41 research outputs found
Clustering Prediction Techniques in Defining and Predicting Customers Defection: The Case of E-Commerce Context
With the growth of the e-commerce sector, customers have more choices, a fact which encourages them to divide their purchases amongst several e-commerce sites and compare their competitorsâ products, yet this increases high risks of churning. A review of the literature on customer churning models reveals that no prior research had considered both partial and total defection in non-contractual online environments. Instead, they focused either on a total or partial defect. This study proposes a customer churn prediction model in an e-commerce context, wherein a clustering phase is based on the integration of the k-means method and the Length-Recency-Frequency-Monetary (LRFM) model. This phase is employed to define churn followed by a multi-class prediction phase based on three classification techniques: Simple decision tree, Artificial neural networks and Decision tree ensemble, in which the dependent variable classifies a particular customer into a customer continuing loyal buying patterns (Non-churned), a partial defector (Partially-churned), and a total defector (Totally-churned). Macro-averaging measures including average accuracy, macro-average of Precision, Recall, and F-1 are used to evaluate classifiersâ performance on 10-fold cross validation. Using real data from an online store, the results show the efficiency of decision tree ensemble model over the other models in identifying both future partial and total defection
Supercomplexes multifonctionnels chez les mitochondries, et chez E. coli
Les processus mitochondriaux tels que la rĂ©plication et la traduction sont effectuĂ©s par des complexes multiprotĂ©iques. Par contre, le mĂ©tabolisme et la voie de maturation des ARN mitochondriaux (p. ex prĂ©curseurs des ARNt et des ARNr) sont habituellement traitĂ©s comme une suite de rĂ©actions catalysĂ©es par des protĂ©ines sĂ©parĂ©es. LâexĂ©cution fidĂšle et optimale de ces processus mitochondriaux, exige un couplage Ă©troit nĂ©cessaire pour la canalisation des intermĂ©diaires mĂ©taboliques. Or, les Ă©vidences en faveur de l'interconnexion postulĂ©e de ces processus cellulaires sont peu nombreuses et proviennent en grande partie des interactions protĂ©ine-protĂ©ine.
Contrairement Ă la perception classique, nos rĂ©sultats rĂ©vĂšlent lâorganisation des fonctions cellulaires telles que la transcription, la traduction, le mĂ©tabolisme et la rĂ©gulation en supercomplexes multifonctionnels stables, dans les mitochondries des champignons (ex Saccharomyces cerevisiae, Aspergillus nidulans et Neurospora crassa), des animaux (ex Bos taurus), des plantes (B. oleracea et Arabidopsis thaliana) et chez les bactĂ©ries (ex E. coli) Ă partir desquelles les mitochondries descendent. La composition de ces supercomplexes chez les champignons et les animaux est comparable Ă celle de levure, toutefois, chez les plantes et E. coli ils comportent des diffĂ©rences notables (ex, prĂ©sence des enzymes spĂ©cifiques Ă la voie de biosynthĂšse des sucres et les lĂ©ctines chez B. oleracea).
Chez la levure, en accord avec les changements dĂ»s Ă la rĂ©pression catabolique du glucose, nos rĂ©sultats rĂ©vĂšlent que les supercomplexes sont dynamiques et que leur composition en protĂ©ines dĂ©pend des stimulis et de la rĂ©gulation cellulaire. De plus, nous montrons que lâinactivation de la voie de biosynthĂšse des lipides de type II (FASII) perturbe lâassemblage et/ou la biogenĂšse du supercomplexe de la RNase P (responsable de la maturation en 5â des prĂ©curseurs des ARNt), ce qui suggĂšre que de multiples effets plĂ©iotropiques peuvent ĂȘtre de nature structurale entre les protĂ©ines.
Chez la levure et chez E. coli, nos Ă©tudes de la maturation in vitro des prĂ©curseurs des ARNt et de la protĂ©omique rĂ©vĂšlent lâassociation de la RNase P avec les enzymes de la maturation dâARNt en 3â. En effet, la voie de maturation des prĂ©-ARNt et des ARNr, et la dĂ©gradation des ARN mitochondriaux semblent ĂȘtres associĂ©es avec la machinerie de la traduction au sein dâun mĂȘme supercomplexe multifonctionnel dans la mitochondrie de la levure. Chez E. coli, nous avons caractĂ©risĂ© un supercomplexe similaire qui inclut en plus de la RNase P: la PNPase, le complexe du RNA degradosome, lâARN polymĂ©rase, quatre facteurs de transcription, neuf aminoacyl-tRNA synthĂ©tases, onze protĂ©ines ribosomiques, des chaperons et certaines protĂ©ines mĂ©taboliques. Ces rĂ©sultats supposent lâassociation physique de la transcription, la voie de maturation et dâaminoacylation des ARNt, la dĂ©gradation des ARN.
