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Silicon nitride substrates have been diamond coated by hot-filament (home made) and microwave plasma (commercial) CVD reactors. The importance of Si3N4 as substrate relies on its favoured adhesion to the diamond film, as required in wear applications. Diamond coatings have been characterized by μ-Raman spectroscopy, X-ray diffraction, scanning electron microscopy and atomic force microscopy. The diamond film/substrate adhesion has been evaluated by performing Brale indentations at different loads. The diamond films grown by hot filament matched those grown by microwave plasma in terms of morphology and diamond quality, only loosing in uniformity. Spherical substrates have also been used to compare the films coated by both techniques.Se han depositado películas de diamante CVD sobre substratos de nitruro de silicio empleando un reactor experimental de filamento caliente y un reactor comercial que utiliza un plasma generado por microondas. La importancia del Si3N4 como substrato reside en que favorece una buena adhesión con el diamante para ser utilizado en aplicaciones de desgaste. Los recubrimientos obtenidos han sido caracterizados mediante espectroscopía μ-Raman, difracción de Rayos-X, microscopía electrónica de barrido y microscopía de fuerza atómica. El grado de adhesión entre la película y el substrato ha sido determinado realizando una serie de indentaciones con una punta Brale a diferentes cargas. Las películas depositadas mediante filamento caliente son similares, en términos de calidad del diamante y morfología, a las conseguidas con plasma inducido por microondas, aunque presentan problemas de uniformidad. Se han utilizado también substratos con geometría esférica para comparar los recubrimientos obtenidos por ambas técnicas.

The effect of several variables such as molar ratio P2O5/B2O3 (X), temperature and heating cycle on the strength of chemically bonded SiC materials for grinding wheels fabrication was studied. It was shown that the highest compressive strength (52.4 MPa) could be obtained using an optimal molar ratio X = 4.5 and a multiple step heating cycle up to a sintering temperature of 800oC. DTA, XRD, SEM and dilatometrical analysis were performed to follow the different stages of the structural development.Se estudia el efecto de diferentes variables tales como la razón molar P2O5/B2O3(X), temperatura y ciclo de calentamieno sobre la resistencia de materiales de SiC aglomerados quimicamente para la fabricación de muelas arasivas. Se ha comprobado que la más alta resistencia a la compresión (52,4MPa) pueda obtenerse usando una razón molar òptima x= 4,5 y un ciclo de calentamiento en múltiples etapas hasta la temperatura de 800º C. Estudios mediante ATD, DRX, MEB y análisis dilatométricos fueron llevados a cabo para seguir las diferentes etapas del desarrollo microestructura.

Metal/ceramic diffusion experiments are helpful to study bonding mechanisms or the effect of metal composition on the chemical wear of ceramic cutting tools. The reaction kinetics of Fe alloys/Si3 N4 ceramic diffusion couples was investigated in the temperature range 1050ºC-1250ºC, for 0.5h to 80h, under inert atmosphere. Optical microscopy, SEM and EPMA were carried out in cross sections of the reacted pairs. Si3N4 decomposes into Si and N that dissolve and diffuse through the metal. Both the diffusion zone on the metal side and the reaction zone on the ceramic side obey parabolic growth laws of time, with activation energies in the range Q=310-460kJmol-1. The amount of dissolved Si, the length of the diffusion zone and thus the reactivity of the ceramic increase as the alloy carbon content decreases. Due to Si accumulation, the α-Fe solid solution is stabilised at the reaction temperature and a steep decrease in the Si concentration is observed beyond the diffusion zone. The reinforcement of the Si3N4 composites with A12O3 platelets enhances the chemical resistance of the ceramic due to the inertness of this oxide and to the partial crystallisation of the intergranular phase. Other dispersoids such as HfN, BN and TiN do not improve the chemical resistance of the matrix by iron attack.Los experimentos de difusión metal/cerámica permiten estudiar mecanismos de unión y analizar el efecto de la composición del metal en el desgaste químico de herramientas de corte cerámicas. En este trabajo se investigó la cinética de reacción en pares de difusión aleaciones de Fe/Si3N4 a temperaturas entre 1050ºC-1250ºC, tiempos entre 0.5h a 80h, en atmósfera inerte. Las secciones transversales de los pares de difusión se analizaron mediante microscopía óptica, SEM y microsonda electrónica. El Si3N4 se descompone en Si y N que se disuelven y difunden en el metal. Tanto la zona de difusión en el metal como la zona de reacción en la cerámica obedecen una ley parabólica de crecimiento, con energías de activación de 310-460 KJ.mol-1. La cantidad de Si disuelto, el tamaño de la zona de difusión y, por lo tanto, la reactividad de la cerámica aumenta al diminuir el contenido de carbón de la aleación. Debido a la acumulación de Si, la solución sólida de α-Fe se estabiliza a la temperatura de reacción, y se observa un descenso significativo en la concentración de Si más allá de la zona de difusión. El reforzamiento del Si3N4 con plaquetas de Al2O3 aumenta la resistencia química del Si3N4 debido a la inercia de este oxido y a la cristalización parcial de la fase intergranular. La incorporación de HfN, BN y TiN no mejoran la resistencia química de la matriz al ataque por Fe.

