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Text has become one of the most extensively used digital media in Internet, which provides steganography an effective carrier to realize confidential message hiding. Nowadays, generation-based linguistic steganography has made a significant breakthrough due to the progress of deep learning. However, previous methods based on recurrent neural network have two deviations including exposure bias and embedding deviation, which seriously destroys the security of steganography. In this paper, we propose a novel linguistic steganographic model based on adaptive probability distribution and generative adversarial network, which achieves the goal of hiding secret messages in the generated text while guaranteeing high security performance. First, the steganographic generator is trained by using generative adversarial network to effectively tackle the exposure bias, and then the candidate pool is obtained by a probability similarity function at each time step, which alleviates the embedding deviation through dynamically maintaining the diversity of probability distribution. Third, to further improve the security, a novel strategy that conducts information embedding during model training is put forward. We design various experiments from different aspects to verify the performance of the proposed model, including imperceptibility, statistical distribution, anti-steganalysis ability. The experimental results demonstrate that our proposed model outperforms the current state-of-the-art steganographic schemes.

With the extensive use of texts on social network, text steganography, which protects several sensitive messages by embedding secret data into normal texts, has attracted widespread attention. As an adversary, text steganalysis which reveals the existence of hidden messages is also important. Recently, Deep Neural Networks (DNNs) have led to significant improvements in text steganalysis. However, the deeper and wider DNNs cause the increase of inference time, which restricts the practicality of text steganalysis. In this paper, we propose an effective and real-time text steganalysis method based on multi-stage transfer learning to enhance inference efficiency and detection performance simultaneously. The experimental results show that the proposed text steganalysis method can outperform previously reported methods in terms of detection accuracy and inference efficiency.

Environmental estrogen contamination poses severe threat to wildlife and human. Biodegradation is an efficient strategy to remove the wide-spread natural estrogen, while strains suitable for hostile environments and fit for practical application are rare. In this work, Microbacterium hominis SJTG1 was isolated and identified with high degrading efficiency for 17β-estradiol (E2) and great environment fitness. It could degrade nearly 100% of 10 mg/L E2 in minimal medium in 6 days, and remove 93% of 1 mg/L E2 and 74% of 10 mg/L E2 in the simulated E2-polluted solid soil in 10 days. It maintained stable E2-degrading efficiency in various harsh conditions like non-neutral pH, high salinity, stress of heavy metals and surfactants. Genome mining and comparative genome analysis revealed that there are multiple genes potentially associated with steroid degradation in strain SJTG1. One 3β/17β-hydroxysteroid dehydrogenase HSD-G129 induced by E2 catalyzed the 3β/17β-dehydrogenation of E2 and other steroids efficiently. The transcription of hsd-G129 gene was negatively regulated by the adjacent LysR-type transcriptional regulator LysR-G128, through specific binding to the conserved site. E2 can release this binding and initiate the degradation process. This work provides an efficient and adaptive E2-degrading strain and promotes the biodegrading mechanism study and actual remediation application.

Tellurite is a strong antimicrobial agent highly toxic to many microorganisms, while its toxicity mechanism is still unclear. In this study, the comparative transcriptome analysis of E. coli MG1655 responding to the stress of tellurite was performed and the differentially transcribed genes were analyzed, to understand toxicity mechanisms of tellurite preliminaryly and uncover metabolism processes changes resulted from tellurite globally. After treated with 10 µg/mL tellurite for 1 h, high concentration and long time, the cells exhibited an obvious adaptive reaction and many metabolic processes were influenced. The transcription of the genes involved in the ribosome metabolism and the flagella assembly were changed significantly, implying they might be the major pathway affected by tellurite. The transcription of the genes encoding the transcriptional factors and small RNAs, and the genes functioned in the cell motility, metal ion metabolism and membrane function were also varied, which may participate in the metabolism adjustment and damage repair to resist the toxicity of tellurite. This work can facilitate the study of the toxicity mechanism of tellurite and promote the clinical application of this chemical.

