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The isoselective ring-opening polymerization of rac-LA is a challenging goal. In this work, a series of potassium amidate complexes (K1–K10) were easily prepared and characterized using the 1H/13C NMR spectrum. The molecular structures of potassium complexes K2 and K10 were determined by X-ray diffraction, which showed that both were two-dimensional coordination polymers due to the adjacent π interactions of the aryl. In the presence of benzyl alcohol (BnOH), all of the potassium complexes exhibited a high catalytic activity toward the ring-opening polymerization of L-lactide and rac-LA, yielding linear polylactides capped with BnO or CH3O end groups. A significant solvent effect on the ROP of the L-LA was observed, with a superior efficiency in toluene than in THF and CH2Cl2. These complexes are iso-selective and act as active catalysts for the controlled ring-opening polymerization of rac-lactide, with a Pm from 0.54 to 0.76. This is a rare example of simple alkali metal complexes for the isoselective ROP of rac-lactide. The substituent greatly affected the monomer conversion and isoselectivities.

Through activation with LiCH2SiMe3 or LiN(SiMe3)2, zinc(ii) chloride complexes bearing 5,6,7-trihydroquinolin-8-amines appended with pendant diphenyl phosphine units displayed remarkable catalytic activity for ROP of ε-caprolactone.

To explore room-temperature strengthening and high-temperature ductility, a lightweight novel Mg-1.85Gd-0.64Al-0.62Zn alloy was fabricated by innovative multidirectional forging and a hot-rolling technique. Microstructures and mechanical properties were studied at room and elevated temperatures with an optical microscope, an X-ray diffractometer, and a tensile tester. An ultimate tensile strength of 260 MPa, yield strength of 171 MPa, and elongation of 20.4% were demonstrated at room temperature. The room-temperature strengthening mechanisms were identified by strengthening the model estimation. A type C Portevin-Le Chatelier effect was discovered and elucidated in this alloy. X-ray diffraction analysis revealed that the phase composition is α-Mg solid solution and (Mg, Al)3Gd, Al7Zn3, and Al2Gd intermetallic compounds. Examination of the microstructure at elevated temperatures revealed that dynamic recrystallization and dynamic grain growth occur. In particular, it was discovered that bimodal microstructures or incomplete dynamic recrystallization microstructures exist in high-temperature deformation. A maximum quasi-superplasticity of 228.4% was demonstrated in this alloy at 673 K and 5.0 × 10−4 s−1. Flow stress curves showed that the present alloy exhibits Sotoudeh–Bate curves or a long intermediate strain-hardening stage followed by a strain-softening stage. A modified Zerilli–Armstrong constitutive equation incorporating the number of dislocations was established. The power-law constitutive equation was established to identify the deformation mechanism. Both constitutive models had good predictability. At 673 K and 5.0 × 10−4 s−1, the stress exponent was 4, and the average deformation activation energy was 104.42 kJ/mol. The number of dislocations inside a grain was 146. This characteristic evidence confirmed that dislocation motion controlled by pipe diffusion dominates the rate-controlling process under this condition.

To explore the hot compression behavior and microstructural evolution, fine-grained Al−1.88Mg−0.18Sc− 0.084Er (wt.%) aluminum alloy wires were fabricated with Castex (continuous casting−extrusion) and ECAP-Conform, and their hot compression behavior was investigated at temperatures of 673−793 K and strain rates of 0.001−10 s−1; the microstructures were characterized by optical microscope, X-ray diffractometer, transmission electron microscope, and electron backscattered diffractometer, and the flow stresses were obtained by thermal compression simulator. Microstructural evolution and flow curves reveal that dynamic recovery is the dominant softening mechanism. Continuous dynamic recrystallization followed by dynamic grain growth takes place at a temperature of 773 K and a strain rate of 0.001 s−1; the yielding drop phenomenon was discovered. Hyperbolic sine constitutive equation incorporating dislocation variables was presented, and a power law constitutive equation was established. The stress exponent is 3.262, and the activation energy for deformation is 154.465 kJ/mol, indicating that dislocation viscous glide is the dominant deformation mechanism.

