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The bHLH transcription factors play pivotal roles in plant growth and development, production of secondary metabolites and responses to various environmental stresses. Although the bHLH genes have been well studied in model plant species, a comprehensive investigation of the bHLH genes is required for tobacco with newly obtained high-quality genome. In the present study, a total of 309 NtbHLH genes were identified and can be divided into 23 subfamilies. The conserved amino acids which are essential for their function were predicted for the NtbHLH proteins. Moreover, the NtbHLH genes were conserved during evolution through analyzing the gene structures and conserved motifs. A total of 265 NtbHLH genes were localized in the 24 tobacco chromosomes while the remained 44 NtbHLH genes were mapped to the scaffolds due to the complexity of tobacco genome. Moreover, transcripts of NtbHLH genes were obviously tissue-specific expressed from the gene-chip data from 23 tobacco tissues, and expressions of 20 random selected NtbHLH genes were further confirmed by quantitative real-time PCR, indicating their potential functions in the plant growth and development. Importantly, overexpressed NtbHLH86 gene confers improve drought tolerance in tobacco indicating that it might be involved in the regulation of drought stress. Therefore, our findings here provide a valuable information on the characterization of NtbHLH genes and further investigation of their functions in tobacco.

This study examines the mechanism of adsorption–dispersion by superplasticisers with varying side chain density in cement paste. Acrylic acid was used to copolymerise with 2-methylprop-2-ene polyethylene glycol, using chain transfer agent to synthesise polycarboxylate ether superplasticisers (PCEs) with comparable main chain lengths and different side chain densities. Gel permeation chromatography, zeta potential, total organic carbon and fluidity tests were used to investigate the adsorption–dispersion of PCE samples in cement pastes with different amounts of tricalcium aluminate (C3A) additive. The results indicate: products with higher side chain densities also have correspondingly shorter main chains, which allows them to form conformations with comparable initial adsorption performance; with C3A added, samples with denser side chains performed better, and their resistance to adsorption became more prominent at higher C3A content.

Background Abscisic acid (ABA) is an important phytohormone for plant growth, development and responding to stresses such as drought, salinity, and pathogen infection. Pyrabactin Resistance 1 (PYR1)/PYR1-Like (PYL)/Regulatory Component of ABA Receptor (RCAR) (hereafter referred to as PYLs) has been identified as the ABA receptors. The PYL family members have been well studied in many plants. However, the members of PYL family have not been systematically identified at genome level in cultivated tobacco (Nicotiana tabacum) and its two ancestors. In this study, the phylogenic relationships, chromosomal distribution, gene structures, conserved motifs/regions, and expression profiles of NtPYLs were analyzed. Results We identified 29, 11, 16 PYLs in the genomes of allotetraploid N. tabacum, and its two diploid ancestors N. tomentosiformis and N. sylvestris, respectively. The phylogenetic analysis revealed that NtPYLs can be divided into three subfamilies, and each NtPYL has one counterpart in N. sylvestris or N. tomentosiformis. Based on microarray analysis of NtPYL transcripts, four NtPYLs (from subfamily II, III), and five NtPYLs (from subfamily I) are highlighted as potential candidates for further functional characterization in N. tabacum seed development, response to ABA, and germination, and resistance to abiotic stresses, respectively. Interestingly, the expression profiles of members in the same NtPYL subfamily showed somehow similar patterns in tissues at different developmental stages and in leaves of seedlings under drought stress, suggesting particular NtPYLs might have multiple functions in both plant development and drought stress response. Conclusions NtPYLs are highlighted for important functions in seed development, germination and response to ABA, and particular in drought tolerance. This work will not only shed light on the PYL family in tobacco, but also provides some valuable information for functional characterization of ABA receptors in N. tabacum. Electronic supplementary material The online version of this article (10.1186/s12864-019-5839-2) contains supplementary material, which is available to authorized users.

The effect of Ti and B microalloying on the hardenability, prior austenite grain size (PAGS), mechanical properties, and sulfide stress cracking (SSC) of C110 grade steel was studied by Jominy testing, static tensile testing, an optical microscope (OM), scanning electron microscopy (SEM) and double cantilever beam (DCB) testing. The results show that the addition of 0.015% Ti and 0.002% B into a medium-carbon Fe-Cr-Mo-Nb-V steel increased the hardenability and refined the PAGS and quenched martensite packets, and the size of carbides was reduced. It is believed that these behaviors are responsible for the improvement in the threshold stress intensity factor KISSC.

With the development of microelectronics and the miniaturization of electronic devices, the use of molecular materials to construct various components in electronic circuits has become a most likely development trend. Compared with silicon-based semiconductor components, molecular electronic device has the advantages of small size, high integration, low energy consumption and fast response. In recent years, more and more molecules have been used to design molecular devices such as molecular diodes, molecular switches, molecular field effect transistors and molecular memories. In this paper, sandwich structure devices based on graphene nanoribbon electrodes are constructed. The first-principles calculation method combining density functional theory and non-equilibrium Green’s function is adopted to design the molecular devices with functional characteristics. The effects of redox reactions on the electrical transport properties of molecular devices are systematically discussed. The main research contents of this paper are as follows. The switching characteristics of an anthraquinone molecular device based on graphene electrode are studied. The zigzag-edge nanoribbons and armchair-edge graphene nanoribbons are selected as electrodes. Considering the two isomers of anthraquinone (HQ) and anthraquinone (AQ) molecules in the redox reaction, the double electrode molecular junction is constructed. The effects of redox reaction and electrode structure on the switching characteristics of anthraquinone molecular devices are discussed. It is found that the current in the HQ configuration is significantly greater than that in the AQ configuration, regardless of the zigzag-edge graphene electrode or the armchair-edge graphene electrode. That is, under the redox reaction, the anthraquinone molecules show significant switching characteristics. The switching ratio of zigzag-edge graphene electrode is selected to reach a maximum of 3125, and that of armchair-edge graphene electrode is selected to maximum of 1538. In addition, when the armchair-edge graphene is used as an electrode in the HQ configuration, the negative differential resistance is obviously between 0.7 and 0.9 V.

