Volterra-assisted Optical Phase Conjugation: a Hybrid Optical-Digital Scheme For Fiber Nonlinearity Compensation

Mitigation of optical fiber nonlinearity is an active research field in the area of optical communications, due to the resulting marked improvement in transmission performance. Following the resurgence of optical coherent detection, digital nonlinearity compensation (NLC) schemes such as digital backpropagation (DBP) and Volterra equalization have received much attention. Alternatively, optical NLC, and specifically optical phase conjugation (OPC), has been proposed to relax the digital signal processing complexity. In this work, a novel hybrid optical-digital NLC scheme combining OPC and a Volterra equalizer is proposed, termed Volterra-Assisted OPC (VAO). It has a twofold advantage: it overcomes the OPC limitation in asymmetric links and substantially enhances the performance of Volterra equalizers. The proposed scheme is shown to outperform both OPC and Volterra equalization alone by up to 4.2 dB in a 1000 km EDFA-amplified fiber link. Moreover, VAO is also demonstrated to be very robust when applied to long-transmission distances, with a 2.5 dB gain over OPC-only systems at 3000 km. VAO combines the advantages of both optical and digital NLC offering a promising trade-off between performance and complexity for future high-speed optical communication systems

COMPARING THE SENSITIVITY AND SPECIFICITY OF CBCT AND MRI IN DETECTING OSTEOARTHRITIS OF THE TMJ: A SYSTEMATIC REVIEW

The aim of this systematic review was to compare the sensitivity and specificity of cone-beam computed tomography (CBCT) and magnetic resonance imaging (MRI) in detecting osteoarthritis (OA) of the temporomandibular joint (TMJ). This was done by using computed tomography (CT) and the research diagnostic criteria for temporomandibular disorders (RDC/TMD) as reference methods and using CBCT and MRI as index methods. A specific search strategy was developed and applied to these electronic databases: PubMed, Embase, DOSS, and Cochrane. The search results returned 802 articles, which were then narrowed down using the inclusion/exclusion criteria, to four final articles that were included in this review. Two of these articles used CBCT as their index method, and the other two used MRI. The sensitivity and specificity for CBCT was calculated to be moderate. Regarding MRI, we were not able to retrieve the raw data necessary so sensitivity and specificity were unable to be calculated. It was concluded that while CBCT and MRI show promise in their use as a diagnostic tool in the diagnosis of OA of the TMJ, more studies are needed to fully evaluate their validity

Genetic base broadening in tomato (Lycopersicon esculentum Mill.)

Genetic variability in many modern crops is very limited because of bottlenecks during domestication and past selection pressures. This narrow genetic base has resulted in a lack o f genetic variability in some crops, and increasing the susceptibility to biotic and abiotic stresses, and may limit responsiveness to market needs. Tomato (Lycopersicon esculentum M ill.) is one of many autogamous crop species in which the exploited germplasm has been severely reduced as a result o f the process o f domestication, and particularly because the initial germ plasm used to generate much of the material exploited in current varieties, represented a very small fraction of the initial variability available. The concept of genetic base broadening has been suggested as a means of mitigating this lack o f diversity in modern crops, with the aim to utilise the rich genetic resources available in wild relatives, vintage varieties, and land races. Genetic base broadening programmes involve the systematic utilisation of an arrangement o f genetic variability in such a way as to generate a mass of newly adapted gene stocks available as parents in breeding programmes.This research examines options available within a genetic base broadening program me, limited by space and time. Different populations were created by hybridisation in order to examine options and feasibility within a base broadening programme. These included a study of the genetic diversity of the genus Lycopersicon, using 43 accessions o f different taxa to examine the level o f genetic variability in tomato, and the richness o f diversity available in wild relatives and vintage/landrace tomato cultivars. Hybridisation was conducted as part of genetic base broadening program me to create inter-taxon and intra-taxon crosses between selected tomato cultivars and wild relatives. As part o f possible strategies, double crosses between inter-taxon populations were tested and analysed. The created populations were selfed and examined using morphological and molecular markers for polymorphism , genetic distances and heterozygosity indices from genetic population analysis computational program packages Popgene and NTSYS.Results are presented for these populations over a number of generations and reviewed against possible strategies for conservation and utilisation of this sample of populations for future breeding programmes. Results showed that there is large genetic diversity at morphological and molecular level between and within Lycopersicon taxa. L. esculentum presented limited genetic diversity within the accessions examined, and a narrow genetic base. However, substantial sources of genetic diversity are available to incorporate into the cultivated tomato from both wild relatives and old varieties and landraces of the cultivated species.After hybridisation, the created populations did not follow the expectation of autogamous crops, and revealed only a tendency toward decreasing genetic variability in further generations. The F t generation behaved as expected, for both morphological and molecular markers, but in F2 and F3 generations, the results fluctuated from increasing to decreasing values for all indices examined. However, from the data obtained it was possible to theorise about the number of parents to be involved, and the created population size that should be used in genetic base broadening programmes, along with strategies for the conservation of the created genetic variability.The methods utilised in this project, morphological and molecular markers, gave valuable information about the genetic diversity in self-pollinating generations. However, morphological characters were more limited than molecular markers in respect to information accuracy, because of the number and type o f traits selected. The sample size affected both type of markers. From the genetic indices utilised, average gene diversity (Hs), total gene diversity (//,), and effective number of alleles (Ae) were more informative than the arbitrary mean proportion o f polymorphic loci (P) and number of polymorphic alleles (A). However, all indices had some m erit and usefulness in analysing the data obtained in this research.For the future, it is hoped to use the experience gained with Lycopersicon spp utilising morphological and molecular markers in order to answer some more of the questions that will arise in any genetic base broadening program me

