Implémentation et vérification de la méthode zonale à coefficients d'absorption multiples

Presentation available online at http://www.sft.asso.fr/Local/sft/dir/user-3775/documents/actes/congres_2011/Communications/167.pdfNational audienceLa méthode zonale à coefficients d'absorption multiples (MACZM) pour la modélisation des facteurs de transferts radiatifs dans les milieux transparents et semi-transparents est implémentée et validée numériquement. Les calculs sont améliorés par l'utilisation de réseaux de neurones artificiels. Une autre méthode efficace de calcul des facteurs de transferts radiatifs, la méthode des flux plans, est aussi décrite. Les deux méthodes sont appliquées simultanément pour le calcul des facteurs d'échanges radiatifs dans un four de réchauffage sidérurgique de brames d'acier et les résultats sont comparés. La validité deMACZM est ainsi démontrée et des temps de calcul réduits de plus de cent fois sont obtenus

Essential oils modulate gene expression and ochratoxin a production in Aspergillus carbonarius

Ochratoxin A (OTA) is a mycotoxin, mainly produced on grapes by Aspergillus carbonarius, that causes massive health problems for humans. This study aims to reduce the occurrence of OTA by using the ten following essential oils (E.Os): fennel, cardamom, anise, chamomile, celery, cinnamon, thyme, taramira, oregano and rosemary at 1 µL/mL and 5 µL/mL for each E.O. As a matter of fact, their effects on the OTA production and the growth of A. carbonarius S402 cultures were evaluated, after four days at 28 C on a Synthetic Grape Medium (SGM). Results showed that A. carbonarius growth was reduced up to 100%, when cultured with the E.Os of cinnamon, taramira, and oregano at both concentrations and the thyme at 5 µL/mL. As for the other six E.Os, their effect on A. carbonarius growth was insignificant, but highly important on the OTA production. Interestingly, the fennel E.O at 5 µL/mL reduced the OTA production up to 88.9% compared to the control, with only 13.8% of fungal growth reduction. We further investigated the effect of these E.Os on the expression levels of the genes responsible for the OTA biosynthesis (acOTApks and acOTAnrps along with the acpks gene) as well as the two regulatory genes laeA and vea, using the quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR) method. The results revealed that these six E.Os reduced the expression of the five studied genes, where the ackps was downregulated by 99.2% (the highest downregulation in this study) with 5 µL/mL of fennel E.O. As for the acOTApks, acOTAnrps, veA and laeA, their reduction levels ranged between 10% and 96% depending on the nature of the E.O and its concentration in the medium

Antifungal and Antiochratoxigenic Activities of Essential Oils and Total Phenolic Extracts: A Comparative Study

This study is intended to prevent ochratoxin A (OTA) production by Aspergillus carbonarius S402 using essential oils (EOs) and total phenolic compounds extracted from plants and herbs. The EOs used in this study are the following: bay leaves, cumin, fenugreek, melissa, mint, and sage. As for the phenolic compounds, they were extracted from bay leaves, cumin, fenugreek, melissa, mint, sage, anise, chamomile, fennel, rosemary, and thyme. The experiments were conducted on Synthetic Grape Medium (SGM) medium at 28 °C for 4 days. OTA was extracted from the medium with methanol and quantified using HPLC (High Performance Liquid Chromatography). Results showed that EOs had a greater impact than the total phenolic extracts on the OTA production. Reduction levels ranged between 25% (sage) and 80% (melissa) for the EOs at 5 µL mL-1, and 13% (thyme) and 69% (mint) for the phenolic extracts. Although they did not affect the growth of A. carbonarius, total phenolic extracts and EOs were capable of partially reducing OTA production. Reduction levels depended on the nature of the plants and the concentration of the EOs. Reducing OTA with natural extracts could be a solution to prevent OTA production without altering the fungal growth, thus preserving the natural microbial balance

