CAP - Indexed Articles in Journals

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    250 km ultra long sensor system based on a Fiber Loop Mirror interrogated by an OTDR
    ( 2011) M. Lopez-Amo ; José Manuel Baptista ; José Luís Santos ; Orlando Frazão ; M. Bravo
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    300 km-Ultralong Raman Fiber Lasers using a Distributed Mirror for Sensing Applications
    ( 2011) Manuel Joaquim Marques ; Hugo Fidalgo Martins ; Orlando Frazão
    H. Martins, M. B. Marques, O. Frazão, 300 km-Ultralong Raman Fiber Lasers using a Distributed Mirror for Sensing Applications, Opt. Express, 19 (19), 18149-18154, September 2011.
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    Absorption-line-locked fiber laser for gas-sensing applications
    ( 2007) Nome Apelido ; Francisco Araújo ; Luís Alberto Ferreira
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    Acetone evaporation and water vapor detection using a caterpillar-like microstructured fiber
    ( 2016) André Delgado Gomes ; Ferreira,MFS ; Moura,JP ; Ricardo Melo André ; Kobelke,J ; Bierlich,J ; Wondraczek,K ; Schuster,K ; Orlando Frazão
    A new microstructured optical fiber is presented as a sensor of acetone evaporation. Sensing is performed by observing the time response of the reflected signal at 1550 nm when the device is dipped in acetone or a 50% acetone-50% water mixture. The sensor consists on a caterpillar-like microstructured fiber spliced to a single-mode fiber, where the spliced end of the sensor has a transversal microfluidic channel etched using focused ion beam. Upon heating, different behaviors are visible between the dipping and the evaporation of acetone. The sensor is able to track the evaporation of acetone and to distinguish between pure acetone and a 50% acetone-50% water mixture. The sensor is also able to detect when the acetone in a mixture with water is fully evaporated. The detection of water vapor with no particular orientation of the sensor is achieved due to the presence of the microfluidic channels. (c) 2016 Wiley Periodicals, Inc.
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    Acoustic Optical Fiber Sensor Based on Graphene Oxide Membrane
    ( 2021) Catarina Silva Monteiro ; Raposo,M ; Ribeiro,PA ; Susana Oliveira Silva ; Orlando Frazão ; 4061 ; 4678 ; 6568
    A Fabry–Pérot acoustic sensor based on a graphene oxide membrane was developed with the aim to achieve a faster and simpler fabrication procedure when compared to similar graphene-based acoustic sensors. In addition, the proposed sensor was fabricated using methods that reduce chemical hazards and environmental impacts. The developed sensor, with an optical cavity of around 246 µm, showed a constant reflected signal amplitude of 6.8 ± 0.1 dB for 100 nm wavelength range. The sensor attained a wideband operation range between 20 and 100 kHz, with a maximum signal-to-noise ratio (SNR) of 32.7 dB at 25 kHz. The stability and sensitivity to temperatures up to 90 °C was also studied. Moreover, the proposed sensor offers the possibility to be applied as a wideband microphone or to be applied in more complex systems for structural analysis or imaging.
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    Active Illumination Single-Pixel Camera Based on Compressive Sensing
    ( 2011) Mehrdad Abolbashari ; Francisco Araújo ; Miguel Velhote Correia ; Faramarz Farahi ; Filipe Tiago Magalhães
    In this paper an optical imaging system based on compressive sensing (CS) is presented along with its principal mathematical aspects. Although CS is undergoing significant advances and empowering many discussions and applications throughout various fields, this article focus on the analysis of a single-pixel camera. This work was the core for the development of a single-pixel camera approach based on active illumination. Therefore, the active illumination concept is described along with experimental results, which were OSA Published by 2 very encouraging towards the development of compressive sensing based cameras for various applications, such as pixel level programmable gain imaging.
