Theoretical Study on Non-Linear Optics Properties of Polycyclic Aromatic Hydrocarbons and the Effect of Their Intercalation with Carbon Nanotubes

Results of a theoretical study devoted to comparing NLO (non-linear optics) responses of derivatives of tetracene, isochrysene, and pyrene are reported. The static hyperpolarizability β, the dipole moment μ, the HOMO and LUMO orbitals, and their energy gap were calculated using the CAM-B3LYP density functional combined with the cc-pVDZ basis set. The para-disubstituted NO2-tetracene-N(CH3)2 has the highest NLO response, which is related to a large intramolecular charge transfer. Adding vinyl groups to the para-disubstituted NO2-tetracene-N(CH3)2 results in an increase in the NLO responses. We further investigated the effect of the intercalation of various push–pull molecules inside an armchair single-walled carbon nanotube. The intercalation leads to increased NLO responses, something that depends critically on the position of the guest molecule and/or on functionalization of the nanotube by donor and attractor groups.</p

Algerian Acid Activated Clays as Efficient Catalysts for a Green Synthesis of Solketal by Chemoselective Acetalization of Glycerol with Acetone

The production of solketal and conversion of glycerol takes a major importance in the field of the sustainability of the biodiesel industry. The synthesis of (2,2-dimethyl-1,3-dioxolan-4-yl)methanol by the acetalization of glycerol with acetone successfully applied out using various Algerian acid activated clays (maghnia-H+) under autogenous pressure and without solvent. The acid catalyst clays are prepared by an easy technique by activation with the available and low-cost Maghnia clay. The purified Maghnia clay named ALC and the resulting series of acid-activated clays AL1, AL2, AL3, and AL4 are characterized by X-ray Fluorescence (XRF) investigation, N2-adorption/desorption Brunauer–Emmett–Teller  (BET) surface area, X-rays Diffraction (XRD), Fourier Transform Infra Red (FT-IR) spectroscopy, SEM microscopy and the cation exchange capacity (CEC) with copper bisethylenediamine complex method, in order to study the effect of activation at the acid and the catalytic behaviour in the acetalization reaction. The results show a high catalytic activity whose that the yield of solketal production interest reached 95 % at a temperature of 40 °C for a reaction time of 48 hours with full selectivity and glycerol conversion reaching up to 89 %. A mechanistic is proposed to explain the chemoselective of solketal production. These results indicate the potential of this Algerian acid activated clays catalysts for the acetalization of glycerol for an environmentally benign process. Copyright © 2019 BCREC Group. All rights reserved

Le changement organisationnel et la transformation digitale : Quelle relation ?

