Global Navigation Satellite System-Acoustic (GNSS-A) technology has been widely used in ocean engineering and ocean environmental science. Accurate sound travel time modeling is essential for GNSS-A ...seafloor positioning. Currently, half of the two-way travel time (TWTT) has been used as an approximation for the one-way travel time (OWTT). In this work, the time error of the approximate OWTT is investigated under different survey configurations, and a sequential GNSS-A seafloor positioning method using the extended Kalman filter (EKF) is developed to investigate the impact of sound travel time modeling. Simulations show that the time error induced under the static survey configuration is less than 0.6 ms; the time error induced under the circle survey configuration with a stable inclination angle is stable, but the time error of the line survey configuration can reach 28 ms. As confirmed through field experiments, sequential GNSS-A seafloor positioning using TWTT modeling is more stable than OWTT modeling. The positioning residuals of TWTT modeling are similar to those of OWTT modeling under the circle configuration but at least 2 times less than those of OWTT modeling under the line survey configuration. Furthermore, the average positioning residuals of OWTT and TWTT modeling can be greatly reduced for a survey configuration combining circular and linear tracks. These findings provide a feasible method for improving the precision and efficiency of GNSS-A seafloor positioning.
•Vibration data of converter transformers under different no-load conditions are collected.•Vibration characteristics of converter transformers are investigated under different no-load ...conditions.•Analysis of vibration characteristics provides a valuable reference for vibration state assessment.
For lack of study on the vibration characteristics of converter transformers, this paper studied the vibration signal analysis method and investigated the vibration characteristics of converter transformers during the commissioning of a ±800 kV converter station. The study comprised two parts including no-load and load conditions. In Part I, converter transformers are under no-load conditions. Vibration data are collected under conditions of no-load closing, no-load voltage rise with converters, and no-load voltage rise with DC lines. The vibration characteristics and mechanisms are studied based on the collected data. Several different vibration characteristics are introduced. Vibration power entropy, vibration total harmonic distortion, and recurrence rate are calculated under no-load conditions. Results show that vibration amplitude, vibration total harmonic distortion, and recurrence rate are sensitive to no-load closing. Vibration power entropy is sensitive to no-load voltage rise with DC lines. All these vibration characteristics are sensitive to converter unlocking. These characteristics show different and significant changes under different no-load conditions. Thus, it is vital to choose appropriate vibration characteristics when assessing the vibration state of converter transformers under different operating conditions. The study examines the vibration characteristics’ physical meanings and their changing mechanisms. It also summarizes distribution intervals and typical values of vibration characteristics. This research reveals the vibration regularity and corresponding mechanism. It provides a reference for vibration state assessment and early fault detection of ±800 kV converter transformers under no-load conditions.
•Nonstationary models that incorporate climatic variables and reservoir index are constructed.•The nonstationary models provide a better fitting of nonstationary flood and low flow ...series.•Nonstationary frequency analysis of flood and low flow in upper of Huaihe River Basin are conducted.•Climatic and reservoir impacts are related to nonstationarity of flood and low flow respectively.
Conventional water infrastructure designs for flood and low flows are usually based on the assumption of stationarity of extreme events. However, recent evidence suggests that the influences of climate variability and human activities have made the hypothesis of stationarity questionable. In this study, we used the generalized additive models for location, scale, and shape (GAMLSS) to construct a nonstationary model in which the parameters of the selected distributions were modelled as a function of climatic variables (i.e., climate indices and precipitation) and/or the reservoir index (RI). The nonstationary models were then used to analyse annual flood and low flow frequency at four hydrological stations in the upper reaches of the Huaihe River Basin, including Dapoling (DPL), Changtaiguan (CTG), Zhuganpu (ZGP), and Xixian (XX) stations. Annual floods were represented by the maximum daily streamflow in each year, and low flows were represented by the 95th quantile of the daily streamflow (Q95) in each year. The change point and trend analysis revealed that the flood series of the ZGP station and the low flow series of the DPL and XX stations exhibited significant downward and upward trends (p < 0.1)), respectively. The low flow series of the ZGP station showed a significant change point in 1980 (p < 0.1). GAMLSS modelling results showed that, in comparison with stationary models, nonstationary models that included precipitation and the Arctic Oscillation climate index as covariates for the gamma distribution location parameter provided a superior description of the flood series at the four stations. Nonstationary models that incorporated precipitation and/or RI as covariates for the Weibull distribution parameters fit the low flow series better than stationary models at all stations. Furthermore, we found that nonstationary models outperformed stationary models in terms of flood frequency analysis, covering all flood observation points and capturing the generally decreasing trend in flood series, as well as a decrease in the scatter of estimated flood value magnitudes. For the low flow frequency analysis, the comparison results showed that the nonstationary and stationary models performed identically for the DPL, CTG, and XX stations, where no significant change point was detected. However, for the ZGP station, where a significant change point was detected, the nonstationary models performed better than the stationary models and could accurately capture the changes in the magnitude of the estimated low flow values before and after the change point. Overall, the proposed nonstationary model can serve as a tool for nonstationary frequency analysis of flood and low flow series under the influence of climate variability and reservoir regulations, thus providing a reference for regional water infrastructure design.
