Solar radiation over and under sea ice and photographic quantification of Ice algal aggregates during the POLARSTERN cruise ARK-XXVII/3 (IceArc) in summer 2012

The ice cover of the Arctic Ocean has been changing dramatically in the last decades and the consequences for the sea-ice associated ecosystem remain difficult to assess. Algal aggregates underneath sea ice have been described sporadically but the frequency and distribution of their occurrence is not well quantified. We used upward looking images obtained by a remotely operated vehicle (ROV) to derive estimates of ice algal aggregate biomass and to investigate their spatial distribution. During the IceArc expedition (ARK-XXVII/3) of RV Polarstern in late summer 2012, different types of algal aggregates were observed floating underneath various ice types in the Central Arctic basins. Our results show that the floe scale distribution of algal aggregates in late summer is very patchy and determined by the topography of the ice underside, with aggregates collecting in dome shaped structures and at the edges of pressure ridges. The buoyancy of the aggregates was also evident from analysis of the aggregate size distribution. Different approaches used to estimate aggregate biomass yield a wide range of results. This highlights that special care must be taken when upscaling observations and comparing results from surveys conducted using different methods or on different spatial scales.

(Table 1) 40Ar-39Ar incremental heating ages for ODP Hole 163-988A basalt and plagioclase

Results of 40Ar-39Ar Ar dating constrain the age of the submerged volcanic succession, part of the seaward-dipping reflector sequence of the Southeast Greenland volcanic rifted margin, recovered during Leg 163. At the 63ºN drilling transect, the fully normally magnetized volcanic units at Holes 989B (Unit 1) and 990A (Units 1 and 2) are dated at 57.1 ± 1.3 Ma and 55.6 ± 0.6 Ma, respectively. This correlates with a common magnetochron, C25n. The underlying, reversely magnetized lavas at Hole 990A (Units 3-13) yield an average age of 55.8 ± 0.7 Ma and may correlate with C25r. The argon data, however, are also consistent with eruption of the lavas at Site 990 during the very earliest portion of C24. If so, the normally polarized units have to be correlated to a cryptochron (e.g., C24r-11 at ~55.57 Ma). The lavas at Holes 989B and 990A have typical oceanic compositions, implying that final plate separation between Greenland and northwest Europe took place at ~56 Ma. The age for Hole 989B lava is younger than expected from the seismic interpretations, posing questions about the structural evolution of the margin. An age of 49.6 ± 0.2 Ma for the basaltic lava at Site 988 (~66ºN) points to the importance of postbreakup tholeiitic magmatism at the rifted margin. Together with results from Leg 152, a virtually complete time frame for ~12 m.y. of pre-, syn-, and postbreakup volcanism during rifted margin evolution in Southeast Greenland can now be assembled. This time frame includes continental type volcanism at ~61-60 Ma, synbreakup volcanism beginning at ~57 Ma, and postbreakup volcanism at ~49.6 Ma. These discrete time windows coincide with distinct periods of tholeiitic magmatism from the onshore East Greenland Tertiary Igneous Province and is consistent with discrete mantle-melting events triggered by plume arrival (~61-60 Ma) under central Greenland, continental breakup (~57-54 Ma), and passage of the plume axis beneath the East Greenland rifted margin after breakup (~50-49 Ma), respectively.

Eugenio María de Hostos en el Cono Sur

Abordaremos un tramo del pensamiento de Eugenio María de Hostos correspondiente a su estancia en el Cono Sur, particularmente en Argentina durante su peregrinación por América. Trabajamos sobre la producción periodística comprendida entre los años 1870 y 1873 en diarios de Chile y Argentina. En dichos textos puede apreciarse el desarrollo de dos líneas temáticas convergentes: la primera dedicada al seguimiento de los hechos que se suceden en las Antillas, en particular la lucha de Cuba por su independencia; la segunda comprende una importante cantidad de crónicas y comentarios sobre la vida y el desarrollo sociocultural de los países que visita. Son temáticas convergentes pues ambas están orientadas en el sentido de un proyecto modernizador, tendiente a unir la causa antillana a la causa de la civilización de los pueblos hermanos de América. En esta perspectiva, la modernización impulsada por Hostos adquiere tonalidades y acentuaciones especiales.