Background: Pseudomonas citronellolis SJTE-3 can efficiently degrade 17β-estradiol (E2) and other estrogenic chemicals. However, the enzyme responsible for E2 metabolism within strain SJTE-3 has remained unidentified. Objective: Here, a novel 3-oxoacyl-(acyl-carrier protein) (ACP) reductase, HSD-X1 (WP_ 009617962.1), was identified in SJTE-3 and its enzymatic characteristics for the transformation of E2 were investigated. Methods: Multiple sequence alignment and homology modelling were used to predict the protein structure of HSD-X1. The concentrations of different steroids in the culture of recombinant strains expressing HSD-X1 were determined by high performance liquid chromatography. Additionally, the transcription of hsd-x1 gene was investigated using reverse transcription and quantitative PCR analysis. Heterologous expression and affinity purification were used to obtain recombinant HSD- X1. Results: The transcription of hsd-x1 gene in P. citronellolis SJTE-3 was induced by E2. Multiple sequence alignment (MSA) indicated that HSD-X1 contained the two consensus regions and conserved residues of short-chain dehydrogenase/reductases (SDRs) and 17β-hydroxysteroid dehydrogenases (17β-HSDs). Over-expression of hsd-x1 gene allowed the recombinant strain to degrade E2. Recombinant HSD-X1 was purified with a yield of 22.15 mg/L and used NAD+ as its cofactor to catalyze the oxidization of E2 into estrone (E1) while exhibiting a Km value of 0.025 ± 0.044 mM and a Vmax value of 4.92 ± 0.31 mM/min/mg. HSD-X1 could tolerate a wide range of temperature and pH, while the presence of divalent ions exerted little influence on its activity. Further, the transformation efficiency of E2 into E1 was over 98.03% across 15 min. Conclusion: Protein HSD-X1 efficiently catalyzed the oxidization of E2 and participated in estrogen degradation by P. citronellolis SJTE-3.

A novel model of the coupling system consisting of a solar collector and an alkali metal thermal electric converter (AMTEC) is proposed, in which various irreversible losses are considered. Analytical expressions for the efficiencies of the solar collector, AMTEC, and coupling system are derived. The operative temperatures of the solar collector and AMETC are determined by energy balance equations rather than some specified parameters. The influences of the thickness of the electrolyte membrane, current density, and area ratio of the absorber to the AMTEC on the performance of the system are discussed. The maximum efficiency and power output density for a given value of the solar concentration ratio are calculated and revealed to be two different operation states of the coupling system. The effects of the solar concentration ratio on the optimal regions of some key parameters are discussed in detail. The optimum selection criteria of these parameters are provided.

The aim of this study is to deeply search the performance of the coupling system comprised of a direct carbon fuel cell and an alkali metal thermal electric converter. The main contents of this study are to propose the model of the novel coupling system by considering the main irreversible losses, derive the efficiency and power output of the whole system, discuss the influences of the electric current of the fuel cell, the electrolyte thickness, and the ratio of the electrode areas of two subsystems on the systemic performances, and, evaluate and compare the performances of the whole system and the fuel cell. The main novelties are to provide parametric optimum choice criteria and give the reasonably matching schemes of two subsystems. The results obtained reveal the advantages of the present coupling system.

Spin-momentum locking arising from strong spin-orbit coupling is one of the key natures of topological materials. Since charge can induce a spin polarization due to spin-momentum locking, the search for materials that exhibit this feature has become one of the top priorities in the field of spintronics. In this paper, we report the electrical detection of the spin-transport properties of ${\mathrm{ZrTe}}_{5}$ nanowires, using a nonlocal geometry measurement. A clear hysteresis voltage signal, which depends on the relative orientations between the magnetization of the ferromagnetic electrodes and the carrier spin polarization, has been observed. The hysteresis voltage states can be reversed by altering the electron movement direction, providing direct evidence of the spin-momentum locking feature of ${\mathrm{ZrTe}}_{5}$ nanowires and revealing its topological nature. Furthermore, the current-dependent measurement suggests that the charge (spin) current is induced by thermal effect, which utilizes the thermoelectric properties of ${\mathrm{ZrTe}}_{5}$. Using the thermal effect to control the spin-polarized current protected by spin-momentum locking offers possibilities for small-sized devices based on the topological materials.

Putrescine, a typical polyamine compound important for cell growth and stress resistance, can be utilized as an energy source. However, the regulation of its catabolism is unclear. Here the small RNA (sRNA) Spot 42, an essential regulator of carbon catabolite repression (CCR), was confirmed to participate in the post-transcriptional regulation of putrescine catabolism in Escherichia coli. Its encoding gene spf exclusively exists in the γ-proteobacteria and contains specific binding sites to the 5'-untranslated regions of the puuE gene, which encodes transaminase in the glutamylated putrescine pathway of putrescine catabolism converting γ-aminobutyrate (GABA) into succinate semialdehyde (SSA). The transcription of the spf gene was induced by glucose, inhibited by putrescine, and unaffected by PuuR, the repressor of puu genes. Excess Spot 42 repressed the expression of PuuE significantly in an antisense mechanism through the direct and specific base-pairing between the 51`-57 nt of Spot 42 and the 5'-UTR of puuE. Interestingly, Spot 42 mainly influenced the stability of the puuCBE transcript. This work revealed the regulatory role of Spot 42 in putrescine catabolism, in the switch between favorable and non-favorable carbon source utilization, and in the balance of metabolism of carbon and nitrogen sources.