As one of the most popular expression systems, recombinant protein expression in Pichia pastoris relies on the AOX1 promoter (P
) which is strongly induced by methanol. However, the toxic and ...inflammatory nature of methanol restricts its application, especially in edible and medical products. Therefore, constructing a novel methanol-free system becomes necessary. The kinases involved in P
activation or repression by different carbon sources may be promising targets.
We identified two kinase mutants: Δgut1 and Δdak, both of which showed strong alcohol oxidase activity under non-methanol carbon sources. Based on these two kinases, we constructed two methanol-free expression systems: Δgut1-HpGCY1-glycerol (P
induced by glycerol) and Δdak-DHA (P
induced by DHA). By comparing their GFP expression efficiencies, the latter one showed better potential. To further test the Δdak-DHA system, three more recombinant proteins were expressed as examples. We found that the expression ability of our novel methanol-free Δdak-DHA system was generally better than the constitutive GAP promoter, and reached 50-60 % of the traditional methanol induced system.
We successfully constructed a novel methanol-free expression system Δdak-DHA. This modified expression platform preserved the favorable regulatable nature of P
, providing a potential alternative to the traditional system.
The interactions between osteogenic proteins and the biomaterial surface are crucial to the application of biomaterials, in which the conformational or orientational change of the adsorbed protein on ...the solid surfaces is one of the most important interactions other than the protein adsorption. Although some progress has been made in the mechanism of protein adsorption on the surface of hydroxyapatite (HAP) in recent years, there is still insufficient atomistic/molecular information about the conformation and orientation of proteins upon adsorbing on solid surfaces. In this study, different orientations and conformations of bone morphological protein-2 (BMP-2) adsorbed on the surface of HAP were calculated through the protein–solid surface docking approach; the relationship between optimal adsorption and biological activity of BMP-2 was investigated by applying a combination of molecular dynamic simulation (MD) and steered molecular dynamic simulation (SMD). Two optimal adsorption conformers were screened out according to the docking results on the basis of orientations of BMP-2 with different epitopes. Subsequent MD and SMD results showed that the knuckle epitope of BMP-2 was easier to adsorb on the surface of HAP(100) than the wrist epitope accompanying certain conformational changes. Such an absorption mode led to the wrist epitope of BMP-2 being exposed to the environment and then being identified/interacted with type I receptors on the stem cell membrane, which further induces the differentiation of stem cells into osteoblasts. Current simulation provided a theoretical high-throughput screening method for the protein–biomaterial adsorption states. It can be extended to more research on different protein adsorptions on the surface of different materials. The simulation results provided more information at the molecular and atomic levels to further interpret the mechanism of osteoinductivity from the perspective of growth factor adsorption. Meanwhile, we believe that it should be a meaningful attempt to screen biomaterial key factors by the high-throughput method, which might become a promising way to develop or optimize new biomaterials.
In order to improve the flame retardancy of poly(ethylene terephthalate) (PET) and maintain its excellent foamability, nanosilica (nano-SiO2), and zinc diethyl hypophosphite (ZDP) were selected as ...synergistic flame retardants, and pyromellitic dianhydride (PMDA) was used as a chain extender to carry out flame retardant and chain extension modification of PET simultaneously. The flame retardancy and flame-retardant mechanism of modified PET were characterized by limiting oxygen index, vertical combustion test, thermogravimetric analysis, and SEM. Dynamic rheological test and DSC were used to analyze the rheological and thermal properties. The foaming ability was also studied by batch foaming experiments. The test results indicated that nano-SiO2 and ZDP had a synergistic effect, which could significantly improve flame retardancy of PET. The vertical combustible grade of modified PET reached V-0 grade, and the limiting oxygen index increased from 21% to about 30%. The role of nano-SiO2 on the flame retardancy of PET was mainly to increase compactness and strength of the carbon layer, which could block combustible gas produced by the pyrolysis of PET and resist dripping behavior. At the same time, the addition of nano-SiO2 increased the crystallization temperature and crystallinity of PET. Otherwise, nano-SiO2 could act as a bubble-nucleating agent and improve the foaming ability of modified PET. When the addition amount was 1 wt%, not only did the maximum foaming ratio increase but the foaming temperature zone was also widened from 225°C-235°C to 225°C-250°C. Finally, a flame-retardant PET system with good foaming property was proposed.