Víctor Mercante y su proyecto educativo : Reforma de Saavedra-Lamas

Considerando que es posible pensar la historia de la educación como un camino para lograr reconstruir la producción y circulación de ideas de una determinada época, el presente trabajo tiene como objeto no solo iniciar el estudio de un pedagogo como lo es Víctor Mercante (1870-1934) involucrado en la educación argentina de finales del Siglo XIX y principios del XX-sino comenzar a recorrer una trayectoria profesional permeada de las discusiones y debates de la época. Mercante aporta una mirada que presenta aspectos innovadores en clave de un período histórico determinado rico por el abanico de perspectivas culturales que en él se concentran. Con este objeto hemos trabajado en el análisis del contenido de la reforma educativa Saavedra-Lamas de la cual es mentor y en su sustento teórico, a partir del propio pensamiento de Mercante y de las condiciones en las que la misma fue implementada y en las que fue derogada. La intención final es alcanzar una explicación que de cuenta de las condiciones de la relación entre corrientes y tradiciones intelectuales, fuerzas políticas y actores sociales en el marco de un proceso de reforma educativa

Activity, work and employment: some reflections on a topic under debate

Since ten years ago, it is intensely thought of human work and employment in developed countries as a consequence of the deep changes on the productive system. In this chapter we analyze at first place the concept of work and its evolution, based on recent researches. In second place we review the notions of activity, work and employment and also the definition and measurement of unemployment, which is not a very old notion. The third part is about the work rol in human life and finally we study the different alternatives on activity and specific work contracts, proposals that nowadays replace the notion of "full employment" in France.

Víctor Mercante y su proyecto educativo : Reforma de Saavedra-Lamas

Considerando que es posible pensar la historia de la educación como un camino para lograr reconstruir la producción y circulación de ideas de una determinada época, el presente trabajo tiene como objeto no solo iniciar el estudio de un pedagogo como lo es Víctor Mercante (1870-1934) involucrado en la educación argentina de finales del Siglo XIX y principios del XX-sino comenzar a recorrer una trayectoria profesional permeada de las discusiones y debates de la época. Mercante aporta una mirada que presenta aspectos innovadores en clave de un período histórico determinado rico por el abanico de perspectivas culturales que en él se concentran. Con este objeto hemos trabajado en el análisis del contenido de la reforma educativa Saavedra-Lamas de la cual es mentor y en su sustento teórico, a partir del propio pensamiento de Mercante y de las condiciones en las que la misma fue implementada y en las que fue derogada. La intención final es alcanzar una explicación que de cuenta de las condiciones de la relación entre corrientes y tradiciones intelectuales, fuerzas políticas y actores sociales en el marco de un proceso de reforma educativa

Activity, work and employment: some reflections on a topic under debate

Since ten years ago, it is intensely thought of human work and employment in developed countries as a consequence of the deep changes on the productive system. In this chapter we analyze at first place the concept of work and its evolution, based on recent researches. In second place we review the notions of activity, work and employment and also the definition and measurement of unemployment, which is not a very old notion. The third part is about the work rol in human life and finally we study the different alternatives on activity and specific work contracts, proposals that nowadays replace the notion of "full employment" in France.

Víctor Mercante y su proyecto educativo : Reforma de Saavedra-Lamas

Considerando que es posible pensar la historia de la educación como un camino para lograr reconstruir la producción y circulación de ideas de una determinada época, el presente trabajo tiene como objeto no solo iniciar el estudio de un pedagogo como lo es Víctor Mercante (1870-1934) involucrado en la educación argentina de finales del Siglo XIX y principios del XX-sino comenzar a recorrer una trayectoria profesional permeada de las discusiones y debates de la época. Mercante aporta una mirada que presenta aspectos innovadores en clave de un período histórico determinado rico por el abanico de perspectivas culturales que en él se concentran. Con este objeto hemos trabajado en el análisis del contenido de la reforma educativa Saavedra-Lamas de la cual es mentor y en su sustento teórico, a partir del propio pensamiento de Mercante y de las condiciones en las que la misma fue implementada y en las que fue derogada. La intención final es alcanzar una explicación que de cuenta de las condiciones de la relación entre corrientes y tradiciones intelectuales, fuerzas políticas y actores sociales en el marco de un proceso de reforma educativa

