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The effect of pre-stretching and under-aging treatment on microstructure and fatigue crack resistance of Al-4.1Cu-1.27Mg-0.47Mn-0.02Ti alloy has been investigated in present work. The results showed that the fatigue strength corresponding to 107 stress cycle numbers of the sample pre-stretched 4% and under-aged at for 2 hours reached up to 280MPa, 80MPa higher than that pre-stretched 0% and peak-aged at for 8 hours. Microstructural observations showed that fine and uniformly dispersed S’ plates were present in the sample treated by pre-stretching and under-aging, whereas, a coarse S’ plate was formed in the sample when treated by 0% pre-stretching and peak-aging. It is indicated that the pre-stretching and under-aging treatment promotes the dispersoid formation of strengthening particles, enhancing the fatigue crack resistance and resultant fatigue strength. Keywords: Al-Cu-Mg alloy, fatigue, pre-stretching, aluminum alloy casing pipe

Background Aloe polysaccharide (AP) is a type of an active macromolecule of Aloe vera, which contributes to its function. However, whether AP possesses anti-osteoporosis properties is unknown. Methods Adipose-derived stromal cells were treated with different concentrations of AP. Early and late osteogenesis were, respectively, evaluated by ALP and Alizarin Red S staining. The effect of AP on the processes of adipogenesis inhibition in ADSCs was analyzed by oil red O staining. Western blot was used to assess the expression of osteogenic and adipogenic related factors. Then, Noggin was administered to further confirm the mechanism by which AP promotes the osteogenesis of ADSCs. Finally, 40 female SD rats were classified into a bilateral laparotomy group (Sham group) and three bilateral ovariectomy groups: OVX group, OVX + AP group, and OVX + AP + Noggin group. The bilateral rat femurs were collected to perform micro-CT scanning, HE, Masson trichrome, and Oil red O staining. Results The results indicated that AP could increase ALP expression and calcium deposition. Through molecular mechanisms, AP promotes the protein expression of COL1A1, OPN, and ALP in ADSCs, but downregulates the expression of PPARγ. Also, AP directs ADSCs’ fate by stimulating the BMP2/Smads signaling pathway. In vivo, the rat AP-treated had more trabecular bone than the OVX rat, indicating partial protection from cancellous bone loss after treatment with AP. Conclusion Our results show that AP may promote osteogenesis of ADSCs through BMP-2/Smads signaling pathway and inhibits lipogenic differentiation. Thus, AP might be a promising alternative medicine to treat postmenopausal osteoporosis.

BACKGROUND Sedation with propofol injections is associated with a risk of addiction, but remimazolam benzenesulfonate is a comparable anesthetic with a short elimination half-life and independence from cell P450 enzyme metabolism. Compared to remimazolam, remimazolam benzenesulfonate has a faster effect, is more quickly metabolized, produces inactive metabolites and has weak drug interactions. Thus, remimazolam benzenesulfonate has good effectiveness and safety for diagnostic and operational sedation. AIM To investigate the clinical value of remimazolam benzenesulfonate in cardiac surgery patients under general anesthesia. METHODS A total of 80 patients who underwent surgery in the Department of Cardiothoracic Surgery from August 2020 to April 2021 were included in the study. Using a random number table, patients were divided into two anesthesia induction groups of 40 patients each: remimazolam (0.3 mg/kg remimazolam benzenesulfonate) and propofol (1.5 mg/kg propofol). Hemodynamic parameters, inflammatory stress response indices, respiratory function indices, perioperative indices and adverse reactions in the two groups were monitored over time for comparison. RESULTS At pre-anesthesia induction, the remimazolam and propofol groups did not differ regarding heart rate, mean arterial pressure, cardiac index or volume per wave index. After endotracheal intubation and when the sternum was cut off, mean arterial pressure and volume per wave index were significantly higher in the remimazolam group than in the propofol group (P < 0.05). After endotracheal intubation, the oxygenation index and the respiratory index did not differ between the groups. After endotracheal intubation and when the sternum was cut off, the oxygenation index values were significantly higher in the remimazolam group than in the propofol group (P < 0.05). Serum interleukin-6 and tumor necrosis factor-α levels 12 h after surgery were significantly higher than before surgery in both groups (P < 0.05). The observation indices were re-examined 2 h after surgery, and the epinephrine, cortisol and blood glucose levels were significantly higher in the remimazolam group than in the propofol group (P < 0.05). The recovery and extubation times were significantly lower in the remimazolam group than in the propofol group (P < 0.05); there were significantly fewer adverse reactions in the remimazolam group (10.00%) than in the propofol group (30.00%; P < 0.05). CONCLUSION Compared with propofol, remimazolam benzenesulfonate benefited cardiac surgery patients under general anesthesia by reducing hemodynamic fluctuations. Remimazolam benzenesulfonate influenced the surgical stress response and respiratory function, thereby reducing anesthesia-related adverse reactions.

