Preparation of tubular alumina-based membranes incorporated with coal fly ash and application as support to ZSM-5 membranes

Synthetic membranes are increasingly used in different applications for the concentration, fractionation, and efficient purification of components present in solutions and mixtures of liquids or gases. Ceramic membranes have a large potential over the polymeric ones for applications at high temperature, pressure, and in aggressive environments. However, the preparation of ceramic membranes is expensive. The coal fly ash (CFA) is a burning coal byproduct with structural qualities, mainly composed of silica and alumina oxides, being an appropriate and inexpensive raw material for ceramic membrane addition. Thus, the main objective of this work is to prepare and characterize tubular alumina-based membranes incorporated with CFA, without additive and binder-free, using the centrifugal casting method. In addition, this work aims to use these ceramic membranes as support for the ZSM-5 zeolites prepared without using organic structure-directing agents for application in catalytic processes. The centrifugal casting method with high-speed mold rotation has produced asymmetric membranes with different morphologies at the inner and outer surfaces of the tubes. High CFA fraction in the membranes resulted in higher porosity levels and water permeability, accompanied by a decrease in mechanical strength and in linear shrinkage. Moreover, the observed permeate flux was in the range between 116 and 370 L m-2 h-1 bar-1, and the retention for the cornstarch solution was above 99 % for all the membranes. To test the zeolitic deposition on these tubes, the synthesis of the ZSM-5 zeolite was performed with a theoretical Si/Al ratio of 50. The ZSM-5 zeolite membranes could be successfully synthesized on the tubes using the seeding method followed by the direct hydrothermal synthesis. The prepared materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy and tested for The prepared materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy and tested for separation of organic compounds and xylene isomerization reaction. The ceramic membranes CFA-based showed potential application for wastewater treatment and can be used as support to selective layer coatings as the ZSM-5 zeolite.Les membranes synthétiques sont de plus en plus utilisées dans différentes applications pour la concentration, le fractionnement et la purification efficaces des composants présents dans les solutions, ainsi que dans les mélanges de liquides ou de gaz. Les membranes céramiques ont un grand potentiel par rapport aux membranes polymères pour des applications à haute température, à haute pression et dans des environnements agressifs. Cependant, la préparation des membranes céramiques est coûteuse. La cendre volante de charbon (CFA, de l'anglais coal fly ash) est un sous-produit de la combustion du charbon dont les qualités structurelles, principalement composées d'oxydes de silice et d'alumine, sont une matière première appropriée et peu coûteuse qui peut être ajoutée à des membranes céramiques. Ainsi, l'objectif principal de ce travail est de préparer et de caractériser des membranes tubulaires à base d'alumine incorporées avec la CFA, sans additif et sans liant, en utilisant la méthode de coulée centrifuge. En outre, ce travail vise à utiliser ces membranes céramiques comme support pour les zéolithes ZSM-5 préparées sans utiliser d'agents organiques directeurs de structure pour les procédés catalytiques. La méthode de coulée par centrifugation avec rotation du moule à grande vitesse a produit des membranes asymétriques de morphologies différentes sur les surfaces intérieures et extérieures des tubes. La fraction élevée de CFA dans les membranes a entraîné des niveaux de porosité et une perméabilité à l'eau plus élevée, accompagnés d'une diminution de la résistance mécanique et du retrait linéaire. De plus, le flux de perméat observé était compris entre 116 et 370 L m-2 h-1 bar-1, et la rétention pour la solution d'amidon de maïs était supérieure à 99 % pour toutes les membranes. CPour tester le dépôt zéolitique sur ces tubes, la synthèse de la zéolite ZSM-5 a été réalisée avec un rapport théorique Si/Al de 50. Les membranes de la zéolite ZSM- 5 ont pu être synthétisées avec succès sur les tubes en utilisant la méthode d'ensemencement suivie de la synthèse hydrothermale directe. Les matériaux préparés ont été caractérisés par la diffraction des rayons-X, la spectroscopie infrarouge à transformée de Fourier et la microscopie électronique à balayage et ils ont été testés pour la séparation des composés organiques et la réaction d'isomérisation du xylène. Les membranes céramiques à base de CFA ont montré une application potentielle pour le traitement des eaux usées et peuvent être utilisées comme support pour le dépôt des couches de catalyseur comme la zéolite ZSM-5