The tribological behaviour of various Si3N4 based materials, including Si3N4/SiC composites, has been analysed from room temperature up to 700ºC, and for sliding speeds between 0.5 and 2 m/s. Materials have been prepared by hot pressing at 1750ºC in nitrogen atmosphere, varying α-Si3N4 phase content, microstructure coarseness and shape and size of the SiC particles. Wear tests were performed in self-mated pairs using a pin on disc tribometer, without lubrication and at a fixed load of 5 N. Pin and disc worn surfaces were observed by scanning electron microscopy (SEM-EDS). Debris generated during tests was analysed by SEM-EDS and X-ray diffraction (XRD). Results showed friction, f, and wear coefficients, K, above 0.3 y 10-6 mm3N-1m-1, respectively. Wear mechanism depended on the microstructure and the mechanical properties of the materials.Se ha analizado el comportamiento tribológico de materiales de Si3N4 y de compuestos Si3N4/SiC, desde temperatura ambiente hasta 700ºC y en el rango de velocidades 0.5-2 m/s. Los materiales se han preparado mediante prensado en caliente a 1750ºC en atmósfera de nitrógeno, variando el contenido en fase α-Si3N4, el tamaño medio de grano, y la morfología de las partículas de SiC adicionadas. Los ensayos se han realizado en pares homólogos utilizando un tribómetro del tipo punta sobre disco, sin lubricación y a una carga constante de 5 N. Las superficies de desgaste de las puntas y los discos se observaron en un microscopio electrónico de barrido con capacidad analítica (MEB-EDX). Los residuos generados durante los ensayos se analizaron mediante MEB-EDX y difracción de rayos X (DRX). Los resultados obtenidos en los ensayos daban valores de coeficiente de fricción, f, y de desgaste, K, superiores a 0.3 y 10-6 mm3N-1m-1, respectivamente. El mecanismo de desgaste predominante dependía de la microestructura y de las propiedades mecánicas del material ensayado.

