996 resultados para 80-550B


Relevância:

70.00% 70.00%

Publicador:

Resumo:

The evolution through time of trace element contents (Sr, Mg, Mn, and Fe) of sediments at Sites 549 and 550 is similar to that of previously studied oceanic sites. A comparison with some North Atlantic sites and with outcrops of the Gubbio section (Italy) allowed us to show that 1. A negative correlation between Sr and Mg contents, generally characteristic of pelagic carbonate having undergone diagenesis, is confirmed. 2. Magnesium diagenesis occurs over a relatively short time and is sensitive to the sedimentation rate of each individual time period, whereas Sr diagenesis is a long-term phenomenon and is sensitive to the overall average sedimentation rate at the site. Strontium loss by sediments is related to sediment age (i.e., residence time of sediments in a given diagenetic environment) and could be a rough method of dating individual sediment layers. 3. The nature of the seafloor (oceanic or continental) does not appear to play an important part in the content of Fe and Mn in sediments. Their distribution depends more on mid-oceanic ridge activity, paleodepth (through mediation of CaCO3 dissolution and environment), and distance of the site from the ridge.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

A transect from the bathyal to proximal shelf facies of the Boreal Realm was investigated to compare spatial and temporal distribution changes of calcareous dinoflagellate cysts (c-dinocysts) throughout the mid-Cenomanian in order to gain information on the ecology of these organisms. Pithonelloideae dominated the cyst assemblages to more than 95% on the shelf, a prevalence that can be observed throughout most of the Upper Cretaceous. The affinity of this group with the dinoflagellates, which is still controversially discussed, can be confirmed, based on evidence from morphological features and distribution patterns. The consistent prevalence of Pithonella sphaerica and P. ovalis in c-dinocyst assemblages throughout the Upper Cretaceous indicates that they were produced more frequently than cysts of the other species and might, therefore, represent a vegetative dinoflagellate life stage. P. sphaerica and P. ovalis are interpreted as eutrophic species. P. sphaerica is the main species in a marginal-shelf upwelling area, offshore Fennoscandia. Here, sedimentary cyclicity appears to have been reduced to the strongest light/dark changes, while in the outer shelf sediments, light/dark cycles are well-developed and show pronounced temporal assemblage changes. Cyclic fluctuations in the P. sphaerica / P. ovalis ratio reflect shifts of the preferred facies zones and indicate changes in surface mixing patterns. During periods of enhanced surface mixing most parts of the shelf were well-ventilated, and nutrient-enriched surface waters led to high productivity and dominance of the Pithonelloideae. These conditions on the shelf contrasted with those in the open ocean, where more oligotrophic and probably stratified waters prevailed, and an assemblage with very few Pithonelloideae and dominance of Cubodinellum renei and Orthopithonella ? gustafsonii was characteristic. While orbitally-forced light/dark sedimentary cyclicity of the shelf sections was mainly related to surface-water carbonate productivity changes, no cyclic modulation of productivity was observed in the oceanic profile. Therefore, dark layer formation in the open ocean was predominantly controlled by the cyclic establishment of anoxic bottom water conditions. Orbitally-forced interruptions in mixing on the shelf resulted in cyclic periods of stratification and oligotrophy in the surface waters, an expansion of oceanic species to the outer shelf, and a shelfward shift of pithonelloid-facies zones, which were probably related to shelfward directed oceanic ingressions.

