834 resultados para Lower level relaxation


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In this paper we describe the stratigraphy and sediments deposited in Lake Samra that occupied the Dead Sea basin between ~135 and 75 ka. This information is combined with U/Th dating of primary aragonites in order to estimate a relative lake-level curve that serves as a regional paleohydrological monitor. The lake stood at an elevation of ~340 m below mean sea level (MSL) during most of the last interglacial. This level is relatively higher than the average Holocene Dead Sea (~400±30 m below MSL). At ~120 and ~85 ka, Lake Samra rose to ~320 m below MSL while it dropped to levels lower than ?380 m below MSL at ~135 and ~75 ka, reflecting arid conditions in the drainage area. Lowstands are correlated with warm intervals in the Northern Hemisphere, while minor lake rises are probably related to cold episodes during MIS 5b and MIS 5d. Similar climate relationships are documented for the last glacial highstand Lake Lisan and the lowstand Holocene Dead Sea. Yet, the dominance of detrital calcites and precipitation of travertines in the Dead Sea basin during the last interglacial interval suggest intense pluvial conditions and possible contribution of southern sources of wetness to the region.

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Lower Campanian to middle Eocene chalks and oozes were recovered at Sites 761 and 762 of Ocean Drilling Program Leg 122 on the Exmouth Plateau, northwest Australia. Paleomagnetic analyses were made on 125 samples from Hole 761B and 367 samples from Hole 762C. Thermal cleaning, alternating field demagnetization, or mixed treatment reveals a stable remanent component of normal or reversed polarity. Correlation of the magnetic polarity sequences established for these holes with the standard magnetic polarity time scale was aided by nannofossil zonation. At Hole 761B, the sequence extends from Subchron C32-N (upper Campanian) through Subchron C17-R (middle Eocene), but given the low sedimentation rate, not all the subchrons of the standard magnetic polarity sequence were recognized. The sequence at Hole 762C extends from Subchron C13-R (middle Eocene) to the boundary between Chrons C33 and C34 (lower Campanian). The sedimentation rate is higher at Hole 762C, and all the magnetic polarity subchrons of the Campanian and Maestrichtian stages were identified. Thus, this hole could be a reference section to refine the Upper Cretaceous time scale.

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Biodiversity estimates through geological times are difficult because of taphonomic perturbations that affect sedimentary records. Pristine shell assemblages, however, allow for calibration of past diversity. Diversity structures of two exceptionally preserved Miocene bivalve assemblages are quantitatively determined, compared with recent communities and used as paleoenvironmental proxy. The extremely rich assemblages were collected in Aquitanian (Early Miocene) carbonate sands of the Vives Quarry (Meilhan, SW France). Both paleontological and sedimentological data indicate a coral patch-reef environment, which deposits were affected by transport processes. Among two samples more than 28.000 shells were counted and 135 species identified. Sample Vives 1 is interpreted as a proximal debris flow and Sample Vives 2 as a sandy shoreface/foreshore environment influenced by storms. The two Vives assemblages have a similar diversity structure despite facies differences. Rarefaction curves level off at ~600 shells. The rare species account for more than 80 % of the species pool. The high values of PIE diversity index suggest a relatively high species richness and an even distribution of abundance of the most common species within the assemblages. The fossil data are compared to death shell assemblages (family level) of a modern reefal setting (Touho area, New Caledonia). The shape of the rarefaction curves and PIE indices of Meilhan fossil assemblages compare well to modern data, especially those of deep (>10 m water depth), sandy depositional environments found downward the reef slope (slope and pass settings). In addition to primary ecological signals, the similarity of the Vives samples and the Recent deep samples derives from taphonomic processes. This assumption is supported by sedimentological and paleontological observations. Sediment transports gather allochthonous and in situ materials leading to mixing of various ecological niches. Such taphonomic processes are recorded in the diversity metrics. Environmental mixing and time-averaging of the shell assemblages disturb the preservation of local-scale diversity properties but favour the sampling of the regional-scale diversity.

