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Cadmium-hyperaccumulator Sedum plumbizincicola possesses strong capacities of Cd transport, accumulation and detoxification, but the transcriptional regulation mechanisms of Cd hyperaccumulation remain unknown. In this study, we examined the comparative transcriptome between S. plumbizincicola and non-accumulator Sedum alfredii with or without Cd treatments. Many differentially expressed genes involved in heavy metal transport and detoxification were found to be abundantly expressed in S. plumbizincicola. Meanwhile, a large number of differentially expressed transcription factor genes had been identified and revealed the complexity of transcriptional regulatory networks. Four transcription factor genes that were highly expressed in the roots of S. plumbizincicola were screened as candidate genes for creating CRISPR/Cas9 knockout mutations. The mutant lines of SpARR11 and SpMYB84 exhibited decreased Cd accumulation in the aboveground parts, indicating that the two transcription factors may be involved in the regulation of the Cd hyperaccumulation in S. plumbizincicola. Although further research will be needed to determine the precise targeted genes of these transcription factors, this study combining transcriptome analysis and CRISPR/Cas9 genome editing technology offers unprecedented opportunities to mine transcription factors related to Cd hyperaccumulation and contributes to uncovering the transcriptional regulation mechanism of hyperaccumulation in S. plumbizincicola.

Interferometric Synthetic Aperture Radar (InSAR) is a powerful and cost-effective technology to monitor ground deformation. Its accuracy is highly influenced by the atmospheric characteristic of the monitoring area. Separating the true ground deformation from atmospheric signals remains one of the major challenges in the application of InSAR. In this paper, the phase-based linear model, high spatial-resolution weather model (MERRA-2 and GACOS) and combination of MERRA-2 and phase-based linear model selected, and their performances in reducing the Tropospheric delay are assessed based on detrending standard deviation (DStd) of all Persistent Scattered (PS) points. A framework for the assessment is proposed and applied to a selected region of Shaoxing, Zhejiang Province, China. 26 Sentinel-1A images are used and processed by the method of PS-InSAR. It is found that the phase-based linear model outperforms the other models by at least 6.6% if the whole monitoring time span of the SAR images in the study area are considered. The proper tropospheric correction model in different seasons is not the same. The phase-based linear model is robust against the variations of atmospheric characteristics of the four seasons.

Cold seep and hydrothermal vent system have unique function in mass circulation of the earth, and have been explored by in situ detection technologies in past decades. A brief review on the development and the newest applications of in situ laser spectroscopy for deep sea research is presented here. The laser Raman spectroscopy and laser induced breakdown spectroscopy, with the advantages exactly meeting the requirement of the in situ detection, are emphatically introduced in this paper. The prospect of the in situ laser spectroscopy for the possible application in the deep sea is also discussed in this paper, aiming to provide a reference for the future development of spectroscopy.

Laser-induced plasma in water always suffers from strong pulse-to-pulse fluctuations due to the multiple breakdown phenomenon, leading to a poor stability of underwater LIBS signals. The traditional normalization method by using the internal standard element is often limited in some practical cases due to the lack of a suitable element as a reference. In this work, we developed an effective normalization method by using the plasma image information for underwater LIBS analysis. Correlations between the plasma images and LIBS spectra were firstly studied, showing a good linear relationship between the spectral line intensity and plasma image intensity. Subsequently, the spectral line intensities were standardized by using the corresponding image intensities and then used for quantitative analysis. A good normalization model was established by using partial least squares regression (PLSR). With the proposed method, the average relative standard deviations (RSDs) of validation samples were significantly reduced from 10.71% to 5.76%, and the average relative errors (AREs) of the validation samples were also reduced from 7.80% to 7.55%. Moreover, by combining the proposed method with the internal standard method, the average RSD and ARE can be further reduced to 4.07% and 4.86%, respectively, both of which are better than those obtained using the internal standard method only.

