Temporally Local Weighting-Based Phase-Locked Time-Shift Data Augmentation Method for Fast-Calibration SSVEP-BCI.

Various training-based spatial filtering methods have been proposed to decode steady-state visual evoked potentials (SSVEPs) efficiently. However, these methods require extensive calibration data to obtain valid spatial filters and temporal templates. The time-consuming data collection and calibration process would reduce the practicality of SSVEP-based brain-computer interfaces (BCIs). Therefore, we propose a temporally local weighting-based phase-locked time-shift (TLW-PLTS) data augmentation method to augment training data for calculating valid spatial filters and temporal templates. In this method, the sliding window strategy using the SSVEP response period as a time-shift step is to generate the augmented data, and the time filter which maximises the temporally local covariance between the original template signal and the sine-cosine reference signal is used to suppress the temporal noise in the augmented data. For the performance evaluation, the TLW-PLTS method was incorporated with state-of-the-art training-based spatial filtering methods to calculate classification accuracies and information transfer rates (ITRs) using three SSVEP datasets. Compared with state-of-the-art training-based spatial filtering methods and other data augmentation methods, the proposed TLW-PLTS method demonstrates superior decoding performance with fewer calibration data, which is promising for the development of fast-calibration BCIs.

Metal-Metal Bonding Process Research Based on Xgboost Machine Learning Algorithm.

Conventionally, the optimization of bonding process parameters requires multi-parameter repetitive experiments, the processing of data, and the characterization of complex relationships between process parameters, and performance must be achieved with the help of new technologies. This work focused on improving metal-metal bonding performance by applying SLJ experiments, finite element models (FEMs), and the Xgboost machine learning (ML) algorithm. The importance ranking of process parameters on tensile-shear strength (TSS) was evaluated with the interpretation toolkit SHAP (Shapley additive explanations) and it optimized reasonable bonding process parameters. The validity of the FEM was verified using SLJ experiments. The Xgboost models with 70 runs can achieve better prediction results. According to the degree of influence, the process parameters affecting the TSS ranked from high to low are roughness, adhesive layer thickness, and lap length, and the corresponding optimized values were 0.89 µm, 0.1 mm, and 27 mm, respectively. The experimentally measured TSS values increased by 14% from the optimized process parameters via the Xgboost model. ML methods provide a more accurate and intuitive understanding of process parameters on TSS.

Cross-Subject Transfer Method Based on Domain Generalization for Facilitating Calibration of SSVEP-Based BCIs.

In steady-state visual evoked potential (SSVEP)-based brain-computer interfaces (BCIs), various spatial filtering methods based on individual calibration data have been proposed to alleviate the interference of spontaneous activities in SSVEP signals for enhancing the SSVEP detection performance. However, the time-consuming calibration session would increase the visual fatigue of subjects and reduce the usability of the BCI system. The key idea of this study is to propose a cross-subject transfer method based on domain generalization, which transfers the domain-invariant spatial filters and templates learned from source subjects to the target subject with no access to the EEG data from the target subject. The transferred spatial filters and templates are obtained by maximizing the intra- and inter-subject correlations using the SSVEP data corresponding to the target and its neighboring stimuli. For SSVEP detection of the target subject, four types of correlation coefficients are calculated to construct the feature vector. Experimental results estimated with three SSVEP datasets show that the proposed cross-subject transfer method improves the SSVEP detection performance compared to state-of-art methods. The satisfactory results demonstrate that the proposed method provides an effective transfer learning strategy requiring no tedious data collection process for new users, holding the potential of promoting practical applications of SSVEP-based BCI.

Latency Aligning Task-Related Component Analysis Using Wave Propagation for Enhancing SSVEP-Based BCIs.

Due to the high robustness to artifacts, steady-state visual evoked potential (SSVEP) has been widely applied to construct high-speed brain-computer interfaces (BCIs). Thus far, many spatial filtering methods have been proposed to enhance the target identification performance for SSVEP-based BCIs, and task-related component analysis (TRCA) is among the most effective ones. In this paper, we further extend TRCA and propose a new method called Latency Aligning TRCA (LA-TRCA), which aligns visual latencies on channels to obtain accurate phase information from task-related signals. Based on the SSVEP wave propagation theory, SSVEP spreads from posterior occipital areas over the cortex with a fixed phase velocity. Via estimation of the phase velocity using phase shifts of channels, the visual latencies on different channels can be determined for inter-channel alignment. TRCA is then applied to aligned data epochs for target recognition. For the validation purpose, the classification performance comparison between the proposed LA-TRCA and TRCA-based expansions were performed on two different SSVEP datasets. The experimental results illustrated that the proposed LA-TRCA method outperformed the other TRCA-based expansions, which thus demonstrated the effectiveness of the proposed approach for enhancing the SSVEP detection performance.