Crystals of dipeptide α-L-aspartyl-L-alanine (α-Asp-Ala), C 7 H 12 N 2 O 5 , were studied under high-temperature conditions through vibrational spectroscopy (IR and Raman) and thermal analysis (Differential Scanning Calorimetry - DSC). From the analysis of the results, it is possible to conclude that: (i) the studied material undergoes a reversible order-disorder phase transition at 373 K on heating, where several changes were observed in the vibrational spectra, especially with vibrational modes of the units that participate directly of the hydrogen bonds; (ii) the phase transition undergone by the α-Asp-Ala crystal (about 373 K) involves changes in hydrogen bonds, possibly the rupture of at least one of them, and change in the conformation of the molecules in the unit cell., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Recent in vitro follicle culture (IVFC) studies in caprine have yielded lower maturation rates using late preantral follicles compared to early antral follicles. Thus, research focusing on developing stage-specific customized culture systems able to improve the efficiency of IVFC for late preantral follicles are warranted. This study aimed to compare the morphometric features, estradiol production, and gene expression between early antral caprine follicles produced in vitro and in vivo. In vitro-derived early antral follicles were produced after a 6-day in vitro culture of late preantral follicles, while in vivo-derived early antral follicles were yielded immediately after isolation from the ovaries; antral follicles were, thereafter, cultured for 18 days. In vitro-derived antral follicles were cultured either in a medium developed for preantral follicles (PF medium) or in a medium developed for antral follicles (AF medium). In vivo-derived early antral follicles, on the other hand, were cultured in AF medium (Control treatment). Results demonstrated that in vitro-derived antral follicles cultured in PF medium produced higher estradiol concentration, and m-RNA expression for matrix metalloproteinase-9 (MMP-9), and insulin receptor when compared to both in vitro- and in vivo-derived antral follicles cultured in AF medium. Remarkably, in vitro-derived antral follicles cultured in PF medium had similar MII and oocytes ≥110 μm rates compared with in vivo-derived antral follicles (Control treatment). In conclusion, when cultured in a single and appropriate medium (i.e., PF medium), in vitro-derived early antral follicles had comparable oocyte maturation rates to the in vivo-derived early antral follicles., Competing Interests: Declaration of competing interest The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of this work., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The aim of this study was to evaluate the effect of 1 μmol/L zearalenone (ZEN) and 1 μmol/L enterolactone (ENL), alone or in combination, on the survival and morphology of in vitro cultured ovarian preantral follicles. Ovaries from 10 sheep were collected at a local abattoir and fragmented, and the ovarian pieces were submitted to in vitro culture for 3 days in the presence or absence of the test compounds. The morphology of primordial and primary follicles was impaired by ZEN, whereas that of cultured secondary follicles was improved by ENL. However, the combination of ENL with ZEN impaired the quality of primary and secondary follicles. Both ZEN and ENL induced apoptosis, but only ZEN was responsible for oocyte autophagy. None of these xenoestrogens affected endoplasmic reticulum stress as observed by the unaltered expression of ERP29. Differently from ZEN, ENL increased the expression of the efflux transporter ABCG2. In conclusion, although ENL can counteract the negative effects of ZEN on primordial and primary follicles, this positive effect is not similar to that observed in ovarian tissue cultures in the presence of ENL alone., Competing Interests: Declaration of competing interest The authors declare no conflict of interest to disclose., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Public health concerns exist surrounding the epidemic of the Zika virus (ZIKV) and the rapid growth of transplantation in developing countries, including endemic zones of active arbovirus transmission, as well as travel to such regions by potential organ donors and recipients. Few data exist regarding the clinical characteristics of ZIKV infection in immunocompromised hosts. Laboratory screening protocols for transplantation to differentiate ZIKV infections from other endemic viral diseases and for the detection of possible donor-derived infection have not been stated. The diagnosis of ZIKV infection remains a challenge, fueled by the lack of standardized commercially available diagnostic tests and validated reference diagnostic laboratories, as well as the limited duration of ZIKV viremia. In this small series, ZIKV infection in renal and liver recipients presented without rash, conjunctivitis, or neurological symptoms, and with abnormal graft function, thrombocytopenia, and bacterial superinfection. We report the first case series of ZIKV infection in solid organ recipients, with a description of clinical and laboratory features and therapeutic management., (© Copyright 2016 The American Society of Transplantation and the American Society of Transplant Surgeons.)