In a disruptive world, digital transformation has become a major concern for organizations both nationally and internationally. In order to exploit the potential of these new technologies, they need to change their current model to adapt quickly to the changing environment, and to do so through the path of digital transformation. To this end, we consider digital transformation to be a complex and difficult process of change, a matter of the moment and an urgent necessity. This leads us to propose the following research problem: to what extent do organizational change models enable digital transformation to be carried out? The problematic raised by this article is firstly to establish a link between the change management models from the literature on organizational change and the management of digital transformation. Secondly, through this paper we contribute to the research on change management models in a context marked by a strong orientation of organizations towards digital transformation, by identifying a set of key factors from the existing models that can be used to manage digital transformation. The results revealed by this study demonstrate that digital transformation leads to organizational change. These results will be used as a benchmark to reflect on whether organizational change models can be used to drive digital transformation in a future scientific contribution. Keywords : digital transformation, organizational change, change management models, key success factors JEL Classification&nbsp;: H75, O30 Paper type: Theoretical ResearchDans un monde en pleine disruption, la transformation digitale est devenue une préoccupation majeure pour les organisations que ce soit à l’échelle nationale et internationale. Afin qu’elles puissent exploiter le potentiel de ces nouvelles technologies, elles doivent changer leur modèle actuel pour s’adapter rapidement aux changements de l’environnement, et cela en empruntant le chemin de la transformation digitale. À cet effet, nous considérons la transformation digitale comme un processus de changement complexe et difficile à mettre en œuvre, il s’agit en effet d’un sujet de l’heure et d’une nécessité urgente. Ce qui nous impose à proposer la problématique de recherche suivante&nbsp;: dans quelle mesure les modèles de changement organisationnel permettent de conduire une transformation digitale ? De par la problématique soulevée par cet article, nous cherchons en premier lieu à établir un lien, entre les modèles de conduite de changement issus de la littérature sur le changement organisationnel, et la conduite de la transformation digitale. En deuxième lieu, par le biais de cet article, nous contribuons à la recherche sur les modèles de conduite de changement dans un contexte marqué par une orientation forte des organisations vers la transformation digitale, et ce, par la détermination d’un ensemble de facteurs clé à partir des modèles existants, et qui peuvent servir à la conduite de la transformation digitale. Les résultats révélés par cette étude démontrent que la transformation digitale conduit à un changement organisationnel. Ces résultats vont nous servir comme repère pour réfléchir en étudiant dans une future contribution scientifique si les modèles de changement organisationnel permettent de conduire la transformation digitale. &nbsp; Mots-clés : transformation digitale, changement organisationnel, modèles de conduite de changement, facteurs clés de succès Classification JEL&nbsp;: H75, O30 Type de l’article&nbsp;: Article théorique

MRI of bone marrow abnormalities in hematological malignancies

Magnetic resonance imaging (MRI) is essential for evaluating bone marrow. Bone marrow undergoes constant modification and its appearance on MRI changes in response. Knowledge of the types of changes and their origins is essential for analysis of MRI findings of bone marrow infiltration with hematological malignancies. This pictorial review describes the MRI pulse sequences used for imaging of bone marrow, and illustrates bone marrow changes due hematological malignancies, including changes following treatment

SARS-CoV-2 susceptibility and COVID-19 disease severity are associated with genetic variants affecting gene expression in a variety of tissues

Variability in SARS-CoV-2 susceptibility and COVID-19 disease severity between individuals is partly due to genetic factors. Here, we identify 4 genomic loci with suggestive associations for SARS-CoV-2 susceptibility and 19 for COVID-19 disease severity. Four of these 23 loci likely have an ethnicity-specific component. Genome-wide association study (GWAS) signals in 11 loci colocalize with expression quantitative trait loci (eQTLs) associated with the expression of 20 genes in 62 tissues/cell types (range: 1:43 tissues/gene), including lung, brain, heart, muscle, and skin as well as the digestive system and immune system. We perform genetic fine mapping to compute 99% credible SNP sets, which identify 10 GWAS loci that have eight or fewer SNPs in the credible set, including three loci with one single likely causal SNP. Our study suggests that the diverse symptoms and disease severity of COVID-19 observed between individuals is associated with variants across the genome, affecting gene expression levels in a wide variety of tissue types

SARS-CoV-2 susceptibility and COVID-19 disease severity are associated with genetic variants affecting gene expression in a variety of tissues

Variability in SARS-CoV-2 susceptibility and COVID-19 disease severity between individuals is partly due to genetic factors. Here, we identify 4 genomic loci with suggestive associations for SARS-CoV-2 susceptibility and 19 for COVID-19 disease severity. Four of these 23 loci likely have an ethnicity-specific component. Genome-wide association study (GWAS) signals in 11 loci colocalize with expression quantitative trait loci (eQTLs) associated with the expression of 20 genes in 62 tissues/cell types (range: 1:43 tissues/gene), including lung, brain, heart, muscle, and skin as well as the digestive system and immune system. We perform genetic fine mapping to compute 99% credible SNP sets, which identify 10 GWAS loci that have eight or fewer SNPs in the credible set, including three loci with one single likely causal SNP. Our study suggests that the diverse symptoms and disease severity of COVID-19 observed between individuals is associated with variants across the genome, affecting gene expression levels in a wide variety of tissue types