Double-pulse laser-induced breakdown spectroscopy (DP-LIBS) has been demonstrated to enable efficient elemental analysis of bulk water. Its applications are based on the fundamental understanding of the characteristics of the secondary plasma. However, due to the poor stability of the secondary breakdown, the inherent formation and evolution processes of the secondary plasma within the first laser formed bubble (LFB) remain unknown. By post focusing the second laser beam at the rear boundary of the first LFB (post-focus arrangement), the generated secondary plasma can provide a stable system for understanding its spatiotemporal behaviors. Based on this post-focus arrangement, the secondary plasma was characterized by using temporally resolved spectroscopy, monochromatic fast imaging and shadowgraph techniques. It was shown that the emission of underwater DP-LIBS presented transient increments within 1 μs. Such a distinctive temporal behavior was closely related to the back and forth movement of the secondary plasma within the first LFB, due to its spatial confinement effect. Species-specific imaging studies reveal that the interactions between the secondary plasma and the surrounding water vapor can give rise to the dissociation of water molecules, as well as the excitation of hydrogen and oxygen atoms. Meanwhile, the molecular emissions (CaOH) appeared only after 2 μs, but lasted for 32 μs, suggesting a slower plasma relaxation within the first LFB. Further shadowgraphic investigations highlight the quasi-static, low-pressure environment of the first LFB, which can reduce energy losses and enhance optical radiation from the secondary plasma.

In recent years, laser-induced breakdown spectroscopy (LIBS) has gained significant attention as a means for simple elemental analyses. The suitability of LIBS for contactless analysis allows it to be a perfect candidate for underwater applications. While the majority of LIBS systems still rely upon sub-kHz pulsed lasers, this contribution introduces 10s-kHz low pulse-energy lasers into underwater LIBS to improve the throughput and statistical validity. Interestingly, the spectral component significantly changed above a critical laser repetition-rate threshold. Spectral lines of atomic hydrogen and oxygen stemming from water become visible beyond a ∼10 kHz repetition rate. This observation suggests a different plasma dynamic compared to low repetition rates. When the pulse-to-pulse interval becomes sufficiently short, a cumulative effect begins to be significant. Apparently, the new phenomena occur on a timescale corresponding to a threshold rate of ∼10 kHz, i.e. ∼100 μs. Analytically, the high repetition rates result in improved statistical validity and throughput. More plasma events per unit time allowed the use of low efficiency Echelle spectrometers without compromising on the analytical performance. Meanwhile, the presence of H I and O I out of the water (as the matrix) also offers internal standardization in underwater elemental analysis. Since the laser fluence was on the lower edge of the plasma threshold, an additional ultrasound source was introduced to induce external perturbation, which significantly improved the plasma formation stability. A huge advantage of LIBS is the possibility of detecting almost all elements within a sample simultaneously. Throughout the periodic table, chlorine is one of the most challenging elements. Consequently, Ca2+ and Na+ were used as samples to demonstrate the capability of this high repetition-rate LIBS platform. As an ambitious benchmark for our system, chlorine detection in water was also discussed.

The technological advances in lasers enabled the wide application of laser-induced breakdown spectroscopy (LIBS) as a powerful analytical means for elemental analyses. Rather than commonly used lasers that operate at several to several-tens of Hz, the high repetition rate ones that operate at tens of kHz showed superior analytical advantages while implying unique excitation pathways. Specifically, the production of excited atomic hydrogen and oxygen, which can serve as internal standards, is quite different from that in commonly reported double-pulse LIBS. In this part of the work, it was found that the atomic emitters stemming from water are not related to cavitation bubbles. Moreover, the emitter productions of dissolved species, e.g., Na+, and water-related species, e.g., H-α, are two distinctive mechanisms. Towards analytical applications of the high repetition-rate system, the fundamental investigation can provide important guidelines to address real-life challenges. In this part of the work, the high repetition-rate regime of operation is explored from a more kinetic perspective.

With the wide application of lidar in the future, the problem of crosstalk between lidars will become more serious. True random coding photon counting lidar with high anti-crosstalk ability will play an important role in solving this problem. In this paper, based on the working principle of Gm-APD, the detection probability theoretical model of true random coding photon counting lidar is built, and the impact of jitter on detection probability is considered for the first time. The influence of mean echo photon number, mean pulse count density, sequence length and pulse width on detection probability is analyzed. Monte Carlo simulation and experimental results are highly consistent with the theoretical model, which proves the correctness of the detection probability theoretical model. This theoretical model provides an effective means to evaluate the system performance.

Ultrasound is widely employed in disease screening and diagnosis. However, ultrasound scanning requires experienced sonographers manually operating probes to search the lesions inside patients, which is unavailable in rural or remote areas. Recently, teleoperated ultrasound scanning systems are proposed to enable sonographers to conduct scanning and diagnosis remotely. Nevertheless, these systems cannot offer a good sense of operation. This paper proposed a teleoperated ultrasonic scanning allowing sonographers to control the remote scanning probe with a glove in real-time. It can significantly increase the sense of operation. Experiments show its feasibility and a good sense of operation. It is noteworthy that the system is potential and easy to upgrade.