Electrical Conduction Characteristic of a 2D MXene Device with Cu/Cr2C/TiN Structure Based on Density Functional Theory.

The electronic structure and the corresponding electrical conductive behavior of the Cu/Cr2C/TiN stack were assessed according to a newly developed first-principle model based on density functional theory. Using an additional Cr2C layer provides the metal-like characteristic of the Cu/Cr2C/TiN stack with much larger electrical conduction coefficients (i.e., mobility, diffusivity, and electrical conductivity) than the conventional Ag/Ti3C2/Pt stack due to the lower activation energy. This device is therefore capable of offering faster switching speeds, lower programming voltage, and better stability and durability than the memristor device with conventional Ti3C2 MXene.

In-Memory Logic Operations and Neuromorphic Computing in Non-Volatile Random Access Memory.

Recent progress in the development of artificial intelligence technologies, aided by deep learning algorithms, has led to an unprecedented revolution in neuromorphic circuits, bringing us ever closer to brain-like computers. However, the vast majority of advanced algorithms still have to run on conventional computers. Thus, their capacities are limited by what is known as the von-Neumann bottleneck, where the central processing unit for data computation and the main memory for data storage are separated. Emerging forms of non-volatile random access memory, such as ferroelectric random access memory, phase-change random access memory, magnetic random access memory, and resistive random access memory, are widely considered to offer the best prospect of circumventing the von-Neumann bottleneck. This is due to their ability to merge storage and computational operations, such as Boolean logic. This paper reviews the most common kinds of non-volatile random access memory and their physical principles, together with their relative pros and cons when compared with conventional CMOS-based circuits (Complementary Metal Oxide Semiconductor). Their potential application to Boolean logic computation is then considered in terms of their working mechanism, circuit design and performance metrics. The paper concludes by envisaging the prospects offered by non-volatile devices for future brain-inspired and neuromorphic computation.

Population genetic structure of Bellamya aeruginosa (Mollusca: Gastropoda: Viviparidae) in China: weak divergence across large geographic distances.

Bellamya aeruginosa is a widely distributed Chinese freshwater snail that is heavily harvested, and its natural habitats are under severe threat due to fragmentation and loss. We were interested whether the large geographic distances between populations and habitat fragmentation have led to population differentiation and reduced genetic diversity in the species. To estimate the genetic diversity and population structure of B. aeruginosa, 277 individuals from 12 populations throughout its distribution range across China were sampled: two populations were sampled from the Yellow River system, eight populations from the Yangtze River system, and two populations from isolated plateau lakes. We used seven microsatellite loci and mitochondrial cytochrome oxidase I sequences to estimate population genetic parameters and test for demographic fluctuations. Our results showed that (1) the genetic diversity of B. aeruginosa was high for both markers in most of the studied populations and effective population sizes appear to be large, (2) only very low and mostly nonsignificant levels of genetic differentiation existed among the 12 populations, gene flow was generally high, and (3) relatively weak geographic structure was detected despite large geographic distances between populations. Further, no isolation by linear or stream distance was found among populations within the Yangtze River system and no signs of population bottlenecks were detected. Gene flow occurred even between far distant populations, possibly as a result of passive dispersal during flooding events, zoochoric dispersal, and/or anthropogenic translocations explaining the lack of stronger differentiation across large geographic distances. The high genetic diversity of B. aeruginosa and the weak population differentiation are likely the results of strong gene flow facilitated by passive dispersal and large population sizes suggesting that the species currently is not of conservation concern.

Effects of Pb(â ¡) exposure on Chlorella protothecoides and Chlorella vulgaris growth, malondialdehyde, and photosynthesis-related gene transcription.

