Diesel engines for light-to-medium helicopters and airplanes (Editorial)

The purpose of this article is to investigate utilization of common-rail turbocharged diesel aero-engines as primary propulsion powerplant for light-to-medium helicopters and airplanes. This article summarizes the results of a larger study on possible implementation of novel aerospace propulsion systems utilizing aero-diesel powerplant with hybrid, power-assist, and super-power capabilities for powered aircraft. Thermodynamic cycles of gasoline, diesel and jet engines are compared. The power-density of the respective powerplant and of the total power-train with fuel storage was examined. The feasibility of hybrid and super-power assist was considered for aero-diesel powerplants. The safety, technical and environmental footprint of each system was evaluated. The findings of this article identify many technical, safety, and environmental advantages by using aero-diesel engines in light-to-medium aircraft. Diesel engines represent well proven technology. The main obstacle for widespread and faster application of aero-diesels in aviation/aeronautics is lengthy certification process by regulatory agencies and some minor remaining control, operational, and maintenance issues. Implications of aero-diesel engine utilization in aeronautical applications may result in enhanced performance characteristics and safety of flight while lowering operational costs. Additionally, diesel engines leave lower negative environmental footprint than the other traditional aerospace propulsion systems. This editorial does not reflect the views of the IJAAA or ERAU. This work was not peer reviewed

Revêtements de verres bioactifs et d'hydroxyapatite et leurs propriétés

Dans les dernières décennies, la recherche biomédicale est devenue de plus en plus important. En outre, le vieillissement progressif de la population, avec leurs troubles musculosquelettiques, est le moteur du développement de matériaux innovants pour les implants osseux. Bien que la production d'implants prothétiques est aujourd'hui une pratique éprouvée et bien établie, la recherche scientifique est en constante évolution dans le but d'améliorer la fiabilité et l'efficacité des prothèses disponibles, augmentant ainsi leur espérance de vie. Le but de ce travail est la production de revêtements de nouvelle génération pour les prothèses dont l'objectif est l'augmentation de l'adhérence entre les implants prothétiques et les tissus osseux. Pour la réalisation des revêtements des matériaux bioactifs ont été pris en considération, nommément matériel spéciaux qui provoquent une réponse biologique spécifique à leur interface. Les nouveaux revêtements ont été produits avec l'hydroxyapatite et/ou du bioverre, deux matériaux bioactifs qui sont capables de se lier avec les tissus osseux. En particulier, l'hydroxyapatite est un matériau céramique dont la composition et la structure sont très semblables à ceux de la fraction minérale des os. Les bioverre sont des verres spéciaux qui sont caractérisés par une bioactivité tres élevée. Malheureusement, l'utilisation d'hydroxyapatite et bioverre dans des applications structurelles est limitée par leurs propriétés mécaniques, notamment de leur fragilité. Pour résoudre ce problème, bioverres et hydroxyapatite peuvent être appliqués comme revêtements sur des prothèses métalliques; ainsi la capacité de se lier à les tissus osseux des matériaux bioactifs est combinée à les élevées propriétés mécaniques typiques des métaux. Le procédé de production actuellement le plus utilisé pour le revêtements bioactifs est la projection au plasma. Dans cette étude une récente évolution de cette technique a été utilisée: projection au plasma de suspension. La différence entre cette nouvelle technique et la projection au plasma classique réside dans les matières premières utilisées. En fait, le nouveau procédé utilise des suspensions au lieu de poudres sèches qui permet de traiter les particules sub-micrométriques ou nanométriques et donc d'obtenir des revêtements avec une microstructure très fine et contrôlée. Dans la première partie de ce travail des bioverres ayant des compositions différentes ont été étudiés afin de choisir le plus prometteur pour la production de revêtements. Plus précisément, une étude visant à comparer leur bioactivité in vitro en a été réalisée. Après, les paramètres de dépôt pour produire des revêtements de bioverre ont été optimisés. Les revêtements ont été caractérisées d'un point de vue microstructurale et mécanique; également, des tests préliminaire in vitro ont été réalisées afin d'évaluer la réactivité des revêtements dans les liquide physiologiques. Ensuite, une couche superficiel en bioverre a été appliqué sur des revêtements traditionnels d'hydroxyapatite pour augmenter leur bioactivité. Depuis cette couche a montré la capacité de promouvoir la réactivité in vitro des revêtements, l'étude a évolué avec la réalisation de systèmes composites qui ont été produits avec bioverres et hydroxyapatite. Par conséquent, des revêtements composites bioverre/hydroxyapatite ont été produites et analysées. Trois différentes microstructures ont été produits: revêtements composites conventionnels (les phases constitutives sont réparties de façon aléatoire d'une manière uniforme); revêtements bicouches (composée d'une couche d'hydroxyapatite et d'une couche de surface en bioverre); revêtements avec un gradient de composition (dans laquelle la composition varie graduellement à partir de l'hydroxyapatite pure, en contact avec le substrat métallique, jusqu'à bioverre pur, sur la surface extérieure). L'objectif de ces systèmes est de joindre l' élevé bioactivité du bioverre avec la stabilité de l'hydroxyapatite. Les échantillons ainsi obtenus ont été caractérisés, et le revêtement à gradient a été choisi pour une optimisation ultérieure. Des nouveaux revêtements à gradient ont été produites et analysées et, en particulier, la leur microstructure et les leur propriétés mécaniques ont été analysés avant et après les tests in vitro. De cette façon, la bioactivité et aussi la stabilité des échantillons ont été évalués.Over the last decades, biomedical research has acquired a growing importance. Moreover, the progressive population ageing, with related musculoskeletal disorders, is driving the development of innovative materials for bone implants. Though the production of prosthetic implants is nowadays a mature and well-established practice, the scientific research is constantly evolving with the aim of improving the reliability and effectiveness of the available prostheses, thus increasing their life expectancy. The purpose of the present study is the production of new-generation coatings to support the adhesion between prosthetic implants and bone tissues. Bioactive materials, which are ones that elicit a specific biological response at their interface, were selected as coating materials. The new coatings were produced with hydroxyapatite and/or bioactive glass, two bioactive materials which are able to bond to bone. In particular, hydroxyapatite is a ceramic material whose composition and structure are very similar to those of the mineral component of bones. Moreover hydroxyapatite is highly stable in biological environment. For these reasons, this ceramic is currently the most widely used bioactive material to produce coatings for orthopaedic implants. Bioactive glasses, instead, are special glasses which exhibit a great bioactivity. Unfortunately, the use of hydroxyapatite and bioactive glasses in structural applications is limited by their mechanical properties, in particular their brittleness. To solve this problem, hydroxyapatite and bioactive glasses can be successfully used as coatings on metal prostheses. In this way the bone-bonding ability of bioactive materials is combined with the high mechanical properties of metals. Plasma spray is an established technique to produce bioactive coatings. In this study, a recent evolution of this process has been used i.e. the suspension plasma spray. The main difference between the new technique and the conventional one resides in the feedstock materials. In fact, the new process uses suspensions instead of dry powders which makes it possible to process sub-micrometric or nanometric particles and therefore to obtain coatings with an extremely fine and controlled microstructure. In the first part of this work, bulk bioactive glasses with different compositions were studied in order to select the most promising one for the coatings production. Specifically, a study to compare their in vitro bioactivity was carried out. Following, the deposition parameters to produce bioactive glass coatings were optimized. The coatings were characterized from a microstructural and mechanical point of view; also preliminary in vitro tests were carried out to assess the reactivity in physiological media. Then, a bioactive glass topcoat was applied on traditional hydroxyapatite coatings to increase their bioactivity. Since the topcoat showed the ability to promote coatings in vitro reactivity, the study progressed with the realization of specific composite systems using the hydroxyapatite and bioactive glasses. Accordingly, composite bioactive glass/hydroxyapatite coatings were produced and analysed. Three different microstructures were produced: conventional composite coatings (the constituent phases were evenly and randomly distributed); bi-layer coatings (the coatings included a hydroxyapatite bond coat and a bioactive glass topcoat); functionally graded coatings (the composition gradually changed from pure hydroxyapatite, in contact with the metal substrate, to pure bioactive glass, on the working surface). The basic goal was to merge the high bioactivity of bioactive glasses with the stability of hydroxyapatite. On account of the results of an introductory characterization, the graded structure was selected for further optimizations. New graded coatings were produced and analysed; in particular, their microstructure and mechanical properties were investigated before and after in vitro tests. In this way, both the bioactivity and the stability of the coatings could be estimated.LIMOGES-BU Sciences (870852109) / SudocSudocFranceF