Le nombre de cas oĂč les activitĂ©s cellulaires sont fonctionnellement et structurellement associĂ©es est certainement Ă la hausse (ex, lâĂ©ditosome et le complexe de la glycolyse). En effet, lâorganisation en supercomplexe multifonctionnel reprĂ©sente probablement lâunitĂ© fonctionnelle dans les cellules et les analyses de ces super-structures peuvent devenir la prochaine cible de la biologie structurale.It is known that processes such as transcription, translation and intron splicing require a multitude of proteins (plus a few non-protein components) organized in large âmolecular machinesâ. But, according to traditional views, processing of RNA precursors (e.g., tRNA and rRNA) and metabolic pathways are pools of individual enzymes (single proteins or small complexes), with sequential enzymatic reaction steps connected via diffusible metabolites. This perception is incompatible with the âmolecular crowdingâ in most cellular compartments (e.g., 60% in the mitochondrial matrix). It is also not in line with the cumulating indirect evidence from comprehensive studies of protein-protein interactions and affinity purification, showing that numerous protein complexes involving different metabolic and regulatory processes are interconnected. However, direct evidence of extensive cross-talk among diverse cellular processes remains to be clearly demonstrated.
Here we show that in mitochondria of yeast and other fungi (Neurospora crassa and Rhizopus oryzae), animal (Bos taurus), plant (Brassica oleracea), and in E. coli (standing for the âbacterial ancestorâ of mitochondria), metabolism is physically interlinked (in supercomplexes) with translation, replication, transcription and RNA processing. Further, the supercomplexes also contain a variety of helper proteins, in support of earlier reports that describe such proteins as important structural units assisting complex assembly. Whereas the composition of supercomplexes in fungi (e.g., Neurospora crassa), animals and yeast is relatively similar, plants and E. coli present substantial compositional differences (e.g., plant-specific enzymes involved in the biosynthesis of sugars and secondary metabolites).
In yeast, the supercomplex pattern of glucose-repressed cells is completely different from that of cells grown on galactose/glycerol, and the protein composition perfectly correlates with known regulatory changes under glucose repression. The destabilization of the complex organization is also illustrated by the deletion of genes in the mitochondrial fatty acid type II biosynthetic pathway (mutant strain oar1Î). Mutants have both, a defect
in fatty acid synthesis and in 5â processing of mitochondrial tRNA, and no longer have a supercomplex containing Oar1p and components of RNase P (5â tRNA processing). The pleiotropic mutant phenotype is best explained by a structural (assembly) defect.
Also in yeast mitochondria, we demonstrate that RNase P and tRNA Z activities are part of a large complex, which further includes the RNA degradosome complex, five additional RNA processing proteins, and several other mitochondrial pathways. 5â and 3â tRNA processing enzymes are also associated in a large, multifunctional supercomplex in E. coli that includes six out of the seven proteins of the RNA degradosome, nine aminoacyl-tRNA synthases, RNA polymerase plus four transcription factors, eleven ribosomal proteins plus four translation factors, several components of protein folding and maturation, and a small set of metabolic enzymes. Apparently, not only is RNA processing coordinated, but it is also structurally connected to aminoacylation, transcription and other cellular functions.
The number of documented cases where functionally related activities are structurally integrated is definitely increasing (e.g., editosome, glycolysis complex, etc). Indeed, structural integration of related functions and pathways may turn out to be a principle and the analyses of such super-structures may become a next structural biology frontier
Dynamical Gaussian quantum steering in optomechanics
Einstein-Podolski-Rosen steering is a form of quantum correlation exhibiting
an intrinsic asymmetry between two entangled systems. In this paper, we propose
a scheme for examining dynamical Gaussian quantum steering of two mixed
mechanical modes. For this, we use two spatially separated optomechanical
cavities fed by squeezed light. We work in the resolved sideband regime.