Ability of Soil Isolated Actinobacterial Strains to Prevent, Bind and Biodegrade Ochratoxin A

Ochratoxin A (OTA) is one of the most important mycotoxins, and contaminates several agricultural products, particularly cereals, grapes, maize, barley, spices and coffee. The aim of this project was to reduce the levels of OTA by supplementing the artificially contaminated solutions with seven strains of actinobacteria (AT10, AT8, SN7, MS1, ML5, G10 and PT1) in order to evaluate their capacity for binding and metabolizing the OTA, as well as their ability to reduce the expression of the genes responsible for its production in A. carbonarius. In the first part of this study, we evaluated the capacity of Streptomyces strains for binding OTA on their surfaces after 0, 30 and 60 min of incubation with PBS solution supplemented with OTA. In the second part, we tested the ability of these strains, as well as their supernatants, to detoxify the ISP2 medium. Finally, we studied the effect of the Streptomyces cocultured with Aspergillus carbonarius on the expression of OTA biosynthesis genes. Results showed that, among the strains co-cultured with A. carbonarius, the strain G10 was able to reduce the expression of acpks, acOTApks, acOTAnrps and vea genes, thus reducing OTA from solid PDA medium to 13.50% of reduction. This strain was remarkably able to detoxify and bind OTA up to 47.07%. Strain AT8 was stronger in detoxifying OTA (52.61%), but had no significant effect on the studied gene expression

Valorization of wine‐making by‐products’ extracts in cosmetics

The increased demand for conscious, sustainable and beneficial products by the consumers has pushed researchers from both industries and universities worldwide to search for smart strategies capable of reducing the environmental footprint, especially the ones connected with industrial wastes. Among various by-products, generally considered as waste, those obtained by winemaking industries have attracted the attention of a wide variety of companies, other than the vineries. In particular, grape pomaces are considered of interest due to their high content in bioactive molecules, especially phenolic compounds. The latter can be recovered from grape pomace and used as active ingredients in easily marketable cosmetic products. Indeed, phenolic compounds are well known for their remarkable beneficial properties at the skin level, such as antioxidant, antiaging, anti-hyperpigmentation and photoprotective effects. The exploitation of the bioactives contained in grape pomaces to obtain high value cosmetics may support the growing of innovative start-ups and expand the value chain of grapes. This review aims to describe the strategies for recovery of polyphenols from grape pomace, to highlight the beneficial potential of these extracts, both in vitro and in vivo, and their potential utilization as active ingredients in cosmetic products

Human CD34+ CD133+ Hematopoietic Stem Cells Cultured with Growth Factors Including Angptl5 Efficiently Engraft Adult NOD-SCID Il2rγ−/− (NSG) Mice

Increasing demand for human hematopoietic stem cells (HSCs) in clinical and research applications necessitates expansion of HSCs in vitro. Before these cells can be used they must be carefully evaluated to assess their stem cell activity. Here, we expanded cord blood CD34+ CD133+ cells in a defined medium containing angiopoietin like 5 and insulin-like growth factor binding protein 2 and evaluated the cells for stem cell activity in NOD-SCID Il2rg−/− (NSG) mice by multi-lineage engraftment, long term reconstitution, limiting dilution and serial reconstitution. The phenotype of expanded cells was characterized by flow cytometry during the course of expansion and following engraftment in mice. We show that the SCID repopulating activity resides in the CD34+ CD133+ fraction of expanded cells and that CD34+ CD133+ cell number correlates with SCID repopulating activity before and after culture. The expanded cells mediate long-term hematopoiesis and serial reconstitution in NSG mice. Furthermore, they efficiently reconstitute not only neonate but also adult NSG recipients, generating human blood cell populations similar to those reported in mice reconstituted with uncultured human HSCs. These findings suggest an expansion of long term HSCs in our culture and show that expression of CD34 and CD133 serves as a marker for HSC activity in human cord blood cell cultures. The ability to expand human HSCs in vitro should facilitate clinical use of HSCs and large-scale construction of humanized mice from the same donor for research applications.Singapore-MIT Alliance for Research and Technology ( Infectious Diseases research grant

