Optical Fiber Sensors for Structural Monitoring in Power Transformers.

Power transformers are central elements of power transmission systems and their deterioration can lead to system failures, causing major disruptions in service. Catastrophic failures can occur, posing major environmental hazards due to fires, explosions, or oil spillage. Early fault detection can be accomplished or estimated using electrical sensors or a chemical analysis of oil or gas samples. Conventional methods are incapable of real-time measurements with a low electrical noise due to time-consuming analyses or susceptibility to electromagnetic interference. Optical fiber sensors, passive elements that are immune to electromagnetic noise, are capable of structural monitoring by being enclosed in power transformers. In this work, optical fiber sensors embedded in 3D printed structures are studied for vibration monitoring. The fiber sensor is encapsulated between two pressboard spacers, simulating the conditions inside the power transformer, and characterized for vibrations with frequencies between 10 and 800 Hz, with a constant acceleration of 10 m/s2. Thermal aging and electrical tests are also accomplished, aiming to study the oil compatibility of the 3D printed structure. The results reported in this work suggest that structural monitoring in power transformers can be achieved using optical fiber sensors, prospecting real-time monitoring.

Femtosecond laser micromachining of an optofluidics-based monolithic whispering-gallery mode resonator coupled to a suspended waveguide.

A monolithic lab-on-a-chip fabricated by femtosecond laser micromachining capable of label-free biosensing is reported. The device is entirely made of fused silica, and consists of a microdisk resonator integrated inside a microfluidic channel. Whispering gallery modes are excited by the evanescent field of a circular suspended waveguide, also incorporated within the channel. Thermal annealing is performed to decrease the surface roughness of the microstructures to a nanometric scale, thereby reducing intrinsic losses and maximizing the Q-factor. Further, thermally-induced morphing is used to position, with submicrometric precision, the suspended waveguide tangent to the microresonator to enhance the spatial overlap between the evanescent field of both optical modes. With this fabrication method and geometry, the alignment between the waveguide and the resonator is robust and guaranteed at all instances. A maximum sensitivity of 121.5 nm/RIU was obtained at a refractive index of 1.363, whereas near the refractive index range of water-based solutions the sensitivity is 40 nm/RIU. A high Q-factor of 105 is kept throughout the entire measurement range.

Effect of Low-Doses of Gamma Radiation on Electric Arc-Induced Long Period Fiber Gratings.

This work presents an experimental study on the effects of gamma radiation on Long Period Fiber Gratings (LPFGs) in a low-dose test campaign to evaluate their eventual degradation. The study was carried out with standard single-mode fibers where the grating was inscribed using the Electric-Arc Discharge (EAD) technique. Before the gamma campaign, a detailed optical characterization was performed with repeatability tests to verify the accuracy of the setup and the associated error sources. The gamma-induced changes up to a dose of 200 krad and the recovery after radiation were monitored with the Dip Wavelength Shift (DWS). The results show that the gamma sensitivity for a total dose of 200 krad is 11 pm/krad and a total DWS of 2.3 nm has been observed with no linear dependence. Post-radiation study shows that recovery from radiation-induced wavelength shift is nearly complete in about 4000 h. Experimental results show that the changes suffered under gamma irradiation of these LPFGs are temporary making them a good choice as sensors in space applications.

Temperature Stability and Spectral Tuning of Long Period Fiber Gratings Fabricated by Femtosecond Laser Direct Writing.

Long period fiber gratings (LPFGs) were fabricated in a standard single mode fiber (SMF-28e) through femtosecond (fs) laser direct writing. LPFGs with longer and shorter periods were fabricated, which allows coupling from the fundamental core mode to lower and higher order asymmetric cladding modes (LP1,6 and LP1,12, respectively). For the grating periods of 182.7 and 192.5 µm, it was verified that the LP1,12 mode exhibits a TAP at approximately 1380 and 1448 nm in air and water, respectively. Characterization of the LPFGs subjected to high-temperature thermal treatment was accomplished. Fine-tuning of the resonance band's position and thermal stability up to 600 °C was shown. The temperature sensitivity was characterized for the gratings with different periods and for different temperature ranges. A maximum sensitivity of -180.73, and 179.29 pm/°C was obtained for the two resonances of the 182.7 µm TAP LPFG, in the range between 250 and 600 °C.

Paraduodenal mass as initial presentation of burned-out testicular tumour: case report and literature review.

