Dielectric relaxations in PEEK by combined dynamic dielectric spectroscopy and thermally stimulated current

The molecular dynamics of a quenched poly (ether ether ketone) (PEEK) was studied over a broad frequency range from 10-3 to 106 Hz by combining dynamic dielectric spectroscopy (DDS) and thermo-stimulated current (TSC) analysis. The dielectric relaxation losses e00 KK has been determined from the real part e0 T(x) thanks to Kramers–Kronig transform. In this way, conduction and relaxation processes can be analyzed independently. Two secondary dipolar relaxations, the c and the b modes, corresponding to non-cooperative localized molecular mobility have been pointed out. The main a relaxation appeared close to the glass transition temperature as determined by DSC; it has been attributed to the delocalized cooperative mobility of the free amorphous phase. The relaxation times of dielectric relaxations determined with TSC at low frequency converge with relaxation times extracted from DDS at high frequency. This correlation emphasized continuity of mobility kinetics between vitreous and liquid state. The dielectric spectroscopy exhibits the ac relaxation, near 443 K, which has been associated with the rigid amorphous phase confined by crystallites. This present experiment demonstrates coherence of the dynamics of the PEEK heterogeneous amorphous phase between glassy and liquid state and significantly improve the knowledge of molecular/dynamic structure relationships

Assembly, organization, and function of the COPII coat

A full mechanistic understanding of how secretory cargo proteins are exported from the endoplasmic reticulum for passage through the early secretory pathway is essential for us to comprehend how cells are organized, maintain compartment identity, as well as how they selectively secrete proteins and other macromolecules to the extracellular space. This process depends on the function of a multi-subunit complex, the COPII coat. Here we describe progress towards a full mechanistic understanding of COPII coat function, including the latest findings in this area. Much of our understanding of how COPII functions and is regulated comes from studies of yeast genetics, biochemical reconstitution and single cell microscopy. New developments arising from clinical cases and model organism biology and genetics enable us to gain far greater insight in to the role of membrane traffic in the context of a whole organism as well as during embryogenesis and development. A significant outcome of such a full understanding is to reveal how the machinery and processes of membrane trafficking through the early secretory pathway fail in disease states

[Beds dedicated to stroke patients in postacute care units. Are national guidelines followed?]

International audienceOBJECTIVE: We sought to determine the number of beds necessary for stroke patients in postacute care units and to measure the relevance of the national guidelines on required number of beds. METHODOLOGY: We conducted an epidemiological follow-up of a cohort, what allowed for evaluating stroke care under real-life conditions. We applied the French guidelines for transfer of patients to postacute care wards. RESULTS: Of the 605 stroke patients hospitalised, 156 with a mean age of 72 years were included. A total of 64 (41%) could return home directly from the acute care wards and 73 (47%) were referred to postacute care wards. Among the latter patients, 31 (43%) were transferred to a physical medicine and rehabilitation (PMR) unit and 42 (57%) to a geriatric unit. The 19 remaining patients died in acute care. Of the 137 surviving patients, 46.7% returned directly home and 53.2% were referred to postacute care wards. Of patients older than 80 years, 74% were transferred to a geriatric unit, whereas 76% of the patients less than 80 years were transferred to a PMR unit. DISCUSSION-CONCLUSION: The national guidelines are based on a rate of discharge of about 24% of stroke patients to postacute care wards. In our study, we found that 47% were transferred to such wards. If the guidelines are applied, 19 beds dedicated to stroke patients would be necessary for postacute stroke care on a national level, or double that (36) on a regional level. Of these 36 beds, 16 to 24 should be PMR beds. The calculation of the number of beds necessary often rests on a simple transposition of the results of the studies and not on an objective evaluation according to the local context. Studies of longitudinal follow-up of cohorts such as this seem essential to evaluate needs and measure the relevance of the national guidelines

[Early prediction of functional outcome one year after initial unilateral hemispheric stroke]

International audienceBACKGROUND AND PURPOSE: Several prognostic factors have been identified for outcome after stroke. We conducted a study to determine early predictive factors of functional outcome one year after stroke and to evaluate which factors are independent predictors, with an aim of specifying the role of age, aphasia, unilateral neglect, cognitive impairment and family social support. METHODS: Observational cohort study of 156 patients. All patients admitted to the university hospital for initial unilateral hemispheric stroke were included. The study duration was two years (inclusion, one year, and follow-up, one year) .The initial evaluation of stroke was conducted at day 2 and day 15 and included the Motricity Index and Trunk Control Test, New Functional Ambulation Classification, Frenchay arm test, Mini-Mental State Examination, Boston Diagnostic Aphasia Examination, unilateral neglect evaluation, and depression. Data on functional recovery (Barthel Index) were collected at day 360. RESULTS: The average age of patients was 72 years. Age was correlated to social situation (P<0.01) and previous neurological impairment (P<0.01). A multiple regression analysis, including 14 initial clinical factors correlated with the Barthel Index score at day 360, revealed 4 independent early predictive factors of outcome: initial score of Barthel Index at day 2 and its progression from day 2 to day 15, disorders of the executive functions and previous neurological impairment. CONCLUSION: In our cohort, in accordance with previous studies, age, cognitive impairment, unilateral neglect, aphasia, depression and social situation are not independent factors of poor outcome after stroke as evaluated by the Barthel Index

Ibuprofen-loaded poly(epsilon-caprolactone) layered silicate nanocomposites prepared by hot melt extrusion

Ibuprofen loaded poly(epsilon-caprolactone) (PCL) layered silicate nanocomposites were prepared by hot-melt extrusion. The morphology and extent of dispersion of ibuprofen and layered silicate was studied using a combination of wide-angle X-ray diffraction (WAXD), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). Exhaustive examination across the length scales revealed the composite to have both an intercalated and exfoliated morphology. The ibuprofen was well dispersed and distributed throughout the PCL matrix. Most significantly, the static tensile and dynamic mechanical properties of PCL can be manipulated as a function of nanoclay loading and is dependent on the aspect ratio of clay platelets. The glass transition of PCL increased by up to 16A degrees C on addition of nanoclay, as determined from dynamic mechanical thermal analysis (DMTA). This behaviour was attributed to the constrained mobility of PCL chains intercalated between clay platelets and to the tethering of PCL chains by hydrogen bonding with platelet edges. As a consequence, PCL crystallisation was inhibited and confirmed from non-isothermal crystallisation experiments using differential scanning calorimetry (DSC). The fraction of PCL that was crystalline (X-c) decreased by 15% on addition of ibuprofen and nanoclay, although the temperature of crystallisation (T-c) did not change significantly. The dissolution of ibuprofen from PCL can be retarded by addition of layered silicates (nanoclays) to the polymer matrix