1,308 research outputs found

    Aligning the Interests of Multiple Principals: Ownership Concentration and Profitability in China's Publicly-Traded Firms

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    Across the social sciences, agency theory has become one of the basic frameworks through which to analyze the organizational problem of aligning interests between owners (principals) and those who carry out the work of the corporation (agents). Less often analyzed within this framework is the problem of multiple principals with different incentives and agendas. In today's global economy, this is a problem that institutional investors from around the world encounter on a regular basis. We argue that ownership concentration holds the key to dealing with the collective action problems that emerge in these circumstances. To provide empirical insight into these issues, we analyze the impact of ownership concentration in multiple-principal firms that have been listed on the Shanghai and Shenzhen stock exchanges over the last decade. Through these data, we show that the strongest factor shaping performance among this population of firms is ownership concentration: the higher a firm's ownership concentration, the better it performs, both in terms of profitability and in terms of efficiency. Further, as markets in this context have become more competitive over the last decade, overall profitability has declined, but the effect of ownership concentration has increased, suggesting that ownership concentration becomes even more important for achieving corporate goals as markets become more competitive

    The evolution of microbialite forms during the Early Triassic transgression: A case study in Chongyang of Hubei Province, South China

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    The widespread development of microbialites in shallow areas of the Tethys Ocean at the start of the Early Triassic reflects the deterioration of marine ecosystems in the aftermath of the extinction that marked the demise of the majority of Palaeozoic marine faunas. Here we present a study of the evolving microbialite forms and associated biotic assemblages of this pioneering microbialite interval from exposures at Chongyang, Hubei Province, China. This research provides a perspective on the effects of eustatic transgression on marine ecosystems as water depths increased at the beginning of Mesozoic, through the study of the changing forms, microfacies and distribution of microbialites. Microbialite forms evolved from stratiform stromatolites to a sequence of tabular thrombolites (with an intercalated layer of columnar stromatolites), followed by domical thrombolites that were overlain, in turn, by oolites. The stratiform stromatolites contain poorly preserved remains of calcified cyanobacteria, but microfossils with chambered structure can also be seen. Metazoan fossils increased from the base of the overlying tabular thrombolite, reflecting increasing biodiversity with deepening of seawater. The occurrence of columnar stromatolites within the tabular thrombolite may indicate a temporary sea-level shallowing. Foraminiferans and other metazoans are absent within the columnar stromatolites, but spherical cyanobacterial remains are extremely abundant. Well-preserved calcified cyanobacteria may reflect an absence of metazoan predation and/or carbonate supersaturation of seawater. As water deepened, domical thrombolites developed and the more complex seafloor relief created varied niches between and within the domes that harboured more ecologically diverse communities. During the process of transgression within the microbialite interval, carbon isotopes exhibit a negative relationship with biodiversity, implying that upwelling of anoxic deep-ocean water, if associated with the negative excursion of carbon isotope values, did not inhibit the diversification of benthic organisms at least on shallow carbonate platforms in the period immediately after the end-Permian mass extinction.This study was jointly supported by the National Natural Science Foundationof China (Grants No. 41730320 and No. 41572001) and the 111 project(B08030

    Monte Carlo simulation of light transport in dark-field confocal photoacoustic microscopy

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    A modified MC convolution method for integration extension of MC simulation is developed for finite photon beam with random shape of translational or rotational invariance, which is proven consistent with the conventional convolution extension of MC simulation for normal incident finite beam. The method is applied to analyze the positions of fluence foci and ratios of fluence at the focus and surface which are two key factors in the application of dark-field confocal and some interesting points are presented including: 1) The fluence profile has a saddle-like shape with highest peak in the bright field and low valley near the surface and a second rise in the center of dark field which is defined as the effective optical focus; 2) Besides a little peak near zero inner radius, the ratio of fluences at the focus and surface increases linearly with the inner radius, suggesting the large inner radius more advantageous to image at the effective optical focus; 3) The position of effective optical foci deepens linearly with the increase of the inner radius, suggesting that to get a high quality image of deeper target, a dark-field with larger size is more beneficial. But the position of fluence foci are far away from the foci of geometrical laser beam in high scattering tissue, so aligning the foci of geometrical laser beam and acoustic transducer doesn't guarantee that effective optical focus is accurately overlapping with the acoustic focus. An MC simulation with integration extension presented in this paper maybe helpful to determine where the acoustic focus should be to maximize the SNR in tissue imaging; 4) incident angle makes little difference to ratio of fluences at the focus and surface and an incident angle between 30 and 50 degrees gives the highest fluence at the effective optical focus; 5) the depth of fluence focus is insensitive to the incident angle

    Analysis of the dynamics of a delayed HIV pathogenesis model

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    AbstractIn this paper, considering full Logistic proliferation of CD4+ T cells, we study an HIV pathogenesis model with antiretroviral therapy and HIV replication time. We first analyze the existence and stability of the equilibrium, and then investigate the effect of the time delay on the stability of the infected steady state. Sufficient conditions are given to ensure that the infected steady state is asymptotically stable for all delay. Furthermore, we apply the Nyquist criterion to estimate the length of delay for which stability continues to hold, and investigate the existence of Hopf bifurcation by using a delay τ as a bifurcation parameter. Finally, numerical simulations are presented to illustrate the main results
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