Variability in Isotope Discrimination Factors in Coral Reef Fishes: Implications for Diet and Food Web Reconstruction

Interpretation of stable isotope ratios of carbon and nitrogen (δ13C and δ15N) is generally based on the assumption that with each trophic level there is a constant enrichment in the heavier isotope, leading to diet-tissue discrimination factors of 3.4‰ for 15N (ΔN) and ∼0.5‰ for 13C (ΔC). Diet-tissue discrimination factors determined from paired tissue and gut samples taken from 152 individuals from 26 fish species at Ningaloo Reef, Western Australia demonstrate a large amount of variability around constant values. While caution is necessary in using gut contents to represent diet due to the potential for high temporal variability, there were significant effects of trophic position and season that may also lead to variability in ΔN under natural conditions. Nitrogen enrichment increased significantly at higher trophic levels (higher tissue δ15N), with significantly higher ΔN in carnivorous species. Changes in diet led to significant changes in ΔN, but not tissue δ15N, between seasons for several species: Acanthurus triostegus, Chromis viridis, Parupeneus signatus and Pomacentrus moluccensis. These results confirm that the use of meta-analysis averages for ΔN is likely to be inappropriate for accurately determining diets and trophic relationships using tissue stable isotope ratios. Where feasible, discrimination factors should be directly quantified for each species and trophic link in question, acknowledging the potential for significant variation away from meta-analysis averages and, perhaps, controlled laboratory diets and conditions

Short-selling ban and cross-sectoral contagion: Evidence from the UK

The UK?s Financial Services Authority introduced a ban on the short-selling of specified financial-sector stocks in September 2008. The regulator?s stated objectives were to protect market quality, stabilise the market for financial-sector stocks, and prevent cross-sectoral contagion. We analyse the price, market quality and contagion effects following the imposition of the short-selling ban, and its removal in January 2009. We report evidence consistent with a short-lived overpricing (underpricing) effect immediately after the ban was imposed (lifted). There is evidence of deterioration in market quality while the ban was in force. There is evidence of cross-sectoral contagion from the financial sector to the telecommunication sector immediately before the imposition of the ban, but there is no contagion for seven other non-financial sectors. There is no evidence of contagion while the ban was in force. In terms of preventing cross-sectoral contagion, the ban may be seen as a successful governance mechanism in the regulator?s toolbox.Peer reviewe

Building connectomes using diffusion MRI: why, how and but

Why has diffusion MRI become a principal modality for mapping connectomes in vivo? How do different image acquisition parameters, fiber tracking algorithms and other methodological choices affect connectome estimation? What are the main factors that dictate the success and failure of connectome reconstruction? These are some of the key questions that we aim to address in this review. We provide an overview of the key methods that can be used to estimate the nodes and edges of macroscale connectomes, and we discuss open problems and inherent limitations. We argue that diffusion MRI-based connectome mapping methods are still in their infancy and caution against blind application of deep white matter tractography due to the challenges inherent to connectome reconstruction. We review a number of studies that provide evidence of useful microstructural and network properties that can be extracted in various independent and biologically-relevant contexts. Finally, we highlight some of the key deficiencies of current macroscale connectome mapping methodologies and motivate future developments

The integrity of financial analysts:Evidence from asymmetric responses to earnings surprises

This paper investigates the integrity of financial analysts by examining their recommendation responses to large quarterly earnings surprises. Although there is no significant difference in recommendation changes between affiliated and unaffiliated analysts in response to positive earnings surprises, affiliated analysts are more reluctant than unaffiliated analysts to downgrade stock recommendations in response to negative earnings surprises. The evidence implies that conflicts of interest undermine the integrity of financial analysts. We further examine the effects of reputation concern and the Global Research Analyst Settlement as informal and formal mechanisms, on restoring analysts’ integrity. The results show that the positive bias in recommendations remains prevalent for affiliated analysts from reputable investment banks and for the postreform period. Finally, evidence from market reactions suggests that investors fail to notice that analysts’ integrity is compromised by conflicts of interest and are misled by affiliated analysts