Search

The age-hardening behavior and precipitation evolution of an isothermal aged Mg−5Sm−0.6Zn−0.5Zr (wt.%) alloy have been systematically investigated by means of transmission electron microscopy (TEM) and atomic-resolution high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The Vickers hardness of the present alloy increases first and then decreases with ageing time. The sample aged at 200 °C for 10 h exhibits a peak-hardness of 90.5 HV. In addition to the dominant β0′ precipitate (orthorhombic, a = 0.642 nm, b = 3.336 nm and c = 0.521 nm) formed on {11-20}α planes, a certain number of γ” precipitate (hexagonal, a = 0.556 nm and c = 0.431 nm) formed on basal planes are also observed in the peak-aged alloy. Significantly, the basal γ” precipitate is more thermostable than prismatic β0′ precipitate in the present alloy. β0′ precipitates gradually coarsened and were even likely to transform into β1 phase (face centered cubic, a = 0.73 nm) with the increase of ageing time, which accordingly led to a gradual decrease in number density of precipitates and finally resulted in the decreased hardness and mechanical property in the over-aged alloys.

A fiber Bragg grating (FBG) pulse and systolic blood pressure (SBP) measurement system based on the edge-filtering method is proposed. The edge filter is the Mach–Zehnder interferometer (MZI) fabricated by two fiber couplers with a linear slope of 52.45 dBm/nm. The developed system consists of a broadband light source, an edge filter, fiber Bragg gratings (FBGs), a coarse wavelength-division multiplexer (CWDM), and signal-processing circuits based on a field-programmable gate array (FPGA). It can simultaneously measure pulse pulsations of the radial artery in the wrist at three positions: Cun, Guan and Chi. The SBP can be calculated based on the pulse transit time (PTT) principle. The measurement results compared to a standard blood pressure monitor showed the mean absolute error (MAE) and standard deviation (STD) of the SBP were 0.93 ± 3.13 mmHg. The system meets the requirements of the Association for the Advancement of Medical Instrumentation (AAMI) equipment standards. The proposed system can achieve continuous real-time measurement of pulse and SBP and has the advantages of fast detection speed, stable performance, and no compression sensation for subjects. The system has important application value in the fields of human health monitoring and medical device development.

It is a critical challenge to develop reliable, stable, and sensitive biosensors for specific detection of mucin 1 (MUC1). In this paper, a label-free biosensor based on polydimethylsiloxane (PDMS) combustion product and graphene oxide (GO) functionalized tapered fiber (PGTF) was proposed and demonstrated for high sensitivity MUC1 detection. The PDMS combustion product is mainly composed of SiO2, which can be firmly bonded to the surface of the fiber, effectively increasing the specific surface area of the fiber. At the same time, the combination of the PDMS combustion product and the fiber cladding material will generate defects in the cladding, resulting in easier leakage of light inside the fiber core. Therefore, a strong evanescent field and interference effect can be obtained without drawing the tapered fiber waist very thin, which contributes to improving the sensitivity of fiber biosensor. In addition, GO has good biological affinity, a large specific surface area, and abundant functional groups, which can provide more binding sites for the attachment of biomolecule. The detection limit of the PGTF is 0.11 pM when the diameter of the fiber taper is 50 μm and modified with five layers of PDMS combustion product. Experimentally demonstrated sensor specificity and reproducibility, indicating that the sensor has a practical value for real applications. The PGTF has great potential as a simple, sensitive, and label-free assay in the field of cancer marker detection.

Abstract Background Two-dimensional speckle-tracking echocardiography (2D-STE) enables objective assessment of left atrial (LA) deformation through the analysis of myocardial strain, which can be measured by different speckle-tracking software. The aim of this study was to compare the consistency of 3 different commercially available software, which include vendor-specific software for measuring left ventricle (VSSLV), vendor-independent software packages for measuring LV strain (VISLV) and vendor-independent software packages for measuring LA strain (VISLA). Methods Sixty-four subjects (mean age: 44 ± 16 years, 50% males) underwent conventional echocardiograms using a GE Vivid 9 (GE Ultrasound, Horten, Norway) cardiac ultrasound system. Standard apical 4 and 2 chamber views of the left atrium were obtained in each subject with a frame-rate range of 40–71 frames/s. LA strain during the contraction phase (Sct), conduit phase (Scd), reservoir phase (Sr = Sct + Scd) were analyzed by 2 independent observers and 3 different software. Results Sct, Scd, Sr were, respectively, − 11.26 ± 2.45%, − 16.77 ± 7.06%, and 28.03 ± 7.58% with VSSLV, − 14.77 ± 3.59%, − 23.17 ± 10.33%, and 38.23 ± 10.99% with VISLV, and − 14.80 ± 3.88%, − 23.94 ± 10.48%, and 38.73 ± 11.56% when VISLA was used. A comparison of strain measurements between VSSLV and VIS (VISLV and VISLA) showed VIS had significantly smaller mean differences and narrower limits of agreement. Similar results were observed in the coefficient of variation (CV) for measurements between VSSLV and VIS (VISLV and VISLA). Comparison of the intra-class correlation coefficients (ICCs) indicated that measurement reliability was weaker with VSSLV (ICC 0.9). For intra-observer ICCs, VISLA > VSSLV = VISLV. For inter-observer ICCs, VSSLV > VISLA > VISLV. Conclusions Software measurement results of LA strain vary considerably. We recommended not measuring LA strain across vendor platforms.

