Experimento de campo sobre la capacidad reproductiva de la almeja invasiva Mya arenaria en el estuario del rio Tajo: coexistencia con la almeja nativa Scrobicularia plana

A three month field experiment with tidal level (upper, middle, lower) and treatment (excavated and not excavated plots) as categorical experimental factors showed that the invasive clam Mya arenaria has reached a more advanced stage in the invasion process in the Tagus estuary. As we observed the smallest recruited juveniles of Mya arenaria (2 mm) throughout the study period, we concluded that the clam is capable of reproducing in the new habitat. Juveniles of both Mya arenaria and the bivalve Scrobicularia plana were found to avoid excavated experimental plots, showing a significantly higher abundance in the control plots. These data, strongly suggest that the recruited bivalves actively avoid unsuitable substrata. Juvenile specimens of Mya arenaria were more abundant in the mid-intertidal zone. However, juvenile specimens of Scrobicularia plana were mainly distributed in the upper intertidal level, which suggests that they have a different settlement behaviour from that observed for the juveniles of the invasive clam. Despite the divergent distribution between the juveniles of the two species in the study site, the possible interaction between these two species is considered and discussed.La almeja invasiva Mya arenaria ha alcanzado un nuevo estadio invasivo en el estuario del Río Tajo, de acuerdo con los resultados de un experimento de campo que transcurrió durante 3 meses y en el que fueron considerados los factores categóricos elevación intermareal (superior, intermedia e inferior) y tratamiento (unidades experimentales excavadas y no excavadas). La presencia continua durante el tiempo de estudio de juveniles del menor tamaño observado (2 mm) nos permitió deducir que la almeja invasiva es capaz de reproducirse en el nuevo hábitat. Individuos juveniles de Mya arenaria y Scrobicularia plana evitaron las unidades experimentales excavadas, siendo más abundantes en las unidades de control. Esta observación sugiere que los juveniles de ambas especies evitan activamente sustratos poco adecuados. Los juveniles de Mya arenaria se distribuyeron principalmente en la zona intermareal media. Sin embargo, los juveniles de Scrobicularia plana se concentraron principalmente en la región intermareal superior, lo que sugiere un comportamiento de fijación distinto al observado en la almeja invasiva. A pesar de la distribución divergente entre los juveniles, la probable interacción entre las dos especies es considerada y discutida

Distribución intermareal de las poblaciones de macroinvertebrados en el estuario del Tajo, Portugal, en relación con factores ambientales

Fourteen intertidal sites from the eastern mid-region of the Tagus estuary were considered in order to study their macrobenthic assemblages in relation to environmental factors. The salinity gradient was displayed in an ordination of the assemblages by non-metric multidimensional scaling (NMDS). However, salinity was not found to be a significant environmental factor to explain the distribution of the assemblages. Conversely, a lateral gradient characterized three clusters of sites identified in relation to their outer, intermediate and inner location also related to organic matter content, oxygen concentration and redox potential values. Although the hydrodynamic factor was not investigated it is thought to be an important environmental factor for characterizing the lateral gradient. As a general trend, there was a transition between the groups of assemblages from the lower estuary towards the inner and upstream locations. The polychaetes Lanice conchilega and Hediste diversicolor and the gastropod Hydrobia ulvae were the characteristic species in the outer, inner and intermediate groups of sites, respectively. It was concluded that the lateral gradient is the main environmental driver that explains the distribution of the intertidal macrobenthic assemblages in the Tagus estuary when the salinity gradient is not find to be a significant environmental factor.Se han estudiado las poblaciones de macroinvertebrados y su distribución en relación a varios factores ambientales en catorce estaciones de muestreo da la zona intermareal situadas en la región central, margen Este, del estuario del Río Tajo. El gradiente salino fue sobrepuesto sobre las poblaciones macrobentónicas tras aplicar un escalado multidimensional no métrico (NMDS). El análisis reveló que la salinidad no es un factor ambiental significativo en la distribución de las poblaciones macrobentónicas de la zona en estudio. En cambio, se identificó un gradiente lateral que caracterizó los grupos de estaciones de muestreo agrupadas según su localización exterior, interior e intermedia, igualmente relacionadas con los factores ambientales contenido de materia orgánica, concentración de oxígeno y potencial redox. Aunque no se ha medido el factor hidrodinámico, éste parece ser importante para la definición del gradiente lateral. De modo general se observó una transición gradual entre los grupos de poblaciones macrobentónicas desde los situados en la parte de mayor influencia marina hacia aquellos que se distribuyeron en zonas más alejadas del mar en sentido lateral o longitudinal. Los poliquetos Lanice conchilega y Hediste diversicolor y el gasterópodo Hydrobia ulvae fueron las especies características de los grupos de estaciones exterior, interior e intermedio respectivamente. Se ha concluido que el gradiente lateral es el principal condicionante ambiental que explica la distribución de las poblaciones de macroinvertebrados intermareales en el estuario del Río Tajo cuando el gradiente salino no es significativamente importante