Greater exposure to Pb(Ⅱ) increases the likelihood of harmful effects in the environment. In this study, the aquatic unicellular alga Chlorella protothecoides (C. protothecoides) and Chlorella vulgaris (C. vulgaris) were chosen to assess the acute and chronic toxicity of Pb(Ⅱ) exposure. Results of the observations show dose-response relationships could be clearly observed between Pb(Ⅱ) concentration and percentage inhibition (PI). Exposure to Pb(Ⅱ) increased malondialdehyde (MDA) content by up to 4.22 times compared with the control, suggesting that there was some oxidative damage. ANOVA analysis shows that Pb(Ⅱ) decreased chlorophyll (chl) content, indicating marked concentration-dependent relationships, and the lowest levels of chl a, chl b, and total-chl were 14.53, 18.80, and 17.95% of the controls, respectively. A real-time PCR assay suggests the changes in transcript abundances of three photosynthetic-related genes. After 120 h exposure Pb(Ⅱ) reduced the transcript abundance of rbcL, psaB, and psbC, and the relative abundances of the three genes of C. protothecoides and C. vulgaris in response to Pb(Ⅱ) were 54.66-98.59, 51.68-95.59, 37.89-95.48, 36.04-94.94, 41.19-91.20, and 58.75-96.80% of those of the controls, respectively. As for 28 d treatments, the three genes displayed similar inhibitory trend. This research provides a basic understanding of Pb(Ⅱ) toxicity to aquatic organisms.

Acute and chronic toxic effects of bisphenol A on Chlorella pyrenoidosa and Scenedesmus obliquus.

The acute and chronic toxic effects of Bisphenol A (BPA) on Chlorella pyrenoidosa (C. pyrenoidosa) and Scenedesmus obliquus (S. obliquus) were not well understood. The indoor experiments were carried out to observe and analyze the BPA-induced changes. Results of the observations showed that in acute tests BPA could significantly inhibit the growth of both algae, whereas chronic exposure hardly displayed similar trend. Superoxide dismutase (SOD) and Catalase (CAT) activities of both algae were promoted in all the treatments. Chlorophyll a synthesis of the two algae exhibited similar inhibitory trend in short-term treatments, and in chronic tests C. pyrenoidosa hardly resulted in visible influence, whereas in contrast, dose-dependent inhibitory effects of S. obliquus could be clearly observed. The experimental results indicated that the growth and Chlorophyll a syntheses of S.obliquus were more sensitive in response to BPA than that of C. pyrenoidosa, whereas for SOD andCAT activities, C. pyrenoidosa was more susceptible. This research provides a basic understanding of BPA toxicity to aquatic organisms.

Acute and chronic toxic effects of chloramphenicol on Scenedesmus obliquus and Chlorella pyrenoidosa.

The acute and chronic toxicological effects of Chloramphenicol (CAP) on Scenedesmus obliquus and Chlorella pyrenoidosa are not well understood. The indoor experiments were carried to observe and analyze the CAP induced changes. Results of the observations have showed that CAP exposure could significantly inhibit the growth of Scenedesmus obliquus in almost all the treated groups, while Chlorella pyrenoidosa exhibited less sensitivity. Chlorophyll-a syntheses of Scenedesmus obliquus were all inhibited by CAP exposure, while Chlorella pyrenoidosa displayed obvious stimulation effect. Catalase (CAT) and Superoxide dismutase (SOD) activities of both algae were promoted in all the treatments. The experimental results indicated that the growth and Chlorophyll-a syntheses of Scenedesmus obliquus were more sensitive in response to CAP exposure than that of Chlorella pyrenoidosa. While for CAT and SOD activities, Chlorella pyrenoidosa showed more susceptible. This research provides a basic understanding of CAP toxicity to aquatic organisms.

Roles of plasmid-encoded proteins, EseH, EseI and EscD in invasion, replication and virulence of Edwardsiella ictaluri.

