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In this paper, we present the results of an experimental study on the characterization of holmium-doped silica fiber. A standard acousto-optic modulator controls the output power of the ytterbium-doped fiber laser operating at 1134.5 nm and serving as a pump source of the holmium-doped fiber under test. This technique allows us to measure the lifetimes of 5I7 and 5I8 energy levels of Ho3+ ions. The effects of the fiber length and the concentration-dependent pair-induced quenching on the accuracy of the fluorescence lifetime measurement are considered. The results of this study are compared with those obtained using the exponential and Förster decay functions used for such types of measurements. It is demonstrated that the knowledge of two fiber parameters, the pump saturation power and the fluorescence saturation power, together with the fiber absorption spectrum, permits one to obtain the absorption cross-sections at the pump and other key wavelengths, the effective concentration of the active ions, and the quantum efficiency of the fluorescence from the laser level. The results of this study are applicable to the reliable characterization of any type of heavily doped gain fibers and to the further numerical modeling and optimization of fiber lasers. [ABSTRACT FROM AUTHOR]

Giant cell tumors of bone are a rare entity, usually occurring in young patients and characteristically arising in the long bones. The spinal location is rare and usually presents with pain and/or neurological symptoms. The treatment of choice is surgery. Treatment with Denosumab, a bisphosphonate inhibitor of RANK-L, which is highly expressed in these tumors, has shown extensive activity in unresectable patients or those undergoing incomplete surgery. Preoperative treatment with this drug is gaining increasing interest, as its high potency in tumor reduction in this subtype of neoplasm has allowed resectability in selected patients. We present the case of a young patient with a large spinal tumor who, after neoadjuvant Denosumab, underwent complete en bloc surgery with clean margins and a great pathological response. [ABSTRACT FROM AUTHOR]

This paper proposes three-dimensional (3D) additive fabrication of synthetic core plugs for core flooding experiments from spheres and grains of Berea Sandstone using a digital particle packing approach. Samples were generated by systematically combining the main textural parameters of the rock reservoir to design synthetic core plugs Numerical flow simulation was per-formed using the lattice Boltzmann method (LBM) to verify the flow distribution and permeability for comparison with the experimentally measured permeability and to that obtained from correlations in the literature. The digital porosity of the sample was compared to the porosity measured using an HEP-P helium porosimeter. The numerical and experimental results for permeability and porosity differed by a maximum of 18%. [ABSTRACT FROM AUTHOR]

In-fiber opto-mechanics based on forward Brillouin scattering has received increasing attention because it enables sensing the surrounding of the optical fiber. Optical fiber transverse acoustic resonances are sensitive to both the inner properties of the optical fiber and the external medium. A particularly efficient pump and probe technique—assisted by a fiber grating—can be exploited for the development of point sensors of only a few centimeters in length. When measuring the acoustic resonances, this technique provides the narrowest reported linewidths and a signal-to-noise ratio better than 40 dB. The longitudinal and transverse acoustic velocities—normalized with the fiber radius—can be determined with a relative error lower than 10−4, exploiting the derivation of accurate asymptotic expressions for the resonant frequencies. Using this technique, the Poisson's ratio of an optical fiber and its temperature dependence have been measured, reducing the relative error by a factor of 100 with respect to previously reported values. Using a single-point sensor, discriminative measurements of strain and temperature can be performed, achieving detection limits of ±25 με and ±0.2 °C. These results show the potential of this approach for the development of point sensors, which can be easily wavelength-multiplexed. [ABSTRACT FROM AUTHOR]

We report an easy-to-build, compact, and low-cost optical fiber refractive index sensor. It consists of a single fiber loop whose transmission spectra exhibit a series of notches produced by the resonant coupling between the fundamental mode and the cladding modes in a uniformly bent fiber. The wavelength of the notches, distributed in a wavelength span from 1,400 to 1,700 nm, can be tuned by adjusting the diameter of the fiber loop and are sensitive to refractive index changes of the external medium. Sensitivities of 170 and 800 nm per refractive index unit for water solutions and for the refractive index interval 1.40-1.442, respectively, are demonstrated. We estimate a long range resolution of 3 x 10-4 and a short range resolution of 2 x 10-5 for water solutions. [ABSTRACT FROM AUTHOR]

