Molten hydroxide synthesis as an alternative to molten salt synthesis for producing K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>NbO<Subscript>3</Subscript> lead free ceramics

Lead-free piezoelectric materials have grown in importance through increased environmental concern and subsequent EU and worldwide legislation, with the aspiration to reduce the use of Pb-based materials in all sectors. Integration of the next generation of lead-free piezoelectric materials with substrates to form functional micro devices has received less attention. Low temperature synthesis methods for K_0.5Na_0.5NbO₃ (KNN) powder were developed to overcome the issue of poor purity of the final product during high temperature sintering. Molten hydroxide synthesis (MHS), derived from molten salt synthesis (MSS), has been developed to overcome a Na ion preference in the molten salt synthesis reaction that leads to NaNbO₃ production instead of KNN when stoichiometric amounts of precursors are used. MHS makes use of a KOH molten reaction aid in place of the NaCl/KCl molten salt mix of the MSS. In a two stage reaction K rich intermediate niobates are produced and subsequent reactions with Na species produce KNN.     

Growth of InAs/InAsSb heterostructured nanowires

We report the growth of InAs/InAs(1-x)Sb(x) single and double heterostructured nanowires by Au-assisted chemical beam epitaxy. The InAs(1-x)Sb(x) nanowire segments have been characterized in a wide range of antimony compositions. Significant lateral growth is observed at intermediate compositions (x ~ 0.5), and the nucleation and step-flow mechanism leading to this lateral growth has been identified and described. Additionally, CuPt ordering of the alloy has been observed with high resolution transmission electron microscopy, and it is correlated to the lateral growth process. We also show that it is possible to regrow InAs above the InAsSb alloy segment, at least up to an intermediate antimony composition. Such double heterostructures might find applications both as mid-infrared detectors and as building blocks of electronic devices taking advantage of the outstanding electronic and thermal properties of antimonide compound semiconductors.     

New PMMA-based composites for preparing spacer devices in prosthetic infections

Even though the systemic antibiotic therapy is usually applied after prosthetic infections surgical treatments, it is unable to reach the infection site in sufficient concentrations to eradicate bacteria. Delivering antibiotics locally with the use of custom made device (spacer or nail coating) might eradicate or reduce the infection and the risk of recolonization, providing a very high concentration of antibiotic. PMMA-based (Mendec Spine^®) composites with BaSO₄ were enriched with β-tricalcium phosphate (Porosectan-TCP) or only a slightly higher BaSO₄ concentration (Porosectan-BaSO₄) to obtain higher porosity. The aim of the study was to evaluate: (i) drug absorption capability and drug release kinetics in vitro soaking them with a combined solution of gentamicin and vancomycin, (ii) their in vitro and in vivo biocompatibility, and finally, (iii) they were tested preliminarily in an experimental model of bone infection. The simultaneous presence of β-TCP and BaSO₄ resulted in the formation of a texture of interconnecting channels with different diameters, from a few microns to several hundred microns, which totally filled the material. The porosity, determined by microcomputed tomography, was significantly higher in both tested plain composites (Porosectan-TCP: +17.3%; Porosectan-BaSO₄: +7.5%) in comparison to control composite material (Mendec Spine^®). The kinetics of antibiotic release from composites was rapid and complete, producing high drug concentrations for a short period of time. Both composites showed a good level of biocompatibility. The osteomyelitic model confirmed that both composites, soaked in antibiotic solution, were able to cure bone infection. These composites could be useful for preparing devices for prosthetic joint infections treatment also allowing the use of antibiotics solution at required concentrations.     

Scanning-PIXE analysis of gold lace embroideries in a relic of St. Francis

In this work, we describe the compositional analysis performed by scanning-mode PIXE on the metal threads of a XIII century embroidery. The precious work analysed is the pillow-case used to cover the pillow, on which - according to tradition - St. Francis of Assisi was resting his head when he died. Measurements were performed in order to characterise the embroideries of the two sides and the passementerie in the lateral hems. Several areas, each of the order of two square millimetres, were scanned with a 3 MeV proton external beam of 20 μm size on target, using the external micro-beam facility of our laboratory, with list-mode acquisition. Analysis of elemental maps and spectra from selected homogeneous sub-areas allowed us to extract the quantitative composition of the gilded tape and estimates of its thickness.     

