Search

In order to develop a portable flash x-ray source, a compact explosive pulsed power source based on an explosive-driven ferroelectric generator (EDFEG) is investigated numerically and experimentally in this paper. The EDFEG is used as a primary power supply to charge a pulse capacitor, and then the capacitor outputs high current through an inductor and an electrical exploding opening switch (EEOS). Finally, a high voltage fast pulse is generated on a diode, which generates x rays. A circuit model was built to analyze the performance of this compact pulsed power source. A portable flash x-ray generator prototype was constructed in our laboratory. The typical experimental results illustrated that after metal wires of the EEOS exploded, a high-voltage fast pulse with a peak value of 180 kV, a rise time of 2.8 ns, and a pulse width of 30 ns was generated on the x-ray diode. Meanwhile, an x-ray pulse with a pulse width of 19 ns, a focus of about 1 mm, and a dose of 100 mR at 15 cm was obtained.

Double common bile duct is a rare congenital anomaly among biliary anomalies. The anomaly has an important clinical implication because of its association with biliary tract obstruction. In addition, if one of the two common bile ducts is mistaken for the cystic duct during surgery, residual stones and bile duct injury are likely to occur. Here, we report a case of double choledochal variation (Type Vb) with choledochal calculi. An 82-year-old woman was admitted to the hospital due to mild pain in the upper abdomen accompanied by vomiting for 3 days. Magnetic resonance imaging suggested common bile duct lithiasis, variation of the common bile duct and moderate biliary tract dilation. Laparoscopy combined with choledochoscopic lithotomy was performed for choledocholithotomy. During the operation, left and right choledocholithotomy was performed, and all the gallstones were removed via choledochoscope. The patient's post-operative recovery was good, and no recurrence of cholelith had been observed at the time of writing.

Learning based depth estimation from light field has made significant progresses in recent years. However, most existing approaches are under the supervised framework, which requires vast quantities of ground-truth depth data for training. Furthermore, accurate depth maps of light field are hardly available except for a few synthetic datasets. In this paper, we exploit the multi-orientation epipolar geometry of light field and propose an unsupervised monocular depth estimation network. It predicts depth from the central view of light field without any ground-truth information. Inspired by the inherent depth cues and geometry constraints of light field, we then introduce three novel unsupervised loss functions: photometric loss, defocus loss and symmetry loss. We have evaluated our method on a public 4D light field synthetic dataset. As the first unsupervised method published in the 4D Light Field Benchmark website, our method can achieve satisfactory performance in most error metrics. Comparison experiments with two state-of-the-art unsupervised methods demonstrate the superiority of our method. We also prove the effectiveness and generality of our method on real-world light-field images.

Ferroelectric pulsed-power sources with rapid response time and high output energy are widely applied in the defense industry and mining areas. As the core materials, ferroelectric materials with large remnant polarization and high electrical breakdown field should generate high power under compression. Currently, lead zirconate titanate 95/5 ferroelectric ceramics dominated in this area. Due to environmental damage and limited output power of lead-based materials, lead-free ferroelectrics are highly desirable. Here, the electrical response of 0.9BiFeO3-0.1BaTiO3 (BFO-BT) ferroelectric ceramics under shock-wave compression was reported, and a record-high power density of 4.21 × 108 W/kg was obtained, which was much higher than any existing lead-based ceramics and other available energy storage materials. By in situ high-pressure neutron diffraction, the mechanism of shock-induced depolarization of the BFO-BT ceramics was attributed to pressure-induced structural transformation, and the excellent performance was further elaborated by analyzing magnetic structure parameters under high pressures. This work provides a high-performance alternative to lead-based ferroelectrics and guidance for the further development of new materials.

