Effect of homogenization annealing on internal residual stress distribution and texture in ME21 magnesium alloy extruded plates

The distribution of residual stresses through thickness of 5 mm-thick ME21 magnesium alloy extruded plates was analyzed non-destructively using short-wavelength X-ray diffraction(SWXRD),and the effect of homogenization annealing before extrusion on the residual stress was discussed.The classic d 0 method with an annealed stress-free reference specimen was employed to determine the residual stress of the extruded plates.The residual stress results showed that the gradient of residual stress in the transverse direction was larger than that of the extrusion direction.The homogenization process prior to extrusion weaken the formed sample’s texture.The maximum residual stress of the as-extruded plate was reduced,and the residual stress distribution was homogenized.

Research progress of residual stress determination in magnesium alloys

With the research development of the magnesium alloys,the deformation or stress corrosion induced by residual stress(RS)attracted extensive interests in industry and research efforts extensive.However,there are relatively few studies on the RS of magnesium alloys in the world.The generation cause of RS in magnesium alloys was analyzed at first.Several methods of determinate the RS,including destructive methods(drilling hole,crack compliance,layer exfoliation etc.)and non-destructive methods(X-ray Diffraction,Neutron Diffraction,Short Wavelength X-ray Diffraction)were summarized.The factors that influence the measuring accuracy of XRD method were emphasized.The research trends of RS in magnesium alloys were put forward.

Physiological performance of three calcifying green macroalgae Halimeda species in response to altered seawater temperatures

The effects of seawater temperature on the physiological performance of three Halimeda species were studied for a period of 28 d.Five treatments were established for Halimeda cylindracea,Halimeda opuntia and Halimeda lacunalis,in triplicate aquaria representing a factorial temperature with 24°C,28°C,32°C,34°C and 36°C,respectively.The average Fv/Fm of these species ranged from 0.732 to 0.756 between 24°C and 32°C but declined sharply between 34°C(0.457±0.035)and 36°C(0.122±0.014).Calcification was highest at 28°C,with net calcification rates(Gnet)of(20.082±2.482)mg/(g·d),(12.825±1.623)mg/(g·d)and(6.411±1.029)mg/(g·d)for H.cylindracea,H.opuntia and H.lacunalis,respectively.Between 24°C and 32°C,the specific growth rate(SGR)of H.lacunalis(0.079%–0.110%d–1)was lower than that of H.cylindracea(0.652%–1.644%d–1)and H.opuntia(0.360%–1.527%d–1).Three Halimeda species gradually bleached at 36°C during the study period.Malondialdehyde(MDA)and proline levels in tissues of the three Halimeda were higher in 34–36°C than those in 24–32°C.The results indicate that seawater temperature with range of 24–32°C could benefit the growth and calcification of these Halimeda species,however,extreme temperatures above 34°C have negative impacts.The measured physiological parameters also revealed that H.cylindracea and H.opuntia displayed broader temperature tolerance than H.lacunalis.

Detail description of Lithophyllum okamurae(Lithophylloideae,Corallinales), a widely distributed crustose coralline alga in marine ecosystems

Lithophyllum okamurae is one of the important encrusting coralline algae,which plays important roles as primary producer,carbonate sediment builder,and habitat provider in the marine ecosystems.In this study,L.okamurae was collected from tropical coast of Sanya,and firstly described based on both detailed morph-anatomical characteristics and molecular studies of typic DNA sequences.The structure of the thalli of L.okamurae was pseudoparenchymatous construction with radially organized dimerous organizations in the crustose portion.The pseudoparenchymatous construction were composed of three parts,including 1 to 3 layers of epithelia cells which had flatten to round outermost walls,one layer of square or rectangular cells of the hypothallia and multiple layers of square or elongated rectangular peripheral cells.Palisade cells were observed,and the cells of the contiguous vegetative filaments were connected by secondary pit-connections with cell fusions absent.The carposporangial conceptacles,the spermatangial conceptacles,the bisporangial conceptacles and the tetrasporangial conceptacles were observed,and all these four kinds of conceptacles were uniporate.The spermatangial conceptacles were slightly convex and buried at shallow depths in the thalli tissues,and the carposporangial conceptacles and asexual conceptacles were protruding and conical.Phylogenetic studies based on DNA barcoding markers of 18 S rDNA,COI,rbc L and psb A revealed that L.okamurae clustered with the closest relation of L.atlanticum,and formed a distinct branch.Based on the comparative anatomical features and the molecular data,the detailed description of the valid species of L.okamurae was firstly given in this study to provide theoretical basis for algae resources utilization and conservation in marine ecosystems.

疑似胃神经内分泌肿瘤的胃底腺型胃癌1例

本文报道1例疑似胃神经内分泌肿瘤的胃底腺型胃癌, 回顾分析其临床、内镜、病理特征, 旨在提高胃底腺型胃癌的诊断水平以及减少误诊、漏诊。