Experimental settlement and dynamic behavior of a portion of ballasted railway track under high speed trains

International audienceThe study of railway tracks under high speed trains is one of the most important researches in the domain of transport. A reduced scale experiment with three sleepers is presented to study the dynamic behavior and the settlement of ballasted tracks. A large number of trains passing at high speeds are simulated by signals, applied with the help of hydraulic jacks, having the shape of the letter M and representing the passages of bogies on sleepers. This experiment offers results such as displacements, accelerations, pressures and settlements that allow to better understand the dynamic behavior of a portion of a ballasted railway track at reduced scale and to estimate the settlement versus the number of load cycles. It was found that mechanical properties such as the global stiffness of the track can have important variations during the experiment. The settlement was also found to be a function of the acceleration of sleepers and above all it was observed, for accelerations above a critical value, that the increase of settlement per cycle was very high

Do shareholders punish or reward excessive CSR engagement? The moderating effect of cash flow and firm growth

Although extensive past research has studied the connection between corporate social responsibility (CSR) and firm value, it has rarely discriminated between optimal and excessive CSR. Thus, we addressed this issue by examining whether shareholders punish or reward excessive CSR engagement through the moderating effect of cash flow and firm growth. We applied country–industry–year fixed-effects (FE) regression to a cross-country sample of 43,803 firm-year observations between 2002 and 2019. The findings show that while both optimal and excessive CSR increase firm value, optimal CSR has greater value relevance than excessive CSR for shareholders. However, although cash flow positively moderates the relationship between optimal and excessive CSR and firm value, firm growth negatively moderates this relationship. The findings are robust regarding alternative CSR proxies, industry-adjusted firm value measures, public governance indicators, and endogeneity concerns

Corporate strategy, board composition, and firm value

This study addressed a gap in the literature by investigating the link between corporate strategy and board composition and how it connects to firm value. Most studies have explored whether board structure predicts firm outcomes rather than the other way around even though firm strategy plays a significant role in structuring the board. The sample covered the period between 2013 and 2018 and included 20,677 firm-year observations, on which we executed country-industry-year fixed-effects regression analysis. We found that, first, cost leadership strategy was positively associated with board size, board independence, board gender diversity, and board tenure, whereas it was negatively associated with board skills. Second, differentiation strategy was positively associated with board size and board gender diversity. Third, the moderating effects revealed that while board size and board tenure negatively moderated between cost leadership and firm value, board skills positively moderated between cost leadership and firm value. On the other hand, while board size, board gender diversity, and board tenure positively moderated between differentiation and firm value, board skills negatively moderated between differentiation and firm value. The results were robust to an alternative firm value proxy and endogeneity concerns. These findings provide firms with the opportunity to better shape their board structure in line with their corporate strategies and shareholder expectations

The Promise of Molecular and Genomic Techniques for Biodiversity Research and DNA Barcoding of the Arabian Peninsula Flora

The Arabian Peninsula is known to have a comprehensive and rich endowment of unique and genetically diverse plant genetic resources. Analysis and conservation of biological diversity is a crucial issue to the whole Arabian Peninsula. The rapid and accurate delimitation and identification of a species is crucial to genetic diversity analysis and the first critical step in the assessment of distribution, population abundance and threats related to a particular target species. During the last two decades, classical strategies of evaluating genetic variability, such as morphology and physiology, have been greatly complemented by phylogenetic, taxonomic, genetic diversity and breeding research molecular studies. At present, initiatives are taking place around the world to generate DNA barcode libraries for vascular plant flora and to make these data available in order to better understand, conserve and utilize biodiversity. The number of herbarium collection-based plant evolutionary genetics and genomics studies being conducted has been increasing worldwide. The herbaria provide a rich resource of already preserved and identified material, and these as well as freshly collected samples from the wild can be used for creating a reference DNA barcode library for the vascular plant flora of a region. This review discusses the main molecular and genomic techniques used in plant identification and biodiversity analysis. Hence, we highlight studies emphasizing various molecular techniques undertaken during the last 10 years to study the plant biodiversity of the Arabian Peninsula. Special emphasis on the role of DNA barcoding as a powerful tool for plant biodiversity analysis is provided, along with the crucial role of herbaria in creating a DNA barcode library

Reflecting on Hybrid Events: Learning from a Year of Hybrid Experiences

The COVID-19 pandemic led to a sudden shift to virtual work and events, with the last two years enabling an appropriated and rather simulated togetherness - the hybrid mode. As we return to in-person events, it is important to reflect on not only what we learned about technologies and social justice, but about the types of events we desire, and how to re-design them accordingly. This SIG aims to reflect on hybrid events and their execution: scaling them across sectors, communities, and industries; considering trade-offs when choosing technologies; studying best practices and defining measures of "success"for hybrid events; and finally, identifying and charting the wider social, ethical, and legal implications of hybrid formats. This SIG will consolidate these topics by inviting participants to collaboratively reflect on previous hybrid experiences and what can be learned from them