The widespread use of therapeutic glucocorticoids has increased the incidences of glucocorticoid-induced osteoporosis (GIOP). Oxidative stress and mitochondrial dysfunction are major causes of GIOP; therefore, alleviation of excess oxidative stress in osteoblasts is a potential therapeutic strategy for osteoporosis. Exosomes derived from ADSCs (ADSCs-Exos), as novel cell-free therapeutics, can modulate various biological processes, such as immunomodulation, reduce oxidative damage, and promote tissue repair as well as regeneration. In this study, ADSCs-Exos restored the viability and osteogenic potential of MC3T3-E1 cells by attenuating apoptosis, oxidative damage, intracellular ROS generation, and mitochondrial dysfunction. Moreover, after pretreatment with ADSCs-Exos, Nrf2 expressions were upregulated in Dex-stimulated osteoblasts. Inhibitory assays showed that silencing Nrf2 partially eliminated the protective effects of ADSCs-Exos. The rat model assays confirmed that ADSCs-Exos alleviated the Dex-induced increase in oxidation levels, restored bone mass of the distal femur, and increased the expressions of Nrf2 and osteogenic markers in bone tissues. Thus, ADSCs-Exos alleviated apoptosis and oxidative stress by regulating Nrf2/HO-1 expressions after Dex and prevented the development of GIOP in vivo.

With the explosive growth of multimedia data on the Internet,single-modal retrieval has been unable to meet the needs of users,and cross-modal retrieval has emerged.Cross-modal retrieval aims to retrieve related data of one modality with data of another modality.Its core task is to extract data features and measure data correlation between different modality.This paper summarizes the recent research progress in the field of cross-modal retrieval,and summarizes the research results in the field of cross-modal retrieval from the perspectives of traditional methods,deep learning methods,manual feature hash coding methods and deep learning hash coding methods.On this basis,the performance of various algorithms in cross-modal retrieval of commonly used standard data sets is compared and analyzed.Finally,the problems of cross-modal retrieval research are analyzed and the future development trend of the field is prospected.

A fractional viscoelastic-viscoplastic model is developed for time-dependent materials, by considering the reference stress in the fractional viscoelastic body. Using this model, the creep, stress relaxation and strain rate behavior is numerically analyzed for frozen soil and zeonex results, with the consideration of continuous order functions that conform to the order interval limits. Subsequently, a variable-order viscoelastic-viscoplastic creep model and also a variable-order viscoelastic-viscoplastic strain rate model are established by the developed variable-order viscoplastic and fractional viscoelastic models, respectively. Finally, the rheological behavior of frozen soil and Zeonex is simulated using the variable-order viscoelastic-viscoplastic creep model and variable-order viscoelastic-viscoplastic strain rate model, and the model parameters are analyzed. The results show that the proposed order function equation is continuous and conforms to the interval effect of the definition. The variable-order viscoelastic-viscoplastic rheological model takes into account the elastic-visco-plastic behavior of the material in the rheological process, and has high accuracy.

Hydrogen peroxide (H2O2) is an important product generated in the body and related to many pathophysiological processes and glucose metabolism disorder can cause many fatal diseases in living bodies. Therefore, the sensing of H2O2 and glucose is of great significance in disease diagnostics and treatment. Fluorescent carbon dots (CDs) are one new class of nanoprobes for H2O2 and glucose. Nevertheless, the CD-based sensor is always based on its fluorescence response, which is influenced by the auto-fluorescent interference. Herein, efficient fluorescent CDs were synthesized by one-pot solvothermal method, and the CDs exhibit bright and persistent deep-red (DR) chemiluminescence (CL) in bis(2,4,6-trichlorophenyl) oxalate and H2O2 solution with a CL quantum yield of (8.22 ± 0.30) × 10−3, which is amongst the highest values in ever reported nanomaterials for chemical analysis. Employing the CDs as CL nanoprobes, sensitive sensing for H2O2 has been achieved with a detection limit of 11.7 μM, and further for glucose detection with a detection limit of 12.6 μM. The DR CL CDs is promising to be applied in blood glucose analysis or in vivo biosensor.