The superior biotribological performance of nanocrystalline diamond (NCD) coatings grown by a chemical vapor deposition (CVD) method was already shown to demonstrate high wear resistance in ball on plate experiments under physiological liquid lubrication. However, tests with a close-to-real approach were missing and this constitutes the aim of the present work. Hip joint wear simulator tests were performed with cups and heads made of silicon nitride coated with NCD of ~10 μm in thickness. Five million testing cycles (Mc) were run, which represent nearly five years of hip joint implant activity in a patient. For the wear analysis, gravimetry, profilometry, scanning electron microscopy and Raman spectroscopy techniques were used. After 0.5 Mc of wear test, truncation of the protruded regions of the NCD film happened as a result of a fine-scale abrasive wear mechanism, evolving to extensive plateau regions and highly polished surface condition (Ra<10nm). Such surface modification took place without any catastrophic features as cracking, grain pullouts or delamination of the coatings. A steady state volumetric wear rate of 0.02 mm(3)/Mc, equivalent to a linear wear of 0.27 μm/Mc favorably compares with the best performance reported in the literature for the fourth generation alumina ceramic (0.05 mm(3)/Mc). Also, squeaking, quite common phenomenon in hard-on-hard systems, was absent in the present all-NCD system., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Bone complexity demands the engineering of new scaffolding solutions for its reconstructive surgery. Emerging bone grafts should offer not only mechanical support but also functional properties to explore innovative bone therapies. Following this, ceramic bone grafts of Glass/hydroxyapatite (HA) reinforced with conductive carbon nanotubes (CNTs) - CNT/Glass/HA - were prepared for bone electrotherapy purposes. Computer-aided 3D microstructural reconstructions and TEM analysis of CNT/Glass/HA composites provided details on the CNT 3D network and further correlation to their functional properties. CNTs are arranged as sub-micrometric sized ropes bridging homogenously distributed ellipsoid-shaped agglomerates. This arrangement yielded composites with a percolation threshold of pc=1.5vol.%. At 4.4vol.% of CNTs, thermal and electrical conductivities of 1.5W·m(-1)·K(-1) and 55S·m(-1), respectively, were obtained, matching relevant requisites in electrical stimulation protocols. While the former avoids bone damaging from Joule's heat generation, the latter might allow the confinement of external electrical fields through the conductive material if used for in vivo electrical stimulation. Moreover, the electrically conductive bone grafts have better mechanical properties than those of the natural cortical bone. Overall, these highly conductive materials with controlled size CNT agglomerates might accelerate bone bonding and maximize the delivery of electrical stimulation during electrotherapy practices., (© 2013.)

The cytotoxicity profile of nanocrystalline diamond (NCD) coatings on a Si(3)N(4) ceramic was investigated. This material is envisaged to have biomedical dental applications such as burrs and surgical instruments. Two fibroblast cell culture systems were used to address the cytotoxicity of NCD-coated samples: L929 cells (a mouse permanent cell line) and human gingival fibroblasts. Cell behavior was evaluated in terms of cell adhesion, cell viability/proliferation (mitochondrial function, MTT assay) and the pattern of cell growth. Fibroblast cell behavior on standard polystyrene culture plates was used as control, as Si(3)N(4) substrates have previously been shown to be biocompatible. NCD coatings provided a suitable surface for cell attachment, spreading and proliferation. Human gingival cells showed a homogeneous cytoplasm spreading, a flattened elongated morphology and a typical parallel alignment on confluent cultures. In comparison, L929 cells denoted a lower cytoplasm expansion, a heterogeneous spreading but a higher proliferation rate. For both cells, after few days, the NCD coating was completely covered with continuous cell layers. As compared to standard polystyrene culture plates, no deleterious or cytotoxic responses were observed with L929 and human fibroblast cell cultures, and in both a slight enhancement in cell proliferation was observed. In addition, the seeded NCD film allowed reproduction of the typical features of the two cell culture systems tested, further suggesting the lack of cytotoxicity of this coating.

