Mostrando recursos 1 - 20 de 15.168

  1. LLC resonant charger with variable inductor control

    Costa, Válter de Sousa
    The present work pretends to study the operation and behavior of the LLC resonant converter topology considering a battery charging application, using the traditional switching frequency control and a new control variable, the variable inductance, provided by a current controlled device, the Variable Inductor (VI). During this work, a brief state of the art regarding general types of power converters and resonant power converters is presented. The LLC resonant converter topology and its advantages and disadvantages are described. The VI principle of operation and structure is presented and discussed and, in the end some information about batteries and its behavior under charging and discharging conditions is presented. The...

  2. Retinal atrophy in relation to visual functioning and vision-related quality of life in patients with multiple sclerosis.

    Balk, LJ; Coric, D; Nij Bijvank, JA; Killestein, J; Uitdehaag, BM; Petzold, A
    BACKGROUND: Inner retinal layer atrophy in patients with multiple sclerosis (MS) has been validated as a structural imaging biomarker for neurodegeneration. OBJECTIVE: To determine how retinal layer thickness relates to high-contrast visual acuity (HCVA), low-contrast visual acuity (LCVA) and vision-related quality of life (QoL) and to investigate the effect of previous episodes on MS-associated optic neuritis (MSON). METHODS: Spectral-domain optical coherence tomography (SD-OCT) was performed in 267 patients with MS. Images were segmented for the peripapillary retinal nerve fiber layer (pRNFL) and the macular ganglion cell inner plexiform layer (GCIPL). Ophthalmological evaluations included history of MSON, HCVA, LCVA, and vision-related...

  3. Craniosynostosis

    Greig, AVH; Dunaway, DJ
    © 2015 John Wiley & Sons, Ltd. All rights reserved.Craniosynostosis is defined as the premature fusion of cranial sutures, which may be due to primary or secondary causes. Either a single suture or multiple sutures may be involved and these cause a change in head shape. Single suture synostosis is usually non-syndromic but craniosynostosis can be associated with several syndromes, including Apert, Crouzon, Pfeiffer, Saethre-Chotzen, Carpenter and Muenke syndromes. Syndromic craniosynostosis patients may present with elevated intracranial pressure, hydrocephalus, papilloedema, optic atrophy, corneal exposure or ulceration, globe herniation, amblyopia, astigmatism, squints and loss of vision. They may present with hearing...

  4. Measuring Primary and Secondary Degeneration of Retinal Ganglion Cells in the Rodent Partial Optic Nerve Transection Model

    Davis, B; Guo, L; Brenton, J; Langley, L; Normando, EM; Cordeiro, MF

  5. Irradiation campaign in the EOLE critical facility of fiber optic Bragg gratings dedicated to the online temperature measurement in zero power research reactors

    Morana, Adriana; Mellier, Frederic; Cheymol, Guy; Destouches, Christophe; SALVO, JACQUES DI; Girard, Sylvain; Laffont, Guillaume; Marin, Emmanuel
    International audience

  6. On-line Characterization of Gamma Radiation Effects on Single-Ended Raman Based Distributed Fiber Optic Sensor

    Cangialosi, C.; Girard, Sylvain; Cannas, Marco; Boukenter, Aziz; Marin, Emmanuel; Agnello, S.; Delepine-Lesoille, S.; Marcandella, Claude; Paillet, Philippe; Ouerdane, Youcef
    International audience

  7. The Identification of Power-In Region in Vortex-Induced Vibration of Flexible Cylinders

    Rao, Zhibiao; Resvanis, Themistocles L; Vandiver, John Kim
    This paper proposes a novel method to identify the power-in regions of long flexible cylinders subjected to vortex-induced vibration (VIV). It also attempts to address a practical problem: “Will a secondary power-in region appear after the primary power-in region is covered with suppression devices?” The source of data is a recent model test on a 38 meter long flexible cylinder, densely instrumented with fiber optic strain gauges and accelerometers. For pipes with partial coverage of suppression devices in uniform flow, the bare region would be expected to be a power-in region and the section with suppression devices is expected to...

