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The most advantageous property of magnesium (Mg) alloys is their density, which is lower compared with traditional metallic materials. Mg alloys, considered the lightest metallic structural material among others, have great potential for applications as secondary load components in the transportation and aerospace industries. The fatigue evaluation of Mg alloys under elastic stress amplitudes is very important in ensuring their service safety and reliability. Given their hexagonal close packed structure, the fatigue crack initiation of Mg and its alloys is closely related to the deformation mechanisms of twinning and basal slips. However, for Mg alloys with shrinkage porosities and inclusions, fatigue cracks will preferentially initiate at these defects, remarkably reducing the fatigue lifetime. In this paper, some fundamental aspects about the fatigue crack initiation mechanisms of Mg alloys are reviewed, including the 3 followings: 1) Fatigue crack initiation of as-cast Mg alloys, 2) influence of microstructure on fatigue crack initiation of wrought Mg alloys, and 3) the effect of heat treatment on fatigue initiation mechanisms. Moreover, some unresolved issues and future target on the fatigue crack initiation mechanism of Mg alloys are also described. [ABSTRACT FROM AUTHOR]

Through comparing the microstructure and mechanical properties of Mg-6%Li and Mg-6%Li-6%Zn-1.2%Y alloys, the difference in their mechanical anisotropy have been deeply investigated. Due to the formation of I-phase (Mg3Zn6Y, icosohedral structure), the volume fraction of β-Li phases formed in Mg-6%Li-6%Zn-1.2%Y alloy was two times higher than that in Mg-6%Li alloy even these two alloys having the same Li content. Texture analysis demonstrated that I-phase particle stimulated nucleation of recrystallization (PSN) and the formation of higher volume fraction of β-Li phases can remarkably weaken the basal texture of α-Mg phases, resulting in a very weak mechanical anisotropy. On the contrary, the basal texture of the a-Mg phases in Mg-6%Li alloy was quite strong and obvious mechanical anisotropy between differently oriented samples can be observed. [ABSTRACT FROM AUTHOR]

Through investigating and comparing the fatigue behavior of an as-cast Mg-7%Gd-5%Y-1%Nd-0.5%Zr alloy in both laboratory air and 3.5 wt.% NaCl solution, the effect of corrosion attack on fatigue crack initiation has been disclosed. The S-N curves showed that the fatigue strength in air was 120 MPa and not sensitive to the loading frequency, whereas the fatigue strength in NaCl solution decreased from 80 MPa to 60 MPa with the loading frequency decreasing from 20 Hz to 5 Hz. Observations to fracture surfaces demonstrated that in air, fatigue cracks preferentially initiated at the oxide inclusions. However, the fatigue crack initiation in NaCl solution was associated with corrosion pits. Moreover, multiple fatigue cracks initiated at pits on fracture surfaces of corrosion fatigue failed samples when the loading frequency decreased to 5 Hz. Based on the measured "defect area" of oxide inclusions, the predicted fatigue strength in air could be well fitted with the experimental data. However, due to the occurrence of hydrogen embrittlement and crack initiation at multiple sites, the fatigue strength of samples tested in NaCl solution cannot be predicted. [ABSTRACT FROM AUTHOR]

By investigating the corrosion behavior of two oriented surfaces for an as-extruded Mg-3% Al-1% Zn alloy bar, we demonstrate that the surface with a high concentration of {1 0 -1 0} and {1 1 -2 0} oriented prism planes is more electrochemically stable and corrosion resistant than the surface with a high concentration of {0 0 0 2}, {1 0 -1 0} and {1 1 -2 0} oriented planes. Further analysis confirms that the corrosion performance is mainly determined by the galvanic corrosion between grains and between twinned and untwinned areas due to their different crystallographic orientations. [ABSTRACT FROM AUTHOR]

This paper presents a newly developed flexible sheet forming approach with better sheet thickness distribution and reduced processing time comparing to the conventional incremental sheet forming. In the approach, a two-step forming process has been proposed: multi-point forming as preforming is employed to achieve an initial shape and designed thickness distribution; After the preforming, incremental sheet forming process is then applied to finalize part geometry with desired thickness distribution. In the work, a numerical model for predicting the thickness distribution of the final part is developed by integrating finite element simulation and analytical prediction of ISF process. To achieve the uniformity of final thickness distribution, the preformed shape is optimized based on the developed thickness prediction model. Additionally, a real industrial case problem of forming an aerospace cowling is used to validate the proposed hybrid flexible sheet forming approach. Satisfactory results are obtained, which demonstrates the feasibility and effectiveness of the developed forming process. [ABSTRACT FROM AUTHOR]