Activity, work and employment: some reflections on a topic under debate

Since ten years ago, it is intensely thought of human work and employment in developed countries as a consequence of the deep changes on the productive system. In this chapter we analyze at first place the concept of work and its evolution, based on recent researches. In second place we review the notions of activity, work and employment and also the definition and measurement of unemployment, which is not a very old notion. The third part is about the work rol in human life and finally we study the different alternatives on activity and specific work contracts, proposals that nowadays replace the notion of "full employment" in France.

Water chemistry, and abundance and carbon biomass of under-ice fauna during POLARSTERN cruise ARK-XIX/1 to the Storfjord area in 2003

The under-ice habitat and fauna were studied during a typical winter situation at three stations in the western Barents Sea. Dense pack ice (7-10/10) prevailed and ice thickness ranged over <0.1-1.6 m covered by <0.1-0.6 m of snow. Air temperatures ranged between -1.8 and -27.5°C. The ice undersides were level, white and smooth. Temperature and salinity profiles in the under-ice water (0-5 m depth) were not stratified (T=-1.9 to -2.0°C and S=34.2-34.7). Concentrations of inorganic nutrients were high and concentrations of algal pigments were very low (0.02 µg chlorophyll a/l), indicating the state of biological winter. Contents of particulate organic carbon and nitrogen ranged over 84.2-241.3 and 5.3-16.4 µg/l, respectively, the C/N ratio over 11.2-15.5 pointing to the dominance of detritus in the under-ice water. Abundances of amphipods at the ice underside were lower than in other seasons: 0-1.8 ind/m**2 for Apherusa glacialis, 0-0.7 ind/m**2 for Onisimus spp., and 0-0.8 ind/m**2 for Gammarus wilkitzkii. A total of 22 metazoan taxa were found in the under-ice water, with copepods as the most diverse and numerous group. Total abundances ranged over 181-2,487 ind/m**3 (biomass: 70-2,439 µg C/m**3), showing lower values than in spring, summer and autumn. The dominant species was the calanoid copepod Pseudocalanus minutus (34-1,485 ind/m**3), contributing 19-65% to total abundances, followed by copepod nauplii (85-548 ind/m**3) and the cyclopoid copepod Oithona similis (44-262 ind/m**3). Sympagic (ice-associated) organisms occurred only rarely in the under-ice water layer.

Photochemical responses of the diatom Skeletonema costatum grown under elevated CO2 concentrations to short-term changes in pH

Variability in pH is a common occurrence in many aquatic environments, due to physical, chemical and biological processes. In coastal waters, lagoons, estuaries and inland waters, pH can change very rapidly (within seconds or hours) in addition to daily and seasonal changes. At the same time, progressive ocean acidification caused by anthropogenic CO2 emissions is superimposed on these spatial and temporal pH changes. Photosynthetic organisms are therefore unavoidably subject to significant pH variations at the cell surface. Whether this will affect their response to long-term ocean acidification is still unknown, nor is it known whether the short-term sensitivity to pH change is affected by the pCO2 to which the cells are acclimated. We posed the latter open question as our experimental hypothesis: Does acclimation to seawater acidification affect the response of phytoplankton to acute pH variations? The diatom Skeletonema costatum, commonly found in coastal and estuarine waters where short-term acute changes in pH frequently occur, was selected to test the hypothesis. Diatoms were grown at both 390 (pH 8.2, low CO2; LC) and 1000 (pH 7.9, high CO2; HC) µatm CO2 for at least 20 generations, and photosynthetic responses to short-term and acute changes in pH (between 8.2 and 7.6) were investigated. The effective quantum yield of LC-grown cells decreased by ca. 70% only when exposed to pH 7.6; this was not observed when exposed to pH 7.9 or 8.2. HC-grown cells did not show significant responses in any pH treatment. Non-photochemical quenching showed opposite trends. In general, our results indicate that while LC-grown cells are rather sensitive to acidification, HC-grown cells are relatively unresponsive in terms of photochemical performance.