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    Addressing the Fabrication Difficulties of Femtosecond Laser Written Surface Waveguides for Enhanced Evanescent Coupling
    ( 2019) Vítor Oliveira Amorim ; João Miguel Maia ; Viveiros,D ; Marques,PVS ; 6407 ; 6596
    In this work, the fabrication of optical waveguides embedded in fused silica (Suprasil1) and boro-aluminosilicate glass (Eagle2000) is demonstrated with femtosecond laser direct writing, as well as their suitability to be brought to the surface, through wet etching, for enhanced evanescent coupling with the external dielectric medium. Fused silica demonstrated to be inappropriate in this particular application, as the guiding region is at the bottom of the induced modification, creating a barrier between the guided mode and the substrate’s boundary. Furthermore, the existence of nanogratings meant that, upon contact of the top of the induced modification with the substrate’s boundary, the waveguide is quickly etched. Eagle2000 demonstrated to be superior to fused silica due to its characteristic modification cross-section and absence of nanogratings, which allowed the placement of the guiding region as close to the substrate’s surface as required. However, surface roughness arising from the creation of insoluble products in the HF solution was found. The addition of HCl to dissolve these products was implemented.
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    All fiber Mach-Zehnder interferometer based on suspended twin-core fiber
    ( 2010) Orlando Frazão ; J. Kobelke ; K. Schuster ; Susana Oliveira Silva ; José Luís Santos ; José Manuel Baptista
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    An all-fiber Fabry-Perot interferometer for pressure sensing in different gaseous environments
    ( 2014) Susana Oliveira Silva ; Luís Carlos Coelho ; Orlando Frazão
    A gas pressure sensor based on an all-fiber Fabry-Perot interferometer (FFPI) is reported. The sensing head consists of a small section of silica rod spliced with a large offset between two single-mode fibers. The silica rod is used only as mechanical support so that an air cavity can be formed between both SMF. It is shown that the FFPI sensor is sensitive to gas pressure variation and when submitted to different gaseous environments, namely carbon dioxide, nitrogen and oxygen - sensitivities of 6.2, 4.1 and 3.6 nm/MPa, respectively, were attained. The refractive index change on nitrogen environment by means of gas pressure variation was also determined and a sensitivity of 1526 nm/RIU was obtained. The response of the sensing device to temperature variations in air was also studied and a sensitivity of -14 pm/degrees C was attained.
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    Analysis of Phase Interrogated SPR Fiber Optic Sensors With Bimetallic Layers
    ( 2014) Hamed Moayyed ; Leite,IT ; Luís Carlos Coelho ; José Luís Santos ; Diana Viegas
    An effective analytical model combining geometrical optics with the transfer-matrix theory for stratified optical media is applied to investigate the sensing properties of tapered optical fiber surface plasmon resonance (SPR) sensors incorporating Ag-Au bimetallic layers, particularly in the context of phase interrogation. The performance of the sensing structures is studied as a function of the tapering parameters and thickness of the metallic layers. It is shown that the Ag-Au bimetallic combination is capable of improving the resolution and tuning working region of SPR fiber-optic sensors and that by tapering the sensing structures enhanced sensitivity can be achieved when phase interrogation is considered.
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    Antimicrobial effect of essential oils of Laurus nobilis L. and Rosmarinus officinallis L. on shelf-life of minced "Maronesa" beef stored under different packaging conditions
    ( 2016) Vilela,J ; Martins,D ; Filipe Monteiro Silva ; Gerardo Aguilar ; José Almeida ; Saraiva,C
    The aim of this study was to evaluate the effect of essential oils (EOs) of plants naturally occurring in northern Portugal on the spoilage of fresh Maronesa beef burgers stored at 2 and 8 degrees C under different packaging conditions. EOs were obtained from dried leaves of laurel (Laurus Nobilis L.) and rosemary (Rosmarinus officinallis L.) by hydro-distillation using a Clevenger-type apparatus. Analysis of volatile composition of essential oils of rosemary and laurel was achieved by Gas Chromatography-Mass Spectrometry (GC-MS) and Gas Chromatography-Thermal Conductivity Detection (GC-TCD) resulting in the detection of 95.8% and 89.4% of its compounds, respectively. Fresh beef (semitendinosus and semimembranosus) of DOP-Maronesa breed (males; n = 4) were obtained from local market and transported to the laboratory. Samples were stored at 2 and 8 degrees C in two different conditions: aerobiosis (A) and vacuum (V) and analyzed at 0,1, 2, 3, 5, 7,10,14, 21 and 28 days for Lactic acid bacteria (LAB), Enterobacteriaceae, Pseudomonas spp., Fungi, Total mesophilic (TM) and psychrotrophic (TP), color (L*a*b*) and pH. Laurel was the most effective EO keeping pH from increasing. Coordinates L* and a* were higher on samples containing laurel EO for both A and V packaging. Laurel also showed better effect in reducing microbiologic counts in samples packed in A at both 2 and 8 degrees C and packed in V at 8 degrees C. Rosemary was effective in reducing microbial counts on all V samples stored at 2 degrees C. This study allows to conclude that Laurel EO has significant effect in shelf-life, maintaining fresh beef color.
