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Ablation of TiO2 surface using a double-pulse femtosecond laser was studied applying plasma model calculations and experimental work. The free electron decay time measured by using the double-pulse breakdown threshold method was 550 fs for TiO2. A plasma model is applied with the experimentally derived decay time constant for TiO2 surface ablation. The transient electron density evolution during the TiO2 surface ablation with a double-pulse femtosecond laser was calculated. The ablation experiment using a double-pulse femtosecond laser indicated that the ablation threshold depended on calculated electron density. Furthermore, ablated crater diameter near the threshold was found to depend on the laser fluence with a constant electron density.

SiC MOSFET with three-section edge termination is investigated in this paper. The edge termination for SiC MOSFET is divided into three sections with different field limited rings and the space between rings, which benefits to achieve uniform electric field and high breakdown voltage (BV). The degradation mechanism of BV and on-resistance during high temperature reverse bias (HTRB) and high temperature gate bias (HTGB) experiment are revealed. For HTRB, positive oxide trapped charge generation on SiC/SiO2 surface enhances the electric field peak at breakdown point, which is responsible for BV decreasing. For HTGB, negative oxide trapped charge generation on SiC/SiO2 surface is responsible for the increase of threshold voltage and on-resistance.

An ultra-low specific on-resistance 700 V lateral double-diffused MOSFET (LDMOS) with a buried super junction (BSJ) layer is proposed. [1–9] Buried P-pillars in the LDMOS can be depleted by neighboring N-pillars, overlying and underlying N-drift regions simultaneously, thus allowing a higher doping concentration. Consequently, the doping concentration of either the N-drift regions or N-pillars, or both, may also be increased therewith to compensate the surplus charges in the P-pillars. Compared with conventional surface super junction (SSJ) LDMOS, in which the super junction layer is implemented at the upper surface of the drift region, and P-pillars can only be depleted by the adjacent N-pillars and the N-drift regions beneath, the proposed novel LDMOS structure may have a lower specific on-resistance (Ron,sp) while maintain the same breakdown voltage (BV). Simulation results indicate that the Ron,sp of the novel structure is only 80.5 mΩ cm2 with a high BV of 750 V, which is reduced by 17% in comparison with the Ron,sp of a conventional SSJ LDMOS.

In this study, the accuracy and generality of stress calculation for a plate containing double holes via Schwarz alternating method was investigated. The original Schwarz alternating method with inverse mapping function shows a good performance in terms of the stress solution for a plate containing two arched holes. However, for a plate containing two holes with corners, evitable error may be produced during the calculation because of the unsatisfying accuracy of inverse mapping function. This error is particularly obvious in the stress calculation for a plate containing two triangular holes. To address the problem, an improved Schwarz alternating method without the consideration of inverse mapping function was proposed in this study. The coordinate transformation of points around hole boundaries is realized by an optimization method instead of the inverse mapping function, which leads to little error during the calculation and thus improves the stress solution accuracy especially for plates containing holes with corners. With the employment of the improved method, the influences of connecting angle and lateral pressure coefficient on stress solutions for plates containing double U-shaped holes were discussed. In addition, DEM simulations were further conducted to study the influence of stress characteristics on the failure patterns of rock mass. The result shows that the hoop stress linearly relates to lateral pressure coefficient in the elastic plate and fractures always initiate around hole boundaries where high stress concentrates.

In this work, a split gate trench MOSFET (SGT) with shield layer (SL) is proposed to improve electrical characteristics. The SL modulates charge division of ionized donor atoms in drift region during depletion spreading. As a result, ionized donors electrically coupled to gate are dramatically reduced, thus lowering gate-drain charge (QGD). On the other hand, the SL structure increases energy band of channel region to address drain induced barrier lowering (DIBL) issue while maintaining a lower channel length and doping concentration. Significant reductions in on-resistance (RON), gate charge (QG), and total power losses are confirmed by simulations. The proposed SGT with SL achieves a switching figure of merit (RON × QG) of 30.46 mΩnC, which is 35.5% smaller than conventional trench MOSFET technology, but almost without impacting other fundamental parameters.

