两种高能束焊TC4合金接头的低周疲劳性能比较

比较30mm厚Ti6Al4V钛合金真空电子束焊接和激光摆动填丝焊接头的低周疲劳性能。测试结果表明,电子束焊接头的低周疲劳性能接近母材,而激光填丝焊接头的低周疲劳性能明显不如电子束焊接头和母材。通过研究两个接头的母材、热影响区和焊缝区的显微硬度,发现电子束焊接头的焊缝区显微硬度与母材的接近,但均低于热影响区的显微硬度,而激光填丝焊接头的焊缝区明显弱化。

Knockdown of Microtubule Associated Serine/threonine Kinase Like Expression Inhibits Gastric Cancer Cell Growth and Induces Apoptosis by Activation of ERK1/2 and Inactivation of NF-κB Signaling

Microtubule-associated serine/threonine kinase(MASTL)functions to regulate chromosome condensation and mitotic progression.Therefore,aberrant MASTL expression is commonly implicated in various human cancers.This study analyzed MASTL expression in gastric cancer vs.adjacent normal tissue for elucidating the association with clinicopathological data from patients.This work was then extended to investigate the effects of MASTL knockdown on tumor cells in vitro.The level of MASTL expression in gastric cancer tissue was assessed from the UALCAN,GEPIA,and Oncomine online databases.Lentivirus carrying MASTL or negative control shRNA was infected into gastric cancer cells.RT-qPCR,Western blotting,cell viability,cell counting,flow cytometric apoptosis and cell cycle,and colony formation assays were performed.MASTL was upregulated in gastric cancer tissue compared to the adjacent normal tissue,and the MASTL expression was associated with advanced tumor stage,Helicobacter pylori infection and histological subtypes.On the other hand,knockdown of MASTL expression significantly reduced tumor cell viability and proliferation,and arrested cell cycle at G2/M stage but promoted tumor cells to undergo apoptosis.At protein level,knockdown of MASTL expression enhanced levels of cleaved PARP1,cleaved caspase-3,Bax and p-ERK1/2 expression,but downregulated expression levels of BCL-2 and p-NF-κB-p65 protein in AGS and MGC-803 cells.MASTL overexpression in gastric cancer tissue may be associated with gastric cancer development and progression,whereas knockdown of MASTL expression reduces tumor cell proliferation and induces apoptosis.Further study will evaluate MASTL as a potential target of gastric cancer therapeutic strategy.

Improving thermal efficiency and stability of laser welding process for magnesium alloy by combining power modulation and subatmospheric pressure environment

The laser welding(LW)process of highly reflective materials presents low thermal efficiency and poor stability.To solve the problem,the effects of subatmospheric environment on LW process,technological parameters in subatmospheric environment on weld formation and welding with sinusoidal modulation of laser power on the stability of LW process in subatmospheric environment were explored.The AZ31magnesium(Mg)alloy was used as the test materials.The test result revealed that the weld penetration in subatmospheric environment can increase by more than ten times compared with that under normal pressure.After the keyhole depth greatly rises,significantly periodic local bulge is observed on the backwall surface of the keyhole and the position of the bulge shifts along the direction of the keyhole depth.Eventually,the hump-shaped surface morphology of the welded seam is formed;moreover,the weld width in local zones in the lower part of the welded seam remarkably grows.During LW in subatmospheric environment,the weld penetration can be further greatly increased through power modulation.Besides,power modulation can inhibit the occurrence of bulges in local zones on the backwall of the keyhole during LW in subatmospheric environment,thus further curbing the significant growth of the weld widths of hump-shaped welding beads and local zones in the lower part of welded seams.Finally,the mechanism of synchronously improving the thermal efficiency and stability of LW process of highly reflective materials through power modulation in subatmospheric environment was illustrated.This was conducted according to theoretical analysis of recoil pressure and observation results of dynamic behaviors of laser induced plasma clouds and keyholes in the molten pool through high speed photography.

Non-crossover sub-Doppler DAVLL in selective reflection scheme

We demonstrate a non-crossover sub-Doppler dichroic atomic vapor laser locking(DAVLL)in selective reflection scheme,which allows us to obtain a modulation-free laser locking with wide tuneable range.The dependence of peak-to-peak amplitude,tuneable range and the slope near the zero-crossing point of error signal on the frequency shift induced by the magnetic fields are studied.The adjustable error signal by the varying external magnetic field can offer the laser locking from the order of tens MHz to hundreds MHz.The ultimate dither of locked laser frequency is less than 0.5 MHz.The square root of Allan variance of the error signals reaches a minimum of 3×10^-10 for an averaging time of 130 s.

White matter disease derived from vascular and demyelinating origins

Damage or microstructural alterations of the white matter can cause dysfunction of the intrinsic neural networks in a condition termed as white matter disease(WMD).Frequently detected on brain computed tomography and magnetic resonance imaging scans,WMD is commonly presented in inflammatory demyelinating diseases like multiple sclerosis(MS)and vascular diseases such as cerebral small vessel disease(CSVD).Prevention of MS and CSVD progression requires early treatments with drastically different medications and approaches,as such,early and accurate diagnosis of WMD,derived from vascular or demyelinating etiologies,is of paramount importance.However,the clinical and imaging similarities between MS,especially during the early stage,and CSVD,pose a significant dilemma in differentiating these two conditions.In this review,we attempt to summarize and contrast the distinguishing features of MS and CSVD for aiding accurate diagnosis to ensure timely corresponding management in the early stages of MS and CSVD.

Improvement in the weldability of molybdenum alloy by pre-welding solid carburising

Molybdenum(Mo), with its high chemical stability and resistance to neutron irradiation, has wide application prospects in the nuclear industry;however, the embrittlement of welded Mo joints limits its further application. In this study, the brittleness of the welded joints of Mo alloy was reduced and their strength was enhanced by adding carbon to the fusion zone(FZ) during laser welding. In the FZ of the Mo joints, carbon mainly existed as Mo_(2)C, and some free C atoms, and MoC and MoOxC yphases were also present. The distribution of Mo_(2)C directly influenced the bonding strength of the grain boundaries.As Mo_(2)C was dispersedly distributed as particles or discontinuous lines at the grain boundaries of Mo,it improved the resistance of the grain boundaries to the propagation of cracks and thereby increasing their strength. However, the Mo_(2)C phases distributed in a reticular pattern at the grain boundaries of Mo provided channels that enabled cracks to rapidly propagate, thereby reducing the resistance of the grain boundaries to crack propagation and weakening their strength. The emergence of the MoOxC yphase reduced the weakening effect of free oxygen atoms on the strength of grain boundaries of Mo.

~elvi-Femoral Complete Bone Bridge in a Patient with Hemophilia

To the Editor： Heterotopic ossification （HO） is a formation of bone outside of the skeletal system. It usually occurs in the following five broad clinical settings： genetic, posttraumatic, neurogenic, postsurgical and as distinctive reactive lesions most often seen in the hands and feet. Although there is an increased tendency to bleed in soft tissue, HO has rarely been reported in hemophilia. At present, a few cases reported the location relationship between ectopic osteogenesis and the pelvis, and only two cases presented pelvi-femoral bone bridge-like progression of this phenomenon. More precisely, it was situated in the posterior area of the hip joint. Here, we describe a rare case of HO bridging from the anterior superior spine to the lesser trochanter of the femur in hemophilia.