Multi-Proxy Approach for Identifying Heinrich Events in Sediment Cores from Hatton Bank (NE Atlantic Ocean)

A series of six gravity cores has been used to reconstruct the depositional history of Hatton Bank (Rockall Plateau, NE Atlantic Ocean). The cores have been studied for magnetic susceptibility (MS), geochemical composition, grain size distribution, and a semi-quantitative foraminiferal association. Two main interbedded facies have been described: (i) calcareous ooze; and (ii) lithogenous silt. The study reveals prominent peaks from the MS signal, silt, Mg/Ca, Fe/Ca, Al/Ca, and Rare Earth Elements normalised by Continental Crust (REE/CC), which are sensitive indicators for Heinrich events (H1, H2, H3, H4, and H5) and ash layers. These peaks may relate to alternations in dominance of the calcareous and lithogenic facies. The sediment displays a high percentage of carbonate in interglacial layers but is lithogenic-dominated in glacial stages. The layers with prominent lithic-rich and foraminifera-poor sediments (established as Heinrich layers) may be related to a possible palaeoclimatic effect, where freshwater discharged during iceberg melting may have reduced the formation of North Atlantic Deep Water (NADW). In the study area, the mean sedimentation rates for the last glacial as ~4.2 cm ka−1 and ~1.4 cm ka−1 for the last ~18 ka (interglacial period) have been estimated. Besides this evidence, Fe/Ca and MS peaks may reflect the presence of basalt, either introduced through ice-rafting or transported and redistributed by bottom currents in the study area. Certain indices, including MS and Fe/Ca, are proposed as good proxies for detecting Heinrich events and ash layers in the Hatton Bank sediments and, in consequence, are parameters that can be used to infer strengthened/weakened NADW formation, according to stadials/interstadials. Moreover, we suggest that the northernmost boundary of the area with evidence of Heinrich events may be situated around 57°38′ N in the Hatton–Rockall area, at least for H4, based on the variation of the Mg/Ca and Fe/Ca curves

The influence of basin slope and fluvial flow on deltaic built-up processes off mountainous, seasonal rivers

0,000

An analysis of the prevalence of peripheral giant cell granuloma and pyogenic granuloma in relation to a dental implant

Background: The aim of the present investigation was to evaluate the literature recurrence of peripheral giant cell granuloma and pyogenic granuloma associated with dental implants. It's important to know the characteristics present in these lesions and possible effects on the prognosis of dental implants. Methods: An electronic search without time restrictions was done in the databases: PubMed/Medline. With the keywords "Granuloma" OR "Granuloma, Giant Cell" OR "peripheral giant cell" OR "Granuloma, Pyogenic" AND "Dental implants" OR "Oral implants". Results: After applying the inclusion and exclusion criteria, a total of 20 articles were included, which reported 32 lesions (10 pyogenic granulomas, 21 peripheral giant cell granulomas and one peripheral giant cell granuloma combined with peripheral ossifying fibroma, all associated with implants). According to our review, these lesions are more frequent in males and in the posterior region of the mandible. Both excision and curettage of the lesion, compared to only excision, presented similar recurrences (40%). Explantation of the implant was performed in 41% of cases without additional recurrences. The results are not statistically significant when comparing one lesion to the other in terms of explantation (p = 0.97), recurrence (p = 0.57) or bone loss (p = 0.67). Conclusions: The main therapeutic approach is tissue excision. The lesions show a high recurrence rate (34.4%), which often requires explantation of the associated implant. This recurrence rate is not affected by curettage after excision

Evolución de los deltas submarinos de los ríos Guadalfeo y Adra en respuesta a las variaciones de los aportes sedimentarios

The Guadalfeo and the Adra submarine deltas off the northern coast of the Alboran Sea have been built up under the direct influence of short and mountainous rivers. The area is subjected to strong climatic seasonality, with sporadic winter torrential floods and high summer aridity. In addition numerous anthropogenic activities have affected these systems, mostly during the last two centuries. In order to decode the influence of climatic variability and anthropogenic impacts on sediment supplies during the recent past, five sediment cores were collected from the Guadalfeo and Adra submarine deltas. Benthic foraminiferal and sedimentological analyses, combined with radiocarbon dating, were performed. The impact of torrential floods alternating with periods of low rainfall or dry periods were recorded in the Adra and Guadalfeo prodeltas. Periods with low abundance of benthic foraminifera and high amounts of coarse-grained sediments, were interpreted as the result of enhanced sediment supply to the shelf triggered by major flood events. On the other hand, periods with high amounts of fine-grained sediments and high abundances of colonizers and opportunistic foraminiferal species indicate the establishment of new environments with distinct ecological constraints. These environments were driven by lower sediment supplies during low rainfall or dry periods. The most recent sedimentation seems to reflect the human interventions in the rivers basins, such as deviation of the main river courses and dams construction, which reduced the sediment input and promoted the deposition of shallow-water submarine deltas.Versión del edito