In this study, complex variable theory was employed to study the stress distribution for rock mass containing a hole with complex shapes. The method of mapping function calculation using optimization technique was investigated and improved. The shape-related mapping function was defined for parameter analysis. A new objective function for mapping function determination was developed to calculate related parameters without the consideration of restrictive conditions between boundary points in z-plane and ζ-plane, which significantly simplified the calculation process. In addition, the mapping function for planes containing a rotated hole was deducted to simplify analytical stress solution process for holes under complex stress conditions. Finally, for six kinds of holes with typical shapes in practical rock engineering, the mapping functions were determined, and the external analytical stress distribution were further presented. The analytical solutions combined with numerical and experimental results show that holes with arched boundaries suffer less stress concentration compared with those with corners. Hole shape mainly affects the stability of rock containing a hole via its influence on stress concentration extent around the hole.

Lean-oxygen environment caused by methane in high gassy coal mine goaf has a significant influence on the prediction index gases of residual coal spontaneous combustion. The coal sample from Xishan coalfield in China was used to conduct the low-temperature oxidation experiments under different lean-oxygen environments. The experimental results show that different lean-oxygen environments had a significant delay effect on the formation of CO, CO2, H2 and C2H6, and the lower the O2 concentration, the more obvious the delay effect, and the delay effect of methane was greater than that of N2. A lean-oxygen environment caused by methane also had a significant influence on the values of CO/ΔO2 ratio and CO2/ΔO2 ratio. However, when the temperature was T can be accurately expressed by exponential function. The absolute amount of CO, CO2 and C2H6 generated by 1 k g residual coal ( C CO , C CO 2 and C C 2 H 6 ), which can reduce the influence of air leakage and residual coal mass on prediction index gases, were introduced to predict the spontaneous combustion in high gassy coal mine goaf. Then, the distribution diagrams of C CO , C CO 2 and C C 2 H 6 with temperature and O2 concentration were obtained, so as to accurately predict the degree of spontaneous combustion in high gassy coal mine goaf. The research results are of great significance to the prevention of spontaneous combustion in goaf of high gassy mine.

Single event burnout (SEB) of NLDMOSFETs on SOI initiated by pulsed laser irradiation is demonstrated for the first time. The sensitive region of the device for SEB and the effects of reverse voltage and laser energy are explored. The data indicate that the device is most sensitive to laser pulses in the drift region near the P-well. This is influenced by the electric field distribution in the drift region of the LDMOSFET at the time of the laser pulse. The SEB threshold depends on both the applied reverse voltage and the laser pulse energy. The laser pulse energy at a given reverse voltage required to initiate SEB is inversely proportional to the laser spot distance from the P-well. Simulation results for the device drain current following the radiation pulse indicate that the behavior of the npn parasitic bipolar transistor inherent in the LDMOS structure can explain the observations.

The copper in the waste printed circuit boards (WPCBs) is cleanly recycled by physical methods and presented in the form of nano copper particles by hydrometallurgical, which provides environmental approach to the advanced utilization of metal copper. Copper in WPCBs was first pre-concentrated by gradient enrichment process including gravity separation, mechanical grinding and flotation. The leaching method was then used to dissolve copper from the flotation concentrate in ammoniacal/ammonium salt solutions. Subsequently, reduction treatment was conducted to synthesize nano-copper from leaching solution. The enrichment results of the clean physical separation process show that the grade of copper increased from 16.22% to –38.05% by gravity separation, and the grade of copper further increased to 72.62 % by flotation after dissociation, which avoids overgrinding of low value components. Copper nanoparticles can be prepared effectively, and the recovery of copper in the leaching process reaches 99 %. The particle size of copper nanoparticles obtained by ascorbic acid reduction is tens of nanometers, and the surface of copper nanoparticles is smooth and nearly spherical. The present study proposes an environmentally friendly process of preparing nano-copper from the copper in WPCBs.

