IPO Waves: How Market Performances Influence The Market Timing Of IPO?

The goal of this paper is to study the impact of stock markets on Initial Public Offerings (IPOs).  Several studies have shown that the need for financing is not the main trigger for an IPO—favorable market conditions may play a more important part. This work prove the existence of a significate relationship between past stock market returns and the number of IPOs.  Before setting the date for an IPO, managers analyze long term financial market yields, a bullish stock market over a six month/ one year period encourages IPOs activities. In the other hand, even a negative performance but over a two-year period may have the same effect. They expect a stock market inversion. These results were obtained by autocorrelation analysis and count regression

Logical dynamical modelling of Fe-S cluster biogenesis in Escherichia coli

Les centres Fer-Soufre (Fe-S) sont des cofacteurs essentiels ubiquitaires conservés dans tous les domaines du vivant. La biogenèse des centres Fe-S est extrêmement sensible à la carence en fer et au stress oxydant provoqué notamment par l’H2O2. Deux machineries, Isc et Suf, permettent l’assemblage et le transfert des centres Fe-S sur les apo-protéines cibles. Chez la bactérie modèle E.coli, Isc est considérée comme la machinerie utilisée en absence de stress, tandis que Suf est celle agissant dans des conditions de stress.Dans ce travail de thèse, nous proposons un modèle mathématique du réseau de régulation contrôlant la biogenèse des centres Fe-S, basé sur le formalisme logique, afin de mieux comprendre les mécanismes de régulation ainsi que la dynamique de ce processus en fonction des conditions environnementales que sont le fer et l’oxygène.Nous avons construit un graphe de régulation représentant les interactions entre les principaux acteurs de la biogenèse. Le graphe a ensuite été paramétré à l’aide de règles logiques décrivant le comportement dynamique du système.Ce modèle logique est centré sur trois modules décrivant la biogenèse des centres Fe-S, l’homéostasie du fer, et le stress oxydant centré sur l'H2O2. Les nœuds d’entrée du modèle représentent les conditions extracellulaires de fer et d’oxygène, tandis que les noeuds ErpA, NfuA (transporteurs de centres Fe-S) et Suf sont les nœuds de sortie du modèle.Iron-sulfur (Fe-S) clusters are essential cofactors conserved in all domains of life. Fe-S biogenesis is extremely sensitive to stresses such as iron deprivation and oxidative stress, notably due to H2O2. Two machineries, Isc and Suf, allow the Fe-S assembly and their transfer to Fe-S proteins. In the model bacterium Escherichia coli, Isc is considered as the machinery used under optimal growth conditions, whereas Suf is used during stress.In this PhD thesis, we propose a logical mathematical model of the regulatory network controlling the Fe-S biogenesis process, in order to better understand the underlying regulatory mechanisms and the dynamics of the process depending on environmental factors such as iron and oxygen levels.In this PhD thesis, we propose a logical mathematical model of the regulatory network controlling the Fe-S biogenesis process, in order to better understand the underlying regulatory mechanisms and the dynamics of the process depending on environmental factors such as iron and oxygen levels.This logical model is centered on three modules describing the Fe-S biogenesis, the iron homeostasis module and the oxidative stress module centered on H2O2 response. The model inputs represent extracellular iron and oxygen environmental conditions, whereas ErpA, NfuA (Fe-S carrier proteins), and Suf are output nodes of the model.In addition to the enhancement of the crosstalks between the three modules mentioned above, the model provides several predictions such as the fact that perturbations of oxidative stress module affect iron homeostasis, but not vice versa

Understanding value characteristics toward a robust IT governance application in private organizations using COBIT framework

This research is an inquiry of Control Objectives for Information and Related Technologies (COBIT) as a high-level governance and control framework which was proposed by ITGI by providing incite and statistical evidence investigating whether ITGI pillars can be accounted for the same IT governance dimension. The data were collected via a questionnaire distributed to 40 private organizations in the Middle East, comprising a sample size of 179 respondents of strategic- and tactical-level managers. To investigate the research questions, the researchers apply an exploratory and confirmatory factor analyses using EQS 6.3 and SPSS 21. The findings of the research indicate that there is an awareness of the nature of the relationship that IT governance has with its various factors as suggested by the COBIT framework: business/IT alignment, IT value delivery, IT resource management, IT risk management and IT performance. The findings also revealed that “IT risk management” is the leading indicator in explaining the IT governance application behavior. The validated model of ITGOV shows that “IT business alignment” has the least significant impact on the study sample. The overall results illustrate the needs and the imperatives of the model factors in achieving a better understanding of the characteristic value of the ITGOV applications using the COBIT framework as suggested by ITGI

Enterprise System as Business Intelligence and Knowledge Capabilities for Enhancing Applications and Practices of IT Governance

According to different views in information systems and the socio-technical perspective, many organizations was led to redefine their business with a more focused IT solutions, this study suggested a number of confirmatory measurement models that establish the ground for the hypothesed research constructs, and utilized the structural equation modeling techniques to test and validate the research hypotheses. The research present the results of a practical investigation of the influence and the effect of enterprise systems role applications and organizational knowledge capabilities on IT governance practices by enhancing its application and usability within the organization. The study suggests that smart enterprise systems capabilities (infrastructure scalability, planning alignments, and HR planning and professional capabilities the IT staff) and knowledge organizational capabilities (individual, managerial, and collaborative) have a positive dynamic influence on IT governance activities. It's also observed that enterprise systems role applications have a more profound influence on organizational knowledge capabilities (OKC) comparing to IT governance (ITGOV), where OKC played a significate additive role in mediating the effect and thus provided an enhanced extra effect on IT governance

Analysis of a logical regulatory network reveals how Fe-S cluster biogenesis is controlled in the face of stress

International audienceIron-sulfur (Fe-S) clusters are important cofactors conserved in all domains of life, yet their synthesis and stability are compromised in stressful conditions such as iron deprivation or oxidative stress. Two conserved machineries, Isc and Suf, assemble and transfer Fe-S clusters to client proteins. The model bacterium Escherichia coli possesses both Isc and Suf, and in this bacterium utilization of these machineries is under the control of a complex regulatory network. To better understand the dynamics behind Fe-S cluster biogenesis in E. coli, we here built a logical model describing its regulatory network. This model comprises three biological processes: 1) Fe-S cluster biogenesis, containing Isc and Suf, the carriers NfuA and ErpA, and the transcription factor IscR, the main regulator of Fe-S clusters homeostasis; 2) iron homeostasis, containing the free intracellular iron regulated by the iron sensing regulator Fur and the non-coding regulatory RNA RyhB involved in iron sparing; 3) oxidative stress, representing intracellular H 2 O 2 accumulation, which activates OxyR, the regulator of catalases and peroxidases that decompose H 2 O 2 and limit the rate of the Fenton reaction. Analysis of this comprehensive model reveals a modular structure that displays five different types of system behaviors depending on environmental conditions, and provides a better understanding on how oxidative stress and iron homeostasis combine and control Fe-S cluster biogenesis. Using the model, we were able to predict that an iscR mutant would present growth defects in iron starvation due to partial inability to build Fe-S clusters, and we validated this prediction experimentally

A wnt2 ortholog in the sea urchin Paracentrotus lividus

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