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The oxygen isotope record of the planktonic foraminifera Globigerina bulloides and Neogloboquadrina pachyderma from Pliocene and early Pleistocene sediments at both DSDP site 173 and the Centerville Beach section in California suggests a large influx of isotopically light water in this area during late Pliocene and early Pleistocene time. Salinity may have been reduced by as much as 2 to 4 ?. Surface sea water paleotemperatures for the lower Pliocene range from 9.5°C to 15.5°C. The oxygen isotope record of the benthonic genus Uvigerina shows little variation indicating environmental stability at depth. At DSDP site 173 the small variation in Uvigerina is due to variation in the oxygen isotopic composition of the oceans as glaciers waxed and waned. At the Centerville Beach section the oxygen isotopic composition of Uvigerina reflects the gradual shoaling of the Humboldt Basin. Carbon and oxygen isotope ratios in G. bulloides and N. pachyderma are inversely correlated at the 95% confidence level. This may indicate that the oxygen and carbon isotopic composition of foraminifera are influenced by the same factors. On the other hand, the inverse correlation may be due to metabolic fractionation. No correlation was found between oxygen and carbon isotopic composition in Uvigerina.

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The course of sea-level fluctuations during Termination II (TII; the penultimate deglaciation), which is critical for understanding ice-sheet dynamics and suborbital climate variability, has yet to be established. This is partly because most shallow-water sequences encompassing TII were eroded during sea-level lowstands of the last glacial period or were deposited below the present sea level. Here we report a new sequence recording sea-level changes during TII in the Pleistocene sequence at Hole M0005D (water depth: 59.63 m below sea level [mbsl]) off Tahiti, French Polynesia, which was drilled during Integrated Ocean Drilling Program Expedition 310. Lithofacies variations and stratigraphic changes in the taxonomic composition, preservation states, and intraspecific test morphology of large benthic foraminifers indicate a deepening-upward sequence in the interval from Core 310-M0005D-26R (core depth: 134 mbsl) through -16R (core depth: 106 mbsl). Reconstruction of relative sea levels, based on paleodepth estimations using large benthic foraminifers, indicated a rise in sea level of about 90 m during this interval, suggesting its correlation with one of the terminations. Assuming that this rise in sea level corresponds to that during TII, after correcting for subsidence since the time of deposition, a highstand sea-level position would be 2 ± 15 m above present sea level (masl), which is generally consistent with highstand sea-level positions in MIS 5e (4 ± 2 masl). If this rise in sea level corresponds to that during older terminations, the subsidence-corrected highstand sea-level positions (30 ± 15 masl for Termination III and 54 ± 15 masl for Termination IV) are not consistent with reported ranges of interglacial sea-level highstands (-18 to 15 masl). Therefore, the studied interval likely records the rise in sea level and associated environmental changes during TII. In particular, the intervening cored materials between the two episodes of sea-level rise found in the studied interval might record the sea-level reversal event during TII. This conclusion is consistent with U/Th ages of around 133 ka, which were obtained from slightly diagenetically altered (i.e., < 1% calcite) in situ corals in the studied interval (Core 310-M0005D-20R [core depth: 118 mbsl]). This study also suggests that our inverse approach to correlate a stratigraphic interval with an approximate time frame could be useful as an independent check on the accuracy of uranium-series dating, which has been applied extensively to fossil corals in late Quaternary sea-level studies.

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During the mid-Pleistocene transition the dominant 41 ka periodicity of glacial cycles transitioned to a quasi-100 ka periodicity for reasons not yet known. This study investigates the potential role of deep ocean hydrography by examining oxygen isotope ratios in benthic foraminifera. Oxygen isotope records from the Atlantic, Pacific and Indian Ocean basins are separated into their ice volume and local temperature/hydrography components using a piece-wise linear transfer function and a temperature calibration. Although our method has certain limitations, the deep ocean hydrography reconstructions show that glacial deep ocean temperatures approached freezing point as the mid-Pleistocene transition progressed. Further analysis suggests that water mass reorganisation could have been responsible for these temperature changes, leading to such stable conditions in the deep ocean that some obliquity cycles were skipped until precessional forcing triggered deglaciation, creating the apparent quasi-100 ka pattern. This study supports previous work that suggests multiples of obliquity cycles dominate the quasi-100 ka glacial cycles with precession components driving deglaciations.

