Quantum Symmetry of Hubbard Model Unraveled

Superconducting quantum symmetries in extended single-band 1-dimensional Hubbard models are shown to originate from the classical (pseudo-)spin SO(4) symmetry of a class of models of which the standard Hubbard model is a special case. Extending the notion of symmetry to include quantum groups allows us to introduce extra parameters but the corresponding quantum symmetric models are restricted to one dimension. All models discussed are related by generalized Lang-Firsov transformations, some have symmetries away from half filling. The most general model with symmetric next-neighbour interaction terms and classical SO(4) symmetry is given explicitly.Comment: 5 pages, revtex; 3 references added, hidden symmetries mentioned in introductio

C60-Propylamine Adduct Monolayers at the Gas/Water Interface: A Brewster Angle Microscopy and X-Ray Scattering Study

Brewster angle microscopy (BAM), x-ray specular reflectivity and grazing-incidence x-ray diffraction (GID) studies of C60-propylamine adduct monolayers at the gas/water interface as a function of molecular area are reported. At large molecular areas (A> ∼ 150 Å2/molecule), BAM images reveal macroscopic heterogeneity in the film, consisting of the coexistence between regions covered with uniform solidlike monolayer and bare water surface. After compression to a limiting molecular area of 150 Å2/molecule, the film is observed to be homogeneous, with the uniform monolayer covering the entire available surface. Both the x-ray reflectivity results and the GID patterns are consistent with the formation of a uniform monolayer at A ∼ 150 Å2/molecule, while the little dependence that the GID patterns have on the molecular area for A> ∼ 150 Å2/molecule is consistent with the heterogeneity in the film. Upon further compression to higher densities (A< ∼ 120 Å2/molecule), the x-ray reflectivity results suggest the formation of a partial layer either at the molecule/gas interface or at the molecule/water interface. In this high density regime, the shift in the observed GID pattern with molecular area is much smaller than would be expected if the film were to remain a homogeneous monolayer, also consistent with the formation of an inhomogeneous partial layer. The analysis of the broad GID pattern observed from a uniform monolayer in terms of a model 2D radial distribution function, implies a short range positional correlation, extending to only a few molecular distances. The average nearest neighbor distance (d ∼ 13 Å), extracted from the GID analysis, is consistent with the limiting molecular area (A ∼ 150 Å2/molecule) assuming local hexagonal packing. These results together with the sharp facets observed in the BAM images demonstrate that the monolayer when uniform is a two-dimensional amorphous solid.Engineering and Applied Science

Monolayer/Bilayer Transition in Langmuir Films of Derivatized Gold Nanoparticles at the Gas/Water Interface: An X-Ray Scattering Study

The microscopic structure of Langmuir films of derivatized gold nanoparticles has been studied as a function of area/particle on the water surface. The molecules (AuSHDA) consist of gold particles of mean core diameter D ∼ 22 Å that have been stabilized by attachment of carboxylic acid terminated alkylthiols, HS–(CH2)15–COOH. Compression of the film results in a broad plateau of finite pressure in the surface pressure versus area/particle isotherm that is consistent with a first-order monolayer/bilayer transition. X-ray specular reflectivity (XR) and grazing incidence diffraction show that when first spread at large area/particle, AuSHDA particles aggregate two dimensionally to form hexagonally packed monolayer domains at a nearest-neighbor distance of a = 34 Å. The lateral positional correlations associated with the two-dimensional (2D) hexagonal order are of short range and extend over only a few interparticle distances; this appears to be a result of the polydispersity in particle size. Subsequent compression of the film increases the surface coverage by the monolayer but has little effect on the interparticle distance in the close-packed domains. The XR and off-specular diffuse scattering (XOSDS) results near the onset of the monolayer/bilayer coexistence plateau are consistent with complete surface coverage by a laterally homogeneous monolayer of AuSHDA particles. On the high-density side of the plateau, the electron-density profile extracted from XR clearly shows the formation of a bilayer in which the newly formed second layer on top is slightly less dense than the first layer. In contrast to the case of the homogeneous monolayer, the XOSDS intensities observed from the bilayer are higher than the prediction based on the capillary wave model and the assumption of homogeneity, indicating the presence of lateral density inhomogeneities in the bilayer. According to the results of Bragg rod measurements, the 2D hexagonal order in the two layers of the bilayer are only partially correlated.Engineering and Applied Science

Determination of 18β-Glycyrrhetinic Acid in Human Serum Using the Fully Automated ALCA-System

Peer Reviewe

High-Dose Hydrocortisone Treatment Does Not Affect Serum C-Reactive Protein (CRP) Concentrations in Healthy Dogs

Measuring C-reactive protein (CRP) in serum is a useful surrogate marker for assessing disease progression and treatment response in dogs with autoinflammatory diseases. Affected dogs often receive high-dose glucocorticoid treatment, but the effect of such treatment alone on serum CRP concentrations is unknown. We evaluated serum CRP concentrations via immunoassay (sandwich enzyme-linked immunosorbent assay and particle-enhanced turbidimetric immunoassay) in 12 healthy beagle dogs administered high-dose hydrocortisone (8 mg/kg q12 h) per os vs. placebo over 28 days (days 0, 1, 5, and 28) in a randomized parallel study design. Serum CRP concentrations slightly decreased during treatment or placebo but without a significant association with hydrocortisone administration (p = 0.761). Compared to baseline, serum CRP concentrations were decreased by >2.7-fold (minimum critical difference) in three hydrocortisone-treated dogs and two dogs in the placebo group on day 28, whereas an increase to >2.7-fold was seen in one dog receiving placebo. These results suggest a lack of confounding effects of high-dose hydrocortisone administration on serum CRP concentrations in healthy dogs. This might also hold in dogs with autoinflammatory conditions and/or administration of other high-dose corticosteroids, suggesting that CRP presents a suitable biomarker to monitor inflammatory disease processes. However, this needs confirmation by further studies evaluating corticosteroid-induced cellular (e.g., hepatic) transcriptome and proteome changes