Based on recent scientific-technical developments referring to the transformation and biodegradation mechanisms of plastic compounds, progress has been made both in the conceptualization of relevant ...definitions and in the development of technical standards that allow determining, in a more precise and reproducible way, the ratio of biodegradability of a determined material. From these advances, they have developed, furthermore, the so-called oxo-biodegradable plastics, in which pro-oxidant additives are added to the raw polymer in such a way that allow a optimal abiotic transformation process (photo/thermo oxidation), producing the fragmentation of the material under suitable conditions for its simultaneous or successive biotic degradation (enzymatic oxidation). Although, currently, oxobiodegradable plastics are widely used in different applications such as, for example, in agriculture andsingle-use plastics, until very recently a technical standard was developed that allows determining the relative degradation ratio of different types of plastics under abiotic and biotic conditions. This process implies that for producers to be able to use specific terms of bio-degradation and oxo-biodegradation for advertising purposes that claim to offer an environmentally friendly product, the relevant entities must carry out metrological tests in light of the new definitions and technical standards. Furthermore, a large amount of specialized literature has been generated in which the bio-degradation ratio of oxobiodegradable plastics is determined in very specific environments and conditions. This review gives a detailed account of the different definitions and scientific concepts involved in oxo-/bio- degradation and shows how these concepts have evolved over time. It also shows the evolution of the technical standards, which, in general, are adapted to the new scientific and technical developments in the field of plastics. Finally, a detailed analysis of results reported in the scientific literature shows the dependence of oxo-biodegradation on different parameters (UV radiation, temperature, exposure time, type of enzymes), specific environments (soil, composting, waste, recycling, etc.), different types of plastics (LDPE, HDPE, LLDPE, pro-oxidant additives) and, finally, on different analytical techniques used (FTIR, DSC, TGA, SEM, tensile test).
Hydroxyapatite (HAp) is the most commonly used biomaterial in modern bone regeneration studies because of its chemical similarity to bone, biocompatibility with different polymers, osteoconductivity, ...low cost, and lack of immune response. However, to overcome the disadvantages of HAp, which include fragility and low mechanical strength, current studies typically focus on property modification through the addition of other materials. Objective. To develop and evaluate the biocompatibility of a HAp material extracted from eggshells and modified with silicon (Si) and poly(lactic-co-glycolic) acid (PLGA). Materials and Methods. An in vitro experimental study in which a HAp material prepared from eggshells was synthesized by wet chemical and conventional chemical precipitation. Subsequently, this material was reinforced with Si/PLGA using the freezing/lyophilization method, and then osteoblast cells were seeded on the experimental material (HAp/Si/PLGA). To analyse the biocompatibility of this composite material, scanning electron microscopy (SEM) and fluorescence confocal microscopy (FCM) techniques were used. PLGA, bovine bone/PLGA (BB/PLGA), and HAp/PLGA were used as controls. Results. A cellular viability of 96% was observed for the experimental HAp/Si/PLGA material as well as for the PLGA. The viability for the BB/PLGA material was 90%, and the viability for the HAp/PLGA was 86%. Cell adhesion was observed on the exterior surface of all materials. However, a continuous monolayer and the presence of filopodia were observed over both external and internal surface of the experimental materials. Conclusions. The HAp/Si/PLGA material is highly biocompatible with osteoblastic cells and can be considered promising for the construction of three-dimensional scaffolds for bone regeneration in dentistry.