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During the past five million yrs, benthic d18O records indicate a large range of climates, from warmer than today during the Pliocene Warm Period to considerably colder during glacials. Antarctic ice cores have revealed Pleistocene glacial-interglacial CO2 variability of 60-100 ppm, while sea level fluctuations of typically 125 m are documented by proxy data. However, in the pre-ice core period, CO2 and sea level proxy data are scarce and there is disagreement between different proxies and different records of the same proxy. This hampers comprehensive understanding of the long-term relations between CO2, sea level and climate. Here, we drive a coupled climate-ice sheet model over the past five million years, inversely forced by a stacked benthic d18O record. We obtain continuous simulations of benthic d18O, sea level and CO2 that are mutually consistent. Our model shows CO2 concentrations of 300 to 470 ppm during the Early Pliocene. Furthermore, we simulate strong CO2 variability during the Pliocene and Early Pleistocene. These features are broadly supported by existing and new d11B-based proxy CO2 data, but less by alkenone-based records. The simulated concentrations and variations therein are larger than expected from global mean temperature changes. Our findings thus suggest a smaller Earth System Sensitivity than previously thought. This is explained by a more restricted role of land ice variability in the Pliocene. The largest uncertainty in our simulation arises from the mass balance formulation of East Antarctica, which governs the variability in sea level, but only modestly affects the modeled CO2 concentrations.

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There is a large and growing empirical literature that investigates the determinants of outward foreign direct investment (FDI). This literature examines primarily the effect of host country characteristics on FDI even though home country characteristics also influence the decision of firms to invest abroad. In this paper, we examine the role of both host and home country characteristics in FDI. To do so, we constructed a firm-level database of outward FDI from Japan, Korea, and Taiwan. Our empirical analysis yields two main findings. First, host countries with better environment for FDI, in terms of larger market size, smaller fixed entry costs, and lower wages, attract more foreign investors. Second, firms from home countries with higher wages are more likely to invest abroad. An interesting and significant policy implication of our empirical evidence is that policymakers seeking to promote FDI inflows should prioritize countries with higher wages.

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In this paper, we explore the firm-level impacts of flooding in Thailand in 2011, specifically those on the procurement patterns at Japanese affiliates in Thailand. Our findings are as follow. First, the damaged small firms are more likely to lower their local procurement share, particularly the share of procurement from other Japanese-owned firms in Thailand. Second, damaged young firms and damaged old firms are more likely to raise the shares of imports from Japan and China, respectively. Third, there are no impacts on imports from ASEAN and other countries. These findings are useful for uncovering how multinational firms adjust their production networks before and after natural disasters.

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International production fragmentation has been a global trend for decades, becoming especially important in Asia where the manufacturing process is fragmented into stages and dispersed around the region. This paper examines the effects of input and output tariff reductions on labor demand elasticities at the firm level. For this purpose, we consider a simple heterogenous firm model in which firms are allowed to export their products and to use imported intermediate inputs. The model predicts that only productive firms can use imported intermediate inputs (outsourcing) and tend to have larger constant-output labor demand elasticities. Input tariff reductions would lower the factor shares of labor for these productive firms and raise conditional labor demand elasticities further. We test these empirical predictions, constructing Chinese firm-level panel data over the 2000--2006 period. Controlling for potential tariff endogeneity by instruments, our empirical studies generally support these predictions.

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In this study, we examine the effects of tariff reduction on firms' quality upgrading by employing an Indonesian plant-product-level panel dataset matched with a plant-level dataset. We explore the effects of lower output and input tariffs separately, by focusing on the apparel industry. By estimating the Berry-type demand function, we derive product-quality indicators based on the Khandelwal (Review of Economic Studies, 2010) methodology, which enables us to isolate quality upgrading from changes in prices. Our findings are as follows. First, a reduction in output tariffs does not affect product quality upgrading. Second, a reduction in input tariffs boosts quality upgrading in general. In particular, this impact is greater for import firms, which is consistent with the fact that the source of the boost is the import of high-quality foreign inputs.