IL-17, IL-1β and TNF-α stimulate VEGF production by dedifferentiated chondrocytes

AbstractObjectiveTo verify the involvement of proinflammatory cytokines IL-17, IL-1β and tumor necrosis factor α (TNF-α) in cartilage vascularization by stimulating the production of vascular endothelial growth factor (VEGF) by chondrocytes isolated from patients with osteoarthritis (OA), in comparison with patients with rheumatoid arthritis (RA) and patients with femoral or humeral neck fracture (FP).DesignChondrocytes isolated from patients with OA were maintained in monolayer culture for several passages. Chondrocyte dedifferentiation was monitored by the synthesis of cathepsin B by these cells. Chondrocytes freshly isolated at each subculture (subcultures 1–3) were stimulated with IL-17, IL-1β or TNF-α. Supernatants were collected, immunoassayed for the production of VEGF and cathepsin B and assayed as the source of VEGF on the VEGF sensible ECV304 cell line. The cells were used to quantify intracellular cathepsin B enzymatic activity.ResultsIn differentiated conditions IL-1β and TNF-α, but not IL-17, can inhibit the spontaneous secretion of VEGF by human OA, RA and FP chondrocytes, and IL-17 can restore the decrease in VEGF secretion caused by TNF-α. IL-17, together with IL-1β and TNF-α, can enhance VEGF secretion to various extents by dedifferentiated OA chondrocytes. This change in effect with respect to primary culture was observable for all cytokines at the beginning of dedifferentiation, when the production of VEGF by chondrocytes had dramatically fallen and the cathepsin B synthesis had increased. The amount of VEGF induced by cytokines on dedifferentiated chondrocytes never reached the amount of VEGF produced by differentiated chondrocytes. VEGF produced by chondrocytes stimulated the ECV304 cell line proliferation.ConclusionsThese results indicate that dedifferentiated OA chondrocytes secrete VEGF after stimulation with proinflammatory cytokines. This event may be responsible for neovascularization found in OA cartilage