Nitrated phenols are a group of nitrogen-containing organics ubiquitously present in ambient air, which are also important components of atmospheric light-absorbing organic matter (brown carbon) that have significant impacts on climate change, air quality, and human health. In this study, we collected a total of 265 daily filter samples of fine particles (PM

This study was performed to uncover the effects of dexmedetomidine on oxidative stress injury induced by mitochondrial localization of telomerase reverse transcriptase (TERT) in enteric glial cells (EGCs) following intestinal ischaemia-reperfusion injury (IRI) in rat models. Following establishment of intestinal IRI models by superior mesenteric artery occlusion in Wistar rats, the expression and distribution patterns of TERT were detected. The IRI rats were subsequently treated with low or high doses of dexmedetomidine, followed by detection of ROS, MDA and GSH levels. Calcein cobalt and rhodamine 123 staining were also carried out to detect mitochondrial permeability transition pore (MPTP) and the mitochondrial membrane potential (MMP), respectively. Moreover, oxidative injury of mtDNA was determined, in addition to analyses of EGC viability and apoptosis. Intestinal tissues and mitochondria of EGCs were badly damaged in the intestinal IRI group. In addition, there was a reduction in mitochondrial localization of TERT, oxidative stress, whilst apoptosis of EGCs was increased and proliferation was decreased. On the other hand, administration of dexmedetomidine was associated with promotion of mitochondrial localization of TERT, whilst oxidative stress, MPTP and mtDNA in EGCs, and EGC apoptosis were all inhibited, and the MMP and EGC viability were both increased. A positive correlation was observed between different doses of dexmedetomidine and protective effects. Collectively, our findings highlighted the antioxidative effects of dexmedetomidine on EGCs following intestinal IRI, as dexmedetomidine alleviated mitochondrial damage by enhancing the mitochondrial localization of TERT.

Oxidative stress is an important contributor to the development of osteoporosis. Melatonin, an indoleamine secreted by the pineal gland, has antioxidant properties. This study aims to explore whether melatonin can promote bone formation and elucidate the mechanisms underlying this process. In this study, we used an

Background Intestinal ischemia/reperfusion (I/R) injury commonly occurs during perioperative periods, resulting in high morbidity and mortality on a global scale. Dexmedetomidine (Dex) is a selective α2-agonist that is frequently applied during perioperative periods for its analgesia effect; however, its ability to provide protection against intestinal I/R injury and underlying molecular mechanisms remain unclear. Methods To fill this gap, the protection of Dex against I/R injury was examined in a rat model of intestinal I/R injury and in an inflammation cell model, which was induced by tumor necrosis factor-alpha (TNF-α) plus interferon-gamma (IFN-γ) stimulation. Results Our data demonstrated that Dex had protective effects against intestinal I/R injury in rats. Dex was also found to promote mitophagy and inhibit apoptosis of enteric glial cells (EGCs) in the inflammation cell model. PINK1 downregulated p53 expression by promoting the phosphorylation of HDAC3. Further studies revealed that Dex provided protection against experimentally induced intestinal I/R injury in rats, while enhancing mitophagy, and suppressing apoptosis of EGCs through SIRT3-mediated PINK1/HDAC3/p53 pathway in the inflammation cell model. Conclusion Hence, these findings provide evidence supporting the protective effect of Dex against intestinal I/R injury and its underlying mechanism involving the SIRT3/PINK1/HDAC3/p53 axis.

Background Propofol is an intravenous anesthetic agent that commonly induces significant neuroapoptosis. MicroRNAs (miRNAs) have been reported to participate in the regulation of propofol exposure-mediated neurotoxicity. MiR-215, as one of miRNAs, was found to regulate nerve cell survival. However, the mechanism through which miRNAs regulate propofol exposure-mediated neurotoxicity is still unclear. Methods Real-time PCR was used to detect miR-215 expression level. Cell viability was measured using MTT assay. Cell apoptosis was examined via flow cytometry analysis. ROS, MDA, LDH and SOD levels were assayed through ELISA kits. Dual luciferase reporter assay identified the interaction between miR-215 and large tumor suppressor 2 (LATS2). Protein level was detected using western blot analysis. Results MiR-215 expression was downregulated in propofol-treated rat hippocampal neurons. MiR-215 mimics promoted cell viability and reduced apoptosis in propofol-treated neonatal rat hippocampal neuron. MiR-215 mimics also caused inhibition of oxidative stress as evidenced by suppression of ROS, MDA and LDH levels as well as increase of SOD level. In addition, we found that large tumor suppressor 2 (LATS2) is a target of miR-215 and miR-215 mimics decreased LATS2 level in propofol-treated neonatal rat hippocampal neuron. Further, LATS2 overexpression suppressed the effect of miR-215 on propofol-induced apoptosis and oxidative stress in neonatal rat hippocampal neuron. Conclusion Taken together, we demonstrate that miR-215 attenuates propofol-induced apoptosis and oxidative stress in neonatal rat hippocampal neuron by targeting LATS2, suggesting that miR-215 may provide a new candidate for the treatment of propofol exposure-induced neurotoxicity.