Native plasmids pEI1 and pEI2 were detected in Edwardsiella ictaluri HSN-1 isolated from diseased yellow catfish (Pelteobagrus fulvidraco). EseH encoded by pEI1 and other two proteins, EseI and EscD, encoded by pEI2, were found with homology to type III secretion system (T3SS) proteins. To investigate their roles in pathogenesis, the native plasmids were cured based on plasmid incompatibility by introducing a Kan positive and SacB negative selection marker into gene spacer of the native plasmids. Mutants with the deletion of the target genes were obtained by reverse PCR and self-ligation, and all mutants were examined for their virulence effect in yellow catfish. Compared with the HSN-1 strain, the two mutants ΔeseH and ΔeseI were attenuated, while mutant ΔescD had increased virulence with higher Competitive Index (CI) value. The adherence and invasion assays on fish EPC cells indicated that ΔeseH and ΔeseI had decreased ability in adherence. Using E. tarda as surrogate, EseH and EseI were detected in culture supernatants, but EscD was not, with the secretion of EseH depending on T3SS. In addition, EseH and EseI were found translocated into host cells, and by means of subcellular fractionation, EseH was localized in membrane fraction of ZF4 cells, and EseI in the cytosol fraction. Hence, the role of these three genes in adherence, invasion and cellular replication was revealed from the pathogenic bacterium E. ictaluri.

Toxicity assessment of Chlorella vulgaris and Chlorella protothecoides following exposure to Pb(II).

The short- and long-term toxic effects of Pb(II) exposure on Chlorella vulgaris (C. vulgaris) and Chlorella protothecoides (C. protothecoides) were not well understood. The lab study was performed to observe the Pb(II) exposure induced changes. Results of the observations show: (1) higher level of Pb(II) (50 or 80mgL(-1)) could significantly inhibit the growth and chlorophyll a synthesis of both algae in almost all the treatments and dose-response relationships could be clearly observed, (2) the range of EC50 values (24-120h, 67.73-172.45mgL(-1)) indicated that Pb(II) had a relatively limited short-term toxicity to the two algae, while long-term tests (7-28d, 50.41-63.91mgL(-1)) displayed higher toxicity and (3) SOD and CAT activities of both algae after exposed to medium level of Pb(II) were significantly promoted, and their response might be more susceptible in short-term exposure. This research provides a basic understanding of Pb(II) toxicity to aquatic organisms.

Induction of annexin by heavy metals and jasmonic acid in Zea mays.

Plant annexins are Ca(2+)- and phospholipid-binding proteins forming an evolutionary conserved multi-gene family. They are implicated in the regulation of plant growth, development, and stress responses. With the availability of the maize genome sequence information, we identified 12 members of the maize annexin genes. Analysis of protein sequence and gene structure of maize annexins led to their classification into five different orthologous groups. Expression analysis by RT-PCR revealed that these genes are responsive to heavy metals (Ni, Zn, and Cd). The maize annexin genes were also found to be regulated by Ustilago maydis and jasmonic acid. Additionally, the promoter of the maize annexin gene was analyzed for the presence of different stress-responsive cis-elements, such as ABRE, W-box, GCC-box, and G-box. RT-PCR and microarray data show that all 12 maize annexin genes present differential, organ-specific expression patterns in the maize developmental steps. These results indicate that maize annexin genes may play important roles in the adaptation of plants to various environmental stresses.

Molecular cloning, tissue distribution, and ontogenetic expression of ghrelin and regulation of expression by fasting and refeeding in the grass carp (Ctenopharyngodon idellus).

Ghrelin is a recently discovered brain-gut peptide in fish and mammals. It has two main physiological functions-stimulating growth hormone secretion and regulating appetite. To investigate the biological function of ghrelin in appetite regulation in grass carp Ctenopharyngodon idellus, the full-length cDNA sequence of the ghrelin gene was obtained by RT-PCR and rapid amplification of cDNA ends methods. Homology analysis indicated that ghrelin cDNA sequence is conserved in teleosts. The grass carp ghrelin gene consists of four exons and three introns, which is similar to that of common carp, zebrafish and humans. Real-time quantitative PCR was used to detect ghrelin mRNA expression in the study. In adult tissues, high levels of gene expression were found in the foregut; moderate levels in the muscle, liver, hypothalamus, white adipose tissue, midgut, heart, and pituitary; and lower levels in the three other examined tissues. During embryonic development, ghrelin mRNA expression could be detected as early as fertilized egg stage and displayed an increase in expression until heart appearance stage. After hatching, the level of ghrelin mRNA expression decreased sharply to the lowest level at 1 day post-hatching (dph), then increased to a higher level at 7 dph and subsequently decreased to a relative stabilized level from 15 to 35 dph. The ghrelin mRNA expression was significantly upregulated in the brain and intestine during fasting and was downregulated after refeeding. The results suggest that ghrelin mRNA expression has obvious tissue specificity and may have a role in appetite regulation in grass carp.

