Accurate Peak Detection for Optical Sensing with Reduced Sampling Rate and Calculation Complexity.

Fiber Bragg gratings (FBGs) are widely applied in optical sensing systems due to their advantages including being simple to use, high sensitivity, and having great potential for integration into optical communication systems. A common method used for FBG sensing systems is wavelength interrogation. The performance of interrogation based sensing systems is significantly determined by the accuracy of the wavelength peak detection processing. Direct maximum value readout (DMVR) is the simplest peak detection method. However, the detection accuracy of DMVR is sensitive to noise and the sampling resolution. Many modified peak detection methods, such as filtering and curve fitting schemes, have been studied in recent decades. Though these methods are less sensitive to noise and have better sensing accuracy at lower sampling resolutions, they also confer increased processing complexity. As massive sensors may be deployed for applications such as the Internet of things (IoT) and artificial intelligence (AI), lower levels of processing complexity are required. In this paper, an efficient scheme applying a three-point peak detection estimator is proposed and studied, which shows a performance that is close to the curve fitting methods along with reduced complexity. A proof-of-concept experiment for temperature sensing is performed. 34% accuracy improvement compared to the DMVR is demonstrated.

Fiber Bragg grating sensing system with wavelength-swept-laser distribution and self-synchronization.

Fiber Bragg gratings (FBGs) with various interrogation schemes to estimate the FBG's spectrum shift have been widely used in fiber sensing systems. Wavelength swept laser (WSL) based interrogation architectures have been proposed to offer rapid and high-quality sensing performance. However, for getting higher sensing accuracy, the demands for high-performance WSL may push the system cost. Under these considerations, a WSL distribution architecture allowing multiple sensing processing units (SPUs) to share the WSL is studied in this Letter. A self-synchronization scheme is proposed to enable flexible SPU deployment with no concerns for the clock calibration. The proposed system is experimentally studied. Temperature estimation error of ∼2.5∘C and ∼0.5∘C with sensitivities of 0.13°C/ms and 0.14°C/ms, respectively, for the high and small temperature ranges are demonstrated.

Use of longer sized screws is a salvage method for broken pedicles in osteoporotic vertebrae.

Screw loosening due to broken pedicles is a common complication resulting from the insertion of screws either with inadequate diameters or into an osteoporotic pedicle. In this novel in vitro study, we tried to clarify the contribution of the pedicle to screw fixation and subsequent salvage strategies using longer or larger-diameter screws in broken pedicles. Sixty L4 fresh-frozen lumbar vertebrae harvested from mature pigs were designed as the normal-density group (n = 30) and decalcified as the osteoporosis group (n = 30). Three modalities were randomly assigned as intact pedicle (n = 30), semi-pedicle (n = 15), and non-pedicle (n = 15) in each group. Three sizes of polyaxial screws (diameter × length of 6.0 mm × 45 mm, 6.0 mm × 50 mm, and 6.5 mm × 45 mm) over five trials were used in each modality. The associations between bone density, pedicle modality and screw pullout strength were analyzed. After decalcification for 4 weeks, the area bone mineral density decreased to approximately 56% (p < 0.05) of the normal-density group, which was assigned as the osteoporosis group. An appropriate screw trajectory and insertional depth were confirmed using X-ray imaging prior to pullout testing in both groups. The pullout forces of larger-diameter screws (6.5 mm × 45 mm) and longer screws (6.0 mm × 50 mm) were significantly higher (p < 0.05) in the semi- and non-pedicle modalities in the normal-density group, whereas only longer screws (6.0 mm × 50 mm) had a significantly higher (p < 0.05) pullout force in the non-pedicle modalities in the osteoporosis group. The pedicle plays an important role in both the normal bone density group and the osteoporosis group, as revealed by analyzing the pullout force percentage contributed by the pedicle. Use of a longer screw would be a way to salvage a broken pedicle of osteoporotic vertebra.

Biomechanical study of the fixation stability of broken pedicle screws and subsequent strategies.

