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The purpose was to explore the value of liver fibrosis scores (fibrosis-4, BAAT score and BARD score) for incidence risk of stroke in a cohort study.A total of 9088 participants without stroke history enrolled the follow-up. Three liver fibrosis scores (LFSs) including FIB-4, BARD score and BAAT score were adopted. The end point was stroke. Cox regression analysis was used to calculate hazard ratios and 95% confidence interval. Kaplan-Meier curve was used to show the probability of stoke in different levels of LFSs. Subgroup analysis showed the association between LFSs and stroke under different stratification. Restricted cubic spline could further explore whether there is a linear relationship between LFSs and stroke. Finally, we used C-statistics, Net Reclassification Index (NRI) and Integrated Discrimination Improvement (IDI) to assess the discriminatory power of each LFS for stroke.During a median follow-up time of 4.66 years, 272 participants had a stroke. Through the baseline characteristics, we observed that the stroke incidence population tends to be male and older. It was shown by Kaplan-Meier that three LFSs were associated with stroke and high levels of LFSs significantly increase the probability of stroke. In the univariate Cox regression analysis, the HR of stroke risk was 6.04 (4.14-8.18) in FIB-4, 2.10 (1.45-3.04) in BAAT score and 1.81 (1.38-2.38) in BARD score by comparing the high level with the low level at each LFSs. The adjusted HRs for three LFSs were 2.05 (1.33-3.15) in FIB-4, 1.61 (1.10-2.35) in BAAT score and 1.54 (1.17-2.04) in BARD score by comparing the high group with low group. We found that multivariable-adjusted HRs of three LFSs still increased for stroke when stratified by various factors in subgroup analysis. Moreover, after adding LFSs to original risk prediction model which consist of age, sex, drinking, smoking, hypertension, diabetes, low-density lipoprotein cholesterol, total cholesterol and triglycerides, we found that new models have higher C-statistics of stroke. Furthermore, we calculated Net Reclassification Index (NRI) and Integrated Discrimination Improvement (IDI) to show the ability of LFSs to predict stroke.Our study showed that three LFSs were associated with stroke amongst middle-aged populations in rural areas of Northeast China. Furthermore, it suggests that LFSs can be used as a risk stratification tool to predict stroke.

Raman spectroscopy is often used for the composition determination and rapid classification of materials because it can reflect the molecular information of materials. Its accuracy mainly depends on the performance of the classification algorithm. In addition to classic machine learning classifiers such as support vector machines and k-nearest neighbor, 1D convolutional neural networks (CNNs) have also been applied to recognize Raman spectra. However, most of the research on 1D CNNs is still in the shallow, simple structure of the network model, and its application scope is only for the classification of a few classes. Therefore, this paper proposes a spectral data classification model based on a 1D deep CNN for classifying and recognizing hundreds of classes. We used the RRUFF Raman spectrum database containing many mineral samples to construct two sub-datasets, which were used to evaluate the classification effect of the model from different perspectives without data enhancement. The experimental results show that the model has a high recognition accuracy for data sets with hundreds of classes and sufficient samples. Compared with the classic machine learning classification algorithm and the 1D CNN models proposed by other scholars, our model has higher recognition accuracy and better performance and has better applicability to datasets with thousands of classes and imbalanced class distribution.

DNA polymerase gamma (PolG) is the major polymerase of mitochondrial DNA (mtDNA) and essential for stabilizing mitochondrial function. Vascular calcification (VC) is common senescence related degenerative pathology phenomenon in the end-stage of multiple chronic diseases. Mitochondrial dysfunction was often observed in calcified vessels, but the function and mechanism of PolG in the calcification process was still unknown. The present study found PolGD257A/D257A mice presented more severe calcification of aortas than wild type (WT) mice with vitamin D3 (Vit D3) treatment, and this phenomenon was also confirmed in vitro. Mechanistically, PolG could enhance the recruitment and interaction of p53 in calcification condition to recover mitochondrial function and eventually to resist calcification. Meanwhile, we found the mutant PolG (D257A) failed to achieve the same rescue effects, suggesting the 3'-5' exonuclease activity guarantee the enhanced interaction of p53 and PolG in response to calcification stimulation. Thus, we believed that it was PolG, not mutant PolG, could maintain mitochondrial function and attenuate calcification in vitro and in vivo. And PolG could be a novel potential therapeutic target against calcification, providing a novel insight to clinical treatment.