Four examples of para-dibenzocycloheptyl-substituted 2,6-bis(arylimino)pyridyl-iron(II) chloride complexes, [2,6-{(2-R1,4-(C15H13),6-R2C6H2)NCMe}2C5H3N]FeCl2 (R1 = R2 = Me Fe1, Et Fe2, iPr Fe3, R1 = Me, R2 = Et Fe4), have been synthesized and characterized by a combination of IR spectroscopy, elemental analysis and single crystal X-ray diffraction. The molecular structures of Fe2 and Fe4 highlight not only their pseudo-square pyramidal geometries but also the variation in configuration of the two remote dibenzo-fused cycloheptyl rings. When activated with MAO or MMAO, Fe1–Fe4 displayed very high activities for ethylene polymerization by operating effectively at 70 °C/10 atm [up to 7.14 × 107 g(PE) mol−1(Fe) h−1] producing high molecular weight linear polyethylene (as high as 98.7 kg mol−1) with a single melting temperature (Tm: >129.7 °C) as well as various levels of vinyl unsaturation. Even at temperatures up to 100 °C, the polymerization activity remained high [up to 1.46 × 107 g(PE) mol−1(Fe) h−1] underlining the good thermal stability of this catalyst class. By contrast at PC2H4 = 1 atm, all polyethylenes produced using Fe1–Fe4 at run temperatures between 20–60 °C exhibited two melting point values with either MAO (Tm1 93.5–116.2 °C, Tm2 124.9–130.0 °C) or MMAO (Tm1 65.1–85.9 °C, Tm2 116.8–122.8 °C) in line with the bimodality of the lower molecular weight polymers. In particular, when MMAO was employed as a co-catalyst, the polyethylene displayed a wax-like composition and displayed a very narrow dispersity (Mw/Mn range: 1.1–1.6).

Magnesium-lithium alloy is the lightest alloy to date. To explore its room temperature strength and high-temperature ductility, a plate of a new fine-grained Mg-9.13Li-3.74Al-0.31Sr-0.11Y alloy was fabricated by asymmetric rolling, and the rolled plate was subjected to friction stir processing (FSP). The microstructure and mechanical properties at room and elevated temperatures were investigated by optical microscopy, X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and tensile tester. Grain refinement with an average grain size in the α-Mg phase of 1.65 μm and an average grain size in the β-Li phase of 4.24 μm was achieved in the water-cooled FSP alloy. For room temperature behavior, the ultimate tensile strength of 208 ± 4 MPa, yield strength of 193 ± 2 MPa, and elongation of 48.2% were obtained in the water-cooled FSP alloy. XRD and EDS analyses revealed that the present alloy consists of α-Mg and β-Li phases, Al2Y, Al4Sr, MgLi2Al, and AlLi intermetallic compounds. For high-temperature behavior, the maximum superplasticity or ductility of 416% was demonstrated in this fine-grained alloy with an average grain size of 10 μm at 573 K and 1.67 × 10−3 s−1. A power-law constitutive equation was established. The stress exponent was 2.29 (≈2) (strain rate sensitivity 0.44), and the deformation activation energy was 162.02 kJ/mol. This evidence confirmed that the dominant deformation mechanism at elevated temperatures is grain boundary and interphase boundary sliding controlled by lattice diffusion.

A novel dual-phase-dominated fine-grained (5.5 μm) Mg-6.4Li-3.6Zn-0.37Al-0.36Y alloy was fabricated by multidirectional forging and rolling (MDFR); its mechanical properties and microstructural evolution were investigated. The ultimate tensile strength of 286 MPa and elongation of 31.8% were demonstrated in this alloy. The Portevin–Le Chatelier effect was observed in cold-rolled alloy. During MDF, the dominant grain refinement mechanisms of the α-Mg phase are mechanically fragmented grain refinement and deformation-induced in-situ dynamic recrystallization (DRX) grain refinement. However, the dominant grain refinement mechanism of the β-Li phase is deformation-induced in-situ DRX grain refinement. In later stage, thermally activated grain coarsening occurs in both phases. X-ray diffraction analyzes reveal the existence of α-Mg and β-Li phases, Al2Y, and MgLi2Al intermetallic compounds in the MDF state and the existence of α-Mg and β-Li phases, Al2Y, Al12Mg17, and MgLiZn intermetallic compounds in the cold-rolled state. Transmission electron microscopy analyzes show that high-density dislocation pile-up, dislocation tangle, subgrains, and MgLiZn particles exist in the cold-rolled alloy and raise the tensile strength. Texture analyzes reveal that strong {0001} basal texture or basal fiber of α-Mg phase exists, but the texture intensities in this alloy are not high. Annealing does not produce new texture component. A Hall-Petch model was established in this alloy: yield strength = 11.83 + 351.89 times minus square root of grain size. The relationship between critical resolved shear stress and resistance to deformation was modeled. Static recrystallization and grain coarsening during annealing were discussed.

To explore new approaches to severe plastic deformation and the ductility of a multicomponent magnesium–lithium alloy, an ultralight microduplex Mg-9.55Li-2.92Al-0.027Y-0.026Mn alloy was made by novel multidirectional forging and asymmetrical rolling, and the superplasticity behavior was investigated by optical microscope, hot tensile test, and modeling. The average grain size is 1.9 μm in this alloy after multidirectional forging and asymmetrical rolling. Remarkable grain refinement caused by such a forming, which turns the as-cast grain size of 144.68 μm into the as-rolled grain size of 1.9 μm, is achieved. The elongation to failure of 228.05% is obtained at 523 K and 1 × 10−2 s−1, which demonstrates the high strain rate quasi-superplasticity. The maximum elongation to failure of 287.12% was achieved in this alloy at 573 K and 5 × 10−4 s−1. It was found that strain-induced grain coarsening at 523 K is much weaker than the strain-induced grain coarsening at 573 K. Thus, the ductility of 228.05% is suitable for application in high strain rate superplastic forming. The stress exponent of 3 and the average activation energy for deformation of 50.06 kJ/mol indicate that the rate-controlling deformation mechanism is dislocation-glide controlled by pipe diffusion.

