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The Relationship between Intraocular Pressure Reduction and Rates of Progressive Visual Field Loss in Eyes with Optic Disc Hemorrhage

MEDEIROS, Felipe A.; ALENCAR, Luciana M.; SAMPLE, Pamela A.; ZANGWILL, Linda M.; SUSANNA JR., Remo; WEINREB, Robert N.
Fonte: ELSEVIER SCIENCE INC Publicador: ELSEVIER SCIENCE INC
Tipo: Artigo de Revista Científica
ENG
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Purpose: To evaluate rates of visual field progression in eyes with optic disc hemorrhages and the effect of intraocular pressure (IOP) reduction on these rates. Design: Observational cohort study. Participants: The study included 510 eyes of 348 patients with glaucoma who were recruited from the Diagnostic Innovations in Glaucoma Study (DIGS) and followed for an average of 8.2 years. Methods: Eyes were followed annually with clinical examination, standard automated perimetry visual fields, and optic disc stereophotographs. The presence of optic disc hemorrhages was determined on the basis of masked evaluation of optic disc stereophotographs. Evaluation of rates of visual field change during follow-up was performed using the visual field index (VFI). Main Outcome Measures: The evaluation of the effect of optic disc hemorrhages on rates of visual field progression was performed using random coefficient models. Estimates of rates of change for individual eyes were obtained by best linear unbiased prediction (BLUP). Results: During follow-up, 97 (19%) of the eyes had at least 1 episode of disc hemorrhage. The overall rate of VFI change in eyes with hemorrhages was significantly faster than in eyes without hemorrhages (-0.88%/year vs. -0.38%/year...

Retinal removal up-regulates cannabinoid CB1 receptors in the chick optic tectum

CHAVES, Gabriela P.; NOGUEIRA, Tatiane C. A.; BRITTO, Luiz R. G.; BORDIN, Silvana; TORRAO, Andrea S.
Fonte: WILEY-LISS Publicador: WILEY-LISS
Tipo: Artigo de Revista Científica
ENG
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The endocannabinoid system has been implicated in several neurobiological processes, including neurodegeneration and neuro protection. The aim of this study was to evaluate the effects of unilateral retinal ablation on the expression of the cannabinoid receptor subtype 1 (CB1) at both protein and mRNA levels in the optic tectum of the adult chick brain. After different survival times postlesion (2-30 days), the chick brains were subjected to immunohistochemical, immunoblotting, and real-time PCR procedures to evaluate CB1 expression. TUNEL and Fluoro-Jade B were used to verify the possible occurrence of cell death, and immunostaining for the microtubule-associated protein MAP-2 was performed to verify possible dendritic remodeling after lesions. No cell death could be observed in the deafferented tectum, at least up to 30 days postlesion, although Fluoro-Jade B could reveal degenerating axons and terminals. Retinal ablation seems to generate an increase of CB1 protein in the optic tectum and other retinorecipient visual areas, which paralleled an increase in MAP-2 staining. On the other hand, CB, mRNA levels were not changed after retinal ablation. Our results reveal that CB, expression in visual structures of the adult chick brain may be negatively regulated by the retinal innervation. The increase of CB1 receptor expression observed after retinal removal indicates that these receptors are not presynaptic in retinal axons projecting to the tectum and suggests a role of the cannabinoid system in plasticity processes ensuing after lesions. (c) 2008 Wiley-Liss...

"Efeitos da anemia ferropriva e da estimulação tátil sobre a morfologia do nervo óptico em ratos." ; "Effects of the iron-deficient anemia and the tactile Stimulation on the Morphology of the Optic Nerve"