Objective: To study the correlation of Doppler ultrasound parameters with angiogenesis and cancer cell growth in endometrial cancer. Methods: Patients with endometrial cancer and fibroids who accepted surgical resection in the Central Hospital of Enshi Autonomous Prefecture between March 2015 and June 2017 were selected as the research subjects and enrolled in the observation group and control group of the study respectively. The preoperative pelvic Doppler ultrasonography was done to determine the blood flow parameters resistance index (RI) and pulsatility index (PI) of the endometrial lesions; after surgical resection, the endometrial cancer lesion tissue was collected from the observation group and normal endometrial tissue was collected from the control group to determine the contents of proproliferation molecules, pro-invasion molecules and angiogenesis molecules. Results: PI and RI levels in endometrial cancer lesion of observation group were significantly lower than those of control group, and cIAP1, cIAP2, RLIP76, p-Pak4ser474, EFEMP2, CXCR4, CXCR7, Snail, Septin-9, β-arrestin2 and SOX2 protein levels in endometrial cancer lesion were significantly higher than those of control group; PI and RI levels in endometrial cancer lesion were negatively correlated with cIAP1, cIAP2, RLIP76, p-Pak4ser474, EFEMP2, CXCR4, CXCR7, Snail, Septin-9, β-arrestin2 and SOX2 protein levels. Conclusion: The Doppler ultrasound parameters of endometrial carcinoma lesion are closely related to the angiogenesis and cancer cell growth in the lesion.

Objective: To measure the contrast-enhanced ultrasound parameters of endometrial benign and malignant lesions and investigate their correlation with malignant molecule expression. Methods: A total of 118 patients who were examined and diagnosed with endometrial benign hyperplasia in the hospital between December 2012 and January 2017 were collected as endometrial hyperplasia group, and 67 patients with endometrial carcinoma were collected as endometrial cancer group. The differences in the levels of uterine contrast-enhanced ultrasound parameters as well as the expression of proliferation, apoptosis and invasion genes in endometrial lesion tissue were compared between the two groups. Pearson test was used to evaluate the correlation between uterine contrast-enhanced ultrasound parameters and malignant molecule expression in the lesions. Results: Contrast-enhanced ultrasound parameter TTP level of endometrial cancer group was lower than that of endometrial hyperplasia group whereas PI level was higher than that of endometrial hyperplasia group. Proliferation gene EFEMP2 mRNA expression in lesion tissue of endometrial cancer group was lower than that of endometrial hyperplasia group whereas RRM2 and DJ-1 mRNA expression were higher than those of endometrial hyperplasia group; apoptosis genes P53, c-myc and Livin mRNA expression were higher than those of endometrial hyperplasia group whereas Caspase-3 and Bid mRNA expression were lower than those of endometrial hyperplasia group; invasion gene DKK1 mRNA expression was lower than that of endometrial hyperplasia group whereas HMGB1, EZH2 and Snail mRNA expression were higher than those of endometrial hyperplasia group. Pearson test showed that the contrast-enhanced ultrasound parameter levels of endometrial cancer were directly correlated with the malignant molecule expression in the lesion tissues. Conclusion: contrast-enhanced ultrasound parameter levels can be used to identify endometrial benign and malignant lesions and are directly correlated with the severity of the lesion.

Background: Intestinal ischemia-reperfusion injury (IRI) is a devastating complication in the perioperative period leading to systemic inflammation and multiple organ dysfunction. We aimed to determine whether dexmedetomidine protects against oxidative stress injury induced by mitochondrial translocation of telomerase reverse transcriptase (TERT) in enteric glial cells (EGCs) of a rat model after intestinal IRI and the mechanisms involved in this protection. Methods: After the rat model with intestinal IRI was established, the rats were treated with high/low dose of dexmedetomidine. The positive rate of TERT protein was detected by immunohistochemistry. The distribution and levels of TERT were measured by immunofluorescence. The levels of apoptosis-related proteins and oxidative stress injury-related factors (ROS, MDA, and GSH) were also measured. Mitochondrial membrane permeability and potential were detected using Calcein cobalt and Rhodamine 123 staining respectively. The oxidative injury of mtDNA was detected by real-time fluorescence quantitative PCR. Cell Counting Kit-8 (CCK-8) assay and flow cytometry were applied to detection of EGC viability and apoptosis. Results: Relative to normal rats, rats with intestinal IRI displayed with reduced TERT mitochondrial translocation and EGC viability, as well as elevated mitochondrial damage, oxidative stress, and EGC apoptosis. Dexmedetomidine treatment could alleviate intestinal IRI by promoting mitochondrial translocation of TERT, reducing mitochondrial damage and oxidative stress. The regulatory mechanism functioned in a dose-dependent manner. Conclusion: Dexmedetomidine restores mitochondrial translocation of TERT, thus reducing oxidative stress and mitochondrial damage in EGCs after intestinal IRI. Funding: The study was supported by a grant from the National Natural Science Foundation of China (No. 81660096). Declaration of Interest: The authors have no competing interests to declare. Ethical Approval: Our study was approved by the Institutional Review Board of the First Affiliated Hospital of Nanchang University. All animal experiments and procedures were performed in accordance with the Guide for the Care and Use of Laboratory Animals published by the National Institutes of Health.