A novel triple reduced surface field (RESURF) lateral double-diffused metal oxide semiconductor field effect transistor (LDMOS) with partial linear variable doping (LVD) N-type top (N-top) layer is proposed in this paper. Compared with the conventional triple RESURF LDMOS, a partial LVD N-top layer is introduced in the surface of N-well, providing a low on-resistance conduction path and leading to an optimized surface electric field, which alleviates the inherent tradeoff between the breakdown voltage (BV) and specific on-resistance (Ron,sp). With the n-drift region length of 70 μm, the novel triple RESURF LDMOS obtains a high BV of 847 V and a low Ron,sp of 79 mΩ cm2 which are 76 V higher and 46 mΩ cm2 lower than those of the conventional triple RESURF LDMOS. Therefore, the novel triple RESURF LDMOS can greatly improve the tradeoff between BV and Ron,sp. Furthermore, compared with the other existing technologies in the high BV level, the novel triple RESURF LDMOS can achieve a highest figure of merit (FOM, defined as BV2/Ron,sp) of 9.08 MW/cm2 and the conventional RESURF silicon limits are broken.

Cost-effective mask-sharing technology for the 200 V silicon-on-insulator (SOI) lateral insulated gate bipolar transistor (LIGBT) and p-channel lateral double-diffused MOS (PLDMOS) are proposed in this paper. N-well and P-body implantations are shared as an N-buffer implantation of the LIGBT and P-buffer implantation of the PLDMOS, respectively, which reduces two masks compared with the conventional process. The structure and process parameters for LIGBT and PLDMOS with the new process are optimized by simulation to achieve good performance. The experimental results indicate that the LIGBT and PLDMOS using the new process maintain the same performance compared to the conventional devices.

A high-voltage thick layer SOI field p-channel LDMOS (pLDMOS) with multiple field plates based on 11-μm-thick silicon layer and 1-μm-thick buried oxide layer is presented in this paper. The thick gate oxide layer is formed by field oxide process to endure the high voltage between the source and gate electrodes. The field implant (FI) technology is adopted to eliminate channel discontinuity at the bird's beak region. Multiple field plates constructed by polysilicon and metal layer are adopted to modulate electric field distribution of the depleted drift region. The SOI field pLDMOS with off-state breakdown voltage (BV) of −240 V is experimentally realized, which can be widely used for simplifying the design of level shifting.

A novel low turnoff loss carrier stored (CS) silicon-on-insulator (SOI) lateral insulated gate bipolar transistor (LIGBT) with trench gate barrier (CS SOI TGLIGBT) is proposed. The proposed CS SOI TGLIGBT features a trench gate inserted between the pwell and n-drift. Firstly, the trench gate acts as a hole barrier to prevent the hole from injecting directly into pwell in the on-state, which introduces carrier stored effect and realizes a uniform carriers distribution in the n-drift region, resulting in a decrease of the on-state voltage drop (Von). Secondly, due to the carrier stored effect and the assisted depleted effect induced by the trench gate, large number of carriers can be quickly removed at the initial turnoff process, leading to a decrease of turnoff loss (Eoff). The influences of gate trench barrier on Von and Eoff are investigated. Simulation results show that the proposed CS SOI TGLIGBT can achieve a 59% lower Eoff compared with the conventional SOI trench gate LIGBT at the same Von of 1.15 V.

The back gate (BG) induced breakdown mechanisms for thin layer SOI Field P-channel LDMOS (FPLDMOS) are investigated in this paper. Surface breakdown, bulk breakdown and punch-through breakdown are discussed, revealing that the block capability depends on not drain voltage (Vd), but also BG voltage (VBG). For surface breakdown, the breakdown voltage (BVs) increases linearly with VBG increasing. An expression of BVs on VBG is given, providing a good fitting to measured and simulated results. Bulk breakdown with a low breakdown voltage is attributed to high VBG. VBG induces depletion in n-well, giving rise to punch-through breakdown. A design requirement for the thin layer SOI FPLDMOS is proposed that breakdown voltages for the three breakdown mechanisms are compelled to be higher than the supply voltage of switching IC.

