89 resultados para Gold nanocrystals
Resumo:
Earnings from gold mining in Australia remained tax-exempt for almost seven decades until January 1, 1991. In the early 1980s, rapid economic prosperity induced by escalated gold prices brought the Australian gold-mining industry under intense political scrutiny. Using a variant of the modified Jones model, this paper provides evidence of significant downward earnings management by Australian gold-mining firms, which is consistent with their attempts to mitigate political costs during the period from June 1985 to May 1988. In contrast, test of earnings management over a similar period in a control sample of Canadian gold-mining firms produced insignificant results. Further, empirical results are robust to several sensitivity tests performed. During the period from June 1988 to December 1990, the Australian firms were found to have engaged in economic earnings management. This is consistent with the sample firms' incentive of maximizing economic earnings immediately prior to the introduction of income tax on gold mining. The findings of this study help to understand the impact of earnings management on the efficient resource allocation in an economy. They also contribute toward understanding the linkage between regulation of accounting for special purposes and general-purpose financial. reporting.
Resumo:
The Jiaodong gold province is the largest gold repository in China. Both mineralization and granitoid hosts are spatially related to the crustal-scale Tan-Lu strike-slip fault system, which developed along the Mesozoic continental margin in eastern China. A series of Ar-40/Ar-39 laser incremental heating analyses of hydrothermal sericite/muscovite from three major gold deposits (Jiaojia, Xincheng, and Wangershan) and igneous biotite from the granodiorite hosts were performed to establish a possible temporal link between gold mineralization, magmatism, and movement along the Tan-Lu fault zone. Magmatic biotite crystals yield well-defined and concordant plateau ages between 124.5+/-0.4 Ma and 124.0+/-0.4 Ma (2sigma), whereas sericite and muscovite samples (a total of 30 single separates) give reproducible plateau ages ranging from 121.0+/-0.4 Ma to 119.2+/-0.2 Ma (2sigma). An integration of our Ar-40/Ar-39 results with age data from other major gold deposits in Jiaodong demonstrates that widespread gold mineralization occurred contemporaneously during a 2-3-m.yr. period. Most gold deposits show intimate spatial associations with abundant mafic to intermediate dikes. The mafic dikes have K-Ar ages of 123.5-119.6 Ma, in excellent agreement with those of the gold deposits. These newly obtained Ar-40/Ar-39 ages, in combination with other independent geological and geochronological data on granodioritic intrusions (130-126 Ma), volcanic rocks (1243.6-114.7 Ma), and deformed rocks within strike-slip faults (132-120 Ma) in Jiaodong or adjacent areas, also support the idea that gold mineralization postdated the granodioritic magmatism but was contemporaneous with mafic magmatism and volcanism, all controlled by the transtensional motion along the Tan-Lu fault in the Early Cretaceous.
Resumo:
Governments, as key stakeholders in the development of events, produce policies to facilitate the growth and potential of events as a platform for industry and economic development. To date, however, there has been a paucity of research undertaken to determine the appropriateness and the consequences of government policies pertaining to events. This paper studies the event policies of two Australian local government authorities, the Gold Coast City Council and Brisbane City Council, from 1974-2003, as measured by four development paradigms: Modernisation, Dependency, Economic Neoliberalism, and Alternative. The analysis revealed that these policies were predominantly underpinned by the Alternative which has a strong socio-cultural focus. Increased awareness and utilisation of the various development paradigms will assist local governments in producing future event policies to promote growth of the event industry and concomitantly, appropriate development within their region.
Resumo:
Photoluminescent emission is observed from surface-passivated PbS nanocrystals following the two-photon excitation of high-energy excitonic states. The emission appears directly at the excitation energy with no detectable Stokes-shift for a wide range of excitation energies. The observation of direct emission from states excited by two-photon absorption indicates that the parity of the excited states of surface-passivated PbS nanocrystals is partially mixed.
Resumo:
Accommodation is considered to be important by institutions interested in mental health care both in Australia and internationally. Some authorities assert that no component of a community mental health system is more important than decent affordable housing. Unfortunately there has been little research in Australia into the consequences of discharging people with a primary diagnosis of schizophrenia to different types of accommodation. This paper uses archival data to investigate the outcomes for people with schizophrenia discharged to two types of accommodation. The types of accommodation chosen are the person's own home and for-profit boarding house. These two were chosen because the literature suggests that they are respectively the most and least desirable types of accommodation. Results suggest that people with schizophrenia who were discharged to boarding houses are significantly more likely to be readmitted to the psychiatric unit of Gold Coast Hospital although their length of stay in hospital is not significantly different. (author abstract)
Resumo:
We describe a single step method to synthesise lead sulphide (PbS) nanocrystals directly in the conjugated polymer poly (2-methoxy-5-(2'-ethyl-hexyloxy)-p-phenylene vinylene) (MEH-PPV). This method allows size control of the nanocrystal via co-solvent ratios. We find good agreement between nanocrystal sizes determined by transmission electron microscopy and sizes theoretically determined from the absorption edge of the nanocrystals. Finally we show that this synthesis technique is not restricted to MEH-PPV and demonstrate that nanocrystals can be grown in Poly(3-hexylthiophene-2,5-diyl) (P3HT). (C) 2005 Elsevier B.V. All rights reserved.
Resumo:
Monodisperse 1-2 nm silicon nanocrystals are synthesized in reverse micelles and have their surfaces capped with either allylamine or 1-heptene to produce either hydrophilic or hydrophobic silicon nanocrystals. Optical characterization (absorption, PL, and time-resolved PL) is performed on colloidal solutions with the two types of surface-capped silicon nanocrystals with identical size distributions. Direct evidence is obtained for the modification of the optical properties of silicon nanocrystals by the surface-capping molecule. The two different surface-capped silicon nanocrystals show remarkably different optical properties.
Resumo:
PbS nanocrystals are synthesized using colloidal techniques and have their surfaces capped with oleic acid. The absorption band edge of the PbS nanocrystals is tuned between 900 and 580 nm. The PbS nanocrystals exhibit tuneable photoluminescence with large non-resonant Stokes shifts of up to 500 mcV. The magnitude of the Stokes shift is found to be dependent upon the size of PbS nanocrystals. Time-resolved photoluminescence spectroscopy of the PbS nanocrystals reveals that the photouminescence has an extraordinarily long lifetime of 1 mus. This long fluorescence lifetime is attributed to the effect of dielectric screening similar to that observed in other IV-VI semiconductor nanocrystals.