998 resultados para messut - 1300-1400-luku
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Includes bibliographical references (p. 490-505) and indexes.
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A controlled crossover experimental design was used to determine the effect of altered water sprinkling duration on heifers subjected to heat stress conditions. Heifers were subjected to 3 days of thermoneutral conditions followed by 3 days of hot conditions accompanied by water sprinkling between 1300 and 1500 h (HOT1-3). Then on the following 2 days (HOT4-5), environmental conditions remained similar, but 3 heifers were sprinkled between 1200 and 1600 h ( WET) and 3 were not sprinkled (NONWET). This was followed by a 1-day period (HOT6) in which environmental conditions and sprinkling regimen were similar to HOT1-3. Rectal temperature (RT) was collected hourly, and respiration rate (RR) was monitored every 2 h on HOT Days 2, 4, 5, and 6. Dry matter intake and rate of eating were also determined. Sprinkling reduced RR and RT (P < 0.01) of all heifers during HOT1-3. During HOT4-5, WET heifers had lower (P < 0.05) RT than NONWET from 1300 to 700 h and lower RR from 1400 to 2000 h. Dry matter intake of NONWET heifers was reduced by 30.6% (P < 0.05) during HOT4-5 and by 51.2% on HOT6. On HOT4-5 the dry matter intakes of WET heifers were similar to intakes under thermoneutral conditions. During HOT6, RT was again reduced following sprinkling in all heifers. Comparison of RT and RR of NONWET and WET heifers on HOT1-3 v. HOT6 revealed that under similar environmental conditions, NONWET heifers had increased RT, partially due to carry-over from HOT4-5. However, NONWET heifers had 40% lower feed intake but tended to have lower RR on HOT6 v. HOT1-3. Only RR of WET heifers was greater on HOT6, possibly a result of switching from a 4-h back to a 2-h sprinkling period, while maintaining a 62% greater intake (5.80 v. 3.58 kg/day) than NONWET heifers during this time. Results suggest that inconsistent cooling regimens may increase the susceptibility of cattle to heat stress and elicit different physiological and metabolic responses.
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Mudrocks and carbonates of the Isa superbasin in the Lawn Hill platform in northern Australia host major base metal sulfide mineralization, including the giant strata-bound Century Zn-Pb deposit. Mineral paragenesis, stable isotope, and K-Ar dating studies demonstrate that long-lived structures such as the Termite Range fault acted as hot fluid conduits several times during the Paleoproterozoic and Mesoproterozoic in response to major tectonic events. Illite and chlorite crystallinity studies suggest the southern part of the platform has experienced higher temperatures (up to 300 degrees C) than similar stratigraphic horizons in the north. The irregular downhole variation of illite crystallinity values provides further information oil the thermal regime in the basin and shows that clay formation was controlled not only by temperature increase with depth but also by high water/rock ratios along relatively permeable zones. K-Ar dating of illite, in combination with other data, may indicate three major thermal events in the central and northern Lawn Hill platform Lit 1500, 1440 to 1400, and 1250 to 1150 Ma. This study did not detect the earlier Century base metal mineralizing event at 1575 Ma. 1500 Ma ages are recorded only in the south and correspond to the age of the Late Isan orogeny and deposition of the Lower Roper superbasin. They may reflect exhumation of a provenance region. The 1440 to 1300 Ma ages are related to fault reactivation and a thermal pulse at similar to 1440 to 1400 Ma possibly accompanied by fluid flow, with subsequent enhanced cooling possibly due to thermal relaxation or further crustal exhumation. The youngest thermal and/or fluid-flow event at 1250 to 1150 Ma is recorded mainly to the cast of the Tern-lite Range fault and may be related to the assembly of the Rodinian supercontinent. Fluids in equilibrium with illite that formed over a range of temperatures, at different times in different parts of the platform. have relatively uniform oxygen isotope compositions and more variable hydrogen isotope compositions (delta O-18 = 3.5-9.7 parts per thousand V-SMOW; delta D = -94 to -36 parts per thousand V-SMOW). The extent of the 180 enrichment and the variably depleted hydrogen isotope compositions suggest the illite interacted with deep-basin hypersaline brines that were composed of evaporated seawater and/or highly evolved meteoric water. Siderite is the most abundant iron-rich gangue phase in the Century Zn-Pb deposit, which is surrounded by all extensive ferroan carbonate alteration halo. Modeling suggests that the ore siderite formed at temperatures of 120 degrees to 150 degrees C, whereas siderite and ankerite in the alteration halo formed at temperatures of 150 degrees to 180 degrees C. The calculated isotopic compositions of the fluids are consistent with O-18-rich basinal brines and mixed inorganic and organic carbon Sources (6180 = 3-10 parts per thousand V-SMOW, delta C-13 = -7 to -3 parts per thousand V-PDB). in the northeast Lawn Hill platform carbonate-rich rocks preserve marine to early diagenetic carbon and oxygen isotope compositions, whereas ferroan carbonate cements in siltstones and shales in the Desert Creek borehole are O-18 and C-13 depleted relative to the sedimentary carbonates. The good agreement between temperature estimates from illite crystallinity and organic reflectance (160 degrees-270 degrees C) and inverse correlation with carbonate delta O-18 values indicates that organic maturation and carbonate precipitation in the northeast Lawn Hill platform resulted from interaction with the 1250 to 1150 Ma fluids. The calculated isotopic compositions of the fluid are consistent with evolved basinal brine (delta O-18 = 5.1-9.4 parts per thousand V-SMOW; delta C-13 = -13.2 to -3.7 parts per thousand V-PDB) that contained a variable organic carbon component from the oxidation and/or hydrolysis of organic matter in the host sequence. The occurrence of extensive O-18- and C-13-depleted ankerite and siderite alteration in Desert Creek is related to the high temperature of the 1250 to 1150 Ma fluid-flow event in the northeast Lawn Hill platform, in contrast to the lower temperature fluids associated with the earlier Century Zn-Pb deposit in the central Lawn Hill platform.