We aimed to evaluate the efficiency and safety of one-step procedure combined endoscopic retrograde cholangiopancreatography (ERCP) and laparoscopic cholecystectomy (LC) for treatment of patients with cholecysto-choledocholithiasis. A prospective randomized study was performed on 63 consecutive cholecysto-choledocholithiasis patients during 2008 and 2011. The efficiency and safety of one-step procedure was assessed by comparing the two-step LC with ERCP + endoscopic sphincterotomy (EST). Outcomes including intraoperative features, postoperative features (length of stay and postoperative complications) were evaluated. One- or two-step procedure of LC with ERCP + EST was successfully performed in all patients, and common bile duct stones were completely removed. Statistical analyses showed that length of stay and pulmonary infection rate were significantly lower in the test group compared with that in the control group (P < 0.05), whereas no statistical difference in other outcomes was found between the two groups (all P > 0.05). The one-step procedure of LC with ERCP + ESTis superior to the two-step procedure for treatment of patients with cholecysto-choledocholithiasis regarding to the reduced hospital stay and inhibited occurrence of pulmonary infections. Compared with two-step procedure, one-step procedure of LC with ERCP + EST may be a superior option for cholecysto-choledocholithiasis patients treatment regarding to hospital stay and pulmonary infections.

In the present paper, the non-intrusive Probabilistic Collocation (NIRPC) method is introduced in detail and used to simulate the effects of tip clearance uncertainty on the aerodynamic performance of NASA Rotor 37, which is combined with a commercial CFD software. The tip clearance height is supposed to be a stochastic variable in Beta distribution with four schemes of uncertainty in the random height of the plain tip clearance, the leading edge, the trailing edge and both the leading and trailing edges, respectively. The statistical properties of total performance of the rotor and flow structure within the blade passage in different flow conditions are analyzed. The results show that the Std. of total performances caused by the uncertain plain tip clearance decreases with reducing of the outlet pressure. The maximum of the standard deviation of Mach number appears in the regions where the leakage flow, the shock wave and the separation flow locate, which decreases from the tip to the hub. When the tip clearance is linear distributed, the uncertainty of tip clearance height at the leading edge is the main factor under high mass flow conditions. With the mass flow reaches to choking point, the Std. of total performances caused by the uncertainty of tip clearance height at the trailing edge drops sharply.

Mechanical properties and microstructural evolution of an Al-Cu-Mg-Ag alloy during thermal exposure at elevated temperature were characterized by means of tensile tests, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation. The tensile test results suggested that tensile strength (σBbB) and yield strength (σBsB) reduced with both increasing exposure time and temperature. When exposed at 150°C, the Al-Cu-Mg-Ag alloy exhibits good structural stability due to the splendid thermal stability of the Ω phase. SEM results showed that the specimen was fractured in a combined manner of intergranular and transgranular fracture. TEM results suggested the reduction of mechanical properties of samples was attributed to the coarsening of Ω phase and the precipitation of θ phase during thermal exposure.

The software CFDesign was used for the analysis of flow field simulation of two different kinds of drilling bit. The results showed that, if the waterway design of drilling bit was unreasonable, it could result in the following phenomenon: the local position of drilling bit could get severe erode of drilling fluid; the return of flow and eddy currents could be observed in the bottom of drilling well; negative pressure could be detected and might result in cavitation corrosion; the direction vector of flow field were diffused and resulted in cross flow. The waterway structure of arc-bottom bit was more reasonable comparing that of flat-bottom bit.

Using the Wilson equation and an extended Miedema model, the thermodynamic effect of silver on the stability of reinforced particles in the Al and Al-Cu matrix were evaluated. The formation of Al3Ti, AlB2, and TiB2 phases are promoted with the addition of silver atoms in Al matrix. Minimum values of excess free energy of reinforced particles were found in the Al-Cu-Ti-B-Ag system. Evidently, Low content of silver atoms actually has the profound effect in promoting the reinforced particles in Al-Cu matrix.

