The First World War and coal trade geography in Latin America and the Caribbean (1890-1930)

This paper aims to illustrate the dynamics of coal trade between Latin America and its main trade partners, i.e. the USA, Great Britain and Germany, before and after the enormous disruption caused by the First World War. The coal trade was used as an indicator of modernization for Latin American countries, given that oil was at that time of secondary importance. Energy imports have determined the possibilities of each Latin American country in its process of development. Here we address this question and place special emphasis on supply channels, concluding that the trade link with main suppliers was of key significance. Although this was very clear by the end of the period, the process had started well before the First World War, at least for the majority of LA&C countries. These points are developed through a gravity model applied to the bilateral coal trade. The importance of the market supplier share is addressed through cluster methodologies.

Influence of RF power on the properties of sputtered ZnO:Al thin films

Transparent conducting, aluminium doped zinc oxide thin films (ZnO:Al) were deposited by radio frequency (RF) magnetron sputtering. The RF power was varied from 60 to 350Wwhereas the substrate temperature was kept at 160 °C. The structural, electrical and optical properties of the as-deposited films were found to be influenced by the deposition power. The X-ray diffraction analysis showed that all the films have a strong preferred orientation along the [001] direction. The crystallite size was varied from 14 to 36 nm, however no significant change was observed in the case of lattice constant. The optical band gap varied in the range 3.44-3.58 eV. The lowest resistivity of 1.2×10 -3Vcm was shown by the films deposited at 250 W. The mobility of the films was found to increase with the deposition power.

Transparent conducting thin films by the co-sputtering of ZnO-ITO targets

Transparent and conductive Zn-In-Sn-O (ZITO) amorphous thin films have been deposited at room temperature by the rf magnetron co-sputtering of ITO and ZnO targets. Co-sputtering gives the possibility to deposit multicomponent oxide thin films with different compositions by varying the power to one of the targets. In order to make ZITO films with different Zn content, a constant rf power of 50 W was used for the ITO target, where as the rf power to ZnO target was varied from 25 W to 150 W. The as deposited films showed an increase in Zn content ratio from 17 to 67 % as the power to ZnO target was increased from 25 to 150 W. The structural, electrical and optical properties of the as deposited films are reported. The films showed an average transmittance over 80% in the visible wavelength range. The electrical resistivity and optical band gap of the ZITO films were found to depend on the Zn content in the film. The ZITO films deposited at room temperature with lower Zn content ratios showed better optical transmission and electrical properties compared to ITO film.

Electrical and optical properties of Zn-In-Sn-O transparent conducting thin films

Indium tin oxide (ITO) is one of the widely used transparent conductive oxides (TCO) for application as transparent electrode in thin film silicon solar cells or thin film transistors owing to its low resistivity and high transparency. Nevertheless, indium is a scarce and expensive element and ITO films require high deposition temperature to achieve good electrical and optical properties. On the other hand, although not competing as ITO, doped Zinc Oxide (ZnO) is a promising and cheaper alternative. Therefore, our strategy has been to deposit ITO and ZnO multicomponent thin films at room temperature by radiofrequency (RF) magnetron co-sputtering in order to achieve TCOs with reduced indium content. Thin films of the quaternary system Zn-In-Sn-O (ZITO) with improved electrical and optical properties have been achieved. The samples were deposited by applying different RF powers to ZnO target while keeping a constant RF power to ITO target. This led to ZITO films with zinc content ratio varying between 0 and 67%. The optical, electrical and morphological properties have been thoroughly studied. The film composition was analysed by X-ray Photoelectron Spectroscopy. The films with 17% zinc content ratio showed the lowest resistivity (6.6 × 10 - 4 Ω cm) and the highest transmittance (above 80% in the visible range). Though X-ray Diffraction studies showed amorphous nature for the films, using High Resolution Transmission Electron Microscopy we found that the microstructure of the films consisted of nanometric crystals embedded in a compact amorphous matrix. The effect of post deposition annealing on the films in both reducing and oxidizing atmospheres were studied. The changes were found to strongly depend on the zinc content ratio in the films.

Uniformity Study of Amorphous and Microcrystalline Silicon Thin Films Deposited on 10cmx10cm Glass Substrate using Hot Wire CVD Technique

The scaling up of the Hot Wire Chemical Vapor Deposition (HW-CVD) technique to large deposition area can be done using a catalytic net of equal spaced parallel filaments. The large area deposition limit is defined as the limit whenever a further increment of the catalytic net area does not affect the properties of the deposited film. This is the case when a dense catalytic net is spread on a surface considerably larger than that of the film substrate. To study this limit, a system able to hold a net of twelve wires covering a surface of about 20 cm x 20 cm was used to deposit amorphous (a-Si:H) and microcrystalline (μc-Si:H) silicon over a substrate of 10 cm x 10 cm placed at a filament-substrate distance ranging from 1 to 2 cm. The uniformity of the film thickness d and optical constants, n(x, λ) and α(x,¯hω), was studied via transmission measurements. The thin film uniformity as a function of the filament-substrate distance was studied. The experimental thickness profile was compared with the theoretical result obtained solving the diffusion equations. The optimization of the filament-substrate distance allowed obtaining films with inhomogeneities lower than ±2.5% and deposition rates higher than 1 nm/s and 4.5 nm/s for (μc-Si:H) and (a-Si:H), respectively.