As an alternative class of antimicrobial agents used to overcome drug-resistant infections, antimicrobial peptides (AMPs) have recently gained significant attention. In this study, we designed an improved antimicrobial peptide, K1K8, based on the molecular template of Hp1404. Compared to the wild-type Hp1404, K1K8 showed an improved antibacterial spectrum in vitro, a lower hemolytic activity, and an enhanced serum stability. Importantly, K1K8 also decreased methicillin-resistant Staphylococcus aureus (MRSA) bacterial counts in the wounded region in a mouse skin infection model. Interestingly, K1K8 did not induce bacterial resistance or non-specific immune response reactions. Moreover, the peptide killed bacterial cells mainly by disrupting the bacterial membrane. In summary, K1K8 has the potential to be used as an improved anti-infection agent for topical use, which opens an avenue that potential anti-infection drugs may be designed and developed from the molecular templates of AMPs.

The effect of uniaxial compression stress on the phase/domain pattern and the electromechanical performances were investigated for Pb(In1/2Nb1/2)–Pb(Mg1/3Nb2/3)–PbTiO3 (PIN–PMN–PT) ferroelectric crystals by the polarization/strain vs. electric field and strain vs. uniaxial stress curves measurement. The results showed that (1) uniaxial stress could induce the rotation of polarization from [101]c, [011]c, [−101]c and [0–11]c directions to [110]c, [−110]c, [−1–10]c and [1–10]c directions but no phase transition in orthorhombic (O) phase PIN–PMN–PT crystal; (2) the dielectric and piezoelectric responses of O phase crystal were found to be enhanced by 6.5% and 15% respectively in the region of domain switching due to the increase of free energy instability and polarization mobility induced by uniaxial stress.

Viral infections still threaten human health all over the world, and many people die from viral diseases every year. However, there are no effective vaccines or drugs for preventing or managing most viral diseases. Thus, the discovery and development of broad-spectrum antiviral agents remain urgent. Here, we expressed and purified a venom peptide, Ev37, from the scorpion Euscorpiops validus in a prokaryotic system. We found that rEv37 can inhibit dengue virus type 2 (DENV-2), hepatitis C virus (HCV), Zika virus (ZIKV), and herpes simplex virus type 1 (HSV-1) infections in a dose-dependent manner at noncytotoxic concentrations, but that it has no effect on Sendai virus (SeV) and adenovirus (AdV) infections in vitro. Furthermore, rEv37 alkalized acidic organelles to prevent low pH–dependent fusion of the viral membrane–endosomal membrane, which mainly blocks the release of the viral genome from the endosome to the cytoplasm and then restricts viral late entry. Taken together, our results indicate that the scorpion venom peptide Ev37 is a broad-spectrum antiviral agent with a specific molecular mechanism against viruses undergoing low pH–dependent fusion activation during entry into host cells. We conclude that Ev37 is a potential candidate for development as an antiviral drug.

Since there is a symbiotic and competitive relationship between microorganisms in the same ecological niche, fungal defensins have been found to be important resources for antimicrobial peptides. Here, a fungal defensin, triintsin, was characterized in a clinical isolate of Trichophyton interdigitale from a patient with onychomycosis. The comparison of its genomic and mRNA sequences showed the gene organization and structure of three coding exons separated by two introns. The precursor peptide of triintsin contained 85 amino acid residues, which were composed of three parts including an N-terminal signal domain of 21 residues, a pro-peptide of 47 residues that ended at lysine-arginine and a mature peptide of 38 residues at the C-terminus. The 3D-structure established by homology modeling revealed that triintsin presented a representative typical cysteine-stabilized α-helical and β-sheet fold. The reductive linear peptide of triintsin was obtained by chemical synthesis. After cyclization to form three pairs of disulfide bonds, the oxidative-type peptide displayed broad-spectrum antimicrobial activity against both gram-positive and gram-negative bacteria but also showed anti-fungal activity. Moreover, triintsin can effectively inhibit the growth of clinical strains. Altogether, the peptide is a human pathogenic fungus-derived defensin with broad-spectrum antimicrobial activity.

Level of concentration is a research hotspot for human being at all aspect of human society and all ages. This paper makes use of the TGAM chip that developed a concentration value collector. Our experiment proves the validity and correctness of this equipment and can extract the attention feature in real time. Compared with the traditional attention evaluation which was also known as a questionnaire, our method had stronger real-time ability and high reliability and was more intuitive and more convenient. In addition, it is possible for our products to be put into practical application because of the high accuracy and real-time.