Purification and characterization of 6-phosphogluconate dehydrogenase (6-PGD) from grass carp (Ctenopharyngodon idella) hepatopancreas.

6-Phosphogluconate dehydrogenase (6-PGD, E.C.: 1.1.1.44) was purified and characterized from the hepatopancreas of grass carp (Ctenopharyngodon idella) for the first time. Grass carp represents the second largest aquaculture industry in the world after silver carp, constituting 14.7% of the world aquaculture production, with an average annual increase of 14% in China, mainly as a source of food. The purification procedure involved a single 2', 5'-ADP-Sepharose 4B affinity chromatographic step by using different elution buffers. The enzyme was purified 309-fold with a specific activity of 5.259 U/mg protein and yield of 68%. The purity and subunit molecular weights of the 6-PGD were checked on SDS-PAGE and purified enzyme showed a single band on the gel. The subunit molecular mass was 57 kDa, with an optimum pH, temperature and ionic strength at 7.96, 50 degrees C and 100 mM Tris-HCl, respectively. The Km values of 6-PGA and NADP+ were 0.019 and 0.0052 mM, respectively, while Vm of 6-PGA and NADP+ was 0.69 U/ml. Dissociation constants (Ki) for 6-PGA and NADP+ were 2.05 and 0.12 mM, respectively. NADPH inhibited the enzyme in a competitive manner and its Ki value was 0.032 mM. The Cu2+, Zn2+, Cd2+ and Al3+ showed inhibitory effects on the enzyme with IC50 values of 0.293, 0.099, 0.045 and 1.526 mM, respectively. All tested metals inhibited the enzyme in a competitive manner, indicating that these metals might be toxic even at low concentrations for the 6-PGD. As the fish is one of valuable foodstuff of animal sources for human consumption, under certain environmental conditions, metal ions accumulated in fish up to a lethal concentration may be harmful for human health. Therefore, it is impending to reduce the concentration of metal ions in contaminated lakes and rivers for fishery and also for human health.

[Control effect of different covering patterns on indigenous nutrient release from sediment].

A laboratory simulation experiment was conducted to study the release of sediment phosphorous and nitrogen under the effects of coating the sediment with plastic, clinoptilolite, calcite, quartz sand, and calcium nitrate, aimed to provide scientific basis and technical support to control the sediment nutrient release under the background of water environment pollution by different concentrations of nitrogen and phosphorus. The control efficacy of test coating materials for sediment total phosphorous release was in the order of plastic > calcium nitrate > clinoptilolite > calcite > quartz sand, and that for sediment total nitrogen release was in the order of clinoptilolite > plastic > calcite > quartz sand > calcium nitrate. As for the release of sediment NO(3-)-N, the control efficacy of test coating materials was calcium nitrate > quartz sand > clinoptilolite > calcite > plastic coating; whereas for the release of sediment NH(4+)-N, the sequence was calcium nitrate > plastic coating > clinoptilolite > calcite > quartz sand. Water temperature had definite relativity to the sediment nutrient release. With the increase of water temperature, the concentrations of water total phosphorous and nitrogen and NO(3-)-N increased, while the concentration of water NH(4+)-N presented a declining trend.

Aldehyde dehydrogenase protein superfamily in maize.

Maize (Zea mays ssp. mays L.) is an important model organism for fundamental research in the agro-biotechnology field. Aldehydes were generated in response to a suite of environmental stresses that perturb metabolism including salinity, dehydration, desiccation, and cold and heat shock. Many biologically important aldehydes are metabolized by the superfamily of NAD(P)(+)-dependent aldehyde dehydrogenases. Here, starting from the database of Z. mays, we identified 28 aldehyde dehydrogenase (ALDH) genes and 48 transcripts by the in silico cloning method using the ALDH-conserved domain amino acid sequence of Arabidopsis and rice as a probe. Phylogenetic analysis shows that all 28 members of the ALDH gene families were classified to ten distinct subfamilies. Microarray data and quantitative real-time PCR analysis reveal that ZmALDH9, ZmALDH13, and ZmALDH17 genes involve the function of drought stress, acid tolerance, and pathogens infection. These results suggested that these three ZmALDH genes might be potentially useful in maize genetic improvement.

