746 resultados para Alluvial fans


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We appreciate very helpful reviews by Dr. Martin Stokes and three anonymous reviewers and editor Dr. Richard Marston. We also appreciate the encouragement for writing this paper from Dr. Timothy Horscroft. We acknowledge support of the sponsors of the Fluvial Systems Research Group consortium, BP, BG, Chevron, ConocoPhillips and Total.

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We appreciate very helpful reviews by Dr. Martin Stokes and three anonymous reviewers and editor Dr. Richard Marston. We also appreciate the encouragement for writing this paper from Dr. Timothy Horscroft. We acknowledge support of the sponsors of the Fluvial Systems Research Group consortium, BP, BG, Chevron, ConocoPhillips and Total.

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Les polygones à coin de glace sont très répandus dans la zone du pergélisol continu. Lorsque le ruissellement d’eau de fonte nivale s’infiltre de façon concentrée dans une cavité, il peut initier le processus de thermo-érosion du pergélisol (notamment des coins de glace) pouvant mener à la formation de ravins. Dans la vallée de Qalikturvik sur l’Ile Bylot (NU, Canada), le développement de ravins de thermo-érosion dans un milieu de polygones à coins de glace entraîne comme impact : i. la réorganisation des réseaux de drainage impliquant un assèchement des milieux humides en marge des chenaux d’érosion, ii. des variations dans le régime thermique et de l’humidité de proche-surface et iii. la prise en charge et le déplacement des sédiments vers l’extérieur du bassin-versant. L’objectif de cette thèse vise à approfondir les connaissances géomorphologiques propres au ravinement par thermo-érosion, d’examiner, caractériser et quantifier les impacts du ravinement (tel que sus-mentionné en i. ii. iii.) et le rôle de celui-ci dans une optique d’évolution du paysage périglaciaire à l’échelle temporelle de l’année à la décennie. Les ravins sont dynamiques : un ravin en particulier déclenché en 1999 et étudié depuis s’érodait à une vitesse de 38 à 50 m/a durant sa première décennie d’existence, pour atteindre une longueur totale de ~750 m et une surface érodée de ~25 000 m² en 2009. Des puits sont localisés près des zones de ravinement actives ; des levées alluviale, mares et polygones effondrés dans les zones stabilisées post-perturbation. Sur la terrasse de polygones recouvrant le plancher de la vallée au site à l’étude, 35 ravins furent identifiés et 1401 polygones furent perturbés avec 200 000 m³ de sols transportés. Une amélioration du drainage, une dégradation de la capacité de rétention de l’humidité, une transition d’un écoulement de ruissellement vers un écoulement canalisé caractérise les aires ravinées et leurs environs. Les polygones intacts sont homogènes d’un à l’autre et dans leurs centres ; les polygones perturbés ont une réponse hétérogène (flore, humidité et régime thermique). Les milieux érodés hétérogènes succèdent aux milieux homogènes et deviennent le nouvel état d’équilibre pour plusieurs décennies.

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With the introduction of new input devices, such as multi-touch surface displays, the Nintendo WiiMote, the Microsoft Kinect, and the Leap Motion sensor, among others, the field of Human-Computer Interaction (HCI) finds itself at an important crossroads that requires solving new challenges. Given the amount of three-dimensional (3D) data available today, 3D navigation plays an important role in 3D User Interfaces (3DUI). This dissertation deals with multi-touch, 3D navigation, and how users can explore 3D virtual worlds using a multi-touch, non-stereo, desktop display. The contributions of this dissertation include a feature-extraction algorithm for multi-touch displays (FETOUCH), a multi-touch and gyroscope interaction technique (GyroTouch), a theoretical model for multi-touch interaction using high-level Petri Nets (PeNTa), an algorithm to resolve ambiguities in the multi-touch gesture classification process (Yield), a proposed technique for navigational experiments (FaNS), a proposed gesture (Hold-and-Roll), and an experiment prototype for 3D navigation (3DNav). The verification experiment for 3DNav was conducted with 30 human-subjects of both genders. The experiment used the 3DNav prototype to present a pseudo-universe, where each user was required to find five objects using the multi-touch display and five objects using a game controller (GamePad). For the multi-touch display, 3DNav used a commercial library called GestureWorks in conjunction with Yield to resolve the ambiguity posed by the multiplicity of gestures reported by the initial classification. The experiment compared both devices. The task completion time with multi-touch was slightly shorter, but the difference was not statistically significant. The design of experiment also included an equation that determined the level of video game console expertise of the subjects, which was used to break down users into two groups: casual users and experienced users. The study found that experienced gamers performed significantly faster with the GamePad than casual users. When looking at the groups separately, casual gamers performed significantly better using the multi-touch display, compared to the GamePad. Additional results are found in this dissertation.

