Search

Undersea earthquakes can have a major impact on coastal cities, submarine infrastructure and environment. To provide advance warning and condition assessment, remote monitoring is critical. However, the current methods of undersea earthquake monitoring have some limitations, such as limited number of sensors, high deployment cost, severe signal attenuation, etc. In this study, we propose a new approach for super-long range vibration monitoring, by detecting vibration-induced phase change along a single sensing fiber using a double-ended forward-transmission distributed fiber-optic vibration sensing system with a compensated self-interference sensing mechanism. The experiment results show a single-span sensing range of 151.5 km without optical amplification, a spatial resolution of 10 m, and the position error can be as small as 37.6 m. The average sensitivity is ∼12.2 mrad/μϵ, and the average limit of detection is 186.7 pϵ/Hz1/2. The vibration frequency range tested is between 100–500 Hz. The sensing system has several advantages, such as super-long sensing distance, relatively low-coherence laser, anti-electromagnetic interference, etc. This study provides a new technical solution for undersea earthquake monitoring, which can improve the early warning and assessment capabilities of undersea earthquakes.

Distributed fiber-optic sensors are widely used for mining safety monitoring, civil engineering structural health monitoring and environmental monitoring. The position accuracy of measurements is of critical concern, as errors can lead to expensive decisions at the wrong location. Accurate fiber length measurement is key to calibrate distributed fiber-optic sensors. Existing methods suffer from time resolution or component delay errors. Optical time-domain reflectometry (OTDR) and its variants are widely used but needs calibration for practical applications. We propose two new methods that can self-calibrate, and can be used to calibrate other methods such as those based on OTDR. One based on a differential pulse loop using dual pulse statistical signal processing, and another is based on a differential pulse loop with multi-pulse sequence analysis, to enhance the timing accuracy. In addition, it is possible to determine the effective index of a single-mode fiber with known fiber length, which is important prerequisite information for practical applications in the field with uncertain laser wavelength and ambient temperature. When using a low-end oscilloscope with a nominal 26 MS/s sampling rate, compared with the measurement results of optical frequency domain reflectometer (OFDR) (LunaOBR4600), the double pulse method has an error of ±6 cm. For the multi pulse method, the measurement error can be as low as 1.75 mm for a fiber length of 2.049 km (relative error of 8.54 × 10−7).

A new type of human immunoglobulin G (IgG) sensors based on the surface plasmon resonance (SPR) in the low refractive index (RI) plastic optical fiber (POF) and an antibody immobilization method is presented. A 50-nm-thick gold film was formed on the polished D-shaped fiber surface by magnetron sputtering. The RI response of the POF sensor is 30 049.61 nm/RIU, which is 26.5 times higher than that of single mode fiber (SMF) SPR sensors. The proposed SPR biosensor can be developed by simple and rapid modification of the gold film with 11-mercapto undecanoic acid (MUA). Upon immobilization of the goat anti-human IgG antibody, the resonance wavelength shifts by 11.2 nm. The sensor can be used to specifically detect and quantify the human IgG at concentrations down to 245.4 ng/mL with the sensitivity of 1.327 7 nm per µg/mL, which offers an enhancement of 12.5-fold compared to that of the conventional SMF based SPR sensors. The proposed device may find the potential applications in the case of use at the point of care.

Recent advances in semiconductor sequencing platform (SSP) have provided new methods for preimplantation genetic diagnosis/screening (PGD/S). The present study aimed to evaluate the applicability and efficiency of SSP in PGD/S. The artificial positive single-cell-like DNAs and normal single-cell samples were chosen to test our semiconductor sequencing platform for preimplantation genetic diagnosis/screening (SSP-PGD/S) method with two widely used whole-genome amplification (WGA) kits. A total of 557 single blastomeres were collected from in vitro fertilization (IVF) couples, and their WGA products were processed and analyzed by our SSP-PGD/S method in comparison with array comparative genomic hybridization (array-CGH). Our SSP-PGD/S method indicated high compatibilities with two commercial WGA kits. For 557 single blastomeres, our method with four million reads in average could detect 24-chromosome aneuploidies as well as microdeletion/microduplication of the size over 4 Mb, providing 100% consistent conclusion with array-CGH method in the classification of whether it was transplantable. Our studies suggested that SSP-PGD/S represents a valuable alternative to array-CGH and brought PGD/S into a new era of more rapid, accurate, and economic.

(Abstracted from Am J Obstet Gynecol2020;222:185.e1–185.e17)Hemoglobin Bart's hydrops fetalis syndrome (Hb Bart's) is a common inherited genetic disease in the south of China and Southeast Asia. Couples who are both carriers of the Southeast Asian type of α-thalassemia gene deletion have a 25% risk of having a pregnancy affected with Hb Bart's as a result of autosomal recessive inheritance.