•A comprehensive framework for quantifying the climatic and anthropogenic influences on river hydrological health is proposed.•Human activities significantly aggravate the degradation of river ...hydrological health for the studied catchment.•Widespread artificial water withdrawal and reservoir operation are the two crucial human activities.•Adequate rainfall maintains the river hydrological health at a good status in the 1990 s.
Climate change and human activities have together altered the river hydrological regime and consequently threatened the health of river ecosystems. Quantifying the impact of climate change and human activities on river hydrological health regimes is essential for water resource management and river ecology protection. Although previous studies have analysed the hydrologic alterations using some indicators, separating effects of climate change and human activities on river hydrological health is needed for developing adaptive measures to protect the ecosystem of river basins. In this study, a comprehensive assessment framework for quantifying climatic and anthropogenic influences on river hydrological health variation was proposed. The framework consists of the following steps: (1) the reconstruction of natural river streamflow using the variable infiltration capacity (VIC) hydrological model, (2) calculation of river hydrological health through the ecological flow threshold method, and (3) quantification of the impacts of climate change and human activities on river hydrological health using the ‘observed–simulated’ comparison approach. The semi-arid Laohahe Basin in northern China, which consists of three human-influenced catchments (Taipingzhuang, Chifeng, and Xinglongpo) and one natural catchment (Xiquan), was selected as the case study area. The case study demonstrated that the proposed procedure is efficient in quantifying climatic and anthropogenic influences on river hydrological health. The results revealed that the hydrological health level has significantly declined in the three human-influenced catchments for the human-influenced period (1980–2016), particularly in the 2000 s and 2010 s, where it degraded much more severely. Whereas, the relatively adequate rainfall in the 1990 s maintained the river hydrological health at a good status. The quantitative evaluation showed that human activities were the main driving factors for the hydrological health degradation during the whole human-influenced period, with contributions of 80.8%, 91.9%, and 86.0% for the Taipingzhuang, Chifeng, and Xinglongpo catchments, respectively. Widespread artificial water withdrawal and reservoir operation were the two crucial human activities that caused the degradation of river hydrological health for the studied catchment. The proposed procedure and findings of this study not only help in deeper understanding of the evolutionary characteristics and driving mechanisms of river hydrological health in a changing environment in general, but also provide scientific basis for local water resources management and river ecosystems protection.
Yunan is a crossed lean meat pig breed in China. Backfat thickness is the gold standard for carcass quality grading. However, over 14 years after breed registration, the backfat of Yunan thickened ...and the consistency of backfat thickness decreased. Meanwhile, no genetic study has been ever performed on Yunan population. So, in this study we collected all the 120 nucleus individuals of Yunan and recorded six backfat traits of them, carried out population genetic structure analysis, selection signals analysis and genome-wide association study of Yunan pigs with the help of their founder population Duroc and Chinese native Huainan pigs, to determine the genomic loci on backfat of Yunan. Genetic diversity indexes suggested Yunan pigs had no inbreeding risk while population genetic structure showed they had few molecular pedigrees and were stratified. A total of 71 common selection signals affecting growth and fat deposition were detected by F
ST
and XP-CLR methods. 34 significant loci associated with six backfat traits were detected, among which a 1.40 Mb region on SSC4 (20.03–21.43 Mb) were outstanding as the strong region underlying backfat. This region was common with the results of selection signature analysis, former reported QTLs for backfat and was common for different kinds of backfat traits at different development stage.
ENPP2
,
EXT1
and
SLC30A8
genes around were fat deposition related genes and were of Huainan pig’s origin, among which Type 2 diabetes related gene
SLC30A8
was the most reasonable for being in a 193.21 Kb haplotype block of the 1.40 Mb region. Our results had application value for conservation, mating and breeding improvement of backfat thickness of Yunan pigs and provided evidence for a human function gene might be reproduced in pigs.
The thermal transport properties of an iron-doped molybdenum disulfide system were explored theoretically using the density functional theory calculations combined with the Keldysh non-equilibrium ...Green's function approach. The results indicate that a perfect spin filtering effect and spin Seebeck effect are induced thermally. Excellently, there exists thermal colossal magnetoresistances, which exhibit a transition between positive and negative that can be tuned using temperature. These features were elucidated using the band structures of the electrodes and the transmission function together with current spectra. Our findings may be helpful in the design of highly efficient spin caloritronic devices.
The thermal transport properties of an iron-doped molybdenum disulfide system were explored theoretically using the density functional theory calculations combined with the Keldysh non-equilibrium Green's function approach.
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