Review and new methodological approaches in human-caused wildfire modeling and ecological vulnerability: Risk modeling at mainland Spain

En las últimas décadas, las autoridades en materia de incendios han fomentado la investigación acerca de los factores desencadenantes del fuego, parámetro decisivo para lograr un entendimiento mayor de los patrones de la ocurrencia de incendios y mejorar las medidas preventivas. Existe por tanto una necesidad de mejorar y actualizar los enfoques metodológicos para el modelado de incendios forestales, teniendo en cuenta no sólo algoritmos innovadores, sino también la mejora y/o superación de los métodos clásicos de regresión. Por otra parte, es también imprescindible fomentar la evaluación de los posibles daños potenciales en los ecosistemas naturales, promoviendo así la conservación de los servicios de valor económico, ambiental, cultural y estético que éstos proporcionan a la sociedad. El objetivo principal de esta tesis doctoral es explorar nuevos métodos para el modelado de la causalidad humana en incendios forestales así como de los efectos adversos sobre las comunidades vegetales potencialmente afectadas. El modelado de la causalidad humana se ha realizado a partir de métodos de aprendizaje artificial y de técnicas de regresión geográficamente ponderada. Estas técnicas permiten por una parte el ajuste de modelos de probabilidad de ocurrencia espacialmente explícitos y, por otra, el estudio de la variabilidad espacial de los factores explicativos. La estimación de la vulnerabilidad de la vegetación frente al fuego, se ha llevado a cabo utilizando un enfoque cuantitativo, que permita superar los métodos existentes, que, si bien pueden ser útiles en algunas áreas de la gestión del territorio, son inadecuados para otros tipos de análisis, tales como la estimación de las pérdidas económicas inducidas por el fuego como consecuencia de la interrupción de los servicios ambientales (por ejemplo, la madera, la caza, y la recolección de setas). Para abordar el análisis de la vulnerabilidad se propone un método basado en la estimación del tiempo de recuperación de las comunidades vegetales tras el fuego, desarrollado mediante álgebra de mapas en entorno SIG. Los resultados indican que la utilización de métodos de aprendizaje artificial (concretamente el algoritmo Random Forest) supone una mejora sustancial respecto a los métodos clásicos de regresión, si bien parece que existe cierta incertidumbre en los modelos desarrollados, relacionada principalmente con la calidad de los datos de ocurrencia. Además, la aplicación de modelos GWR ha revelado la existencia de una elevada heterogeneidad espacial en la relación y capacidad explicativa de los factores relacionados con la ocurrencia de incendios con origen antrópico. Por otra parte, la aplicación del modelo propuesto para la estimación cuantitativa de la vulnerabilidad ecológica sugiere que la capacidad de respuesta de la vegetación se encuentra estrechamente relacionada con la estrategia reproductiva de las especies afectadas.Over the last decades, authorities responsible on forest fire have encouraged research on fire triggering factors, recognizing this as a critical point to achieve a greater understanding of fire occurrence patterns and improve preventive measures. There is therefore a need to improve and update the methodological approaches for modeling forest fires, taking into account not only innovative algorithms, but also improving and/or overcoming classical regression methods. On the other hand it is also essential to encourage the assessment of potential damage on natural ecosystems, promoting the conservation of its economic, environmental, cultural and aesthetic assets they provide to society. The main objective of this PhD thesis is to explore new methods for modeling human causality in forest fires and adverse effects on the plant communities potentially affected. Human causality modeling was carried out from machine learning methods and geographically weighted regression techniques. These procedures allow the adjustment spatially explicit probability models of occurrence and, secondly, the study of the spatial variability of wildfire explanatory factors. The estimation of the vulnerability of vegetation to fire was carried out using a quantitative approach to overcome current methods, which, while they may be useful in some areas of land management, are inadequate for other types of analysis, such as estimating economic losses induced by interrupting ecosystem services (e.g., wood, hunting, and gathering mushrooms). To address the vulnerability a method based on evaluating the recovery time of plant communities after the fire using a GIS map algebra approach is proposed. The results suggest that the use of machine learning methods (specifically the Random Forest algorithm) represents a substantial improvement over traditional methods of regression, although it appears that there is some uncertainty in the models, primarily related to the quality of ignition. Furthermore, the application of GWR models has revealed the existence of a high spatial heterogeneity in the relationship and explanatory power of the factors related to the occurrence of anthropogenic fires. Moreover, the application of the proposed model for the quantitative estimation of ecological vulnerability suggests that the responsiveness of vegetation is closely related to the reproductive strategy of the fire-affected species

