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Defective structures, such as DNA mismatches, occur in DNA with a high frequency in some biological processes. They are difficult to identify and have recently become the focus of single-molecule investigations. Three single-molecule experiments were successively conducted to detect the effects of DNA mismatch on the stability of DNA hairpins. However, there was no consensus regarding the results of the intermediate state caused by DNA mismatch. Based on the extended ox-DNA model, DNA mismatch was introduced to the stem of DNA hairpins with different stem lengths (12–20 bps) and 4T in hairpin loops. The intermediate state and its dependence on the position of the DNA mismatch in the stem from the hairpin loop were systematically studied. The results indicated that DNA mismatch definitely reduced the critical forces of DNA hairpins. At the same time, a common rule about the dependence of the intermediate state on the position of DNA mismatch was generalized in a phase diagram constructed in a phase space of a scaled position of DNA mismatch. Three segments on its diagonal line corresponded to the ranges of the scaled position of DNA mismatch [0, 0.55), [0.55, 0.85), and [0.85, 1], respectively. In the [0.55, 0.85) range, the extension probability distribution of DNA hairpins had unfolded, intermediate, and folded states. In contrast, in the other ranges [0, 0.55) and [0.85, 1], the extension probability distributions had unfolded and folded states. The scaled positions of DNA mismatch for the DNA hairpins used in the three single-molecule experiments (0.65, 0.4736, and 0.5) fell in the ranges [0.55, 0.85) and [0, 0.55). Obviously, the common rule generalized in the phase diagram not only clarifies the non-consensus between the three single-molecule experiments but also highlights the design of single-molecule experiments in the future.

Surface roughness was regarded as an essential indicator of the quality of machining. In machining demands, it was often necessary that the surface roughness of the workpiece lies in a specific range.For this reason , it was significant to detect the surface roughness level of the workpiece. For the traditional roughness detection methods with high manual involvement and unable to achieve automation, this paper proposed a new artificial intelligence detection approach. The approach consisted of a 1-Dimensional Convolutional Neural Network (1DCNN) and a Bi-directional Gated Recurrent Unit Network(BiGRU), called the 1DCNN-BiGRU model. 1DCNN-BiGRU accomplished the detection of roughness levels by classifying surface images directly, without extracting specific roughness features. First, 1DCNN was applied to automate the extraction of roughness-related features along the texture direction of the product surface image. Subsequently, the feature sequences extracted by 1DCNN were fed into BiGRU to learn the overall dependence of the roughness on the sequences. Experiments were performed on a 45steel workpiece roughness image dataset. The 1DCNN-BiGRU model gave 90.60% and 88.06% detection performance on the training and test sets, respectively.

Graphdiyne (GDY) is a new 2D carbon material different from graphene, and its ideal drug carrying and photothermal therapy efficacy had been noticed recently. Graphdiyne-oxide (GDYO), which few phototherapy researches had been reported, has more oxygen functional groups than GDY. Metal-organic framework materials Fe3O4@UiO-66-NH2 (FU) can covalently connect to GDYO layers and obtain covalent-organic framework-like structures FUGYO. FU enlarged interlamellar space of GDYO, which avoided the aggregation of FUGYO multiple layers. At the same time, more acetylenic bonds and hydrophilic group were exposed, which brings out advantages like stability, hydrophily, high drug-loading, as well as magnetic targeting and better magnetic resonance imaging efficacy. To promote cancer treatment effect and water solubility, we loaded chemotherapy drug doxorubicin (DOX) in FUGYO, then encapsulated FUGYO/DOX in phosphatidylcholine and fluorescent organic polymer BODIPY-PEG (BP) to integrate image-guided and synergistic therapy in one nanoparticle (BPFG/DOX). Due to the unique structure of BPFG/DOX, the π–π interaction between GDYO and BP improved photodynamic therapy efficiency. About 10 μg ml−1 BPFG/DOX have nearly 90% cell lethality to MCF-7 (human breast cancer cell line) cells with laser irradiation. In vivo, BPFG/DOX possessed ideal magnetic targeting and effectively inhibited tumor growth in 6 d. In conclusion, BPFG/DOX not only acts as an excellent tumor theranostic agent but also provides a scheme for applying GDYO in the biomedical region.