The effect of aging condition on elevated temperature tensile strength and microstructure of an Al-Cu-Mg-Ag alloy was investigated. The tensile strength of 165°C/14h samples was greater at room temperature and 200°C, while the 165°C/2h samples got superior tensile properties at 250°C and 300°C. The microstructure contained mainly of Ω plates in both conditions, and as the increasing of exposure temperature, the coarsening of Ω precipitates occurred by the solution of small particles and the growth of large particles, resulting in an increase in the average particle size, and the decrease in the number of precipitates.

Effect of thermal exposure on FCG of Al-Cu-Mg alloys with low Cu/Mg ratio in artificial and natural ageing conditions were modeled and analyzed. Three FCG rate models, namely Collipriest, Priddle, and Modified Forman model were examined to research the effect of thermal exposure on FCG of Al-Cu-Mg alloys with low Cu/Mg ratio in artificial and natural ageing conditions. The results showed that Priddle model provided the best fit. Priddle model was used to fit FCG data of (a) 170°C/30min ageing; (b)170°C/30min ageing +100°C/2000h exposure; (c)T351 ageing+100°C/2000h exposure; (d)T351 ageing. The fitted results indicated that the FCP resistance can be increased by slight artificial aging, and artificial aging can delay the degradation of the fatigue properties

Mechanical properties and microstructural evolution of an Al-Cu-Mg-Ag alloy during thermal exposure at elevated temperature were characterized by means of tensile tests, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation. The tensile test results suggested that tensile strength (σb) and yield strength (σs) reduced with both increasing exposure time and temperature. When exposed at 150°C, the Al-4.87Cu-1.2Mg-1.0Ag alloy exhibits good structural stability due to the excellent thermal stability of the Ω phase. SEM results showed that the specimen was fractured in a combined manner of intergranular and transgranular fracture. TEM results suggested the reduction of mechanical properties of samples was attributed to the coarsening of Ω phase and the precipitation of S' phase during thermal exposure.

The effects of two-step aging temperature on exfoliation corrosion of an Al-Zn-Mg-Cu alloy were characterized by EXCO test, electrochemical test and TEM observations. Results suggested that the partial recrystallized structure is susceptible to exfoliation corrosion which is greatly influenced by intergranular corrosion. The transfer current of the sample aged at 170°C (second-step aging temperature) is higher than that of the sample aged at 155°C. The second-step aging temperature exhibits more contributation to the exfoliation corrosion in this investigation, compared to the first-step aging temperature.

Microstructural evolution and flow behaviour during hot compression of twin roll cast ZK60 magnesium alloy were characterised by employing deformation temperatures of 300, 350 and 400°C and strain rate ranging from 10−3 to 100 s−1. When compressed at 10−3 s−1, all stress–strain curves at different temperatures (300, 350 and 400°C) showed a flow softening behaviour due to active dynamic recrystallisation. When compressed at 10−2 s−1 and elevated temperatures (300, 350 and 400°C), all stress–strain curves showed a flow stress drop after peak stress due to twinning for 300 and 350°C deformation and recrystallisation for 400°C deformation. The balance between shear deformation and recrystallisation resulted in a steady flow behaviour after the true strain reached 0·22. When strain rate increased to 10−1 s−1, a small fraction of dynamic recrystallisation in shear deformation region was responsible for slight flow softening behaviour during compression. A flow hardening appeared due to basal and non-bas...

This work aims to develop a physically based numerical model to predict the microstructure evolution and residual yield strength of high Cu/Mg ratio Al-Cu-Mg-Ag alloys after thermal exposure. Based on the established interfacial energy model and the classical nucleation and growth theories, a thermodynamically based precipitation model had been established to describe competitive precipitation of two phases, being of different stability, in under-aged and the subsequent thermally exposed Al-Cu-Mg-Ag alloys. And the strengthening model based on Orowan mechanism was deduced to predict the residual yield strength after thermal exposure. The microstructural evolution and yield strength predictions of the model in this work are generally in good agreement with the experimental result.

A Thermecmastor-Z hot deformation simulator, optical microscopy, XRD and TEM were employed to characterize the flow stress behavior and microstructure of twin roll cast ZK60 magnesium alloy during initial stage of hot compression at elevated temperature of 300 °C and 400 °C and a given strain rate of 10−2 s−1. The results suggest that flow stress drop during initial stage of hot compression at 300°C, generally led by dynamic recrystallization, is attributed to twinning, correspondingly to dynamic recrystallization as deformation temperature is raised to 400 °C.