Simple Summary: After the first wave of COVID-19, the Spanish Society of Thoracic Surgeons (SECT) surveyed its members to assess the impact of the pandemic on thoracic oncology surgery in one of the counties most affected by the virus. In May 2020, all SECT members were invited to complete a 40-item, multiple choice questionnaire by e-mail. The response rate was 19.0%. Surgical activity decreased by 95.7%, with 41.5% of centers performing surgery only in oncologic cases and 11.7% only in emergencies. More than half (56%) of multidisciplinary tumour board meetings (56%) were cancelled or conducted online. Standard protocols for early-stage disease were modified in 62.9% of centers. The results of this survey show that the COVID-19 pandemic severely limited thoracic oncology surgery activity. Here we describe and discuss the impact of the pandemic on thoracic surgery in Spain. After the first wave of COVID-19, the Spanish Society of Thoracic Surgeons (SECT) surveyed its members to assess the impact of the pandemic on thoracic oncology surgery in Spain. In May 2020, all SECT members were invited to complete an online, 40-item, multiple choice questionnaire. The questionnaire was developed by the SECT Scientific Committee and sent via email. The overall response rate was 19.2%. The respondents answered at least 91.5% of the items, with only one exception (a question about residents). Most respondents (89.3%) worked in public hospitals. The reported impact of the pandemic on routine clinical activity was considered extreme or severe by 75.5% of respondents (25.5% and 50%, respectively). Multidisciplinary tumour boards were held either with fewer members attending or through electronic platforms (44.6% and 35.9%, respectively). Surgical activity decreased by 95.7%, with 41.5% of centers performing surgery only on oncological patients and 11.7% only in emergencies. Nearly 60% of respondents reported modifying standard protocols for early-stage cancer and in the preoperative workup. Most centers (≈80%) reported using full personal protective equipment when operating on COVID-19 positive patients. The COVID-19 pandemic severely affected thoracic oncology surgery in Spain. The lack of common protocols led to a variable care delivery to lung cancer patients. [ABSTRACT FROM AUTHOR]

In the present paper, we show the experimental measurement of the growth of a microbubble created on the tip of a single mode optical fiber, in which zinc nanoparticles were photodeposited on its core by using a single laser source to carry out both the generation of the microbubble by photothermal effect and the monitoring of the microbubble diameter. The photodeposition technique, as well as the formation of the microbubble, was carried out by using a single-mode pigtailed laser diode with emission at a wavelength of 658 nm. The microbubble's growth was analyzed in the time domain by the analysis of the Fabry–Perot cavity, whose diameter was calculated with the number of interference fringes visualized in an oscilloscope. The results obtained with this technique were compared with images obtained from a CCD camera, in order to verify the diameter of the microbubble. Therefore, by counting the interference fringes, it was possible to quantify the temporal evolution of the microbubble. As a practical demonstration, we proposed a vibrometer sensor using microbubbles with sizes of 83 and 175 µm as a Fabry–Perot cavity; through the time period of a full oscillation cycle of an interferogram observed in the oscilloscope, it was possible to know the frequency vibration (500 and 1500 Hz) for a cuvette where the microbubble was created. [ABSTRACT FROM AUTHOR]

In-fiber opto-mechanics based on forward Brillouin scattering has received increasing attention because it enables sensing the surrounding of the optical fiber. Optical fiber transverse acoustic resonances are sensitive to both the inner properties of the optical fiber and the external medium. A particularly efficient pump and probe technique-assisted by a fiber grating-can be exploited for the development of point sensors of only a few centimeters in length. When measuring the acoustic resonances, this technique provides the narrowest reported linewidths and a signal-to-noise ratio better than 40 dB. The longitudinal and transverse acoustic velocities-normalized with the fiber radius-can be determined with a relative error lower than 10 -4 , exploiting the derivation of accurate asymptotic expressions for the resonant frequencies. Using this technique, the Poisson's ratio of an optical fiber and its temperature dependence have been measured, reducing the relative error by a factor of 100 with respect to previously reported values. Using a single-point sensor, discriminative measurements of strain and temperature can be performed, achieving detection limits of ±25 με and ±0.2 °C. These results show the potential of this approach for the development of point sensors, which can be easily wavelength-multiplexed.