Here, it is reported an enhancement of the light-extraction efficiency in organic light emitting diodes (OLEDs) by growing a colloidal crystal (CC) matrix inside the luminescent layer of single ...bottom-emitting heterostructures. The CC matrix is obtained by self-assembly of Silica (SiO2) spheres during the spin-coating procedure used for the deposition of the luminescent polymer Poly 2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene (MDMO-PPV). The SiO2 sphere diameter is estimated assuming a crystalline face-centered-cubic (fcc) structure and performing first principles calculations with the plane wave expansion method. The calculations provided a 250 nm sphere diameter for an adequate decoupling of the waveguide organic mode. From these considerations both, traditional bilayer and nanostructured OLEDs, were elaborated using ITO/PEDOT:PSS/MDMO-PPV/Ag and ITO/PEDOT:PSS/MDMO-PPV+Colloidal crystal/Ag architectures, respectively. The light-extraction efficiencies of both types of OLED architectures are quantified by measuring the wall plug efficiency. The results show a significant increase (near to 30%) on the average efficiency for nanostructured OLEDs. The improvement in the power efficiency is attributed to a reduction in the effective refractive index of the organic layer through the incorporation of a fcc-colloidal crystal into the emission layer (EML) of the OLED, which modifies their reflection properties. This novel method for obtaining CC in a single-step associated to the spin coating process has also the advantage of introducing the scattering medium directly into the EML in order to modify internal coupling modes, instead of focusing on substrate modification.
El pasado 7 de octubre de 2014 se anunció, por parte del correspondiente comité, que el premio Nobel de Física 2014 se les concedió a los japoneses Isamu Akasaki, Hiroshi Amano y Shuji Nakamura por ...la invención de los diodos emisores de luz (LED, por sus siglas en inglés) con emisión en la región verde-azul del espectro visible (Nakamura, Mukai & Senoh, 1991). La importancia de este invento está relacionada tanto con las potenciales aplicaciones de los LED azules como fuente de luz eficiente y ecológica, como en el desarrollo de los llamados sistemas cuánticos. Es así como actualmente el desarrollo de dispositivos electrónicos y opto-electrónicos, cuya región activa está constituida por estructuras cuánticas, está fuertemente modulado por la capacidad de fabricar dichas estructuras con una alta calidad cristalina, un alto control de la composición química y, sobre todo, con gran reproducibilidad. En este sentido, las técnicas de crecimiento epitaxial constituyen la piedra angular en el desarrollo tecnológico que supone la nano-electrónica. En este trabajo se plantean, en general, los diferentes procesos químicos y físicos que tienen lugar durante un crecimiento por Epitaxia de Capas Atómicas (Atomic Layer Epitaxy, ALE) de pozos cuánticos ultra-delgados (Ultra-Thin Quantum Wells, UTQW) de ZnXCd1-X.Se y se estudian, en particular, la cinética del proceso de adsorción de Zn dentro de la estructura cristalina en términos de una ecuación de reacción de primer orden que define la composición de la estructura en función de la temperatura del sustrato (Ts) y del flujo de átomos de zinc. Se obtienen los valores para la energía de activación, el factor pre-exponencial y la constante de adsorción de Zn. La composición química de los UTQW es uno de los parámetros más importantes para el diseño de estructuras cuánticas, ya que define la energía de emisión en potenciales aplicaciones opto-electrónicas y, en particular, en el desarrollo de LED azules y UV.
Abstract Studies regarding cytotoxic effects attributed to the use of adhesive bonding agents on pulp tissue are not conclusive. To point out whether these materials are safe for clinical use, in ...vivo exposure of dental pulp to adhesive bonding agents was simulated using an experimental setup in which Human Dental Pulp Stem Cells (hDPSC) are exposed to the action of two kinds of adhesives: self-etching adhesives and two-step bonding agents through a dentine barrier. Cytotoxic effects on these cells were evaluated by MTT assay protocol and fluorescence microscopy, and their results were contrasted to those obtained through Raman spectra taken on single hDPSCs. Overall, no significant cytotoxic effects were observed by combining all the techniques, and cell viability close to 90% was achieved for a dentine barrier of at least 1 mm thick. Moreover, Raman spectroscopy was able to detect structural DNA damage in some dental pulp cells when exposed to two-step bonding agents, suggesting that this technique could be considered a complementary tool with the potential to evaluate cell toxicity beyond cell viability.
