216 resultados para AK26A-2601


Relevância:

20.00% 20.00%

Publicador:

Resumo:

Micropaleontological and biomarker data from two high-accumulation marine sites from the Coastal and Continental Shelf Zone (CCSZ) off East Antarctica (Adélie Land at w140°E and eastern Prydz Bay at w77°E) are used to reconstruct Holocene changes in sea ice and wind stress at the basin-wide scale. These data demonstrate congruent increase in sea-ice concentration/persistence and wind stress-related sea-surface turbulence in the two regions since 7 cal ka BP, with a particularly strong signal since 4.5 - 3.5 cal ka BP. Comparison of these high latitude records with sea ice and turbulence records from the southern mid-latitudes highlights distinctive climatic evolutions according to the different latitudinal bands. Sea-ice persistence and turbulence increase in East Antarctica CCSZ are opposite to sea-surface warming and sea-ice retreat recorded after 4.5 - 3.5 cal ka BP in the East Atlantic and Indian sector between 55 and 45°S. At the same period, paleodata suggest SST cooling in all major coastal upwelling systems of the southern hemisphere, caused by the northward transport of subpolar surface waters as a response to southern Westerlies reinforcement. We therefore propose, as suggested for the northern hemisphere, that Holocene changes in the latitudinal insolation gradient, primarily forced by obliquity and precession and amplified by sea-ice and glacial-ice expansions in the Antarctic realm, are responsible for the observed contrasted latitudinal patterns of southern latitudes.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The project investigated the relationships between diversification in modes ofdelivery, use of information and communication technologies, academics’ teaching practices, and the context in which those practices are employed, in two of the three large universities in Brisbane—Griffith University and the Queensland University of Technology (QUT). The project’s initial plan involved the investigation of two sites: Queensland University of Technology’s Faculty of Education (Kelvin Grove campus) and Griffith University’s Faculty of Humanities(Nathan campus). Interviews associated with the Faculty of Education led to a decision to include a third site—the School of Law within Queensland University of Technology’s Faculty of Law, which is based on the Gardens Point Campus. Here the investigation focused on the use of computer-based flexible learning practices, as distinct from the more text-based practices identified within the original two sites.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Synthesis of imines from amines and aliphatic alcohols (C1–C6) in the presence of base on supported palladium nanoparticles has been achieved for the first time. The catalytic system shows high activity and selectivity in open air at room temperature. As an example of the isostructural Ln3Sb3Co2O14 (Ln: La, Pr, Nd, Sm—Ho) series with an ordered pyrochlore structure, the La variant is prepared by a citrate complex method employing stoichiometric amounts of La(NO3)3, Co(NO3)2, and Sb tartrate together with citric acid with a metal/citrate molar ratio of 1:2

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This study aimed to provide a detailed evaluation and comparison of a range of modulated beam evaluation metrics, in terms of their correlation with QA testing results and their variation between treatment sites, for a large number of treatments. Ten metrics including the modulation index (MI), fluence map complexity (FMC), modulation complexity score (MCS), mean aperture displacement (MAD) and small aperture score (SAS) were evaluated for 546 beams from 122 IMRT and VMAT treatment plans targeting the anus, rectum, endometrium, brain, head and neck and prostate. The calculated sets of metrics were evaluated in terms of their relationships to each other and their correlation with the results of electronic portal imaging based quality assurance (QA) evaluations of the treatment beams. Evaluation of the MI, MAD and SAS suggested that beams used in treatments of the anus, rectum, head and neck were more complex than the prostate and brain treatment beams. Seven of the ten beam complexity metrics were found to be strongly correlated with the results from QA testing of the IMRT beams (p < 0.00008). For example, Values of SAS (with MLC apertures narrower than 10 mm defined as “small”) less than 0.2 also identified QA passing IMRT beams with 100% specificity. However, few of the metrics are correlated with the results from QA testing of the VMAT beams, whether they were evaluated as whole 360◦ arcs or as 60◦ sub-arcs. Select evaluation of beam complexity metrics (at least MI, MCS and SAS) is therefore recommended, as an intermediate step in the IMRT QA chain. Such evaluation may also be useful as a means of periodically reviewing VMAT planning or optimiser performance.