Inter-comparison of salt effect correction for δ 18 O and δ 2 H measurements in seawater by CRDS and IRMS using the gas-H 2 O equilibration method

The isotope composition of seawater is an efficient method for detecting mixing between water masses. To measure long term or large scale hydrological processes at the ocean surface, it is necessary to be able to precisely compare datasets produced by different laboratories. The oxygen and hydrogen isotope (δ18O and δ2H) composition of marine waters can be measured using isotope ratio mass spectrometry (IRMS) and near-infrared laser absorption spectroscopy (LS) techniques. The IRMS and equilibration method is thought to provide results on the activity scale, while LS provides results on the concentration scale. However, the effect of dissolved seawater salts on the measurement is not sufficiently assessed and seems sometimes contradictory in the literature. For this purpose, we made artificial seawater and a pure NaCl solution from a freshwater of known isotope composition. The solutions were measured by four different laboratories allowing us to compare the two techniques. We show that minor corrections are necessary to correct seawater measurements for the salt effect and report them on the concentration scale. Interestingly, seawater measurements using LS (type Picarro) coupled to a liner are not on the concentration scale and require a correction of ~ 0.09‰ for δ18O, while the correction is relatively less significant for δ2H (~ 0.13‰). Moreover, we found for IRMS measurements that the salt effect can differ between different laboratories but seems reproducible for a given laboratory. A natural sea water sample was then analyzed by the different laboratories participating in the study. We found that applying the corrections increases the reproducibility of the isotope measurement significantly, with inter-laboratory standard deviation decreasing from 0.06 to 0.02‰ and 0.55 to 0.23‰ for δ18O and δ2H, respectively. Thus, comparing sea water datasets produced in different laboratories requires that each laboratory carries out its own calibration with artificial seawater and presents measurements on the concentration scale

Contracting on litigation

Two risk‐averse litigants with different subjective beliefs negotiate in the shadow of a pending trial. Through contingent contracts, the litigants can mitigate risk and/or speculate on the trial outcome. Contingent contracting decreases the settlement rate and increases the volume and costs of litigation. These contingent contracts mimic the services provided by third‐party investors, including litigation funders and insurance companies. The litigants (weakly) prefer to contract with risk‐neutral third parties when the capital market is transaction‐cost free. However, contracting with third parties further decreases the settlement rate, increases the costs of litigation, and may increase the aggregate cost of risk bearing.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149242/1/rand12274.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149242/2/rand12274_am.pd

The impact of news on measures of undiversifiable risk: evidence from the UK stock market

Using UK equity index data, this paper considers the impact of news on time varying measures of beta, the usual measure of undiversifiable risk. The empirical model implies that beta depends on news about the market and news about the sector. The asymmetric response of beta to news about the market is consistent across all sectors considered. Recent research is divided as to whether abnormalities in equity returns arise from changes in expected returns in an efficient market or over-reactions to new information. The evidence suggests that such abnormalities may be due to changes in expected returns caused by time-variation and asymmetry in beta

Examining the Impact of STR Weekly RevPAR Announcements on Lodging Stock Returns

This study investigated whether or not there were abnormal stock market returns on the announcement date of weekly RevPAR (revenue per available room) data by the lodging industry research firm STR. Using event study methodology, the study found that there were not statistically significant abnormal returns on the weekly RevPAR announcement date for the period from 2004 to 2009. The implications of this study are important to the hotel investment community including lodging stock owners and investors, stock analysts, investment bankers, and consultants as it indicates that there is not advance trading in lodging stocks based on the STR weekly RevPAR announcements

Identifying allosteric fluctuation transitions between different protein conformational states as applied to Cyclin Dependent Kinase 2

BACKGROUND: The mechanisms underlying protein function and associated conformational change are dominated by a series of local entropy fluctuations affecting the global structure yet are mediated by only a few key residues. Transitional Dynamic Analysis (TDA) is a new method to detect these changes in local protein flexibility between different conformations arising from, for example, ligand binding. Additionally, Positional Impact Vertex for Entropy Transfer (PIVET) uses TDA to identify important residue contact changes that have a large impact on global fluctuation. We demonstrate the utility of these methods for Cyclin-dependent kinase 2 (CDK2), a system with crystal structures of this protein in multiple functionally relevant conformations and experimental data revealing the importance of local fluctuation changes for protein function. RESULTS: TDA and PIVET successfully identified select residues that are responsible for conformation specific regional fluctuation in the activation cycle of Cyclin Dependent Kinase 2 (CDK2). The detected local changes in protein flexibility have been experimentally confirmed to be essential for the regulation and function of the kinase. The methodologies also highlighted possible errors in previous molecular dynamic simulations that need to be resolved in order to understand this key player in cell cycle regulation. Finally, the use of entropy compensation as a possible allosteric mechanism for protein function is reported for CDK2. CONCLUSION: The methodologies embodied in TDA and PIVET provide a quick approach to identify local fluctuation change important for protein function and residue contacts that contributes to these changes. Further, these approaches can be used to check for possible errors in protein dynamic simulations and have the potential to facilitate a better understanding of the contribution of entropy to protein allostery and function