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Abstract Space debris laser ranging with a 4.2 W double-pulse 532 nm picosecond laser at a pulse repetition frequency of 1 kHz was achieved at the Shanghai satellite laser ranging (SLR) station, which receiving telescope was 60 cm. Space debris' radar cross sections were from 2 m2 to 12 m2, and ranging precision was up to centimeters. A compound regenerative amplifier was used to realize double pulses output with pulse space of 4.1 ns. Double pulses would have the same detection ability as the equal energy single pulse. A 500 μm diameter avalanche photo-diode detector with less than 10 kHz dark noise and a quantum efficiency of 40% at 532 nm was developed to improve the measurement capability. And also a spectral filter with high efficiency and narrow bandwidth were applied. Basing on the Shanghai SLR system, the laser ranging to space debris with picosecond laser at 1 kHz was successfully implemented for the first time among the global SLR stations. The results showed that the ranging precision root-mean-square can be achieved about 5 cm. It will be very useful to monitor and study the space debris. [ABSTRACT FROM AUTHOR]

An average power of 3 W green picosecond laser at a pulse repetition frequency of 1 kHz was reported. At the Shanghai satellite laser ranging (SLR) station, many satellites were measured with this laser and a narrow spectrum filter in the daytime. Satellites of the Beidou satellite navigation system for the Chinese, Global navigation satellite system for the Russian and Galileo satellite navigation system for the Europe were measured respectively. Especially ranging precision root mean square was up to 19.4 mm for the satellite of compassi5 about 37,000 km far from the earth. A Nd:YVO 4 mode-locked laser with an etalon, a dual-length of Nd:YAG regenerative amplification cavity, single-pass two Nd:YAG modules amplifier and nonlinear optical materials LiB 3 O 5 frequency doubling were designed. An average power of 3 W in 532 nm was obtained with pulse width of 30 ps, and angle of divergence was 0.8 mrad. Using the dual-length of regenerative cavity would greatly decrease the laser's volume and improve stability of picosecond laser. A narrow spectrum filter can reduce a lot of optics noise from the sun, and so all the satellites were almost be measured with this laser in the daytime at the Shanghai SLR station. [ABSTRACT FROM AUTHOR]

To obtain size distribution of nanoparticles, scanning electron microscope (SEM) and transmission electron microscopy (TEM) have been widely adopted, but manual measurement of statistical size distributions from the SEM or TEM images is time-consuming and labor-intensive. Therefore, automatic detection methods are desirable. This paper proposes an automatic image processing algorithm which is mainly based on local adaptive Canny edge detection and modified circular Hough transform. The proposed algorithm can utilize the local thresholds to detect particles from the images with different degrees of complexity. Compared with the results produced by applying global thresholds, our algorithm performs much better. The robustness and reliability of this method have been verified by comparing its results with manual measurement, and an excellent agreement has been found. The proposed method can accurately recognize the particles with high efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Diffusion tensor imaging (DTI) may provide an accurate noninvasive method of detecting degenerative matrix alterations in human lumbar intervertebral discs (IVDs). This study aimed to investigate age-related degenerative changes in human lumbar IVDs using DTI. Thirty asymptomatic volunteers ranging in age from 25 to 67 years underwent single-shot diffusion weighted echo-planar imaging on a 3 T scanner. DTI-derived metrics including fractional anisotropy (FA) and mean diffusivity (MD) were analyzed by a histogram analysis method. A Mann–Whitney test was used to compare subject groups (young and elderly) with respect to the diffusion measures, and piecewise linear regression was used to characterize the change in each metric as a function of age. We found significant age-related changes in the elderly adult group, with decrease of MD (11%, P<.001) and increase of FA (20%, P<.001). Our results demonstrate that the degenerative-related changes taking place in the IVDs through aging can be quantitatively accessed by DTI-derived metrics, while the morphologic changes are difficult to be identified in conventional T2-weighted images. Our initial findings suggest that it would be worthwhile to validate the relationship between DTI metrics and the actual degenerative status of IVDs using extracted disc samples and to extend it to studies on patients with degenerative discs in order to further explore the clinical usefulness and relevance of DTI. [Copyright &y& Elsevier]

• Cost-effective monitoring methods is needed to detect CO 2 leakage in carbon sequestration. • Our method does not need time-lapse imaging and directly detects CO 2 leak mass from raw seismic data. • Our leakage detection method are based on densely connected convolutional neural networks. In carbon capture and sequestration (also known as carbon capture and storage, or CCS), developing effective monitoring methods is needed to detect and respond to CO 2 leakage. CO 2 leakage detection methods rely on geophysical observations and monitoring sensor network. However, traditional methods usually require the development of site-specific physical models and expert interpretation, and the effectiveness of these methods can be limited to different application locations, operational scenarios, and conditions. In this paper, we developed a novel data-driven leakage detection method based on densely connected convolutional neural networks. Our method is an end-to-end detection approach, that differs from conventional leakage monitoring methods by directly learning a mapping relationship between seismic data and the CO 2 leakage mass. To account for the spatial and temporal characteristics of seismic data, our novel networks architecture combines 1D and 2D convolutional neural networks. To overcome the computational expense of solving optimization problems, we apply a densely-connecting strategy in our network architecture that reduces the number of network parameters. Based on the features generated by our convolutional neural networks, we further incorporate a long short-term memory network to utilize time-sequential information, which further improves the detection accuracy. Finally, we employ our detection method to synthetic seismic datasets generated based on flow simulations of a hypothetical CO 2 storage scenario with injection into a partially compartmentalized sandstone storage reservoir. To evaluate method performance, we conducted multiple experiments including a random leakage test, a sequential test, and a robustness test. Numerical results show that our CO 2 leakage detection method successfully detects the leakage and accurately predicts the leakage mass, suggesting that it has the potential for application in monitoring of real CO 2 storage sites. [ABSTRACT FROM AUTHOR]