There is much fluorescence for impurities on the variation cashmere fiber surface; the characteristic of the Raman spectrum is not obvious. Based on the orthogonal principle, variation cashmere fiber is purified by soaking in different component water/organic solvents, and cleaning with ultrasonic wave. Through measuring and analyzing the Raman spectrum, we confirm the optimal organic solvent system, soaking time and temperature for the cleanse technology of variation cashmere. The result shows that, the variation cashmere fiber is soaked in diethyl ether/aqueous organic solvent in the optimal condition, the Raman spectrum appears good peak-area ratio, and we get cleanest variation cashmere fiber.

A novel solid catalyst for coupling reaction has been successfully prepared by immobilizing palladium in the nanocages of the ethylenediamine-functionalized mesoporous material SBA-16. The structure and composition of the solid catalyst were characterized by N2 adsorption–desorption, XRD, TEM, FT-IR and TGA. These results revealed that Pd(II) was successfully embedded inside the nanocages of SBA-16. This catalyst afforded high activity (over 91% conversion) for the Suzuki coupling of various aryl bromides and phenyiboronic acids in ethanol solvent at 60 °C even at the loading of 0.5 mol% Pd. Moreover, the SBA-16-2 N-Pd(II) catalyst could be separated easily from reaction mixture and reused for ten times without obvious loss of catalytic activity, showing the superiority over the homogeneous catalysts in industrial applications.

A palladium-based catalyst supported on thiol-modified superparamagnetic nanoparticles was successfully prepared by co-precipitation method. These magnetic nanomaterials were characterized by elemental analysis (EA), inductively coupled plasma (ICP), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), fourier transform-infrared (FT-IR), thermogravimetric analysis (TGA) and vibrating sample magnetometry (VSM). The conversions of various aromatic nitro and unsaturated compounds can receive a really high yield with the existence of magnetic nanomaterials. The turn-over frequency (TOF) can be 66.46 h−1 in ethanol under a H2 atmosphere at room temperature. In this paper, the conversions of aromatic nitro bearing a variety of substituents were 93.56–100%, moreover, the catalyst afforded over 90% yield in the reducing unsaturated compounds. Another advantage is that the magnetite nanoparticles modified by thiol group can be separated just through the external magnetic force and can be reused atleast ten times without any significant loss in activity.

Drought is one of the most severe forms of abiotic stresses that threaten the survival of plants, including crops. In turn, plants dramatically change their physiology to increase drought tolerance, including reconfiguration of proteomes. Here, we studied drought-induced proteomic changes in leaves of cultivated tobacco (Nicotiana tabacum), a solanaceous plant, using the isobaric tags for relative and absolute quantitation (iTRAQ)-based protein labeling technology. Of identified 5570 proteins totally, drought treatment increased and decreased abundance of 260 and 206 proteins, respectively, compared with control condition. Most of these differentially regulated proteins are involved in photosynthesis, metabolism, and stress and defense. Although abscisic acid (ABA) levels greatly increased in drought-treated tobacco leaves, abundance of detected ABA biosynthetic enzymes showed no obvious changes. In contrast, heat shock proteins (HSPs), thioredoxins, ascorbate-, glutathione-, and hydrogen peroxide (H2O2)-related proteins were up- or down-regulated in drought-treated tobacco leaves, suggesting that chaperones and redox signaling are important for tobacco tolerance to drought, and it is likely that redox-induced posttranslational modifications play an important role in modulating protein activity. This study not only provides a comprehensive dataset on overall protein changes in drought-treated tobacco leaves, but also shed light on the mechanism by which solanaceous plants adapt to drought stress.

By applying first-principles method based on density functional theory combined with nonequilibrium Green’s function, we investigate the effect of torsion angle on the electronic transport properties in dipyrimidinyl–diphenyl co-oligomer molecular device with tailoring graphene nanoribbon electrodes. The results show that the torsion angle plays an important role on the electronic transport properties of the molecular device. When the torsion angle rotates from 0[Formula: see text] to 90[Formula: see text], the molecular devices exhibit very different current–voltage characteristics which can realize the on and off states of the molecular switch.

The conformation statistics of single chain of polymer is a most basic and important problem in polymer science. Common polymer chain could do internal rotation around its chemical bond because thermal motion, this makes polymer chain’s form change ceaselessly. Because the molecular weight of macromolecule is very large, the number of polymer conformation is too large to be resolved using the common mathematical methods. This paper researches the free rotation chain conformation in non-lattice chain of high molecule. Through setting-up mathematical model, a new method is proposed to simulate the polymer chain. Simulation result shows the polymer conformation in microcosmic and reflects the characteristic “random coil” of polymer chain actually. These results provide an important basis for further quantitative analysis and optimal design.

An investigation of the microstructure and the microprocess of fracture of an eutectoid pearlitic steel has been carried out by means of electron-diffraction-contrast (EDC) and other analytical techniques. The nature of the dislocations in pro-eutectoid ferrite and ferrite in pearlite was determined. The character of interface conjunction between ferrite and cementite was discussed. The fracture process of pearlitic steel has been analysed crystallographically.