Composite vessels are used as replacements for metal vessels, because they offer significant weight savings. This paper describes the in-situ curing of such vessels, using compressed air to heat the liner of a vessel and realize the curing and molding of the vessel. To overcome uneven heating, a heating gasbag with small holes is inserted into the liner of the vessel to provide heating. A simulation program based on a mathematical model is developed using the finite element method on an ANSYS software platform. The factors affecting the curing temperature, degree of curing, and deformation of a composite vessel are identified by a numerical simulation. The curing temperature, the degree of curing, and the deformation of the composite vessel are influenced by the room temperature, surface convection coefficient, fiber volume fraction, and thickness of the composite vessel, although to different degrees. The type of metal used for the liner has little influence on the curing.

Flotation is an effective method for recovering metals from dissociated waste printed circuit boards (WPCBs). The difference in dissociation and flotation behaviors of various size particles are revealed in this study. The metal and impurity in 3–1 mm particles were first dissociated under the impact force. The particle morphology of each size particle in the grinding products was analyzed by scanning electron microscope (SEM). SEM results show that the metal particles presents flake shape, and the dissociated glass fiber shows rod shape. The size composition and element distribution appear bimodal distribution. Flotation results present that the distribution rate of particles in floats increases with the decrease of particle size, and increases with the increase of collector dosage. In addition, the removal rate of Si and Cu reveals the same trend. The finer particles are more sensitive to the change of collector dosage. The removal rates of Si in 1–0.25, 0.25–0.074 and −0.074 mm reaches 59.80%, 95.69% and 95.59% with 4 kg/t collector. Under the action of the collector, the floatability of Cu particles with organic matter adhered to the surface is enhanced, which results in the higher impurity removal and Cu loss.

High-voltage (HV) integrated power devices are widely used in many applications, including alternating current/direct current (AC/DC) power converter, HV gate driver integrated circuit (IC) and light emitting diode (LED) driver IC, etc. Among these applications, AC/DC power converter is essential for almost all power systems operated in the DC conditions. As a power switch in the AC/DC converter, the fundamental performance requirement of these power devices is to withstand a high voltage of 500–900 V and simultaneously have a low power loss for its efficient conversion. Therefore, several device technologies have been proposed to realize a high breakdown voltage (BV) and a low specific on-resistance (Ron,sp), such as reduced surface field (RESURF) technology, lateral super-junction (SJ) structure, lateral insulated-gate bipolar transistor (LIGBT), integrated vertical structure and junction termination technology. In this paper, a comprehensive review of the development and prospect of these technologies in AC/DC switching application is presented. Furthermore, analytic Ron,sp-BV models for some typical device structures, the possible strategies of Bipolar - Complementary metal oxide semiconductor - Double-diffused metal oxide semiconductor (BCD) platform integrated with vertical SJ devices, partial silicon-on-insulator (SOI) BCD technology, low gate charge (Qg) HV integrated power devices and wide bandgap technology are also described.

Seven pairs of new enantiomeric sesquiterpenoids, (+)/(−)-phaeocauline A − G [(+)/(−)-1–7], were isolated from the rhizomes of Curcuma phaeocaulis by chiral HPLC separation. Their structures, including absolute configurations, were determined by spectroscopic analyses and ECD data. The isolates were assessed for vasorelaxant, anti-platelet aggregative, and neuroprotective activities. Enantiomers (+)-1 and (−)-1 showed similar activity against abnormal platelet aggregation induced by arachidonic acid, while their C-4 epimers (+)-2 and (−)-2 were inactive, which indicated that those effects were stereoselective, but not enantioselective. Compounds (+)/(−)-3–5 exhibited vasorelaxant effects against KCl-induced contraction of rat aortic rings.