Supercritical fluid extraction of bioactive lipids from the microalga Nannochloropsis sp.

Marine microalgae are recognised as an important renewable source of bioactive lipids with a high proportion of polyunsaturated fatty acids (PUFA), which have been shown to be effective in preventing or treating several diseases. For the extraction of oil from microalgae, supercritical CO₂ (ScCO₂) is regarded with interest, being safer than hexane and offering a negligible environmental impact, a short extraction time and a high‐quality final product. Whilst some experimental papers are available on the supercritical fluid extraction (SFE) of oil from microalgae, only limited information exists on the kinetics of the process. In such a contest, a mathematical model able to describe the kinetics of the SFE was applied to the recovery with ScCO₂ of lipids from Nannochloropsis sp., a marine microalga commonly used in aquaculture and characterised by a lipid fraction with a high PUFA content. The aim of this paper was to examine the effect of operating conditions on the kinetics of the SFE, on process yields and on the fatty acid composition of lipid extracts.     

Facile One‐Step Micropatterning Using Photodegradable Gelatin Hydrogels for Improved Cardiomyocyte Organization and Alignment

Hydrogels are often employed as temporary platforms for cell proliferation and tissue organization in vitro. Researchers have incorporated photodegradable (PD) moieties into synthetic polymeric hydrogels as a means of achieving spatiotemporal control over material properties. In this study protein‐based PD hydrogels composed of methacrylated gelatin and a crosslinker containing o‐nitrobenzyl ester groups are developed. The hydrogels are able to degrade rapidly and specifically in response to UV light and can be photopatterned to a variety of shapes and dimensions in a one‐step process. Micropatterned PD hydrogels are shown to improve cell distribution, alignment, and beating regularity of cultured neonatal rat cardiomyocytes. Overall this work introduces a new class of PD hydrogel based on natural and biofunctional polymers as cell culture substrates for improving cellular organization and function.     

Development and characterization of cellulose‐based hydrogels for use as dietary bulking agents

In the last decade, cellulose‐based hydrogels have been receiving increasing attention for a number of applications because of their smart swelling behavior, biodegradability, and biocompatibility. Given the dramatic spreading of obesity and overweight in the industrialized countries and the lack of scientific consensus over currently available dietary supplements, it was recently proposed that such hydrogels might be used as orally administered bulking agents in hypocaloric diets, because the hydrogel swelling in the stomach may greatly reduce the space available for food intake, thus giving a sense of fullness. This study is focused on the synthesis of cellulose‐based hydrogels, starting from pharmaceutical and food grade cellulose derivatives, and shows that such hydrogels possess good swelling properties in water solutions mimicking the environmental conditions of the stomach and the intestine, as well as a good biocompatibility. The crosslinking agent used was a “zero‐length” crosslinker, that is, a water soluble carbodiimide, which is washed out from the gel after the synthesis and does not affect the gel compatibility, as shown by preliminary biocompatibility assays. The experimental results confirmed that cellulose‐based hydrogels might be a scientifically valid dietary adjuvant in the treatment of obesity and overweight, and provide further scientific evidence for future experiments on humans. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A 147-dB dynamic range electronic attenuator for audiometricapplications with on-chip 1-W power amplifier

This paper presents an integrated circuit for audiometric applications, which includes a linearly controlled exponential attenuator with 147 dB of dynamic range and a power amplifier capable of driving 8 V_pp on a 7-Ω resistive load. The required attenuation is achieved in the current domain by exploiting the exponential transfer characteristic of bipolar transistors. In order to achieve a temperature-independent attenuation, in spite of the temperature-dependent bipolar transistor I_C-V_BE relationship, we produce on-chip an attenuation control voltage proportional to the absolute temperature. The 24-mm² chip, fabricated in a 2-μm high-voltage CMOS process, achieves the required dynamic range with 80 dB of spurious-free dynamic range (excluding harmonics) and -57 dB of total harmonic distortion, consuming 33 mA from a ±5-V power supply