Molecular characterization of cholecystokinin in grass carp (Ctenopharyngodon idellus): cloning, localization, developmental profile, and effect of fasting and refeeding on expression in the brain and intestine.

Cholecystokinin (CCK) is a multi-functional brain-gut peptide in fish and mammals. To investigate the role of CCK in appetite regulation in fish, a 770-bp full-length cDNA sequence of CCK gene was obtained by RT-PCR and rapid amplification of cDNA ends methods in grass carp Ctenopharyngodon idellus. Homology analysis showed that the CCK cDNA sequence of grass carp had the highest similarity (90 %) to that of goldfish Carassius auratus and a higher similarity (>70 %) to those of other teleosts than to mammals. The PCR amplification using genomic DNA identified that the CCK gene of grass carp was comprised of three exons and two introns. Real-time quantitative PCR was used to detect CCK mRNA expression in adult tissues. High levels of gene expression were found in the hypothalamus and pituitary; moderate levels in the intestine, muscle and white adipose tissue; and low levels in other tissues. During early development (i.e., fertilized eggs to 35-day post-hatching larvae) the levels of CCK mRNA expression were higher during embryonic developmental stages than during post-hatch larval stages. Fasting decreased CCK mRNA expression levels in the brain and intestine, whereas refeeding resulted in an increase of expression. The results suggest that CCK mRNA expression has obvious tissue specificity and may have a role in feed intake regulation in grass carp.

Ecotoxicological effects of decabromodiphenyl ether and cadmium contamination on soil microbes and enzymes.

The ecotoxicological effects of decabromodiphenyl ether (BDE209) and cadmium (Cd) contamination on soil culturable microbial population, enzyme activity and bacterial community structure were investigated. Results of the indoor incubation test runs performed on many series of control and contaminated soil samples have demonstrated some notable toxic effects due to long term exposure to either or both contaminants. The two contaminants produced notable yet different toxic effects on the test microbes; the population of the exposed species generally declined according to certain dose-response relationships. The soil culturable microbial population and enzyme activity data show that the sensitivity to one or both contaminants followed the order of: bacteria>fungi>actinomycete and urease>saccharase, respectively. The interaction between BDE209 and Cd was dependent on both the exposure dose and time and that the joint toxic effects were synergistic, antagonistic or additive. The PCR-DGGE analysis data of species composition and richness suggest the synergistic combined effects on bacterial community structure during the 30d exposure. Pseudomonas tuomuerensis strain CCM 7280 and Pseudomonas alcaliphila strain AL15-21 were enriched, indicating these species might be major functional populations and highly tolerant. Such observations have provided the useful information of potential ecotoxicological effects of BDE209 and Cd contamination in the environment.

Synergetic degradation of Fe/Cu/C for groundwater polluted by trichloroethylene.

This study investigated the enhancement of synergetic degradation of Fe/Cu/C (Fe: commercial iron, Cu: solid product of Fe reacted with CuSO(4), C: carbon powder) for simulated groundwater contaminated by trichloroethylene (TCE). Zero valent iron (ZVI) as a reducing agent was proved to be effective for TCE removal. The Fe/Cu/C system resulted in higher reduction efficiency as a result of the synergetic role of Fe/Cu and Fe/C microelectrode than the Fe (ZVI) or Fe/Cu system, and the half-life was only about 0.4 h. When m(Fe) achieved 12.5 g L(-1), the residual concentration of TCE almost leveled off. Fe:Cu = 10:1 or m(C) = 0.0086 g can induce the optimum function for TCE degradation. A neutral condition was appropriate for TCE degradation, and an acidic system slightly favored TCE dechlorination compared with an alkaline system. GC/MS analysis indicated that TCE was dechlorinated to 1,1-dichloroethene (1,1-DCE), cis-1,2-dichloroethene (cis-DCE) and vinyl chloride (VC), and 1,1-DCE might be the precursor. Fe/Cu/C reduction is a highly promising technique for TCE removal, and it is an excellent alternative to enhance TCE reductive dechlorination.