic glycosides as the active constituents. As part of an ongoing study aimed at identifying bioactive compounds from plants in Jeju Island, this study conducted phytochemical investigations on this plant. From the ethanol extract of the leaves and twigs of E. emarginata, new phenylpropanoid glycosides, eutigosides D (1) and E (2), were isolated along with five known compounds, eutigoside B (3), eutigoside C (4), cinnamic acid (5), rengyolone (6) and cleroindicin B (7) (Fig. 1). We herein report the structure elucidation and antioxidative activities of isolates 1-7. Compound 1 was obtained as viscous liquid with molecular ion peak at m/z 446.1577 in HR-FAB-MS, indicating a molecular formula of C23H26O9 (11 unsaturations). The C NMR spectrum revealed only 20 carbon peaks suggesting the presence of a symmetric moiety, which was readily identified as a phenyl group based on the characteristic aromatic H and C NMR signals appearing in narrow δ ranges (Tables 1 and 2). The trans-olefinic structure was also clearly characterized by the large coupling constant (J = 16.0 Hz) of the sp peaks at δ 7.76 (H-7’’) and 6.52 (H-8’’) ppm. This olefin was determined to be connected to both the phenyl and a carbonyl (C-9’’) groups by an inspection of the heteronuclear multiple bond correlation (HMBC) spectrum, which established a cinnamoyl substructure. The other aromatic protons were characterized to have the ABX spin system in the H NMR spectrum (Table 1). For example, the signal for H-5 showed a coupling constant of J = 8.5 Hz, which confirmed the ortho coupling to H-6. The signal for H-6 showed ortho and meta coupling to H-2 with J = 2.8 Hz. The remaining substructure –OCH2CH2was confirmed by its H, C and COSY NMR data. The HMBC cross signal of H-8/C-1 indicated the linkage of this ethylene unit to C-1 of the aromatic ring (Fig. 2). The presence of a sugar moiety in compound 1 is also clearly recognized by the H and C NMR spectra. As protons of the sugar exhibited relatively large coupling constants due to their axial H/H interactions, this hexose was assumed to be glucose. This was confirmed by the hydrolysis of the compound 1 with aq. HCl followed by the comparative TLC analysis of the aqueous phase to the authentic D-glucose. As the anomeric This paper is dedicated to Professor Eun Lee on the occasion of his honourable retirement. Figure 1. Structures of compounds 1-7 isolated from E. emarginata.

Exceptionally strong magnetism in the 4dperovskitesRTcO3(R=Ca, Sr, Ba)

The evolution of the magnetic ordering temperature of the 4d3 perovskites RTcO3 (R=Ca,Sr,Ba) and its relation with its electronic and structural properties has been studied by means of hybrid density functional theory and Monte Carlo simulations. When compared to the most widely studied 3d perovskites the large spatial extent of the 4d shells and their relatively strong hybridization with oxygen weaken the tendency to form Jahn-Teller like orbital ordering. This strengthens the superexchange interaction. The resulting insulating G-type antiferromagnetic ground state is characterized by large superexchange coupling constants (26-35 meV) and Neel temperatures (750-1200 K). These monotonically increase as a function of the R ionic radius due to the progressive enhancement of the volume and the associated decrease of the cooperative rotation of the TcO6 octahedra.

Electrical and optical properties of polyfluorene thin films studied by THz time-domain spectroscopy

We report on the electrical and optical characteristics of the conjugated polymer poly[9,9-bis-(2-ethylhexyl)-9H-fluorene-2,7-diyl] (PFO) studied by THz time-domain spectroscopy. A differential spectroscopy method was employed to measure the THz response of 1 µm thick PFO films. The THz spectra of optical and electrical characteristics of the PFO films can be described reasonably well by the Lorentz oscillator model with one effective oscillator. The large coupling constant of the effective oscillator testifies the strong intra-chain localization of charged carriers in the PFO polymer.