Helium-3 (3He) is a noble gas that has critical applications in scientific research and promising application potential as clean fusion energy. It is thought that the lunar regolith contains large amounts of helium, but it is challenging to extract because most helium atoms are reserved in defects of crystals or as solid solutions. Here, we find large amounts of helium bubbles in the glassy surface layer of ilmenite particles that were brought back by the Chang’E-5 mission. The special disordered atomic packing structure of glasses should be the critical factor for capturing the noble helium gas. The reserves in bubbles do not require heating to high temperatures to be extracted. Mechanical methods at ambient temperatures can easily break the bubbles. Our results provide insights into the mechanism of helium gathering on the moon and offer guidance on future in situ extraction.

OxDNA, as a successful coarse-grain model, has been applied to reproduce the thermodynamic and mechanical properties of both single- and double-stranded DNA. In current simulation, oxDNA is extended to explore the combined effects of temperature and force on the stability of DNA hairpin and its free energy landscape. Simulations were carried out at different forces and temperatures, at each temperature, a 18-base-pair DNA hairpin dynamically transited between folded state and unfolded state, and the separation between two states is consistent with the full contour length of single-stranded DNA in the unfolded state. Two methods were used to identify the critical force of DNA hairpin at each temperature and the critical forces obtained from two methods were consistent with each other and gradually decreased with the increasing temperature from 300 K to 326 K. The critical force at 300 K is reasonably consistent with the single molecule result of DNA hairpin with the same stem length. The two-state free energy landscape can be elucidated from the probability distribution of DNA hairpin extension and its dependence on the force and temperature is totally different. The increasing temperature not only reduces the free energy barrier, but also alters the position of transition point along the extension coordinate, resulting in the reduction of folding distance and the extension of unfolding distance, but their sum is not obviously dependent on the temperature. Generally, an assumption that the location of transition state in two-state energy landscape is independent of the stretching force is used to analyze the data of the single molecule experiment, but current simulation results indicate that effects of stretching forces on the location of transition state in two-state energy landscape are dependent on temperature. At relatively high temperature, stretching force can also change the location of transition state in the free energy landscape.

High dose intake of fluoride results in fluorosis and our previous experiments at single-molecule level using magnetic tweezers have proved that fluoride anions destabilize DNA hairpin and its equilibrium critical force decreases with increasing concentration of fluoride anions. One possible mechanism is that a fluoride anion competes with a DNA base and forms a hydrogen bond with its complementary base. The Isothermal Titration Calorimetry experiments suggest that the fluoride anion does not form a hydrogen bond with a DNA base. With increasing concentration of fluoride anions, decreasing Zeta potentials for different oligonucleotides enhance the electrostatic repulsion between complementary oligonucleotides, which accounts for the decreasing association constant and destabilization of DNA hairpin. Molecule dynamics simulation was further performed to determine the ion distribution around the oligonucleotide, radial distribution functions (RDFs) indicate that the fluoride anion distributes far from the oligonucleotide in comparison with the chloride anion, which is the possible mechanism that decreases Zeta potentials with the increasing concentration of fluoride anions.

The deformation behavior of the 1.15C-4.00Cr-3.00V-6.00W-5.00Mo powder metallurgy high speed steel in hot working processes was investigated by the isothermal compression tests carried out at the temperature of 1000-1150°C and the strain rate of 0.001-1.0s−1 with the height reduction of 60%. The processing maps were constructed, identification of the instability regions and optimization of hot deformation parameters. Different types of instability criteria of PRASAD, MALAS, GEGEL, MURTY and SEMIATIN were compared. It was found that the hot working process of the steel can be carried out safely in the domain of 1040-1130 °C/0.01-1.0 s−1. Furthermore, the temperature and the strain rate had a great effect on microstructures. To obtain a homogeneous microstructure with fine grain, the hot working process should be carried out under the condition of 1050-1100 °C/0.01-0.06 s−1.