The aim of this study is to deeply search and understand the performance of the coupling system composed of an alkali metal thermoelectric converter and a thermoelectric generator. The main methods are to update the model of the coupling system, which includes the main irreversible losses existing in subsystems and coupling system, and obtain the analytical expressions of the power outputs and efficiencies of two subsystems and coupling system. The main novelties are to discuss the influences of the thickness of the β ″ -alumina solid electrolyte on the whole performance of the system and solve the matching problem between two subsystems. The main contents of this study include that the influences of the thickness of the electrolyte membrane, current density of the alkali metal thermoelectric converter, and electric current of the thermoelectric generator on the power output density and efficiency are discussed and the maximum power output density and efficiency of the system are calculated and compared with those of the single alkali metal thermoelectric converter and the existing coupling models. The results obtained reveal the advantages of the present model. The whole performance of the coupling system can be optimized and the parametric selection criteria of several key parameters of the coupling system operating at optimum states can be provided, When the thickness of the electrolyte membrane is optimally selected, the maximum efficiency of the present model attain 34.6% and increase about 10.4%, compared with those of the existing best coupling system. The waste heat released by the alkali metal thermoelectric converter can be efficiently utilized by the thermoelectric generator.

[EN]A model for a novel integrating system consisting of an alkali metal thermoelectric converter and a non-recuperative irreversible Brayton heat engine is presented. The efficiency and power output density of the overall system is analyzed at light of the main characteristic losses in each subsystem: the thickness of the electrolyte, the current density of the converter, and the internal losses of the Brayton cycle coming from the compressor and turbine. A detailed study on the behavior of the overall maximum power and maximum efficiency regimes is also presented. An analysis on compromise performance regimes from multi-objective and multi-parametric optimization techniques based on the Pareto front, for both the subsystems and the overall system, enhance the obtained results. The numerical results of the present model are compared with those of alkali metal thermoelectric converter working alone and with other different existing hybrid models. It is found that the exhaust heat discharged by the converter can be efficiently utilized by an irreversible Brayton heat engine. So, the maximum efficiency and maximum power output density of the present model attain 41.7% and W/m2 which increase about 44.8% and 158% compared to the values of the alkali metal thermoelectric converter working alone and 20.5% and 80.4% when compared with a hybridized configuration including a thermoelectric energy converter., National Natural Science Foundation of China (No. 11675132) People’s Republic of China and China Scholarship Council (CSC) under the State Scholarship Fund (No. 201806310020) Junta de Castilla y Leon under project SA017P17. J.G.A. acknowledges Universidad de Salamanca contract 2017/X005/1

A new model of the intermediate band thermoradiative cell (IBTRC) is put forward. Expressions for the power output density (POD) and efficiency of the IBTRC are derived. The current densities and PODs arising from the normal transitions and interband transitions of electrons are compared. It is found that when the IBTRC with a bandgap of 0.2 eV is operated between the heat source at 1000 K and the surroundings at 300 K, the maximum POD and efficiency of the cell are approximately $1.583\times $ and $1.096\times $ of those of the thermoradiative cell without intermediate bands (IBs) under the same operating temperature and bandgap, respectively. This shows that the performance of the IBTRC can be largely improved by the insert of the IB. Moreover, the optimal selection criteria of some key parameters are provided, and then the optimum operating conditions of the IBTRC are determined. Finally, several issues that will influence the performances of the IBTRC are pointed out. These results may help engineers to fabricate high-performance IBTRCs.

The cycle model of an alkali metal thermal electric converter (AMTEC) is updated, where the relation between the thickness of the electrolyte and the other parameters of the AMTEC is established. The effects of thickness of the electrolyte on the performance of the AMTEC are discussed. The operation states of the AMTEC are optimized. The maximum efficiency and power output density of the AMTEC are calculated. The selective criteria of the thickness of the electrolyte and other parameters are optimally provided. Moreover, it is expounded that the proportional coefficient related to the thickness of the electrolyte is closely dependent on electrolyte materials. The effects of this coefficient on the efficiency and power output density of the AMTEC are further discussed, and consequently, the rational range of the coefficient is determined.

A new model of the energy selective electron (ESE) device composed of four electron reservoirs and four energy filters is proposed. The device can work as a thermal amplifier, which may be equivalent to a coupling system consisting of two three-electron-reservoir heat pumps. Expressions for the heat-pumping rate (HPR) and coefficient of performance (COP) of the device are analytically derived through the heat flows of two-terminal ESE devices. The maximum HPR and COP are calculated. It is found that the maximum HPR of the coupling system can attain 2 times of that of a three-electron-reservoir heat pump while its COP is still equal to that of a three-electron-reservoir heat pump. Moreover, the effects of the chemical potentials of electron reservoirs, central levels of energy filters, half width at half maximum of energy filters on the HPR and COP of the device are discussed in detail. The optimal configuration of the device is determined. The cut-off value of the half width at half maximum of energy filters is calculated. The optimum selection criteria of main parameters are provided.