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La Tesis Doctoral nace con una intensa vocación pedagógica. La hipótesis de trabajo se establece en torno a una cuestión de interés personal, un tema sobre el que se vertebran, desde el comienzo del doctorado, los diferentes cursos y trabajos de investigación: LA CASA DOMÍNGUEZ como paradigma de la dialéctica en la obra de Alejandro de la Sota. La clasificación de la realidad en categorías antagónicas determina un orden conceptual polarizado, una red de filiaciones excluyentes sobre las que Sota construye su personal protocolo operativo: la arquitectura intelectual o popular, experimental o tradicional, universal o local, ligera o pesada, elevada o enterrada, etc. Se propone el abordaje de una cuestión latente en el conjunto de la obra ‘sotiana’, desde la disección y el análisis de una de sus obras más pequeñas: la casa Domínguez. Se trata de una organización sin precedentes, que eleva la estrategia dialéctica al paroxismo: la vivienda se separa en dos estratos independientes, la zona de día, elevada, y la zona de noche, enterrada; cada uno de los estratos establece su propio orden geométrico y constructivo, su propio lenguaje y carácter, su propia identidad e incluso su propio presupuesto. Las relaciones entre interior y exterior se especializan en función de la actividad o el reposo, estableciéndose una compleja red de relaciones, algunas evidentes y otras celosamente veladas, entre los diferentes niveles. La estancia destinada a las tareas activas se proyecta como un objeto de armazón ligero y piel fría; la precisa geometría del cubo delimita la estancia vigilante sobre el paisaje conquistado. La ladera habitada se destina al reposo y se configura como una topografía verde bajo la que se desarrollan los dormitorios en torno a patios, grietas y lucernarios, generando un paisaje propio: la construcción del objeto frente a la construcción del lugar La casa Domínguez constituye uno de los proyectos menos estudiados, y por lo tanto menos celebrados, de la obra de Don Alejandro. Las publicaciones sucesivas reproducen la documentación gráfica junto a la memoria (epopeya) que el propio Sota compone para la publicación del proyecto. Apenas un par de breves textos críticos de Miguel Ángel Baldellou y, recientemente de Moisés Puente, abordan la vivienda como tema monográfico. Sin embargo, la producción de proyecto y obra ocupó a De la Sota un periodo no inferior a diez años, con casi cien planos dibujados para dos versiones de proyecto, la primera de ellas, inédita. El empeño por determinar hasta el último detalle de la ‘pequeña’ obra, conduce a Sota a controlar incluso el mobiliario interior, como hiciera en otras obras ‘importantes’ como el Gobierno Civil de Tarragona, el colegio mayor César Carlos o el edificio de Correos y Telecomunicaciones de León. La complicidad del cliente, mantenida durante casi cuarenta años, habilita el despliegue de una importante colección de recursos y herramientas de proyecto. La elección de la casa Domínguez como tema central de la tesis persigue por lo tanto un triple objetivo: en primer lugar, el abordaje del proyecto como paradigma de la dialéctica ‘sotiana’, analizando la coherencia entre el discurso de carácter heroico y la obra finalmente construida; en segundo lugar, la investigación rigurosa, de corte científico, desde la disección y progresivo desmontaje del objeto arquitectónico; y por último, la reflexión sobre los temas y dispositivos de proyecto que codifican la identificación entre la acción de construir y el hecho de habitar, registrando los aciertos y valorando con actitud crítica aquellos elementos poco coherentes con el orden interno de la propuesta. This doctoral thesis is the fruit of a profound pedagogical vocation. The central hypothesis was inspired by a question of great personal interest, and this interest has, since the very beginning of the doctorate, been the driving force behind all subsequent lines of research and investigation. The “Casa Domínguez” represents a paradigm of the dialectics found in the work of Alejandro de la Sota. The perception of reality as antagonistic categories determines a polarized conceptual order, a network of mutually excluding associations upon which Sota builds his own personal operative protocol: intellectual or popular architecture, experimental or traditional, universal or local, heavy or light, above or below ground, etc. Through the analysis and dissection of the “Casa Domínguez”, one of Sota’s smallest projects, an attempt is made to approach the underlying question posed in “Sotian” work as a whole. This is about organization without precedent, raising the strategic dialectics to levels of paroxysm. The house is divided into two separate levels, the day-time level above ground, and the lower night-time level beneath the surface of the ground. Each level has its own geometrical and stuctural order, its own language and character, its own identity and even has its own construction budget. The interaction between the two areas is centered on the two functions of rest and activity, and this in turn establishes a complex relationship network between both, which is sometimes self-evident, but at other times jealously guarded. The living area designed for daily activity is presented as an object of light structure and delicate skin; the precise geometry of the cube delimiting the ever watchful living area’s domain over the land it has conquered. A green topography is created on the slope below which lies an area adapted for rest and relaxation. Two bedrooms, built around patios, skylights and light crevices, generate an entirely independent environment: the construction of an object as opposed to the creation of a landscape. The “Casa Domínguez” project has been subject to much less scrutiny and examination than Don Alejandro’s other works, and is consequently less well-known. A succession of journals have printed the blueprint document together with a poetic description (epopee), composed by Sota himself, to mark the project’s publication. There has, however, scarcely been more than two brief critical appraisals, those by Miguel Ángel Baldellou and more recently by Moisés Puente, that have regarded the project as a monographic work. The project and works nevertheless occupied no less than ten years of De La Sota’s life, with over a hundred draft drawings for two separate versions of the project, the first of which remains unpublished. The sheer determination to design this “small” work in the most meticulous detail, drove Sota to manage and select its interior furniture, as indeed he had previously done with more “important” works like the Tarragona Civil Government, César Carlos College, or the Post Office telecommunications building in León. Client collaboration, maintained over a period of almost forty years, has facilitated an impressive array of the project’s tools and resources. The choice of “Casa Domínguez” as the central subject matter of this thesis, was made in pursuance of a triple objective: firstly, to approach the project as a paradigm of the “Sotian” dialectic, the analysis of the discourse between the heroic character and the finished building; secondly, a rigorous scientific investigation, and progressive disassembling and dissecting of the architectonic object; and finally, a reflection on aspects of the project and its technology which codify the identification between the action of construction and the reality of living, thus marking its achievements, whilst at the same time subjecting incoherent elements of the proposal’s established order to a critical evaluation.