Características del alpechín: modelos y análisis estadístico

A synthesis of the work carried out on Olive Mill Wastewater (OMW) characterisation is given, covering articles published over the last 50 years. Data on OMW characterisation found in the literature are summarised and correlations between them and with phenolic compounds content are sought. This permits the characteristics of an OMW to be estimated from one simple measurement: the phenolic compounds concentration. A model based on OMW characterisations accounting 6 countries was developed along with a model for Portuguese OMW. The statistical analysis of the correlations obtained indicates that Chemical Oxygen Demand of a given OMW is a second-degree polynomial function of its phenolic compounds concentration. Tests to evaluate the regressions significance were carried out, based on multivariable ANOVA analysis, on visual standardised residuals distribution and their means for confidence levels of 95 and 99 %, validating clearly these models. This modelling work will help in the future planning, operation and monitoring of an OMW treatment plant.Presentamos una síntesis de los trabajos realizados en los últimos 50 años relacionados con la caracterización del alpechín. Realizamos una recopilación de los datos publicados, buscando correlaciones entre los datos relativos al alpechín y los compuestos fenólicos. Esto permite la determinación de las características del alpechín a partir de una sola medida: La concentración de compuestos fenólicos. Proponemos dos modelos, uno basado en datos relativos a seis países y un segundo aplicado únicamente a Portugal. El análisis estadístico de las correlaciones obtenidas indica que la demanda química de oxígeno de un determinado alpechín es una función polinómica de segundo grado de su concentración de compuestos fenólicos. Se comprobó la significancia de esta correlación mediante la aplicación del análisis multivariable ANOVA, y además se evaluó la distribución de residuos y sus promedios a un nivel de fiabilidad del 95 y 99 %. Este trabajo ayudará al diseño futuro de plantas de tratamiento de alpechín, así como a su funcionamiento y control

Correlação entre o conteúdo inorgânico e a polimerização da matriz orgânica das resinas compostas para restaurações dentárias: uma revisão narrativa

Introduction: In recent years, resin-matrix composite materials have revealed a fast technological improvement for dental applications. However, there are still some drawbacks related to the chemical composition, polymerization, and mechanical properties of resin-matrix composites with consequences in long-term clinical success. Objective: This study aimed to perform a narrative review regarding the effects of inorganic fillers on the organic matrix polymerization of resin-matrix composites. Materials and Methods: A search was performed in PubMed using relevant related key terms related to the chemical composition, properties and polymerization of resin matrix composites. Relevant studies published between 2001 and 2021 were selected. Results: The studies included in the present research provided relevant information on the chemical composition and properties of resin composites and polymerization factors, including the time, wavelength mode, and equipment. Studies have reported that silica and silicate nano-scale particles improve light transmission through resin-matrix composites and the degree of conversion of monomers in the organic matrix. Micrometric particles with a high refractive index can decrease the degree of conversion of monomers in the organic matrix. Conclusion: The polymerization of resin-matrix composites is affected by light scattering due to the type of inorganic particles and the differences in refractive indexes of inorganic and organic contents.Introdução: Nos últimos anos, as resinas compostas têm sido melhoradas em termos tecnológicos, permitindo o alcance de melhores prognósticos na medicina dentária. Entretanto, subsistem algumas limitações relacionadas com a composição química e as propriedades das resinas compostas com consequências no sucesso clínico a longo prazo. Objetivo: O objetivo deste trabalho foi realizar uma revisão narrativa sobre a influência da componente inorgânica na polimerização da matriz orgânica das resinas compostas usadas para restauração dentária. Materiais e Métodos: A pesquisa foi realizada na plataforma PubMed utilizando termos de pesquisa relacionados com a composição química, propriedades e a polimerização das resinas compostas, para seleção de artigos relevantes ao tema. Resultados: Os estudos identificados reportam diferentes fatores relacionados com a polimerização incluindo modo, tempo, equipamento e a composição química das resinas compostas. Os estudos indicam que partículas nanométricas à base de sílica ou silicatos promovem uma maior transmissão de luz à matriz orgânica o que favorece a polimerização do material. Por outro lado, partículas micrométricas com um alto índice de refração podem diminuir o grau de conversão dos monómeros da matriz orgânica. Conclusão: A polimerização das resinas compostas é afetada pela dispersão da luz, devido ao tamanho das partículas inorgânicas e aos índices de refração da componente orgânica e inorgânica. De fato, um maior controlo da composição química e do tamanho de partículas inorgânicas aumenta o grau de polimerização das resinas compostas