Sclerosing encapsulating peritonitis: a case successfully treated with immunosuppression.

Perit Dial Int. 1999 Sep-Oct;19(5):478-81. Sclerosing encapsulating peritonitis: a case successfully treated with immunosuppression. Martins LS, Rodrigues AS, Cabrita AN, Guimaraes S. SourceDepartment of Nephrology, Hospital de Santo António, Porto, Portugal

How do insolvency codes affect a firm’s investment?

[EN] This paper provides an ex ante analysis of the effect of financial insolvency codes on investment by examining the main characteristics embodied in several codes that may cause investment distortions. The results from the estimation of an extended version of the q model of investment show a negative relationship between ex ante insolvency costs and investment. Furthermore, most of the analysed characteristics of insolvency codes negatively impact on investment; however, the magnitude of this effect is greater concerning those of reorganization without creditors’ consent and creditors’ lack of control, as compared to those of automatic stay and the violation of absolute priority

How does Financial Distress Affect Small Firms’ Financial Structure?

[EN] This paper provides new evidence on the financial structure of small firms by emphasizing the role played by financial distress. We specify a model of debt adjustments that allows us to investigate the specific nature of the adjustment process towards target debt levels in small firms, which is then extended to account for the effect of financial distress on financial structure decisions. Our models were estimated by the Generalized Method of Moments on a data panel of small Portuguese firms during a period of recession, in which a substantial proportion of the companies analyzed faced a financial distress situation. We find that small firms do adjust their debt ratios towards target levels, the speed of adjustment being faster in the shorter term. Our results also indicate that there are major differences in the determinants of long-term and short-term debt, highlighting the role played by debt maturity in explaining a firm’s financial structure. Finally, random behavior is observed in financially distressed firms, who seem to be disoriented when making their financial structure decisions

Estimating financial distress likelihood

[EN] This study develops an ex-ante model for estimating financial distress likelihood (FDL), and contributes to the literature by presenting a financially-based definition of distress that is independent of its legal consequences, a theoretically supported model for the FDL, and an appropriate methodology that uses panel data to eliminate the unobservable heterogeneity. The model is then estimated cross-sectionally to obtain an indicator of the likelihood of financial distress that incorporates the specificity of each company. In doing so, this study provides a well-specified model that is stable in terms of magnitude, sign and significance of the coefficients and, more importantly, that yields a measure of the FDL that is more robust to time and the international context than the estimates of FDL that are based on seminal models. This measure could be appropriate for use in future research that deals with FDL, such as capital structure and the prevention of financial distress

Simplest relationship between local field potential and intracellular signals in layered neural tissue.