Recently, molecular emissions from the laser-induced plasma in ambient gas have gained increasing interest; however, very little is known about the case in water solutions. In this work, we investigated the spatiotemporal characteristics of molecular emissions, CaOH for instance, in underwater laser-induced breakdown spectroscopy (LIBS) by using time-resolved spectroscopy, spectral-resolved imaging, and shadowgraph techniques. It was shown that clear CaOH molecular bands can be observed in the spectrum at very early times after the laser pulse and presented a much longer lifetime and more homogeneous emission distribution compared with the Ca I and Ca II lines. Such unique characteristics of CaOH molecular emission inspired us to improve the performances of underwater LIBS by using the CaOH molecular bands instead of Ca I and Ca II lines. We demonstrated the excellent quantification results of CaOH with higher stability, less self-absorption, and reduced matrix effect. Meanwhile, the limit of detection (LOD) of Ca with the CaOH molecular band (2.46 ppm) is comparable to that with the atomic line of Ca I (2.07 ppm), and much lower than that with the ionic line of Ca II (13.81 ppm), indicating a good sensitivity of CaOH. This work gives not only some insights into the molecule formation mechanisms in underwater plasmas, but also provides new ideas to improve the analytical performances of underwater LIBS.

The influences of laser focusing geometry on laser-induced plasma and laser-induced breakdown spectroscopy (LIBS) in bulk water are investigated by using fast imaging and spectroscopic techniques. Comparisons between different focusing geometries (spherical aberrations and focusing angles) are performed in terms of breakdown thresholds, plasma morphologies, emission distributions, pulse-to-pulse plasma fluctuations, and the corresponding LIBS signals. It is shown that spherical aberrations lead to an increase in the threshold energy of breakdown, to a formation of multiple elongated plasmas with weak emissions, and to a decrease in the signal intensity as well as LIBS stability. With aberration minimized focusing, larger focusing angles produce a lower breakdown threshold, a compact plasma with stronger emissions, and a higher signal intensity as well as higher LIBS stability. In particular, we demonstrate that with the minimized spherical aberrations and large focusing angles, the intensities of plasma emission continue to increase at higher laser energies and no clear saturation is observed. The present results suggest that a relatively large focusing angle should be applied for LIBS measurement in bulk water, and the spherical aberrations should be eliminated.

Characteristics of the secondary breakdown of dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) in bulk water were investigated with different axial focusing arrangements and laser energies of the second laser pulse. Compared to the pre-focus or in-focus arrangement, post-focus arrangement could provide both stronger emissions and better repeatability within the energy range of 20–40 mJ. Such phenomenon is directly related to the breakdown characteristics in different conditions. Especially for in-focus arrangement, i.e. the most reported case of DP-LIBS in bulk water, the breakdown all occurs at the bubble boundary rather than inside the gaseous bubble even using a quite large laser energy of 130 mJ. The simulation results further confirm the secondary breakdown could not occur directly in gas of the bubble interior under the present experimental setup.

A polarized micropulse lidar (P-MPL) employing a pulsed laser at 532 nm was developed by the Institute of Oceanographic Instrumentation, Qilu University of Technology (Shandong Academy of Sciences). The optomechanical structure, technical parameters, detection principle, overlap factor calculation method, and inversion methods of the atmospheric boundary layer (ABL) depth and depolarization ratio (DR) were introduced. Continuous observations using the P-MPL were carried out at Xi’an Meteorological Bureau, and the observation data were analyzed. In this study, we gleaned much information on aerosols and clouds, including the temporal and spatial variation of aerosols and clouds, aerosol extinction coefficient, DR, and the structure of ABL were obtained by the P-MPL. The variation of aerosols and clouds before and after a short rainfall was analyzed by combining time-height-indication (THI) of range corrected signal (RCS) and DR was obtained by the P-MPL with profiles of potential temperature (PT) and relative humidity (RH) detected by GTS1 Digital Radiosonde. Then, the characteristics of tropopause cirrus cloud were discussed using the data of DR, PT, and RH. Finally, a haze process from January 1st to January 5th was studied by using aerosol extinction coefficients obtained by the P-MPL, PT, and RH profiles measured by GTS1 Digital Radiosonde and the time-varying of PM2.5 and PM10 observed by ambient air quality monitor. The source of the haze was simulated by using the NOAA HYSPLIT Trajectory Model.