Surface-enhanced Raman spectroscopy (SERS) has attracted lots of interest in academic and industrial fields in recent years. The improvement in long-time sensitivity and repeatability is highly demanded by the on-site applications. Herein, we present an expedient SERS strip tactic with these desired advantages. Specifically, the tactic utilized the outstanding stability of colloidal particles to maintain the SERS materials during the storage. Upon usage, the strip is rapidly prepared on-site, and then the targets were sampled with a dip-coating and heating method, which is designed to standardize the whole detection process with the sensitivity kept. Thanks to the tactic, only one-third of SERS sensitivity decay was observed for rhodamine 6G after half a year. Besides rhodamine 6G, the SERS spectra of different animal blood samples were also investigated with the SERS strip tactic, and a species-based discrimination capability was preliminarily demonstrated.

In the paper, we present the sea experiment of positioning underwater vehicles using multiple surface beacons. A system is designed to realize the underwater vehicles' positioning using the time difference of arrivals (TDOA) technique, where no strict clock synchronization between beacons and underwater vehicles is required. Moreover, an Extended Kalman Filter (EKF) method is introduced to improve the robustness. A sea experiment is conducted to verify the proposed positioning method. In the experiment, three surface beacons broadcast positioning messages synchronously at a given interval. The underwater node uses the received positioning messages and its corresponding arrival time to perform the position calculation. The experimental results show that the proposed positioning method works well and the average positioning error is less than 20 meters.

The sound intensity periodic structure in the shadow zone is mainly caused by the interference among the bottom-reflected wave, the bottom-surface-reflected wave, the surface-bottom-reflected wave, and the surface-bottom-surface-reflected wave and the corresponding interference period is related to the location of sound source. The traditional method extracts the interference period manually and matches the interference period with the simulation result to estimate the source localization. Manual extraction process is cumbersome and may introduce large errors. In this paper, the mechanism of interference fringe formation is analyzed in depth, and it is pointed out that the interference period is determined by the multipath delay difference, and the multipath delay difference is related to the source localization, so that source localization can be performed. Finally, a method of autonomous extraction of interference period and source location estimation is proposed, and the feasibility of this method is verified by simulation.

This paper is concerned with two classical modulation schemes of M-ary and CSK in spread spectrum technology, our treatment is focused on the communication performance of two schemes in the deep-sea vertical channel. We process long-term experimental data with sea-depth from 1207m to 3870m for three times, and present the deep-sea vertical channel properties such as the time-delay spread, the amplitude of the successive paths and the time-varying multipath structure. The influence of the deep-sea vertical channel on the communication performance of the two schemes is analyzed, their performance are compared based on the experimental data.

Underwater acoustic MODEMs are usually powered by batteries, it is very important to design a low-power wake-up detector to save the power of modems. This paper proposes a low-complexity wake-up detector for underwater acoustic MODEM. A balanced Gold sequence is used to design a two-phase code signal as the wake-up signal. A detector algorithm is proposed that requires only one addition, one subtraction and two multiplication operations for each sample, thus achieving low computational complexity, at the same time, the algorithm can also provide accurate Doppler estimation and rough arrival time estimation for the wake-up signal. The proposed wake-up detection algorithm has been successfully tested in the lake experiment, the results show that, the proposed detector achieves high detection rate and low false alarm rate. Therefore it is suitable as a low-power wake-up detector for underwater acoustic MODEM.

Direct-sequence spread-spectrum (DSSS) underwater acoustic (UWA) communication can obtain considerable matching processing gain at the receiving end, which is the preferred communication method for high quality underwater acoustic communication. However, under the mobile condition, the DSSS receiving signal will face fast carrier phase fluctuation interference, resulting in a serious degradation of the matching processing gain at the receiving end. Aiming at this problem, this paper proposes a dual differential spread-spectrum (DDSS) UWA communication technology: double differential encoding of the original information sequence at the transmitting end; dual-difference correlation detector for decoding at the receiving end, which can effectively suppress fast carrier phase interference. The simulation results show that the DDSS UWA communication can achieve -8dB SNR robust acoustic communication under the condition of relative motion speed of 8m/s, and the communication error rate is less than 10−3.