The relationship between the extracellularly measured electric field potential resulting from synaptic activity in an ensemble of neurons and intracellular signals in these neurons is an important but still open question. Based on a model neuron with a cylindrical dendrite and lumped soma, we derive a formula that substantiates a proportionality between the local field potential and the total somatic transmembrane current that emerges from the difference between the somatic and dendritic membrane potentials. The formula is tested by intra- and extracellular recordings of evoked synaptic responses in hippocampal slices. Additionally, the contribution of different membrane currents to the field potential is demonstrated in a two-population mean-field model. Our formalism, which allows for a simple estimation of unknown dendritic currents directly from somatic measurements, provides an interpretation of the local field potential in terms of intracellularly measurable synaptic signals. It is also applicable to the study of cortical activity using two-compartment neuronal population models

Anatomia da artéria pudenda superficial externa: estudo quantitativo

The importance of the superficial external pudendal artery in cases of lower limb obstructive arteriopathies has been established, and a perfect knowledge of its anatomy is desirable for the creation of successful flaps involving it. However, little information is available on the morphometry of this artery. PURPOSE: In this study, we conducted a quantitative investigation of the superficial external pudendal artery as the basis for skin grafts. METHOD: Twenty-five right and left sides of the inguinal region of male cadavers were dissected. After retracting the skin at the inguinal region, the femoral vessels and the sapheno-femoral junction were exposed. The following aspects were then analyzed: 1) the presence of the superficial external pudendal artery, 2) the place of origin of the superficial external pudendal artery and the common trunk, 3) the duplication of the superficial external pudendal artery, 4) the distance from the superficial external pudendal artery or the common trunk to the inguinal ligament, and 5) the diameter of the superficial external pudendal artery. RESULTS: The results were the following: 1) superficial external pudendal arteries were found in 46 of 50 sides (92%); 2) they originated from the femoral artery in 45 cases and from the deep femoral artery in only 1 case; 3) the arteries were found duplicated in 21 cases (46%), as a common trunk in 11 cases (24%), and as a single artery in 14 cases (30%); 4) the distance from the superficial external pudendal artery to the inguinal ligament ranged from 0.8 cm to 8.5 cm; from the common trunk, it ranged from 3.5 cm to 6.7 cm; 5) the diameter of the superficial external pudendal artery ranged from 1.2 mm to 3.8 mm; and 6) the diameter of the common trunk ranged from 1.35 mm to 5.15 mm. CONCLUSION: The results show that the superficial external pudendal artery generally originates from the femoral artery. It was found as a common trunk, duplicated, or as a single artery. There was a great variability in both the diameter of the artery and the distance from the artery to the inguinal ligament. Most of the data showed no significant differences between the right and the left sides.A importância do conhecimento da anatomia da artéria pudenda superficial externa está bem estabelecida e um conhecimento adequado de sua anatomia é desejável para a criação bem sucedida de flaps. Entretanto, são escassos os trabalhos morfométricos sobre esta artéria. OBJETIVO. No presente estudo, foi feita uma análise quantitativa da artéria pudenda superficial externa, como base para enxertos de pele. MÉTODO. Foram dissecadas 25 regiões inguinais direitas e 25 esquerdas de cadáveres do sexo masculino. Após rebater a pele da região inguinal, os vasos femorais, a junção safeno-femoral e a artéria pudenda superficial externa foram expostas. Os seguintes aspectos foram então analisados: 1. Presença da artéria pudenda superficial externa; 2. Local de origem da artéria pudenda superficial externa ou do tronco comum; 3. Duplicação da artéria pudenda superficial externa; 4. Distância da artéria pudenda superficial externa ou do tronco comum ao ligamento inguinal; 5. Diâmetro da artéria pudenda superficial externa. RESULTADOS. Os resultados mostraram que: 1. A artéria pudenda superficial externa foi encontrada em 46 dos 50 lados dissecados (92%); 2. A artéria teve origem na artéria femoral em 45 casos; em um único caso teve origem na artéria femoral profunda; 3. A artéria foi encontrada duplicada, em 21 casos (46%), formando um tronco comum, que depois se bifurcava, em 11 casos (24%) e como uma artéria única 14 vezes (30%); 4. A distância da artéria ao ligamento inguinal variou de 0,8 cm a 8,5 cm; quando sob a forma de tronco comum, esta distância variou de 3,5 cm a 6,7 cm; 5. O diâmetro da artéria pudenda superficial externa variou de 1,36 mm a 5,15 mm. CONCLUSÕES. Os resultados mostram que a artéria pudenda superficial externa origina-se, na grande maioria dos casos, da artéria femoral. Foi encontrada como um tronco comum, duplicada ou como uma artéria única. O diâmetro da artéria mostrou grande variabilidade assim como a distância da artéria ao ligamento inguinal. A maioria dos dados não mostrou diferença significante entre os lados direito e esquerdo