Pedicles are often broken when screws are inserted into hard pedicles with small diameters or when the diameter of the screw itself is inadequate. However, there is a lack of biomechanical literature that addresses screw loosening as a result of broken pedicles or the resulting salvage of those screws. We performed a novel in vitro study to compare the pullout strength of screws between intact pedicles and two different types of broken pedicles; strategies to prevent screw loosening were also compared. Thirty L4 Sawbones were designed to represent intact pedicles, semi-pedicles, and nonpedicles and were prepared for screw insertion. Three sizes of polyaxial screws (diameter × length dimensions of 6.0 mm × 45 mm, 6.0 mm × 50 mm and 6.5 mm × 45 mm) were independently and randomly distributed into the intact-pedicle group (IP group, n = 30), the semi-pedicle group (SP group, n = 15), or the nonpedicle group (NP group, n = 15). The experiments were conducted across a minimum of five trials for each of the chosen screw sizes. We then analyzed the results of the imaging, pullout testing, and embedded bone volume. Any fractures or defects of the vertebrae caused by screw insertion were excluded from the study. The appropriate screw trajectory and insertional depth were confirmed using axial and sagittal X-ray imaging prior to screw pullout testing. A pullout strength of only 41% to 45% for the SP group and 29% to 39% for the NP group was retained following a broken pedicle. The use of longer or larger-diameter screws appears to be an effective salvaging procedure for the NP group (p < 0.05). The embedded bone volume percentage analysis indicated that, compared to the IP group, 68% to 76% of effective bone embedded into the screw threads in the SP group, and 58% to 65% in the NP group. There was no direct correlation between the pullout strength and the embedded bone volume; however, less effective embedded bone volume was associated with lower pullout strength. This study describes the evolution of the well-established screw pullout test being applied to the broken pedicle Sawbone testing model. The pedicle plays an important role in determining the pullout strength of a screw. However, a salvage procedure that utilizes a longer or larger-diameter screw might be a reliable clinical approach to address broken pedicles.

[Research on raman spectra and energy transfer in Tm3+, Ho3+ single and co-doped YVO4 crystals].

Raman spectra of Tm3+ :YVO4, Ho3+ :YVO4 and Tm3+: Ho3+: YVO4 crystals were measured at room temperature by HRD-1 double grating monochromator, with the excitation laser beam were parallel and perpendicular to c axis, respectively. For the Ho3+: YVO4, it was found that the Raman spectrum excited by laser beam perpendicular to axis c is stronger than that by parallel excitation, and because 488 nm laser was very close to the absorption peak of Ho3+, the competition between absorption and scattering results in the 475 cm(-1) Raman mode weakening and external mode widening. It was also found that the most probable phonon energy focused on the 880 cm(-1), which was brought about by the breathe mode of (VO4)3-, Like YAG, YVO4 is a kind of crystal with high phonon energy too. Comparing the luminescence of Tm3+ :YVO4 with that of Tm3+: Ho3+: YVO4, it was found that the intensity of Ho3+ 2.09 microm is about 4/5 of that of Tm3+ 1.85 microm, which means the sensitization efficiency of Tm3+ to Ho3+ was as high as up to 80%, and since the overlap between the luminescence of Tm3+ with the absorption of Ho3+ is quite small, the radiative energy transfer between them was very less possible, and most probability, this process was via the nonradiative, phonon-aided cross-relaxation between Tm3+ and near resonance energy transfer between Tm3+ and Ho3+.

Relationships between dorsolateral prefrontal cortex metabolic change and cognitive impairment in first-episode neuroleptic-naive schizophrenia patients.

The present study aimed to explore the possible associations between the dorsolateral prefrontal cortex (DLPFC) metabolites and the cognitive function in first-episode schizophrenia (FES).This study included 58 patients with FES (29 males and 29 females; mean age, 22.66 ±â€Š7.64 years) recruited from the First Affiliated Hospital, College of Medicine, Zhejiang University, and 43 locally recruited healthy controls (16 males and 27 females; mean age, 23.07 ±â€Š7.49 years). The single-voxel proton magnetic resonance spectroscopy was used to measure the levels of N-acetylaspartate (NAA); complex of glutamate, glutamine, and γ-aminobutyric acid (Glx); choline-containing compounds; and myo-inositol in the DLPFC. The ratios of metabolites to creatine (Cr) were calculated. The cognitive function was assessed by Measurement and Treatment Research to Improve Cognition in Schizophrenia Consensus Cognitive Battery (MCCB). Correlation analysis was used to assess the relationships between the DLPFC metabolites and the cognitive function.Compared with the healthy controls, the patients with FES showed significantly reduced scores in each part of the MCCB, significantly reduced NAA/Cr, and significantly increased Glx/Cr in the left DLPFC. Poor performance in verbal learning and visual learning was correlated to the reduced NAA/Cr ratio in the left DLPFC.These findings suggest that a lower NAA/Cr ratio in the left DLPFC is associated with the cognitive deficits in patients with FES, and may be an early biochemical marker for the cognitive impairment in schizophrenia.