Learning from Letchworth and Welwyn Garden City: garden cities’ policies for the development of existing settlements in the contemporary world

So far, the garden city model has been analysed and adopted by scholars, urban planners, and institutions to design garden cities, new towns, and suburban communities as new settlements from scratch around the world. In contrast, this paper explores the potentialities of such a model to provide a multi-faceted approach based on territorial, socio-economic, and urban planning strategies, thus offering a series of policies to combat a wide range of issues in existing communities. For that purpose, this paper provides a new approach about the garden city model through the case studies of Letchworth and Welwyn Garden City and latest updated models to form a new scheme with the capability to encourage the decentralisation of population and means of production across the territory, develop cooperatives to achieve a self-financing system and affordable housing in existing communities, and implement the garden cities’ design principles for the regeneration and expansion of existing settlements towards a sustainable, attractive, self-reliant and prosperous future.Funding for open access charge: Universidad de Málaga / CBU

Efeito das dimensões do espécime na resistência à flexão de uma resina composta

PUORPOSE: The aim of this study was to evaluate the effect of specimen dimensions on the flexural strength of a composite resin (Heliomolar RO). METHODS: The different dimensions tested - length x width x height (mm) were: 25x2x4; 25x2x2 (ISO 4049); 15x2x2; 10x2x2 and 10x2x1. Light-curing was performed at 600 mW/cm² for 40s, three times along the 25mm specimens, twice along 15mm specimen and once for the 10mm specimens. Specimens of all dimensions were light-cured on both surfaces, or only on one side. In the latter, the load was applied on the irradiated side or on the opposite one. RESULTS: It was shown that the flexural strength was not affected by specimen length. When light-curing was performed on both surfaces, similar flexural strength values were obtained for any dimension. Despite the number of irradiated surfaces, specimens with a height of 1mm also obtained similar values. On the contrary, specimens with a height of 4mm, exposed only on one surface, reached the lowest strength. CONCLUSION: The use of specimens with lower dimensions can lead to flexural strength values similar to the ones obtained with standardized specimen (ISO 4049), with the advantage of demanding less amount of material and being less time consuming.OBJETIVO: A finalidade da presente investigação foi avaliar a influência das dimensões dos corpos-de-prova (cp) e da superfície de irradiação na resistência à flexão de uma resina composta (Heliomolar RO). MÉTODOS: As diversas dimensões adotadas - comprimento x largura x altura (mm) foram: 25x2x4; 25x2x2 (ISO 4049); 15x2x2; 10x2x2; 10x2x1. A fotoativação foi realizada por 40 segundos a 600mW/cm²; três vezes ao longo dos cp de 25mm, duas vezes ao longo dos cp de 15mm e uma vez nos cp de 10mm de comprimento. Os corpos-de-prova de todas as dimensões foram ativados em ambas as superfícies, ou apenas em uma; neste caso a carga de ruptura era aplicada na face de irradiação ou na oposta. RESULTADOS: Foi mostrado que a resistência à flexão não foi afetada pelo comprimento dos cp. Com a fotoativação em ambas as superfícies, as resistências obtidas eram semelhantes nos diversos comprimentos. Independentemente do número de faces irradiadas, os cp com 1mm de altura apresentaram resistências semelhantes. Contudo, cp com 4mm de altura e irradiados apenas por um lado, alcançaram os menores valores. CONCLUSÃO: Com o emprego de cp com dimensões menores são alcançados valores de resistência à flexão semelhante aos obtidos com cp padronizados (ISO 4049), com a vantagem de menor demanda de material e menor consumo de tempo (o menor comprimento dos cp requer apenas uma ativação por lado)

The invasive species Asparagopsis taxiformis (Bonnemaisoniales, Rhodophyta) on Andalusian coast (Southern Spain): reproductive stages, new records and invaded communities

The invasive species Asparagopsis taxiformis (Bonnemaisoniales, Rhodophyta) on Andalusian coasts (Southern Spain): reproductive stages, new records and invaded communities.The present study provides new records from Andalusian coasts of the exotic invasive seaweed Asparagopsis taxiformis (Delile) Trevisan. These records demonstrate that A. taxiformis has rapidly and widely expanded its distribution range in this region, from Almería to Cádiz (Strait of Gibraltar).The latter locality may represent the western geographical limit of the species in the Mediterranean Sea. Spermatangial heads and cystocarps were observed in the collected gametophytes. Additionally, we report the first record of the tetrasporophytic stage, Falkenbergia hillebrandii (Bornet) Falkenberg from the Andalusian coast, although tetraspores were not encountered in these samples. Consequently, information on the affected communities and arguments for considering A. taxiformis as an invasive species in the Andalusian coast are provided.La especie invasora Asparagopsis taxiformis (Bonnemaisoniales, Rhodophyta) en las costas andaluzas (Sur de España): fases reproductivas, nuevas citas y comunidades invadidas. El presente trabajo aporta nuevas citas para las costas andaluzas de la especie exótica invasora de macroalga Asparagopsis taxiformis (Delile) Trevisan. Estas citas muestran que la especie ha aumentado ampliamente su área de distribución de manera rápida en esta región, desde Almería hasta Cádiz (Estrecho de Gibraltar). Esta última localidad representaría el límite occidental de la especie en el mar Mediterráneo. En las muestras recogidas de gametofitos se pudieron observar ramas espermatangiales y cistocarpos. Se aporta la primera cita del estadio tetrasporofítico, Falkenbergia hillebrandii (Bornet) Falkenberg en las costas andaluzas, aunque no se observaron tetrásporas en estas muestras. Se informa sobre las comunidades afectadas y se dan argumentos para considerar a A.taxiformis invasora en las costas andaluzas