Relevância:

60.00% 60.00%

Publicador:

Resumo:

Preservation of planktic foraminiferal calcite has received widespread attention in recent years, but the taphonomy of benthic foraminiferal calcite and its influence on the deep-sea palaeotemperature record have gone comparatively unreported. Numerical modeling indicates that the carbonate recrystallization histories of deep-sea sections are dominated by events in their early burial history, meaning that the degree of exchange between sediments and pore fluids during the early postburial phase holds the key to determining the palaeotemperature significance of diagenetic alteration of benthic foraminifera. Postburial sedimentation rate and lithology are likely to be important determinants of the paleoceanographic significance of this sediment-pore fluid interaction. Here we report an investigation of the impact of extreme change in sedimentation rate (a prolonged and widespread Upper Cretaceous hiatus in the North Atlantic Ocean) on the preservation and d18O of benthic foraminifera of Middle Cretaceous age (nannofossil zone NC10, uppermost Albian/lowermost Cenomanian, ~99 Ma ago) from multiple drill sites. At sites where this hiatus immediately overlies NC10, benthic foraminifera appear to display at least moderate preservation of the whole test. However, on closer inspection, these tests are shown to be extremely poorly preserved internally and yield d18O values substantially higher than those from contemporaneous better preserved benthic foraminifera at sites without an immediately overlying hiatus. These high d18O values are interpreted to indicate alteration close to the seafloor in cooler waters during the Late Cretaceous hiatus. Intersite differences in lithology modulate the diagenetic impact of this extreme change in sedimentation rate. Our results highlight the importance of thorough examination of benthic foraminiferal wall structures and lend support to the view that sedimentation rate and lithology are key factors controlling the paleoceanographic significance of diagenetic alteration of biogenic carbonates.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

An engaging narrative is maintained throughout this edited collection of articles that address the issue of militarism in international relations. The book seamlessly integrates historical and contemporary perspectives on militarism with theory and relevant international case studies, resulting in a very informative read. The work is comprised of three parts. Part 1 deals with the theorisation of militarism and includes chapters by Anna Stavrianakis and Jan Selby, Martin Shaw, Simon Dalby, and Nicola Short. It covers a range of topics relating to historical and contemporary theories of militarism, geopolitical threat construction, political economy, and the US military’s ‘cultural turn’.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We examine the security of the 64-bit lightweight block cipher PRESENT-80 against related-key differential attacks. With a computer search we are able to prove that for any related-key differential characteristic on full-round PRESENT-80, the probability of the characteristic only in the 64-bit state is not higher than 2−64. To overcome the exponential (in the state and key sizes) computational complexity of the search we use truncated differences, however as the key schedule is not nibble oriented, we switch to actual differences and apply early abort techniques to prune the tree-based search. With a new method called extended split approach we are able to make the whole search feasible and we implement and run it in real time. Our approach targets the PRESENT-80 cipher however,with small modifications can be reused for other lightweight ciphers as well.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The 21st century will see monumental change. Either the human race will use its knowledge and skills and change the way it interacts with the environment, or the environment will change the way it interacts with its inhabitants. In the first case, the focus of this book, we would see our sophisticated understanding in areas such as physics, chemistry, engineering, biology, planning, commerce, business and governance accumulated over the last 1,000 years brought to bear on the challenge of dramatically reducing our pressure on the environment. The second case however is the opposite scenario, involving the decline of the planet’s ecosystems until they reach thresholds where recovery is not possible, and following which we have no idea what happens. For instance, if we fail to respond to Sir Nicolas Stern’s call to meet appropriate stabilisation trajectories for greenhouse gas emissions, and we allow the average temperature of our planets surface to increase by 4-6 degrees Celsius, we will see staggering changes to our environment, including rapidly rising sea level, withering crops, diminishing water reserves, drought, cyclones, floods… allowing this to happen will be the failure of our species, and those that survive will have a deadly legacy. In this update to the 1997 International Best Seller, Factor Four, Ernst von Weizsäcker again leads a team to present a compelling case for sector wide advances that can deliver significant resource productivity improvements over the coming century. The purpose of this book is to inspire hope and to then inform meaningful action in the coming decades to respond to the greatest challenge our species has ever faced – that of living in harmony with our planet and its other inhabitants.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

