Static Characterization of the Birefringence Effect in the Semiconductor Optical Amplifier Using the Finite Difference Method

Knowing the various physical mechanisms of the semiconductor optical amplifier (SOA) helps us to develop a more complete numerical model. It also enables us to simulate more realistically the static behavior of the SOAs’ birefringence effect. This way, it allows us to study more precisely the behavior of SOAs, and particularly the impact of the amplified spontaneous emission (ASE) or the pump and probe signals as well as the optical functions based on the non-linearity of the component. In static regime, the SOAs possess a very low amplification threshold and a saturation power of the gain which mainly depends on the optical power injected into the active region. Beyond the optical input power, the SOA is in the saturated gain regime which gives it a nonlinear transmission behavior. Our detailed numerical model offers a set of equations and an algorithm that predict their behavior. The equations form a theoretical base from which we have coded our model in several files.cpp that the Language C++ executes. It has enabled us, from the physical and geometrical parameters of the component, to recover all the relevant values ​​for a comprehensive study of SOAs in static and dynamic regimes. In this paper, we propose to make a static characterization of the effect of the nonlinear polarization rotation by realizing a pump-probe assemblage to control the power and state of polarization at the entering of the SOA

DNA damage-induced S and G2/M cell cycle arrest requires mTORC2-dependent regulation of Chk1.

mTOR signalling is commonly dysregulated in cancer. Concordantly, mTOR inhibitors have demonstrated efficacy in a subset of tumors and are in clinical trials as combination therapies. Although mTOR is associated with promoting cell survival after DNA damage, the exact mechanisms are not well understood. Moreover, since mTOR exists as two complexes, mTORC1 and mTORC2, the role of mTORC2 in cancer and in the DNA damage response is less well explored. Here, we report that mTOR protein levels and kinase activity are transiently increased by DNA damage in an ATM and ATR-dependent manner. We show that inactivation of mTOR with siRNA or pharmacological inhibition of mTORC1/2 kinase prevents etoposide-induced S and G2/M cell cycle arrest. Further results show that Chk1, a key regulator of the cell cycle arrest, is important for this since ablation of mTOR prevents DNA damage-induced Chk1 phosphorylation and decreases Chk1 protein production. Furthermore, mTORC2 was essential and mTORC1 dispensable, for this role. Importantly, we show that mTORC1/2 inhibition sensitizes breast cancer cells to chemotherapy. Taken together, these results suggest that breast cancer cells may rely on mTORC2-Chk1 pathway for survival and provide evidence that mTOR kinase inhibitors may overcome resistance to DNA-damage based therapies in breast cancer

Dynamic Response of Two-Electrode Distributed Feedback Laser for Stable Signal Mode Operation

The longitudinal spatial hole burning (LSHB) effect has been known to limit the performance of distributed feedback (DFB) semiconductor lasers to achieve a better dynamic signal mode operation (DSMO). So, in order to ensure a stable (DSMO), we propose a novel device design of two electrode DFB lasers with longitudinal variation in the coupling coefficient (distributed coupling coefficient (DCC)), the structure also contains a phase shifted in middle of the cavity. By means of the finite difference time domain (FDTD) numerical method, we analyze dynamic response of our structure and we also compare the results with the conventional two electrode DFB laser (TE-DFB). The numerical simulation shows that, a better dynamic signal mode has been achieved by TE-DCC-DFB lasers in comparison with TE-DFB laser due to its better and high side mode suppression ratio (SMSR). Therefore, the TE-DCC-DFB lasers will be useful to extend the transmission distance in optical fiber communication systems

Petri Nets Models for Analysis and Control of Public Bicycle-Sharing Systems

International audienc

A New and simple pathway route way for the synthesis of silver nanoparticles using the industrial latex

This paper presents a new method for preparing silver nanofluids based onself assembly process induced by the aqueous emulsion of copolymers (Latex) on Silver nitrate precursor dissolved in alcohol. We have observed after few hours, that nanoparticles of silver are formed in the alcohol/latex solution without need of any external thermal excitation. These results are compared with the case where the synthesis was assisted by microwave providing thermal excitation.The latex polymers act as reducer inducing Ag+ →Ag° reaction in the colloidal solution and also as the protecting agent of the formed Ag nanoparticles encapsulated in the latex matrix. The obtained solutions have been characterized by The UV-Visible, XRD, TEM, and SEM. The UV- Visible spectrum shows a single peak at 425 nm arising from the surface plasmon absorption of silver nanoparticles. The TEM results showed that the spherical particles had an average diameter of 7 nm. The synthesized samples prepared Ag NPs were stable for more than 12 months at room temperature