Homem, Jefferson Mallmann
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 27/02/2004 PT
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Vários trabalhos têm mostrado que a ingestão deficiente de ferro pode causar alterações nos parâmetros morfológicos e bioquímicos do Sistema Nervoso Central (SNC) do rato assim como em seu comportamento. Também, os animais deficientes em ferro mostram redução no número de lamelas de mielina e déficits de aprendizado. Por outro lado, a estimulação tátil pode reduzir e/ou evitar os danos causados pela má nutrição sobre o SNC e comportamento. Entretanto, os danos no processo de mielinização têm também sido vistos na anemia ferro-deficiente e, uma vez que o nervo óptico é em grande parte formado pelos axônios mielinizados, o objetivo deste estudo é verificar os efeitos da anemia ferropriva e estimulação tátil sobre a morfologia do nervo óptico de ratos Wistar machos aos 18, 22 e 32 dias de idade. Os animais foram divididos em 2 grupos: Controles ( C ) (35 mg Fe / Kg de dieta), Anêmicos ( A ) (4 mg Fe / Kg de dieta). Cada grupo foi subdividido em Estimulado ( E ) e Não Estimulado ( N ). O peso corporal, hemoglobina, hematócrito, área, perímetro, diâmetro mínimo, densidade de células gliais e número de vasos no nervo óptico foram avaliados. Os animais foram anestesiados com éter sulfúrico e sacrificados por perfusão cardíaca com PBS 0...

Avaliação morfológica e morfométrica dos efeitos da estimulação tátil neonatal sobre o nervo óptico de ratos Wistar hígidos ou submetidos a uma dieta deficiente em ferro no período pós-natal precoce; Morphological and morphometric evaluation of the effects of neonatal tactile stimulation on the optic nerve or healthy wistar rats subjected to a iron-deficient diet in the early post-natal period.

Barbosa, Everton Horiquini
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 01/11/2013 PT
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Diante da deficiência de ferro que leva a processos degenerativos do sistema nervoso central e da estimulação tátil neonatal como uma estratégia não invasiva e promissora para atenuar os déficits causados pela degeneração, assim, justifica-se comparar em ratos submetidos à dieta deficiente em ferro (A - 4mg/kg) ou dieta adequada em ferro (C - 35mg/kg) os efeitos da estimulação tátil neonatal, em relação aos aspectos morfológicos e morfométricos das células gliais, fibras mielínicas e vasos sanguíneos do nervo óptico, aos 18, 22 e 32 dias de idade. Foram utilizadas 12 ninhadas de ratos Wistar, compostas por 12 ratas-mãe e 72 filhotes machos recém-nascidos, que por sua vez, foram divididos em dois grupos de acordo com a dieta submetida às ratas-mãe (A e C). Metade das ninhadas do grupo A e C foram submetidas à estimulação tátil (E) e a outra metade não recebeu nenhuma forma de estímulo (N). Resultando, portanto, nos seguintes grupos experimentais: grupo controle não estimulado (CN), grupo controle estimulado (CE), grupo anêmico não estimulado (AN), e grupo anêmico estimulado (AE), cada grupo foi composto por 3 ratas-mães e 18 filhotes. Aos 18, 22 e 32 dias de vida, seis animais de cada grupo experimental foram profundamente anestesiados e perfundidos por via transcardíaca. Os nervos ópticos foram cuidadosamente dissecados com o auxílio de um estereomicroscópio (Stemi DRC...

Heterodyne Interferometry Applied to the Characterization of Acousto-Electro-Optic Light Modulators

Kitano, C.; Higuti, R. T.; Sakamoto, J. M. S.; Pacheco, G. M.; Linde, BBJ; Paczkowski, J; Ponikwicki, N
Fonte: American Institute of Physics (AIP) Publicador: American Institute of Physics (AIP)
Tipo: Conferência ou Objeto de Conferência Formato: 84-87
ENG
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When the electro-optic and acousto-optic effects are combined into a single device, the resulting acousto-electro-optic (AEO) modulator shows improved flexibility to overcome some limitations of the individual modulators or their cascade combinations. By using optical interferometry, it is possible to investigate the AEO modulator behavior as a function of this applied voltage. By this way, a lithium niobate AEO modulator is positioned in one of the arms of a Mach-Zehnder interferometer and operates at 62 MHz frequency, which constitutes the intermediate frequency of the heterodyne interferometer. Operating the AEO modulator in the acousto-optic small diffraction efficiency regime, the photodetected signal amplitude and phase are analyzed, and the induced phase shift, transmission curve and linearity response are obtained. The experimental results show good agreement with that expected from the coupled-mode theory. The possibility of linear control of the optical phase shift by the external voltage, from 0 to 2 p radians, is demonstrated.

