Resonant helical deformations in nonhomogeneous Kirchhoff filaments

We study the three-dimensional static configurations of nonhomogeneous Kirchhoff filaments with periodically varying Young's modulus. This type of variation may occur in long tandemly repeated sequences of DNA. We analyse the effects of the Young's modulus frequence and amplitude of oscillation in the stroboscopic maps, and in the regular (non chaotic) spatial configurations of the filaments. Our analysis shows that the tridimensional conformations of long filaments may depend critically on the Young's modulus frequence in case of resonance with other natural frequencies of the filament. As expected, far from resonance the shape of the solutions remain very close to that of the homogeneous case. In the case of biomolecules, it is well known that various other elements, besides sequence-dependent effects, combine to determine their conformation, like self-contact, salt concentration, thermal fluctuations, anisotropy and interaction with proteins. Our results show that sequence-dependent effects alone may have a significant influence on the shape of these molecules, including DNA. This could, therefore, be a possible mechanical function of the ``junk'' sequences.Comment: 18 pages (twocolumn), 5 figures Revised manuscrip

Sleep quality and chronic pain in community dwelling older adults: preliminary results

Background: The natural process of human aging causes biopsychosocial alterations, which can trigger chronic pain and poor sleep quality in older adults. Considering the high prevalence and possible association between these two clinical conditions, special attention from public health policies is necessary to provide quality aging. Objective: To verify if there is an association between chronic pain and sleep quality among older adults in the community. Methods: A quantitative, cross-sectional study on the association of chronic pain with the sleep quality among older people in the community. Participants were evaluated using the Pittsburgh Sleep Quality Index (PSQI); Visual Analog Pain scale; questionnaires of sociodemographic and clinical data, assessment of cognitive impairment through the Mini Mental State Examination, and anthropometric assessments. The data were submitted to descriptive statistics. The means between the groups of older people with and without chronic pain were compared using the Student's t test for independent samples and Pearson's correlation coefficient (r) was used to analyze the association of PSQI with pain intensity. Results: In total, 51 older women were included, with a mean age of 70 ± 8 years. The majority had a low level of education (52.9%), low financial income (64.7%), and chronic pain (56.9%). It was found that the older adults with chronic pain presented worse sleep quality when compared those without chronic pain and a moderate (r=0.595) and significant (p<0.01) correlation between sleep quality and the intensity of chronic pain was observed. Conclusion: Older adults in the community with chronic pain present worse sleep quality when compared to the older adults without pain. There is a strong correlation between the intensity of chronic pain and sleep quality in older adults; the greater the intensity of pain, the worse the sleep quality