  8. Combined and three-dimensional rendered multimodal data for planning cranial base surgery: a prospective evaluation.

    Gandhe, AJ; Hill, DL; Studholme, C; Hawkes, DJ; Ruff, CF; Cox, TC; Gleeson, MJ; Strong, AJ
    Magnetic resonance (MR), X-ray computed tomography (CT), and angiographic images best depict soft tissue, bone, and blood vessels respectively. No one on its own is sufficient in the preoperative assessment of cranial base lesions. We have developed and evaluated a computational technique for the three-dimensional (3D) combination and display of multimodality images for planning cranial base surgery. This evaluation was prospective and performed in such a way that the results could be quantified. Eight patients (three acoustic neuromas, four subfrontal and suprasellar meningiomas, and one petrous apex meningioma) underwent MR, CT, and MR angiographic investigations. These images were registered with...

  9. A recurrent de novo mutation in ACTG1 causes isolated ocular coloboma.

    Rainger, J; Williamson, KA; Soares, DC; Truch, J; Kurian, D; Gillessen-Kaesbach, G; Seawright, A; Prendergast, J; Halachev, M; Wheeler, A; McTeir, L; Gill, AC; van Heyningen, V; Davey, MG; UK10K,; FitzPatrick, DR
    Ocular coloboma (OC) is a defect in optic fissure closure and is a common cause of severe congenital visual impairment. Bilateral OC is primarily genetically determined and shows marked locus heterogeneity. Whole exome sequencing was used to analyse twelve trios (child affected with OC and both unaffected parents), This identified de novo mutations in ten different genes in eight probands. Three of these genes encoded proteins associated with actin cytoskeleton dynamics: ACTG1, TWF1 and LCP1. Proband-only whole exome sequencing identified a second unrelated individual with isolated OC carrying the same ACTG1 allele, encoding p.(Pro70Leu). Both individuals have normal neurodevelopment with...

  10. Pontocerebellar hypoplasia type 2D and optic nerve atrophy further expand the spectrum associated with selenoprotein biosynthesis deficiency

    Pavlidou, E; Salpietro, V; Phadke, R; Hargreaves, LP; Batten, L; McElreavy, K; Pitt, M; Mankad, K; Wilson, C; Cutrupi, MC; Ruggieri, M; McCormick, D; Saggar, A; Kinali, M

  11. Estudo da comunidade de diatomáceas (BACILARIOPHYTA) epifíticas em marismas da costa do sul do Brasil

    Bertolli, Lucielle Merlym
    Diatomáceas são importantes constituintes do epifíton em ambientes costeiros. Estratégias de fixação conferem a estas algas vantagem adaptativa, no entanto, as mesmas estão sujeitas às variações ambientais, podendo responder com alterações da composição e estrutura da comunidade. Embora a relação entre epifíton e substrato seja pouco compreendida, a arquitetura do substrato parece influenciar na comunidade aderida. A composição, estrutura e variação sazonal de diatomáceas epifíticas foram avaliadas em ambientes de marismas no estuário da Lagoa dos Patos, sul do Brasil. Três sítios foram amostrados, Saco do Silveira, Ilha da Pólvora e São José do Norte, distantes 36, 18 e 9...

  12. Incorporação de moinha de carvão vegetal na produção de coques em forno piloto

    Orellana, Daniel Rigon
    A reutilização de resíduos e sua destinação são desafios seguidamente enfrentados na indústria. Por ser extensa e empregar uma grande variedade de processos, matérias-primas e insumos, a cadeia do aço se beneficia por ter ampla flexibilidade e diversas possibilidades de reintrodução de compostos em sua rota de fabricação. Resíduos carbonosos, por exemplo, podem ser parcialmente usados em misturas de carvões no processo de coqueificação dependendo do tamanho e da composição química. Este trabalho, teve como objetivo, avaliar a influência da adição de moinha de carvão vegetal em uma mistura de carvões para a produção de coques em forno piloto de...

  13. Author response: Gray matter MRI differentiates neuromyelitis optica from multiple sclerosis using random forest.

    Eshaghi, A; Ciccarelli, O

  14. A Period of Controlled Elevation of IOP (CEI) Produces the Specific Gene Expression Responses and Focal Injury Pattern of Experimental Rat Glaucoma

    Morrison, JC; Cepurna, WO; Tehrani, S; Choe, TE; Jayaram, H; Lozano, DC; Fortune, B; Johnson, EC
    PURPOSE: We determine if several hours of controlled elevation of IOP (CEI) will produce the optic nerve head (ONH) gene expression changes and optic nerve (ON) damage pattern associated with early experimental glaucoma in rats. METHODS: The anterior chambers of anesthetized rats were cannulated and connected to a reservoir to elevate IOP. Physiologic parameters were monitored. Following CEI at various recovery times, ON cross-sections were graded for axonal injury. Anterior ONHs were collected at 0 hours to 10 days following CEI and RNA extracted for quantitative PCR measurement of selected messages. The functional impact of CEI was assessed by electroretinography...