A series of spiro-phenanthrene-monoketone/OH derivatives (L1–L6) were synthesized and fully characterized with 1H/13C NMR spectroscopy and elemental analyses. By treating ligands with AlMe3, oxygen-bridged binuclear aluminum complexes (Al1–Al6) were isolated and characterized by 1H/13C NMR spectroscopy. The molecular structures of ligands (L2, L4 and L5) and complex Al1 were determined by single crystal X-ray diffraction. In the presence of benzyl alcohol (BnOH), these aluminum complexes demonstrated high efficiency towards the ring-opening polymerization of e-caprolactone (e-CL), resulting in PCL in a linear manner with the BnO-end group. In addition, complexes Al1 and Al5 exhibited good catalytic activities even without BnOH. Moreover, complexes Al3 and Al6 with the bulkier substituent of iPr at the ortho-position of the arylamines demonstrated better catalytic activities than the analogs. Moreover, substituents on the backbone also affected catalytic behaviors.

Creep is the process by which material occurs at high temperatures and its slow deformation process. -2 since the slow...

To explore the ductility and deformation nature, a new Mg-2.76Li-3Al-2.6Zn-0.39Y alloy has been successfully fabricated by decreasing-temperature multidirectional forging and hot rolling. The maximum elongation to failure of 223.0% was demonstrated in this alloy at a temperature of 633 K and a strain rate of 1.67×10-4 s-1. Flow stress curves and microstructural examination showed that continuous dynamic recrystallization occurred in this alloy at different temperatures and strain rates in most cases, but the flow hardening phenomena appeared at a temperature of 603 K at a strain rate of 5×10-4 s-1 and at 573, 603 and 633 K at a strain rate of 1.67×10-4 s-1. A criterion of grain size changing rate was proposed to judge the occurrence of microstructural evolution mechanisms. A modified Johnson-Cook constitutive model established in this alloy was incorporated into dislocation models to realize the estimation of the dislocation density and the number of dislocations under specific conditions. A power-law constitutive equation was established in this alloy. The relationship between average grain size and Zener-Hollomon parameter was established. It was found that the stress exponent was 3.26, and the average experimental activation energy for deformation was 143.67 kJ/mol; the dislocation density was 3.25×1013 m-2, and the number of dislocations was 59 at 633 K and 1.67×10-4 s-1. All of these results indicate that the predominant deformation mechanism of this alloy under this condition is dislocation glide creep controlled by lattice diffusion.

To improve its strength and ductility, a novel microduplex Mg-7.28Li-2.19Al-0.091Y alloy was designed; its sheets 2 mm in thickness were fabricated by casting, homogenization, and rolling. Mechanical properties and microstructural evolution were investigated by tensile tester, hardness tester, optical microscope, transmission electron microscopy (TEM), X-ray diffractometer (XRD), and scanning electron microscopy (SEM). Tensile tests reveal that the ultimate tensile strength of 299 MPa and elongation of 15.7% were demonstrated in the cold-rolled alloy; the ultimate tensile strength of 211 MPa and elongation of 26.5% were demonstrated in the annealed alloy. Hardness tests indicate that the microhardness of α-Mg phase reaches HV 85. TEM examination reveals that high-density dislocations, dislocation pile-up, dislocation tangle, and interaction between dislocations and particles result in dislocation strengthening and second phase strengthening in the cold-rolled alloy. TEM and XRD results show that α-Mg, β-Li, AlLi, MgLi2Al, and Al2Y phases exist in the cold-rolled alloy while α-Mg, β-Li, MgLi2Al, and Al2Y phases exist in the annealed alloy. SEM observation shows that the fracture mode in the cold-rolled state is a ductile and brittle mixed fracture, and the fracture mode in the annealed state is a ductile fracture. The elongations in both cases are consistent with the fracture morphologies. Strengthening mechanisms were analyzed via crystal defect strengthening models. A strengthening sequence was proposed in this alloy as follows: dislocation strengthening > solid solution strengthening > grain boundary strengthening > lattice friction strengthening > second phase strengthening.