Aims Liver fibrosis is a crucial pathological feature which could result in cirrhosis and hepatocarcinoma. But until now, there is no favourable treatment for it. Apigenin (APG) is a flavonoid, which exhibits efficient anti-liver fibrosis activity, but its underlying mechanisms were rarely studied. So this work aims to estimate the potential therapeutic action of APG on liver fibrosis rats and to gain insight into its system-level mechanisms. Main methods Hepatic fibrosis was induced by CCl4 in Wistar rats, and APG was given in the light of the regimen. Biochemical indexes, histopathological change and immunohistochemistry of liver were evaluated. The optimal effect group of APG was selected for further transcriptomic and proteomic analysis. Key findings APG ameliorated liver fibrosis via reducing the levels of AST, ALT, ALP, LDH, Hyp, TP, TB, DB, HA, LN, PCIII and IV-C, mitigating fibrosis and inflammation of liver in H&E and Masson staining. Mechanistically, APG elevated the activity of ALB, SOD and GSH-PX with reducing the level of MDA. The results of microarray and TMT revealed that 4919 genes and 4876 proteins were differentially expressed in the APG and model groups. Besides, transcriptomics and proteomics analyses unfolded 120 overlapped proteins, enriched in 111 GO terms containing apoptotic process, angiogenesis, cell migration and proliferation, etc. Meanwhile, KEGG pathway analysis showed that 26 pathways containing HIF-1/MAPK/eNOS/VEGF/PI3K/Akt signaling pathway, regulation of actin cytoskeleton and focal adhesion mostly. Significance APG can ameliorate CCl4-induced liver fibrosis via VEGF-mediated FAK phosphorylation through the MAPKs, PI3K/Akt, HIF-1, ROS, and eNOS pathways, which may hopefully become the anti-liver fibrosis activity of natural product.

Background The recombinant yellow fever-17D-dengue virus, live, attenuated, tetravalent dengue vaccine (CYD-TDV) has undergone extensive clinical trials. Here safety and consistency of immunogenicity of phase III manufacturing lots of CYD-TDV were evaluated and compared with a phase II lot and placebo in a dengue-naive population. Methods Healthy 18–60 year-olds were randomly assigned in a 3:3:3:3:1 ratio to receive three subcutaneous doses of either CYD-TDV from any one of three phase III lots or a phase II lot, or placebo, respectively in a 0, 6, 12 month dosing schedule. Neutralising antibody geometric mean titres (PRNT50 GMTs) for each of the four dengue serotypes were compared in sera collected 28 days after the third vaccination—equivalence among lots was demonstrated if the lower and upper limits of the two-sided 95% CIs of the GMT ratio were ≥0.5 and ≤2.0, respectively. Results 712 participants received vaccine or placebo and 614 (86%) completed the study; 17 (2.4%) participants withdrew after adverse events. Equivalence of phase III lots was demonstrated for 11 of 12 pairwise comparisons. One of three comparisons for serotype 2 was not statistically equivalent. GMTs for serotype 2 in phase III lots were close to each other (65.9, 44.1 and 58.1, respectively). Conclusions Phase III lots can be produced in a consistent manner with predictable immune response and acceptable safety profile similar to previously characterised phase II lots. The phase III lots may be considered as not clinically different as statistical equivalence was shown for serotypes 1, 3 and 4 across the phase III lots. For serotype 2, although equivalence was not shown between two lots, the GMTs observed in the phase III lots were consistently higher than those for the phase II lot. As such, in our view, biological equivalence for all serotypes was demonstrated.