Identification and biotechnological characterization of lactic acid bacteria isolated from chickpea sourdough in northwestern Argentina

Chickpea, a relevant legume worldwide, can be nutritional and functionally improved by fermentation with lactic acid bacteria (LAB). In order to select suitable autochthonous starter cultures, we isolated and identified LAB from kabuli chickpeas cultivated and consumed in northwestern Argentina, and screened their relevant techno-functional properties. Chickpeas were milled and spontaneously fermented with daily back-slopping at 37 °C for 6 days and evolution of microbial populations were followed by plate counting. Phenotypic and genotypic methods including (GTG)5-based PCR fingerprinting and 16S rDNA sequencing were used to differentiate and identify the isolates to species level. A marked increase of LAB counts was observed throughout fermentation raising from 0.88 ± 0.35 log CFU/g of unfermented flours to 9.61 ± 0.21 log CFU/g after 5 backslopping steps with a concomitant pH decline from 6.09 ± 0.05 to 4.40 ± 0.03. Eighteen strains belonging to four LAB genera and six species: Enterococcus durans, E. mundtii, Lactococcus garvieae, Pediococcus pentosaceus, Weissella cibaria and W. paramesenteroides were identified in chickpea sourdoughs. Based on their abilities, Weissella cibaria CRL 2205 (acidification capacity), W. paramesenteroides CRL 2191 (proteolytic activity), Pediococcus pentosaceus CRL 2145 (gallate decarboxylase and peptidase activities), Lactococcus garviae CRL 2199 (α-galactosidase activity) and E. durans CRL 2193 (antimicrobial activity), were selected to design novel fermented chickpea products.Fil: Saez, Gabriel Dario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad San Pablo Tucumán; ArgentinaFil: Saavedra, Maria Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Hebert, Elvira Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Zarate, Gabriela del Valle. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; Argentina. Universidad San Pablo Tucumán; Argentin

La contabilidad ambiental y el impacto financiero de los costos ambientales para el desarrollo sostenible de la empresa multinacional de la industria de bebidas Coca Cola Company en el Ecuador

The present study aims to analyse the environmental accounting and the financial impact of the environmental costs for sustainable development of a multinational corporation within the beverage company such as Coca Cola Company in Ecuador. Since 2010, Coca Cola Company in Ecuador performs business operations under the name of Arca Ecuador, which is a part of the Mexican group Arca Continental that manages Coca Cola Brand in Mexico, Argentina and Ecuador. Sustainable development is part of the culture of Coca Cola and all of its representatives around the world are required to present “Sustainability Report” every year. This information is an organizational report that gives evidence about economic, environmental, social, and governance performance containing a list of the activities developed and amount of investment. The main programs performed by Coca Cola Ecuador in 2012 were: bottles recycling, water usage optimization, and the acquisition of technology for the efficient use of energy.El presente estudio tiene como fin analizar la cuenta ambiental y el impacto financiero de los costos ambientales para el desarrollo sostenible de una empresa multinacional dentro de la industria de bebidas como es Coca Cola Company en Ecuador. Desde el 2010, Coca Cola Company en Ecuador realiza operaciones de negocios bajo el nombre de Arca Ecuador, misma que es parte del grupo Mexicano Arca Continental que maneja la marca Coca Cola en México, Argentina y Ecuador. El desarrollo sostenible es parte de la cultura de Coca Cola y todos sus representantes a nivel mundial están requeridos a presentar anualmente un “Reporte de Sostenibilidad”. Este informe provee información de las actividades e inversiones para el desarrollo económico, ambiental, social y el gobierno corporativo. Las principales actividades realizadas por Coca Cola Ecuador en el 2012 fueron: reciclaje de botellas, optimización del uso del agua y adquisición de tecnología para el uso eficiente de energía

