423 research outputs found
Perspectives on the viscoelasticity and flow behavior of entangled linear and branched polymers
We briefly review the recent advances in the rheology of entangled polymers
and identify emerging research trends and outstanding challenges, especially
with respect to branched polymers. Emphasis is placed on the role of
well-characterized model systems, as well as the synergy of
synthesis-characterization, rheometry and modeling/simulations. The theoretical
framework for understanding the observed linear and nonlinear rheological
phenomena is the tube model which is critically assessed in view of its
successes and shortcomings, whereas alternative approaches are briefly
discussed. Finally, intriguing experimental findings and controversial issues
that merit consistent explanation, such as shear banding instabilities,
multiple stress overshoots in transient simple shear and enhanced steady-state
elongational viscosity in polymer solutions, are discussed, whereas future
directions such as branch point dynamics and anisotropic monomeric friction are
outlined.Comment: 25 pages, accepted for publication in Journal of Physics Condensed
Matter (August 2015
Prolonged antimicrobial activity of PMMA bone cement with embedded gentamicin-releasing silica nanocarriers
Antibiotic laden bone cements are regularly employed to prevent infections after joint replacement surgeries. We have developed silica nanocarriers loaded with gentamicin as a drug delivery system to be dispersed in poly methyl-methacrylate (PMMA) bone cement for controlling and extending the release of the antibiotic from bone cements, thus proving a prolonged antimicrobial activity. Layer-by-layer self-assembly was used to deposit gentamicin between alginate layers and two different poly ÎČ-amino esters on the silica nanoparticles. The release of gentamicin from PMMA bone cement containing silica nanocarriers continued for about 30 days compared to 6 days when the same amount of antibiotic was added as a pure powder (as in commercial formulations); moreover, the medium containing the released antimicrobial drug was capable of preventing the growth of numerous bacteria species responsible for prosthetic joint infections (both catalogue strains and clinical isolates) for longer periods of time than in the case of commercial formulations, thus confirming the extended antimicrobial properties of the drug once released from the carrier. No detrimental effects toward human osteoblasts were also observed; moreover, bone cement material characteristics such as curing time, water uptake, and mechanical properties were unaffected when the silica nanocarriers were added
Notes sur les habitudes alimentaires de Rioraja agassizi (Chondrichthyes, Rajidae) dans le sud du Brésil.
Copyright © 2011 SociĂ©tĂ© Française dâIchtyologie.Feeding habits of the skate Rioraja agassizi were analyzed in southeastern Brazil from samples obtained along SĂŁo Paulo coast. A total of 258 specimens were examined, ranging between 96 and 532 mm total length. About 57.85% were females and 42.15% were males, resulting in a 1:1.37 sex-ratio to females. From 223 stomachs collected (94 males and 129 females) empty stomachs represented only 1.4%. Nine prey categories were identified: Polychaeta, Copepoda, Cumacea, Isopoda, Gammaridea, Dendrobranchiata, Brachyura, Teleostei, and one non-animal category (nonidentifiable items). Crustaceans were the most important item, indicating that the species has a carcinophagic preference. The presence of fish was just verified in juveniles and some adult individuals, with predominance in summer. Sex, maturity stage and seasonality did not influence the feeding habits of the species.RĂSUMĂ: Les habitudes alimentaires de Rioraja agassizi on Ă©tĂ© analysĂ©es dans le sud-ouest du BrĂ©sil, tout au long de la cĂŽte de lâĂtat de SĂŁo Paulo. Au total, 258 exemplaires ont Ă©tĂ© examinĂ©s, leurs tailles variant entre 96 et 532 mm de longueur totale. Les femelles ont reprĂ©sentĂ© 57,85% de lâĂ©chantillon, conduisant Ă un sex-ratio secondaire de 1 : 1,37 en leur faveur. Sur 223 estomacs recueillis (94 mĂąles et 129 femelles) ceux qui Ă©taient vides reprĂ©sentaient seulement 1,4%. Neuf catĂ©gories de proies ont Ă©tĂ© identifiĂ©es: Polychaeta, Copepoda, Cumacea, Isopoda, Gammaridea, Dendrobranchiata, Brachyura, Teleostei, et des restes inorganiques (items non identifiables). Les crustacĂ©s sont la proie la plus importante, indiquant une prĂ©fĂ©rence carcinophage pour cette espĂšce. La prĂ©sence de poissons a Ă©tĂ© vĂ©rifiĂ©e seulement dans les estomacs de juvĂ©niles avec une prĂ©dominance durant les mois dâĂ©tĂ©. Aucune influence des variables âsexeâ, âmaturitĂ©â et âsaisonâ sur les habitudes alimentaires nâa Ă©tĂ© dĂ©tectĂ©e