Performance analysis of a small capacity horizontal axis wind turbine using QBlade

In recent times, wind energy has become one of the leading renewable energy sources for generating electricity in prospective regions around the globe. Nowadays, researchers are conducting different research activities to develop and optimize the existing designs of wind turbines through experimental and diversified computational techniques. Among the computational techniques, one of the popular choices is Computational Fluid Dynamics (CFD). However, CFD techniques are hardware intensive and computationally expensive. On the other hand, freely available simple tools like QBlade is computationally inexpensive and it can be used for performance and design analyses of horizontal and vertical axis wind turbines. In the present research, an attempt has been made to use QBlade for performance analyses of a smaller capacity horizontal axis wind turbine using selected prospective airfoils. In this study, four airfoils (namely, NACA 4412, SG6043, SD7062 and S833) have been selected and investigated in QBlade. It has been found that the overall power coefficients (CP) of NACA 4412 at different tip speed ratios are superior to the other three airfoils

Chemotherapy-mediated p53-dependent DNA damage response in clear cell renal cell carcinoma: role of the mTORC1/2 and hypoxia-inducible factor pathways.

The DNA-damaging agent camptothecin (CPT) and its analogs demonstrate clinical utility for the treatment of advanced solid tumors, and CPT-based nanopharmaceuticals are currently in clinical trials for advanced kidney cancer; however, little is known regarding the effects of CPT on hypoxia-inducible factor-2α (HIF-2α) accumulation and activity in clear cell renal cell carcinoma (ccRCC). Here we assessed the effects of CPT on the HIF/p53 pathway. CPT demonstrated striking inhibition of both HIF-1α and HIF-2α accumulation in von Hippel-Lindau (VHL)-defective ccRCC cells, but surprisingly failed to inhibit protein levels of HIF-2α-dependent target genes (VEGF, PAI-1, ET-1, cyclin D1). Instead, CPT induced DNA damage-dependent apoptosis that was augmented in the presence of pVHL. Further analysis revealed CPT regulated endothelin-1 (ET-1) in a p53-dependent manner: CPT increased ET-1 mRNA abundance in VHL-defective ccRCC cell lines that was significantly augmented in their VHL-expressing counterparts that displayed increased phosphorylation and accumulation of p53; p53 siRNA suppressed CPT-induced increase in ET-1 mRNA, as did an inhibitor of ataxia telangiectasia mutated (ATM) signaling, suggesting a role for ATM-dependent phosphorylation of p53 in the induction of ET-1. Finally, we demonstrate that p53 phosphorylation and accumulation is partially dependent on mTOR activity in ccRCC. Consistent with this result, pharmacological inhibition of mTORC1/2 kinase inhibited CPT-mediated ET-1 upregulation, and p53-dependent responses in ccRCC. Collectively, these data provide mechanistic insight into the action of CPT in ccRCC, identify ET-1 as a p53-regulated gene and demonstrate a requirement of mTOR for p53-mediated responses in this tumor type

A p53-independent role for the MDM2 antagonist Nutlin-3 in DNA damage response initiation.

