Co-axial dual-core resonant leaky fibre for optical amplifiers

We present a co-axial dual-core resonant leaky optical fibre design, in which the outer core is made highly leaky. A suitable choice of parameters can enable us to resonantly couple power from the inner core to the outer core. In a large-core fibre, such a resonant coupling can considerably increase the differential leakage loss between the fundamental and the higher order modes and can result in effective single-mode operation. In a small-core single-mode fibre, such a coupling can lead to sharp increase in the wavelength dependent leakage loss near the resonant wavelength and can be utilized for the suppression of amplified spontaneous emission and thereby gain equalization of an optical amplifier. We study the propagation characteristics of the fibre using the transfer matrix method and present an example of each, the large-mode-area design for high power amplifiers and the wavelength tunable leakage loss design for inherent gain equalization of optical amplifiers.Comment: 6 page

Monomeric PcrA helicase processively unwinds plasmid lengths of DNA in the presence of the initiator protein RepD

The helicase PcrA unwinds DNA during asymmetric replication of plasmids, acting with an initiator protein, in our case RepD. Detailed kinetics of PcrA activity were measured using bulk solution and a single-molecule imaging technique to investigate the oligomeric state of the active helicase complex, its processivity and the mechanism of unwinding. By tethering either DNA or PcrA to a microscope coverslip surface, unwinding of both linear and natural circular plasmid DNA by PcrA/RepD was followed in real-time using total internal reflection fluorescence microscopy. Visualization was achieved using a fluorescent single-stranded DNA-binding protein. The single-molecule data show that PcrA, in combination with RepD, can unwind plasmid lengths of DNA in a single run, and that PcrA is active as a monomer. Although the average rate of unwinding was similar in single-molecule and bulk solution assays, the single-molecule experiments revealed a wide distribution of unwinding speeds by different molecules. The average rate of unwinding was several-fold slower than the PcrA translocation rate on single-stranded DNA, suggesting that DNA unwinding may proceed via a partially passive mechanism. However, the fastest dsDNA unwinding rates measured in the single-molecule unwinding assays approached the PcrA translocation speed measured on ssDNA

Dispersive properties of quasi-phase-matched optical parametric amplifiers

The dispersive properties of non-degenerate optical parametric amplification in quasi-phase-matched (QPM) nonlinear quadratic crystals with an arbitrary grating profile are theoretically investigated in the no-pump-depletion limit. The spectral group delay curve of the amplifier is shown to be univocally determined by its spectral power gain curve through a Hilbert transform. Such a constraint has important implications on the propagation of spectrally-narrow optical pulses through the amplifier. In particular, it is shown that anomalous transit times, corresponding to superluminal or even negative group velocities, are possible near local minima of the spectral gain curve. A possible experimental observation of such effects using a QPM Lithium-Niobate crystal is suggested.Comment: submitted for publicatio

Kinetic Mechanism of Initiation by RepD as a Part of Asymmetric, Rolling Circle Plasmid Unwinding

ABSTRACT: Some bacterial plasmids carry antibiotic resistance genes and replicate by an asymmetric, rolling circle mechanism, in which replication of the two strands is not concurrent. Initiation of this replication occurs via an initiator protein that nicks one DNA strand at the double-stranded origin of replication. In this work, RepD protein from the staphylococcal plasmid pC221 carries this function and allows PcrA helicase to bind and begin unwinding the plasmid DNA. This work uses whole plasmid constructs as well as oligonucleotide-based mimics of parts of the origin to examine the initiation reaction. It investigates the phenomenon that nicking, although required to open a single-stranded region at the origin and so allow PcrA to bind, is not required for another function of RepD, namely to increase the processivity of PcrA, allowing it to unwind plasmid lengths of DNA. A kinetic mechanism of RepD initiation is presented, showing rapid binding of the origin DNA. The rate of nicking varies with the structure of the DNA but can occur with a rate constant of>25 s −1 at 30 °C. The equilibrium constant of the nicking reaction, which involves a transesterification to form a phosphotyrosine bond within the RepD active site, is close to unity. Bacterial plasmids are extrachromosomal genetic elements

Casos de buenas prácticas en el uso de pequeños generadores con energías renovables

La Matriz Energética Argentina requiere promover su diversificación incentivando la generación eléctrica distribuida, con recursos renovables locales, por parte de pequeños consumidoresproductores inyectando la energía generada a la red de baja tensión. Con este objetivo esta ponencia, elaborada con una mirada integradora que trata de incorporar el uso de las energías renovables al colectivo social y las políticas urbanas locales, se desarrolla conforme a dos aspectos que se consideran significativos: El marco normativo, infiriendo que su existencia y/o sanción debería alentar la generación eléctrica distribuida en bajas potencias, con incorporación al sistema interconectado. El enfoque instrumental a través del análisis de casos - buenas prácticas. Se consideran buenas prácticas a las acciones destinadas a mejorar las condiciones de vida de la comunidad. Conocerlas permite compartir experiencias valiosas incrementando el grado de conciencia de quienes toman decisiones sobre soluciones potenciales a los problemas sociales, económicos y medio ambientales locales.Argentina Energy Matrix requires promoting its diversification by encouraging the distributed electricity generation, with local renewable resources, by small consumers-producers incorporating their generated energy to the distribution networks in low voltage. With this objective this paper, made with an integrative look that seeks to incorporate the use of renewable energies to the collective social and local urban policies, develops according to two aspects that are considered significant: Normative framework, inferring that their existence and/or enactment should encourage the distributed electricity generation in low powers, with incorporation to the grid. Instrumental approach through the analysis of cases - good practice. It is considered good practice to actions designed to improve the living conditions of the community. To know them allows to share valuable experiences increasing the level of awareness of those who take decisions on potential solutions to social problems, economic and environmental premises.Tema 13: Generación distribuida.Facultad de Arquitectura y Urbanism