Defensins are important components of innate host defence system against bacteria, fungi, parasites and viruses. Here, we predicted six potential defensin genes from the genome of the scorpion Mesobuthus martensii and then validated four genes from them via the combination of PCR and genomic sequence analysis. These four scorpion defensin genes share the same gene organization and structure of two exons and one phase-I intron with the GT-AG rule. Conserved motif and phylogenetic analysis showed that they belonged to the members of the invertebrate cysteine-stabilized α-helix/β-sheet motif defensin (CSαβ) defensin family. All these four CSαβ defensin genes have the expression feature of constitutive transcription (CON) by the whole scorpion infection model, promoter sequence analysis and dual luciferase assays. Further evolution and comparison analysis found that the invertebrate CSαβ defensin genes from most of arachnids and mollusks appear to share the expression pattern of CON, but those from insects and lower invertebrates (nematodes, annelids, cnidarians and sponges) seem to have identical inducible transcription (IND) after being challenged by microorganisms. Together, we identified four scorpion CSαβ defensin genes with the expression feature of CON, and characterized the diversified expression patterns of the invertebrate CSαβ defensin genes, which will shed insights into the evolution of the invertebrate CSαβ defensin genes and their expression patterns.

The charge release and related mechanisms for Pb(In1/2Nb1/2)–Pb(Mg1/3Nb2/3)–PbTiO3 (PIN–PMN–PT) ferroelectric crystals under one-dimensional shock wave compression were investigated using discharge current profile measurement, by which the piezoelectric stress coefficient e31 and the phase transition (from tetragonal to orthorhombic phase) pressure were obtained, being −2.9 C/m2 and 2.3 GPa, respectively. Based on experiment results and thermodynamics analysis, it was found that the one-dimensional shock compression favored ferroelectric phase, being different from the effect of hydrostatic pressure, which favored paraelectric phase. This phenomenon can be attributed to the crystal anisotropy and electromechanical coupling effects as one-dimensional shock compression is applied to PIN–PMN–PT ferroelectric crystals.

PZT 95/5 ferroelectric ceramic with niobium doped has been assembled for the pulsed power supply, and the electrical current output has been investigated under the action of shock wave in a “normal mode”. The PZT 95/5 ferroelectric ceramics are shocked simultaneously by two shock waves from the two parallel surfaces, therefore a sandwich‐structured ferroelectric power supply is formed. Double current output is expected when it is compared to the single shock wave loading structure. Theoretical calculation was conducted and a good agreement with the experiment is presented.

The effects of hydrostatic and one-dimensional (1D) compression pressure on the phase transition of perovskite ferroelectric crystal were comparably investigated via the measurement of polarization P r with respect to applied pressure and the Landau–Devonshire (LD) phenomenological approach. The results showed that hydrostatic pressure can induce ferroelectric-to-paraelectric phase transition, while 1D compression can stablize the ferroelectric phase. This phenomenon was very different from the phase transitions of metal crystals, such as iron. In the framework of LD phenomenological theory, this phenomenon is believed to be associated with the strong anisotropy and electromechanical coupling which exists in ferroelectrics under high pressure. On the other hand, the piezoelectric stress coefficient e 31 and piezoelectric strain coefficient d h for PIN-PMN-PT crystal were obtained as −2.9 C m−2 and 80 pC N−1, respectively.

Ferroelectric phase transitions and electromechanical properties of BaTiO3 (BT) and PbTiO3 (PT) crystals under one-dimensional shock wave compression were investigated using Landau-Ginzburg-Devonshire phenomenological approach. The results showed that the Curie temperature of both BT and PT increased with increasing pressure. Under highest shock wave compression, the orthorhombic phase was the stable state for BT, while no ferroelectric-ferroelectric phase transition was induced for PT. At room temperature, the electromechanical parameters for PT and BT were found to decrease with increasing one-dimensional compression, except for the dielectric susceptibility e22 and piezoelectric coefficient e24 of tetragonal BT. The variations of dielectric and piezoelectric parameters were analyzed according to the elastic Gibbs free-energy.