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El 30 de diciembre último se ha producido en la Ciudad de Buenos Aires un hecho que sacudió al país: el incendió de un boliche de rock en el que murieron, hasta hoy, 195 personas. Inmediatamente se desencadeno la batalla por desentrañar lo sucedido y señalar al culpable. Los medios de comunicación, los intelectuales, los músicos, los partidos políticos y las propias víctimas fueron parte de esta batalla. Los culpables se fueron sucediendo, desde los funcionarios públicos y el dueño del boliche (Ibarra y Chabán), hasta las propias víctimas (el público, los fans de rock, el chico que prendió la bengala). En el medio, la banda que tocaba esa noche, Callejeros y detrás de ella la cultura rock. La intención de la presente ponencia es indagar en el análisis de las fortalezas y debilidades de cada una de las explicaciones del hecho, cada cual con su culpable señalado. Su intención es también indagar sobre el origen y los intereses sociales que se esconden detrás de cada una de las diferentes explicaciones. Por último intentaremos brindar, a partir de este análisis cual es la mejor forma de caracterizar lo sucedido. ¿Es Cromañón una tragedia, una masacre o un crimen social?

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El 30 de diciembre último se ha producido en la Ciudad de Buenos Aires un hecho que sacudió al país: el incendió de un boliche de rock en el que murieron, hasta hoy, 195 personas. Inmediatamente se desencadeno la batalla por desentrañar lo sucedido y señalar al culpable. Los medios de comunicación, los intelectuales, los músicos, los partidos políticos y las propias víctimas fueron parte de esta batalla. Los culpables se fueron sucediendo, desde los funcionarios públicos y el dueño del boliche (Ibarra y Chabán), hasta las propias víctimas (el público, los fans de rock, el chico que prendió la bengala). En el medio, la banda que tocaba esa noche, Callejeros y detrás de ella la cultura rock. La intención de la presente ponencia es indagar en el análisis de las fortalezas y debilidades de cada una de las explicaciones del hecho, cada cual con su culpable señalado. Su intención es también indagar sobre el origen y los intereses sociales que se esconden detrás de cada una de las diferentes explicaciones. Por último intentaremos brindar, a partir de este análisis cual es la mejor forma de caracterizar lo sucedido. ¿Es Cromañón una tragedia, una masacre o un crimen social?

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El 30 de diciembre último se ha producido en la Ciudad de Buenos Aires un hecho que sacudió al país: el incendió de un boliche de rock en el que murieron, hasta hoy, 195 personas. Inmediatamente se desencadeno la batalla por desentrañar lo sucedido y señalar al culpable. Los medios de comunicación, los intelectuales, los músicos, los partidos políticos y las propias víctimas fueron parte de esta batalla. Los culpables se fueron sucediendo, desde los funcionarios públicos y el dueño del boliche (Ibarra y Chabán), hasta las propias víctimas (el público, los fans de rock, el chico que prendió la bengala). En el medio, la banda que tocaba esa noche, Callejeros y detrás de ella la cultura rock. La intención de la presente ponencia es indagar en el análisis de las fortalezas y debilidades de cada una de las explicaciones del hecho, cada cual con su culpable señalado. Su intención es también indagar sobre el origen y los intereses sociales que se esconden detrás de cada una de las diferentes explicaciones. Por último intentaremos brindar, a partir de este análisis cual es la mejor forma de caracterizar lo sucedido. ¿Es Cromañón una tragedia, una masacre o un crimen social?

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To project the future development of the soil organic carbon (SOC) storage in permafrost environments, the spatial and vertical distribution of key soil properties and their landscape controls needs to be understood. This article reports findings from the Arctic Lena River Delta where we sampled 50 soil pedons. These were classified according to the U.S.D.A. Soil Taxonomy and fall mostly into the Gelisol soil order used for permafrost-affected soils. Soil profiles have been sampled for the active layer (mean depth 58±10 cm) and the upper permafrost to one meter depth. We analyze SOC stocks and key soil properties, i.e. C%, N%, C/N, bulk density, visible ice and water content. These are compared for different landscape groupings of pedons according to geomorphology, soil and land cover and for different vertical depth increments. High vertical resolution plots are used to understand soil development. These show that SOC storage can be highly variable with depth. We recommend the treatment of permafrost-affected soils according to subdivisions into: the surface organic layer, mineral subsoil in the active layer, organic enriched cryoturbated or buried horizons and the mineral subsoil in the permafrost. The major geomorphological units of a subregion of the Lena River Delta were mapped with a land form classification using a data-fusion approach of optical satellite imagery and digital elevation data to upscale SOC storage. Landscape mean SOC storage is estimated to 19.2±2.0 kg C/m**2. Our results show that the geomorphological setting explains more soil variability than soil taxonomy classes or vegetation cover. The soils from the oldest, Pleistocene aged, unit of the delta store the highest amount of SOC per m**2 followed by the Holocene river terrace. The Pleistocene terrace affected by thermal-degradation, the recent floodplain and bare alluvial sediments store considerably less SOC in descending order.