In this paper, a sapphire-derived fiber (SDF) with a core diameter of 10 μm and a cladding diameter of 125 μm is fabricated by the melt-in-tube method, and fiber Bragg gratings (FBGs) with reflectivity over 80% are prepared by the femtosecond laser point-by-point direct writing method. By analyzing the refractive index distribution and reflection spectral characteristics of the SDF, it can be seen that the SDF is a graded refractive index few-mode fiber. In order to study the element composition of the SDF core, the end-face element distribution of the SDF is analyzed, which indicates that element diffusion occurred between the core and the cladding materials. The temperature and stress of the SDF gratings are measured and the highest temperature is tested to 1000 °C. The temperature and strain sensitivities are 15.64 pm/°C and 1.33 pm/με, respectively, which are higher than the temperature sensitivity of the quartz single-mode fiber. As a kind of special fiber, the SDF expands the application range of sapphire fiber, and has important applications in the fields of high-temperature sensing and high-power lasers.

In this paper, an energy regulation method based on the combination of a half-wave plate (HWP) and a polarization beam splitter (PBS) is proposed for the fabrication of apodized fiber gratings, which can effectively improve the side lobe suppression ratio of high-reflectivity fiber Bragg gratings (FBGs) fabricated by femtosecond laser. The apodized FBGs prepared by this method has good repeatability and flexibility. By inputting different types of apodization functions through the program, the rotation speed of the stepping motor can be adjusted synchronously, and then the position of the HWP can be accurately controlled so that the laser energy can be distributed as an apodization function along the axial direction of the fiber. By using the energy apodization method, the gratings with a reflectivity of 75% and a side lobe suppression ratio of 25 and 32 dB are fabricated in the fiber with a core diameter of 9 and 4.4 μm, respectively. The temperature and strain sensitivities of the energy-apodized fiber gratings with a core diameter of 4.4 μm are 10.36 pm/°C and 0.9 pm/με, respectively. The high-reflectivity gratings fabricated by this energy apodization method are expected to be used in high-power narrow-linewidth lasers and wavelength division multiplexing (WDM) systems.

A simple method for tuning a sampled nonlinearly chirped fiber Bragg grating (SNCFBG) without a center-wavelength shift is demonstrated experimentally. A uniform sampled fiber Bragg grating (SFBG) is adhered on a bent plastic plate along a precalculated curve. The nonlinear chirp among the SFBG channels is tuned when a displacement is applied to the free end of the plastic plate and the central wavelength of the grating is fixed. The dispersion varies from -996.3 to -117.9 ps/nm in the center channel and the center-wavelength shift is as small as 0.06 nm in the tuning process. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 432–434, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20493 [ABSTRACT FROM AUTHOR]

A novel temperature-independent strain sensor based on a fiber Bragg grating is demonstrated. The front section of the fiber Bragg grating is fixed to a crystal plate, and the other section is linearly etched in HF acid. The reflected power of the grating varies linearly with strain and is insensitive to temperature variation. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 324–326, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20458 [ABSTRACT FROM AUTHOR]

We theoretically analyze and experimentally demonstrate a simple method for adjusting the chirp of chirped fiber gratings by temperature, while the central wavelength is temperature insensitive. Chirped fiber grating with tapered cross-section area is mounted under tension in a negative thermal-expansion coefficients material. The central wavelength is determined by the tension, and almost does not vary with temperature after packaging. The chirp can be adjusted by temperature. The grating in the package exhibits a linear variation in chirp of -0.00051 nm/cm/°C, and the temperature coefficient of central wavelength is -0.0018 nm/°C [ABSTRACT FROM PUBLISHER]

In this paper, we report on high quality two-level phase-type Fresnel zone plates (FZPs) produced by femtosecond laser two-photon polymerization of the resin SU-8. The optical focusing property was tested using a simple experimental setup. Moreover, the lens imaging functions 'JLU' and '\mathsEPS+[c]{32028sym01.eps}{1.92pc} ' (English and Chinese abbreviations for Jilin University) were also demonstrated. In order to further enhance the diffraction efficiency, four-level and eight-level FZPs were designed using theoretical calculation and rapidly realized by point-to-point femtosecond laser scanning. In this way, the diffractive efficiency was enhanced from 35.8% for the two-level phase lens to 67% for the four-level phase lens and 73.9% for the eight-level phase lens, which are the largest values reported so far. [ABSTRACT FROM AUTHOR]