DNA persistence length is a key parameter for quantitative interpretation of the conformational properties of DNA and related to the bending rigidity of DNA. A series of experiments pointed out that, in the DNA condensation process by multivalent cations, the condensed DNA takes elongated coil or compact globule states and the population of the compact globule states increases with an increase in ionic concentration. At the same time, single molecule experiments carried out in solution with multivalent cations (such as spermidine, spermine) indicated that DNA persistence length strongly depends on the ionic concentration. In order to revolve the effects of ionic concentration dependence of persistence length on DNA condensation, a model including the ionic concentration dependence of persistence length and strong correlation of multivalent cation on DNA is provided. The autocorrelation function of the tangent vectors is found as an effective way to detect the ionic concentration dependence of toroidal conformations. With an increase in ion concentration, the first periodic oscillation contained in the autocorrelation function shifts, the number of segment contained in the first periodic oscillation decreases gradually. According to the experiments, the average long-axis length is defined to estimate the ionic concentration dependence of condensation process further. The relation between long-axis length and ionic concentration matches the experimental results qualitatively.

With a view of detecting the effects of macromolecular crowding on the phase transition of DNA compaction confined in spherical space, Monte Carlo simulations of DNA compaction in free space, in confined spherical space without crowders and in confined spherical space with crowders were performed separately. The simulation results indicate that macromolecular crowding effects on DNA compaction are dominant over the roles of multivalent counterions. In addition, effects of temperature on the phase transition of DNA compaction have been identified in confined spherical space with different radii. In confined spherical space without crowders, the temperature corresponding to phase transition depends on the radius of the confined spherical space linearly. In contrast, with the addition of crowders to the confined spherical space, effects of temperature on the phase transition of DNA compaction become insignificant, whereas the phase transition at different temperatures strongly depends on the size of crowder, and the critical volume fraction of crowders pertains to the diameter of crowder linearly.

In the present study, Fe–Cr–Ni alloy coatings were produced by laser cladding using the blending powder of Cr and Ni on the surface of T10 steel. The composition of phase and microstructure were analyzed by scanning electron microscope (SEM) and x-ray diffraction (XRD). The microhardness and corrosion resistance were investigated. The Fe–Cr–Ni cladding coatings composed of austenites and a few eutectic ferrites. And the content of eutectic ferrite in the grain boundary decreased with the decreasing Cr/Ni ratio of the blending powder. The Creq/Nieq ratio and the ferrite number (FN) of the coatings confirm that the solidification process was the AF mode for the Fe–Cr–Ni cladding coatings. The average microhardness value of Fe–Cr–Ni coatings was about 380HV0.2 and the Cr/Ni ratio of the blending powder was not an obvious effect. The corrosion resistance of Fe–Cr–Ni alloy coatings which was significantly superior to T10 steel decreased with the decreasing Cr/Ni ratio of the blending powder. This research exhibits that the Fe–Cr–Ni coatings and laser cladding processing have a potential engineering application value on hypereutectoid carbon steel.

The PLA/PHBV/PBAT blends with varied ratio were extruded into filaments by a 3D consumables extruder and the dumbbell-shaped specimens were prepared by a desktop 3D printer. The properties of composites and printed samples were characterized by x-ray diffraction (XRD), differential scanning calorimetry (DSC), melt flow index (MFI), scanning electron microscope (SEM) and tensile strength test. The process parameters of 3D printing were also surveyed. Compared with injection molded specimens with identical composition, the PLA crystallinity of printed specimens was greatly improved; SEM micrographs of the 3D printed specimens fracture surface showed a more uniform microstructure distribution with smaller oval cavities structure; and the 3D printed specimens exhibited superior tensile strength and elongation at break. This study may expand the application fields of PLA based 3D printing filaments.

Using density-functional-theory calculations, a monoclinic metallic post-ζ phase (space group C2/c) is predicted at 215 GPa. The calculated phonon dispersion curves suggest that this structure is stable at least up to 310 GPa. Oxygen remains a molecular crystal and there is no dissociation in the related pressure range. Moreover, it is found that the phase transition from ζ to post-ζ phase is attributed to phonon softening. The significant change in the optical properties can be used to identify the phase transition.