To control the superplastic flow and fracture and examine the variation in deformation energy, the stress and grain size of Mg–7.28Li–2.19Al–0.091Y alloy were obtained using tensile testing and microstructure quantification, and new high temperature deformation energy models were established. Results show that the grain interior deformation energy increases with increasing the strain rate and decreases with increasing the temperature. The variation in the grain boundary deformation energy is opposite to that in the grain interior deformation energy. At a given temperature, critical cavity nucleation energy decreases with increasing strain rate and cavity nucleation becomes easy, whereas at a given strain rate, critical cavity nucleation energy increases with increasing temperature and cavity nucleation becomes difficult. The newly established models of the critical cavity nucleation radius and energy provide a way for predicting the initiation of microcrack and improving the service life of the forming parts.

The microstructures, mechanical properties, deformation mechanism and cavitation growth of Mg-10.2Li-2.1Al-2.23Zn-0.2Sr alloy subjected to multidirectional forging and rolling (MDFR) were studied to examine the deformability of the Mg-Li alloy. X-ray diffraction (XRD) results confirm the existence of α (Mg) and β (Li) phases and Mg17Al12, Al4Sr and LiMgAl2 intermetallic compounds. Studies of the microstructures reveal that a thin banded-grained microstructure with a grain size less than 3.75 µm is obtained via MDFR and annealing at 523 K for 1 h. There were significant grain refinements. The maximum elongation to failure was 712.1%, and this was obtained in the current alloy at 623 K with a strain rate of 1.67 × 10−3 s−1. The strain rate sensitivity exponent and the activation energy for deformation were estimated to be 0.884 and 91.9 kJ/mol, respectively. This indicates that the rate-controlling deformation mechanism under the aforementioned condition is grain boundary sliding controlled by lattice diffusion. Experimental cavity observations show the existence of cavity interlinkage or stringers. A new plasticity-controlled cavity growth rate equation considering cavity interlinkage was established, and a cavity growth diagram was constructed. The diagram prediction is consistent with the experimental results. In addition, fractographs show that the intergranular fracture is a ductile fracture mechanism. At room temperature, the ultimate tensile strength of 242 MPa and the elongation of 23.59% were obtained in the present alloy.

The continuous casting-extrusion (CTE) process is a short-route technology for fabricating aluminum and aluminum alloy wires. A novel Al-1.44Mg-1.09Y alloy was prepared by CTE, and its mechanical properties and microstructure evolution were investigated at elevated temperatures to explore the hot tensile ductility of aluminum alloy wire. A true strain to failure of 1.159 was obtained at 773 K and 1.67×10−2 s−1, and the present alloy exhibits high strain rate quasi-superplasticity. Microstructure observations reveal that it is difficult to realize the equiaxedness of elongated or textured grains through hot tensile deformation. A new deformation mechanism map (DMM) was constructed which predicts that dislocation climb at high stress dominates the high-temperature deformation process. This theoretical prediction using the DMM is in good agreement with experimental transmission-electron-microscopy results and with the estimated true stress exponent of 5 and the activation energy for deformation in the range 127.378―141.536 kJ mol−1. A new three-dimensional histogram containing a dynamic recovery (DRV) or dynamic recrystallization factor was constructed to demonstrate that the DRV mechanism dominates the deformation. Most experimental results are consistent with prediction using this histogram.

Based on Fractional Fourier Transform (FrFT), a targets number detection method is proposed for conventional narrow-band radar in this paper. Firstly, the fractional Fourier transform angle is estimated based on the minimum entropy criterion. And then, the narrow-band echo data are transformed to frequency domain via FrFT from the estimated angle. Finally, the sorties are identified by peak detection of the transform results. The simulation results verify the effectiveness of the proposed method.

A novel Mg-2.76Li–3Al-2.6Zn-0.39Y alloy was prepared by multidirectional forging (MDF) and rolling (R) to improve strength and ductility, and its microstructural evolution and mechanical properties were investigated by an optical microscope, X-ray diffraction (XRD), transmission electron microscope (TEM), and tensile tester. After MDFR, the ultimate tensile strength was 275 ± 8 MPa, the yield strength was 207 ± 7 MPa, and the elongation was 29% at a grain size of 6.8 ± 1.1 μm. The specific modulus of this alloy was 30.04 MN m kg−1, and the specific strength was 183.58 kN m kg−1. Microstructural examination of decreased-temperature MDF revealed the presence of a bimodal microstructure, which is favorable for the enhancement of both strength and ductility. The deformation mechanisms of MDF are intense mechanically shearing fragmentation and incomplete dynamic recrystallization. XRD analysis revealed that the present alloy consists of α(Mg) phase, and Al2Y, Mg17(Al,Zn)12, Mg2Y, and AlLi intermetallic compounds. TEM analysis confirmed the existence of Mg17(Al,Zn)12 compound and dislocation wall and pile-up. Portevin–Le Chatelier (PLC) effect or serrated flow was discovered in this alloy. The relationship between the break-away stress and the experimental stress was proposed as a criterion for judging the occurrence of the PLC effect. The estimated stress is consistent with the experimental stress. The contributions of different strengthening mechanisms to tensile yield strength were estimated. The estimated tensile yield strength is in good agreement with the experimental tensile yield strength.