Characterizing pyroregions in mainland Spain from spatial-temporal patterns of fire regime and their underlying drivers

El fuego ha coexistido de forma intrínseca en diversos ecosistemas a nivel global. En el caso de los ambientes más humanizados la acción del hombre ha alterado esos regímenes de incendio naturales por uno fundamentalmente de carácter antrópico. En el contexto de la Europa Mediterránea, el número de incendios forestales y su área quemada observados han experimentado un descenso general durante el final del siglo XX. Esto ha supuesto un declive de la incidencia del fuego en la mayoría de los ecosistemas mediterráneos históricamente afectados por incendios recurrentes. Por tanto, es evidente la alteración de los regímenes de incendio pasados, debido principalmente a la intervención humana con una política de exclusión total del fuego muy exigente.No obstante, la evolución reciente de los regímenes de incendio presenta una alta variabilidad espacial y temporal. Por otro lado, las perspectivas de futuro vaticinan un impacto creciente del factor humano (abandono del campo, gestión de los bosques y mantenimiento de la supresión excluyente), lo que consecuentemente derivará una mayor actividad de incendios debido a una mayor cantidad de combustible disponible. Asimismo, se prevén unas condiciones climáticas cada vez más propensas a generar incendios de gran superficie (mayores valores de temperatura, mayor frecuencia de olas de calor y sequías), lo que sin duda afectará negativamente tanto a los ecosistemas como las sociedades futuras.Todos estos factores hacen necesaria una adecuada zonificación de los regímenes de incendio desde una perspectiva espacio-temporal, la cual permita conocer la relación existente entre el régimen de incendios alterado y los factores socio-económicos y ambientales asociados. Así como detectar tendencias en el tiempo en regiones que experimenten un descenso de la actividad, o, por el contrario, incremento de la incidencia de incendios. Por tanto, conociendo estas zonas se podrá mejorar la gestión y prevención contra incendios forestales.Esta tesis doctoral se enfoca en enriquecer el conocimiento sobre la identificación e interpretación de regiones homogéneas de regímenes de incendio. Para ello se recurre a un amplio abanico de métodos de análisis estadísticos y de modelado espacial. La tesis se estructura de acuerdo a los siguientes objetivos: el objetivo 1 se centra en analizar la distribución espacio-temporal de las principales métricas que definen el régimen de incendio durante el periodo reciente. El objetivo 2 pretende profundizar en la influencia del riesgo meteorológico en la evolución de la actividad de los incendios. El objetivo 3 evalúa el cambio de la contribución relativa de los factores antropogénicos en los incendios forestales. El objetivo 4 se enfoca en explicar la evolución y causas de los cambios o transiciones de los regímenes de incendios durante el periodo reciente (1974-2015) y futuro (2016-2036). Finalmente, el objetivo 5 pone la atención en la traslación de la zonificación de tipologías de regímenes de incendios hacia una cartografía integral de piroregiones.Los resultados indican que los regímenes de incendio en la España peninsular han experimentado diversos cambios, principalmente una disminución considerable de la actividad de incendios en la mayor parte del territorio, aunque todavía persiste una alta actividad en el extremo norte (especialmente en invierno). Los diversos métodos de aprendizaje automático empleados, especialmente Random Forest, han demostrado su potencial en términos de revelar los factores que impulsan la evolución del régimen de incendios. Además, la proyección ARIMA ha confirmado la tendencia actual hacia una menor incidencia de incendios. Todo apunta a que las medidas preventivas deben tomar más protagonismo en áreas con un abrupto descenso de la ocurrencia, ya que son significativamente más propensas a grandes incendios a corto y medio plazo.Fire has always been an intrinsic feature in various ecosystems around the world. In environments heavily populated by humans, their actions have altered these natural fire regimes for others that are fundamentally anthropogenic in nature. In the context of Mediterranean Europe, the number of forest fires and their observed burnt area fell into a general decline during the late twentieth century, which led to a reduced incidence of fire in most Mediterranean ecosystems historically affected by recurrent fires. Therefore, the change in past fire regimes is evident, mainly due to human intervention instigating a very demanding policy of total exclusion of fire. However, the recent evolution of fire regimes presents a high spatial and temporal variability. On the other hand, future scenarios predict a growing impact of the human factor (more land abandonment, poor management of forests and adhering exclusively to suppression methods), which will result in increased fire activity due to a greater amount of available fuel. In addition, climatic conditions are expected to cause increasingly larger burned areas (higher temperatures, more frequent heat waves and droughts), which will undoubtedly have a negative effect on both ecosystems and future societies. All these factors make an adequate zoning of fire regimes necessary from a spatial-temporal perspective, which allows the relationship between the altered fire regime and associated socio-economic and environmental factors to be determined, as well as detecting temporal trends in regions with decreasing activity, or on the contrary, an increase in the incidence of fires. Therefore, finding these areas will lead to improved management and prevention of forest fires. This doctoral thesis focuses on enriching knowledge for identifying and interpreting homogeneous regions of fire regimes. A wide range of methods of statistical analysis and spatial modeling are employed. The thesis is structured according to the following objectives: Objective 1 focuses on analyzing the spatial-temporal distribution of the main features defining the fire regime during the recent period. Objective 2 aims to further describe the influence of meteorological danger on the evolution of fire activity. Objective 3 evaluates the change in the relative contribution of anthropogenic factors on forest fires. Objective 4 focuses on explaining the evolution and causes of changes or transitions in fire regimes during the recent (1974-2015) and future (2016-2036) periods. Finally, Objective 5 centers on the transfer of the zoning of fire regime typologies into an integral mapping of pyroregions The results indicate that fire regimes in mainland Spain have undergone several changes, mainly a considerable decrease in fire activity in most of the territory, although it still remains high in the north (especially in winter). The diverse machine-learning methods employed, especially Random Forest, have demonstrated their potential in terms of revealing the fire drivers behind fire regime evolution. Moreover, forecasting by the ARIMA model has confirmed the ongoing tendency towards a lower incidence of fire. All indications are that preventive measures should take greater prominence in areas with an abrupt decrease in wildfires, as they are significantly more prone to large ones in the short and medium term.<br /

