Superconductivity in the Two-Dimensional tt-JJ Model at Low Hole Doping

By combining a generalized Lanczos scheme with the variational Monte Carlo method we can optimize the short- and long-range properties of the groundstate separately. This allows us to measure the long-range order of the groundstate of the $t$-$J$ model as a function of the coupling constant $J/t$, and identify a region of finite d-wave superconducting long-range order. With a lattice size of 50 sites we can reliably examine hole densities down to 0.16.Comment: 12 pages and 4 PostScript figures, ReVTeX 3.0, ETH-TH/94-1

Fingerprinting of chlorinated paraffins and their transformation products in plastic consumer products

Chlorinated paraffins (CPs) can be classified according to their length as short-chain (SC, C10-C13), medium-chain (MC, C14-C17) and long-chain (LC, C ≥ 18) CPs. Technical CP-mixtures can contain a wide range of carbon- (C-, nC = 10-30) and chlorine- (Cl-, nCl = 3-19) homologues. CPs are high-production volume chemicals (>106 t/y). They are used as flame-retardants, plasticizers and coolant fluids. Due to the persistence, bioaccumulation, long-range environmental transport potential and adverse effects, SCCPs are regulated as persistent organic pollutants (POPs) by the Stockholm Convention. Transformation of CPs can lead to the formation of unsaturated compounds such as chlorinated mono- (CO), di- (CdiO) and tri-olefins (CtriO). Such transformation reactions can occur at different stages of CP manipulation providing characteristic C-/Cl-homologue distributions. All this results in unique patterns that collectively create a fingerprint, which can be distinguished from CP-containing samples. Therefore, CP-fingerprinting can develop into a promising tool for future source apportionment studies and with it, the reduction of environmental burden of CPs and hazards to humans. Herein, CP-containing plastics were studied to establish fingerprints and develop this method. We analyzed four household items by reverse-phase liquid-chromatography coupled with a mass spectrometer with an atmospheric pressure chemical ionization source and an Orbitrap mass analyzer (RP-LC-APCI-Orbitrap-MS) operated at a resolution of 120000 (FWHM at m/z 200). MS-data of different CP-, CO-, CdiO- and CtriO-homologues were efficiently processed with an R-based automatic mass spectra evaluation routine (RASER). From the 16720 ions searched for, up to 4300 ions per sample were assigned to 340 C-/Cl-homologues of CPs and their transformation products. Specific fingerprints were deduced from the C-/Cl-homologues distributions, the carbon- (nC) and chlorine- (nCl) numbers and saturation degree. These fingerprints were compared with the ones obtained by a GC-ECNI-Orbitrap-MS method

Singlet Stripe Phases in the planar t-J Model

The energies of singlet stripe phases in which a plane is broken up into spin liquid ladders by lines of holes, is examined. If the holes were static then patterns containing spin liquids with a finite spin gap are favored. The case of dynamic holes is treated by assembling t-J ladders oriented perpendicular to the stripes. For a wide region around $J/t \approx 1$ the hole-hole correlations in a single ladder are found to be predominantly charge density wave type but an attraction between hole pairs on adjacent ladders leads to a stripe phase. A quantum mechanical melting of the hole lines at smaller $J/t$ values leads to a Bose condensate of hole pairs, i.e. a superconducting phase.Comment: 5 pages, uuencoded compressed PostScript file including 5 figures, ETH-TH/942

Phase Separation of the Two-Dimensional t-J model

The boundary of phase separation of the two-dimensional t-J model is investigated by the power-Lanczos method and Maxwell construction. The method is similar to a variational approach and it determines the lower bound of the phase separation boundary with $J_c/t=0.6\pm 0.1$ in the limit $n_e\sim 1$. In the physical interesting regime of high T_c superconductors where $0.3<J/t<0.5$ there is no phase separation.Comment: LaTex 5 pages, 4 figure

Numerical Study of Impurity Effects on Quasiparticles within S-wave and Chiral P-wave Vortices

The impurity problems within vortex cores of two-dimensional s-wave and chiral p-wave superconductors are studied numerically in the framework of the quasiclassical theory of superconductivity and self-consistent Born approximation under a trial form of the pair potential. The dispersion and impurity scattering rate (the inverse of the relaxation time) of the Andreev bound state localized in vortex cores are deduced from the angular-resoloved local density of states. The energy dependence of the impurity scattering rates depends on the pairing symmetry; particularly, in the chiral p-wave vortex core where chirality and vorticity have opposite sign and hence the total angular momentum is zero, the impurities are ineffective and the scattering rate is vanishingly small. Owing to the cancellation of angular momentum between chirality and vorticity, the chiral p-wave vortex core is similar to locally realized s-wave region and therefore non-magnetic impurity is harmless as a consequence of Anderson's theorem. The results of the present study confirm the previous results of analytical study (J. Phys. Soc. Jpn. {\bf 69} (2000) 3378) in the Born limit.Comment: 8pages, 9figures, submitted to J. Phys. Soc. Jp

Fingerprinting of chlorinated paraffins and their transformation products in plastic consumer products

