1,358 research outputs found
Next Generation 10 Gb/s RZ Optical Transmitters
No full textA Master of Science thesis in Mechatronics Submitted to the School of Engineering by Amira Mohamed Al Houli, "Next Generation 10 Gb/s RZ Optical Transmitters," May 6th, 2004. Chair of Thesis Committee Dr. Aly Elrefaie. Available are Both Soft and Hard Copies of the Thesis.We propose an alternate chirp RZ optical transmitter that provides telecommunication carriers with a cost effective solution for upgrading the existing 2.5 Gb/s fiber links to 10 Gb/s. The performance of the proposed alternate chirp RZ transmitter has been compared with the chirp-free RZ with 33% duty cycle, chirp-free RZ with 50% duty cycle, and NRZ transmitters. Two dispersion compensation schemes have been used in the evaluation. In the first scheme, the fiber dispersion is compensated at the transmitter and receiver sites (end-to-end compensation) for 1000 km and 2000 km links. In the second scheme, the fiber dispersion is compensated every 640 km where optical switches are normally located. Computer simulation results indicate that RZ transmitters are better than NRZ transmitter for both dispersion compensation schemes. They also indicate that alternate chirp RZ transmitter can tolerate nonlinear effects than other classical chirp-free RZ transmitters for transmission up to 2000 km using end-to-end compensation scheme. Transmission up to 4000 km using dispersion compensation every 640 km is also possible using alternate chirp RZ transmitter but not possible with chirp-free RZ transmitters nor NRZ transmitter.College of EngineeringMultidisciplinary ProgramsMaster of Science in Mechatronics Engineering (MSMTR
Generation and characterisation of 40 GHz picosecond optical pulses generated using an EAM
No full textThe authors describe the generation of short (< 4 ps) optical pulses at a repetition rate of 40 GHz using an InP electro-absorption modulator. The technique of frequency resolved optical gating (FROG) is subsequently used to accurately characterize the generated pulses over a range of bias conditions and RF drive voltages. Our results show that the FROG technique will be vital for the optimization of RZ optical transmitters (in terms of pulse width, extinction ratio and frequency chirp) to be used in systems operating at 40 Gb/s and beyond, as standard measurement techniques will not suffice to optimize such high-speed hybrid WDM/OTDM or OTDM systems
Simvastatin prevents isoproterenol-induced cardiac hypertrophy through modulation of the JAK/STAT pathway
No full textNouf M Al-Rasheed,1 Maha M Al-Oteibi,1 Reem Z Al-Manee,1 Sarah A Al-Shareef,1 Nawal M Al-Rasheed,1 Iman H Hasan,1 Raeesa A Mohamad,2 Ayman M Mahmoud3 1Department of Pharmacology, Faculty of Pharmacy, 2Department of Anatomy, College of Medicine, King Saud University, Riyadh, Saudi Arabia; 3Physiology Division, Department of Zoology, Faculty of Science, Beni-Suef University, Egypt Abstract: Simvastatin (SIM) is a lipid-soluble inhibitor of hydroxy-3-methylglutaryl coenzyme A reductase with multiple reported therapeutic benefits. The present study was designed to investigate the effect of pretreatment with SIM on isoproterenol (ISO)-induced cardiac hypertrophy in rats. Twenty-four male albino Wistar rats weighing 180–200 g were divided into four groups. Groups I and III received normal saline while groups II and IV received SIM (10 mg/kg body weight) for 30 days per gavage. In the last 7 days, rats of groups III and IV were administered ISO (5 mg/kg) intraperitoneally to induce cardiac hypertrophy. Administration of ISO induced an increase in heart-to-body weight (HW/BW) ratio, an increase in serum interleukin-6, and elevated systolic and diastolic blood pressure. Serum levels of lipids, cardiovascular risk indices, and cardiac troponin I and creatine phosphokinase-MB showed significant increase in ISO-induced hypertrophic rats. Histopathological examination of heart tissue revealed focal areas of subendocardium degeneration, mononuclear cellular infiltrations, fibrous tissue deposition, and increased thickness of the myocardium of left ventricle. In addition, ISO-administered rats exhibited significant upregulation of cardiac Janus kinase, phosphorylated signal transducer and activator of transcription, and nuclear factor-kappa B. Pretreatment with SIM significantly prevented ISO-induced cardiac hypertrophy, alleviated the altered biochemical parameters, and improved the heart architecture. In conclusion, our study provides evidence that SIM prevented the development of cardiac hypertrophy via modulation of the Janus kinase/signal transducer and activator of transcription-signaling pathway in the heart of ISO-administered animals. Keywords: simvastatin, cardiac hypertrophy, JAK/STAT pathway, IL-6, isoprotereno
Ortografia bez reguł i wyjątków. Na przykładzie pisowni „rz” i „ż”
No full textSpelling without rules and exceptions as exemplified by the spelling of “rz” and “ż”Spelling rules in Polish maintain that there are “rz” and “ż” that are not interchangeable, which the author of the article rejects, proving that for nearly all words with uninterchangeable “rz” and “ż” there exist related words with interchangeable “r” or “z”, “g”, “s”, “h”. The author also rejects the rule requiring “rz” when following consonants “p”, “b”, “t”, “d”, “w”, “g”, “ch”, “j” as well as the conviction of the existence of numerous exceptions from the accepted rules. The author accepts only one rule, i.e. the rule of interchangeability and rejects mechanical memorising of spelling in exchange for cognitive learning, reinforced by the knowledge of the history of language and historical grammar.Spelling without rules and exceptions as exemplified by the spelling of “rz” and “ż”Spelling rules in Polish maintain that there are “rz” and “ż” that are not interchangeable, which the author of the article rejects, proving that for nearly all words with uninterchangeable “rz” and “ż” there exist related words with interchangeable “r” or “z”, “g”, “s”, “h”. The author also rejects the rule requiring “rz” when following consonants “p”, “b”, “t”, “d”, “w”, “g”, “ch”, “j” as well as the conviction of the existence of numerous exceptions from the accepted rules. The author accepts only one rule, i.e. the rule of interchangeability and rejects mechanical memorising of spelling in exchange for cognitive learning, reinforced by the knowledge of the history of language and historical grammar