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This research studied the effects of additional fiber in the rearing phase diets on egg production, gastrointestinal tract (GIT) traits, and body measurements of brown egg-laying hens fed diets varying in energy concentration from 17 to 46 wk of age. The experiment was completely randomized with 10 treatments arranged as a 5 × 2 factorial with 5 rearing phase diets and 2 laying phase diets. During the rearing phase, treatments consisted of a control diet based on cereals and soybean meal and 4 additional diets with a combination of 2 fiber sources (cereal straw and sugar beet pulp, SBP) at 2 levels (2 and 4%). During the laying phase, diets differed in energy content (2,650 vs. 2,750 kcal AMEn/kg) but had the same amino acid content per unit of energy. The rearing diet did not affect any production trait except egg production that was lower in birds fed SBP than in birds fed straw (91.6 and 94.1%, respectively; P < 0.05). Laying hens fed the high energy diet had lower feed intake (P < 0.001), better feed conversion (P < 0.01), and greater BW gain (P < 0.05) than hens fed the low energy diet but egg production and egg weight were not affected. At 46 wk of age, none of the GIT traits was affected by previous dietary treatment. At this age, hen BW was positively related with body length (r = 0.500; P < 0.01), tarsus length (r = 0.758; P < 0.001), and body mass index (r = 0.762; P < 0.001) but no effects of type of diet on these traits were detected. In summary, the inclusion of up to 4% of a fiber source in the rearing diets did not affect GIT development of the hens but SBP reduced egg production. An increase in the energy content of the laying phase diet reduced ADFI and improved feed efficiency but did not affect any of the other traits studied.

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The nuclear spin polarization of 129Xe can be enhanced by several orders of magnitude by using optical pumping techniques. The increased sensitivity of xenon NMR has allowed imaging of lungs as well as other in vivo applications. The most critical parameter for efficient delivery of laser-polarized xenon to blood and tissues is the spin-lattice relaxation time (T1) of xenon in blood. In this work, the relaxation of laser-polarized xenon in human blood is measured in vitro as a function of blood oxygenation. Interactions with dissolved oxygen and with deoxyhemoglobin are found to contribute to the spin-lattice relaxation time of 129Xe in blood, the latter interaction having greater effect. Consequently, relaxation times of 129Xe in deoxygenated blood are shorter than in oxygenated blood. In samples with oxygenation equivalent to arterial and venous blood, the 129Xe T1s at 37°C and a magnetic field of 1.5 T were 6.4 s ± 0.5 s and 4.0 s ± 0.4 s, respectively. The 129Xe spin-lattice relaxation time in blood decreases at lower temperatures, but the ratio of T1 in oxygenated blood to that in deoxygenated blood is the same at 37°C and 25°C. A competing ligand has been used to show that xenon binding to albumin contributes to the 129Xe spin-lattice relaxation in blood plasma. This technique is promising for the study of xenon interactions with macromolecules.