A review of the Tripterygion tripteronotus (Risso, 1810) complex, with a description of a new species from the Mediterranean Sea (Teleostei: Tripterygiidae)

We compared specimens of Tripterygion tripteronotus from 52 localities of the Mediterranean Sea and adjacent waters, using four gene sequences (12S rRNA, tRNA-valine, 16S rRNA and COI) and morphological characters. Two well-differentiated clades with a mean genetic divergence of 6.89±0.73% were found with molecular data, indicating the existence of two different species. These two species have disjunctive geographic distribution areas without any molecular hybrid populations. Subtle but diagnostic morphological differences were also present between the two species. T. tripteronotus is restricted to the northern Mediterranean basin, from the NE coast of Spain to Greece and Turkey, including the islands of Malta and Cyprus. T. tartessicum n. sp. is geographically distributed along the southern coast of Spain, from Cape of La Nao to the Gulf of Cadiz, the Balearic Islands and northern Africa, from Morocco to Tunisia. According to molecular data, these two species could have diverged during the Pliocene glaciations 2.7-3.6 Mya.

The First World War and coal trade geography in Latin America and the Caribbean (1890-1930)

This paper aims to illustrate the dynamics of coal trade between Latin America and its main trade partners, i.e. the USA, Great Britain and Germany, before and after the enormous disruption caused by the First World War. The coal trade was used as an indicator of modernization for Latin American countries, given that oil was at that time of secondary importance. Energy imports have determined the possibilities of each Latin American country in its process of development. Here we address this question and place special emphasis on supply channels, concluding that the trade link with main suppliers was of key significance. Although this was very clear by the end of the period, the process had started well before the First World War, at least for the majority of LA&C countries. These points are developed through a gravity model applied to the bilateral coal trade. The importance of the market supplier share is addressed through cluster methodologies.

Reflexiones en torno a la cultura material. nuevas aproximaciones

Para cualquier arqueólogo, la cultura material representa la base de toda investigación ya que es la documentación prioritaria sobre la cual construye sus teorías e interpretaciones. En los últimos años, algunos antropólogos como Appadurai o Kopitoff han propuesto una nueva lectura de cómo analizar la cultura material en el ámbito de la etnografía. Algunas de sus propuestas, debidamente adaptadas, permiten una reflexión más amplia sobre el estudio de la cultura material, que proponemos aquí.

Arva: prospecciones en un centro productor de ánforas Dressel 20 (Alcolea del Río, Sevilla)

La campaña de excavación realizada en 1991 en las proximidades de sector termal de la ciudad romana de Arva (Alco1ea del Río, Sevilla) ha permitido localizar tres hornos dedicados a la producción de ánforas Dressel20. Uno de ellos se data en época flavio-trajanea; los dos restantes se sitúan en un momento post-severiano. El conjunto parece formar parte del sector artesanal de Arva, situado junto al Guadalquivir.

El circuit comercial de Barcino: reflexions al voltant de les marques amfòriques

Barcino és encara avui una ciutat romana poc coneguda de la província Tarraconense, que segons la majoria d¿especialistes fou fundada per raons polítiques. Malgrat això, una anàlisi detallada de les característiques econòmiques suggereixen que es va crear com a resultat de necessitats comercials, ja que es localitzava en una de les millors zones portuàries del NE de la península. L¿article present pretén reconstruir tot el circuit comercial de Barcino a partir de les nombroses estampilles d¿àmfores trobades en les excavacions. Aquestes marques comercials no solament evidencien una pròspera producció de vi en l¿àrea, sinó també la corresponent demanda externa

Arva: Prospección en un centro productor de ánforas Dressel 20 (Alcolea del Río, Sevilla)

La campaña de excavación realizada en 1991 en las proximidades de sector termal de la ciudad romana de Arva (Alco1ea del Río, Sevilla) ha permitido localizar tres hornos dedicados a la producción de ánforas Dressel20. Uno de ellos se data en época flavio-trajanea; los dos restantes se sitúan en un momento post-severiano. El conjunto parece formar parte del sector artesanal de Arva, situado junto al Guadalquivir.

El fracaso escolar y los supuestos esenciales de la reforma: la percepción del profesorado de la educación secundaria en Cataluña (España)

Nuestra intención y objetivo ha sido establecer un diálogo con profesores de la enseñanza secundaria Obligatoria (ESO) con la finalidad de comprender, analizar e interpretar sus pensamientos, ideas, acciones y opiniones en relación a los supuestos básicos de las reformas educativas y el fracaso escolar. Hemos realizado dicho diálogo desde una perspectiva tanto sincrónica como diacrónica y, a este efecto, el profesorado participante cumple el requisito de llevar más de 30 años en activo. Esta perspectiva sincrónica/diacrónica nos ha permitido rastrear el pensamiento y la experiencia vivida, de modo transversal, a través de las reformas educativas desde la postura profesional del ¿hoy¿. En este contexto, hemos valorado el conocimiento y experiencia acumulada de aquellos profesionales que iniciaron sus carreras en plena etapa predemocrática y que han vivido todos los cambios como un valor añadido.