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Approaches to quantify the organic carbon accumulation on a global scale generally do not consider the small-scale variability of sedimentary and oceanographic boundary conditions along continental margins. In this study, we present a new approach to regionalize the total organic carbon (TOC) content in surface sediments (<5 cm sediment depth). It is based on a compilation of more than 5500 single measurements from various sources. Global TOC distribution was determined by the application of a combined qualitative and quantitative-geostatistical method. Overall, 33 benthic TOC-based provinces were defined and used to process the global distribution pattern of the TOC content in surface sediments in a 1°x1° grid resolution. Regional dependencies of data points within each single province are expressed by modeled semi-variograms. Measured and estimated TOC values show good correlation, emphasizing the reasonable applicability of the method. The accumulation of organic carbon in marine surface sediments is a key parameter in the control of mineralization processes and the material exchange between the sediment and the ocean water. Our approach will help to improve global budgets of nutrient and carbon cycles.
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Thomas
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Variability in the oceanic environment of the Arabian Sea region is strongly influenced by the seasonal monsoon cycle of alternating wind directions. Prominent and well studied is the summer monsoon, but much less is known about late Holocene changes in winter monsoon strength with winds from the northeast that drive convective mixing and high surface ocean productivity in the northeastern Arabian Sea. To establish a high-resolution record of winter monsoon variability for the late Holocene, we analyzed alkenone-derived sea surface temperature (SST) variations and proxies of primary productivity (organic carbon and d15N) in a well-laminated sediment core from the Pakistan continental margin. Weak winter monsoon intensities off Pakistan are indicated from 400 B.C. to 250 A.D. by reduced productivity and relatively high SST. At about 250 A.D., the intensity of the winter monsoon increased off Pakistan as indicated by a trend to lower SST. We infer that monsoon conditions were relatively unstable from ~500 to 1300 A.D., because primary production and SST were highly variable. Declining SST and elevated biological production from 1400 to 1900 A.D. suggest invigorated convective winter mixing by strengthening winter monsoon circulation, most likely a regional expression of colder climate conditions during the Little Ice Age on the Northern Hemisphere. The comparison of winter monsoon intensity with records of summer monsoon intensity suggests that an inverse relationship between summer and winter monsoon strength exists in the Asian monsoon system during the late Holocene, effected by shifts in the Intertropical Convergence Zone.
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El presente trabajo analiza la evolución del señorío eclesiástico en el largo plazo, para sumar al conocimiento de las formas señoriales de la Extremadura leonesa. Consideramos específicamente el caso del cabildo catedralicio salmantino entre los siglos XII y XV. Buscamos demostrar que no poseyó idéntica estructura durante todo el período y que sus transformaciones se explican por una compleja conjunción de variables. Dichas transformaciones incidieron sobre las estructuras sociales del agro, en especial sobre el desarrollo de procesos de diferenciación social campesina. Demostramos que la forma concreta en que se realizaba la renta podía alterar las estructuras sociales de las comunidades y que el desarrollo de las relaciones sociales asalariadas se encontraba muy vinculado a las coyunturas económicas y a las posibilidades y límites de la gestión señorial. Finalmente, ponemos de relieve que la transformación social no siempre fue irreversible y que su consolidación dependió de la incapacidad de los señores de ejercer sus poderes políticos.
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Durante el siglo XIII se produjo una sucesión de revueltas que supuso la desaparición del Imperio almohade y su sustitución por poderes regionales en al-Andalus, el Magreb y el Magreb al-Aqsà. La historiografía ha presentado el surgimiento y pugna entre estos poderes como un fenómeno social, político e, incluso, cultural y religioso, con el que se ha podido explicar su aniquilación o marginalización. Este trabajo pretende contextualizar los hechos desde una perspectiva medioambiental, de forma que la desintegración del califato almohade, el surgimiento de aquellos poderes y la progresión de los reinos cristianos en la península ibérica puedan entenderse desde una visión global de cambio climático y una posible crisis agrícola.