Early diagnosis of Neurocognitive Disorder (NCD) is crucial in facilitating preventive care and timely treatment to delay further progression. This paper presents the development of a state-of-the-art automatic speech recognition (ASR) system built on the Dementia-Bank Pitt corpus for automatic NCD detection. Speed perturbation based audio data augmentation expanded the limited elderly speech data by four times. Large quantities of out-of-domain, non-aged adult speech were exploited by cross-domain adapting a 1000-hour LibriSpeech corpus trained LF-MMI factored TDNN system to DementiaBank. The variability among elderly speakers was modeled using i-Vector and learning hidden unit contributions (LHUC) based speaker adaptive training. Robust Bayesian estimation of TDNN systems and LHUC transforms were used in both cross-domain and speaker adaptation. A Transformer language model was also built to improve the final system performance. A word error rate (WER) reduction of 11.72% absolute (26.11% relative) was obtained over the baseline i-Vector adapted LF-MMI TDNN system on the evaluation data of 48 elderly speakers. The best NCD detection accuracy of 88%, comparable to that using the ground truth speech transcripts, was obtained using the textual features extracted from the final ASR system outputs.

State-of-the-art neural language models (LMs) represented by Transformers are highly complex. Their use of fixed, deterministic parameter estimates fail to account for model uncertainty and lead to over-fitting and poor generalization when given limited training data. In order to address these issues, this paper proposes a full Bayesian learning framework for Transformer LM estimation. Efficient variational inference based approaches are used to estimate the latent parameter posterior distributions associated with different parts of the Transformer model architecture including multi-head self-attention, feed forward and embedding layers. Statistically significant word error rate (WER) reductions up to 0.5\% absolute (3.18\% relative) and consistent perplexity gains were obtained over the baseline Transformer LMs on state-of-the-art Switchboard corpus trained LF-MMI factored TDNN systems with i-Vector speaker adaptation. Performance improvements were also obtained on a cross domain LM adaptation task requiring porting a Transformer LM trained on the Switchboard and Fisher data to a low-resource DementiaBank elderly speech corpus.

This paper proposes an ingenious alignment scheme for a Doppler velocity log-aided strapdown inertial navigation system with only the initial velocity and position information. The proposed scheme decomposes the task into two tightly coupled subproblems. First, an optimization-based coarse alignment (OBCA) method is developed to derive the constant attitude at the very start of the alignment. During the OBCA process, the required velocity and position are all approximated using their initial values. Second, a nonlinear-filtering-based fine alignment (NFFA) is developed to refine the attitude and calculate the real-time velocity and position. In an NFFA, the standard inertial navigation equations are used directly as the process model, which, therefore, can track the vehicle maneuverability during the alignment period. The NFFA is carried out again from the very start, initialized with the roughly known attitude by OBCA and the known initial velocity and position information. This scheme necessitates the recording of the sensor data during the OBCA. The experimental results show that the proposed method can not only align the attitude to high precision within very short time, but also determine the velocity and position with satisfied accuracy.

This paper presented a comparative study of monoethanolamine (MEA) and diethanolamine (DEA) for post-combustion CO2 capture (PCC) process with different process configurations to study the interaction effect between solvent and process. The steady state process model of the conventional MEA-based PCC process was developed in Pro/II® and was validated with the experimental data. Then ten different process configurations were simulated for both MEA and DEA. Their performances in energy consumption were compared in terms of reboiler duty and total equivalent work. The results show that DEA generally has better thermal performances than MEA for all these ten process configurations. Seven process configurations provide 0.38%–4.61% total energy saving compared with the conventional PCC process for MEA, and other two configurations are not favourable. For DEA, except one configuration, other process configurations have 0.27%–4.50% total energy saving. This work also analyzed the sensitivities of three key parameters (amine concentration, stripper pressure and lean solvent loading) in conventional process and five process modifications to show optimization strategy.