Testicular germ cell tumours (TGCTs) are relatively rare overall and are mainly encountered in young adults and teenagers. The 'burned-out' phenomenon refers to the spontaneous regression of the primary testicular lesion, generally with the presence of a metastatic germ cell tumour. Regressed tumours with retroperitoneal metastasis, as the first manifestation, represent difficult cases prone to misdiagnosis. Burned-out TGCT is a rare but well-recognized entity, with defined clinical features and diagnostic criteria; however, its etiopathogenesis is still not well defined.We present a case of 37-year-old man with a retroperitoneal mass adjacent to the duodenum identified on CT scan. After surgical excision, histopathologic findings evidenced metastatic non-seminomatous GCT. Testicular examination was normal, but a right testis suspicious lesion was found on ultrasound study. Radical right orchidectomy was performed, and histological examination showed complete regression of TGCT. He underwent first-line chemotherapy with complete response and no evidence of recurrence.

Femoral Hernia Containing the Right Fallopian Tube: A Rare Finding.

Femoral hernias comprise a small proportion of all groin hernias. They are more common in women and have a high rate of incarceration and strangulation, leading to emergency repair. A 61-year-old female patient was admitted to the emergency department complaining of a 2-day painful lump in the right groin, that had become more intense in the last 24 hours. Physical examination suggested the presence of a strangulated femoral hernia, and the patient underwent emergency surgical repair. Intraoperatively, the right fallopian tube was observed in the hernia sac. Since there were no signs of ischemia, the tube was reduced back into the pelvic cavity and the hernia was repaired. The postoperative period was uneventful, and the patient was discharged without complications, 3 days after surgery.

As hérnias femorais representam uma pequena fração de todas as hérnia da região inguinal. Elas são mais comuns entre as mulheres e estão associadas a elevadas taxas de complicações, como encarceramento e estrangulamento, com necessidade de cirurgia urgente. Uma paciente do sexo feminino, de 61 anos, recorreu ao serviço de emergência por quadro de dor e tumefação da região inguinal direita com 2 dias de evolução e agravamento nas últimas 24 horas. O exame objetivo sugeria a presença de uma hérnia femoral encarcerada, e a paciente foi submetida a cirurgia urgente. Intraoperatoriamente, confirmou-se o diagnóstico de hérnia femoral encarcerada, que continha a trompa de falópio direita no interior do saco herniário. Uma vez que a que a trompa não apresentava sinais de isquemia, o conteúdo da hérnia foi reduzido, e procedeu-se à sua reparação. O período pós-operatório decorreu sem intercorrências, e a paciente teve alta no 3° dia após a cirurgia.

Femoral hernia containing the right fallopian tube: a rare finding / Hérnia femoral contendo a trompa de falópio direita: um achado raro

Abstract Femoral hernias comprise a small proportion of all groin hernias. They are more common in women and have a high rate of incarceration and strangulation, leading to emergency repair. A 61-year-old female patient was admitted to the emergency department complaining of a 2-day painful lump in the right groin, that had become more intense in the last 24 hours. Physical examination suggested the presence of a strangulated femoral hernia, and the patient underwent emergency surgical repair. Intraoperatively, the right fallopian tube was observed in the hernia sac. Since there were no signs of ischemia, the tube was reduced back into the pelvic cavity and the hernia was repaired. The postoperative period was uneventful, and the patient was discharged without complications, 3 days after surgery.

Resumo As hérnias femorais representamuma pequena fração de todas as hérnia da região inguinal. Elas são mais comuns entre as mulheres e estão associadas a elevadas taxas de complicações, como encarceramento e estrangulamento, com necessidade de cirurgia urgente. Uma paciente do sexo feminino, de 61 anos, recorreu ao serviço de emergência por quadro de dor e tumefação da região inguinal direita com 2 dias de evolução e agravamento nas últimas 24 horas. O exame objetivo sugeria a presença de uma hérnia femoral encarcerada, e a paciente foi submetida a cirurgia urgente. Intraoperatoriamente, confirmou-se o diagnóstico de hérnia femoral encarcerada, que continha a trompa de falópio direita no interior do saco herniário. Uma vez que a que a trompa não apresentava sinais de isquemia, o conteúdo da hérnia foi reduzido, e procedeu-se à sua reparação. O período pós-operatório decorreu sem intercorrências, e a paciente teve alta no 3° dia após a cirurgia.