Optimisation and statistical analysis of 21.4 Gb/s RZ-DPSK WDM non-slope matched transmission
No full textConsidering a numerical example, we analyse the performance of Return-to-Zero (RZ) Differential Phase Shift Keyed (DPSK) transmission when deployed in a large scale transmission system. It is shown that at high distances, RZ-DPSK performs well whilst being limited by nonlinear effects. We also show that when nonlinear effects become dominant, we can still estimate channel statistics to reasonable accuracy
Wavelength tunable transmitters for future reconfigurable agile optical networks
No full textWavelength tuneable transmission is a requirement for future reconfigurable agile optical networks as it enables cost efficient bandwidth distribution and a greater degree of transparency. This thesis focuses on the development and characterisation of wavelength tuneable transmitters for the core, metro and access based WDM networks.
The wavelength tuneable RZ transmitter is a fundamental component for the core network as the RZ coding scheme is favoured over the conventional NRZ format as the line rate increases. The combination of a widely tuneable SG DBR laser and an EAM is a propitious technique employed to generate wavelength tuneable pulses at high repetition
rates (40 GHz). As the EAM is inherently wavelength dependant an accurate characterisation of the generated pulses is carried out using the linear spectrogram
measurement technique. Performance issues associated with the transmitter are investigated by employing the generated pulses in a 1500 km 42.7 Gb/s circulating loop
system. It is demonstrated that non-optimisation of the EAM drive conditions at each operating wavelength can lead to a 33 % degradation in system performance. To achieve
consistent operation over a wide waveband the drive conditions of the EAM must be altered at each operating wavelength.
The metro network spans relatively small distances in comparison to the core and therefore must utilise more cost efficient solutions to transmit data, while also
maintaining high reconfigurable functionality. Due to the shorter transmission distances, directly modulated sources can be utilised, as less precise wavelength and chirp control can be tolerated. Therefore a gain-switched FP laser provides an ideal source for wavelength tuneable pulse generation at high data rates (10 Gb/s). A self-seeding scheme that generates single mode pulses with high SMSR (> 30 dB) and small pulse duration is demonstrated. A FBG with a very large group delay disperses the generated pulses and subsequently uses this CW like signal to re-inject the laser diode negating the need to tune the repetition rate for optimum gain-switching operation.
The access network provides the last communication link between the customer’s premises and the first switching node in the network. FTTH systems should take advantage of directly modulated sources; therefore the direct modulation of a SG DBR tuneable laser is investigated. Although a directly modulated TL is ideal for reconfigurable access based networks, the modulation itself leads to a drift in operating frequency which may result in cross channel interference in a WDM network. This effect is investigated and also a possible solution to compensate the frequency drift through simultaneous modulation of the lasers phase section is examined
A comparison of 43-Gb/s POLMUX-RZ-DPSK and POLMUX-RZ-DQPSK modulation for long-haul transmission systems
No full textWe compare the suitability of 43-Gb/s POLMUX-RZ-DPSK and POLMUX-RZ-DQPSK modulation for long-haul optical transmission. We experimentally demonstrate that the higher robustness against nonlinear impairments of 43-Gb/s POLMUX-RZ-DPSK allows for a ~40% increase in feasible transmission distance
Corrélation entre le nombre de taches solaires (Rz) et les évènements de chocs au cours du cycle solaire 24
No full textThe correlation between Rz and shock events is investigated using the temporal profiles of Rz and Aa geomagnetic index. By evaluating the activity of shock events according to the classification of Legrand et Simon (1989) and Zerbo et al. (2012), the study revealed a very low correlation between shock events and Rz. A consideration of coronal mass ejections (CMEs) data isolated fourteen (14) cases of sudden storm commencement (SSC) that were not caused by CMEs. The elimination of these cases resulted in a good correlation between Rz and magnetic cloud activity and between Rz and shock events. The correlation coefficient between Rz and shock activity has changed but remains low. That between shock events is constant. These results, clearly below those of Zerbo et al. (2012) for cycles 11 to 23, could be explained by the low agitation of shock events during cycle 24.La corrélation entre Rz et les évènements de chocs est étudiée en utilisant les profils temporels de Rz et de l’indice géomagnétique Aa. En évaluant l'activité des évènements de chocs selon la classification de Legrand et Simon (1989) et Zerbo et al. (2012), l’étude a révélé une très faible corrélation entre les événements de chocs et Rz. Une prise en compte des données sur les éjections de masses coronales (CMEs) a permis d’isoler quatorze (14) cas de sudden storm commencement (SSC) qui ne sont pas provoqués par des CMEs. L’élimination de ces cas a permis d’obtenir une bonne corrélation entre Rz et l’activité de nuages magnétiques et entre Rz et les événements de chocs. Le coefficient de corrélation entre Rz et l’activité de chocs a évolué mais reste faible. Celui entre les évènements de chocs est resté constant. Ces résultats, nettement en deçà de ceux de Zerbo et al. (2012) pour les cycles 11 à 23 pourraient trouver une explication dans la faible agitation du point de vue d’événements de chocs au cours du cycle 24.