Sustainable Development and Poverty Reduction under Mubarak's Program

This paper describes and analyzes the major features of economic development and poverty reduction in Egypt during its transition to a market Economy. It focuses on the changes in the situation of poverty and economic policies pursued as remedies by the government of Egypt and the ruling NDP. Sustainable development and poverty reduction is the core of the President Mubarak’s election campaign for his fifth term for the presidency. We attempt to explain the obstacles encountered by the Egyptian economy in terms of adjustments and general economic arguments on poverty. Finally, we refer to the necessity for enhanced accountability in the society to accomplish the goal.

Trace Elements Distribution in Red Soils under Semiarid Mediterranean Environment

This study states the potential trace elements (TE’s) content of red soils located at the centre region of Spain, characterized by low rainfall and slight acidity over prolonged weathering periods. For this purpose, three soil profiles from a catena were described, sampled and analyzed. The most notable characteristics are the low organic matter content and the predominantly acidic pH. Illite and kaolinite are the predominant clay minerals. The fertility of the soils is sufficient to provide most of the nutrients required, with very suitable potassium levels. The geochemical characters of this soil are: only few elements remain almost invariable across the profiles and over time, however the majority of them were directly linked with the clay content. These soils are characterized by relatively low levels of some trace elements such as Sr (64.35 mg?kg–1), Ba (303.67 mg?kg–1) and Sc (13.14 mg?kg–1); high levels of other trace elements such as V (103.92 mg?kg–1), Cr (79.9 mg?kg–1), Cu (15.18 mg?kg–1), Hf (10.26 mg?kg–1), Ni (38 mg?kg–1) and Zr (337 mg?kg–1); while the levels for rare earth elements (REE’s) such as La (48.36 mg?kg–1), Ce (95.07 mg?kg–1), Th (13.33 mg?kg–1) and Nd (42.65 mg?kg–1) are significantly high. The distribution of mayor and trace elements was directly re- lated to weathering processes, parent material and anthropogenic activities.

Structural behaviour and design criteria of under-deck cable-stayed bridges subjected to seismic action

Under-deck cable-stayed bridges are very effective structural systems for which the strong contribution of the stay cables under live loading allows for the design of very slender decks for persistent and transient loading scenarios. Their behaviour when subjected to seismic excitation is investigated herein and a set of design criteria are presented that relate to the type and arrangement of bearings, the number and configuration of struts, and the transverse distribution of stay cables. The nonlinear behaviour of these bridges when subject to both near-field and far-field accelerograms has been thoroughly investigated through the use of incremental dynamic analyses. An intensity measure that reflects the pertinent contributions to response when several vibration modes are activated was proposed and is shown to be effective for the analysis of this structural type. The under-deck cable-stay system contributes in a very positive manner to reducing the response when the bridges are subject to very strong seismic excitation. For such scenarios, the reduction in the stiffness of the deck because of crack formation, when prestressed concrete decks are used, mobilises the cable system and enhances the overall performance of the system. Sets of natural accelerograms that are compliant with the prescriptions of Eurocode 8 were also applied to propose a set of design criteria for this bridge type in areas prone to earthquakes. Particular attention is given to outlining the optimal strategies for the deployment of bearings

Research on intermediate band solar cells and development of experimental techniques for their characterization under concentrated illumination