The evolution of the Guadalfeo submarine delta (northern Alboran Sea) during the last ca. 200 years

The Guadalfeo submarine delta is located on the northern Alboran Sea shelf in the western Mediterranean Sea. The sedimentary dynamics of the deltaic system is governed by the discharge of one of the major rivers in this area draining the western sector of the near-coastal Sierra Nevada Mountains. The area is under the influence of a Mediterranean climate, with high spatial and temporal (i.e., inter- and intra-annual) rain variability. Major anthropogenic forcing affected the river system during the 1930’s, with the deviation of the main river channel 2.5 km to the west, to its present position. More recently, the construction of Béznar (1977-1985) and Rules (1993-2003) dams have also contributed to limit the amount of sediments exported to the deltaic system. In order to understand the interaction between river discharges and the evolution of the submarine delta at different timescales, sediment cores were collected off the ancient (core 13) and present-day (cores12 and 15) river courses. A chronological framework was performed and combined with sedimentological and benthic foraminiferal analyses. Radiocarbon dating of plant debris from the base of the cores indicates that the sedimentary record goes back 200 years. In core 13, the variations between coarse and fine fractions along the core and the upward increase of benthic foraminiferal population density, would indicate that deposition possibly occurred until the deviation of the main river course to its present position. In the lower part of core 12, the strong alternation between coarse and fine sediment textures and the variable amounts of benthic foraminiferal species are interpreted as the result of an active fluvial regime. The upper part, with high percentages of fine sediments and high values of population density, could be attributed to the stabilization of the river course in its present-day location. Core 15, located at 11 m water depth, showed the highest content of gravel in the lower part of the core, high contents of silt at two core depths and increased percentages of sand to the top, indicating the strong influence of human interventions in the river basin and consequent changes in the sediment supply to the Guadalfeo submarine delta.info:eu-repo/semantics/publishedVersio

Multi-proxy evidence of rainfall variability recorded in subaqueous deltaic deposits off the Adra River, southeast Iberian Peninsula

The Adra River deltaic system, southeast Iberian Peninsula, shows a steep topography and is subjected to strong climatic seasonality. This system has been affected by alternating wet and dry periods, and it has also undergone numerous anthropogenic activities such as deforestation, mining activities, river channel deviations and dam construction, particularly during the last two centuries. Two sediment cores were retrieved off the Adra River, from the western (MS_V9) and eastern (MS_V4) lobes of the subaqueous deltaic deposit. A multi-proxy study was carried out, including grain size, benthic foraminiferal assemblages, magnetic susceptibility and geochemical element analyses, in order to understand the sedimentary expression of recent climatic cycles and anthropogenic interventions in the river basin. Periods of increased deposition of coarse-grained sediments, low absolute abundance of benthic foraminifera and high elemental ratios indicative of terrigenous contributions, were interpreted as periods of increased sediment supply to the shelf. Four flooding events were recorded in core MS_V9 and three events on core MS_V4, of which two were observed in both cores. They were related to periods with major floods that were documented on the southern Iberian Peninsula around 1770e1810 and 1860 e1870 AD. On the other hand, sediment core intervals exhibiting increasing proportion of fine-grained sediments and higher abundances of foraminiferal species assigned as successful colonizers (Textularia earlandi) and opportunistic species that feed on bacteria or terrestrial organic matter (Bolivina ordinaria, Bulimina elongata, Eggerelloides scaber and Ammonia beccarii or tepida), indicate the establishment of new environments with new ecological constraints. They were related to significant decreases of terrigenous sediment input during low rainfall or dry periods. The increase of opportunistic species feeding on fresh phytodetritus (Nonionella iridea, Nonionella stella, Nonionella sp., Brizalina dilatata, Epistominella vitrea and Bolivinellina pseudopuntata), under more stable environmental conditions, also point to a stronger marine influence on the prodeltaic environments during these periods. The human interventions on the river basin after 1872 AD, with the deviation of the main river channel to the east, led to a drastic reduction of the sediment exported to the western delta lobe. This study showed that the sedimentation on the Adra subaqueous deltaic deposit was mainly controlled by rainfall variability from 1663 to 1872 AD, and afterwards by anthropogenic interventions.En prensa2,247

Moluscos de hábitats bentónicos del volcán de fango Gazul (Golfo de Cádiz)