Microstructure and mechanical properties of grains of silica nanofluids dried in an acoustic levitator

The microstructure and mechanical properties of spray-dried grains are key factors in many applications. In this work single droplets of silica nanofluids were dried in an acoustic levitator under different experimental conditions of solid mass fraction, pH value, salt concentration, drying temperature and initial droplet volume. ANOVA method was used to determine their influence on the final grain diameter, the shell thickness and the mechanical strength. The solid content and the droplet volume are the variables that exert an influence on these three properties. In addition, the mechanical strength is influenced by the pH value. The maximum packing fraction of the particles inside the shell was obtained by modeling the viscosity data with the Quemada equation. The packing fraction was then used to calculate the shell thickness. The internal microstructure of the grains was observed by SEM and the shell thickness was measured. Experimental and calculated results show good agreemen

El proceso de secado por atomización: formación de gránulos y cinética de secado de gotas

Spray drying is a unit operation very common in many industrial processes. For each particular application, the resulting granulated material must possess determined properties that depend on the conditions in which the spray drying processing has been carried out, and whose dependence must be known in order to optimize the quality of the material obtained. The large number of variables that influence on the processes of matter and energy transfer and on the formation of granular material has required a detailed analysis of the drying process. Over the years there have been many studies on the spray drying processing of all kind of materials and the influence of process variables on the drying kinetics of the granulated material properties obtained. This article lists the most important works published for both the spray drying processing and the drying of individual droplets, as well as studies aimed at modeling the drying kinetics of drops.El proceso de secado por atomización es una operación unitaria que interviene en numerosas aplicaciones industriales. Para cada aplicación en concreto, el material granulado resultante debe poseer unas propiedades determinadas que dependen de las condiciones en las que se lleve a cabo el secado por atomización, y cuya dependencia debe conocerse para así optimizar la calidad del material obtenido. El gran número de variables que influyen en los procesos de transferencia de materia y energía que tienen lugar, y en la formación del material granulado, han hecho necesario el análisis en detalle del proceso de secado. A lo largo de los años han sido muchos los estudios realizados sobre el secado por atomización y la influencia de las variables del proceso en la cinética de secado y las propiedades del material granulado obtenido, para todo tipo de materiales. En este artículo se recogen los trabajos más importantes publicados correspondientes tanto al secado por atomización como al secado de gotas individuales, así como los estudios cuyo objetivo es el modelado de la cinética de secado de gotas

Characterization of silica–water nanofluids dispersed with an ultrasound probe: A study of their physical properties and stability

The stability and agglomeration state of nanofluids are key parameters for their use in different applications. Silica nanofluids were prepared by dispersing the nanoparticles in distilled water using an ultrasonic probe, which has proved to be the most effective system and gives the best results when compared with previous works. Results were obtained concerning the influence of the solid content, pH and salt concentration on the zeta potential, electrical double layer, viscosity, elastic and viscous moduli, particle size and light backscattering. Measurement of all these properties provides information about the colloidal state of nanofluids. The most important variable is the solid content. Despite the agglomeration due to high concentration, nanofluids with low viscosity and behaving like liquid were prepared at 20% of mass load thanks to the good dispersion achieved with the ultrasonic treatment. The pH of the medium can be used to control the stability, since the nanofluids are more stable under basic conditions far from the isoelectric point (IEP) and settle at pH = 2. Therefore, stable nanofluids for at least 48 h, with high solid content, can be prepared at high pH value (pH > 7) due to the electrostatic repulsion between particles

Encuadre fitosociológico y valor de conservación de los abedulares riparios supratemplados del noroeste de la Península Ibérica

We studied the downy birch forests that grow in the headwaters of rivers in the mountains in NW Iberian Peninsula and their differences from other previously described birch forests. To do this, an ordination analysis was done on a database of 342 relevés (144 unpublished). As a result, four riparian forest associations were recognized in the territory, all of them belonging to the suballiance Saxifrago spathularis-Fraxinenion excelsioris (Hyperico androsaemi-Alnion glutinosae, Alno-Fraxinetaliaexcelsioris, Salici-Populetea). Two associations (Carici reuterianae-Betuletum celtibericae and Violo palustris-Betuletum pubescentis) have been previously described, but the other two (Chaerophyllo hirsuti-Betuletum pubescentis and Valeriano officinalis-Betuletum pubescentis) are described here for the first time. We characterized their floristic composition, ecological features and distribution, and evaluated their conservation value under the criteria of the 92/43/CEE Community Directive, and with regard to national and regional lists of protected speciesEn este trabajo se aborda el estudio de las comunidades de abedulares riparios presentes en los tramosde cabecera de diversos macizos montañosos del extremo NW Ibérico y su diferenciación frente a otros tipos de abedulares previamente descritos. Para ello se ha aplicado un análisis de ordenación a una base de datos conformadapor 342 inventarios (144 inéditos). Como resultado, se reconocen cuatro asociaciones vegetales integradas en la subalianza Saxifrago spathularis-Fraxinenion excelsioris (Hyperico androsaemi-Alnion glutinosae, Alno-Fraxinetaliaexcelsioris, Salici-Populetea). Dos de ellas (Carici reuterianae-Betuletum celtibericae y Violo palustris-Betuletum pubescentis) eran previamente conocidas mientras que las otras dos (Chaerophyllo hirsuti-Betuletum pubescentis and Valeriano officinalis-Betuletum pubescentis) se dan a conocer aquí por primera vez. Para cada una de ellas se precisa su composición florística, ecología y distribución biogeográfica y se discute su valor de conservación en relación a los criterios establecidos en la Directiva Comunitaria 92/43/CEE así como a los catálogosnacionales y regionales de especies protegidas.S