The losses of Superconducting Magnetic Energy Storage (SMES) magnet are not neglectable during the power exchange process with the grid. In order to prevent the thermal runaway of a SMES magnet, quantitative analysis of its thermal status is inevitable. In this paper, the loss characteristics of a self-developed 150 kJ SMES magnet are analyzed by means of experiments and simulations, including the loss of the joint resistance, the eddy current loss of the metal cooling structures and the AC loss of the superconducting magnet. A thermal model of the magnet was built to theoretically analyze the relationship between the current and magnet temperature variation. Three kinds of power compensation experiments were carried out to study the thermal characteristics of the SMES magnet. The temperature variation of the magnet under these three operating conditions was simulated. The simulation results and experimental results are compared and analyzed. [ABSTRACT FROM AUTHOR]

This study sought to monitor the dynamic process of lymph node (LN) metastasis with intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI), and to investigate the impact of disease course on the detection of metastatic LNs by IVIM-DWI. Twenty female New Zealand rabbits with 2.5–3.0 kg body weight were studied. VX2 cells and egg yolk emulsion were randomly inoculated into one thigh to induce metastatic and inflammatory popliteal LNs, respectively. Eight rabbits underwent IVIM-DWI (14 b values, 0–2000 s/mm2) 2 h prior to, and 14, 21, and 28 days after inoculation (D0, D14, D21, D28). The apparent diffusion coefficient (ADC), true diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f) were measured and compared between the metastatic and the inflammatory groups at each time point. Three rabbits randomly chosen from the remaining twelve rabbits were sacrificed at each time point to perform hematoxylin and eosin staining and histologic evaluation. The patterns of dynamic change of D*, ADC, and D were different between the metastatic and the inflammatory LNs. The metastatic group had a lower D* value at D14 (p =.003), and greater ADC and D values at both D21 (p =.001, p =.001) and D28 (p =.021, p =.001), compared to the inflammatory group. The f value of the metastatic group was greater than that of the inflammatory only at D28 (p =.001). IVIM-DWI can reflect the dynamic process of LN metastasis, and disease course has a significant influence on the ability of IVIM-DWI to detect metastatic nodes. [ABSTRACT FROM AUTHOR]

BeiDou navigation satellite System (BDS), was the dedicated Chinese Global Navigation Satellite Systems (GNSS). The satellites in the BDS constellation can be tracked by many Satellite Laser Range (SLR) stations, making use of the onboard Laser Retro-reflector Array (LRA). Additionally, some of BDS satellites were also equipped with Laser Time Transfer (LTT) payloads. The measuring data from these instruments provided highly accurate estimations of satellites orbit, and time comparison between satellites and ground clocks.The performance of the BDS LRA and LTT payloads designed by Shanghai Astronomical Observatory (SHAO) were presented, as well as the SLR systems with a one meter-aperture telescope, which provided the ranging precision of centimeter levels for daylight ranging to BDS satellites at the synchronous orbit. For the first time, high precise LTT measurements at the synchronous orbit satellites were performed by the SHAO. The LTT data processing and analysis were presented with the time stability of 20ps at 500s, and a relative frequency stability of 10E-14.The further developments and improvements of Chinese LTT technology were also discussed. Global SLR tracking of BDS satellites were performed by the International Laser Ranging Service, providing accurate range data with global coverage. By using laser data, the accuracy of BDS satellite orbit and broadcast ephemeris were evaluated and the orbit error of BDS satellites was achieved at the meter level. [ABSTRACT FROM AUTHOR]