Molluscs from the Gazul mud volcano and its adjacent areas in the northern Gulf of Cádiz were studied using differ­ent sampling methods. This mud volcano has vulnerable deep-sea habitats and a potential high biodiversity. A total of 232 species were identified from the taxocoenosis and thanatocoenosis, of which 86 are new records for the Spanish margin of the Gulf of Cádiz, three of them are new records for Spanish waters and two species are new to science. The high species richness observed could be related to the combination of different sampling methods, the study of the thanatocoenosis, the high habitat heterogeneity and the geographical location of the Gazul mud volcano between different biogeographical regions. The best-represented species were Bathyarca philippiana, Asperarca nodulosa, Leptochiton sp., Astarte sulcata and Limopsis angusta. The thanatocoenosis harboured, with low frequency, species that are typical of northern latitudes, species indicating past seepage, species from the shelf and species restricted to particular hosts. The taxocoenosis found in different areas of Gazul (the mud volcano edifice, erosive de­pression and adjacent bottoms) generally displayed significant differences in multivariate analyses. Furthermore, the environmental parameters related to environmental complexity and food availability displayed the highest linkage with the molluscan fauna.Se estudiaron los moluscos del volcán de fango Gazul y sus zonas adyacentes, en el norte del Golfo de Cádiz, utili­zando diferentes métodos de muestreo. Este volcán de fango destaca por la presencia de hábitats vulnerables de aguas profundas y una alta biodiversidad potencial. Se identificaron un total de 232 especies de la taxocenosis y la tanatocenosis, de las cuales 86 son nuevas citas para el margen español del Golfo de Cádiz, tres de ellas son nuevas citas para aguas españolas y dos especies son nuevas para la ciencia. La alta riqueza de especies detectada podría estar relacionada con la combinación de diferentes mé­todos de muestreo, el estudio de la tanatocenosis, la alta heterogeneidad del hábitat y la ubicación geográfica del volcán de fango Gazul entre diferentes regiones biogeográficas. Las especies mejor representadas fueron Bathyarca philippiana, Asperarca nodulosa, Leptochiton sp., Astarte sulcata y Limopsis angusta. La tanatocenosis contenía, con baja frecuencia, especies típicas de latitudes superiores, especies indicadoras de emisiones pasadas, especies de la plataforma y especies restringidas a huéspedes particulares. La taxocenosis encontrada en las diferentes zonas de Gazul (edificio del volcán de fango, depresión erosiva y fon­dos adyacentes) generalmente mostró diferencias significativas en los análisis multivariantes. Además, los parámetros ambien­tales más vinculados con la malacofauna fueron los relacionados con la complejidad ambiental y la disponibilidad de alimento

A dual-band outphasing transmitter using broadband class E power amplifiers

In this paper, a dual-band outphasing transmitter (able of operating either at 770 MHz or 960 MHz frequency bands) is presented. Two broadband RF power amplifiers (PAs) have been designed over packaged GaN HEMT devices, switching close to the nominal zero-voltage and zero-voltage-derivative class E conditions. A reactive combiner, using transmission lines of appropriate electrical lengths at both bands, together with compensating reactances, allows positioning the drain impedance loci to produce high efficiency and good dynamic range profiles. Average drain efficiency figures over 68% and 38% have been measured for WCDMA signals with a peak-to-average power ratio (PAPR) of 5.1 dB and 8.4 dB, respectively.This work was supported by MINECO through projects TEC2011-29126-C03 (-01, co funded with FEDER, and -02), and Consolider CSD2008-00068

Submarine deltaic geometries linked to steep, mountainous drainage basins in the northern shelf of the Alboran Sea: Filling the gaps in the spectrum of deltaic deposition

A comprehensive analysis of small deltaic environments linked to short, mountainous, and seasonal fluvial systems in the northern shelf of the Alboran Sea was undertaken in order to define the controlling parameters of the geomorphological variability. The database includes multibeam and backscatter imagery, surficial sediment samples, and high-resolution seismic profiles. Additionally, geomorphological and hydrodynamic modeling and statistical analysis (principal component and cluster analysis) of hydrological and physiographic variables were performed.Most of the studied deltaic systems have high-gradient, coarse-grained deposits with preferential development of the submarine portions to the detriment of the deltaic plains. The geomorphological analysis identified three basic types of plan-viewdistributions according to the length-to-width ratios: elongate, linguoid and lobate. Cross-slope profiles evidence dominant concave-upward geometries, fewer occurrences of planar geometries, and no sigmoid profiles. Sediment depocenters are extremely thick in proximal locations, but thin out rapidly seawards. The geometric distribution patterns of the deltaic systems are characterized by a predictable pattern in plan-view according to the type of fluvial system, ranging from a relatively large river to ephemeral creeks. Prevailing concave and secondary planar profiles support strong sediment progradation in the submarine realmand lowsediment retention in the emerged deltaic environment. Two different types of systems are distinguished: (1) larger rivers,where deltaic deposition is largely controlled by basin dimensions, ultimately dictating themagnitude of water and sediment discharges; and (2) smaller rivers and creeks,where deltaic geometries are related to the basin slopes. The influence of hydrodynamic variables on defining the submarine deltaic geometry has been observed in the case of concave-upward geometries, where geomorphological boundaries are defined by medium- and high-energy wave conditions.Versión del editor2,520