Dynamic risk management

This article develops a dynamic risk management model to determine a firm's optimal risk management strategy. This strategy has two elements. First, for low-leverage values, the firm fully hedges its operating cash flow exposure, due to the convexity of its cost of capital. When leverage exceeds a very high threshold, the firm gambles for resurrection and stops hedging. Second, the firm manages its capital structure through dividend distributions and investment. When leverage is low, the firm replaces depreciated assets, fully invests in opportunities if they arise, and distribute dividends, all of these together to achieve its optimal capital structure. As leverage increases, the firm stops paying dividends, while fully investing. After a certain leverage, the firm also reduces investment until it stops investing completely. The model predictions are consistent with empirical observation

Data Sharing and Research on Peer Review: A Call to Action

While recent surveys show that most stakeholders recognise the importance of peer review to the publication process, there is a lack of systematic research on the topic. In a period of hyper-competition for resources, with perverse incentives that lead to academic capitalism and a \u201cpublish or perish\u201d mentality, the lack of robust and cumulative research on approaches, models and practices of peer review can slow down efforts towards fostering research integrity and the credibility of scholarly communication. A major challenge in studying peer review systematically is the lack of available data. While data sharing in scientific research has made relevant progress in certain fields, the lack of infrastructures to promote the sharing of peer review data among publishers, journals and academic scholars, the challenges posed by privacy and data protection legislation, and the perceived lack of incentives for publishers, learned societies and journals to share data, have all hampered efforts in this important domain. While public authorities, learned societies and publishers may face different priorities, incentives and obstacles regarding data sharing, the time has come to call to action all stakeholders who play a part in this field. In this paper, we argue that an infrastructure for data sharing is needed to stimulate independent, collaborative, public research on peer review and we suggest measures and initiatives to set up a collaborative effort towards this goal

Recent Advances and Future Prospects of Serial Crystallography using XFEL and synchrotron X-ray sources

Protein structure determination at the atomic level is an essential step for understanding protein functions and developing new drugs. However, growing crystals of sufficient quality and size necessary to obtain good diffraction patterns is a significant bottleneck. The advent of X-ray free electron lasers (XFELs) has made it possible to collect high quality X-ray diffraction patterns from nano- or micro-sized crystals because a typical XFEL pulse is intense enough to provide a diffraction pattern from such small sized crystals and is temporally short (less than 50 femtoseconds) enough to collect the diffraction pattern prior to crystal destruction or significant radiation damage. A combination of this idea and a continuous sample delivery system supplying a fresh crystal for every X-ray pulse provides a nascent field of serial femtosecond crystallography (SFX). The concept of serial crystallography (SX) is also being adapted in conventional micro- and nanofocused synchrotron beamlines, resulting in serial synchrotron crystallography (SSX). In this review, we survey and examine a variety of currently available sample delivery systems in SFX and SSX and discuss their advantages and drawbacks. We also review the protein systems studied by SFX and SSX and various protein crystallization techniques that are particularly useful for membrane proteins in the application with SFX and SSX. Finally, we highlight the applicability of the SFX and SSX methods for time-resolved studies, which offer notable new possibilities for tracking both the reversible and irreversible structural dynamics of proteins at the atomic level in real time. SSX and SFX may revolutionize the field of structural biology. © 2015 Bio Design22Nothe

Etude physique et théorique des matériaux à changement de phase pour disques optiques

Le thème de cette thèse s'inscrit dans l'étude et le développement de la technologie de l'enregistrement optique réversible par changement de phase (technologie des DVD-RAM). La compréhension des phénomènes physiques intervenant dans les processus d'écriture et d'effacement des dommées est aujourd'hui indispensable pour permettre le développement des DVD de demain. La très forte interactions entre les aspects optique, thermique, thermodynamique et cinétique des transitions de phase impliqués dans des systèmes e couches minces nous a conduit à mettre en place des modèles pour chacun de ces aspects puis à coupler ces différents phénomènes dans une simulation globale; celle-ci permettant d'analyser avec précision les mécanismes et les paramètres influençant les processus d'amorphisation et de cristallisation qui régissent respectivement les opérations d'écriture et d'effacement. Cette simulation a été construite à partir d'un support expérimental varié : dépôt de couches minces, caractérisation optique d ces couches, caractérisation structurale : microscopie électronique à transmission, diffraction des rayons X, EXAFS.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Multireference Ab Initio Study of the Ground and Low-LyingExcited States of Cr(CO)2 and Cr(CO)3

We investigate the ground and low-lying excited states of unsaturated chromium carbonyls, Cr(CO)2 and Cr(CO)3, using multiconfigurational ab initio perturbation theory. Unlike other chromium carbonyls, there are discrepancies between the experiment and theory on the identity of the ground states of Cr(CO)2 and Cr(CO)3. From multireference ab initio calculations considering the full valence orbitals of Cr(CO)2 and Cr(CO)3, the differences in the molecular structures of their various electronic states are explained by the electronic structure analysis. On the basis of the result from CASPT2 and MS-CASPT2 calculations, we propose that the ground states of Cr(CO)2 and Cr(CO)3 are the 5Πg and 1A1 states, respectively, addressing the ambiguity regarding their ground states. In addition, the multiconfigurational ab initio perturbation theory calculations reveal that (1) the energy gaps between the ground and first low-lying excited states of Cr(CO)2 and Cr(CO)3 are quite small and (2) the first low-lying excited states of Cr(CO)2 and Cr(CO)3 have the same spin multiplicities as the ground states of CrCO and Cr(CO)2, respectively, which are the products of ligand dissociation. As a result, the apparent spin-forbidden dissociation of Cr(CO)2 and Cr(CO)3 into CrCO and Cr(CO)2, respectively, are likely to be facilitated by thermal excitation of the ground states of Cr(CO)2 and Cr(CO)3 into their first low-lying excited states, which then actually undergoes the spinallowed dissociation to the ground states of CrCO and Cr(CO)2 with the same spin multiplicities.1221sciescopu