Background and Aim The efficacy of telbivudine for breaking vertical transmission of hepatitis B virus has been well established. Data on the risk of postpartum flare after telbivudine withdrawal and efficacy of extended antiviral therapy after delivery are limited. Methods Chronic hepatitis B virus-infected women who received telbivudine beginning at week 24 or 28 of gestation were enrolled and then followed up to 52 weeks postpartum. Virological and biochemical parameters were assessed. Results Of the 241 women who finished 52 weeks of follow-up, 33.6% had elevated serum alanine aminotransferase (ALT) during pregnancy. Telbivudine administration resulted in ALT normalization in 85.2% before delivery. Compared with women having a normal ALT level throughout pregnancy, those with elevated ALT had a significantly higher rate of ALT flare after telbivudine withdrawal (25.0% vs 11.9%; χ2 = 4.273, P = 0.039). Multivariate analysis indicated that only ALT elevation during pregnancy correlated with postpartum flare after telbivudine withdrawal. Those women with elevated ALT during pregnancy continued antiviral treatment to 52 weeks postpartum and had a significantly higher HBeAg seroconversion rate (P = 0.001) and a notable decrease in HBsAg titers (P = 0.001). Conclusion It is safe for the majority of women to withdraw telbivudine after delivery, whereas exciting serological response encourages extended antiviral therapy for mother with ALT elevation during pregnancy.

Eight examples of potassium N-arylbenzimidates, [K2{OCPhN(2-R1,6-R2,4-R3C6H2)}2]n (R1 = R2 = R3 = H K1; R1 = R2 = H, R3 = Me K2; R1 = R2 = H, R3 = OMe K3; R1 = R2 = H, R3 = F K4; R1 = R2 = H, R3 = Cl K5; R1 = R2 = H, R3 = NO2 K6; R1 = R3 = H, R2 = Me K7; R1 = R2 = Me, R3 = H K8), have been prepared and characterized by spectroscopic and analytical techniques. In addition, the molecular structures of K6(3THF) and K7 were determined and shown to consist of two-dimensional coordination polymers involving combinations of π-aryl and NO2-/N-donor interactions. In the presence of benzyl alcohol (BnOH), K1 - K8 all showed high efficiency for the ROP of e-caprolactone (e-CL) and L-lactide (L-LA), affording linear polyesters (PCL and PLA) with BnO or CH3O end-groups (the latter derived from the quenching solvent). By contrast, lower conversions were achievable when the runs were performed in the absence of BnOH. Mechanistic studies have indicated that for runs performed with BnOH, monomer activation by benzyl alkoxide and N-arylbenzimidate were competitive pathways for the ROP of both cyclic esters. Furthermore, the nature of the N-aryl substituents influenced the ROP of e-CL and L-LA in distinct ways. For example, K1 and K6 showed lower conversions of e-CL than that observed for K2 - K5, K7 and K8, while the conversions of L-LA using K1 - K3 and K6 exceeded that shown by K4, K5, K7 and K8. In addition, the type of solvent greatly affected their catalytic efficiency with hexane and toluene proving superior to THF and CH2Cl2 in the ROP of e-CL. Conversely, for L-LA almost quantitative conversions were observed in THF, CH2Cl2 and toluene while hexane was less effective. Furthermore, kinetic studies of the ROP of L-LA performed at different run temperatures highlighted the beneficial effect of higher temperature.

Mother-to-child transmission (MTCT) is a major obstacle in the elimination of hepatitis B virus (HBV) infection. Telbivudine (LdT) and tenofovir disoproxil fumarate (TDF) are the two most common antiviral medicines for preventing MTCT. However, the efficacy and safety of LdT and TDF in preventing HBV vertical transmission during the second to third trimester have not been compared rigorously. Therefore, we carried out a prospective multicentre cohort study of chronic hepatitis B in mothers with HBV DNA > 106 IU/mL, receiving LdT or TDF during the second to third trimester. Among the 893 mothers enrolled, 857 (LdT/TDF/untreated group (NTx) = 396/325/136) completed consecutive follow-up with 854 infants (LdT/TDF/NTx = 395/323/136). LdT and TDF treatment resulted in a similar decrease of HBV DNA in mothers at delivery. Multivariate analysis indicated that only HBsAg titre at the baseline correlated with viral DNA decrease (P = 0.015). With intention-to-treat analysis, MTCT rates in the LdT, TDF and NTx group were 4.41%, 2.42% and 22.08%, respectively. An increasing vertical transmission rate was found to be closely associated with higher HBsAg titre, 5.32% and 17.65% infection rate was estimated in infants born to mothers with HBsAg > 4 and >5 log10 IU/mL, respectively. No serious side effects were reported in either mothers or infants. LdT and TDF treatments were well tolerated and showed comparable efficacy in reducing MTCT. Higher risk of MTCT was shown in pregnant women with HBsAg > 4 log10 IU/mL.