The hydrostatic piezoelectricity of Pb ( Mg 1/3 Nb 2/3)–x PbTiO 3 (PMN–xPT) ceramics and PMN–0.32PT and Pb(Mg1/3Nb2/3)–Pb(In1/2Nb1/2)–PbTiO3 (PMN–PIN–PT) crystals were investigated through a quasi-static method. The results showed that pressure-induced depolarization occurred in PMN–xPT ceramics when pressure was above about 50 MPa, while there was no obvious pressure-induced depolarization for PMN–0.32PT and PMN–PIN–PT crystals in the whole pressure range (0~530 MPa). The hydrostatic piezoelectric coefficient d h of PMN–0.32PT and PMN–PIN–PT crystals was nearly independent of pressure. The d h of mono-domain orthorhombic and tetragonal phase crystals is slightly larger, on the order of 100 pC/N. In addition, the relationship between the hydrostatic piezoelectric coefficient d h and the longitudinal and transverse piezoelectric coefficients d33 and d31 for different crystal systems was summarized.

Pyroelectric properties of rhombohedral and tetragonal single crystals Pb(In1/2Nb1/2)-Pb(Mg1/3Nb2/3)-PbTiO3 (PIN-PMN-PT) were investigated, with temperature from −100 °C to 100 °C. At room temperature, the pyroelectric coefficient p and the figure of merit Fd of rhombohedral crystals are 7.81 × 10−4 C/m2 K and 10.9 × 10−5 Pa−1/2, respectively, and 6.84 × 10−4 C/m2 K and 11.67 × 10−5 Pa−1/2, respectively, for tetragonal crystals. Although the coefficient p and Fd at room temperature are similar for rhombohedral and tetragonal crystals, the Fd of tetragonal crystal is much more stable with respect to temperature, owing to its higher phase transition temperature and stable mono-domain state. From room temperature to 100 °C, the Fd of rhombohedral crystal decreases from 10.74 × 10−5 Pa−1/2 to 5.3 × 10−5 Pa−1/2, while that of tetragonal crystals is nearly independent of temperature. Such investigation reveals that tetragonal PIN-PMN-PT crystal is more suitable for uncooled infrared detectors and imagers when c...

The electromechanical properties of rhombohedral single crystals Pb(Mg1/3Nb2/3)-Pb(In1/2Nb1/2)-PbTiO3 (PMN-PIN-PT) were investigated under hydrostatic pressure from 0.1 to 456 MPa. Due to pressure-induced morphotropic phase boundary moving, the piezoelectric coefficients and electromechanical coupling factors of PMN-PIN-PT crystals were found to decrease by ∼10% and ∼2%, respectively. The mechanical quality factor Q was found to dramatically decrease, because the domain wall motion and friction between vibrator and pressure-transmitting fluid were enhanced under hydrostatic pressure. On the other hand, the pressure induced depolarization and phase transition were not observed in the experimental pressure range.

The influence of the hydrostatic pressure on the piezoelectric response for tetragonal BaTiO3 and PbTiO3 monodomain crystals is investigated using Landau–Ginzburg–Devonshire phenomenological approach. It is shown that hydrostatic pressure could enhance the piezoelectric properties in some directions of crystals. The piezoelectricy enhancement is attributed to the hydrostatic pressure-induced flattening of the elastic Gibbs free-energy profile and its corresponding dielectric softening. For BaTiO3 at 285 K, with increasing pressure, the free-energy profile tends to become flat along the polar [001]c direction, facilitating the dilatation and contraction of polarization. So the dielectric softens and the d33 obviously increases in the [001]c direction. But in the direction perpendicular to the polarization, the free-energy profile goes to steepen, which restrains the polarization rotation away from the [001]c polar axis and in turn makes the shear piezoelectric coefficient d15 decreased. As a result, the ma...