Interaction of cylindrical polymer brushes in dilute and semi-dilute solution

We present a systematic study of flexible cylindrical brush-shaped macromolecules in a good solvent by small-angle neutron scattering (SANS), static light scattering (SLS), and by dynamic light scattering (DLS) in dilute and semi-dilute solution. The SLS and SANS data extrapolated to infinite dilution lead to the shape of the polymer that can be modeled in terms of a worm-like chain with a contour length of 380 nm and a persistence length of 17.5 nm. SANS data taken at higher polymer concentration were evaluated by using the polymer reference interaction site model (PRISM). We find that the persistence length reduce from 17.5 nm at infinite dilution to 5.3 nm at the highest concentration (volume fraction 0.038). This is comparable with the decrease of the persistence length in semi-dilute concentration predicted theoretically for polyelectrolytes. This finding reveals a softening of stiffness of the polymer brushes caused by their mutual interaction

Perfil epidemiológico e morbimortalidade dos pacientes submetidos à reconstrução de trânsito intestinal: experiência de um centro secundário do nordeste Brasileiro Epidemiologic profile and morbimortality of patients undergoing to intestinal transit reconstruction: experience of a secundary health service in Brazil northeast

Racional- A reconstrução do trânsito intestinal não está isenta de riscos cirúrgicos e apresenta taxas consideráveis de complicações pós-operatórias, sendo que a infecção continua a ser um dos maiores desafios existentes neste procedimento. Métodos- Foram analisados retrospectivamente 86 prontuários de pacientes com colostomia ou ileostomia, através de fatores que tivessem impacto sobre a morbimortalidade após a reconstrução de trânsito intestinal, de janeiro de 2003 a abril de 2009. Resultados- Houve 20 mulheres e 60 homens, com idade média de 43 anos. A colostomia em alça (n: 34) e o trauma abdominal indicando colostomia ou ileostomia foram as condições mais frequentes. O intervalo médio entre a confecção do estoma e a reconstrução de trânsito intestinal foi 15,7 meses. O índice de morbidade foi 56,8%, sendo a infecção incisional a complicação mais comum (27.47%). A permanência hospitalar média foi 7,6 dias. Houve regressão linear positiva entre permanência hospitalar pós-operatória e a idade do paciente. Demonstrou-se associação estatisticamente significativa entre o prolongamento da permanência hospitalar e a ocorrência de complicações (p<0,001). Conclusão- Pode-se inferir que ocorrência de complicações pós-operatórias e idade associam-se a prolongamento da permanência hospitalar.<br>Background - The reconstruction of the intestinal tract is not surgical complications risk-free and is associated to postoperative complications high rates; furthermore, infection remains the hardest challenge in this procedure. Methods - Retrospectively, eighty-six patients with intestinal stomas were analyzed through factors that impact on the morbimortality afterwards intestinal transit reconstruction, since January 2003 to April 2009. Results - Loop colostomy (n=34) and abdominal trauma implicating 38.2% of indications to colostomy or ileostomy were the most frequent conditions. The mean interval between stoma confection and intestinal transit reconstruction was 15.7 months. The morbidity frequency was 56.8% and incisional infection was its commonest complication (27.47%). The mean inpatient length of stay was 7.6 days. There was positive linear regression between post-operative inpatient length of stay and inpatient's age. Inpatient length of stay prolongation is associated to occurrence of complications (p<0,001). Conclusion - Post-operative complications and age are associated to inpatient length of stay prolongation