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El presente trabajo pretende analizar cuáles eran las características climáticas que se sucedían en Madrid y su Tierra a lo largo del año, fundamentalmente entre los siglos XIV y XVI. Se intentará comprobar, dentro de las limitaciones que impone la documentación de la época, si en aquel tiempo se daba también un clima mediterráneo, o no, y si este ha variado mucho desde entonces. Igualmente se podrá comprobar algo que tal vez podría, aunque no debería, sorprendernos: el hombre medieval tenía muy claros muchos conceptos meteorológicos y climatológicos, aunque siempre aprehendidos con una finalidad práctica, para aplicarlos en su vida cotidiana tan cercana y dependiente de la naturaleza.
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La tesis mariológica de la conceptio per aurem, según la cual la Virgen María habría concebido a Jesucristo por el oído en el momento de escuchar del ángel el mensaje celestial anunciándole que, sin perder su virginidad, sería madre del Hijo de Dios encarnado, ha merecido hasta ahora muy pocos estudios académicos rigurosamente fundados en fuentes primarias. De hecho, en la literatura especializada son muy escasas las referencias a tal teoría y, cuando algún estudioso la evoca, casi siempre se contenta con aludir a ella, sin aportar pruebas documentales. Sin embargo, tal como lo revelan las nueve pinturas italianas aquí analizadas, esa teoría fue ilustrada mediante sutiles metáforas visuales en muchas obras pictóricas medievales, las cuales se inspiraron en una sólida tradición literaria. Además una pléyade de Padres de la Iglesia y teólogos medievales testimonia, mediante afirmaciones explícitas, que semejante teoría gozó de notable aceptación entre los maestros del pensamiento cristiano. Basándose en numerosos textos patrísticos y teológicos, este artículo intenta dos objetivos esenciales: exponer, ante todo, las distintas formulaciones teóricas propuestas por esos pensadores; y además, tratar de poner en luz los significados dogmáticos que subyacen bajo esa sorprendente tesis.
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La berenjena (Solanum melongena L.) es una planta solanácea de múltiples variedades, cuyos ancestros salvajes se sitúan en Indochina y el este de África. Su cultivo fue muy temprano en zonas de China e India. Aun así, no se extendió al Occidente antiguo ni apenas se conoció, de ahí su ausencia en los textos clásicos de botánica y farmacología. Fueron los árabes quienes llevaron el cultivo de la planta por el Norte de África y Al-Andalus, de donde pasó ya a Europa. Los primeros testimonios occidentales de la berenjena aparecen en traducciones latinas de textos árabes, para incorporarse luego a la literatura farmacológica medieval y, más tarde ya, a la del Renacimiento, que empezó a tratar de ella por su posible parecido con una especie de mandrágora. Pese a que se le reconocían algunas virtudes medicinales, siempre se la tuvo bajo sospecha por ser de sabor poco agradable, indigesta y causante de algunas afecciones. Solo los botánicos de finales del Renacimiento describirían la planta y sus variedades con criterios más «científicos» y botánicos, ya sin apenas intereses farmacológicos.
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Photographs
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In this study, we considered earthquakes with a maximum observed intensity (MOI) Io≥V that occurred throughout the Portuguese mainland and its adjacent Atlantic region to produce the map of maximum intensities of Portugal. This map is based on a wide variety of historical and recent sources, including 175 earthquakes, over the period of 1300–2014. This MOI map allows the regions of high, medium, and low levels of seismic hazard to be highlighted. The entirety of Portugal has been affected by major seismic events, some of which have caused serious damage. In addition, offshore earthquakes have had significant impacts on the coastal cities located in the central and southern regions of the country. Because the southern region of mainland Portugal is more active than the northern region, the largest concentrations of events with Io≥VI are in the southern region, especially on the mainland near the city of Évora, in the Lisbon region, in the Lower Tagus Valley region, and along the Algarve coast, especially in the southwest region in Cape of São Vicente and the Gorringe Bank.
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O estudo da sismicidade em Portugal ao longo de várias centenas de anos é essencial para uma melhor avaliação do risco sísmico ao qual o continente está sujeito. Neste trabalho, a organização de diversas fontes históricas e atuais numa base de dados possibilita validar facilmente a ocorrência de eventos sísmicos no período desde 1300 a 2014. A construção de um mapa de intensidades máximas observadas neste período permite mostrar que todo o território Português esteve sujeito a sismos com Io≥V. Existem também registos de grandes eventos sísmicos, concentrados em pequenas áreas, que causaram danos consideráveis. De destacar ainda o impacto dos sismos com epicentro no mar, nas cidades costeiras, no Centro e Sul do país.