Anharmonic transitions in nearly dry L-cysteine I

Two special dynamical transitions of universal character have been recently observed in macromolecules at $T_{D}\sim 180 - 220$ K and $T^{*}\sim 100$ K. Despite their relevance, a complete understanding of the nature of these transitions and their consequences for the bio-activity of the macromolecule is still lacking. Our results and analysis concerning the temperature dependence of structural, vibrational and thermodynamical properties of the orthorhombic polymorph of the amino acid L-cysteine (at a hydration level of 3.5%) indicated that the two referred temperatures define the triggering of very simple and specific events that govern all the biochemical interactions of the biomolecule: activation of rigid rotors ($T<T^{*}$), phonon-phonon interactions with phonons of water dimer ($T^{*}<T<T_{D}$), and water rotational barriers surpassing ($T>T_{D}$).Comment: 4 pages, 4 figures, submitted to Physical Review Letter

Agressividade de isolados de curtobacterium flaccumfaciens pv. flaccumfaciens em feijoeiro comum.

Para o estudo da patogenicidade dos isolados de C. flaccumfaciens pv. flaccumfaciens em genótipos de feijoeiro comum torna-se necessário o desenvolvimento mais pesquisas, por ser um estudo direcionado ao programa de melhoramento genético do feijão para seleção de cultivares com resistência genética à presente doença.CONAFE

Effectiveness of Chitosan Films Impregnated With Ciprofloxacin for the Prophylaxis of Osteomyelitis in Open Fractures: An Experimental Study in Rats

Background: The systemic antimicrobial prophylaxis is the standard treatment in the prevention of osteomyelitis after open fractures, with topical application of antimicrobials as an alternative due to their high concentrations at the site of the fracture, low systemic concentrations and fewer side effects. Objectives: This study aimed to evaluate the effectiveness of prophylaxis of osteomyelitis through experimental model of open fractures with the use of chitosan films, whether or not impregnated with ciprofloxacin. Materials and Methods: In this experimental study, 24 Holtzman rats were distributed into 4 groups of 6 rats each. The CT (control of treatment) group: an open fracture model treated with systemic antimicrobial; the IC (infection control) group: an open fracture untreated model; the C (chitosan) group: an open fracture model treated using a chitosan film; and the CA (chitosan with antimicrobial) group: an open fracture model treated using a chitosan film impregnated with antimicrobial. After 3 weeks the animals were killed by an overdose of anesthetic, and a fragment osseous was removed for histological and microbiological analysis. The comparisons between the groups considered significant values of P ≤ 0.05. Results: In cultures of the CT group, there was less bacterial growth compared to the results of the cultures of the IC (P = 0.005), C (P = 0.005) and CA (P = 0.009) groups. The inflammation was lower in the CT group compared to the IC (P = 0.014), C (P = 0.001) and CA (P = 0.007) groups. Conclusions: In this experimental model of open fracture, the chitosan film pure or impregnated with ciprofloxacin was not effective in the prophylaxis of osteomyelitis

On the role of composition entropies in the statistical mechanics of polydisperse systems

Polydisperse systems are commonly encountered when dealing with soft matter in general or any non-simple fluid. Yet their treatment within the framework of statistical thermodynamics is a delicate task as the latter has been essentially devised for simple—non-fully polydisperse—systems. In this paper, we address the issue of defining a non-ambiguous combinatorial entropy for these systems. We do so by focusing on the general property of extensivity of the thermodynamic potentials and discussing a specific mixing experiment. This leads us to introduce the new concept of composition entropy for single phase systems that we do not assimilate to a mixing entropy. We then show that they do not contribute to the thermodynamics of the system at a fixed composition and prescribe to subtract ln N! from the free energy characterizing a system however polydisperse it can be. We then re-derive general expressions for the mixing entropy between any two polydisperse systems and interpret them in term of distances between probability distributions, showing that one of these metrics relates naturally to a recent extension of Landauer's principle. We then propose limiting expressions for the mixing entropy in the case of mixing with equal proportions in the original compositions and finally address the challenging problem of chemical reactions

General Scalar Fields as Quintessence

We study the cosmological evolution of scalar fields with arbitrary potentials in the presence of a barotropic fluid (matter or radiation) without making any assumption on which term dominates. We determine what kind of potentials V(phi) permits a quintessence interpretation of the scalar field phi and to obtain interesting cosmological results. We show that all model dependence is given in terms of lambda= - V'/V only and we study all possible asymptotic limits: lambda approaching zero, a finite constant or infinity. We determine the equation of state dynamically for each case. For the first class of potentials, the scalar field quickly dominates the universe behaviour, with an inflationary equation of state allowing for a quintessence interpretation. The second case gives the extensively studied exponential potential. While in the last case, when lambda approaches infinity, if it does not oscillate then the energy density redshifts faster than the barotropic fluid but if lambda oscillates then the energy density redshift depends on the specific potential.Comment: 14 pages, LaTeX, 4 postscript figure