A risk-averse manager's overconfidence makes him less conservative. As a result, it is cheaper for firms to motivate him to pursue valuable risky projects. When compensation endogenously adjusts to ...reflect outside opportunities, moderate levels of overconfidence lead firms to offer the manager flatter compensation contracts that make him better off. Overconfident managers are also more attractive to firms than their rational counterparts because overconfidence commits them to exert effort to learn about projects. Still, too much overconfidence is detrimental to the manager since it leads him to accept highly convex compensation contracts that expose him to excessive risk.
Consumption of fruit and vegetable products is commonly viewed as a potential risk factor for infection with enteropathogens such as Salmonella and Escherichia coli O157, with recent outbreaks linked ...to lettuce, spinach and tomatoes. Routes of contamination are varied and include application of organic wastes to agricultural land as fertilizer, contamination of waters used for irrigation with faecal material, direct contamination by livestock, wild animals and birds and postharvest issues such as worker hygiene. The ability of pathogens to survive in the field environment has been well studied, leading to the implementation of guidelines such as the Safe Sludge Matrix, which aim to limit the likelihood of viable pathogens remaining at point-of-sale. The behaviour of enteropathogens in the phyllosphere is a growing field of research, and it is suggested that inclusion in phyllosphere biofilms or internalization within the plant augments the survival. Improved knowledge of plant-microbe interactions and the interaction between epiphytic and immigrant micro-organisms on the leaf surface will lead to novel methods to limit enteropathogen survival in the phyllosphere.
People who are highly anxious about undergoing dental treatment comprise approximately one in seven of the population and require careful and considerate management by dental practitioners. This ...paper presents a review of a number of non‐pharmacological (behavioural and cognitive) techniques that can be used in the dental clinic or surgery in order to assist anxious individuals obtain needed dental care. Practical advice for managing anxious patients is provided and the evidence base for the various approaches is examined and summarized. The importance of firstly identifying dental fear and then understanding its aetiology, nature and associated components is stressed. Anxiety management techniques range from good communication and establishing rapport to the use of systematic desensitization and hypnosis. Some techniques require specialist training but many others could usefully be adopted for all dental patients, regardless of their known level of dental anxiety. It is concluded that successfully managing dentally fearful individuals is achievable for clinicians but requires a greater level of understanding, good communication and a phased treatment approach. There is an acceptable evidence base for several non‐pharmacological anxiety management practices to help augment dental practitioners providing care to anxious or fearful children and adults.
The concentration of radiocarbon (14C) differs between ocean and atmosphere. Radiocarbon determinations from samples which obtained their 14C in the marine environment therefore need a ...marine-specific calibration curve and cannot be calibrated directly against the atmospheric-based IntCal20 curve. This paper presents Marine20, an update to the internationally agreed marine radiocarbon age calibration curve that provides a non-polar global-average marine record of radiocarbon from 0–55 cal kBP and serves as a baseline for regional oceanic variation. Marine20 is intended for calibration of marine radiocarbon samples from non-polar regions; it is not suitable for calibration in polar regions where variability in sea ice extent, ocean upwelling and air-sea gas exchange may have caused larger changes to concentrations of marine radiocarbon. The Marine20 curve is based upon 500 simulations with an ocean/atmosphere/biosphere box-model of the global carbon cycle that has been forced by posterior realizations of our Northern Hemispheric atmospheric IntCal20 14C curve and reconstructed changes in CO2 obtained from ice core data. These forcings enable us to incorporate carbon cycle dynamics and temporal changes in the atmospheric 14C level. The box-model simulations of the global-average marine radiocarbon reservoir age are similar to those of a more complex three-dimensional ocean general circulation model. However, simplicity and speed of the box model allow us to use a Monte Carlo approach to rigorously propagate the uncertainty in both the historic concentration of atmospheric 14C and other key parameters of the carbon cycle through to our final Marine20 calibration curve. This robust propagation of uncertainty is fundamental to providing reliable precision for the radiocarbon age calibration of marine based samples. We make a first step towards deconvolving the contributions of different processes to the total uncertainty; discuss the main differences of Marine20 from the previous age calibration curve Marine13; and identify the limitations of our approach together with key areas for further work. The updated values for ΔR, the regional marine radiocarbon reservoir age corrections required to calibrate against Marine20, can be found at the data base http://calib.org/marine/.
Deep learning for finance: deep portfolios Heaton, J. B.; Polson, N. G.; Witte, J. H.