Products of diagonalizable matrices

Chapter 1 reviews better-known factorization theorems of a square matrix. For example, a square matrix over a field can be expressed as a product of two symmetric matrices; thus square matrices over real numbers can be factorized into two diagonalizable matrices. Factorizing matrices over complex numbers into Hermitian matrices is discussed. The chapter concludes with theorems that enable one to prescribe the eigenvalues of the factors of a square matrix, with some degree of freedom. Chapter 2 proves that a square matrix over arbitrary fields (with one exception) can be expressed as a product of two diagonalizable matrices. The next two chapters consider decomposition of singular matrices into Idempotent matrices, and of nonsingular matrices into Involutions. Chapter 5 studies factorization of a complex matrix into Positive-(semi)definite matrices, emphasizing the least number of such factors required.Mathematical SciencesM. Sc. (Mathematics

Metal organic vapor phase epitaxy of semipolar GaN on patterned silicon substrates

Jusqu'à présent, les dispositifs optoélectroniques commerciaux sont épitaxiés selon la direction c, qui souffre de deux limitations intrinsèques. D'une part, les fortes discontinuités de polarisation le long de l'hétéro-interfaces des nitrures qui sont responsables de l'effet Stark de confinement quantique. Ceci mène dans le cas des dispositifs optiques GaN à une séparation de la fonction d'onde électron-trou dans les puits quantiques. D'une autre part, l'incorporation d'indium sur les plans polaires (0001) se trouve être relativement limité par comparaison avec les autres orientations cristallographiques. Ces effets néfastes peuvent être partiellement dépasser en performant la croissance du GaN sur des plans cristallographiques autre que le plan (0001). Ces plans semi polaires conduit éventuellement à l'amélioration des performances du dispositif. En fait, comme la seule solution disponible pour l'instant pour la croissance du GaN semipolaire est l'homoépitaxie, les dispositifs à base de GaN semipolaire de haute qualité a ses inconvénients qui est la petite taille et le prix élevé des substrats. Cela justifie la croissance du GaN semi-polaire sur d'autre type de substrats spécialement le silicium. Dans cette étude, la croissance de couches de GaN semi-polaire (10-11) et (20-21) par MOVPE sur des substrats de silicium structurés sera évaluée. La stratégie générale de fabrication consiste a structuré l'orientation adaptée du substrat silicium de façon à révéler les facettes Si(111).To-date, commercial III-nitride optoelectronic devices are grown along the c-direction, which suffers two intrinsic limitations. The first is the strong polarization discontinuities across nitride hetero-interfaces that are responsible for the quantum confined Stark effect, leading in the case of GaN-based optical devices to electron-hole wave function separation within the quantum wells, and thus, a decrease in the oscillator strength. The associated longer exciton lifetime together with the occurrence of non-radiative defects, result in reducing the device's efficiency. The second is the indium incorporation on the polar plane, which is relatively limited when compared with its incorporation on other crystallographic orientations. These deleterious effects can be partially overcome by performing the growth of GaN on planes other than (0001), such as semipolar ones leading to the eventual improvement of devices' performances. Growth of device-quality semipolar GaN, however, comes at a price, and the only currently available option is homoepitaxy, which is limited in size and is highly priced. At this point, the growth on foreign substrates becomes appealing, especially on silicon. In this thesis, the MOVPE growth of (10-11) and (20-21) semipolar GaN on patterned silicon substrates has been performed. The general fabrication strategy, which consists of patterning the appropriate silicon wafer orientation in order to reveal the Si (111) facets, will be first described. Subsequently, the selective growth of GaN along the c-direction will be carried out, where the c-oriented crystals will be brought to coalescence until a semipolar layer is achieved