Superconductivity in the two-dimensional Hubbard model?

A refined variational wave function for the two-dimensional repulsive Hubbard model is studied numerically, with the aim of approaching the difficult crossover regime of intermediate values of U. The issue of a superconducting ground state with d-wave symmetry is investigated for an average electron density n=0.8125 and for U=8t. Due to finite-size effects a clear-cut answer to this fundamental question has not yet been reached.Comment: 5 pages, 1 figure, Proc. 30th Int. Conf. of Theoretical Physics, Ustron, Poland, 2006, to be published in phys. stat. so

Novel cinnamic acid/4-aminoquinoline conjugates bearing non-proteinogenic amino acids: Towards the development of potential dual action antimalarials

A series of cinnamic acid/4-aminoquinoline conjugates conceived to link, through a proper retro-enantio dipeptide, a heterocyclic core known to prevent hemozoin formation, to a trans-cinnamic acid motif capable of inhibiting enzyme catalytic Cys residues, were synthesized as potential dual-action antimalarials. The effect of amino acid configuration and the absence of the dipeptide spacer were also assessed. The replacement of the D-amino acids by their natural L counterparts led to a decrease in both anti-plasmodial and falcipain inhibitory activity, suggesting that the former are preferable. Molecules with such spacer were active against blood-stage Plasmodium falciparum, in vitro, and hemozoin formation, implying that the dipeptide has a key role in mediating these two activities. In turn, compounds without spacer were better falcipain-2 inhibitors, likely because these compounds are smaller and have their vinyl bonds in closer vicinity to the catalytic Cys, as suggested by molecular modeling calculations. These novel conjugates constitute promising leads for the development of new antiplasmodials targeted at blood-stage malaria parasites

A preferential attachment model with random initial degrees

In this paper, a random graph process ${G(t)}_{t\geq 1}$ is studied and its degree sequence is analyzed. Let $(W_t)_{t\geq 1}$ be an i.i.d. sequence. The graph process is defined so that, at each integer time $t$, a new vertex, with $W_t$ edges attached to it, is added to the graph. The new edges added at time t are then preferentially connected to older vertices, i.e., conditionally on $G(t-1)$, the probability that a given edge is connected to vertex i is proportional to $d_i(t-1)+\delta$, where $d_i(t-1)$ is the degree of vertex $i$ at time $t-1$, independently of the other edges. The main result is that the asymptotical degree sequence for this process is a power law with exponent $\tau=\min\{\tau_{W}, \tau_{P}\}$, where $\tau_{W}$ is the power-law exponent of the initial degrees $(W_t)_{t\geq 1}$ and $\tau_{P}$ the exponent predicted by pure preferential attachment. This result extends previous work by Cooper and Frieze, which is surveyed.Comment: In the published form of the paper, the proof of Proposition 2.1 is incomplete. This version contains the complete proo

Low-Impedance 3D PEDOT:PSS Ultramicroelectrodes

The technology for producing microelectrode arrays (MEAs) has been developing since the 1970s and extracellular electrophysiological recordings have become well established in neuroscience, drug screening and cardiology. MEAs allow monitoring of long-term spiking activity of large ensembles of excitable cells noninvasively with high temporal resolution and mapping its spatial features. However, their inability to register subthreshold potentials, such as intrinsic membrane oscillations and synaptic potentials, has inspired a number of laboratories to search for alternatives to bypass the restrictions and/or increase the sensitivity of microelectrodes. In this study, we present the fabrication and in vitro experimental validation of arrays of PEDOT:PSS-coated 3D ultramicroelectrodes, with the best-reported combination of small size and low electrochemical impedance. We observed that this type of microelectrode does not alter neuronal network biological properties, improves the signal quality of extracellular recordings and exhibits higher selectivity toward single unit recordings. With fabrication processes simpler than those reported in the literature for similar electrodes, our technology is a promising tool for study of neuronal networks. \ua9 Copyright \ua9 2020 Jones, Moskalyuk, Barthold, Gut\uf6hrlein, Heusel, Schr\uf6ppel, Samba and Giugliano

Evaluation of C-reactive protein and its kinetics as a prognostic indicator in canine leptospirosis.