Applied stochastic models in business and industry,
January/February 2017, Letnik:
33, Številka:
1
Journal Article
Early researchers of radiocarbon levels in Southern Hemisphere tree rings identified a variable North-South hemispheric offset, necessitating construction of a separate radiocarbon calibration curve ...for the South. We present here SHCal20, a revised calibration curve from 0–55,000 cal BP, based upon SHCal13 and fortified by the addition of 14 new tree-ring data sets in the 2140–0, 3520–3453, 3608–3590 and 13,140–11,375 cal BP time intervals. We detail the statistical approaches used for curve construction and present recommendations for the use of the Northern Hemisphere curve (IntCal20), the Southern Hemisphere curve (SHCal20) and suggest where application of an equal mixture of the curves might be more appropriate. Using our Bayesian spline with errors-in-variables methodology, and based upon a comparison of Southern Hemisphere tree-ring data compared with contemporaneous Northern Hemisphere data, we estimate the mean Southern Hemisphere offset to be 36 ± 27 14C yrs older.
The Gaussian process is an indispensable tool for spatial data analysts. The onset of the “big data” era, however, has lead to the traditional Gaussian process being computationally infeasible for ...modern spatial data. As such, various alternatives to the full Gaussian process that are more amenable to handling big spatial data have been proposed. These modern methods often exploit low-rank structures and/or multi-core and multi-threaded computing environments to facilitate computation. This study provides, first, an introductory overview of several methods for analyzing large spatial data. Second, this study describes the results of a predictive competition among the described methods as implemented by different groups with strong expertise in the methodology. Specifically, each research group was provided with two training datasets (one simulated and one observed) along with a set of prediction locations. Each group then wrote their own implementation of their method to produce predictions at the given location and each was subsequently run on a common computing environment. The methods were then compared in terms of various predictive diagnostics.
ABSTRACT
The triggering mechanism for the most luminous, quasar-like active galactic nuclei (AGN) remains a source of debate, with some studies favouring triggering via galaxy mergers, but others ...finding little evidence to support this mechanism. Here, we present deep Isaac Newton Telescope/Wide Field Camera imaging observations of a complete sample of 48 optically selected type 2 quasars – the QSOFEED sample ($L_{\rm O\, \small {III}}\gt 10^{8.5}\, \mathrm{L}_{\odot }$; z < 0.14). Based on visual inspection by eight classifiers, we find clear evidence that galaxy interactions are the dominant triggering mechanism for quasar activity in the local universe, with 65$^{+6}_{-7}$ per cent of the type 2 quasar hosts showing morphological features consistent with galaxy mergers or encounters, compared with only 22$^{+5}_{-4}$ per cent of a stellar-mass- and redshift-matched comparison sample of non-AGN galaxies – a 5σ difference. The type 2 quasar hosts are a factor of 3.0$^{+0.5}_{-0.8}$ more likely to be morphologically disturbed than their matched non-AGN counterparts, similar to our previous results for powerful 3CR radio AGN of comparable O iii emission-line luminosity and redshift. In contrast to the idea that quasars are triggered at the peaks of galaxy mergers as the two nuclei coalesce, and only become visible post-coalescence, the majority of morphologically disturbed type 2 quasar sources in our sample are observed in the pre-coalescence phase (61$^{+8}_{-9}$ per cent). We argue that much of the apparent ambiguity that surrounds observational results in this field is a result of differences in the surface brightness depths of the observations, combined with the effects of cosmological surface brightness dimming.
Beyond ~13.9 cal kBP, the IntCal20 radiocarbon (14C) calibration curve is based upon combining data across a range of different archives including corals and planktic foraminifera. In order to ...reliably incorporate such marine data into an atmospheric curve, we need to resolve these records into their constituent atmospheric signal and marine reservoir age. We present results of marine reservoir age simulations enabling this resolution, applying the LSG ocean general circulation model forced with various climatic background conditions and with atmospheric radiocarbon changes according to the Hulu Cave speleothem record. Simulating the spatiotemporal evolution of reservoir ages between 54,000 and 10,700 cal BP, we find reservoir ages between 500 and 1400 yr in the low- and mid-latitudes, but also more than 3000 yr in the polar seas. Our results are broadly in agreement with available marine radiocarbon reconstructions, with the caveat that continental margins, marginal seas, or tropical lagoons are not properly resolved in our coarse-resolution model.
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