Reflexões E Teorias Sobre O Lazer - Um Roteiro Para A Geografia

Leisure activities became a human need and provide a myriad of meanings that can be read throughout space and time. As a social activity it consumes and develops in space and for individuals. In this article we intend to address the main similarities between tourism approaches, leisure and geography, by analyzing the theories, procedures and the nature of research. We portray the state of the art in top researches involving Leisure and Geography and searching for contributions in other areas. The theoretical framework is worked in the light of some of the most common geography concepts such as place, landscape and region, drawing opportunities of study for each concept. It articulates, through the most common theoretical-conceptual constructions in other areas, especially in the contributions of sociology, anthropology and economics. Part of the article is a series of proposals to encourage studies in different subfields of geography, including Economic Geography, Geography of Tourism and Cultural Geography. By drawing parallels between leisure and the different branches of Geographical knowledge, it culminates in a schematic proposal for studies of Geography and Leisure through the synthesis of categories and a theoretical framework proposal for each of them. It concludes with considerations about the potential and limitations of the studies in Geography having leisure as an object.379110

Phonon-phonon interactions and phonon damping in carbon nanotubes

We formulate and study the effective low-energy quantum theory of interacting long-wavelength acoustic phonons in carbon nanotubes within the framework of continuum elasticity theory. A general and analytical derivation of all three- and four-phonon processes is provided, and the relevant coupling constants are determined in terms of few elastic coefficients. Due to the low dimensionality and the parabolic dispersion, the finite-temperature density of noninteracting flexural phonons diverges, and a nonperturbative approach to their interactions is necessary. Within a mean-field description, we find that a dynamical gap opens. In practice, this gap is thermally smeared, but still has important consequences. Using our theory, we compute the decay rates of acoustic phonons due to phonon-phonon and electron-phonon interactions, implying upper bounds for their quality factor.Comment: 15 pages, 2 figures, published versio

Assessing Vancomycin Dosing Per Pharmacy in Elderly Patients Over the Age of 74 Years

Vancomycin has a complex pharmacokinetic profile and carries potential risks for nephrotoxicity and ototoxicity. The pharmacokinetic profile in elderly patients significantly differs from that of younger patients. It is common practice in many institutions for pharmacists to intentionally round serum creatinine levels to 1 mg/dl in elderly patients with levels \u3c1 mg/ dl to avoid overestimating clearance and toxicities. This can potentially lead to underestimation of creatinine clearance, and subsequently lead to vancomycin under dosing. The aim of this study was to evaluate vancomycin target trough attainment and the time to trough attainment with vancomycin dosing per pharmacy in elderly patients

Peierls Mechanism of the Metal-Insulator Transition in Ferromagnetic Hollandite K2Cr8O16

Synchrotron X-ray diffraction experiment shows that the metal-insulator transition occurring in a ferromagnetic state of a hollandite K$_2$Cr$_8$O$_{16}$ is accompanied by a structural distortion from the tetragonal $I4/m$ to monoclinic $P112_{1}/a$ phase with a $\sqrt{2}\times\sqrt{2}\times 1$ supercell. Detailed electronic structure calculations demonstrate that the metal-insulator transition is caused by a Peierls instability in the quasi-one-dimensional column structure made of four coupled Cr-O chains running in the $c$-direction, leading to the formation of tetramers of Cr ions below the transition temperature. This furnishes a rare example of the Peierls transition of fully spin-polarized electron systems.Comment: Phys. Rev. Lett., in press, 5 pages, 3 figure