The effect of two specific solution heat treatment procedures on the corrosion and stress corrosion cracking (SCC) susceptibility of an as-rolled Al-Zn-Mg-Cu alloy was investigated. It is shown that for a stepped solution treatment with a final temperature of 495°C, the SCC resistance of subsequently retrogressed and re-aged (RRA) samples is remarkably improved compared with that of samples solution-treated at a stationary temperature of 475°C. Since the investigated alloy is probably only partially homogenized or cooled with a very slow industrial cooling rate after homogenization, the mechanistic aspects of this are related to the dissolution of Al2CuMg and the Cu content in the grain boundary precipitates after the RRA treatment. [ABSTRACT FROM AUTHOR]

Single point incremental forming (SPIF) is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. In the SPIF process, a ball nose tool moves along a predefined tool path to form the sheet to desired shapes. Due to its unique ability in local deformation of sheet metal, the friction condition between the tool and sheet plays a significant role in material deformation. The effects of friction on surface finish, forming load, material deformation and formability are studied using a newly developed oblique roller ball (ORB) tool. Four grades of aluminum sheet including AA1100, AA2024, AA5052 and AA6111 are employed in the experiments. The material deformation under both the ORB tool and conventional rigid tool are studied by drilling a small hole in the sheet. The experimental results suggest that by reducing the friction resistance using the ORB tool, better surface quality, reduced forming load, smaller through-the-thickness-shear and higher formability can be achieved. To obtain a better understanding of the frictional effect, an analytical model is developed based on the analysis of the stress state in the SPIF deformation zone. Using the developed model, an explicit relationship between the stress state and forming parameters is established. The experimental observations are in good agreement with the developed model. The model can also be used to explain two contrary effects of friction and corresponding through-the-thickness-shear: increase of friction would potentially enhance the forming stability and suppress the necking; however, increase of friction would also increase the stress triaxiality and decrease the formability. The final role of the friction effect depends on the significance of each effect in SPIF process. [ABSTRACT FROM AUTHOR]

Objective: To investigate the safety and feasibility of laparoscopic remedial surgery in patients who didn't reach the cure criterion of early colorectal cancer after endoscopic resection. Methods: The clinical and follow-up data of 12 patients who didn't reach the cure criterion of early colorectal cancer and then underwent endoscopic resection was collected. The clinicalpathological features and remedial indications were analyzed to evaluate the effects of laparoscopic remedial surgery. Results: The average number of lymph nodes in the lymph node dissection was 15 during remedial surgery, and 3 of them had lymph node metastasis. Among the 3 patients with residual cancer, two cases were poorly differentiated, 1 case was moderately differentiated, 1 case was positive for basal margin, and 1 case had vascular invasion. No lymph node metastasis occurred in the 9 patients who had no residual cancer. Among these, 8 cases were moderately differentiated, 1 case was poorly differentiated and 2 cases had positive basal margin. The average follow-up duration was 40 months and all 12 patients were in a state of survival at the last follow-up. During the follow-up of the 3 patients with residual cancer, 1 patient received adjuvant chemotherapy with unknown prognosis; 1 patient received postoperative adjuvant radiochemotherapy, and lung metastasis occurred; 1 patient did not receive any treatment after surgery and survived for 33 months. Conclusions: Laparoscopic remedial surgery is a safe and feasible remedy for patients who didn't reach the cure criterion of early colorectal cancer after endoscopic resection. However, the choice of remedial strategy for colorectal carcinoma needs further investigation for patients with no vascular invasion, high degree of differentiation, and negative basal margin.

Objective: To study the effects of metastasis associated 1 (MTA1) on biological characteristics such as migration, invasion and proliferation of gastric cancer (GC) cells. Methods: pSilencer3.1-MTA1-siRNA vector was used to establish human gastric cancer BGC-823 cell lines with constitutive MTA1-knockdown. Boyden, wound healing, clony forming assay and 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H tetrazolium bromide (MTT) assay were performed to identify the effects of MTA1-deficiency on the biological behaviors of BGC-823 cells in vitro. Simultaneously, MTA1 overexpressed BGC-823 cell line was established by pcDNA3-MTA1 plasmid transfection for reverse verification. In addition, the role of MTA1 in the tumorigenicity of gastric cancer BGC823 cells in vivo was examined by subcutaneous injection of BGC-823 cells expressing different MTA1 levels into nude mice. Reverse transcription-polymerase chain reaction (RT-PCR) and western blot were used to detect the expression levels of integrin β1, cyclin D1 and uPAR in pSilencer3.1-MTA1-siRNA, pcDNA3-MTA1 transfected cells and control cells. Results: MTA1 knocked down or upregulated BGC-823 cell lines were successfully generated by transfecting pSilencer3.1-MTA1-siRNA or pcDNA3-MTA1 vector with lipofectamine 2000, respectively. The Boyden and wound healing experiments showed metastasis and invasion ability in MTA1 knocked down cells (25±2, 12±1) were significantly decreased when compared with those of control (78±2, 50±2) and MTA1-overexpressed groups (218±2, 269±3; P <0.05). The results of MTT assay and colony forming assay were significantly decreased when compared with those of showed that MTA1 overexpressed cells grew more rapidly and formed more colonies in vitro and induced worse malignant tumors in vivo, while MTA1 knocked down cells presented the reversed phenotype[control group (1 482.41±511.90) mm(3,) (1.39±0.29)g; MTA1 overexpressed group [(3 158.73±1 823.22) mm(3,) (2.23±0.51)g; MTA1-downregulated group (711.32±284.30)mm(3,) (0.87±0.21) g ; P <0.05)]. In addition, RT-PCR result showed that the expression level of MTA1 was positively correlated with the known metastasis-related genes (integrinβ1, cyclinD1, uPAR). Conclusions: MTA1 promotes the invasion, migration and proliferation of human gastric cancer BGC-823 cells. On the contrary, down-regulation of MTA1 significantly inhibits tumorigenicity of BGC-823 cells and induces favorable phenotypes. MTA1 may promote the malignant phenotype of BGC-23 cells via regulating the expressions of integrinβ1, cyclinD1 and uPAR.

