Sr-containing hydroxyapatite: morphologies of HA crystals and bioactivity on osteoblast cells

A series of Sr-substituted hydroxyapatites (HA), of general formula Ca_(10 ? x)Sr_x(PO₄)₆(OH)₂, where x = 2 and 4, were synthesized by solid state methods and characterized extensively. The reactivity of these materials in cell culture medium was evaluated, and the behavior towards MG-63 osteoblast cells (in terms of cytotoxicity and proliferation assays) was studied. Future in vivo studies will give further insights into the behavior of the materials.A paper by Lagergren et al. (1975), concerning Sr-substituted HA prepared by a solid state method, reports that the presence of Sr in the apatite composition strongly influences the apatite diffraction patterns. Zeglinsky et al. (2012) investigated Sr-substituted HA by ab initio methods and Rietveld analyses and reported changes in the HA unit cell volume and shape due to the Sr addition.To further clarify the role played by the addition of Sr on the physico-chemical properties of these materials we prepared Sr-substituted HA compositions by a solid state method, using different reagents, thermal treatments and a multi-technique approach. Our results indicated that the introduction of Sr at the levels considered here does influence the structure of HA. There is also evidence of a decrease in the crystallinity degree of the materials upon Sr addition. The introduction of increasing amounts of Sr into the HA composition causes a decrease in the specific surface area and an enrichment of Sr-apatite phase at the surface of the samples. Bioactivity tests show that the presence of Sr causes changes in particle size and/or morphology during soaking in MEM solution; on the contrary the morphology of pure HA does not change after 14 days of reaction. The presence of Sr, as Sr-substituted HA and SrCl_2, in cultures of human MG-63 osteoblasts did not produce any cytotoxic effect. In fact, Sr-substituted HA increased the proliferation of osteoblast cells and enhanced cell differentiation: Sr in HA has a positive effect on MG-63 cells. In contrast, Sr ions alone, at the concentrations released by Sr-HA (1.21–3.24 ppm), influenced neither cell proliferation nor differentiation. Thus the positive effects of Sr in Sr-HA materials are probably due to the co-action of other ions such as Ca and P.     

pH-triggered conduction of amine-functionalized single ZnO wire integrated on a customized nanogap electronic platform

The electrical conductance response of single ZnO microwire functionalized with amine-groups was tested upon an acid pH variation of a solution environment after integration on a customized gold electrode array chip. ZnO microwires were easily synthesized by hydrothermal route and chemically functionalized with aminopropyl groups. Single wires were deposited from the solution and then oriented through dielectrophoresis across eight nanogap gold electrodes on a platform single chip. Therefore, eight functionalized ZnO microwire-gold junctions were formed at the same time, and being integrated on an ad hoc electronic platform, they were ready for testing without any further treatment. Experimental and simulation studies confirmed the high pH-responsive behavior of the amine-modified ZnO-gold junctions, obtaining in a simple and reproducible way a ready-to-use device for pH detection in the acidic range. We also compared this performance to bare ZnO wires on the same electronic platform, showing the superiority in pH response of the amine-functionalized material.     

Functionalized polysiloxane coatings on hot‐rolled and high‐strength Fe 430 B steel: Analysis of mechanical response and resistance to chemicals

Hybrid organic‐inorganic coatings can be extremely beneficial to improve the performance of steel substrates as their outstanding adhesion strength, scratch resistance, and chemical endurance. However, the design and manufacture of the appropriate coating systems on the different metal alloys can be troublesome. Defective coatings can cause the deterioration of their performance, especially the resistance to aggressive chemicals. In this work, the deposition of functionalized methyl phenyl polysiloxane resins on hot rolled and high strength Fe 430 B steel substrates with and without an intermediate layer of a hybrid organic‐inorganic grafting polymer (vinyltriethoxysilane) is comparatively evaluated. Visual appearance, scratch and wear resistance of the coatings as well as their attitude to act as chemical proof barriers are investigated. Proper functionalization of methyl phenyl polysiloxane resins with hydroxyl and alkoxy groups can lead to coatings that are well adhered to the underlying substrates, thus exploiting all the performance they were designed for. In this case, the use of an organo‐silane interlayer can further increment the final properties of the overall coating systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40624.     

Ecological effects of aquaculture on living and non-living suspended fractions of the water column: a meta-analysis

The effects of aquaculture on the ecology of the water column have been extensively studied in the last two decades. However, to date, it has not been possible to extrapolate homogeneous information from the peer-reviewed literature. In the present study, 68 peer-reviewed articles were analysed and about 1087 study cases were used to test whether worldwide cultivations of aquatic organisms (shrimps, fish, bivalves and polyculture) have a differential effect on living and non-living fractions of the water column (suspended matter, chlorophyll-a, particulate organic carbon, nitrogen and phosphorus, bacteria and plankton). Meta-analysis feasibility depends on obtaining an estimate of the effect size from every study, and the most common measure of effect size (Hedges'd) is the difference between means of controls and impacts standardised by dividing by the pooled standard deviation. Shrimp, fish and bivalve cultivation differentially affected water column dynamics, with a general major impact on bacteria and phytoplankton. In addition, results showed that the water column dynamics are probably affected by organic aquaculture loading but, due to the substantial heterogeneity across studies, the information available on the effects can be considered partially flawed and therefore not sufficient to either support or exclude the notion that different forms of aquaculture affect ecological processes of the water column.     