  15. Influence of Population Variation of Physiological Parameters in Computational Models of Space Physiology

    Myers, J. G.; Werner, C.; Ethier, C. R.; Nelson, E. S.; Raykin, J.; Samuels, B.; Feola, A.
    The earliest manifestations of Visual Impairment and Intracranial Pressure (VIIP) syndrome become evident after months of spaceflight and include a variety of ophthalmic changes, including posterior globe flattening and distension of the optic nerve sheath. Prevailing evidence links the occurrence of VIIP to the cephalic fluid shift induced by microgravity and the subsequent pressure changes around the optic nerve and eye. Deducing the etiology of VIIP is challenging due to the wide range of physiological parameters that may be influenced by spaceflight and are required to address a realistic spectrum of physiological responses. Here, we report on the application of...

  16. Design of photovoltaics for modules with 50% efficiency

    Warmann, Emily C.; Flowers, Cristofer; Lloyd, John; Eisler, Carissa N.; Escarra, Matthew D.; Atwater, Harry A.
    We describe a spectrum splitting solar module design approach using ensembles of 2–20 subcells with bandgaps optimized for the AM1.5D spectrum. Device physics calculations and experimental data determine radiative efficiency parameters for III-V compound semiconductor subcells and enable modification of conventional detailed balance calculations to predict module efficiency while retaining computational speed for a wide search of the design space. Accounting for nonideal absorption and recombination rates due to realistic material imperfections allows us to identify the minimum subcell quantity, quality, electrical connection configuration, and concentration required for 50% module efficiency with realistic optical losses and modeled contact resistance losses....

  17. Characterizing microglia activation: a spatial statistics approach to maximize information extraction.

    Davis, BM; Salinas-Navarro, M; Cordeiro, MF; Moons, L; Groef, LD
    Microglia play an important role in the pathology of CNS disorders, however, there remains significant uncertainty about the neuroprotective/degenerative role of these cells due to a lack of techniques to adequately assess their complex behaviour in response to injury. Advancing microscopy techniques, transgenic lines and well-characterized molecular markers, have made histological assessment of microglia populations more accessible. However, there is a distinct lack of tools to adequately extract information from these images to fully characterise microglia behaviour. This, combined with growing economic pressures and the ethical need to minimise the use of laboratory animals, led us to develop tools to...

  18. A study of the geophysical response of distributed fibre optic acoustic sensors through laboratory-scale experiments

    Papp, Bence; Donno, Daniela; Martin, James E.; Hartog, Arthur H.
    International audience

  19. Creating Automation to Couple Laser Light from an Optical Fiber to a Photonic Integrated Circuit

    Maharry, Aaron
    Coupling light between fiber optic cables and photonic devices on silicon chips is important for optical communications. Recently, vertically bent cantilever couplers have been developed that have better bandwidth and lower power loss than grating couplers, which are the current standard for fiber-to-chip coupling. A system that can perform butt-coupling between optical fibers and cantilever couplers on an integrated silicon photonic device is reported here. This system is able to perform butt coupling using vision processing and measured coupled power as feedback, and requires minimal human assistance. This system can be extended to automatically collect measurements from multiple devices on...

  20. Superconducting nanowire single-photon detectors on aluminum nitride photonic integrated circuits

    Zhu, Di, S.M. Massachusetts Institute of Technology
    With recent advances in integrated single-photon sources and quantum memories, onchip integration of high-performance single-photon detectors becomes increasingly important. The superconducting nanowire single-photon detector (SNSPD) is the leading single-photon counting technology for quantum information processing. Among various waveguide materials, aluminum nitride (AlN) is a promising candidate because of its exceptionally wide bandgap, and intrinsic piezoelectric and electro-optic properties. In this Master's thesis, we developed a complete fabrication process for making high-performance niobium nitride SNSPDs on AlN, and demonstrated their integration with AlN photonic waveguides. The detectors fabricated on this new substrate material have demonstrated saturated detection efficiency from visible to...

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