870 resultados para The Early Permian
Resumo:
The record of deposition of tephras in Europe and the North Atlantic during the period 18.5–8.0 14C ka BP (the Last Termination and Early Holocene) is reviewed. Altogether, 34 tephras originating from four main volcanic provinces (Iceland, the Eifel district, the Massif Central and Italy) have been identified so far in geological sequences spanning this time–interval. Most of the records have been based, until very recently, on observations of visible layers of tephras. Here, we report on the potential for extending the areas over which some of the tephras can be traced by the search for layers of micro–tephra, which are not visible to the naked eye, and on the use of geochemical methods to correlate them with known tephra horizons. This approach has greatly extended the area in Northern Europe over which the Vedde Ash can be traced. The same potential exists in southern Europe, which is demonstrated for the first time by the discovery of a distinct layer of micro–tephra of the Neapolitan Yellow Tuff in a site in the Northern Apennines in Italy, far to the north of the occurrences of visible records of this tephra. The paper closes by considering the potential for developing a robust European tephrostratigraphy to underpin the chronology of records of the Last Termination and Early Holocene, thereby promoting a better understanding of the nature, timing and environmental effects of the abrupt climatic changes that characterized this period.
Resumo:
The first stable homoleptic alkenyls of the early transition metals, MRn, (R = C(Ph)=CMe2; M = Ti, Zr, Hf, n = 4; and M = Cr, n = 3) and the related species (C5H5)2MR2 (M = Ti, Zr) and (C5H5)2Zr(Cl)R have been prepared using appropriate organolithium reagents. Cleavage and insertion reactions are reported for the new compounds.
Resumo:
The chapter begins by establishing the key features of poetry itself and of poetry in the early years of schooling. A case study of how poetry is taught and learnt in one Reception class (ages 4 - 5 years) is presented, in this way demonstrating what excellent practice might look like. Poetry for listening to, for performing, for word-play, for responding and for writing are all covered. The chapter ends with advice on 'where do I start in teaching poetry?'
Resumo:
The themes of awareness and influence within the innovation diffusion process are addressed. The innovation diffusion process is typically represented as stages, yet awareness and influence are somewhat under-represented in the literature. Awareness and influence are situated within the contextual setting of individual actors but also within the broader institutional forces. Understanding how actors become aware of an innovation and then how their opinion is influenced is important for creating a more innovation-active UK construction sector. Social network analysis is proposed as one technique for mapping how awareness and influence occur and what they look like as a network. Empirical data are gathered using two modes of enquiry. This is done through a pilot study consisting of chartered professionals and then through a case study organization as it attempted to diffuse an innovation. The analysis demonstrates significant variations across actors’ awareness and influence networks. It is argued that social network analysis can complement other research methods in order to present a richer picture of how actors become aware of innovations and where they draw their influences regarding adopting innovations. In summarizing the findings, a framework for understanding awareness and influence associated with innovation within the UK construction sector is presented. Finally, with the UK construction sector continually being encouraged to be innovative, understanding and managing an actor’s awareness and influence network will be beneficial. The overarching conclusion thus describes the need not only to build research capacity in this area but also to push the boundaries related to the research methods employed.
Resumo:
Research on the cortical sources of nociceptive laser-evoked brain potentials (LEPs) began almost two decades ago (Tarkka and Treede, 1993). Whereas there is a large consensus on the sources of the late part of the LEP waveform (N2 and P2 waves), the relative contribution of the primary somatosensory cortex (S1) to the early part of the LEP waveform (N1 wave) is still debated. To address this issue we recorded LEPs elicited by the stimulation of four limbs in a large population (n=35). Early LEP generators were estimated both at single-subject and group level, using three different approaches: distributed source analysis, dipolar source modeling, and probabilistic independent component analysis (ICA). We show that the scalp distribution of the earliest LEP response to hand stimulation was maximal over the central-parietal electrodes contralateral to the stimulated side, while that of the earliest LEP response to foot stimulation was maximal over the central-parietal midline electrodes. Crucially, all three approaches indicated hand and foot S1 areas as generators of the earliest LEP response. Altogether, these findings indicate that the earliest part of the scalp response elicited by a selective nociceptive stimulus is largely explained by activity in the contralateral S1, with negligible contribution from the secondary somatosensory cortex (S2).