Most of efforts have been made to prepare high performance surface-enhanced Raman scattering (SERS) substrate for amplifying Raman signals. It still remains a grand challenging task in building a simple, conventional and low-cost SERS substrate with highly dense hotspots for improved sensitivity of the target analytes. Here, we report a very dexterous strategy to fabricate a distinctive SERS substrate with high density hotspots, using common adsorbent activated carbon (AC) as template to assemble silver nanoparticles (Ag NPs). It can be estimated that the enhancement effect of Ag NPs/AC composite is about 6.5-fold that of bare Ag NPs. Different from the resonant dyes, however, formaldehyde (FA) is a Raman-inactive molecule even though enhanced. Considering that, a novel method for quantitative analysis of FA using the Ag NPs/AC composite as SERS sensor has been developed, based on the catalytic effect of trace FA on the oxidation of malachite green (MG) through bromate under acidic condition. The change of MG from reduced form into oxidized leucomalachite green (LMG) results in the quench of Raman signals of MG, responding to 0.07 ppb FA that is about 2 orders of magnitude lower than the limit defined by the Nash's method as a standard procedure recommended in Europe, Japan and China. Moreover, SERS examinations of endogenous FA in human urine signify that the proposed method has high selectivity, reliability and accuracy. Thus, as-fabricated Ag NPs/AC composite is adequate as inexpensive and versatile SERS sensor utilized in the quantification of trace targets in various complicated matrices. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the value of intravoxel incoherent motion (IVIM) histogram analysis based on whole tumor volume in predicting microvascular invasion (MVI) of single hepatocellular carcinoma (HCC).Materials and Methods: The study enrolled 41 patients with pathologically proven HCCs who underwent IVIM diffusion-weighted imaging with nine b values and contrast-enhanced magnetic resonance imaging (MRI). Histogram parameters including mean; skewness; kurtosis; and percentiles (5th, 10th, 25th, 50th, 75th, 90th, 95th) were derived from apparent diffusion coefficient (ADC), perfusion fraction (f), true diffusion coefficient (D), and pseudo diffusion coefficient (D*). Quantitative histogram parameters and clinical data were compared between HCCs with and without MVI. For significant parameters, receiver operating characteristic (ROC) curves were further plotted to compare the diagnosis performance for identifying MVI.Results: The mean, 5th, 10th, 25th, 50th, and 75th percentiles of D, and the 5th, 10th, and 25th percentiles of ADC between HCCs with and without MVI were statistically significant (all P＜0.05). The histogram parameters of D* and f showed no statistically significant differences between HCCs with and without MVI (all P＞0.05). The areas under the ROC curves (AUCs) were 0.707-0.874 for D and 0.668-0.720 for ADC. The largest AUC of D (5th percentile) showed significantly higher accuracy than that of ADC or tumor size (P = 0.009-0.046). With a cut-off of 0.403 × 10-3 mm²/s, the 5th percentile of D value provided a sensitivity of 81% and a specificity of 85% in the prediction of MVI.Conclusions: Histogram analysis of IVIM based on whole tumor volume can be useful for predicting MVI. The 5th percentile of D was most useful value to predict MVI of HCC. [ABSTRACT FROM AUTHOR]

Reactive oxygen species (ROS) regulating the release of free zinc ions (Zn 2+ ) in cellular lysosome is closely related to various pathways of cellular signal transduction, such as inflammation and oxidative stress. Directly visualizing Zn 2+ release in lysosome is essential for in-depth understanding these physiological processes, and is still an atelic challenge. In this work, we successfully fabricate a lysosome-specific Zn 2+ fluorescent probe and achieve the visualization of ROS-induced Zn 2+ release in lysosome of inflammatory cells. The as-prepared probe combines a green fluorophore, an ionophore with five-dentate sites, and a morpholine as the lysosome-specific localization moiety. The fluorescence of the fluorophore in the free probe is suppressed by a photoinduced electron transfer (PET) process from nitrogen atoms in the ionophore. Upon the addition of Zn 2+ , the fluorescence can be promoted immediately, achieving the real-time detection. Meanwhile, the probe is sensitive and selective to Zn 2+ , which provides the capability to detect low-concentration of free Zn 2+ in lysosomes. Accordingly, the Zn 2+ release was clearly observed in lysosome with the increase of ROS levels when the inflammation occurred in living cells. [ABSTRACT FROM AUTHOR]

Objective The objective was to investigate the capabilities of diffusional kurtosis imaging (DKI) in detection of age-related white matter (WM) changes in elderly patients with leukoaraiosis. Material and methods Fractional anisotropy (FA), kurtosis, and diffusion parameters in the frontal lobe and parietal lobe were compared between 14 patients at Fazekas scale 0 and 1, and 15 patients at Fazekas scale 2 and 3. Results FA and DKI parameters were significantly altered in the ischemic lesions vs normal regions of WM in the severe patients. Conclusion DKI can provide sensitive imaging biomarkers for assessing the severity of leukoaraiosis in reference to Fazekas score. [ABSTRACT FROM AUTHOR]

The intracellular pH value controls many aspects of cell metabolism and is considered as an integral part of many metabolic reactions by maintaining the structure and function of nearly all proteins. Detection of pH fluctuation covering the whole intracellular pH window including both neutral and acidic is essential but challenging and still needs more sensitive pH probes. We have synthesized a new near-infrared fluorescent and colorimetric probe based on cyanine dye, which can be used for monitoring the pH fluctuation. The probe has a good water solubility, excellent photostability, reversibility, low cytotoxicity and exhibits a good performance to detect pH fluctuation in both solution and live cells. Upon incubation with live cells, it responds sensitively to low pH value in cell medium by exhibiting bright red fluorescence. On the contrary, the fluorescence intensity of probe seems to be very weak in neutral cellular environment. The satisfactory results show that the probe was a highly sensitive pH probe in living cells and further demonstrate its promising biological applications. [ABSTRACT FROM AUTHOR]