Sperm competition-induced plasticity in the speed of spermatogenesis

Background: Sperm competition between rival ejaculates over the fertilization of ova typically selects for the production of large numbers of sperm. An obvious way to increase sperm production is to increase testis size, and most empirical work has focussed on this parameter. Adaptive plasticity in sperm production rate could also arise due to variation in the speed with which each spermatozoon is produced, but whether animals can respond to relevant environmental conditions by modulating the kinetics of spermatogenesis in this way has not been experimentally investigated. Results: Here we demonstrate that the simultaneously hermaphroditic flatworm Macrostomum lignano exhibits substantial plasticity in the speed of spermatogenesis, depending on the social context: worms raised under higher levels of sperm competition produce sperm faster. Conclusions: Our findings overturn the prevailing view that the speed of spermatogenesis is a static property of a genotype, and demonstrate the profound impact that social environmental conditions can exert upon a key developmental process. We thus identify, to our knowledge, a novel mechanism through which sperm production rate is maximised under sperm competition

Casos de buenas prácticas en el uso de pequeños generadores con energías renovables

La Matriz Energética Argentina requiere promover su diversificación incentivando la generación eléctrica distribuida, con recursos renovables locales, por parte de pequeños consumidoresproductores inyectando la energía generada a la red de baja tensión. Con este objetivo esta ponencia, elaborada con una mirada integradora que trata de incorporar el uso de las energías renovables al colectivo social y las políticas urbanas locales, se desarrolla conforme a dos aspectos que se consideran significativos: El marco normativo, infiriendo que su existencia y/o sanción debería alentar la generación eléctrica distribuida en bajas potencias, con incorporación al sistema interconectado. El enfoque instrumental a través del análisis de casos - buenas prácticas. Se consideran buenas prácticas a las acciones destinadas a mejorar las condiciones de vida de la comunidad. Conocerlas permite compartir experiencias valiosas incrementando el grado de conciencia de quienes toman decisiones sobre soluciones potenciales a los problemas sociales, económicos y medio ambientales locales.Argentina Energy Matrix requires promoting its diversification by encouraging the distributed electricity generation, with local renewable resources, by small consumers-producers incorporating their generated energy to the distribution networks in low voltage. With this objective this paper, made with an integrative look that seeks to incorporate the use of renewable energies to the collective social and local urban policies, develops according to two aspects that are considered significant: Normative framework, inferring that their existence and/or enactment should encourage the distributed electricity generation in low powers, with incorporation to the grid. Instrumental approach through the analysis of cases - good practice. It is considered good practice to actions designed to improve the living conditions of the community. To know them allows to share valuable experiences increasing the level of awareness of those who take decisions on potential solutions to social problems, economic and environmental premises.Tema 13: Generación distribuida.Facultad de Arquitectura y Urbanism

Casos de buenas prácticas en el uso de pequeños generadores con energías renovables

La Matriz Energética Argentina requiere promover su diversificación incentivando la generación eléctrica distribuida, con recursos renovables locales, por parte de pequeños consumidoresproductores inyectando la energía generada a la red de baja tensión. Con este objetivo esta ponencia, elaborada con una mirada integradora que trata de incorporar el uso de las energías renovables al colectivo social y las políticas urbanas locales, se desarrolla conforme a dos aspectos que se consideran significativos: El marco normativo, infiriendo que su existencia y/o sanción debería alentar la generación eléctrica distribuida en bajas potencias, con incorporación al sistema interconectado. El enfoque instrumental a través del análisis de casos - buenas prácticas. Se consideran buenas prácticas a las acciones destinadas a mejorar las condiciones de vida de la comunidad. Conocerlas permite compartir experiencias valiosas incrementando el grado de conciencia de quienes toman decisiones sobre soluciones potenciales a los problemas sociales, económicos y medio ambientales locales.Argentina Energy Matrix requires promoting its diversification by encouraging the distributed electricity generation, with local renewable resources, by small consumers-producers incorporating their generated energy to the distribution networks in low voltage. With this objective this paper, made with an integrative look that seeks to incorporate the use of renewable energies to the collective social and local urban policies, develops according to two aspects that are considered significant: Normative framework, inferring that their existence and/or enactment should encourage the distributed electricity generation in low powers, with incorporation to the grid. Instrumental approach through the analysis of cases - good practice. It is considered good practice to actions designed to improve the living conditions of the community. To know them allows to share valuable experiences increasing the level of awareness of those who take decisions on potential solutions to social problems, economic and environmental premises.Tema 13: Generación distribuida.Facultad de Arquitectura y Urbanism

Extradural autologous temporal muscle graft mimicking a meningioma: Case report

Meningiomas are the most common dural tumour, but there are also many other dural masses which mimic their appearances, such as neoplastic and non-neoplastic lesions. In this paper we report another mass which may mimic a dural lesion, namely a muscle graft harvested from the temporal site and left in situ, used to achieve haemostasis in a posttraumatic temporal extradural hematoma in a young male patient. Solid knowledge of differentiating neuroimaging characteristics of dural masses, as well as its corroboration with the patient’s medical history are extremely helpful in establishing an accurate diagnostic