Optic neuritis due to immunobiologics: first Brazilian case report

Silva,Luiz Gustavo Martins da; Sasso,Letícia Soares; Nelli,Carlos José; Bernardes Filho,Fred; Abreu,Marilda Aparecida Milanez Morgado de
Fonte: Sociedade Brasileira de Dermatologia Publicador: Sociedade Brasileira de Dermatologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2013 EN
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The change in immunological response obtained by immunobiologics has brought a new paradigm to the treatment of immune-mediated disorders. As a result of their efficacy, there is a positive impact on the quality of life of patients. However, severe side effects, such as demyelination of cerebral or peripheral nerves, have been reported. After review of literature using PubMed and MEDLINE data from 2000 to 2012, we identified the cases correlating the biological uniterms and optic neuritis. This article reports the first Brazilian optic neuritis case associated with the use of immunobiologics. This publication is justified by the rarity of the disease and atypical therapeutical evolution.

Adeno-associated viral-mediated catalase expression suppresses optic neuritis in experimental allergic encephalomyelitis

Guy, John; Qi, Xiaoping; Hauswirth, William W.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 10/11/1998 EN
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Suppression of oxidative injury by viral-mediated transfer of the human catalase gene was tested in the optic nerves of animals with experimental allergic encephalomyelitis (EAE). EAE is an inflammatory autoimmune disorder of primary central nervous system demyelination that has been frequently used as an animal model for the human disease multiple sclerosis (MS). The optic nerve is a frequent site of involvement common to both EAE and MS. Recombinant adeno-associated virus containing the human gene for catalase was injected over the right optic nerve heads of SJL/J mice that were simultaneously sensitized for EAE. After 1 month, cell-specific catalase activity, evaluated by quantitation of catalase immunogold, was increased approximately 2-fold each in endothelia, oligodendroglia, astrocytes, and axons of the optic nerve. Effects of catalase on the histologic lesions of EAE were measured by computerized analysis of the myelin sheath area (for demyelination), optic disc area (for optic nerve head swelling), extent of the cellular infiltrate, extravasated serum albumin labeled by immunogold (for blood–brain barrier disruption), and in vivo H2O2 reaction product. Relative to control, contralateral optic nerves injected with the recombinant virus without a therapeutic gene...

Dose-dependent and combined effects of N-methyl-D-aspartate receptor antagonist MK-801 and nitric oxide synthase inhibitor nitro-L-arginine on the survival of retinal ganglion cells in adult hamsters☆

Li, Yaoyu; Yang, An’an; Zhu, Tingting; Liu, Zhao; You, Siwei; So, Kwok-Fai
Fonte: Medknow Publications & Media Pvt Ltd Publicador: Medknow Publications & Media Pvt Ltd
Tipo: Artigo de Revista Científica
Publicado em 05/04/2012 EN
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This study investigated the effects of daily intraperitoneal injections of N-methyl-D-aspartate receptor antagonist MK-801 and nitric oxide synthase inhibitor nitro-L-arginine (L-NA) on the survival of retinal ganglion cells (RGCs) at 1 and 2 weeks after unilateral optic nerve transection in adult hamsters. The left optic nerves of all animals were transected intraorbitally 1 mm from the optic disc and RGCs were retrogradely labeled with Fluorogold before they received different daily dosages of single MK-801 or L-NA as well as daily combinational treatments of these two chemicals. All experimental and control animals survived for 1 or 2 weeks after optic nerve transection. Our results revealed that the mean numbers of surviving RGCs increased and then decreased when the dosage of MK-801 (1.0, 3.0 and 4.5 mg/kg) and L-NA (1.5, 3.0, 4.5 and 6.0 mg/kg) increased at both 1 and 2 weeks survival time points. Daily combinational use of 1.0 mg/kg MK-801 and 1.5 mg/kg L-NA lead to a highest RGC number that was even higher than the sum of the RGC numbers in 1.0 mg/kg MK-801 and 1.5 mg/kg L-NA subgroups at 2 weeks. These findings indicated that both MK-801 and L-NA can protect axotomized RGCs in a dose-dependent manner and combinational treatment of these chemicals possesses a potentiative and protective effect.

Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist inhibits apoptosis of retinal ganglion cells in a rabbit model of optic nerve injury★

Wang, Ruijia; Luan, Xinping; Mu, Yiti; Jia, Hongyu; Xu, Jingxuan
Fonte: Medknow Publications & Media Pvt Ltd Publicador: Medknow Publications & Media Pvt Ltd
Tipo: Artigo de Revista Científica
Publicado em 05/04/2012 EN
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35.71%
A rabbit model of traumatic optic nerve injury, established by occlusion of the optic nerve using a vascular clamp, was used to investigate the effects of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist GYKI 52466 on apoptosis of retinal ganglion cells following nerve injury. Hematoxylin-eosin staining and a terminal deoxynucleotidyl transferase dUTP nick end labeling assay showed that retinal ganglion cells gradually decreased with increasing time of optic nerve injury, while GYKI 52466 could inhibit this process. The results demonstrate that following acute optic nerve injury, apoptosis of retinal ganglion cells is a programmed process, which can be inhibited by the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist.

Photoelastic and electro-optic effects : study of PMN-29%PT single crystals

Di, Na (1977 - ); Quesnel, David J.
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:xiv, 111 leaves
ENG
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Thesis (Ph. D.)--University of Rochester. Dept. of Mechanical Engineering, 2010.; Relaxor ferroelectrics PMN-PT single crystals exhibit extra-high dielectric and piezoelectric properties compared with conventional piezoelectric ceramics. They are becoming widely used in high performance electromechanical devices. However, PMN-PT single crystals are elastically softer than PMN-PT polycrystalline ceramics. Mechanical loads and electric fields interact to produce fractures at relatively low stresses, and cracks grow under both AC and DC electric fields. To prevent the failure of the electromechanical devices, we need to have a better understanding of the mechanisms of fracture in this material when it is subjected to mechanical and electrical loadings. Photoelasticity is an efficient and effective method to measure the internal stress distributions of materials that result from both internal residual stress and external loading. I report the exploration of the use of this classic technique to study internal stresses inside PMN-PT single crystals through bending and Hertzian contact experiments. Effects under electric field loading were also investigated using birefringence techniques.

Optic nerve microvessels: A partial molecular definition of cell surface anionic sites

Lawrenson, J.; Reid, A.; Gajree, T.; Ghabriel, M.; Allt, G.
Fonte: Academic Press Publicador: Academic Press
Tipo: Artigo de Revista Científica
Publicado em //1995 EN
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Incorporated in the luminal glycocalyx of vascular endothelia (EC) are negatively charged microdomains (anionic sites). These sites are considered functionally important (a) in their interaction with circulating blood constituents, and (b) as a determinant of vascular permeability. The molecular composition of these EC sites, described for a number of tissues, has demonstrated a heterogeneity dependent on their anatomical location. Luminal anionic sites have not been characterized for EC of optic nerve. Optic nerves were removed from Sprague-Dawley rats previously fixed by vascular perfusion. EC anionic sites were labelled with the probes cationic colloidal gold (CCG) and cationic ferritin (CF), using the pre- and post-embedding techniques, and examined by electron microscopy. The effects of enzyme digestion of ultrathin sections on subsequent CCG labelling were determined using a battery of enzymes in association with the post-embedding technique. CCG labelling was quantified following each enzyme treatment using image analysis software. The biotinylated lectin wheat germ agglutinin (WGA) with streptavidin gold was also used to localize specific monosaccharide residues. The luminal front of intraneural EC showed a uniform labelling with CCG and CF which was greater than on the abluminal surface. Extracellular matrix components and basal laminae were moderately labelled. Digestion of tissue sections with heparitinase and trypsin had no significant effect on subsequent CCG labelling. Proteinase K was less effective than papain but both produced a significant reduction. Neuraminidase almost completely eliminated labelling. CCG binding to the luminal plasma membrane of optic nerve EC can be significantly reduced with proteolytic and glycolytic enzymes. The results demonstrate that sialoglycoproteins principally constitute these luminal EC anionic sites. Biotinylated WGA-streptavidin gold...

