Performance analysis of a noncontact plastic fiber optical fiber displacement sensor with compensation of target reflectivity

peer-reviewedAn inexpensive fiber-based noncontact distance sensor specific for monitoring short-range displacements in micromachining applications is presented. To keep the overall costs low, the sensor uses plastic optical fibers and an intensiometric approach based on the received light intensity after the reflection from the target whose displacement has to be measured. A suitable target reflectivity compensation technique is implemented to mitigate the effects due to target surface nonuniformity or ageing.The performances of the sensor are first evaluated for different fiber configurations and target reflectivity profiles and positions using a numerical method based on Monte Carlo simulations. Then, experimental validations on a configuration designed to work up to 1.5mm have been conducted. The results have confirmed the validity of the proposed sensor architecture, which demonstrated excellent compensation capabilities, with errors below 0.04mm in the (0-1)mm range regardless the color and misalignment of the target

Towards inline spatially resolved temperature sensing in thermal ablation with chirped fiber Bragg grating

We investigate the theory and feasibility of an in-line spatially resolved temperature sensor, suitable for thermal ablation monitoring. The sensor is based o a chirped fiber Bragg grating (CFBG). The CFBG is modelled as a chain of Bragg gratings, each sensitive to local temperature variations. By using a combination of iterative and statistical optimization techniques, it is possible to use demodulate the CFBG, in case of a Gaussian-like spatial temperature profile. A feasibility test based on CFBG simulation shows that the CFBG returns error <1 mm on cells damage threshold spatial estimation and good noise resilience

Ionizing radiation profiling through the induced refractive index change in backscattering-enhanced optical fibers

Enhanced Rayleigh backscattering optical fibers, interrogated by an optical frequency domain reflectometer, are used to perform remote real-time measurements of X-ray irradiation profiles, with possible application as dosimeters in radiotherapy treatments. The enhanced Rayleigh backscattering is obtained by proper engineering of the composition of fiber core, either by introduction of Aluminum or Magnesium silicate nanoparticles as radiation-sensitive dopants. A detectable radiation-induced refractive index change can be spatially resolved through the measurement of the frequency shift of the Rayleigh backscattering along the fiber. It is experimentally demonstrated that two mechanisms of radiation-induced refractive index change take place. At doses nearly compatible with those delivered in radiotherapy, a negative refractive index is induced, whereas at high doses the change is positive. This behavior is also confirmed by the shift of Bragg wavelength of a fiber Bragg grating inscribed in the nanoparticles-doped fiber and used as a reference

Linearly chirped fiber Bragg grating response to thermal gradient: from bench tests to the real-time assessment during in vivo laser ablations of biological tissue

The response of a fiber optic sensor [linearly chirped fiber Bragg grating (LCFBG)] to a linear thermal gradient applied on its sensing length (i.e., 1.5 cm) has been investigated. After these bench tests, we assessed their feasibility for temperature monitoring during thermal tumor treatment. In particular, we performed experi- ments during ex vivo laser ablation (LA) in pig liver and in vivo thermal ablation in animal models (pigs). We investigated the following: (i) the relationship between the full width at half maximum of the LCFBG spectrum and the temperature difference among the extremities of the LCFBG and (ii) the relationship between the mean spectrum wavelength and the mean temperature acting on the LCFBG sensing area. These relationships showed a linear trend during both bench tests and LA in animal models. Thermal sensitivity was significant although different values were found with regards to bench tests and animal experiments. The linear trend and significant sensitivity allow hypothesizing a future use of this kind of sensor to monitor both temperature gradient and mean temperature within a tissue undergoing thermal treatment

Distributed X-ray dosimetry with optical fibers by Optical Frequency Domain Interferometry

This article reports on the first demonstration of in situ, real-time dosimetry realized with an enhanced backscatttering optical fiber, and a high resolution optical backscattering reflectometry measurement. This work is devised to overcome the current problems in monitoring radiotherapy treatments, in particular, the difficult evaluation of not only the actual X-ray dose that is accumulated on the target volume but also the distribution profile of the ionizing radiation beam. Overall, the research aims at developing a dose sensor with the most demanding features of small form factor, spatial profiling, and remote interrogation. The experiments have been conducted by evaluating the spatial profile of radiation-induced spectral shift of the Rayleigh backscattering along an optical fiber exposed to X-rays. The sensing element is a section of specialty optical fiber whose Rayleigh backscattering signature changes under ionizing radiation. The specialty fiber is designed to exhibit an enhanced backscattering, in order to overcome the poor sensitivity to radiation of standard optical fibers that are normally, used in telecommunications. The enhanced sensitivity is achieved by doping the core with either aluminum or magnesium nanoparticles, and two different fibers have been fabricated and tested. The experimental results show the capability of real time detection of the radiation profile from high-dose rates (700 Gy/min) to low-dose rates (2 Gy/min). Moreover, different sensing mechanisms and responses to high- and low-dose rates are evidenced. A comparison with a quasi-distributed sensing system based on an array of fiber Bragg gratings (FBGs) is discussed, highlighting the superior performance of the backscattering approach in terms of sensitivity and spatial resolution, whereas the array of FBGs exhibits an advantage in terms of sampling speed