Deformation mechanism map (DMM) is a useful tool to depict pictorially the deformation mechanisms and to elucidate the nature of material flow in creep and superplasticity. In this paper, the number of dislocations and the dislocation density inside the grain and at the grain boundary were incorporated into Mohamed's and Kawasaki–Langdon's DMMs in an attempt to give their distribution. It is found that in superplasticity or Region II regime, whether or not the dislocations exist inside the grain depends on the Burgers vector compensated grain size and the shear modulus compensated stress. In the DMMs, the number of dislocations at the grain boundary is about one fifth as much as that inside the grain. The dislocation forecasts in Coble creep and dislocation creep regimes are consistent with the thoughts of Coble and Weertman mechanisms. A new DMM containing the dislocation density was proposed with Zn–22 wt% Al eutectoid alloy as the subject and its prediction is in good agreement with some of available experimental evidences.

The ultimate tensile strength of 209 MPa and the elongation to failure of 24% were demonstrated in as-rolled Mg–9.3Li–1.79Al–1.61Zn (designated as LAZ922) alloy sheets. Variation in true stress with true strain showed that stress decreases and elongation to failure increases under high density pulsed current. The stresses at the current density of 1.44×103 and 2.11×103 A/mm2 decreased by 57% and 82%, respectively, relative to the stress without a current. The elongations to failure at above current density were 33.2% and 78%. These were somewhat larger than the elongation to failure of 24% without a current. The imposed current promoted the appearance of some equiaxed grains within the elongated grains in the gauge section and induced partial dynamic recrystallization. The formation of needle grains near the fracture site at the current density of 2.11×103 A/mm2 can be attributed to the occurrence of new grain boundaries caused by the lattice expansion due to an increase in temperature. Dislocation studies revealed that, as the current density increases, the structure evolution such as the formation of tangled dislocations, the formation of dislocation walls at the subgrain boundary, and the disappearance of dislocations within the subgrain takes place. New models of dislocation density and number of dislocations inside the grain in the presence of current were established. The changing trend of the model prediction was consistent with experimental results.

When recovering a shredded document that has numerous mixed pieces, the difficulty of the recovery process can be reduced by clustering, which is a method of grouping pieces that originally belonged to the same page. Restoring homologous shredded documents (pieces from different pages of the same file) is a frequent problem, and because these pieces have nearly indistinguishable visual characteristics, grouping them is extremely difficult. Clustering research has important practical significance for document recovery because homologous pieces are ubiquitous. Because of the wide usage of Chinese and the huge demand for Chinese shredded document recovery, our research focuses on Chinese homologous pieces. In this paper, we propose a method of completely clustering Chinese homologous pieces in which the distribution features of the characters in the pieces and the document layout are used to correlate adjacent pieces and cluster them in different areas of a document. The experimental results show that the proposed method has a good clustering effect on real pieces. For the dataset containing 10 page documents (a total of 462 pieces), its average accuracy is 97.19%.

BACKGROUND AND GOALS A series of changes in the immune system occur during pregnancy and puerperium. Currently, we aim to characterize both the natural changes in liver inflammation and its association with hepatitis B viremia during this special period. PATIENTS AND METHODS Chronic hepatitis B (CHB) gravidas were recruited and followed up to 52 weeks postpartum. Virological and biochemical parameters were assessed throughout the period. RESULTS A total of 1097 CHB mothers had finished the entire follow-up including 451 accepting telbivudine, 178 accepting tenofovir, and 468 without antiviral therapy. Among the mothers, 11.94% went through hepatic flare in the first trimester and the rate decreased to 2.1% at the time of delivery. Nevertheless, a much higher frequency (19.78%) was observed in the early postpartum. Interestingly, alanine aminotransferase level decreased along with the development of pregnancy and then suddenly increased in the first month of puerperium. In addition, a downward trend was observed on the titer of HBsAg and HBeAg after delivery. Of note, an obvious higher frequency of alanine aminotransferase flare was revealed in mothers with high viremia (>6 log10 IU/mL). With multivariate analysis, only hepatitis B virus titer at baseline was strongly associated with hepatic flare during early postpartum (95% confidence interval, 1.012-3.049, P=0.045). The predictive rates of hepatic flare at baseline viral load of 6, 7, and 8 log10 IU/mL were 16.67%, 28.30%, and 30.60%, respectively. CONCLUSIONS CHB gravidas with high viremia should be monitored closely during entire pregnancy, and extended antiviral therapy is recommend to those mothers with baseline viremia >7 log10 IU/mL.