Mechanical properties and microstructural evolution of an Al-Cu-Mg-Ag alloy during thermal exposure at elevated temperature were characterized by means of tensile tests, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation. The tensile test results suggested that tensile strength (σBbB) and yield strength (σBsB) reduced with both increasing exposure time and temperature. When exposed at 150°C, the Al-Cu-Mg-Ag alloy exhibits good structural stability due to the splendid thermal stability of the Ω phase. SEM results showed that the specimen was fractured in a combined manner of intergranular and transgranular fracture. TEM results suggested the reduction of mechanical properties of samples was attributed to the coarsening of Ω phase and the precipitation of θ phase during thermal exposure.

The effect of severe plastic deformation method on the dissolution of θ’phase in Al-Cu binary alloy was investigated by employing equal channel angular pressing(ECAP) and multi-axial compression(MAC). The results suggested that a more rapid dissolution of θ’ phase occurred in the MAC processed sample comparing with the ECAP processed sample, which was attributed to the stress state difference between ECAP and MAC processed samples .

The alloying behavior of RE element of Er in Al-Cu-Mg-Ag alloys with addition of Er were investigated in this paper. During solidification ,most of element Er segregated at grain boundaries in the form of primary Al8Cu4Er phase and part of Er dissolved in the α-Al matrix. After rolling, Al8Cu4Er phase could be fragmentated into dispersed particle which leaded to an increase of the grain boundary strengthening . TEM observation and tensile strength test showed that small addition of Er retarded the precipitation of Ω phase and prolonged the time corresponding to the peak aging,with a remarkable increase of ductility.

The evolution of second phases and its effect on tensile mechanical property in artificial ageing and RRA process of super-high strength aluminum alloy is investigated.The result of tensile test shows that the samples of Al-Zn-Mg-Cu-Ag alloy aged at lower temperature(100°C) not only have higher tensile strength up to 753Mpa but also relatively higher tensile elongation above 9% than normal temperature(120°C) in artificial ageing. The sample of Al-Zn-Mg-Cu alloy has the highest tension strength upto 788Mpa when aged at 100°C for 48 hours in single step of artificial ageing. Further more in RRA process samples of Al-Zn-Mg-Cu alloy preaged at 100°C for 24 hours retrogressed at 200°C for 7min and reaged at 100°Cfor 24 hours present the best tensile strength of 795Mpa than others. The tensile strength of Al-Zn-Mg-Cu alloy after RRA treated decreases with prolonging of retrogression time and reageing time starting from 7mins and 24 houres respectively. SEM observation shows that crack of the samples in tensile test is created at large particles in the fracture while there are more particles of undissolved phase in Al-Zn-Mg-Cu alloy containing Ag. TEM observation shows that the dominant strengthening particle corresponding to the peak strength of Al-Zn-Mg-Cu alloy containing Ag when aged at 120°C for 8 hours is η’ phase while dominant strengthening particle is G.P zone when aged at 100°C for 80 hours. However, η’ phase as the dominant strengthening particles corresponds to the peak strength of Al-Zn-Mg-Cu alloy without content of Ag when aged at 100°C for 48hours. TEM observation also shows that G.P zone as strengthening particle is dominant in the samples of Al-Zn-Mg-Cu alloy reaged at 100°C for 24 hours, and strengthening particles is coarsened when the sample is retrogressed at 200°C and reaged for a longer time. It is suggested that whether at the presence of coarse particles of undissolved phases or when G.P zone and η’ particle grow up in the retrogression ,sample needs deformable G.P zone instead of undeformable η’ in subsequent artificial ageing and reageing as dominant strengthening particle, in order to present a larger freedom spacing for dislocation to slip and let the sample not to behave too brittle to display high resistance to imposed plastic deformation or high tensile strength.

The effects of heat treatment on the microstructure and mechanical properties of two alloys, namely Al-12.2% Zn-2.48% Cu-2.0% Mg-0.15% Zr-0.166% Ag (alloy 1), and Al-9.99% Zn-1.72% Cu-2.5% Mg-0.13% Zr (alloy 2) were investigated. The results show that low temperature aging after promotive solution treatment can increase elongation without the loss of strength for the studied alloys. The optimum aging treatment (T6) for alloy 1 and alloy 2 is 100 °C/80 h and 100 °C/48 h, respectively. Compared with other heat treatment alloys, alloy 1 and alloy 2 show super-high tensile strength up to 753 MPa and 788 MPa, remaining 9.3% and 9.7% elongation under T6 condition, respectively. During aging, trace addition of Ag enhances the formations of GP zone and metastable phase, and stabilizes GP zone and metastable phase to a higher temperature. Trace addition of Ag prolongs the aging time of reaching the peak strength and delays over-aging condition of the alloy. However, trace addition of Ag promotes the formation of coarse constituent in the alloy and consumes hardening alloying elements of Zn and Mg. Morecover, the addition of the transition element Zr in 7000 series super-high alloy forms incoherent Al3Zr dispersoid which can serve as nucleation sites for nonuniform precipitation of η phase during aging process. The higher the aging temperature, the greater the tendency for nonuniform precipitation of η phase.