Aim: Serum tumour markers carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA19-9) and CA242 were investigated to evaluate the values of single and combined test in the diagnosis and prognosis of pancreatic cancer., Methods: Pre-operative serum CEA, CA19-9 and CA242 were measured in 105 pancreatic cancers, 70 non-pancreatic malignancies and 30 benign pancreatic diseases., Results: The sensitivity of CA19-9 alone was the highest in pancreatic cancer patients (80%), but the specificity was significantly lower than that of CEA and CA242 (P<0.01). The combination of CEA and CA242 could increase the specificity to 92%. In serum CA242 positive patients, the survival time was remarkably shorter than that of patients with negative result (P<0.01). The survival time in patients with more than two markers positive expression of CEA, CA19-9 and CA242 was obviously shorter than that of only one or no marker positive expression (P<0.05)., Conclusion: The diagnostic rate of CA19-9 in pancreatic cancer is better than that of CEA and CA242. Combined detection of CEA and CA242 can improve the diagnostic specificity obviously. High levels of serum markers are associated with advanced stage of the disease. Patients with two or three markers positive expression of CEA, CA19-9, and CA242 simultaneously had a shorter survival time.

A sensitive and simplified high performance liquid chromatographic procedure has been developed for quantification of lomefloxacin in human plasma. The recovery of lomefloxacin was 95 to 102%. The relative standard deviation was 2.1 to 7.8%. The calibration curve was linear in the range from 0.125 micrograms/ml to 5.012 micrograms/ml with r = 0.9998. The detection limit of the method is 25 ng/ml. The plasma drug concentration-time course after medication conformed to a 1-compartment open model with a first order absorption. Mean t1/2 value was 5.5 h.

Ofloxacin is a new broad-spectrum oral bactericidal antimicrobial agent. Its primary effect is the inhibition of bacterial DNA gyrase. This paper describes the development of a simple method for its determination using HPLC with UV detection. We used a Waters liquid chromatograph equipped with a Model 490 E multi-wavelength detector, a Model 510 pump and a U6K injector. The separation was performed on a Spherisorb C18 column (200 mm x 4.6 mm ID, 5 microns) with a mobile phase of methanol-0.01 mol/L phosphate buffer-0.5 mol/L tetrabutylammonium bromide (35:65:4, pH 2.50). The flow-rate was 1.0 ml/min and detection was at 294 nm. A specimen (0.2 ml) was spiked with the internal standard (norfloxacin) and deproteinized by adding 1.0 ml methanol. The precipitated mixture was shaken and then centrifuged at 3000 x g for 10 min, the supernatant was evaporated at 75 degrees C under a nitrogen stream. The residue was taken up with 0.4 ml of the mobile phase and 50 microliters aliquots were injected into the system. The minimal detectable concentration in plasma is 20 ng/ml. There is a linear relationship between the peak area ratio over the range of 0.5-4.0 micrograms/ml with r = 0.9999. The method has been applied to assay ofloxacin concentration in human plasma. The pharmacokinetic characteristics were studied.

A sensitive and simplified high-performance liquid chromatographic procedure has been developed for quantification of amiloride in rabbit plasma, as well as human plasma and urine. Following protein precipitation with perchloric acid, the supernatant was directly injected into a C18 Nucleosil column. The mobile phase consisted of methanol-water (45:55) containing 0.1 M perchloric acid, and the compound was quantitated using a fluorescence detector at excitation and emission wavelengths of 286 and 418 nm, respectively. The average recovery was 97.6%. The calibration curve was linear over the range 2.0-20.0 ng/ml. The limit of detection was 0.5 ng/ml.