TOXICOLOGICAL AND PHARMACOLOGICAL ASSESSMENT OF GOLD NANORODS IN NORMAL RATS

Objective: assessment of acute, subchronic and chronic toxicity of pegylated gold nanorods (PEG-gold NRs) in Wistar rats of both sex in three routes of administration {intravenous (IV), intramuscular (IM) and subcutaneous (SC)}.Methods: in the acute toxicity study; PEG-gold NRs were injected once by three different routes, blood and tissue samples were collected after 14 d. In the subchronic and chronic studies; PEG-gold NRs were injected via three different routes, at 0.225, 0.45 and 0.9 mg/kg, once daily for 5 consecutive days, followed by a 23-day recovery period, for three and six months in the subchronic and chronic toxicity studies, respectively. Hematology, urinalysis, biochemical and histopathological examinations were conducted at the end of each study.Results: acute toxicity showed a significant decrease in serum triglycerides and cholesterol levels after single IV, IM and SC injection of PEG-gold NRs, while serum creatinine was significantly increased after IV and IM injection. Subchronic results revealed a significant decrease in serum triglycerides and cholesterol levels. The chronic study showed a significant decrease in serum triglycerides, sodium levels, total leukocytes count and significant increase in serum creatinine after IV injection. IM injection resulted in significant decrease in serum alkaline phosphatase, triglycerides, cholesterol, sodium levels and total leukocytes count. SC injection resulted in significant decrease in serum triglycerides, glucose, red blood cell count with increased creatinine and hematocrit.Conclusion: PEG-gold NRs at the three examined doses is apparently safe since no serious signs of toxicity were detected. IM and SC routes of injection were irritating, so we recommend the IV route.Â

Analyse des déformations permanentes des voies ferrées ballastées - Approche dynamique

The study of ballasted railway tracks behaviour under moving trains at high speeds is one of the most important researches in the domain of transport. Due to repeated passage of trains at high speeds, differential settlements are observed in the longitudinal direction of the railway track. These settlements depend on the platform quality, the rolling speed and the dynamical behaviour of the track. They can threaten the comfort and the security of passengers and need high costs of maintenance in order to return the track into its initial position. In order to progress in understanding the phenomenon of settlement, a reduced scale experiment of three sleepers is proposed. Sleepers are submitted into analytical forces of shape M by hydraulic jacks representing loads due to the passage of boogies. This experiment allows to measure several parameters such as displacements, accelerations and stresses in the embankment. It is modelled by the finite element method with linear elastic behaviours and two different zones of ballast (compacted and non compacted). Numerical results are determined by three-dimensional modeling and then compared to the experimental ones. The essential aim of this experiment is to establish a permanent settlement law for a large number of cycles depending on a dynamical parameter that can be determined by the three-dimensional numerical model.L'étude du comportement des voies ferrées ballastées sous les passages de trains à grandes vitesses est une des recherches les plus importantes dans le domaine des transports. À cause du passage répété de trains à grandes vitesses, des tassements verticaux différentiels sont observés tout au long de la voie ferrée. Ces tassements dépendent de la qualité de la plate-forme, de la vitesse de roulement ainsi que du comportement dynamique de la voie. Ils peuvent menacer le confort et la sécurité des passagers et nécessiter des coûts élevés de maintenance pour rendre la voie à sa géométrie initiale. Pour progresser dans la compréhension du phénomène de tassement, un essai à échelle réduite constitué de trois traverses est proposé. Les traverses sont mises en charge à l'aide de trois vérins hydrauliques fournissant des signaux ayant la forme de la lettre M qui simulent les passages de bogies. Cet essai permet de mesurer plusieurs paramètres tels que les déplacements, les accélérations et les contraintes dans l'éprouvette. Il est modélisé par la méthode des éléments finis avec des comportements élastiques linéaires et avec deux zones différentes de ballast (compactée et non compactée). Les résultats numériques déterminés grâce à un modèle tridimensionnel sont comparés à ceux de la mesure. Le but essentiel de cet essai est d'établir une loi de tassement vertical pour un grand nombre de cycles dépendant d'un paramètre dynamique qui peut être déterminé par le modèle numérique tridimensionnel

Cooling Performance of Heat Sinks Used in Electronic Devices

Existing passive cooling solutions limit the short-term thermal output of systems, thereby either limiting instantaneous performance or requiring active cooling solutions. As the temperature of the electronic devices increases, their failure rate increases. That’s why electrical devices should be cooled. Conventional electronic cooling systems usually consist of a metal heat sink coupled to a fan. This paper compares the heat distribution on a heat sink relative to different heat fluxes produced by electronic chips. The benefit of adding a fan is also investigated when high levels of heat generation are expected

Do board monitoring and audit committee quality help risky firms reduce CSR controversies?

This study focuses on potential inhibiting and driving factors of corporate social responsibility (CSR) controversies including board monitoring intensity and audit committee quality with a particular focus on risky firms. We draw on agency, resource dependence, and slack financial resources theories to explain this association. Using an international sample between 2002-2019 and executing fixed-effects regression and Hayes’s moderation analysis methodology, we find that risky firms tend to commit more CSR controversies. Furthermore, CSR performance, firm complexity, and indebtedness exacerbate CSR controversies, whereas larger boards mitigate them. Moreover, while board monitoring intensity and audit committee quality do not prevent committing CSR controversies in absolute terms, they alleviate risky firms' CSR controversies tendency. The findings confirm agency theory and the monitoring function of the board in mitigating CSR controversies. In line with the resource dependence theory, audit committees’ independent members and members with different skills and expertise provide critical resources that help prevent CSR controversies