Fractal Propagators in QED and QCD and Implications for the Problem of Confinement

We show that QED radiative corrections change the propagator of a charged Dirac particle so that it acquires a fractional anomalous exponent connected with the fine structure constant. The result is a nonlocal object which represents a particle with a roughened trajectory whose fractal dimension can be calculated. This represents a significant shift from the traditional Wigner notions of asymptotic states with sharp well-defined masses. Non-abelian long-range fields are more difficult to handle, but we are able to calculate the effects due to Newtonian gravitational corrections. We suggest a new approach to confinement in QCD based on a particle trajectory acquiring a fractal dimension which goes to zero in the infrared as a consequence of self-interaction, representing a particle which, in the infrared limit, cannot propagate.Comment: To appear in Brazilian Journal of Physics, special edition for the proceedings of IRQCD, Rio de Janeiro, 5-9 June 200

Isolation of ESBL-producing gram-negative bacteria and in silico inhibition of ESBLs by flavonoids

AbstractObjectiveTo evaluate nosocomial accounts of 426 extended spectrum β-lactamase (ESBL)-producing strains from 705 isolates of 9 pathogenic gram-negative bacteria in vitro. We analysed the genetic divergence of ESBLs by constructing a phylogenetic tree and modelled flavonoid inhibition of ESBLs with in silico molecular docking to determine effective control options.MethodsNine ESBL-producing bacteria were isolated from urine samples and their antibiograms were determined by the disc-diffusion method. Comparative models of the 9 ESBL enzymes were generated computationally using reference sequences, and validated by Ramachandran plots. Molecular docking with 11 flavonoids was conducted against the ESBL models.ResultsIsolated strains were floridly multidrug-resistant. From the docking study, the predicted minimum energy value of amikacin was −8.108 kcal/mol against the wild type TEM-1 ESBL of Acinetobacter baumannii, while the docking value against the mutant type Escherichia coli was −7.388 kcal/mol. The docking scores obtained corroborated the in vitro results showing that the antibiotic was incapable of controlling the ESBL of the mutant strain. Among 11 flavonoids tested against the mutant ESBL of E. coli, epigallocatechin 3-gallate and eriodictyol, with docking scores of −9.448 and −8.161 kcal/mol, respectively, were the most effective, with drug-likeness scores of 0.39 and 1.37, respectively, compared to 1.03 for amikacin.ConclusionDocking scores and drug-likeness scores indicated that flavonoids are compelling alternative antimicrobial agents that could serve as complementary therapy for newly arising ESBL-producing bacteria. Phylogenetic tree analysis elucidated the genetic relationship of the 9 ESBL serotypes

Transport and magnetic properties in YBaCo2O5.45: Focus on the high-temperature transition

The electronic transport properties and the magnetic susceptibility were measured in detail in $YBaCo_2O_{5.45}$. Close to the so-called metal-insulator transition, strong effects of resistance relaxation, a clear thermal hysteresis and a sudden increase of the resistance noise are observed. This is likely due to the first order character of the transition and to the underlying phases coexistence. Despite these out of equilibrium features, a positive and linear magneto-resistance is also observed, possibly linked to the heterogeneity of the state. From a magnetic point of view, the paramagnetic to ordered magnetic state transition is observed using non linear susceptibilty. This transition shows the characteristics of a continuous transition, and time dependent effects can be linked with the dynamics of magnetic domains in presence of disorder. Thus, when focusing on the order of the transitions, the electronic one and the magnetic one can not be directly associated.Comment: accepted for publication in PR

In vitro antibacterial efficacy of plants used by an Indian aboriginal tribe against pathogenic bacteria isolated from clinical samples

AbstractObjectivesTo evaluate antibacterial efficacies of 21 medicinal plants used by an Indian aboriginal tribe against infectious diseases caused by bacteria isolated from clinical samples.MethodsStandard biochemical procedures were followed for identifying bacteria that were isolated from several clinical samples. All of the bacterial strains were subjected to antibiotic sensitivity tests by Kirby–Bauer's disc diffusion method. From antibiograms of isolated Gram-positive and Gram-negative bacteria, it was discernible that samples were multidrug resistant (MDR). The methanol leaf-extract of Solanum xanthocarpum was subjected to thin layer chromatography (TLC) for phytochemical analysis. Molecular docking of β-lactamase enzyme of Escherichia coli with phytochemicals of S. xanthocarpum was performed to locate effective compounds.ResultsThe most effective 5 plants, which caused the size of the zone of inhibition to range from 21 to 27 mm, were Buchanania latifolia, Careya arborea, Ocimum tenuiflorum, Senna alata and S. xanthocarpum, for MDR bacteria. S. xanthocarpum had the lowest MIC value of 0.67 mg/ml and the lowest MBC value of 1.51 mg/ml against E. coli. In the TLC study, 9 spots of methanol leaf-extract of S. xanthocarpum were recorded with two solvent systems. The phytochemicals of S. xanthocarpum, solasodine and stigmasterol glucoside had the highest docking score values, −10.868 kcal/mol and −10.439 kcal/mol, respectively, against β-lactamase.ConclusionThis study could prove in vitro antimicrobial efficacy of 5 uncommon plants against MDR pathogenic bacteria. Solasodine and stigmasterol glucoside were computationally recorded as the best controlling chemicals from the plant S. xanthocarpum

A new look at NICMOS transmission spectroscopy of HD189733, GJ-436 and XO-1: no conclusive evidence for molecular features

We present a re-analysis of archival HST/NICMOS transmission spectroscopy of three exoplanet systems; HD 189733, GJ-436 and XO-1. Detections of several molecules, including H20, CH4 and CO2, have been claimed for HD 189733 and XO-1, but similarly sized features are attributed to systematic noise for GJ-436. The data consist of time-series grism spectra covering a planetary transit. After extracting light curves in independent wavelength channels, we use a linear decorrelation technique account for instrumental systematics (which is becoming standard in the field), and measure the planet-to-star radius ratio as a function of wavelength. For HD 189733, the uncertainties in the transmission spectrum are significantly larger than those previously reported. We also find the transmission spectrum is considerably altered when using different out-of-transit orbits to remove the systematics, when some parameters are left out of the decorrelation procedure, or when we perform the decorrelation with quadratic functions rather than linear functions. Given that there is no physical reason to believe the baseline flux should be modelled as a linear function of any particular set of parameters, we interpret this as evidence that the linear decorrelation technique is not a robust method to remove systematic effects from the light curves for each wavelength channel. For XO-1, the parameters measured to decorrelate the light curves would require extrapolation to the in-transit orbit to remove the systematics, and we cannot reproduce the previously reported results. We conclude that the resulting NICMOS transmission spectra are too dependent on the method used to remove systematics to be considered robust detections of molecular species in planetary atmospheres, although the presence of these molecules is not ruled out.Comment: 17 pages, 28 figures, accepted in MNRA