Effect of Dentin Biomodification Delivered by Experimental Acidic and Neutral Primers on Resin Adhesion

Objectives Proanthocyanidins (PACs) are biocompounds mimicking native collagen cross-links. The effective and practical delivery of any biocompound is pivotal for clinical usage. The aim was to investigate the dentin biomodification and effective formation of dentin–resin biointerfaces of two highly bioactive PAC-rich extracts, Vitis vinifera (Vv) and Camellia sinensis (Cs), delivered using neutral (NP) or acidic (AP) rinse-out primer approaches. Methods The depth of dentin demineralization (optical profilometry), dentin biomodification (apparent modulus of elasticity, collagen auto-fluorescence) and properties of dentin–resin interfaces (microtensile bond strength - μTBS, and micro-permeability) were investigated. NP consisted of either 15% Vv or Cs applied for 60 s after surface etching; while AP contained 15% Vv or Cs in either 35% glycolic acid or tartaric acid applied for 30 s or 60 s. Data were analyzed using ANOVA and post-hoc tests (α = 0.05). Results The depth of demineralization was statistically higher when applied for 60 s, regardless of rinse-out primer approach (p \u3c 0.001). Compared to the AP strategy, NP exhibited statistically higher apparent modulus of elasticity, regardless of PAC extract (p \u3c 0.001). Highest μTBS were obtained for NPVv, which were statistically similar to APGAVv, when applied for 60 s (p \u3c 0.001); both resulted in a dramatic decrease of the interfacial permeability. NPCs group showed the lowest μTBS (p \u3c 0.001). Conclusions A combination of high bond strength and low micro-permeability can be accomplished using glycolic acid with the mid- and high-PAC oligomer enriched extract (Vv). Cs extract containing mostly catechins and dimeric PACs, was found unsuitable for resin-dentin adhesion despite exhibiting high initial dentin biomodification. Clinical significance This study provides a new conceptual delivery of PAC-mediated dentin biomodification and conservative dentin surface etching using rinse-out primers. The strategy requires a specific combination of PAC source, α-hydroxy acid, and application time

Estimación de Resultados Económicos de Cultivos de Verano - Campaña 2020/21

En este artículo se realiza una evaluación económica de los cultivos estivales teniendo en cuenta la combinación de actividades y modalidades de producción de un sistema con un uso del suelo predominantemente agrícola. El territorio considerado es el Mar y Sierras, que comprende los partidos de Tandil, Balcarce, Lobería y Necochea, formando parte de la Zona Agroeconómica Mixta del Centro Sur.EEA BalcarceFil: Guido, Sergio Ricardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; Argentina.Fil: Guido, Sergio Ricardo. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentina.Fil: Urcola, Hernán Alejandro. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; Argentina.Fil: Natinzon, Paula Carina. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; Argentina.Fil: Tosi, Juan Carlos. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Balcarce; Argentina

Preliminary investigation of radiation dose sensors based on aluminum-doped silicate optical fibers

The paper reports on the first demonstration of in-situ, real-time dosimetry realized with an enhanced back-scattering optical fiber and a high-resolution optical back-scattering reflectometry measurement. This work is devised to overcome the current problems in monitoring radiotherapy treatments, in particular the difficult evaluation of not only the actual x-ray dose that is accumulated on the target volume, but also the distribution profile of the ionizing radiation beam. The experiments have been conducted by evaluating the radiation-induced spectral shift of the Rayleigh back-scattering along the fiber under test during x-ray exposure, in a radiation chamber. The sensing region is a section of aluminum-doped silicate fiber, that overcomes the poor sensitivity to radiation of standard, germanium-doped, silicate fibers for telecom applications. The preliminary results show that it is possible to remotely track the x-ray dose at high dose rates (700 Gy/min) and at rates closer to therapeutic values (22 Gy/min). A linear relationship between accumulated dose and spectral shift has been found. This research aims at developing a dose sensor with the most demanding features of small form factor, spatial profiling and remote interrogation