Laser-induced breakdown spectroscopy (LIBS) has drawn more attention as a new technique for in situ detection of seawater, especially for hydrothermal areas. In order to evaluate the focusing geometry effect on laser-induced plasma in bulk water, four focusing arrangements were tried out with a single lens as well as with a double-lens combination. We demonstrated that, for the same transmission distance in water, the double-lens combination with shorter effective focal length generated more condensed plasma, as shown by the spectroscopic and fast imaging results. Accordingly, the moving breakdown phenomenon significantly decreased with well-improved LIBS intensity, signal-to-noise ratio, and stability. The plasma emissions evidently attenuated along the laser transmission due to the strong absorption effect of the water medium. Based on the acquired results, the performance of a practical detection window was evaluated by combining the regular lens with a customized lens-shaped optical window, and a positive outcome was also reached. The obtained results suggested that improved LIBS detection could be easily achieved via settling another lens window to LIBS system, which is considered helpful for better in situ submarine application.

In this work, a comparative study and evaluation of CO2 capture process using monoethanolamine (MEA) and diethanolamine (DEA) is reported. Ten different process configurations from a power plant are simulated and compared in terms of the total equivalent work and the reboiler duty. Process flowsheet modifications present a good performance with respect to the reduction of energy consumption. It is carried out with a 0.38–4.61% of reduction for MEA and 0.27–4.5% for DEA. Furthermore, a detailed analysis is presented to study the effect of four significant parameters in capture process, including various temperatures, pressures, and concentrations. This analysis presents the influence of the interaction between the solvent and the process, which is essential in post-combustion process design to develop an optimization strategy.

The influence of laser wavelength on the characteristics of laser-induced breakdown spectroscopy (LIBS) in bulk water was investigated by using 532- and 1064-nm lasers. We demonstrated that higher laser energy does not lead to higher LIBS signals because of the strong plasma shielding occurring at high laser energies, as shown by the spectroscopic and fast imaging results in this work. At threshold energies of 100% breakdown probability, the 1064 nm beam could induce a plasma with higher electron density and temperature than the 532 nm beam, which leads to higher signal-to-noise ratios and longer lifetimes of the emission lines.

Axial focusing arrangement effects on collinear dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) in a bulk solution were investigated by spectra and fast images. By properly defocusing the second laser pulse beyond the first laser formed bubble (LFB), brighter and larger plasmas could be produced due to higher breakdown efficiency and higher expansion efficiency. It is attributed to a distinct mechanism of underwater DP-LIBS that the plasma mostly forms at the bubble-water interface and then expands into the gaseous LFB. The results show that optimization of the axial focusing arrangement in underwater collinear DP-LIBS enables significant emission enhancements with relatively low laser energies.

In this work, a systematic simulation study of post-combustion CO2 capture process is presented. Including six individual process modifications and six combinations of process modifications, 13 different process configurations are simulated using aqueous monoethanolamine (MEA) and diethanolamine (DEA) solutions. Process modifications presented a good performance with respect to the reduction of energy consumption. It is carried out with 3.45% to 13.45% of reduction for MEA and 2.36% to 14.10% for DEA. Furthermore, a detailed analysis is presented to study the effect of three significant parameters in capture process, i.e., CO2 loading of lean amine solvent, pinch of heat exchanger and stripper pressure. This work presents the influence of the combination of solvent and process, as well as the combination of different processes on energy consumption, which are essential in post-combustion process design to make optimisation strategy.

Laser focusing geometry effects on plasma emissions in bulk water were investigated with five focusing angles ranging from 11.9° to 35.4°. Fast imaging and space-resolved spectroscopy techniques were used to observe the plasma emission distributions and fluctuations. We demonstrated that by increasing the focusing angle, discrete and irregular plasma formed in multiple sites could be turned into continuous and stable plasma with single core fixed at the laser focal point. This indicates the key role of laser focusing angle in the stabilization of plasma positions, which is crucial to the improvement of laser-induced breakdown spectroscopy repeatability in bulk water.

Temporal and spatial evolutions of the laser-induced plasma in bulk water are investigated using fast imaging and emission spectroscopic techniques. By tightly focusing a single-pulse nanosecond Nd: YAG laser beam into the bulk water, we generate a strongly expanded plasma with high reproducibility. Such a strong expanding plasma enables us to obtain well-resolved spectral lines by means of position-selective detection; hence, the time-gated detector becomes abdicable. The present results suggest not only a possible non-gated approach for underwater laser-induced breakdown spectroscopy but also give an insight into the plasma generation and expansion in bulk water.