Primary radiotherapy in progressive optic nerve sheath meningiomas: a long-term follow-up study

Saeed, P.; Blank, L.; Selva-Nayagam, D.; Wolbers, J.; Nowak, P.; Geskus, R.; Weis, E.; Mourits, M.; Rootman, J.
Fonte: British Med Journal Publ Group Publicador: British Med Journal Publ Group
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
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Background/aims: To report the outcome of primary radiotherapy in patients with progressive optic nerve sheath meningioma (ONSM). Methods: The clinical records of all patients were reviewed in a retrospective, observational, multicentre study. Results: Thirty-four consecutive patients were included. Twenty-six women and eight men received conventional or stereotactic fractionated radiotherapy, and were followed for a median 58 (range 51–156) months. Fourteen eyes (41%) showed improved visual acuity of at least two lines on the Snellen chart. In 17 (50%) eyes, the vision stabilised, while deterioration was noted in three eyes (9%). The visual outcome was not associated with age at the time of radiotherapy (p=0.83), sex (p=0.43), visual acuity at the time of presentation (p=0.22) or type of radiotherapy (p=0.35). Optic disc swelling was associated with improved visual acuity (p<0.01) and 4/11 patients with optic atrophy also showed improvement. Long-term complications were dry eyes in five patients, cataracts in three, and mild radiation retinopathy in four. Conclusion: Primary radiotherapy for patients with ONSM is associated with long-term improvement of visual acuity and few adverse effects.; Peerooz Saeed, Leo Blank, Dinesh Selva...

Sterotaktische, fraktionierte Strahlentherapie bei Patienten mit Optikusscheidenmeningeomen und Keilbeinmeningeomen; Stereotactic fractionated radiotherapy in patients with optic nerve sheath meningioma and sphenoid wing meningioma

Dörr, Stefan
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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Das OSM ist ein seltener, gutartiger Tumor der Sehnervenscheide, dessen klinisches Bild durch langsamen, progredienten Visusverlust und Gesichtsfeldeinschränkungen geprägt ist. Neben klinischer Beobachtung und Operation steht seit einigen Jahren auch die Strahlentherapie zur Verfügung. Wir zeigen die Ergebnisse eines dreistelligen Patientenkollektivs, das zwischen 1993 und 2005 eine SFRT in Tübingen erhielt und vergleichen die Ergebnisse mit älteren Studien ähnlichen Konzepts, sowie mit den Ergebnissen anderer Therapieoptionen. KBM wurden auf Grund der Ähnlichkeit des Bestrahlungsgebietes ebenfalls aufgenommen. Methode: Identifikation der Studienpopulation mittels einer Suchfunktion in der elektronischen Arztbriefschreibung. Einschlusskriterium war ein Meningeom des Nervus opticus oder des Keilbeins. Sodann Durchsicht der Patientenakten und Erfassung der Daten zum prätherapeutischen Stand, zur Behandlung selbst und zur Nachbeobachtung. Die Darstel-lung der Daten erfolgte deskriptiv. Wo sinnvoll, erfolgte eine Signifikanzprüfung mit dem zweiseitigen t-Test bzw. dem log-Rang-Test. Ergebnisse: 118 Patienten, 31 % mit einem primärem, 64 % mit einem sekundären OSM, sowie 5 % mit einem KBM erhielten zwischen Juli 1993 und März 2005 eine SFRT. 83 % der Patienten waren weiblich. Das mediane Erkrankungsalter betrug 51...

Photoinduced magneto-optic Kerr effects in asymmetric semiconductor microcavities