 
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RZ Piscium Hosts a Compact and Highly Perturbed Debris Disk
No full textRZ Piscium (RZ Psc) is well known in the variable star field because of its numerous irregular optical dips in the past 5 decades, but the nature of the system is heavily debated in the literature. We present multiyear infrared monitoring data from Spitzer and WISE to track the activities of the inner debris production, revealing stochastic infrared variability as short as weekly timescales that is consistent with destroying a 90 km sized asteroid every year. ALMA 1.3 mm data combined with spectral energy distribution modeling show that the disk is compact (∼0.1-13 au radially) and lacks cold gas. The disk is found to be highly inclined and has a significant vertical scale height. These observations confirm that RZ Psc hosts a close to edge-on, highly perturbed debris disk possibly due to migration of recently formed giant planets that might be triggered by the low-mass companion RZ Psc B if the planets formed well beyond the snowlines. © 2023. The Author(s). Published by the American Astronomical Society.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Conductometría con el localizador apical electrónico propex pixi y el localizador apical YS-RZ-A
No full textThe purpose of this research work was to compare the conductometrics with the Propex Pixi electronic apical locator and the YS-RZ-A apical locator. The type of research was quantitative, quasi-experimental design, comparative descriptive, cross-sectional. The sample consisted of 20 premolar teeth. The results that stood out the most were: The average of the measurements of the conductometrics with Propex Pixi was 17.68 mm. The mean of the conductometric measurements with YS-RZ-A was 17.50 mm. The most frequent conductometry with LAE Propex Pixi was 16.00 mm; followed by 19.50mm. The most frequent conductometry with LAE YS-RZ-A was 17.00 mm; 18.00mm and 19.00mm. The average measurement at the apical foramen with LAE Propex Pixi was 18.68 mm and at the anatomical foramen it was 19.10 mm. The average measurement at the apical foramen with LAE YS-RZ-A was 18.50 mm and at the anatomical foramen it was 19.10 mm. In none of the cases did the Electronic Apical Locators exceed the apical foramen. There is a significant difference between the measurement at the apical foramen with the LAE Propex Pixi and the anatomical apical foramen (p=0.000). There is a significant difference between the measurement at the apical foramen with the LAE YS-RZ-A and the anatomical apical foramen (p=0.000). There are no significant differences between the conductometrics obtained with LAE Propex Pixi and YS-RZ-A (p=0.763).La finalidad de este trabajo de investigación fue la comparación de la conductometría con el localizador apical electrónico Propex Pixi y el localizador apical YS-RZ-A. El tipo de investigación fue cuantitativa, el diseño cuasi-experimental, descriptivo comparativo, transversal. La muestra fue conformada por 20 dientes premolares. Los resultados destacados fueron: El promedio de las medidas de conductometría con Propex Pixi fue 17,68 mm. El promedio de las medidas de conductometría con YS-RZ-A fue 17,50 mm. La conductometría más frecuente con LAE Propex Pixi fue 16,00 mm; seguido de 19,50 mm. La conductometría más frecuente con LAE YS-RZ-A fue 17,00 mm; 18,00 mm y 19,00 mm. El promedio de medidas al foramen apical con LAE Propex Pixi fue 18,68 mm y al anatómico fue 19,10 mm. El promedio de medidas al foramen apical con LAE YS-RZ-A fue 18,50 mm y al anatómico fue 19,10 mm. En ninguno de los casos los Localizadores Apicales Electrónicos sobrepasaron el foramen apical. Existe diferencia significativa entre la medida al foramen apical con el LAE Propex Pixi y el foramen apical anatómico (p=0,000). Existe diferencia significativa entre la medida al foramen apical con el LAE YS-RZ-A y el foramen apical anatómico (p=0,000). No existe diferencias significativas entre las conductometrías obtenidas con LAE Propex Pixi y YS-RZ-A (p=0,763)
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