Photonic processing of microwave signals

La distribution par fibre optique de signaux de type « ultra-wideband (UWB)» requiert le développement de nouvelles technologies photoniques qui seront le sujet d'étude de cette thèse. Nous commençons avec un démonstration expérimentale d'une technique de sculpture d'impulsions qui offre une solution économique et à faible consommation de puissance pour les systèmes UWB . Dans cette étude, nous procédons à l'apodisation de deux réseaux Bragg identiques avec une variation de période linéaire qui sont placés aux deux entrées d'un photodétecteur balancé. L'apodisation est réalisée par l'application d'un profile de température à l'aide d'éléments résistif de petite dimensions, ce qui permet une consommation énergétique réduite et une bonne résolution spectrale. Le filtrage spectral d'une source laser puisée suivi d'une conversion fréquence-temps par propagation dans une fibre optique standard permet de générer une impulsion UWB efficace d'un point de vue énergétique pour les communications à courte portée dans la bande spectrale de 3 a 10 GHz. Dans un deuxième temps, pour générer des signaux passe-bande à haute fréquence, nous avons utilisé un laser puisé à commutation de gain. Après la conversion optique/électrique des impulsions en utilisant des filtres optiques et RF appropriés, nous réussissons à générer des signaux large bande dans des bandes spectrales ayant des fréquences centrales de 25, 35 et 45 GHz. Nous examinons diverses configurations de filtres permettant cette conversion selon qu'il y ait ou non transmission dans une fibre optique. Finalement, nous démontrons la détection de signaux RF dans le domaine optique par le design et la fabrication de filtres adaptés. Notre récepteur utilise un modulateur de Mach-Zehnder pour faire la conversion électrique-optique et des filtres à base de réseau de Bragg comme filtres adaptés. Nous examinons la performance du récepteur pour deux conditions de polarisation différentes du Mach-Zehnder. Nous avons conçu des filtres adaptés pour ces deux cas et nous discutons de la performance résultant

Multiwavelength erbium-ytterbium co-doped fiber laser / by Mansour Dastmalchi.

A fiber ring laser, using erbium-ytterbium co-doped double clad fiber is proposed and demonstrated to produce a medium power multiwavelength fiber laser. The experimental results show that the ring resonator configuration can produce more output power compared to a laser based on bidirectional pumping scheme in Fabry-Perot resonator configuration. To stabilize the lasing lines we used an unpumped erbium doped fiber as saturable absorber. A sagnac loop interferometer is used as a filter inside the cavity and its effect has been explored. We can produce a maximum four lasing lines which are stable for more than 2 hours when observed through OSA with a resolution of 0.05 run. The maximum output power obtained from the laser is more than 100 mW. Our best result at room temperature is simultaneous oscillations of two single-mode laser wavelengths with a maximum output power of 60 mW when observed through a scanning Fabry-Perot spectrum analyzer of resolution 27 MHz

Retraction Note: The effects of valsartan on renal glutathione peroxidase expression in alleviation of cyclosporine nephrotoxicity in rats

This paper1 was simultaneously submitted by the authors to "Transplantation" journal under the title "The Effects of Valsartan on Renal Klotho Expression and Oxidative stress in Alleviation of Cyclosporine Nephrotoxicity" and was accepted for publication in that journal. On the basis of BioImpacts policy in accordance with the Committee on Publication Ethics (COPE), any duplicate submission is considered as an ethical misconduct. The accepted manuscript in Transplantation shared considerable overlapping text and data (identical images and materials) with the published paper1 in BioImpacts. The Editor-in-Chief of BioImpacts, Prof. Y. Omidi, was alerted by the Editor-in-Chief of Transplantation, Prof. Jeremy R. Chapman, on such duplication. A comprehensive investigation through comparison of both papers was conducted by the editorial office of BioImpacts along with the Ethics Committee of Tabriz University of Medical Sciences (TUOMS) under Prof. M. R. Rashidi, who also acts as Director-in-Charge of BioImpacts and TUOMS Vice Chancellor of Research and Technology Affairs. As a result, they decided to retract this paper in line with the COPE recommendations. The authors were informed and advised on this serious ethical breach. Therefore, the paper is retracted at the request of authors, the aforementioned committee and the Editor-in-Chief of BioImpacts, even though the corresponding author believed that two papers were different in their aims, studied animals, and factors. By the way, they apologize for any inconvenience this may have caused. One of the conditions of submission of a paper to BioImpacts is that authors declare explicitly that "This manuscript has been exclusively submitted to this journal and is not under review or accepted for publication elsewhere". As such, this paper represents abuse of the scientific publishing system. As a peer-review multidisciplinary international "Publish Free" and "Access Free" journal, BioImpacts strongly adheres to the "Publication Ethics", and its foremost goal is to preserve the integrity of the scientific reports in the highest standards, therefore the journal takes all issues of publication misconduct seriously

The effects of valsartan on renal glutathione peroxidase expression in alleviation of cyclosporine nephrotoxicity in rats

Introduction: Nephrotoxicity as a side effect caused by the immunosuppressive drug, cyclosporine-A (CsA), can be a major problem in transplant medicine. Oxidative stress may play an important role in the CsA-induced nephrotoxicity. It has been shown that the antihypertensive drug, valsartan (Val), has also renoprotective effects but, its molecular mechanism is largely unknown. In the present study, it was aimed to evaluate the Val effect in the alleviation of CsA nephrotoxicity via probable renal glutathione peroxidase (GPx) upregulation and oxidative stress decrease. Methods: Thirty-two Sprague-Dawley rats were divided into four groups based on CsA and/or Val administration: group A (Control, 1 mL/kg/day of olive oil as vehicle), group B (CsA, 30 mg/kg/day), group C (CsA+Val, 30+30 mg/kg/day), and group D (Val, 30 mg/kg/day). After the administration period (six weeks), renal GPx expression was evaluated by real-time polymerase chain reaction (PCR). Plasma levels of GPx and 8-Hydroxydeoxyguanosine (8-OHdG) were measured by enzyme-linked immunosorbent assay (ELISA). Malondialdehyde (MDA) and protein carbonyl groups (PCG) were measured by spectrophotometer. Plasma levels of urea and creatinine were measured by an autoanalyzer. Results: CsA treatment led to the decrease in renal expression and plasma levels of GPx in comparison to other study groups. Rats received CsA were detected to have significantly (p<0.05) higher plasma 8-OHdG, MDA, PCG, urea, and creatinine levels in comparison to other groups. Plasma urea and creatinine levels were negatively correlated with renal GPx expression and positively correlated with the oxidative stress markers. Conclusion: Administration of Val may result in attenuating the nephrotoxic side effect of CsA via probable renal GPx upregulation, and subsequently oxidative stress decrease