Resumo Os estudos sobre os efeitos citotóxicos atribuídos ao uso de agentes de união adesivo no tecido pulpar não são conclusivos. Para determinar se esses materiais são seguros para uso clínico, a exposição in vivo da polpa dentária a agentes de união adesiva foi simulada por meio de uma configuração experimental na qual as células-tronco da polpa dentária humana (hDPSC) são expostas à ação de dois tipos de adesivos: adesivos autocondicionantes e agentes de união de duas etapas por meio de uma barreira de dentina. Os efeitos citotóxicos nessas células foram avaliados pelo protocolo de ensaio MTT e microscopia de fluorescência, e seus resultados foram contrastados com os obtidos por meio de espectros Raman obtidos em hDPSCs individuais. De modo geral, não foram observados efeitos citotóxicos significativos com a combinação de todas as técnicas, e a viabilidade celular próxima a 90% foi obtida para uma barreira de dentina de pelo menos 1 mm de espessura. Além disso, a espectroscopia Raman foi capaz de detectar danos estruturais ao DNA em algumas células da polpa dentária quando expostas a agentes de colagem de duas etapas, sugerindo que essa técnica poderia ser considerada uma ferramenta complementar com potencial para avaliar a toxicidade celular além da viabilidade celular.
The adsorption performance of a Cu-TiO 2 composite for removing acid blue 80 (AB80) dye from aqueous solutions was investigated in terms of kinetics, equilibrium, and thermodynamics. The effect of ...operating variables, such as solution pH, initial dye concentration, contact time, and temperature, on AB80 adsorption was studied in batch experiments. AB80 adsorption increased with increasing contact time, initial dye concentration, and temperature and with decreasing solution pH. Modeling of adsorption kinetics showed good agreement of experimental data with the pseudo-second-order kinetics model. The experimental equilibrium data for AB80 adsorption were evaluated for compliance with different two-parameter, three-parameter, and four-parameter isotherm models. The Langmuir isotherm model best described the AB80 adsorption equilibrium data. The thermodynamic data revealed that the AB80 adsorption process was endothermic and nonspontaneous. Kinetics, equilibrium, and thermodynamic results indicate that Cu-TiO 2 adsorbs AB80 by a chemical sorption reaction.
Abstract
OBJECTIVES
The relationship between operating time and postoperative morbidity has not been fully characterized in lung resection surgery. We aimed to determine the variables associated with ...prolonged operative times and their influence on postoperative complications after video-thoracoscopic lobectomy.
METHODS
Patients undergoing thoracoscopic lobectomy for lung cancer from December 2016 to March 2018, within the prospective registry of the Spanish Video-Assisted Thoracic Surgery Group were identified. Operating time was stratified by quartiles and complication rates analysed using chi-squared test. Primary outcomes included 30-day overall, pulmonary and cardiovascular complications and wound infection. Multivariable logistic regression analyses were performed to identify variables independently associated with operating time and their influence on the occurrence of postoperative complications.
RESULTS
Data of 1518 cases were examined. The median operating time was 174 min (interquartile range: 130–210 min). Overall morbidity rates significantly increased with surgical duration (20.5% vs 34.4% in the 1st and 4th quartiles, respectively, P < 0.05) and so did pulmonary complications (14.6% vs 26.4% in the 1st and 4th quartiles, respectively, P < 0.05). Differences were not found regarding cardiovascular and wound complications. After multivariable logistic regression analysis, operating time remained as an independent risk factor for overall (odds ratios, 2.05) and pulmonary complications (odds ratios, 2.01). Male sex, predicted postoperative diffusing capacity of the lung for carbon monoxide, number of lymphatic stations harvested, pleural adhesions, fissures completeness, lobectomy site, surgeon seniority, individual video-thoracoscopic surgeon experience and fissureless technique were identified as predictive factors for long operative time.
CONCLUSIONS
Prolonged operating time is associated with increased odds of postoperative complications. Modifiable factors contributing to prolonged operating time may serve as a target for quality improvement.
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