Exploring spatial–temporal dynamics of fire regime features in mainland Spain

This paper explores spatial–temporal dynamics in fire regime features, such as fire frequency, burnt area, large fires and natural- and human-caused fires, as an essential part of fire regime characterization. Changes in fire features are analysed at different spatial – regional and provincial/NUTS3 – levels, together with summer and winter temporal scales, using historical fire data from Spain for the period 1974–2013. Temporal shifts in fire features are investigated by means of change point detection procedures – Pettitt test, AMOC (at most one change), PELT (pruned exact linear time) and BinSeg (binary segmentation) – at a regional level to identify changes in the time series of the features. A trend analysis was conducted using the Mann–Kendall and Sen's slope tests at both the regional and NUTS3 level. Finally, we applied a principal component analysis (PCA) and varimax rotation to trend outputs – mainly Sen's slope values – to summarize overall temporal behaviour and to explore potential links in the evolution of fire features. Our results suggest that most fire features show remarkable shifts between the late 1980s and the first half of the 1990s. Mann–Kendall outputs revealed negative trends in the Mediterranean region. Results from Sen's slope suggest high spatial and intra-annual variability across the study area. Fire activity related to human sources seems to be experiencing an overall decrease in the northwestern provinces, particularly pronounced during summer. Similarly, the Hinterland and the Mediterranean coast are gradually becoming less fire affected. Finally, PCA enabled trends to be synthesized into four main components: winter fire frequency (PC1), summer burnt area (PC2), large fires (PC3) and natural fires (PC4)