Survival probability of large rapidity gaps in the QCD and N=4 SYM motivated model

In this paper we present a self-consistent theoretical approach for the calculation of the Survival Probability for central dijet production. These calculations are performed in a model of high energy soft interactions based on two ingredients: (i) compatibility with the results of N=4 SYM, which at the moment is the only theory that is able to deal with a large coupling constant; and (ii) the required matching with high energy QCD. Assuming, in accordance with these prerequisites, that the soft Pomeron intercept is rather large and the slope of the Pomeron trajectory is equal to zero, we derive analytical formulae that sum both enhanced and semi-enhanced diagrams for elastic and diffractive amplitudes. Using parameters obtained from a fit to the available experimental data, we calculate the Survival Probability for exclusive central dijet production at energies accessible at the LHC. The results presented here, which include the contribution of semi-enhanced and net diagrams, are considerably larger than our previous estimates.

17 O NQR and 13 C NMR study of hydrogen-bonded organic ferroelectric croconic acid

The 1H17O nuclear quadrupole double resonance spectrum and the 13C CP/MAS NMR spectrum of polycrystalline croconic acid, H2C5O5, have been studied at room temperature. Croconic acid has been recently shown to have the highest switchable spontaneous polarization of all organic ferroelectrics and stays polarized up to the decomposition point at around 450 K. Both the 13C NMR and the 17O nuclear quadrupole resonance (NQR) spectra show that there are five crystallorgaphically non-equivalent carbon and oxygen positions for a given molecule and that therefore the two OH…O bonds are non-equivalent. From the dipolar structure of the 17O quadrupole resonance spectra the OH distance is determined as being 0.099 ± 0.001 nm in both hydrogen bonds. The large 17O quadrupole coupling constant at the COH as well as at the CO…H oxygen position and the short OH distance demonstrate that the OH…O hydrogen bonds are strongly asymmetric. A correlation of the 17OH…O and OH…17O quadrupole coupling constants versus the O…O distance has been observed in several organic acids. The data for croconic acid significantly deviate from this correlation, what may be the result of the strong long range ferroelectric ordering which influences the electron distribution in the hydrogen bonds.

NMR Chemical Shift and Quadrupolar Interaction Parameters of Carbon‐Coordinated 27Al in Aluminium Carbide, Al4C3

AbstractAluminium carbide, Al4C3, was characterised by 13C and 27Al solid‐state NMR spectroscopy. The 13C NMR spectra display two resonances with an intensity ratio of 1:2, which is in agreement with the reported crystal structure. The 27Al NMR spectra of Al4C3 under both static and MAS conditions were deconvoluted into two spectral components, belonging to the two aluminium species Al1 and Al2 in the crystal structure of Al4C3. The spectral fit allowed for determination of the relatively large quadrupolar coupling constants (χ ≈︁ 16 MHz) of both 27Al species. One aluminium species displayed a tendency of having a χ of slightly smaller magnitude compared to the other. By carrying out DFT calculations of the EFG tensor at the 27Al sites using the Wien2k software, we could tentatively assign the smaller χ site to be the crystallographic Al1 species. Also, the isotropic chemical shift for the carbon‐coordinated aluminium in Al4C3 could be determined, being in the range of 111 to 120 ppm. This is somewhat larger than those shift values observed for 27Al in nitrogen coordination.

N=4 SYM and QCD motivated approach to soft interactions at high energies

In this paper we construct a model that satisfies the theoretical requisites of high energy soft interactions, based on two ingredients:(i) the results of N=4 SYM, which at present is a unique theory that allows one to deal with a large coupling constant; and (ii) the requirement of matching with high energy QCD. In accordance with these ideas, we assume that the soft Pomeron intercept is rather large, and the slope of the Pomeron trajectory is equal to zero. We derive analytical formulae that sum both enhanced and semi-enhanced diagrams for elastic and diffractive amplitudes. We fit the available experimental data, and predict the valuefor cross sections at the energies accessible at the LHC. The main corrections to the model are studied and evaluated.