Enhancement of the Biological and Mechanical Performances of Sintered Hydroxyapatite by Multiple Ions Doping

In the present work, hydroxyapatite (HA) nanoparticles doped with Mg2+, Sr2+, and Zn2+ ions are developed by wet neutralization method and then sintered at 1,250°C to obtain bulk consolidated materials. Physicochemical and microstructural analyses show that the presence of doping ions in the HA structure induced the formation of βTCP as secondary phase, during the sintering process, and we found that this effect is depending on the stability of the various doping ions in the hydroxyapatite lattice itself. We also found that the formation of βTCP as secondary phase, in turn, confines the grain growth of HA induced by the high-temperature sintering process, thus leading to a strong increase of the flexural strength of the bulk materials, according to Hall-Petch-like law. Furthermore, we found that the doping ions enter also in the structure of the βTCP phase; besides the grain growth confinement, also the solubility and ion release ability of the final materials were enhanced. In addition to ameliorate the mechanical performance, the described phenomena also activate multiple biofunctionalities: (i) ability to upregulate various genes involved in the osteogenesis, as obtained by human adipose stem cells culture and evaluated by array technology; (ii) enhanced resistance to the adhesion and proliferation of Gram+ and Gram– bacterial strains. Hence, our results open a perspective for the use of sintered multiple ion-doped HA to develop ceramic biodevices, such as plates, screws, or other osteosynthesis media, with enhanced strength, osteointegrability, and the ability to prevent post-surgical infections

Apelin-13 limits infarct size and improves cardiac postischemic mechanical recovery only if given after ischemia

We studied whether apelin-13 is cardioprotective against ischemia/reperfusion injury if given as either a pre- or postconditioning mimetic and whether the improved postischemic mechanical recovery induced by apelin-13 depends only on the reduced infarct size or also on a recovery of function of the viable myocardium. We also studied whether nitric oxide (NO) is involved in apelin-induced protection and whether the reported ischemia-induced overexpression of the apelin receptor (APJ) plays a role in cardioprotection. Langendorff-perfused rat hearts underwent 30 min of global ischemia and 120 min of reperfusion. Left ventricular pressure was recorded. Infarct size and lactate dehydrogenase release were determined to evaluate the severity of myocardial injury. Apelin-13 was infused at 0.5 \u3bcM concentration for 20 min either before ischemia or in early reperfusion, without and with NO synthase inhibition by N(G)-nitro-l-arginine (l-NNA). In additional experiments, before ischemia also 1 \u3bcM apelin-13 was tested. APJ protein level was measured before and after ischemia. Whereas before ischemia apelin-13 (0.5 and 1.0 \u3bcM) was ineffective, after ischemia it reduced infarct size from 54 \ub1 2% to 26 \ub1 4% of risk area (P < 0.001) and limited the postischemic myocardial contracture (P < 0.001). l-NNA alone increased postischemic myocardial contracture. This increase was attenuated by apelin-13, which, however, was unable to reduce infarct size. Ischemia increased APJ protein level after 15-min perfusion, i.e., after most of reperfusion injury has occurred. Apelin-13 protects the heart only if given after ischemia. In this protection NO plays an important role. Apelin-13 efficiency as postconditioning mimetic cannot be explained by the increased APJ level

Making Space, Making Place: Digital Togetherness and the Redefinition of Migrant Identities Online

Immigrants have played a fundamental role in shaping the life and form of urban public spaces for generations. Their efforts, as many scholars have observed, mostly aimed at creating places of comfort in new and sometimes hostile receiving countries. In recent years, the combined contribution of the built environment and screen-based experiences have shaped migrants’ sense of community and belonging, thus making the concept of online community central to ideas about space and public life. Drawing upon a 3-year online ethnography, the article discusses to what extent new media constitute spaces of digital togetherness, where diasporic experiences and transnational identities are constructed and negotiated. It presents a transnational model of creative media consumption, which helps give insight as to how diasporas and ethnic minorities contribute to the transformation of public space in the Digital Age

Chemical characterization of some substituted hydroxyapatites

Synthetic multi-substituted hydroxyapatite nano powders containing silicon and or carbonate prepared by a wet chemical method. The process parameters are set up to allow the simultaneous substitution of carbonate and silicon ions in the place of phosphorus. The chemical and structural characterizations of the prepared powders are determined with the aid of; XRF, ICP, XRD and FTIR. The results show that, the ion substitution in the crystal lattice of HA caused a change in the unit cell dimensions and affected the degree of crystallization of the produced powders. The apatite formation abilityy of the prepared discs from the synthesized powders is determined by immersing in SBF solution for different periods. The degree of ion release was determined in the obtained solutions. The examined surface of the immersed discs under SEM and analyzed by CDS showed a more dense HA layer than those of un-substituted ones. The HA with the substituted silicon and carbonate ions, showed the highest solubility with greater rate of ion release, compared with carbonate-free powder. All prepared powders took sodium ion from the SBF solution during immersion, which was not recorded before

‘Sometimes there’s racism towards the French here’: xenophobic microaggressions in pre-2016 London as articulations of symbolic violence

This article discusses xenophobic microaggressions (Pierce, 1970) experienced by members of the French community in London prior to the EU-Membership Referendum in 2016. Acting at the interface of agency and passivity, implicitness and complicity, they go unseen in the social space despite their omnipresence. Through a close reading of empirical data collected as part of an ethnographic study, the article posits that these microaggressions are articulations of historically embedded anti-French ‘symbolic violence’ (Bourdieu and Wacquant, 1992; Bourdieu, 1993). The three main areas addressed are humour, intersectionality and the reproductive nature of the phenomenon (Bourdieu and Passeron, 1970; Bourdieu, 1972)