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    Apodization of fiber Bragg gratings by using arc discharges
    ( 2008) Paulo Vicente Marques ; Gaspar Rego ; Rosa Romero
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    Application of a Fiber Optic Refractometric Sensor to Measure the Concentration of Paracetamol in Crystallization Experiments
    ( 2021) Liliana Patrícia Soares ; Cruz,P ; Susana Novais ; Ferreira,A ; Orlando Frazão ; Susana Oliveira Silva ; 4061 ; 4678 ; 7662 ; 7725
    A refractometric sensor was applied to measure in real-time the concentration of Active Pharmaceutical Ingredients (APIs) in crystallization experiments. Paracetamol was used as a model system due to the extensive literature available for this API. The refractometric sensor was fabricated by a simple and inexpensive method that consisted in splicing a short section of a multimode fiber to a single mode fiber. The compact geometry of this sensor, with an external diameter of just $125\ \mu\mathrm{m}$, allowed it to measure the concentration of paracetamol, both in a stirred tank crystallizer operating in batch and in an oscillatory flow crystallizer operating continuously. The proposed technique shows the potential to monitor the concentration of APIs in crystallizers of different sizes and geometries as an alternative to more expensive and complex analysis equipment.
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    Application of Glass Reinforced Hydroxyapatite Composite in the Treatment of Human Intrabony Periodontal Angular Defects - Two Case Reports
    ( 2010) M. A. Lopes ; P. Krishnanjaneya Reddy ; Nandyala Hussain ; J. D. Santos ; G. Pavan Kumar ; A. Jaya Kumar
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    Applications of quantum dots in optical fiber luminescent oxygen sensors
    ( 2006) Pedro Jorge ; Faramarz Farahi ; José Luís Santos ; Paulo Caldas ; M. Mayeh ; R. Benrashid
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    Aptamer-based fiber sensor for thrombin detection
    ( 2016) Luís Carlos Coelho ; José Almeida ; José Luís Santos ; Pedro Jorge ; Martins,MCL ; Diana Viegas ; Queiros,RB
    The detection of thrombin based on aptamer binding is studied using two different optical fiber-based configurations: long period gratings coated with a thin layer of titanium dioxide and surface plasmon resonance devices in optical fibers coated with a multilayer of gold and titanium dioxide. These structures are functionalized and the performance to detect thrombin in the range 10 to 100 nM is compared in transmission mode. The sensitivity to the surrounding refractive index (RI) of the plasmonic device is higher than 3100 nmRIU(-1) in the RI range 1.335 to 1.355, a factor of 20 greater than the sensitivity of the coated grating. The detection of 10 nM of thrombin was accomplished with a wavelength shift of 3.5 nm and a resolution of 0.54 nM. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)
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    Assessment of the osteoblastic cell response to a zinc glass reinforced hydroxyapatite composite (Zn-GRHA)
    ( 2009) M. A. Lopes ; P. S. Gomes ; M. H. Fernandes ; J. D. Santos ; Nandyala Hussain
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    à ndice de refração, esse desconhecido (parte I)
    ( 2016) Manuel Joaquim Marques ; Universidade do Porto,
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    à ndice de refração, esse desconhecido (parte II)
    ( 2016) Manuel Joaquim Marques ; Universidade do Porto,