To determine the extrusion force of pipe fabricated by continuous casting and extrusion (CASTEX) using an expansion combination die, the metallic expansion combination die was divided into diversion zone, expansion zone, flow dividing zone, welding chamber, and sizing zone, and the corresponding stress formulae in various zones were established using the slab method. The deformation zones of CASTEX groove were divided into liquid and semisolid zone, solid primary gripping zone, and solid gripping zone, and the formulae of pipe extrusion forces were established. Experiments were carried out on the self-designed CASTEX machine to obtain the aluminum pipe and measure its extrusion force using the expansion combination die. The experimental results of radial extrusion force for aluminum pipe are in good agreement with the calculated ones.

Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester. Based on the deformation behavior and microstructural evolution of superalloy GH4742, different types of instability criteria of Prasad, Gegel, Malas, Murty and Semiatin were compared, and the physical significance of parameters was analyzed. Meanwhile, the processing maps with different instability criteria were obtained. It was shown that instability did not occur when average power dissipation rate was larger than 50% in the temperature range of 1020–1130 °C, corresponding to the strain rate range of 5 × 10−4–3.2 × 10−3 s−1. The domain is appropriate for the processing deformation of superalloy GH4742.

The deformation zone of CONFORM extrusion was divided into primary gripping zone, gripping zone, conical expansion chamber zone, cylindrical zone and sizing zone of die, and corresponding force equilibrium equations were established using the Slab method. The deformation force formulae of CONFORM machine at any wrapping angle with an expansion chamber were obtained. Experiment on pure aluminum and Al–5%Ti–1%B alloy was conducted on the CONFORM machine self-designed. The resistance to deformation of Al–5%Ti–1%B alloy at the deformation temperature of 400 °C and the strain rate of 3.07 s−1 was measured to be 50 MPa using Gleeble–1500 thermal simulation machine. The calculation results of deformation forces for CONFORM process with an expansion chamber for pure aluminum and Al–5%Ti–1%B alloy were given. The experimental CONFORM radial force is in agreement with the radial force obtained by theoretical formula.

Hot compression tests were conducted on a Gleeble-1500D thermal simulating tester. Based on the deformation behavior and microstructural evolution of superalloy GH79, different types of instability criteria of PRASAD, GEGEL, MALAS, MURTY and SEMIATIN were compared, and the physical significance of parameters was analyzed. Meanwhile, the processing maps with different instability criteria were obtained. It is shown that instability did not occur when average power dissipation rate was larger than 60% in the temperature range of 900–930 °C and 960–1080 °C, corresponding to the strain rate range of 5×10 −4 −1.8×10 −1 s −1 and 5×10 −4 −1.5×10 −1 s −1 , respectively. The two domains are appropriate for the processing deformation of superalloy GH79.

A semisolid slurry of AZ31 magnesium alloy was prepared by vibrating wavelike sloping plate process, and the semisolid die forging process, microstructures, and properties of the magnesium alloy mobile telephone shell were investigated. The semisolid forging process was performed on a YA32-315 four-column universal hydraulic press. The microstructures were observed by optical microscopy, the hardness was analyzed with a model 450SVD Vickers hardometer, the mechanical properties was measured with a CMT5105 tensile test machine, and the fractograph of elongated specimens was observed by scanning electron microscopy (SEM). The results reveal that with the increase of die forging force, the microstructures of the product become fine and dense. A lower preheating temperature and a longer dwell time are favorable to the formation of fine and dense microstructures. The optimum process conditions of preparing mobile telephone shells with excellent surface quality and microstructures are a die forging force of 2000 kN, a die preheating temperature of 250°C, and a dwell time of 240 s. After solution treatment at 430°C and aging at 220°C for 8 h, the Vickers hardness is 61.7 and the ultimate tensile strength of the product is 193 MPa. Tensile fractographs show the mixing mechanisms of quasi-cleavage fracture and ductile fracture.

The seroprevalence of hepatitis B virus (HBV) and its impact on pregnancy outcomes of women from Shaanxi Province (China) was assessed. Risk factors for mother-to-child transmission (MTCT) were evaluated based on HBV-related seroprevalence data. Viral markers and biochemical parameters were assessed in HBsAg-positive mothers and their infants out of 13,451 cases recruited. A pretested and structured questionnaire was used to test the general HBV knowledge. Descriptive statistics and logistic regression analysis were done to reveal possible risk factors for MTCT. The overall prevalence of HBsAg in pregnant women was 7.07% (951/13,451), and a rate as high as 9.40% was observed. Among the HBsAg-positive pregnant women, 30.49% (290/951) were HBeAg-positive, 22.08% (210/951) had HBV DNA levels >106 IU/mL and only 16.19% with a high risk of MTCT (34/210) had received antiviral treatment. The overall MTCT rate was 5.21%. Noteworthy, the risk ratio and 95% confidence interval (95% CI) of MTCT in HBeAg-negative mothers with HBV DNA levels >2 × 103 IU/mL and HBsAg >104 IU/mL was 26.062 (2.633–258.024), which was significantly higher than that of HBeAg-positive mothers with HBV DNA level >106 IU/mL. Moreover, the awareness and knowledge about HBV transmission, risk factors, and intervention for MTCT were generally lacking among HBsAg-positive mothers. As a higher HBsAg seroprevalence and a higher MTCT rate among HBeAg-negative mothers with lower HBV DNA level was observed, our study emphasizes different interventional criteria for HBeAg-positive and HBeAg-negative mothers. Extensive health education, routine screening, and immunization against HBV during pregnancy are highly warranted to minimize the possibility of perinatal transmission.

