109 research outputs found
Does Common Ownership Impact Auditor Incentives?
Prior research suggests that common ownership (i.e., institutional investors owning significant equity stakes in companies within the same industry) impairs companies’ incentives to compete since owners are less likely to support an aggressive competitive strategy. In this paper, we examine whether common ownership impacts auditor incentives. Using a sample of US firms during the 2003–2017 period, we find that common ownership lowers audit fees and audit effort without impairing audit quality. We perform cross-sectional tests as well as a quasi-natural experiment based on institutional owner mergers to help mitigate concerns about omitted variable bias or reverse causality. Overall, our findings are consistent with the view that common-owners internalize governance externalities and have accumulated more industry-specific monitoring experience, which in turn decreases audit risk
Spectral characteristics of randomly switched PWM DC/DC converters operating in discontinuous conduction mode
High thermal stress responses of Echinolittorina snails at their range edge predict population vulnerability to future warming
Populations at the edge of their species' distribution ranges are typically living at the physiological extreme of the environmental conditions they can tolerate. As a species' response to global change is likely to be largely determined by its physiological performance, subsequent changes in environmental conditions can profoundly influence populations at range edges, resulting in range extensions or retractions. To understand the differential physiological performance among populations at their distribution range edge and center, we measured levels of mRNA for heat shock protein 70 (hsp70) as an indicator of temperature sensitivity in two high-shore littorinid snails, Echinolittorina malaccana and E. radiata, between 1°N to 36°N along the NW Pacific coast. These Echinolittorina snails are extremely heat-tolerant and frequently experience environmental temperatures in excess of 55°C when emersed. It was assumed that animals exhibiting high temperature sensitivity will synthesize higher levels of mRNA, which will thus lead to higher energetic costs for thermal defense. Populations showed significant geographic variation in temperature sensitivity along their range. Snails at the northern range edge of E. malaccana and southern range edge of E. radiata exhibited higher levels of hsp70 expression than individuals collected from populations at the center of their respective ranges. The high levels of hsp70 mRNA in populations at the edge of a species' distribution range may serve as an adaptive response to locally stressful thermal environments, suggesting populations at the edge of their distribution range are potentially more sensitive to future global warming
Notes on Theories
The cosmological models based on teleparallel gravity with nonzero torsion
are considered. To investigate the evolution of this theory, we consider the
phase-space analysis of the theory. It shows when the tension scalar can
be written as an inverse function of where
and , the system is an autonomous one. Furthermore,the
phase analysis is given out. We perform the dynamical
analysis for the models and particularly. We find that the universe will
settle into de-Sitter phase for both models. And we have examined the evolution
behavior of the power law form in the plane.Comment: 13 pages, 2 figure
Self-consistent scattering description of transport in normal-superconductor structures
We present a scattering description of transport in several
normal-superconductor structures. We show that the related requirements of
self-consistency and current conservation introduce qualitative changes in the
transport behavior when the current in the superconductor is not negligible.
The energy thresholds for quasiparticle propagation in the superconductor are
sensitive to the existence of condensate flow (). This dependence is
responsible for a rich variety of transport regimes, including a voltage range
in which only Andreev transmission is possible at the interfaces, and a state
of gapless superconductivity which may survive up to high voltages if
temperature is low. The two main effects of current conservation are a shift
towards lower voltages of the first peak in the differential conductance and an
enhancement of current caused by the greater availability of charge
transmitting scattering channels.Comment: 31 pages, 10 PS figures, Latex file, psfig.sty file is added. To
appear in Phys. Rev. B (Jan 97
Nonequilibrium Josephson effect in mesoscopic ballistic multiterminal SNS junctions
We present a detailed study of nonequilibrium Josephson currents and
conductance in ballistic multiterminal SNS-devices. Nonequilibrium is created
by means of quasiparticle injection from a normal reservoir connected to the
normal part of the junction. By applying a voltage at the normal reservoir the
Josephson current can be suppressed or the direction of the current can be
reversed. For a junction longer than the thermal length, , the
nonequilibrium current increases linearly with applied voltage, saturating at a
value equal to the equilibrium current of a short junction. The conductance
exhibits a finite bias anomaly around . For symmetric
injection, the conductance oscillates -periodically with the phase
difference between the superconductors, with position of the minimum
( or ) dependent on applied voltage and temperature. For
asymmetric injection, both the nonequilibrium Josephson current and the
conductance becomes -periodic in phase difference. Inclusion of barriers
at the NS-interfaces gives rise to a resonant behavior of the total Josephson
current with respect to junction length with a period . Both
three and four terminal junctions are studied.Comment: 21 pages, 19 figures, submitted to Phys. Rev.