A heterogenous Zr-based metal organic framework (UiO-66) encapsulating phosphotungstic acid (HPWs) catalyst (HPWs@UiO-66), was prepared by a simple direct hydrothermal reaction of ZrCl 4 , terephthalic acid, and HPWs in DMF. The as-prepared novel material was very active as the catalyst for the selective oxidation of cyclopentene (CPE) to glutaraldehyde (GA) with environmentally benign hydrogen peroxide as the oxidant. The crystal structure and morphology of UiO-66 were well preserved after the incorporation of HPWs, as confirmed by X-ray diffraction (XRD), SEM, and TEM. Moreover, the XRD, N 2 adsorption, and FT-IR analyses reveal that HPW components could stably exist in the nanocages of UiO-66. FT-IR-CO adsorption experiments indicated that additional Lewis acid sites were present in the HPWs@UiO-66 sample, which were essential to catalyze the selective oxidation of CPE to GA. A proper amount of HPWs and their high dispersion accounted for high catalytic activity. Almost complete conversion of CPE (∼94.8%) and high yield of GA (∼78.3%) were obtained using the 35 wt% HPWs@UiO-66 catalyst. Furthermore, HPW components hardly leached in the reaction solution, enabling the catalyst to be used for three reaction cycles without obvious deactivation.

A novel simulation approach for the breakdown characteristics of SOI high-voltage (HV) PMOS in a fixed power supply application is proposed. The different optimized parameters for the SOI HV PMOS can be achieved by the conventional and proposed simulation approaches. A SOI variation of lateral doping (VLD) field PMOS, which is widely used in the level-shift circuit is investigated by the conventional and novel simulation approaches. For the level-shift circuit with power supply of 400 V, the breakdown voltage (BV) of the optimized SOI VLD field PMOS increases from 520 V with the conventional simulation approach to 646 V with the proposed simulation approach. Moreover, the corresponding optimized doping concentration of p-drift region with the proposed approach is higher than that with the conventional approach, thus greatly reducing the specific on-resistance ( R on,sp ). The SOI VLD field PMOS actually has a more robust breakdown voltage and lower R on,sp in the fixed power supply. The BV and R on,sp of SOI HV PMOS can be truly reflected and the effect of reduced bulk field (REBULF) is revealed in the fixed HV power supply by employing the novel simulation approach.

The reduction of breakdown voltage (BV) influenced by high voltage interconnection (HVI) is a key problem in power integrated circuit, which essentially is that the modulation of electric field distribution at the device surface caused by HVI. In this paper, we review the developments of the methods to shield HVI including thick insulating film technology, field reduction layer technology, field plate technology and self-shielding technology. The four kinds of HVI technologies prevent BV degradation from the introduced adverse charge induced by interconnections in different ways. Thick insulting film technology increases the distance between the HVI and surface of silicon. Field reduction layer technology uses additional doping layers with optimized impurity concentration to enhance the depletion of the drift region under HVI. Field plate technology shields the influence of HVI with various field plate structures. Self-shielding technology makes HVI avoid crossing over high voltage junction terminal (HVJT), thus no additional shielding structure is needed. The divided reduced surface field (RESURF) technology solves the leakage current in the self-shielding structure.

This paper proposes a 700 V narrow channel region triple-RESURF (reduced surface field) n-type junction field-effect transistor (NCT-nJFET). Compared to traditional structures, low pinch-off voltage ( V P ) with unobvious drain-induced barrier lowering (DIBL) effect and large saturated current ( I Dsat ) are achieved. This is because p-type buried layer (Pbury) and PWELL are introduced to shape narrow n-type channel in JFET channel region. DIBL sensitivity ( S DIBL ) is firstly introduced in this paper to analyze the DIBL effect of high-voltage long-channel JFET. Ultra-high breakdown voltage is obtained by triple RESURF technology. Experimental results show that proposed NCT-nJFET achieves 24-V V P , 3.5% S DIBL , 2.3-mA I Dsat , 800-V OFF-state breakdown voltage (OFF-BV) and 650-V ON-state breakdown voltage when V GS equals 0 V (ON-BV).