Bioactive glass coatings: a review

Bioactive glasses, discovered by Hench and co-workers at the end of the 1960s, are among the most promising biomaterials for bone repair and reconstruction, mainly thanks to their high bioactivity index. Unfortunately, due to their brittleness and relatively poor mechanical properties, their clinical applications are limited to non-load bearing implants. However, bioactive glasses can be successfully employed as coatings on bioinert metallic substrates, in order to combine high bioactivity with mechanical strength. After a brief introduction to the main properties of biomaterials and bioactive glasses, the present paper provides an overview of the different approaches and available techniques to realise bioactive glass coatings, with a particular emphasis on thermal spray, which is nowadays one of the most popular coating procedures

Long-term in vitro expansion of osteoarthritic human articular chondrocytes do not alter genetic stability: a microsatellite instability analysis.

In this study, we investigated genetic damage acquisition during in vitro culture of human osteoarthritic (OA) chondrocytes to evaluate their safety for use in regenerative medicine clinical applications. In particular, we have addressed the impact of long-term in vitro culture on simple sequence repeat stability, to evaluate the involvement of the mismatch repair system (MMR) in the accumulation of genetic damage. MMR, the main post-replicative correction pathway, has a fundamental role in maintaining genomic stability and can be monitored by assessing microsatellite instability (MSI). MMR activity has been reported to decrease with age not only in vivo, but also in vitro in relationship to culture passages. OA chondrocytes from seven donors were cultured corresponding to 13-29 population doublings. Aliquots of the cells were collected and analyzed for MSI at five DNA loci (CD4, VWA, FES, TPOX, and P53) and for MMR gene expression at each subculture. Genetic stability was confirmed throughout the culture period. MMR genes demonstrated a strong coordination at the transcriptional level among the different components; expression levels were very low, in accordance with the observed genetic stability. The reduced expression of MMR genes might underline no need for increasing DNA repair control in the culture conditions tested, in which no genetic damage was evidenced. These data argue for the safety of chondrocytes for cellular therapies and are encouraging for the potential use of in vitro expanded OA chondrocytes, supporting the extension of autologous cell therapy procedures to degenerative articular diseases

A new generation of scaffolds for bone tissue engineering

The design of bioceramic scaffolds, i.e. artificial structures employed as temporary templates for cell proliferation, is a crucial issue in bone tissue reconstruction and regeneration. An ideal scaffold should be highly porous and bioactive. Additionally, a resistant and permeable surface is required in order to have manageable samples. The production of scaffolds by means of the widely used replication method can lead to samples with weak and brittle surfaces and poor mechanical properties, therefore alternative preparation procedures are necessary. In this work a new protocol to realize bioceramic scaffolds is presented. The obtained samples have an original structure, characterized by an external resistant surface together with a highly porous internal network. The external surface, which behaves as a load-bearing structure for the entire scaffold, guarantees high permeability and manageability. Here the proposed protocol is briefly discussed, together with an overview on the structure of the realized samples. Finally, some preliminary data regarding the scaffolds in-vitro bioactivity are reporte

In vivo real time non invasive monitoring of brain penetration of chemicals with near-infrared spectroscopy: Concomitant PK/PD analysis

Background. Near-infrared spectroscopy (NIRS) is a non-invasive technique that monitors changes in oxygenation of haemoglobin. The absorption spectra of near-infrared light differ for the oxygenation–deoxygenation states of haemoglobin (oxygenate (HbO2) and deoxygenate (Hb), respectively) so that these two states can be directly monitored. Comparison with existing method(s). Different methodologies report different basal values of HbO2 and Hb absolute concentrations in brain. Here, we attempt to calculate basal HbO2 levels in rat CNS via evaluation of the influence of exogenous oxygen or exogenous carbon dioxide on the NIRS parameters measured in vivo. New method. Furthermore the possibility that changes of haemoglobin oxygenation in rat brain as measured by NIRS might be a useful index of brain penetration of chemical entities has been investigated. Different compounds from different chemical classes were selected on the basis of parallel ex vivo and in vivo pharmacokinetic (PK/PD) studies of brain penetration and overall pharmacokinetic profile. Results. It appeared that NIRS might contribute to assess brain penetration of chemical entities, i.e. significant changes in NIRS signals could be related to brain exposure, conversely the lack of significant changes in relevant NIRS parameters could be indicative of low brain exposure. Conclusions. This work is proposing a further innovation on NIRS preclinical applications i.e. a “chemical” NIRS [chNIRS] approach for determining penetration of drugs in animal brain. Therefore, chNIRS could became a non invasive methodology for studies on neurobiological processes and psychiatric diseases in preclinical but also a translational strategy from preclinical to clinical investigations