We reported the presence of a 80 kDa polypeptide in porcine follicular fluid that inhibited the binding of 125I-radiolabelled hFSH as well as hCG to the rat ovarian gonadotropin receptors. In the present study, the biological activity of the receptor binding inhibitor is determined using an in vitro bioassay procedure. Granulosa cells isolated from PMSG primed immature rat ovaries respond to exogenously added gonadotropins in terms of progesterone production. Addition of fractions containing the gonadotropin receptor binding inhibitory activity inhibited progesterone production stimulated by the gonadotropins in a dose-dependent fashion. The receptor binding inhibitory activity was also capable of inhibiting progesterone production stimulated by PMSG, which has both FSH- and LH-like activities in rats. In contrast, progesterone production stimulated by dbcAMP was not inhibited by the receptor binding inhibitor. This result indicates that the site of action of the inhibitor is proximal to the formation of the cAMP. The above observations point out to a possible role for this factor in modulating gonadotropin activity at the ovarian level.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Contenido: Presentación -- Parte I. Contribuciones especiales con motivo del 35º Aniversario de la Revista: El derecho privado entre dos Bicentenarios : a propósito de los treinta y cinco años de Prudentia Iuris / Gabriel Limodio -- Breviario de la legislación civil (1980-2015) / Marcelo U. Salerno -- La transformación del derecho penal argentino / Guillermo J. Yacobucci -- Tendencias, cambios y desplazamientos en el campo jurídico / Roberto A. Punte -- Derecho administrativo y ética : una visión luego de treinta y cinco años / Pedro Coviello --- Parte II. Cátedra Internacional Ley Natural y Persona Humana: ¿Hacia un estado mundial de derecho global? / Daniel A. Herrera -- La persona humana en el Código Civil y Comercial, artículos 17 y 19 : una reflexión filosófica / Héctor Padrón -- "De F.A.I., a M.A.D. : el derecho a la vida en la Corte Suprema de Justicia de la Nación" : workshop del 19 de noviembre de 2015 / Jorge Nicolás Lafferriere -- Parte III. Estudios doctrinales : Hegel y la disolución de la tradición de la ley natural : el apogeo del gnosticismo moderno / Félix A. Lamas -- El aborto en la ley europea : derechos humanos, derechos sociales y la nueva tendencia cultural / Grégor Puppinck -- Hacia una política criminal integradora / Carlos M. Romero Berdullas -- La doctrina del control de convencionalidad : dificultades inherentes y criterios razonables para su aplicabilidad / Juan Alonso Tello Mendoza -- Parte IV. Notas y comentarios : Habla ahora o calla (forzosamente) para siempre : las Convenciones en contra de toda forma de discriminación e intolerancia y su amenaza a la libertad de expresión en los estados americanos / Tomás Henríquez C. -- The art of human rights : enriching the life of the law school through drawings and other visual resources / Santiago Legarre -- Las citas de leyes y otras normas : legislación comparada y nuevo Digesto Jurídico Argentino / Fernando M. Toller -- "Paradiso, Campanelli" y un contrato internacional de maternidad subrogada ante el TSribunal Europeo de Derechos Humanos / Julieta Monteroni -- Parte V. Documentos -- Recensiones

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Contenido: Fenomenología y metafísica / Octavio N. Derisi – Balmes y los fundamentos de la ciencia / Augusto Furlán – Libertad religiosa / Octavio N. Derisi – Orígenes, fundamentos y función de la Universidad / Osvaldo Ardiles – Notas y comentarios -- Bibliografía

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Resumen: El Congreso Eucarístico Internacional de 1934 marcó un antes y un después en la Iglesia argentina. Al celebrar sus ochenta años es importante recordar algunas de las consideraciones canónicas que se tuvieron en cuenta para su realización, así como las consecuencias pastorales que tuvo en la Iglesia argentina.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Coleção de editais de concursos públicos reunidos pela Coordenação de Relacionamento Pesquisa e Informação do Centro de Documentação da Câmara dos Deputados.