Abstract This work is a contribution to the research and development of the intermediate band solar cell (IBSC), a high efficiency photovoltaic concept that features the advantages of both low and high bandgap solar cells. The resemblance with a low bandgap solar cell comes from the fact that the IBSC hosts an electronic energy band -the intermediate band (IB)- within the semiconductor bandgap. This IB allows the collection of sub-bandgap energy photons by means of two-step photon absorption processes, from the valence band (VB) to the IB and from there to the conduction band (CB). The exploitation of these low energy photons implies a more efficient use of the solar spectrum. The resemblance of the IBSC with a high bandgap solar cell is related to the preservation of the voltage: the open-circuit voltage (VOC) of an IBSC is not limited by any of the sub-bandgaps (involving the IB), but only by the fundamental bandgap (defined from the VB to the CB). Nevertheless, the presence of the IB allows new paths for electronic recombination and the performance of the IBSC is degraded at 1 sun operation conditions. A theoretical argument is presented regarding the need for the use of concentrated illumination in order to circumvent the degradation of the voltage derived from the increase in the recombi¬nation. This theory is supported by the experimental verification carried out with our novel characterization technique consisting of the acquisition of photogenerated current (IL)-VOC pairs under low temperature and concentrated light. Besides, at this stage of the IBSC research, several new IB materials are being engineered and our novel character¬ization tool can be very useful to provide feedback on their capability to perform as real IBSCs, verifying or disregarding the fulfillment of the “voltage preservation” principle. An analytical model has also been developed to assess the potential of quantum-dot (QD)-IBSCs. It is based on the calculation of band alignment of III-V alloyed heterojunc-tions, the estimation of the confined energy levels in a QD and the calculation of the de¬tailed balance efficiency. Several potentially useful QD materials have been identified, such as InAs/AlxGa1-xAs, InAs/GaxIn1-xP, InAs1-yNy/AlAsxSb1-x or InAs1-zNz/Alx[GayIn1-y]1-xP. Finally, a model for the analysis of the series resistance of a concentrator solar cell has also been developed to design and fabricate IBSCs adapted to 1,000 suns. Resumen Este trabajo contribuye a la investigación y al desarrollo de la célula solar de banda intermedia (IBSC), un concepto fotovoltaico de alta eficiencia que auna las ventajas de una célula solar de bajo y de alto gap. La IBSC se parece a una célula solar de bajo gap (o banda prohibida) en que la IBSC alberga una banda de energía -la banda intermedia (IB)-en el seno de la banda prohibida. Esta IB permite colectar fotones de energía inferior a la banda prohibida por medio de procesos de absorción de fotones en dos pasos, de la banda de valencia (VB) a la IB y de allí a la banda de conducción (CB). El aprovechamiento de estos fotones de baja energía conlleva un empleo más eficiente del espectro solar. La semejanza antre la IBSC y una célula solar de alto gap está relacionada con la preservación del voltaje: la tensión de circuito abierto (Vbc) de una IBSC no está limitada por ninguna de las fracciones en las que la IB divide a la banda prohibida, sino que está únicamente limitada por el ancho de banda fundamental del semiconductor (definido entre VB y CB). No obstante, la presencia de la IB posibilita nuevos caminos de recombinación electrónica, lo cual degrada el rendimiento de la IBSC a 1 sol. Este trabajo argumenta de forma teórica la necesidad de emplear luz concentrada para evitar compensar el aumento de la recom¬binación de la IBSC y evitar la degradación del voltage. Lo anterior se ha verificado experimentalmente por medio de nuestra novedosa técnica de caracterización consistente en la adquisicin de pares de corriente fotogenerada (IL)-VOG en concentración y a baja temperatura. En esta etapa de la investigación, se están desarrollando nuevos materiales de IB y nuestra herramienta de caracterizacin está siendo empleada para realimentar el proceso de fabricación, comprobando si los materiales tienen capacidad para operar como verdaderas IBSCs por medio de la verificación del principio de preservación del voltaje. También se ha desarrollado un modelo analítico para evaluar el potencial de IBSCs de puntos cuánticos. Dicho modelo está basado en el cálculo del alineamiento de bandas de energía en heterouniones de aleaciones de materiales III-V, en la estimación de la energía de los niveles confinados en un QD y en el cálculo de la eficiencia de balance detallado. Este modelo ha permitido identificar varios materiales de QDs potencialmente útiles como InAs/AlxGai_xAs, InAs/GaxIni_xP, InAsi_yNy/AlAsxSbi_x ó InAsi_zNz/Alx[GayIni_y]i_xP. Finalmente, también se ha desarrollado un modelado teórico para el análisis de la resistencia serie de una célula solar de concentración. Gracias a dicho modelo se han diseñado y fabricado IBSCs adaptadas a 1.000 soles.