In the underwater passive positioning systems (UPPS), it involves a key technology of multi-user communication that the beacons synchronously send positioning messages to the targets. Interferences from other users, referred to multi-access interferences (MAIs), can induce significant bit errors for the desired user. In this paper, we designed an underwater acoustic Code Division Multiple Access (CDMA) system using the coded cyclic shift key (CCSK) modulation, and proposed a hybrid MAI cancellation scheme based on cyclic shift inverse matrix transform (CSIMT) and recursive least square (RLS) in the CDMA system. The hybrid scheme can suppress MAI better than RLS or CSIMT, and meets the requirements of strong stability to support reliable transmission for UPPS. The CSIMT interference cancellation performs well under the far-near effects, which doesn’t depend on the accuracy of the estimation of transmitted data, and the strong MAI can be reduced by transformation of the zero-forcing correlation values using m sequence cyclic shift inverse matrix. The RLS interference cancellation is used to mitigate MAI form the detected users with comparable power, by using the estimated the channel impulse response between the receiver and the detected users, and the regenerated signal of detected users form decoder output, which allows of strong error-correcting codes, and it’s robust in an asynchronous environment. The theoretical analysis and experimental result show that the hybrid MAI cancellation scheme can effectively suppress MAI better. The shallow water sea trial was carried out near Dalian Tiger Beach Ocean Park in China, at a distance of about 5 km, the data rates of 100bps, where three users could communicate asynchronously with low failure ratio and can match the UPPS application.

Underwater acoustic (UWA) communication is a major tool for underwater wireless data transmission. In this paper, cross-subband rateless encoding for filtered multitone (FMT) in UWA communications is proposed. Rateless codes are a class of erasure correcting codes that the source data can be recovered from a minimum number of received symbols. For FMT modulation, there are fewer taps in the equivalent channel for each subband in time domain, and different subbands can be treated with different frequency-selective fadings. Therefore, recursive least square (RLS) decision feedback equalization (DFE) with less filter length can be used for symbol-recovery in each subband, and the recovered symbols from severer frequency fading subbands can be abandoned. Mean square error (MSE) values are calculated as the criteria for determining the candidate subbands, i.e. recovered symbols from those subbands with less MSE values will be adopted for rateless decoding. Cross-subbands rateless encoding is adopted for source bit encoding, and two rateless encoding schemes are adopted, which are windowed random matrices based LT code and Raptor code that takes Reed-Solomon (RS) outer correcting code together with the former LT code. The proposed method was verified by experimental results.

The characteristics of underwater acoustic channel is strong multipath, severe Doppler and limited bandwidth. OFDM modulation has good ability in anti multipath and Turbo Product Codes(TPC) has excellent performance in a high code rate, We make full use of their advantages and designed an OFDM underwater acoustic communication system based on TPC. Using the BELLHOP simulation model to get the approximate actual response of the shallow underwater acoustic channel with strong multipath characteristics and large time delay. Take our system for a large number of data simulation under this kind of channel, we obtained the curve of error bit rate, the result show that the system has excellent performance in multi-path and Doppler channel.

