Polymer/bioactive glass nanocomposites for biomedical applications: A review

Nanoscale bioactive glasses have been gaining attention due to their reported superior osteoconductivity when compared to conventional (micron-sized) bioactive glass materials. The combination of bioactive glass nanoparticles or nanofibers with polymeric systems enables the production of nanocomposites with potential to be used in a series of orthopedic applications, including scaffolds for tissue engineering and regenerative medicine. This review presents the state of art of the preparation of nanoscale bioactive glasses and corresponding composites with biocompatible polymers. The recent developments in the preparation methods of nano-sized bioactive glasses are reviewed, covering sol–gel routes, microemulsion techniques, gas phase synthesis method (flame spray synthesis), laser spinning, and electro-spinning. Then, examples of the preparation and properties of nanocomposites based on such inorganic bionanomaterials are presented, obtained using various polymer matrices, including polyesters such as poly(hydroxybutyrate), poly(lactic acid) and poly(caprolactone), and natural-based polymers such as polysaccharides (starch, chitin, chitosan) or proteins (silk fibroin, collagen). The physico-chemical, mechanical, and biological advantages of incorporating nanoscale bioactive glasses in such biodegradable nanocomposites are discussed and the possibilities to expand the use of these materials in other nanotechnology concepts aimed to be used in different biomedical applications are also highlighted.     

Alternating Current Electrophoretic Deposition of Antibacterial Bioactive Glass-Chitosan Composite Coatings

Alternating current (AC) electrophoretic deposition (EPD) was used to produce multifunctional composite coatings combining bioactive glass (BG) particles and chitosan. BG particles of two different sizes were used, i.e., 2 μm and 20–80 nm in average diameter. The parameter optimization and characterization of the coatings was conducted by visual inspection and by adhesion strength tests. The optimized coatings were investigated in terms of their hydroxyapatite (HA) forming ability in simulated body fluid (SBF) for up to 21 days. Fourier transform infrared (FTIR) spectroscopy results showed the successful HA formation on the coatings after 21 days. The first investigations were conducted on planar stainless steel sheets. In addition, scaffolds made from a TiAl4V6 alloy were considered to show the feasibility of coating of three dimensional structures by EPD. Because both BG and chitosan are antibacterial materials, the antibacterial properties of the as-produced coatings were investigated using E. coli bacteria cells. It was shown that the BG particle size has a strong influence on the antibacterial properties of the coatings.     

On the neutron spectrum and multiplication factor in the infinite homogeneous reactor

The analysis of the infinite homogeneous reactor can be useful to have a quick understanding of nuclear reactor phenomena. Thanks to the fact that the neutron emission spectrum from fission is modeled in order to depend neither on the energy of the incident neutron nor on the fissioning nuclide, the critical neutron balance equation can be transformed from an eigenvalue problem to a simple inhomogeneous system. Similar considerations can be addressed to the adjoint problem and to the generalized importance, which can be computed with direct expressions. After having derived the equations relative to the above quantities, we apply them to the investigation of some features of the neutron spectrum in UO₂ and MOX fuel. We deduce some relationships between the properties of the medium and the neutron spectrum, such as the independence of the neutron spectrum from the fission cross section and the neutron multiplicity. We show also in which extent these conclusions can be applied to real reactors.     

A spatial rehomogenization method in nodal calculations

Infinite medium flux weighted cross-sections used in nodal calculations enable equivalence with the corresponding fine configuration if the following condition is satisfied: the flux shape inside the assembly in the core is close to the infinite medium flux shape (computed in lattice calculations). In presence of big flux gradients this condition is not satisfied and the absence of information about cross-sections distributions inside a node does not permit to predict the reaction rates with the same accuracy attained in ordinary situations. This tendency is amplified in case of high heterogeneous regions where tilting the flux causes big changes in reaction rates. The method presented here uses information coming from the lattice calculations that produced the homogenized cross-sections, in order to predict the right reaction rate even in presence of high tilted flux shapes. This is done in evaluating a variation of the cross-sections equivalent to the variation in reaction rate, but no variation is applied to the discontinuity factors. The accuracy of the method and its limitations are shown in several significant configurations. Its implementation in the Areva NP reactor core simulation system SCIENCE has shown better evaluation of control rod worth in comparisons with experimental results.     

Estimation of Quantum Channels with Finite Resources

We examine the problem of determining the parameters that describe a quantum channel. It is assumed that the users of the channel have at best only partial knowledge of it and make use of a finite amount of resources to estimate it. We discuss simple protocols for the estimation of the parameters of several classes of channels that are studied in the current literature. A quantitative measures of the quality of the estimation schemes can be given on the basis of the standard deviation or of the fidelity. Protocols that employ entangled particles are also discussed. The use of entangled particles as a nonclassical resource enhances the estimation quality of some classes of quantum channel. Further, the methods presented here can be extended to higher dimensional quantum systems. PACS: 03.67.Hk     

Identification and quantification of prostaglandin E3 in renal medullary tissue of three strains of rats fed fish oil

Three strains of rats were fed a fish oil diet to verify their ability to incorporate and convert dietary eicosapentaenoic acid (20∶5ω3) into trienoic prostaglandins. Our results show that such conversion indeed occurs in kidney medullae homogenates. Specifically, the presence of prostaglandin E₃ (PGE₃) was established by gas chromatographic-mass spectrometric (GC-MS) analysis. That compound was conclusively identified by comparison of fragment ions and their relative intensities with those obtained from authentic PGE₃. Further evidence was provided by studying the recovery of exogenously added PGE₃. The crude ethyl acetate extracts of the medullary homogenates were methylated and cleaned up by liquid-gel chromatography with Lipidex-5000 prior to conversion to PGB₃ for GC-MS analysis. The PGE₃ was quantified by selected ion monitoring (SIM) with [3,3,4,4-²H₄PGE₂ as internal standard. The levels of PGE₃ were similar, about 3 ng/mg of wet tissue, in the 3 strains of rats. Identical in vivo conversion of the 20∶5ω3 fatty acid to PGE₃ could not be positively established by analysis of pooled urine specimens.     

A new ionic conductor from AgI and Ag2O.B2O3

A room temperature conductivity maximum was recognized in the system AgI:Ag₂O.B₂O₃ at 78.8 mole% AgI, the mobile species being silver ions.X-rays diffraction and DTA showed the glass-like nature of this material which maintains its good electrochemical performances in the temperature range 25–230°. The discharge behaviour of solid state galvanic cells containing this material is close to that obtained from 4AgI:Ag₂WO₄.     

IEN-CsF1 accuracy evaluation and two-way frequency comparison

In this paper we report the accuracy evaluation of the Italian primary frequency standard IEN-CsF1. We discuss the shifts the frequency standard is corrected for and the procedure used for the accuracy evaluation. In the last section we report frequency comparisons of our fountain with those of remote laboratories and with International Atomic Time.