Stability Limits and Defect Dynamics in Ag Nanoparticles Probed by Bragg Coherent Diffractive Imaging.

Dissolution is critical to nanomaterial stability, especially for partially dealloyed nanoparticle catalysts. Unfortunately, highly active catalysts are often not stable in their reactive environments, preventing widespread application. Thus, focusing on the structure-stability relationship at the nanoscale is crucial and will likely play an important role in meeting grand challenges. Recent advances in imaging capability have come from electron, X-ray, and other techniques but tend to be limited to specific sample environments and/or two-dimensional images. Here, we report investigations into the defect-stability relationship of silver nanoparticles to voltage-induced electrochemical dissolution imaged in situ in three-dimensional detail by Bragg coherent diffractive imaging. We first determine the average dissolution kinetics by stationary probe rotating disk electrode in combination with inductively coupled plasma mass spectrometry, which allows in situ measurement of Ag+ ion formation. We then observe the dissolution and redeposition processes in single nanocrystals, providing unique insight about the role of surface strain, defects, and their coupling to the dissolution chemistry. The methods developed and the knowledge gained go well beyond a "simple" silver electrochemistry and are applicable to all electrocatalytic reactions where functional links between activity and stability are controlled by structure and defect dynamics.

Influence of ibuprofen addition on the properties of a bioactive bone cement.

Bioactive bone cements can promote bone growth and the formation of a strong chemical bond between the implant and bone tissue increasing the lifetime of the prosthesis. This study aims at synthesizing a new bioactive bone cement with different amounts of ibuprofen (5, 10 and 20 wt%) using a low toxicity activator, and investigating its in vitro release profile. The effect of ibuprofen (IB) on the setting parameters, residual monomer and bioactivity in synthetic plasma was also evaluated. It was verified that the different IB contents do not prevent the growth of calcium phosphate aggregates on composite surfaces, confirming that the cements are potentially bioactive. A relevant advantage of these formulations was a significant improvement in their curing parameters with increasing IB amount, associated to a reduction of the peak temperature and an extension of the setting time. The investigated cements released an average of about 20 % of the total incorporated ibuprofen during 30 days test, with IB20 liberating the highest percentage of drug 20.6 %, and IB10 and IB5, respectively 19.1 and 17.6 %. This behavior was attributed to the low solubility of this drug in aqueous media and was also related with the hydrophobic character of the polymer. Regarding the therapeutic concentration sufficient to suppress inflammation, the cement with 10 % of ibuprofen achieved the required release rate for 1 week and the cement with 20 % for 2 weeks.

Silicate and borate glasses as composite fillers: a bioactivity and biocompatibility study.

Composites filled with a silicate glass (CSi) and a new borate glass (CB) were developed and compared in terms of their in vitro behaviour both in acellular and cellular media. Acellular tests were carried out in SBF and the composites were characterized by SEM-EDS, XRD and ICP. Biocompatibility studies were investigated by in vitro cell culture with MG-63 osteoblast-like and human bone marrow cells. The growth of spherical calcium phosphate aggregates was observed in acellular medium on all composite surfaces indicating that these materials became potentially bioactive. The biological assessment resulted in a dissimilar behavior of the composites. The CSi demonstrated an inductive effect on the proliferation of cells. The cells showed a normal morphology and high growth rate when compared to standard culture plates. Contrarily, inhibition of cell proliferation occurred in the CB probably due to its high degradation rate, leading to high B and Mg ionic concentration in the cell culture medium.

Resource Utilization and Temporal Segregation of Scarabaeinae (Coleoptera, Scarabaeidae) Community in a Caatinga Fragment.

We characterized dung beetles food preference and diel activity and examined the way such characteristics may structure a Scarabaeinae community in a dry forest. We sampled a fragment of Arboreal Caatinga in Milagres, Bahia, Brazil, during the dry and wet seasons, using baited pitfall (bovine spleen, human feces, cow dung, and rotten banana). Species were classified by activity (nocturnal and diurnal) and food preference (coprophagous, necrophagous, saprophagous, copro-necrophagous, and generalist). In total, 1,581 individuals belonging to 16 morphospecies were sampled, with six new records for Caatinga. The dung beetles were mainly from generalist and coprophagous species; seven species presented nocturnal activity, and five were diurnal. There was higher species richness during the day and greater abundance during the night. Species composition differences were influenced by functional guilds and beetle size according to temporal segregation. These factors may be related to physiological, morphological, and behavioral differences.

Acrylic formulations containing bioactive and biodegradable fillers to be used as bone cements: properties and biocompatibility assessment.

The solid phase of bioactive self-curing acrylic cements was modified by different biodegradable fillers such as poly(3-hydroxybutyrate) (PHB) and its copolymer with hydroxyvalerate (PHBV). The addition of the biodegradable fillers made the cement partially degradable, which is important to allow new bone replacement and ingrowth. The thermal analysis, crystallinity, curing parameters, mechanical properties, degradation and cellular tests were studied in order to characterize the cement performance. Within this context it was verified that the incorporation of the PHBV polymer made the cement more resistant, reaching values within the range reported for typical PMMA bone cements. The results also showed that the cement filled with PHBV took up more water than the cement with PHB after 60 days, for all studied formulations. Regarding the osteoblastic cytocompatibility assessment, the inclusion of the PHBV greatly improved the biological response in both cements filled with the silicate or the borate glass, compared to the inclusion of the PHB. The importance of this novel approach resides on the combination of the properties of the cements components and the possibility of allowing bone regeneration, improving the interfaces with both the prosthesis and the bone, and leading to a new material with suitable performance for application as bone cement.

New records, threatens and conservation status for Dichotomius schiffleri Vaz-de-Mello, Louzada & Gavino (Coleoptera: Scarabaeidae): an endangered dung beetle species from Brazilian atlantic forest ecosystems.

Dichotomius schiffleri Vaz-de-Mello et al is often cited as endemic to the preserved coastal sandy-dune vegetation (restinga) of Guriri Island, Espírito Santo state, and is included in the Brazilian List of Endangered Fauna as "critically endangered" (CR). However, we recorded its occurrence in twelve additional sites along the coasts of Espírito Santo, Bahia, Sergipe and Pernambuco. The geographic distribution of D. schiffleri is limited to the coastal Atlantic Forest domain, mainly in preserved restinga patches. We recommend that D. schiffleri remains in the List of Endangered species, but in the "endangered" (EN) category, according to the IUCN criteria.