Transition on the entropic elasticity of DNA induced by intercalating molecules

We use optical tweezers to perform stretching experiments on DNA molecules when interacting with the drugs daunomycin and ethidium bromide, which intercalate the DNA molecule. These experiments are performed in the low-force regime from zero up to 2 pN. Our results show that the persistence length of the DNA-drug complexes increases strongly as the drug concentration increases up to some critical value. Above this critical value, the persistence length decreases abruptly and remains practically constant for larger drug concentrations. The contour length of the molecules increases monotonically and saturates as drugs concentration increases. Measured in- tercalants critical concentrations for the persistence length transition coincide with reported values for the helix-coil transition of DNA-drug complexes, obtained from sedimentation experiments.Comment: This experimental article shows and discuss a transition observed in the persistence length of DNA molecules when studied as a function of some intercalating drug concentrations, like daunomycin and ethidium bromide. It has 15 pages and 4 figures. The article presented here is in preprint forma

Fundamental Oscillation Periods of the Interlayer Exchange Coupling beyond the RKKY Approximation

A general method for obtaining the oscillation periods of the interlayer exchange coupling is presented. It is shown that it is possible for the coupling to oscillate with additional periods beyond the ones predicted by the RKKY theory. The relation between the oscillation periods and the spacer Fermi surface is clarified, showing that non-RKKY periods do not bear a direct correspondence with the Fermi surface. The interesting case of a FCC(110) structure is investigated, unmistakably proving the existence and relevance of non-RKKY oscillations. The general conditions for the occurrence of non-RKKY oscillations are also presented.Comment: 34 pages, 10 figures ; to appear in J. Phys.: Condens. Mat

Cosmic String Wakes in Scalar-Tensor Gravities

The formation and evolution of cosmic string wakes in the framework of a scalar-tensor gravity are investigated in this work. We consider a simple model in which cold dark matter flows past an ordinary string and we treat this motion in the Zel'dovich approximation. We make a comaprison between our results and previous results obtained in the context of General Relativity. We propose a mechanism in which the contribution of the scalar field to the evolution of the wakes may lead to a cosmological observation.Comment: Replaced version to be published in the Classical and Quantum Gravit

Lifestyles and surveillance of sexual and reproductive women’s health

Abstract: Background: The epidemic increase of diseases is closely related to lifestyle changes. The low adhesion to breast self-examination and cervical cytology hinders prevention and early diagnosis during the asymptomatic state of two silent diseases, with nonspecific symptoms that are a major cause of death by cancer in the Portuguese female population. Objectives: To analyze the influence of sociodemographic variables and lifestyles in the surveillance of sexual and reproductive health of Portuguese women. Methods: Quantitative, non-experimental, correlational and cross-sectional study, conducted with a non-probabilistic convenience sample of 522 women aged between 18 and 67 years old, who applied the questionnaires about Breast self-examination, Knowledge about cervical cancer and the Inventory "My Lifestyle" (Ribeiro, 1993. Results: The average age of women is 38.89 years old. Women aged 31-37 years old (28.6%), Portuguese (99.1%), cohabiting with a partner and / or child (74.0%), with an active employment status (67 5%), residing in urban areas (55.8%) with higher education and attending family planning consultations have better lifestyles, without statistical significance (F = 0.016, p = 0.899). Conclusions: Healthy behaviors and lifestyles are crucial to good overall health. Adhesion to surveillance of sexual and reproductive women’s health is influenced by several factors, including the place of residence, employment status and lifestyles. These variables must be considered by health professionals when planning periodic screenings.info:eu-repo/semantics/publishedVersio

Upper bound for the conductivity of nanotube networks

Films composed of nanotube networks have their conductivities regulated by the junction resistances formed between tubes. Conductivity values are enhanced by lower junction resistances but should reach a maximum that is limited by the network morphology. By considering ideal ballistic-like contacts between nanotubes we use the Kubo formalism to calculate the upper bound for the conductivity of such films and show how it depends on the nanotube concentration as well as on their aspect ratio. Highest measured conductivities reported so far are approaching this limiting value, suggesting that further progress lies with nanowires other than nanotubes.Comment: 3 pages, 1 figure. Minor changes. Accepted for publication in Applied Physics Letter

Critical temperature of a fully anisotropic three-dimensional Ising model

The critical temperature of a three-dimensional Ising model on a simple cubic lattice with different coupling strengths along all three spatial directions is calculated via the transfer matrix method and a finite size scaling for L x L oo clusters (L=2 and 3). The results obtained are compared with available calculations. An exact analytical solution is found for the 2 x 2 oo Ising chain with fully anisotropic interactions (arbitrary J_x, J_y and J_z).Comment: 17 pages in tex using preprint.sty for IOP journals, no figure

Universal data warehouse management system research proposal

The author proposes research on the creation of a Data Warehouse Management System (involving all its domains: logical and conceptual data model and language, user interface, software and hardware) that is more flexible than current alternatives in adapting to changes in business requirements, while still improving value to the user.info:eu-repo/semantics/publishedVersio