A novel 1200-V ultra-thin partial silicon-on-insulator (PSOI) lateral double-diffusion metal oxide semiconductor (LDMOS) with n-type buried (n-buried) layer (NBL PSOI LDMOS) is proposed in this paper. The new PSOI LDMOS features an n-buried layer underneath the n-type drift (n-drift) region close to the source side, providing a large conduction region for majority carriers and a silicon window to improve self-heating effect (SHE). A combination of uniform and linear variable doping (ULVD) profile is utilized in the n-drift region, which alleviates the inherent tradeoff between specific on-resistance ( R on,sp ) and breakdown voltage (BV). With the n-drift region length of 80 μm, the NBL PSOI LDMOS obtains a high BV of 1243 V which is improved by around 105 V in comparison to the conventional SOI LDMOS with linear variable doping (LVD) profile for the n-drift region (LVD SOI LDMOS). Besides, the 1200-V NBL PSOI LDMOS has a lower maximum temperature ( T max ) of 333 K at a power ( P ) of 1 mW/μm which is reduced by around 61 K. Meanwhile, R on,sp and T max of the NBL PSOI LDMOS are lower than those of the conventional LVD SOI LDMOS for a wide range of BV.

In this paper, ESD protection devices for power rails in a PDP scan IC are studied. By numerical simulation, current flow distribution of LIGBT under ESD stress is analyzed. The proposed latchup free LIGBT has additional discharge mechanism to optimize the discharge path, and much smaller discharge resistance can be obtained. As demonstrated by TLP test, optimized LIGBT has 33% larger It2 than HV diode, and its Vt2 is only 27 V higher than its breakdown voltage.

Supported gold catalysts Au/OMS-2 and Au/La-OMS-2 were prepared and used for liquid phase oxidation of cyclohexene with oxygen as an oxidant. These catalysts were characterized by XRD, SEM, TEM and EDX. The reactions were carried out in an autoclave at 80 °C without any solvent. Effects of Au content and La content on catalytic performance were studied. Au/La-OMS-2 (0.24) was found to be an efficient catalyst for the oxidation of cyclohexene with a high conversion (48.0%). More than 86% selectivity for ∑ C6 (including cyclohexene oxide, 2-cyclohexene-1-ol, 2-cyclohexene-1-one) was obtained.

The H5N1 avian influenza virus (AIV) has widely spread in Asia, Europe and Africa, making a large amount of economic loss. Recently, our research group has screened a common neutralizing monoclonal antibody named 8H5, which can neutralize almost all H5 subtype AIV ever isolated so far. Obviously, this monoclonal antibody would benefit for research and development of the universal AIV vaccine and design of the drug against H5N1 AIV in high mutation rate. In this study, the homology modeling was applied to generate the 3D structure of 8H5 Fab fragment, and “canonical structure” method was used to define the specified loop conformation of CDR regions. The model was subjected to energy minimization in cvff force field with Discovery module in Insight II program. The resulting model has correct stereochemistry as gauged from the Ramachandran plot calculation and good 3D-structure compatibility as assessed by interaction energy analysis, solvent accessible surface (SAS) analysis, and Profiles-3D approach. Furthermore, the 8H5 Fab model was subjected to docking with three H5 subtype hemagglutinin (HA) structures deposited in PDB (ID No: 1jsm, 2ibx and 2fk0) respectively. The result indicates that the three docked complexes share a common binding interface, but differ in binding angle related with HA structure similarity between viral subtypes. In the light of the three HA interfaces with structural homology analysis, the common neutralizing epitope on HA recognized by 8H5 consists of 9 incontinuous amino acid residues: Asp68, Asn72, Glu112, Lys113, Ile114, Pro118, Ser120, Tyr137, Tyr252 (numbered as for 1jsm sequence). The primary purpose of the present work is to provide some insight into structure and binding details of a common neutralizing epitope of H5N1 AIV, thereby aiding in the structure-based design of universal AIV vaccines and anti-virus therapeutic drugs.