In recent years, whether autonomous monitoring of ocean environment, deep seabed resources surveying, underwater sensor networks, or military underwater detection networks, etc, there are widespread needs of underwater acoustic networks (UANs). This paper provides a brief overview of the characteristics and advances of UANs, and the main research contents and key technologies of UANs are analyzed, including physical layer technologies, media access control (MAC) protocols and routing protocols. Underwater acoustic communication (UWAC) in the physical layer is the basis for UANs, and its research covers multi-frequency shift keying (MFSK), multi-phase shift keying (MPSK), direct-sequence spread spectrum (DSSS), and orthogonal frequency division multiplexing (OFDM). Common MAC protocols include Time Division Multiple Access (TDMA), ALOHA and MACAW (MACA for Wireless), and are all used in UANs. Routing protocols involve static routing, hybrid routing, and self-organizing routing. The experimental research on underwater acoustic network in the Sanya area is introduced in detail. The network was composed of 15 nodes developed by three institutes. The modems of the nodes deployed used UWAC technology, such as MFSK, MPSK and OFDM. Each network node installed TD, CTD, acoustic Doppler current profiler (ADCP) or other ocean monitoring equipment, gateway was connected with the shore station via radio, and the server of the shore station was connected to the Internet. The network was running for 43 days, and online monitoring of the ocean environment was realized. This paper gives analysis on packet loss ratio, transmission delay and network energy efficiency of the nodes developed by the Hangzhou Applied Acoustics Research Institute. The node packet loss ratio was 2.9%, the average delay was 0.947 minute per hop, when the packet size was 404 bits, and the energy efficiency was 0.7831 bit / J.

The Pseudo Random Noise(PRN) signal has a wide application in active sonar detection, because it has good doppler and range resolution. Aimed at traditional matched filter processing of a PRN signal, there is a need for multiple copy signals, because the PRN signal is sensitive to doppler frequency shift. A new detector based on Fractional Correlation is proposed in this paper. As a generalized form of the Fourier Transform Fractional Fourier Transform(FRFT) can not only deal with the signals of the general sense, but they can also resolve time-varying non-stationary signals. Fractional Correlation processing expands signal processing in Fourier Transform domain to Fractional Fourier Transform domain, hence there is a positive significance in the introduction of FRFT to underwater acoustic detection; and, in the development of a novel detector based on FRFT to deal with complex underwater ambient noise and suppression doppler effects. The theory of a Fractional Correlation detector is derived, and the following are explicitly studied: the detction performance in white Gaussian noise environment; the optimal rotation parameters of the Fractional Correlation detector; and, the computational complexity of the Fractional Correlation detector. The anti-doppler property of Fractional Correlation detector, and the optimal rotation parameter fit to suppress doppler effects are specifically derived. Computer Simulations are provided in order to illustrate the proposed performances of the Fractional Correlation detector. Sea trial data analysis shows that a Fractional Correlation detector base on Fractional Fourier Transform has a better performance than a traditional matched filter, and that it also has good robustness. The Fractional Correlation detector can suppress doppler effects by estimating the optimal rotation parameter in Fractional Fourier Transform domain when the target doppler frequency shift is 2.0 percent of center frequency. The Fractional Correlation detector also has a good performance, so the detector base on Fractional Fourier Transform has broad application prospects.

Underwater acoustic communication networks have gained more and more attention in recent years due to their good prospects in the application of environmental monitoring, underwater surveillance, disaster forecasting, and so on. A sea trial of an underwater acoustic communication network, with up to 10 nodes, was carried out near Shengsi in the East China Sea, in June 2015. The trial was designed with the aim of obtaining application experience in underwater network deployment and in order to evaluate the performance of protocols in a real-world environment. In the physics layer, M-ary spread spectrum communication and the passive time reversal processing are adopted. In data link layer, RTS/CTS handshake based MAC is applied. In the network layer, a reactive routing protocol is tested. In this paper, the configuration of the MODEM, system architecture, and experimental procedure and results are all given. By sea trial, it is demonstrated that the robustness of the network in performing multiple nodes sharing channel and route setup in a realistic underwater environment.

A direct‐sequence spread‐spectrum (DSSS) acoustic communication system was proposed. It used a Gold‐sequence family to transmit information, which was recovered by a RAKE filter receiver. A Gold‐sequence family of large size and of large main‐to‐side lobe ratio (MSLR) of the quasi‐orthogonal function was selected, and the spectral efficiency was improved without communication reliability loss. For the transmitter, message bits were loaded in one symbol by selecting the sequence number in the Gold‐sequence family and pulse position modulation (PPM) was used. For the receiver, the transmitted information was recovered using a cyclic correlation method. Field sea experiments were conducted to test this DSSS system. It was robust at low signal‐to‐noise ratio (SNR) and over complex multipath channels.