Limiting to the adiabatic regime, we show that it is possible to generate
dynamical Gaussian steering via a quantum fluctuations transfer from squeezed
light to the mechanical modes. By an appropriate choice of the environmental
parameters, one-way steering can be observed in different scenarios. Finally,
comparing with entanglement - quantified by the Gaussian R\'enyi-2 entropy-, we
show that Gaussian steering is strongly sensitive to the thermal effects and
always upper bounded by entanglement degree
Gene editing tools new insights for public health and industrial applications
The ability to engineer biological systems and organisms holds enormous potential for applications across biotechnology, medicine, and basic science. Programmable sequence-specific endonucleases that facilitate precise editing of endogenous genomic loci are now enabling systematic interrogation of genetic elements and causal genetic variation. Here we discuss how gene editing by CRISPR/Cas9 new technology can be used in disease therapeutics, virology, cancer therapy, and biotechnology.
Magnetism of Two Coupled Harmonic Oscillators
The thermodynamical properties of a system of two coupled harmonic
oscillators in the presence of an uniform magnetic field B are investigated.
Using an unitary transformation, we show that the system can be diagonalized in
simple way and then obtain the energy spectrum solutions. These will be used to
determine the thermodynamical potential in terms of different physical
parameters like the coupling parameter \alpha. This allows us to give a
generalization of already significant published work and obtain different
results, those could be used to discuss the magnetism of the system. Different
limiting cases, in terms of \alpha and B, have been discussed. In fact, quantum
corrections to the Landau diamagnetism and orbital paramagnetism are found.Comment: 25 page
Unleashing Natureâs potential: a computational approach to discovering novel VEGFR-2 inhibitors from African natural compound using virtual screening, ADMET analysis, molecular dynamics, and MMPBSA calculations
One of the characteristic features of cancer is angiogenesis, the process by which new, aberrant blood vessels are formed from pre-existing blood vessels. The process of angiogenesis begins when VEGF binds to its receptor, the VEGF receptor (VEGFR). The formation of new blood vessels provides nutrients that can promote the growth of cancer cells. When it comes to new blood vessel formation, VEGFR2 is a critical player. Therefore, inhibiting VEGFR2 is an effective way to target angiogenesis in cancer treatment. The aim of our research was to find new VEGFR-2 inhibitors by performing a virtual screening of 13313 from African natural compounds using different in silico techniques. Using molecular docking calculations and ADMET properties, we identified four compounds that exhibited a binding affinity ranging from â11.0Â kcal/mol to â11.5Â Kcal/mol when bound to VEGFR-2. These four compounds were further analyzed with 100 ns simulations to determine their stability and binding energy using the MM-PBSA method. After comparing the compounds with Regorafenib, a drug approved for anti-angiogenesis treatment, it was found that all the candidates (EANPDB 252, NANPDB 4577, and NANPDB 4580), with the exception of EANPDB 76, could target VEGFR-2 similarly effectively to Regorafenib. Therefore, we recommend three of these agents for anti-angiogenesis treatment because they are likely to deactivate VEGFR-2 and thus inhibit angiogenesis. However, it should be noted that the safety and suitability of these agents for clinical use needs further investigation, as the computer-assisted study did not include in vitro or in vivo experiments
Effect of age, clone heads, ramet position and IBA treatment on the rooting of Argan tree (Argania spinosa L. Skeels) cuttings
The vegetative propagation of the Argan tree by cuttings was carried out in a glazed enclosure whose relative humidity and average temperature were 80% and 25 °C respectively. The first trial involved herbaceous cuttings taken from clone heads selected on the basis of productivity, vigor and ability to produce cuttings at different levels (heights) of the tree. Three factors were taken into account: the age of the root-stock, the branch position on the tree and the treatment with indol-butyric acid (IBA), a rooting hormone whose concentrations were 1000 and 2000 ppm compared to a control treated with distilled water. A second trial was conducted to control the overall conditions for cuttings rooting such as light, relative air humidity and substrate temperature, as well as the type of the cuttings: herbaceous, semi-woody and woody. The overall rooting rate was improved by four folds between de first and the second trial. It increased from 25% under uncontrolled conditions to 100% under controlled conditions in some clones. Young trees showed the greatest ability to root. Variance analysis showed a highly significant effect of clone head and branch position on rooting, dry weight and average length of cuttings. On the other hand, no significant effect was observed for auxin treatment on these variables. The best result (100% rooting) was obtained for apical and median cuttings of sprouts of young trees under controlled conditions. Tree age has a highly significant effect on root quality since cuttings from young trees showed superior dry weight and root length. The comparative study of the root system produced by cuttings with that of seedlings showed that seedlings are characterized by a well-developed taproot while cuttings develop a cluster of cells that give rise to several orthotropic roots