Pereda Cubián, David; Haddad, Mustapha; André, Régis; Frey, Robert; Roosen, Gérald; Arce Diego, José Luis; Flytzanis, Christos
Fonte: American Physical Society Publicador: American Physical Society
Tipo: info:eu-repo/semantics/article; publishedVersion
ENG
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Giant photoinduced magneto-optic Kerr effects are predicted and measured in asymmetric semiconductor microcavities with a totally reflecting rear mirror operated in the limit of the strong coupling regime. Themicrocavity is modeled by two coupled Fabry-Perot cavities and use is made of the optical scattering matrices to derive its characteristics. The giant photoinduced rotations and phase changes are traced to the saturation, blueshift, and pseudo-Zeeman splitting of the exciton transition. Modeling the lower and upper polariton transitions by two different two-level systems qualitatively accounts for the main spectral features: the photoinduced Kerr rotations and phase changes are due to the modifications of the coupling existing between the cavity and exciton modes, due to the photoinduced changes of the exciton characteristics. The influence of spin relaxation on the rotation and ellipticity spectra is also analyzed; it confirms the gyrotropic nature of the interaction which depends strongly on the difference between the densities of counter-rotating circularly polarized excitons and only weakly on their sum as is the case in previous isotropic studies. Measurements of photoinduced Kerr rotations performed at a temperature of 50 K in a microcavity containing a single semimagnetic semiconductor quantum well confirm the effectiveness of the effect with polarization rotations of 10° around the lower polariton frequency at a pump fluence of only 2 μJ/cm2.

Aspects of retinal and optic nerve pathology after excitotoxic retinal injury.

Saggu, Sarabjit Kaur
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2011
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35.75%
A large body of evidence supports the notion that excitotoxicity plays a major role in the pathogenesis of a number of neurological diseases, including central nervous system (CNS) ischaemia, Alzheimer's disease, motor neurone disease, and glaucoma. In the global population 60 years of age and over, these diseases are among the leading causes of mortality and morbidity. Although the site of excitotoxic injury is principally at the level of the cell body (perikaryal), understanding the secondary effects on the neuronal axon is important because axonopathy is a documented early feature of these common neurological conditions; hence, an understanding of the pattern and mechanisms of secondary axonal degeneration after excitotoxic perikaryal injury could provide novel detection and treatment strategies in the early phase of neurological disease. The retina and optic nerve, as approachable regions of the CNS, provide a unique anatomical substrate to investigate axonal degeneration after perikaryal excitotoxic injury. Spatiotemporal changes in the retina and optic nerve were studied after injection of 20nM of Nmethyl-D-Aspartate (NMDA) in the left eye of the rat with the saline-injected right eye serving as the control. Temporal changes in the morphology of retina and optic nerve were studied by light and electron microscopy. Progressive retinal damage beginning at 72 hrs...

Thermal Effects on Monitoring and Performance of Reinforced Concrete Structures

DeRosa, DANIELLE
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
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35.64%
Much of North America’s reinforced concrete infrastructure is reaching the end of its service life and careful inspection and assessment is required to ensure the appropriate capacity is maintained in these structures. The research conducted herein seeks to further the development of two new sensor technologies: fibre optic strain sensors and digital image correlation, which have the potential to provide comprehensive performance data for structures to a level of accuracy previously not possible. The research involves determining the accuracy of these sensor systems to monitor both strain and crack widths in reinforced concrete compared to conventional techniques, such as electrical resistance strain gauges. Preliminary work was also undertaken on correcting the sensor results for temperature. It was determined that temperature variations in the range of +21 °C to 20 °C, result in significant strain errors for both sensor systems. Once the results obtained from the sensors systems are corrected for temperature, crack widths are monitored in four small-scale reinforced concrete tension specimens, and strain and crack width behaviour is monitored in four full-scale beams under four point bending. One of the major problems faced when using the digital image correlation technique is out of plane movement which results in significant error. Techniques to lower this error are addressed. In addition...

Distributed Fibre Optic Strain Sensing to Monitor Deterioration in Reinforced Concrete