Effect of Sugars on Gelation Kinetics of Gelatin Gels
We investigate the rheological behavior of aqueous solutions containing animal gelatin, sugars and polyols. The aim is to study how the gelation kinetics, transition temperatures and gel strengths of an aqueous gelatin solution can be affected by the progressive addition of co-solutes. Aqueous solutions with a fixed mass percentage of gelatin of 6.8 wt% were prepared at various concentrations of sugars and polyols. Through Dynamic Temperature Ramp tests, performed at various ramp rates, and Dynamic Time Sweep and Dynamic Frequency Sweep tests, carried out at different temperatures, it was possible both to evaluate the transition temperatures and to monitor the gelation kinetics of the samples. It was found that the contribution of co-solutes positively affects both the gelation process and the thermal stability of the aqueous gelatin solution by reducing the gelation time and improving the mechanical properties of the gel in terms of network elasticity
Indocyanine green labeling for optical and photoacoustic imaging of mesenchymal stem cells after in vivo transplantation
Head and neck region consolidation radiotherapy and prophylactic cranial irradiation with hippocampal avoidance delivered with helical tomotherapy after induction chemotherapy for non-sinonasal neuroendocrine carcinoma of the upper airways
Background: Non-sinonasal neuroendocrine carcinomas (NSNECs) of the head and neck are considered an unfrequent clinico-pathological entity. Combined modality treatment represents an established therapeutic option for undifferentiated forms where distant metastasis is a common pattern of failure.Methods: We report on a case of NSNEC treated with sequential chemo-radiation consisting of 6 cycles of cisplatin and etoposide followed by loco-regional radiation to the head and neck and simultaneous prophylactic cranial irradiation to prevent from intracranial spread, delivered with helical tomotherapy with the 'hippocampal avoidance' technique in order to reduce neuro-cognitive late effects.Results: One year after the end of the whole combined modality approach, the patient achieved complete remission, with no treatment-related sub-acute and late effects.Conclusions: The present report highlights the importance of multidisciplinary management for NSNECs of the head and neck, as the possibility to achieve substantial cure rates with mild side effects with modern radiotherapy techniques. © 2012 Franco et al; BioMed Central Ltd
Local representative democracy and protest politics:the case of the Five-star Movement
In recent years, protest politics has become a relevant phenomenon in various European countries. Italy has witnessed the rise of the Five-star Movement (M5S), an anti-establishment party, which, at the 2013 general election, obtained one-fourth of the total votes. However, the story of this âparty-movementâ started at the local level, as a civic network aimed at changing administrative practices in municipal government. By using an original dataset on representation in 671 Italian municipalities from 2010 to 2014, this article aims to explain not only the subnational political success of the M5S but also the challenges and contradictions that a newly formed movement faces in multi-level electoral arenas
Italian multicenter study on infection hazards during dental practice: Control of environmental microbial contamination in public dental surgeries
Background.
The present study assessed microbial contamination in Italian dental surgeries.
Methods.
An evaluation of water, air and surface microbial contamination in 102 dental units was carried out in eight Italian cities.
Results.
The findings showed water microbial contamination in all the dental surgeries; the proportion of water samples with microbial levels above those recommended decreased during working. With regard to Legionella spp., the proportion of positive samples was 33.3%. During work activity, the index of microbial air contamination (IMA) increased. The level of microbial accumulation on examined surfaces did not change over time.
Conclusion.
These findings confirm that some Italian dental surgeries show high biocontamination, as in other European Countries, which highlights the risk of occupational exposure and the need to apply effective measures to reduce microbial loads
Schmitt e o problema da democracia: nostalgia da transcendĂȘncia ou a representação como questĂŁo para a democracia
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