BACKGROUND: The mammalian DNA-damage response (DDR) has evolved to protect genome stability and maximize cell survival following DNA-damage. One of the key regulators of the DDR is p53, itself tightly regulated by MDM2. Following double-strand DNA breaks (DSBs), mediators including ATM are recruited to the site of DNA-damage. Subsequent phosphorylation of p53 by ATM and ATM-induced CHK2 results in p53 stabilization, ultimately intensifying transcription of p53-responsive genes involved in DNA repair, cell-cycle checkpoint control and apoptosis. METHODS: In the current study, we investigated the stabilization and activation of p53 and associated DDR proteins in response to treatment of human colorectal cancer cells (HCT116p53+/+) with the MDM2 antagonist, Nutlin-3. RESULTS: Using immunoblotting, Nutlin-3 was observed to stabilize p53, and activate p53 target proteins. Unexpectedly, Nutlin-3 also mediated phosphorylation of p53 at key DNA-damage-specific serine residues (Ser15, 20 and 37). Furthermore, Nutlin-3 induced activation of CHK2 and ATM - proteins required for DNA-damage-dependent phosphorylation and activation of p53, and the phosphorylation of BRCA1 and H2AX - proteins known to be activated specifically in response to DNA damage. Indeed, using immunofluorescent labeling, Nutlin-3 was seen to induce formation of γH2AX foci, an early hallmark of the DDR. Moreover, Nutlin-3 induced phosphorylation of key DDR proteins, initiated cell cycle arrest and led to formation of γH2AX foci in cells lacking p53, whilst γH2AX foci were also noted in MDM2-deficient cells. CONCLUSION: To our knowledge, this is the first solid evidence showing a secondary role for Nutlin-3 as a DDR triggering agent, independent of p53 status, and unrelated to its role as an MDM2 antagonist

Assessment of fatty acids profile, oil yield and tocopherol content of four Almond cultivars grown in Eastern Morocco

The most cultivated varieties of almond in eastern Morocco: (Beldi (B), a local ecotype, Marcona (M) from Spain, Ferragnes-Ferraduel (F-F) and Fournat de Breznaud (FNB) from France), were studied during three consecutive crop years in order to evaluate variations in kernel oil yield, Fatty acid (FA) profile and physicochemical properties. For this purpose, extraction of almond oils was carried out by mechanical press. The yield of varieties B, M, (F-F) and FNB ranged between 50.68%- 54.33%, 41.46%- 52.59%, 47.70%-52.39% and 51.66%-56.10%, respectively. Oleic, linoleic and palmitic acids are the major fatty acids (FA) ranging between 57.54%- 72.90%, 17.80%- 29.81% and 6.50%-8.48%, respectively. Results showed a noticeable effect (P<0.001) of variety on Total phenolic content (TPC), oxidative stability and α-, β-, γ-, δ-tocopherol isomers; however, acidity and peroxide index, were affected with a lower manner by "variety" factor. In addition, all the analyzed parameters were highly (P<0.001) affected by climatic conditions of the crop year. In addition, the highest variations for the analyzed almond oils were recorded for their contents on α-tocopherol, γ-tocopherol, oleic and linoleic acids. According to the observed results, the couple Ferragnes-Ferraduel seems to produce stable and high quality almond oil compared to the other varieties

Chemical Composition, Antioxidant and Antibacterial Activities of Thymus broussonetii Boiss and Thymus capitatus (L.) Hoffmann and Link Essential Oils

Thymus capitatus and Thymus broussonnetii are two Moroccan endemic medicinal plants used traditionally by the local population. The present study aims to investigate their essential oil chemical composition, antioxidant and antibacterial activities. The chemical composition of the essential oils was determined using the GC-MS analysis, the antioxidant activity assessed using DPPH and FRAP methods while the antimicrobial activity was evaluated against nine bacteria species tested (Enterococcus faecalis, Serratia fonticola, Acinetobacter baumannii, Klebsiella oxytoca, sensitive Klebsiella pneumoniae, sensitive Escherichia coli, resistant Escherichia coli, resistant Staphylococcus aureus and Enterobacter aerogenes). The major identified compounds of T. capitatus essential oil where carvacrol (75%) and p-cymene (10.58%) while carvacrol (60.79%), thymol (12.9%), p-cymene (6.21%) and γ-terpinene (4.47%) are the main compounds in T. broussonnetii essential oil. The bioactivity of the essential oils of the two species of thyme was explained by their richness in oxygenated monoterpenes known for their great effectiveness with an IC50 of 3.48 ± 0.05 and 4.88 ± 0.04 μL/mL and EC50 of 0.12 ± 0.01 and 0.20 ± 0.02 μL/mL in the DPPH and FRAP assays, respectively, with an important antibacterial activity. These results encourage the use of these plants as a source of natural antioxidants, and antibacterial additives, to protect food from oxidative damage and to eliminate bacteria that are responsible for nosocomial infections