Davis, Matthew
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
35.71%
Structural health monitoring (SHM) is an increasingly useful tool for life cycle management of deteriorating infrastructure. Rayleigh backscatter distributed fibre optic strain sensing (FOS) is a promising measurement technology that can provide relevant quantitative data across an entire structure as opposed to the single point data acquisition of conventional strain sensors. Utilizing this FOS technology, an experimental investigation to measure and better understand the effects of deterioration on reinforced concrete behaviour was undertaken. Reinforced concrete tension specimens were instrumented with optical fibres and tested in axial tension to determine if FOS is capable of measuring the effects of tension stiffening and to develop insights into the bond performance of reinforced concrete. It was found that FOS could be used to measure the distributed reinforcement strain, especially before cracking occurs, and these results illustrate how the bond deteriorates with increasing load. In addition, FOS can detect crack locations as well as when cracks develop on only one side of the specimen. The FOS technology was utilized to detect and quantify corrosion levels of the reinforcing steel and to determine how corrosion affects bond performance. An impressed current accelerated corrosion technique was used to corrode additional reinforced concrete tension specimens. Test results showed that reinforced concrete specimens that were corroded to 13% mass loss had a decrease in ultimate capacity of over 30%. This was due to pitting corrosion of the reinforcement that the FOS was able to detect. Additionally...

The monitoring of an existing cast iron tunnel with distributed fibre optic sensing (DFOS)

Gue, C. Y.; Wilcock, M.; Alhaddad, M. M.; Elshafie, M. Z. E. B.; Soga, K.; Mair, R. J.
Fonte: Springer Publicador: Springer
Tipo: Article; published version
EN
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This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s13349-015-0109-8; Instrumentation is vital to tunnelling projects for validation of design assumptions, monitoring of trigger levels during construction and also serving as a feedback loop to understand the deformation mechanisms of the particular problem which could be used to improve future designs. It can also be used for long term monitoring of the tunnel for maintenance purposes. Distributed fibre optic sensing (DFOS) systems based on brillouin optical time domain reflectometry are able to provide continuous and distributed strain measurements to be taken along the entire length of, for example, an existing cast iron tunnel where the fibre optic cable length is fully attached. This enables engineers to understand the stresses and strains that develop within the lining caused by external influences; which in this case, the construction of a new tunnel directly underneath it, rather than relying on discrete point measurements of displacement from conventional methods of monitoring. Nonetheless, proper installation of DFOS is of paramount importance to obtain high quality data. This paper aims to provide some practical guidance on the planning and installation of DFOS and presents a brief case study on the monitoring of London?s Royal Mail tunnel during the construction of the large Crossrail platform tunnel...

Application of optical system simulation software in a fiber optic telecommunications program

Koontz, Warren; Mandloi, Divya
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Conferência ou Objeto de Conferência Formato: 670847 bytes; application/pdf
EN_US
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One of our objectives in the College of Applied Science and Technology at RIT is to offer our students some kind of “hands-on” experience along with theory. Providing a hands-on experience can be costly, however, especially in the field of optical communication. Although reasonably priced laboratory kits are available, the optical-electronic components in these kits are well below communication grade. Thus if we rely only on hardware, our students can only experiment with low power, low bit rate communication over a few kilometers of fiber. Computer simulation software offers an affordable alternative “hands-on” experience. With this software, a student can create a model of an optical system, execute the model and view measures of the system’s performance. The system components can include DFB laser diodes, high-speed modulators, hundreds of kilometers of fiber, APD receivers and other optical and electrical components. The student can view the optical signals in the time or frequency domain, measure optical power and signal-to-noise ratio and much more. He or she can also view the effects of parameter variations or find the optimal value of a parameter. The software is easy to learn, especially if the student has previous experience with an electronic system simulator. This paper describes our application of an optical-electronic system simulator in the Telecommunications Engineering Technology program at RIT. We are developing a series of exercises to complement courses in fiber optic. These exercises will allow students to model and test systems that they have designed. We expect computer simulation to enhance our fiber optic courses significantly by adding a reasonably realistic and accessible test bed for student designs.; Paper presented at Photonics North in Ottawa in September 2004

A self-locked magneto-optic trap

Fletcher, C; Lye, J; Robins, Nicholas; Close, John
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
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We present a novel technique to lock the frequency of the trapping laser of a magneto-optic trap (MOT) using a signal generated from the ultracold atoms in the MOT itself. This technique utilizes the large number of very cold, slow-moving atoms in the MOT to generate a signal free of Doppler-broadening. A system analogous to Pound-Drever-Hall locking allows an error signal to be generated on resonance without significantly perturbing the MOT. We have successfully stabilized the frequency of the main trapping laser of a 87Rb MOT using this technique to generate a self-locked MOT.