Application of the Taguchi method to the analysis of the deposition step in microarray production

Every microarray experiment is affected by many possible sources of variability that may even corrupt biological evidence on analyzed sequences. We applied a “Taguchi method” strategy, based on the use of orthogonal arrays to optimize the deposition step of oligonucleotide sequences on glass slides. We chose three critical deposition parameters (humidity, surface, and buffer) at two levels each, in order to establish optimum settings. A$L_8$orthogonal array was used in order to monitor both the main effects and interactions on the deposition of a 25 mer oligonucleotide hybridized to its fluorescent-labeled complementary. Signal-background ratio and deposition homogeneity in terms of mean intensity and spot diameter were considered as significant outputs. An analysis of variance (ANOVA) was applied to raw data and to mean results for each slide and experimental run. Finally we calculated an overall evaluation coefficient to group together important outputs in one number. Environmental humidity and surface-buffer interaction were recognized as the most critical factors, for which a 50% humidity, associated to a chitosan-covered slide and a sodium phosphate$+$25% dimethyl sulfoxide (DMSO) buffer gave best performances. Our results also suggested that Taguchi methods can be efficiently applied in optimization of microarray procedures.     

Aluminum nitride grating couplers

Grating couplers in sputtered aluminum nitride, a piezoelectric material with low loss in the C band, are demonstrated. Gratings and a waveguide micromachined on a silicon wafer with 600 nm minimum feature size were defined in a single lithography step without partial etching. Silicon dioxide (SiO(2)) was used for cladding layers. Peak coupling efficiency of -6.6 dB and a 1 dB bandwidth of 60 nm have been measured. This demonstration of wire waveguides and wideband grating couplers in a material that also has piezoelectric and elasto-optic properties will enable new functions for integrated photonics and optomechanics.     

Oxidised carbon nanotubes as solution processable,high work function hole-extraction layers for organic solar cells

For efficient hole-extraction in solution processed organic solar cells the transparent indium-tin oxide (ITO) electrode is invariably pre-coated with a thin layer of the high work function conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate). Herein we show that thin films of partially oxidised multi-wall and single-wall carbon nanotubes are equally effective at facilitating hole-extraction in efficient (～2.7%) bulk-heterojunction organic solar cells based on poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C₆₁ butyric acid methyl ester (PCBM) blends. Crucially, in contrast to PEDOT:PSS, deposition is from aqueous solutions of low acidity (pH 6–7) ensuring compatibility with ITO and other emerging conducting oxides. Furthermore, thin oxidised carbon nanotube films offer greater transparency in the near-infrared as compared to PEDOT:PSS films of comparable thickness. The functionality of these nano-structured films is demonstrated in relatively large area devices (～0.35 cm²) and the performance rationalised based on measurements of the electronic structure and morphology.     

Mapping the research on aquaculture. A bibliometric analysis of aquaculture literature

Research on aquaculture is expanding along with the exceptional growth of the sector and has an important role in supporting even further the future developments of this relatively young food production industry. In this paper we examined the aquaculture literature using bibliometrics and computational semantics methods (latent semantic analysis, topic model and co-citation analysis) to identify the main themes and trends in research. We analysed bibliographic information and abstracts of 14,308 scientific articles on aquaculture recorded in Scopus. Both the latent semantic analysis and the topic model indicate that the broad themes of research on aquaculture are related to genetics and reproduction, growth and physiology, farming systems and environment, nutrition, water quality, and health. The topic model gives an estimate of the relevance of these research themes by single articles, authors, research institutions, species and time. With the co-citation analysis it was possible to identify more specific research fronts, which are attracting high number of co-citations by the scientific community. The largest research fronts are related to probiotics, benthic sediments, genomics, integrated aquaculture and water treatment. In terms of temporal evolution, some research fronts such as probiotics, genomics, sea-lice, and environmental impacts from cage aquaculture, are still expanding while others, such as mangroves and shrimp farming, benthic sediments, are gradually losing weight. While bibliometric methods do not necessarily provide a measure of output or impact of research activities, they proved useful for mapping a research area, identifying the relevance of themes in the scientific literature and understanding how research fronts evolve and interact. By using different methodological approaches the study is taking advantage of the strengths of each method in mapping the research on aquaculture and showing in the meantime possible limitations and some directions for further improvements.