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A 20 kyr long sediment sequence from the Congo deep sea fan (core GeoB 6518-1), one of the world's largest deep sea river fans, has been analysed for bulk and molecular proxies in order to reconstruct the marine, soil and plant organic carbon (OC) contributions to these sediments since the last glacial maximum. The bulk proxies applied, C/N ratio and d13Corg, ranged from 10 to 12.5 and from -24.5 to -21 per mill VPDB, respectively. As molecular proxies, concentrations of marine derived alkenones and terrestrial derived odd-numbered n-alkanes were used, which varied between 0.2 and 4 µg/g dry weight sediment. In addition, the branched vs. isoprenoid tetraether (BIT) index, a proxy for soil organic matter input, was used, which varied from 0.3 to 0.5 in this core. Application of binary mixing models, based on the different individual proxies, showed estimates for terrestrial OC input varying by up to 50% due to the heterogeneous nature of the OC. Application of a three end-member mixing model using the d13Corg content, the C/N ratio and the BIT index, enabled the distinction of soil and plant organic matter as separate contributors to the sedimentary OC pool. The results show that marine OC accounts for 20% to 40% of the total OC present in the deep sea fan sediments over the last 20 kyr and that soil OC accounts for about half (45% on average) of the OC present. This suggests that soil OC represents the majority of the terrestrial OC delivered to the fan sediments. Accumulation rates of the plant and soil OC fractions over the last 20 kyr varied by a factor of up to 5, and are strongly related to sediment accumulation rates. They showed an increase starting at ca. 17 kyr BP, a decline during the Younger Dryas, peak values during the early Holocene and lower values in the late Holocene. This pattern matches with reconstructions of past central African humidity and Congo River discharge from the same core and revealed that central African precipitation patterns exert a dominant control on terrestrial OC deposition in the Congo deep sea fan. Marine OC accumulation rates are only weakly related to sediment accumulation rates and vary only little over time compared to the terrigenous fractions. These variations are likely a result of enhanced preservation during times of higher sedimentation rates and of relative small fluctuations in primary production due to wind-driven upwelling.

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The combination of permafrost history and dynamics, lake level changes and the tectonical framework is considered to play a crucial role for sediment delivery to El'gygytgyn Crater Lake, NE Russian Arctic. The purpose of this study is to propose a depositional framework based on analyses of the core strata from the lake margin and historical reconstructions from various studies at the site. A sedimentological program has been conducted using frozen core samples from the 141.5 m long El'gygytgyn 5011-3 permafrost well. The drill site is located in sedimentary permafrost west of the lake that partly fills the El'gygytgyn Crater. The total core sequence is interpreted as strata building up a progradational alluvial fan delta. Four macroscopically distinct sedimentary units are identified. Unit 1 (141.5-117.0 m) is comprised of ice-cemented, matrix-supported sandy gravel and intercalated sandy layers. Sandy layers represent sediments which rained out as particles in the deeper part of the water column under highly energetic conditions. Unit 2 (117.0-24.25 m) is dominated by ice-cemented, matrix-supported sandy gravel with individual gravel layers. Most of the Unit 2 diamicton is understood to result from alluvial wash and subsequent gravitational sliding of coarse-grained (sandy gravel) material on the basin slope. Unit 3 (24.25-8.5 m) has ice-cemented, matrix-supported sandy gravel that is interrupted by sand beds. These sandy beds are associated with flooding events and represent near-shore sandy shoals. Unit 4 (8.5-0.0 m) is ice-cemented, matrix-supported sandy gravel with varying ice content, mostly higher than below. It consists of slope material and creek fill deposits. The uppermost metre is the active layer (i.e. the top layer of soil with seasonal freeze and thaw) into which modern soil organic matter has been incorporated. The nature of the progradational sediment transport taking place from the western and northern crater margins may be related to the complementary occurrence of frequent turbiditic layers in the central lake basin, as is known from the lake sediment record. Slope processes such as gravitational sliding and sheet flooding occur especially during spring melt and promote mass wasting into the basin. Tectonics are inferred to have initiated the fan accumulation in the first place and possibly the off-centre displacement of the crater lake.