Chlorinated paraffins (CPs) can be classified according to their length as short-chain (SC, C10-C13), medium-chain (MC, C14-C17) and long-chain (LC, C ≥ 18) CPs. Technical CP-mixtures can contain a wide range of carbon- (C-, nC = 10-30) and chlorine- (Cl-, nCl = 3-19) homologues. CPs are high-production volume chemicals (>106 t/y). They are used as flame-retardants, plasticizers and coolant fluids. Due to the persistence, bioaccumulation, long-range environmental transport potential and adverse effects, SCCPs are regulated as persistent organic pollutants (POPs) by the Stockholm Convention. Transformation of CPs can lead to the formation of unsaturated compounds such as chlorinated mono- (CO), di- (CdiO) and tri-olefins (CtriO). Such transformation reactions can occur at different stages of CP manipulation providing characteristic C-/Cl-homologue distributions. All this results in unique patterns that collectively create a fingerprint, which can be distinguished from CP-containing samples. Therefore, CP-fingerprinting can develop into a promising tool for future source apportionment studies and with it, the reduction of environmental burden of CPs and hazards to humans. Herein, CP-containing plastics were studied to establish fingerprints and develop this method. We analyzed four household items by reverse-phase liquid-chromatography coupled with a mass spectrometer with an atmospheric pressure chemical ionization source and an Orbitrap mass analyzer (RP-LC-APCI-Orbitrap-MS) operated at a resolution of 120000 (FWHM at m/z 200). MS-data of different CP-, CO-, CdiO- and CtriO-homologues were efficiently processed with an R-based automatic mass spectra evaluation routine (RASER). From the 16720 ions searched for, up to 4300 ions per sample were assigned to 340 C-/Cl-homologues of CPs and their transformation products. Specific fingerprints were deduced from the C-/Cl-homologues distributions, the carbon- (nC) and chlorine- (nCl) numbers and saturation degree. These fingerprints were compared with the ones obtained by a GC-ECNI-Orbitrap-MS method

Electronic Structure Calculation by First Principles for Strongly Correlated Electron Systems

Recent trends of ab initio studies and progress in methodologies for electronic structure calculations of strongly correlated electron systems are discussed. The interest for developing efficient methods is motivated by recent discoveries and characterizations of strongly correlated electron materials and by requirements for understanding mechanisms of intriguing phenomena beyond a single-particle picture. A three-stage scheme is developed as renormalized multi-scale solvers (RMS) utilizing the hierarchical electronic structure in the energy space. It provides us with an ab initio downfolding of the global band structure into low-energy effective models followed by low-energy solvers for the models. The RMS method is illustrated with examples of several materials. In particular, we overview cases such as dynamics of semiconductors, transition metals and its compounds including iron-based superconductors and perovskite oxides, as well as organic conductors of kappa-ET type.Comment: 44 pages including 38 figures, to appear in J. Phys. Soc. Jpn. as an invited review pape

Structural basis for native agonist and synthetic inhibitor recognition by the Pseudomonas aeruginosa quorum sensing regulator PqsR (MvfR)

Bacterial populations co-ordinate gene expression collectively through quorum sensing (QS), a cell-to-cell communication mechanism employing diffusible signal molecules. The LysR-type transcriptional regulator (LTTR) protein PqsR (MvfR) is a key component of alkyl-quinolone (AQ)-dependent QS in Pseudomonas aeruginosa. PqsR is activated by 2-alkyl-4-quinolones including the Pseudomonas quinolone signal (PQS; 2-heptyl-3-hydroxy-4(1H)-quinolone), its precursor 2-heptyl-4- hydroxyquinoline (HHQ) and their C9 congeners, 2-nonyl-3-hydroxy-4(1H)-quinolone (C9-PQS) and 2-nonyl-4-hydroxyquinoline (NHQ). These drive the autoinduction of AQ biosynthesis and the up-regulation of key virulence determinants as a function of bacterial population density. Consequently, PqsR constitutes a potential target for novel antibacterial agents which attenuate infection through the blockade of virulence. Here we present the crystal structures of the PqsR co-inducer binding domain (CBD) and a complex with the native agonist NHQ. We show that the structure of the PqsR CBD has an unusually large ligand-binding pocket in which a native AQ agonist is stabilized entirely by hydrophobic interactions. Through a ligand-based design strategy we synthesized and evaluated a series of 50 AQ and novel quinazolinone (QZN) analogues and measured the impact on AQ biosynthesis, virulence gene expression and biofilm development. The simple exchange of two isosteres (OH for NH2) switches a QZN agonist to an antagonist with a concomitant impact on the induction of bacterial virulence factor production. We also determined the complex crystal structure of a QZN antagonist bound to PqsR revealing a similar orientation in the ligand binding pocket to the native agonist NHQ. This structure represents the first description of an LTTR-antagonist complex. Overall these studies present novel insights into LTTR ligand binding and ligand-based drug design and provide a chemical scaffold for further anti-P. aeruginosa virulence drug development by targeting the AQ receptor PqsR

Maternal Antibody Transmission in Relation to Mother Fluctuating Asymmetry in a Long-Lived Colonial Seabird: The Yellow-Legged Gull Larus michahellis

Female birds transfer antibodies to their offspring via the egg yolk, thus possibly providing passive immunity against infectious diseases to which hatchlings may be exposed, thereby affecting their fitness. It is nonetheless unclear whether the amount of maternal antibodies transmitted into egg yolks varies with female quality and egg laying order. In this paper, we investigated the transfer of maternal antibodies against type A influenza viruses (anti-AIV antibodies) by a long-lived colonial seabird, the yellow-legged gull (Larus michahellis), in relation to fluctuating asymmetry in females, i.e. the random deviation from perfect symmetry in bilaterally symmetric morphological and anatomical traits. In particular, we tested whether females with greater asymmetry transmitted fewer antibodies to their eggs, and whether within-clutch variation in yolk antibodies varied according to the maternal level of fluctuating asymmetry. We found that asymmetric females were in worse physical condition, produced fewer antibodies, and transmitted lower amounts of antibodies to their eggs. We also found that, within a given clutch, yolk antibody level decreased with egg laying order, but this laying order effect was more pronounced in clutches laid by the more asymmetric females. Overall, our results support the hypothesis that maternal quality interacts with egg laying order in determining the amount of maternal antibodies transmitted to the yolks. They also highlight the usefulness of fluctuating asymmetry as a sensitive indicator of female quality and immunocompetence in birds