Analysis of corporate bond emissions and their impact on value creation of companies in Colombia for the period 1999-2009

This paper makes an analysis of the financing structures of large firms in Colombia and its effects on value creation for the period 1999 to 2009. In the first instance, this paper presents a theoretical review on value creation and capital structures in a second time are classified and characterized by companies in Colombia for their financial structures, and a third stage involves the calculation of Value Economic Added (EVA) for large companies in Colombia. The calculations are based on data from the Information System and Enterprise Risk (Sirem) of the Superintendency of CompaniesEste documento realiza un análisis sobre las estructuras de financiamiento de las grandes empresas en Colombia y sus efectos en la creación de valor para el periodo de 1999-2009. En primera instancia, el artículo aborda una revisión teórica sobre la creación de valor y las estructuras de capital; en un segundo momento, se clasifican y caracterizan las empresas en Colombia por sus estructuras de financiamiento, y en una tercera etapa, se realiza el cálculo del valor económico agregado (EVA) para las grandes empresas en Colombia. Los cálculos se realizan con base en los datos del Sistema de Información y Riesgo Empresarial (Sirem) de la Superintendencia de Sociedade

Optical Fibre Communication Systems in the Nonlinear Regime

This thesis studies solutions to increase the capacity of optical communication systems in the presence of nonlinear effects. Extending the optical bandwidth and mitigating nonlinear distortions were identified as promising ways to increase the throughput in transmission system. Raman amplification was investigated as a potential replacement of the conventional erbium-doped fibre amplifier (EDFA). In this context, the performance of discrete and distributed Raman amplifiers was studied in the linear and nonlinear regimes. Despite the bandwidth benefits, discrete Raman amplifiers were shown to exhibit an increased noise figure and nonlinear distortions, compared to EDFA. Additionally, for the first time, a thorough study of digital back-propagation for distributed Raman amplified links was performed, allowing for higher transmission rates at the expense of an increase of 25% in the algorithm complexity. A major focus of this work was to investigate the growth of nonlinear distortions in optical communication systems as the bandwidth is expanded. This work was the first to experimentally validate the Gaussian noise model (and variations accounting for inter-channel Raman scattering) in a wideband transmission regime up to 9~THz. Using these models, the merit of increasing the optical bandwidth was addressed, showing a beneficial sublinear increase in throughput despite the growth of nonlinear effects. An alternative nonlinear compensation method is optical phase conjugation (OPC). The performance of OPC was experimentally evaluated over an installed fibre link, showing limited improvements when OPC is used with practical transmission constraints. To overcome this limitation, a new method combining OPC and Volterra equalisation was developed. This method was shown to enhance the performance of two limited nonlinear compensation techniques, offering an attractive trade-off between performance and complexity. The results obtained in this research allow for higher information throughput to be transmitted, and can be used to plan and design future communication system and networks around the world

Analytical Modeling Approach to Study Harmonic Mitigation in AC Grids with Active Impedance at Selective Frequencies

This paper presents an analytical model, oriented to study harmonic mitigation aspects in AC grids. As it is well known, the presence of non-desired harmonics in AC grids can be palliated in several manners. However, in this paper, a power electronic-based active impedance at selective frequencies (ACISEF) is used, due to its already proven flexibility and adaptability to the changing characteristics of AC grids. Hence, the proposed analytical model approach is specially conceived to globally consider both the model of the AC grid itself with its electric equivalent impedances, together with the power electronic-based ACISEF, including its control loops. In addition, the proposed analytical model presents practical and useful properties, as it is simple to understand and simple to use, it has low computational cost and simple adaptability to different scenarios of AC grids, and it provides an accurate enough representation of the reality. The benefits of using the proposed analytical model are shown in this paper through some examples of its usefulness, including an analysis of stability and the identification of sources of instability for a robust design, an analysis of effectiveness in harmonic mitigation, an analysis to assist in the choice of the most suitable active impedance under a given state of the AC grid, an analysis of the interaction between different compensators, and so on. To conclude, experimental validation of a 2.15 kA ACISEF in a real 33 kV AC grid is provided, in which real users (household and industry loads) and crucial elements such as wind parks and HVDC systems are near inter-connected