(Pb 0.95 Sr 0.05 )[(Mn 1/3 Sb 2/3 ) x (Ni 1/2 W 1/2 ) y (Zr 1/2 Ti 1/2 ) z ]O 3 piezoelectric ceramics (abbreviated as PNW–PMS–PZT) with 1 mol% excess PbO, 0.25 wt% CeO 2 and 0.2 wt% MnO 2 were synthesized by traditional ceramics process. The effect of Pb(Mn 1/3 Sb 2/3 )O 3 (abbreviated as PMS) and Pb(Ni 1/2 W 1/2 )O 3 (abbreviated as PNW) on phase structure, dielectric and piezoelectric properties was investigated in detail. The content of perovskite phase of all ceramics specimens is 100%, the phase structure of PNW–PMS–PZT ceramics changed from tetragonal phase to single rhombohedral phase with the amount of PMS and PNW increased. Take into consideration dielectric constant, ɛ r , dielectric loss tan δ , electromechanical coupling factor k p , mechanical quality factor Q m , Curie temperature T c and sintering temperature, it was concluded that the ceramics with composition of x = 0.06, y = 0.02, z = 0.92 can be used for high-power piezoelectric transformer. These properties include ɛ r = 2138, tan δ = 0.0058, k p = 0.613, Q m = 1275, d 33 = 380 pC/N, T c = 205 °C.

0.85Pb(Zn1/3Nb2/3)O3-0.10BaTiO3-0.05PbTiO3 (abbreviated as PZN-based ceramics hereafter) ternary system ceramics with Zn2+ deficiency were synthesized by the columbite method. The effect of deficient Zn2+ on phase structure, ordered micro-region size and dielectric properties was investigated in detail. The analysis of Raman scattering spectra demonstrated that Zn2+ deficiency sharply enlarged the ordered micro-region size. Zn2+ deficiency significantly increased the dielectric constant, and decreased the diffusion degree of phase transition. There is a close correlation between effective ordered micro-regions size and dielectric properties for the PZN-based ceramics.

The terahertz wave transmission through ensembles of sub-wavelength size metallic particles is studied by THz-TDS and finite different time domain (FDTD). The result of the experiment shows that with the increase of the thickness of the sample, the terahertz pulses experience significant attenuation, delay and broadening. In addition, an obvious red-shift and narrowing of the amplitude spectrum are observed. Numerical simulations based on FDTD are performed to explain the details of the data and lead to an excellent agreement with the experimental results. Furthermore, the relation between the size of the particles and the transmission properties of terahertz radiation is analyzed.

Purpose Previous studies have reported an association between chronic exposure to elevated levels of drinking water arsenic and cardiovascular and other health effects. There is debate, however, whether human health effects exist at lower exposure levels. Prior studies have been unable to investigate these potential health effects due to imprecise exposure estimation. Examining a sensitive subpopulation such as pregnant women proves more efficient in detecting potential health effects associated with drinking water arsenic. Methods A population-based cohort study was conducted based on the prenatal care visits of 5306 women in Inner Mongolia, China, from 1997 to 1999. Repeated measures mixed models were used to assess associations between drinking water arsenic estimates and serial blood pressure measurements taken during prenatal care visits. Results Once selected confounders were controlled for, exposure to drinking water arsenic was positively associated with mean arterial blood pressure, even at lower ranges of exposure. Arsenic exposure categories of 51 to 100 μg/L and more than 100 μg/L were associated with increases in mean arterial pressure of 3.56 (95% CI = 1.66, 5.47) and 2.30 (0.57, 4.02) mmHg, respectively, relative to the mean arterial pressure of women exposed to drinking water arsenic concentrations ranging from below detectable levels to 20 μg/L. These changes were not consistent over the course of gestation and became somewhat less pronounced later in pregnancy. Conclusion Mean arterial pressure during pregnancy is associated with exposure to drinking water arsenic among otherwise healthy pregnant women, suggesting a potential vascular effect of drinking water arsenic at lower doses than had been previously reported.