Exogenous and endogenous neurotoxins may have poisoning effects on living organisms. Neurotoxic signs can result from human intoxication by substances present in natural ecosystems as pollutants, such as inorganic mercury, cadmium, manganese and lead, or by abnormal accumulation of endogenous compounds, as bilirubin. Dissociated primary nerve cell cultures are powerful models that can be used to evaluate the responses of target cells at the cellular and molecular levels to the deleterious effects of neurotoxic substances. Primary cultures of nerve cells are prepared from either fetal (neurons) or 2-day-old (macroglia and microglia) rat brains, cultured with specific media. Cells can then be used to evaluate the neurotoxic effects of a particular substance. By using cells with different days-in-culture it is possible to mimic and evaluate developmental-related modifications. These modifications can comprise morphological changes, cell death by necrosis (release of lactate dehydrogenase, LDH) and apoptosis (nuclear fragmentation), altered neurotransmission (impaired uptake or increased release of glutamate), neuroinflammation (enhanced cytokine production) and the generation of oxidative damage (formation of reactive oxygen species and disruption of glutathione metabolism). Here we describe the methods for nerve cell cultures, as well as some of the procedures that can be used to assess neuronal and glial cytotoxicity induced by different neurotoxins.

Background/aims: Unconjugated bilirubin (UCB) can be neurotoxic in jaundiced neonates and in patients with Crigler-Najjar syndrome. UCB toxicity may culminate in cell death, however, the occurrence of apoptosis has never been investigated. Ursodeoxycholic acid (UDCA) is a strong modulator of the apoptotic threshold in both hepatic and nonhepatic cells. The aims of this study were to determine whether apoptosis plays a role in neural cell death induced by UCB, and to investigate the ability of UDCA to prevent cell death., Methods: Cultured rat astrocytes were incubated with UCB (17 and 86 microM) plus albumin (5.7 and 28.7 microM) for 4-22 h. In addition, astrocytes and neurones were treated with either UCB, 50 microM UDCA, or their combination for 4 h. Cultures were scored for nonviable cells by trypan blue dye exclusion. Apoptosis was assessed by Hoechst staining and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling assay., Results: UCB induced a concentration- and time-dependent decrease in astrocyte viability. Apoptosis was 4- and 7-fold increased after 4 h exposure to 17 and 86 microM UCB, respectively (P < 0.01). UDCA reduced apoptosis to <7%, which represents a appoximately 60% protection (P < 0.01). Cholic acid was not protective, and chenodeoxyholic acid aggravated UCB toxicity (P < 0.05). Finally, neurones showed a 1.5-fold greater sensitivity than astrocytes to UCB, while UDCA was still protective., Conclusions: UCB is toxic to both astrocytes and neurones, causing cell death through an apoptotic process. Moreover, UDCA inhibits UCB-induced apoptosis in neural cells and this could not be mimicked by other bile acids.

Shortage of donor livers has led several liver transplant centres to widen their definition of liver donor suitability. We have assessed the function of liver grafts from "marginal" donors and attitudes to use of such organs. Over an 18-month period, livers used in 30 of 213 consecutive liver transplantations in Birmingham, UK, came from marginal donors (history of alcoholism, abnormal liver function test results, drug overdose that included paracetamol, advanced cardiovascular disease, sepsis, lengthy hypotension [systolic blood pressure < 80 mm Hg for > 1 h], high-dose inotropic drug use). 16 of these donors had been refused by other UK liver transplant centres, 11 on medical grounds. The controls were grafts retrieved from "good" donors (n = 183) during the same period. All 30 grafts showed satisfactory early function but had greater day 1 (p = 0.004) and peak serum aspartate aminotransferase (p = 0.0008) values than control grafts. Graft and patient survival at 1 year in the two groups was similar (72% vs 73% and 80% vs 82%, respectively). To assess attitudes to marginal donor livers, a questionnaire outlining the details of these 30 donors was sent to the 80 centres in the European Liver Transplant Group, and 60 replied. Median immediate refusal rate of the marginal donors was 7/30 (range 0-18) and median outright acceptance rate was only 11/30 (1-26). Larger centres were less selective, with a significantly lower refusal rate (p = 0.03). These results indicate that, because of existing liver donor criteria within Europe, usable donor livers are being unnecessarily refused on medical grounds.