On the Definition of Gauge Field Operators in Lattice Gauge-Fixed Theories

We address the problem of defining the gauge four-potential on the lattice, in terms of the natural link variables. Different regularized definitions are shown, through non perturbative numerical computation, to converge towards the same continuum renormalized limit.Comment: 8 pages, LaTeX2e/LaTeX209, 3 eps figure

Impact of transforming to conformal Fermi coordinates on quasisingle field non-Gaussianity

In general relativity predictions for observable quantities can be expressed in a coordinate independent way. Nonetheless it may be inconvenient to do so. Using a particular frame may be the easiest way to connect theoretical predictions to measurable quantities. For the cosmological curvature bispectrum such frame is described by the Conformal Fermi Coordinates. In single field inflation it was shown that going to this frame cancels the squeezed limit of the density perturbation bispectrum calculated in Global Coordinates. We explore this issue in quasi single field inflation when the curvaton mass and the curvaton-inflaton mixing are small. In this case, the contribution to the bispectrum from the coordinate transformation to Conformal Fermi Coordinates is of the same order as that from the inflaton-curvaton interaction term but does not cancel it

Carcinogenicity of a Single Administration of N-Nitrosomethylurea: a Comparison Between New-born and 5-Week-Old Mice and Rats

N-Nitrosomethylurea (NMUrea) was given as a single intraperitoneal injection either to newborn or to 5-week-old (C57BL * C3Hf)F1 mice and Wistar rats. Newborn mice were more susceptible than 5-week-old mice to the development of lymphosarcomas, lung adenomas and hepatomas, whereas newborn rats were more susceptible than their weaned counterparts to the development of renal anaplastic tumours. Other tumours occured with the same frequency in newborn and mature animals. Tumours of the forestomach in mice were more frequenty found in animals treated at 5 weeks than in those treated at birth. Since NMUrea persists for only a very short time and breaks down spontaneously it seems that the paucity of enzymes related to immaturity in newborns is not a major factor in determining the different susceptibility of newborn animals to NMUrea carcinogenicity

Impact of transforming to Conformal Fermi Coordinates on Quasi-Single Field Non-Gaussianity

In general relativity predictions for observable quantities can be expressed in a coordinate independent way. Nonetheless it may be inconvenient to do so. Using a particular frame may be the easiest way to connect theoretical predictions to measurable quantities. For the cosmological curvature bispectrum such frame is described by the Conformal Fermi Coordinates. In single field inflation it was shown that going to this frame cancels the squeezed limit of the density perturbation bispectrum calculated in Global Coordinates. We explore this issue in quasi single field inflation when the curvaton mass and the curvaton-inflaton mixing are small. In this case, the contribution to the bispectrum from the coordinate transformation to Conformal Fermi Coordinates is of the same order as that from the inflaton-curvaton interaction term but does not cancel it.Comment: 13 pages, 2 figure

Conformational constraints on side chains in protein residues increase their information content

Like all other complex biological systems, proteins exhibit properties not seen in free amino acids (i.e., emergent properties). The present investigation arose from the deduction that proteins should offer a good model to approach the reverse phenomenon, namely top-down constraints experienced by protein residues compared to free amino acids. The crystalline structure of profilin Ib, a contractile protein of Acanthamoeba castellanii, was chosen as the object of study and submitted to 2-ns molecular dynamics simulation. The results revealed strong conformational constraints on the side chain of residues compared to the respective free amino acids. A Shannon entropy (SE) analysis of the conformational behavior of the side chains showed in most cases a strong decrease in the SE of the χ1 and χ2 dihedral angles compared to free amino acids. This is equivalent to stating that conformational constraints on the side chain of residues increase their information content and hence recognition specificity compared to free amino acids. In other words, the vastly increased information content of a protein relative to its free monomers is embedded not only in the tertiary structure of the backbone, but also in the conformational behavior of the side chains. The postulated implication is that both backbone and side chains, by virtue of being conformationally constrained, contribute to the recognition specificity of the protein toward other macromolecules and ligand

Magnetic structure of Ba(TiO)Cu4_4(PO4_4)4_4 probed using spherical neutron polarimetry

The antiferromagnetic compound Ba(TiO)Cu$_4$(PO$_4$)$_4$ contains square cupola of corner-sharing CuO$_4$ plaquettes, which were proposed to form effective quadrupolar order. To identify the magnetic structure, we have performed spherical neutron polarimetry measurements. Based on symmetry analysis and careful measurements we conclude that the orientation of the Cu$^{2+}$ spins form a non-collinear in-out structure with spins approximately perpendicular to the CuO$_4$ motif. Strong Dzyaloshinskii-Moriya interaction naturally lends itself to explain this phenomenon. The identification of the ground state magnetic structure should serve well for future theoretical and experimental studies into this and closely related compounds.Comment: 9 pages, 4 figure

Activation of benzoate model prodrugs by mycobacteria. Comparison with mammalian plasma and liver hydrolysis.

Due to difficulties in drug penetration in M. tuberculosis, a prodrug approach based on mycobacterial activation appears as a promising strategy to increase the delivery of antitubercular drugs to the target microorganisms. Esters have been successful used by us and others to deliver drugs to mycobacteria, however because very little is known about the metabolic hydrolysis of esters by mycobacteria in connection with prodrug activation, we decided to study the process further. For that we selected a series of 13 benzoates with different chain lengths and ramifications in the alkoxy side as model prodrugs and examined their hydrolysis by a mycobacterial homogenate, comparing the results with those obtained parallelly in human plasma and in total rat liver homogenate. In all biological media, the benzoates with a linear alkyl group showed a parabolic dependence between log(k) and logP (or the number of carbons of the linear alkyl chain) that reached a maximal value for the n-butyl chain. Considering linear correlations for the total number of compounds between log(k) and chosen descriptors, for mycobacterial esterases, pKa of the leaving alcohol (pKa <sub>LG</sub> ) seem to be the most important descriptor. Plasma esterases seem to be quite sensitive to the Taft polarity parameter σ* and also to pKa <sub>LG</sub> and less sensitive to steric effects. Liver esterases seem to be more sensitive to the Taft steric descriptor E <sub>S</sub> <sup>c</sup> . Lipophilicity correlates weakly with log(k) in all the 3 media, however, is more important when one looks for mycobacterial activation selectivity in relation to plasma metabolism or in relation to liver homogenate metabolism. The importance of lipophilicity increases further when biparametric expressions are considered. We showed that it is easy to activate a wide variety of benzoate esters using a mycobacterial homogenate. The data also suggest that with careful design is possible to obtain tuberculostatic prodrug esters sensitive to mycobacterial hydrolases while reasonably resistant to plasma and liver hydrolysis. One important observation is that mycobacterial hydrolysis is less affected by bulky substituents than liver homogenate or plasma hydrolysis. tert-Butyl is probably the substituent in the alkoxy side that seems more adequate to resist simultaneously plasma and liver metabolism, while allowing activation by mycobacterial esterases. Hexyl is also a good option for the medicinal chemist if a linear alkoxy chain is needed