OBJECTIVE To evaluate C-reactive protein at presentation and during hospitalisation in dogs with acute kidney injury resulting from leptospirosis to compare C-reactive protein at presentation in dogs with acute kidney injury of different aetiology and to study its correlation with markers of inflammation, azotaemia and survival. MATERIALS AND METHODS Prospective observational study of 41 dogs with acute kidney injury secondary to leptospirosis and 15 control dogs with acute kidney injury of different aetiology. C-reactive protein was measured at presentation in both groups and daily for 7 days in a subgroup of 28 dogs with leptospirosis. The associations of C-reactive protein with neutrophil count, albumin, urea, creatinine and survival were analysed. RESULTS C-reactive protein was increased at presentation in all dogs with leptospirosis but was not significantly different from dogs with acute kidney injury of different cause. It was associated with markers of inflammation (neutrophil count, albumin) but not with azotaemia (creatinine, urea). It decreased gradually from presentation to day 4, with significantly lower concentrations in survivors than non-survivors. Initial C-reactive protein was only weakly associated with outcome, but its average concentration from presentation to day 2 was more strongly associated. Absolute and relative changes in C-reactive protein during hospitalisation and creatinine at presentation were not associated with survival. CLINICAL SIGNIFICANCE Serial assessment of C-reactive protein may improve outcome prediction in dogs with leptospirosis compared with a single measurement at presentation or with markers of renal function

Genetic analysis of an F2 intercross between two chicken lines divergently selected for body-weight

<p>Abstract</p> <p>Background</p> <p>We have performed Quantitative Trait Loci (QTL) analysis of an F₂intercross between two chicken lines divergently selected for juvenile body-weight. In a previous study 13 identified loci with effects on body-weight, only explained a small proportion of the large variation in the F₂population. Epistatic interaction analysis however, indicated that a network of interacting loci with large effect contributed to the difference in body-weight of the parental lines. This previous analysis was, however, based on a sparse microsatellite linkage map and the limited coverage could have affected the main conclusions. Here we present a revised QTL analysis based on a high-density linkage map that provided a more complete coverage of the chicken genome. Furthermore, we utilized genotype data from ~13,000 SNPs to search the genome for potential selective sweeps that have occurred in the selected lines.</p> <p>Results</p> <p>We constructed a linkage map comprising 434 genetic markers, covering 31 chromosomes but leaving seven microchromosomes uncovered. The analysis showed that seven regions harbor QTL that influence growth. The pair-wise interaction analysis identified 15 unique QTL pairs and notable is that nine of those involved interactions with a locus on chromosome 7, forming a network of interacting loci. The analysis of ~13,000 SNPs showed that a substantial proportion of the genetic variation present in the founder population has been lost in either of the two selected lines since ~60% of the SNPs polymorphic among lines showed fixation in one of the lines. With the current marker coverage and QTL map resolution we did not observe clear signs of selective sweeps within QTL intervals.</p> <p>Conclusion</p> <p>The results from the QTL analysis using the new improved linkage map are to a large extent in concordance with our previous analysis of this pedigree. The difference in body-weight between the parental chicken lines is caused by many QTL each with a small individual effect. Although the increased chromosomal marker coverage did not lead to the identification of additional QTL, we were able to refine the localization of QTL. The importance of epistatic interaction as a mechanism contributing significantly to the remarkable selection response was further strengthened because additional pairs of interacting loci were detected with the improved map.</p

Searching for planar signatures in WMAP

We search for planar deviations of statistical isotropy in the Wilkinson Microwave Anisotropy Probe (WMAP) data by applying a recently introduced angular-planar statistics both to full-sky and to masked temperature maps, including in our analysis the effect of the residual foreground contamination and systematics in the foreground removing process as sources of error. We confirm earlier findings that full-sky maps exhibit anomalies at the planar ($l$) and angular ($\ell$) scales $(l,\ell)=(2,5),(4,7),$ and $(6,8)$, which seem to be due to unremoved foregrounds since this features are present in the full-sky map but not in the masked maps. On the other hand, our test detects slightly anomalous results at the scales $(l,\ell)=(10,8)$ and $(2,9)$ in the masked maps but not in the full-sky one, indicating that the foreground cleaning procedure (used to generate the full-sky map) could not only be creating false anomalies but also hiding existing ones. We also find a significant trace of an anomaly in the full-sky map at the scale $(l,\ell)=(10,5)$, which is still present when we consider galactic cuts of 18.3% and 28.4%. As regards the quadrupole ($\ell=2$), we find a coherent over-modulation over the whole celestial sphere, for all full-sky and cut-sky maps. Overall, our results seem to indicate that current CMB maps derived from WMAP data do not show significant signs of anisotropies, as measured by our angular-planar estimator. However, we have detected a curious coherence of planar modulations at angular scales of the order of the galaxy's plane, which may be an indication of residual contaminations in the full- and cut-sky maps.Comment: 15 pages with pdf figure