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The article is based fundamentally on the authors' participation in the International Conference “I’ll See You Again in 25 Years: The return of Twin Peaks and generations of cult TV”, held on 21 and 22 May 2015, at the School of Arts and Media, at the University of Salford in England. Starting from there, it makes an irregular discussion of issues and working angles around the television series launched in 1990, a work by David Lynch and Mark Frost. Some issues gain particular attention: 1) the relations of the series to the album Outside (1995) by David Bowie; 2) the population of adult toys related to the series, as derivative products, driven by fans in their most playful exercises of affection and remembrance. Despite the article’s intentionally adopted tone of an “academic report”, it can evoke rich theoretical questions in a field of objects that are in a complex upgrade process and have to be subsequently treated according to more regular methodological procedures, seeking further theoretical and epistemological clarifications

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Ticket distribution channels for live music events have been revolutionised through the increased take-up of internet technologies, and the music supply-chain has evolved into a multi-channel value network. The assumption that this creates increased consumer autonomy and improved service quality is explored here through a case-study of the ticket pre-sale for the US leg of the Depeche Mode 2005–06 World Tour, which utilises an innovative virtual channel strategy, promoted as a service to loyal fans. A multi-method analysis, adopting Kozinets' (2002) Kozinets, R. V. 2002. The field behind the screen: using netnography for marketing research in online communities. Journal of Marketing Research, 39: 61–72. [CrossRef], [Web of Science ®] netnography methodology, is employed to map responses of the band's serious fan base on an internet message board (IMB) throughout the tour pre-sale. The analysis focuses on concerns of pricing, ethics, scope of the offer, use of technology, service quality and perceived brand performance fit of channel partners. Findings indicate that fans behaviour is unpredictable in response to channel partners' performance, and that such offers need careful management to avoid alienation of loyal consumers.

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Mineral and chemical composition of alluvial Upper-Pleistocene deposits from the Alto Guadalquivir Basin (SE Spain) were studied as a tool to identify sedimentary and geomorphological processes controlling its formation. Sediments located upstream, in the north-eastern sector of the basin, are rich in dolomite, illite, MgO and KB2BO. Downstream, sediments at the sequence base are enriched in calcite, smectite and CaO, whereas the upper sediments have similar features to those from upstream. Elevated rare-earth elements (REE) values can be related to low carbonate content in the sediments and the increase of silicate material produced and concentrated during soil formation processes in the neighbouring source areas. Two mineralogical and geochemical signatures related to different sediment source areas were identified. Basal levels were deposited during a predominantly erosive initial stage, and are mainly composed of calcite and smectite materials enriched in REE coming from Neogene marls and limestones. Then the deposition of the upper levels of the alluvial sequences, made of dolomite and illitic materials depleted in REE coming from the surrounding Sierra de Cazorla area took place during a less erosive later stage of the fluvial system. Such modification was responsible of the change in the mineralogical and geochemical composition of the alluvial sediments.

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Las relaciones públicas se configuran como una actividad esencial en la gestión de la comunicación con los públicos de los clubes de fútbol ya que son muy activos y su grado de reactividad es alto. Con este texto se analiza el papel que desempeñan las redes sociales en los clubes de fútbol que poseen mayor número de ingresos. Para ello, se desarrolla una metodología que estudia qué presencia tienen en las redes sociales, el número de seguidores, qué grado de interacción se produce entre clubes y públicos y los contenidos y las temáticas de los textos de las redes sociales. Los resultados muestran un público activo pero con intervenciones relacionadas con los resultados futbolísticos y una gestión comunicativa unidireccional por parte de los clubes.

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En este trabajo se calcula la tasa media de incisión fluvial del río Darro (Granada, España) durante el periodo 1890-2010 en su tramo urbano (sector Alhambra-Valparaíso). Para ello se han utilizado fotografías históricas en las que aparece dicho río, a partir de las cuales se ha podido determinar la posición del cauce en el momento en el que se realizaron las fotografías. La comparación con los escenarios actuales de tales imágenes ha permitido determinar la diferencia de altura del cauce a través de medidas de cotas absolutas realizadas mediante teodolito. Esta metodología ha permitido estimar de modo cuantitativo un índice de encajamiento vertical medio del río de 1,05 cm/año para el periodo histórico considerado.