Theoretical investigation of the mechanism, chemo- and stereospecifity in the epoxidation reaction of limonene with meta-chloroperoxybenzoic acid (m-CPBA)

The epoxidation of limonene 1 with m-CPBA has been examined within the MEDT at the B3LYP/6-311(d,p) computational level. The chemo- and stereoisomeric reaction paths involving the two C=C double bonds of limonene have been scrutinized. DFT computations account for the high chemospecifity involving the C1=C2 double bond and the stereospecifity, in complete conformity with the experimental results. An ELF analysis of the epoxidation shows the formation of the epoxide ring taking place of the two new C-O single bonds is somewhat asynchronous

Dynamic modelling of the behaviour of the quarkiss earthen dam under seismic loads

The dynamic modelling of the behaviour of the Ouarkiss earthen dam under seismic loads was performed using the finite elements method (FEM), with an approach in effective stresses. The soil behaviour is described by the Mohr-Coulomb criterion. A numerical method and a procedure of analysis are presented in this work. The seismic response of an earthen dam was evaluated. Particular emphasis is placed on the calculation of stresses, displacements, deformations and interstitial overpressures recorded during the seismic solicitation. It has been shown that numerical simulation is able to highlight the fundamental aspects of the displacements and deformations processes experienced by the structure ofdam and to produce preliminary results for the evaluation of the seismic behaviour of the structure taking into account the physical non-linearity of the materials constituting the body of the dam and the effect of the rigidity of the different zones of the dam and the foundation

The regio- and stereoselective addition of dibromocarbene and dichlorocarbene onto β-himachalene

In this work we used DFT B3LYP/6-31G (d) to study the mechanism, the regio- and stereoselectivity of the [1+2] cycloaddition reaction between β-himachalene and dihalogenocarbene. Analysis of the reactivity indices and calculation of the activation energies of the transition states showed that this reaction is stereoselectives, the treatment of β-himachalene with one equivalent of dibromocarbene leads via an exothermic reaction to the formation of a single product P1 resulting from the attack of the most substituted double bond C6=C7 of β-himachalene. Treatment of product P1 with one equivalent of dichlorocarbene leads, again via an exothermic reaction, to formation of the two products P3 and P4, but dibromocarbene does not react with the product P1 due to the high activation energy of this reaction

Understanding the Regioselectivity and Reactivity of Friedel–Crafts benzoylation Using Parr Functions

A theoretical study of the reactivity and regioselectivity of some aromatic compounds in electrophilic aromatic substitution is carried out at the B3LYP/6-31G(d) computational level. The relative reactivity of these systems is rationalized by means of the global nucleophilicity index proposed by Domingo’s group. The positional selectivity, namely o, m or p, is predicted by means of the local nucleophilicity indices [Parr fonctions]. The present study shows that the experimental trends of the relative reactivities and regioselectivities of these reactions are correctly predicted using Parr fonctions

(4aS,10aS)-7-Hydr­oxy-8-isopropyl-1,1,4a-trimethyl-1,2,3,4,4a,9,10,10a-octa­hydro­phenanthrene: a new diterpenoid compound

The new title diterpenoid compound, C20H30O, is a natural product isolated from Tetra­clinis articulata wood via chloro­form extraction. The asymmetric unit contains four mol­ecules with the same S,S configuration, deduced from the chemical synthesis. Indeed, an overlay analysis, calculated using structure-matching software, shows that the four mol­ecules can be superimposed. The central ring has a half-chair conformation, whereas the saturated ring displays a chair conformation

Impact of the Four Quality "Training, Service, Information System and Information" on the Use of Information System in an Information-Intensive Sector

Today, information is crucial and the flow of information is becoming more and more numerous, so their management is delicate, hence the need to use an information system that supports all production systems, and the majority of competitive advantages is achieved through the intelligent use of these information systems.It is in this context of disrupted information that the use of information systems is necessary in organizations, as they have greatly influenced the ways of work and management. For this purpose, they allow easy access to relevant information in quantity and in real time, the rapidity of analyzing this information and the possibilities for dissemination and exchange between the partners, without forgetting the possibilities for storage and archiving in a more secure way than human intervention could.The study examines the impact of quality of training, service quality, information system quality and information quality on the use of an information system. A quantitative study is conducted to test these effects, the findings of this research are mainly comprised by three facts: (1) the use of information systems is obligatory in the context of intensive information. (2) Voluntary or mandatory use status must be specified in the analysis, (3) there is no specific antecedent to the act of use of IS in the retail secto

Predicting the notch band frequency of an ultra-wideband antenna using artificial neural networks

In this paper we propose to predict the notch frequency of an ultra-wideband (UWB) antenna which operates in the frequency band from 3.85 GHz to 12.38 GHz. The prediction of the notch frequency in order to avoid interferences between (WLAN) IEEE802.11a and HIPERLAN/2 WLAN applications and UWB technology is achieved using the artificial neural networks (ANN) technique. The developed ANN is optimized with the help of K-fold cross validation method which allows us to divide the datasets into 10 subsets in the training phase. The simulated datasets are generated by controlling high frequency structural simulator (HFSS) from MATLAB using a VB script. The performance of the ANN technique is assessed using some statistical criteria. During the training process, the mean absolute percentage error (MAPE) between the simulated and the predicted ANN notch frequencies is 0,125. A comparison between simulated, theoretical, and ANN results has been achieved during the test and validation process, good accuracy is obtained between the simulated and the ANN predictions. The proposed UWB antenna exhibits a notch band from 5.1 GHz to 6.0 GHz with a notch frequency of approximately 5.51 GHz

Ultrasound study of Moroccan Arabic labiovelarization

In this survey, we have provided some acoustic and ultrasound data from two subjects to characterize a secondary articulation generally analyzed as labialization in Moroccan Arabic. Our results show that the so-called labialized consonants are rather labiovelarized. They also show that the vowel [a] adjacent to the labiovelarized consonants is velarized