An electrostrictive uniaxial ultrasonic levitation reaction system was designed to perform TiC synthesis reaction by suspending graphite powder in Al-3Ti melt and an Al-3Ti-0.15C grain refiner alloy was obtained. The results show that sound pressure node in which graphite suspends is formed in the melt between radiation block and reflecting board by ultrasonic and TiAl3 particles congregate around C powder Meanwhile, due to ultrasonic cavitation, dissolved TiAl3 provides better surface condition for the synthesis reaction of TiC. The reaction route is that C and dissolved Ti react to form TiC. Ultrasonic cavitation has a thermal activation effect on TiC particles and Al-3Ti-0.15C refiner has excellent microstructural refining effect on α-Al.

The efficacy of telbivudine for breaking vertical transmission of hepatitis B virus has been well established. Data on the risk of postpartum flare after telbivudine withdrawal and efficacy of extended antiviral therapy after delivery are limited.Chronic hepatitis B virus-infected women who received telbivudine beginning at week 24 or 28 of gestation were enrolled and then followed up to 52 weeks postpartum. Virological and biochemical parameters were assessed.Of the 241 women who finished 52 weeks of follow-up, 33.6% had elevated serum alanine aminotransferase (ALT) during pregnancy. Telbivudine administration resulted in ALT normalization in 85.2% before delivery. Compared with women having a normal ALT level throughout pregnancy, those with elevated ALT had a significantly higher rate of ALT flare after telbivudine withdrawal (25.0% vs 11.9%; χIt is safe for the majority of women to withdraw telbivudine after delivery, whereas exciting serological response encourages extended antiviral therapy for mother with ALT elevation during pregnancy.

Background In China, women with chronic HBV infection and who are of childbearing age receive lamivudine at an early age. Thus, viral resistance becomes a challenge for intervention to prevent mother-to-infant transmission. We prospectively assessed the efficacy of tenofovir in pregnant women with lamivudine-resistant HBV. Methods Chronic HBV-infected mothers resistant to lamivudine were enrolled. Tenofovir was administrated at gestation weeks 24 or 28. Virological and biochemical parameters were assessed. All infants received combined immunoprophylaxis and were followed for 1 year. Results Of the 48 mothers enrolled, 21 started tenofovir therapy at gestation week 24 and 27 started at week 28. Tenofovir resulted in an HBV DNA decline of 5.23 ±1.68 log10 IU/ml at delivery. The group starting therapy at week 24 exhibited a more rapid viral inhibition ( P6 IU/ml, 76.2% from the week 24 starting group displayed virus 4 IU/ml, and 52.4% showed undetectable virus at delivery, much higher than the week 28 starting group (29.6%), although there was no statistically significant difference in viral levels at delivery between the two groups. Congenital abnormalities and neonatal growth were comparable to the normal population. No case of perinatal transmission was diagnosed. Conclusions This investigation clarifies the efficacy of tenofovir for reducing vertical transmission of HBV in mothers with lamivudine-resistant HBV and demonstrates that tenofovir is well-tolerated in the second and third trimesters.

By dividing the CASTEX process of Al-clad steel wire (AS wire) into two stages: the CASTEX stage and the bonding stage, this paper analyzes and studies the CASTEX force of the process at any wrapping angle and develops the analytical equations of this technology, which can be referred to in further studies and practical applications.

Wearable and sensitive photodetectors (PDs) have been demonstrated based on a blend film of PbS quantum dots (QDs) and QDs modified multiwalled carbon nanotubes (MWCNTs). Owing to the synergetic effect from high light sensitivity of PbS QDs and excellent conductive and mechanical properties of MWCNTs, the blend PDs show high sensitivity and flexibility performance: device responsivity and detectivity reach 583 mA/W and 3.25 × 1012 Jones, respectively, and could stand large number (at least 10 000 cycles) and wide angle (up to 80°) bending. Furthermore, the wearable and sensitive PDs have been applied to measure the heart rate in both red and near infrared (NIR) ranges. The presented PDs are expected to work as sensor candidates in integrated electronic skin.