Rotational Diffusion of Macromolecules and Nanoparticles Modeled as Non-Overlapping Bead Arrays in an Effective Medium

In this work, the retarding influence of a gel on the rotational motion of a macromolecule is investigated within the framework of the Effective Medium (EM) model. This is an extension of an earlier study that considered the effect of a gel on the translational motion of a macromolecule [Allison, S. et al. J. Phys. Chem. B 2008, 112, 5858-5866]. The macromolecule is modeled as an array of non-overlapping spherical beads with no restriction placed on their size or configuration. Specific applications include the rotational motion of right circular cylinders and wormlike chains modeled as strings of identical touching beads. The procedure is then used to examine the electric birefringence decay of a 622 base pair DNA fragment in an agarose gel. At low gel concentration (M £ 0.010 gm/mL), good agreement between theory and experiment is achieved if the persistence length of DNA is taken to be 65 nm and the gel fiber radius of agarose is taken to be 2.5 nm. At higher gel concentrations, the EM model substantially underestimates the rotational relaxation time of DNA and this can be attributed to the onset of direct interactions that become significant when the effective particle size becomes comparable to the mean gel fiber spacing

Expiratory airflow at 7–8 years of age in children born extremely low birthweight from 14 years before to 14 years after the introduction of exogenous surfactantResearch in context

Summary: Background: It is unclear if expiratory airflow in survivors born extremely low birth weight (ELBW; 500–999 g) has improved after the introduction of exogenous surfactant into clinical practice in 1991. The primary aim of this study was to describe the changes in airflow at 7–8 years of age of survivors born ELBW in five discrete cohorts from 14 years before to 14 years after the introduction of exogenous surfactant into clinical practice. Methods: The cohorts comprised consecutive survivors born ELBW in 1977–82 and 1985–87 at the Royal Women's Hospital, Melbourne, and in 1991–92, 1997 and 2005 in the state of Victoria, Australia. Survival rates to 2-years of age for infants born ELBW in the state of Victoria rose from approximately 1-in-4 to 3-in-4 over the time of this study. Expiratory airflow measurements at 7–8 years included the forced expired volume in 1 s (FEV1), converted to z-scores for age, height, sex, and race. Findings: There were 596 ELBW participants with expiratory flow data, 280 (47%) of whom had bronchopulmonary dysplasia (BPD). Overall, there was little change in zFEV1 over the 28-year period (mean change per year; 0.003, 95% CI −0.010, 0.015, P = 0.67). There was, however, evidence of an interaction between BPD and year; zFEV1 in those who had BPD fell over time (mean change per year −0.019, 95% CI −0.037, −0.009, P = 0.035), whereas zFEV1 improved in those who did not have BPD (mean change per year 0.021, 95% CI 0.006, 0.037, P = 0.007). Interpretation: Contrary to recent evidence, expiratory airflow of children born ELBW has not improved with the introduction of surfactant, and may be deteriorating in those who had BPD. Funding: National Health and Medical Research Council (Australia); Victorian Government’s Operational Infrastructure Support Program

29 novembre 1916

29 novembre 1916 Mon cher Pierre, D'abord l'affaire de Jean [1]. J'ai pensé qu'en ces matières il valait mieux ne pas tarder et perdre du temps. J'ai fait remettre aujourd'hui une note à Pellé. Tu sais que le général est un ancien camarade de Stan. et que je suis en très bons termes avec lui. Je souhaite que son intervention serve à tranquilliser Paul et ta belle-sœur [2]. Je ne parle pas du Comité secret, tu as dû en apprendre aussi bien que moi toutes les circonstances. Si tu avais pu venir..