Physical activity intervention in cancer survivors : a systematic review and meta-analysis of randomized controlled trials
Proffered paper session: Information, patients and the public/ Survivorship and end of life careBackground
The aim was to systematically review all published randomized controlled trials (RCTs) which tested the effect of a physical activity intervention in adult cancer survivors after the main cancer treatment.
Method
Relevant RCTs were located by: (1) systematic searching of electronic databases (PUBMED and Google Scholar) using cancer-related and exercise-related search terms; and (2) scanning the references of retrieved RCTs and relevant reviews. All relevant RCTs were retrieved and assessed to determine if they met the selection criteria. Data extraction was independently performed by two investigators and followed by a discussion to reach consensus. The main outcome measures were cancer outcome (survival and recurrence), quality of life (QoL), body composition and functional capacity.
Results
A total of 2,447 citations were identified of which 170 potentially relevant ones were examined in detail. Forty-five papers met the selection criteria of which 41 reported data on at least one relevant outcome. These encompassed 18 papers not included in previously published reviews. Twenty-six papers (63.4%) were on breast cancers and the remaining papers were on other cancers.
There was a paucity of published data on the effects of physical activity interventions on cancer outcome. Various instruments were used to assess the other outcomes (QoL and functional capacity) limiting the pooling of data for meta-analysis. Estimates of the effects of physical activity interventions on QoL, body composition and functional capacity were determined. Potential determinants of the effect heterogeneity across studies were evaluated.
Conclusion
Moderately-strong-to-strong evidence was found for a positive effect of physical activity interventions on QoL of adult cancer survivors following main cancer treatment. Clinically meaningful associations were identified between such interventions and improved functional capacity. The observed heterogeneity in study design and outcome parameters highlighted the need for the development of a standardized protocol to facilitate meta-analysis on the effects of physical activity in cancer survivors.
Acknowledgements
This study has been supported by WCRF UK, WCRF International and WCRF Hong Kong
Extremal Bundles on Calabi-Yau Threefolds
We study constructions of stable holomorphic vector bundles on Calabi–Yau threefolds, especially those with exact anomaly cancellation which we call extremal. By going through the known databases we find that such examples are rare in general and can be ruled out for the spectral cover construction for all elliptic threefolds. We then introduce a general Hartshorne–Serre construction and use it to find extremal bundles of general ranks and study their stability, as well as computing their Chern numbers. Based on both existing and our new constructions, we revisit the DRY conjecture for the existence of stable sheaves on Calabi–threefolds, and provide theoretical and numerical evidence for its correctness. Our construction can be easily generalized to bundles with no extremal conditions imposed
Pulsar-wind nebulae and magnetar outflows: observations at radio, X-ray, and gamma-ray wavelengths
We review observations of several classes of neutron-star-powered outflows:
pulsar-wind nebulae (PWNe) inside shell supernova remnants (SNRs), PWNe
interacting directly with interstellar medium (ISM), and magnetar-powered
outflows. We describe radio, X-ray, and gamma-ray observations of PWNe,
focusing first on integrated spectral-energy distributions (SEDs) and global
spectral properties. High-resolution X-ray imaging of PWNe shows a bewildering
array of morphologies, with jets, trails, and other structures. Several of the
23 so far identified magnetars show evidence for continuous or sporadic
emission of material, sometimes associated with giant flares, and a few
possible "magnetar-wind nebulae" have been recently identified.Comment: 61 pages, 44 figures (reduced in quality for size reasons). Published
in Space Science Reviews, "Jets and Winds in Pulsar Wind Nebulae, Gamma-ray
Bursts and Blazars: Physics of Extreme Energy Release
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