Gold nanoparticles were stabilized on alumina support by silica via a surface sol–gel post-modification method and applied for the catalytic cyclohexane oxidation to cyclohexanone and cyclohexanol using oxygen in the absence of any solvent and initiator. The results show that the surface doping of alumina support with silica is highly effective in stabilizing gold nanoparticles subjected to calcination at 500 °C for 3 h. Moreover, the catalytic activity in terms of specific reaction rate and the selectivity to cyclohexanone are appreciably enhanced probably due to a decreased acidity and hydrophilicity by surface substitution of alumina with silica.

The structural details of hepatitis C virus (HCV) have been elusive because of the lack of a robust tissue culture system for producing an adequate amount of virions from infectious sources for in-depth three-dimensional (3D) structural analysis. Using both negative-stain and cryo-electron microscopy (cryoEM), we show that HCV virions isolated from cell culture have a rather uniform size of 500 Å in diameter and that recombinantly expressed HCV-like particles (HCV-LPs) have similar morphologic, biophysical and antigenic features in spite of the varying sizes of the particles. 3D reconstructions were obtained from HCV-LPs with the same size as the HCV virions in the presence and absence of monoclonal antibodies bound to the E1 glycoprotein. The 3D reconstruction of HCV-LP reveals a multilayered architecture, with smooth outer-layer densities arranged in a ‘fishbone’ configuration. Reconstruction of the particles in complex with anti-E1 antibodies shows that sites of the E1 epitope are exposed and surround the 5-, 3- and 2-fold axes. The binding pattern of the anti-E1 antibody and the fitting of the structure of the dengue virus E glycoprotein into our 3D reconstructions further suggest that the HCV-LP E1 and E2 proteins form a tetramer (or dimer of heterodimers) that corresponds morphologically and functionally to the flavivirus E homodimer. This first 3D structural analysis of HCV particles offers important insights into the elusive mechanisms of HCV assembly and maturation.

Previously, an mAb 10F7 was developed against H5N1 hemagglutinin, which was highly specific to 34 different H5N1 strains and showed good neutralizing activity. In the present study, the single-chain fragment of the antibody was cloned into a prokaryotic vector and then expressed in E. coli. The activity of the scFv was tested in hemagglution inhibition and neutralization experiment. Two H5N1 virus strains were inhibited to bind erythrocyte cells by the scFv while the H9 virus was not. Also, five H5N1 virus strains were neutralized during infecting MDCK cells. These results showed an approachable method for developing therapeutic antibody to H5N1 virus.

A cell monolayer radioimmunoassay was established to detect hepatitis B virus (HBV)-binding activity. HBV was shown to bind to HepG2 and HuH7 cells, but not to LTK- and HeLa cells. The binding activity was inhibited by peptide 21-47 from the large hepatitis B surface antigen (L-HBsAg) region, but not by other peptides from the L- and middle-HBsAg. A monoclonal antibody to L-HBsAg (MA18/7) and a polyclonal antibody to HBsAg (anti-HBs) also inhibited the binding. However, only the Fab fragment of MA18/7 showed blocking activity, suggesting that these two antibodies may neutralize virus by different mechanisms. Excess HBV was able to saturate the binding activity of HepG2 cells. The virus was also shown to be internalized; virus DNA was detected in the cytoplasmic fraction 1-2 hr postadsorption and was associated with the nuclear fraction 2 hr later. Furthermore, immunoprecipitation experiments showed that the virus DNA remained encapsidated 48 hr after internalization. Nuclear fractionation experiments showed that the encapsidated HBV DNA remained associated with the nuclear membrane. Trypsinization of intact nuclei resulted in disassociation of the nucleocapsid from the nuclear membranes, suggesting that the nuclear membrane presents a barrier to intact HBV virions or nucleocapsids. This may explain why HepG2 cells are refractile to infection although permissive for HBV replication after transfection of viral DNA.