Effect of inorganic fillers on the light transmission through traditional or flowable resin-matrix composites for restorative dentistry

Objectives The aim of this in vitro study was to evaluate the light transmission through five different resin-matrix composites regarding the inorganic filler content. Methods Resin-matrix composite disc-shaped specimens were prepared on glass molds. Three traditional resin-matrix composites contained inorganic fillers at 74, 80, and 89 wt. % while two flowable composites revealed 60 and 62.5 wt. % inorganic fillers. Light transmission through the resin-matrix composites was assessed using a spectrophotometer with an integrated monochromator before and after light curing for 10, 20, or 40s. Elastic modulus and nanohardness were evaluated through nanoindentation’s tests, while Vicker’s hardness was measured by micro-hardness assessment. Chemical analyses were performed by FTIR and EDS, while microstructural analysis was conducted by optical microscopy and scanning electron microscopy. Data were evaluated using two-way ANOVA and Tukey’s test (p < 0.05). Results After polymerization, optical transmittance increased for all specimens above 650-nm wavelength irradiation since higher light exposure time leads to increased light transmittance. At 20- or 40-s irradiation, similar light transmittance was recorded for resin composites with 60, 62, 74, or 78–80 wt. % inorganic fillers. The lowest light transmittance was recorded for a resin-matrix composite reinforced with 89 wt. % inorganic fillers. Thus, the size of inorganic fillers ranged from nano- up to micro-scale dimensions and the high content of micro-scale inorganic particles can change the light pathway and decrease the light transmittance through the materials. At 850-nm wavelength, the average ratio between polymerized and non-polymerized specimens increased by 1.6 times for the resin composite with 89 wt. % fillers, while the composites with 60 wt. % fillers revealed an increased ratio by 3.5 times higher than that recorded at 600-nm wavelength. High mean values of elastic modulus, nano-hardness, and micro-hardness were recorded for the resin-matrix composites with the highest inorganic content. Conclusions A high content of inorganic fillers at 89 wt.% decreased the light transmission through resin-matrix composites. However, certain types of fillers do not interfere on the light transmission, maintaining an optimal polymerization and the physical properties of the resin-matrix composites. Clinical significance The type and content of inorganic fillers in the chemical composition of resin-matrix composites do affect their polymerization mode. As a consequence, the clinical performance of resin-matrix composites can be compromised, leading to variable physical properties and degradation.Open access funding provided by FCT|FCCN (b-on). This work was supported by FCT (Portugal) in the subject of the following project: PTDC/EMEEME/4197/2021; by CAPES regarding the following projects: CAPES-PRINT/88881.310728/2018–01; and CAPESHUMBOLDT Program (grant number 88881.197684/2018–01). S.C. thanks FCT for her contract funding provided through 2020.00215. CEECIND

A preliminary analysis of the wear pathways of sliding contacts on temporomandibular joint total joint replacement prostheses

In the last years, several materials and design have been assessed in an attempt to improve the mechanical performance of temporomandibular joint total joint replacement (TMJ TJR) prostheses. However, the wear of the TMJ TJR condyle to the polymer-based fossa component during loading and sliding movements. That promotes the release of debris and risks of toxicity to the surrounding tissues. The purpose of this study was to perform a narrative literature review on the wear of TMJ TJR sliding contacts and potential toxicity of metallic debris to the patients. Previous studies reported a significant deterioration of the sliding contact surfaces of TMJ TJR prostheses. Material loss as a result of wear can cause a TMJ TJR condyle/fossa mismatch and the modification of the contact pressure and chewing loading. As a further consequence of wear, metal particles are released to the surrounding tissues with a high risk of local tissue and systemic toxicity through the bloodstream. The presence of particles induces the stimulation of inflammatory reactions depending on the concentration and size of debris. Thus, CoCr-based condyle release metallic ions and sub-micron particles that can be engulfed by macrophages or internalized by other tissue cells. The wear and material loss of TMJ TJR could be decreased by design optimization and novel materials with low friction and contact pressure. That consequently decrease the amount of metallic ions and particles to the surrounding tissues, preventing peri-prosthetic inflammatory reactions.This study was supported by FCT-Portugal (UID/EEA/04436/2013, NORTE-01-0145- FEDER-000018—HAMaBICo, POCI-01-0145-FEDER-031035_LaserMULTICER), SFRH/BPD/123769/ 2016 and CNPq-Brazil (CNPq/UNIVERSAL/421229/2018-7)

Transmitância ótica de resinas compostas na cimentação de restaurações indiretas - um estudo in vitro

[Excerto] Introdução A longevidade das restaurações indiretas adesivas depende, entre outros fatores, do tipo de material restaurador, da espessura do material restaurador, propriedades do cimento à base de resina e do procedimento de fotopolimerização1.[...