H08Mn2SiA冷拔钢丝退火“花丝”成因分析与对策

介绍H0 8Mn2SiA冷拔钢丝退火后形成的“花丝”现象对成品焊丝的危害。分析认为形成“花丝”的原因是半成品在退火时由于炉温过高及炉内富氧造成氧化烧损、酸洗后的钢丝表面粗糙 ,对光的反射与正常表面不一样所致。通过对退火炉温控系统的改进 ,使用含内衬的炉胆 ,并加热风循环装置、加强工艺控制 ,有效避免了“花丝”现象。

关于线切割“花丝”现象的探讨

大多数从事线切割加工和实训教学的教师,在加工较厚工件时都碰上过这种情况。经过一段时间的加工后,钼丝出现一段一段黑斑,出现这种黑斑后钼丝很快就会断掉,而钼丝的使用时间远远没达到正常的寿命。黑斑按一定规率排列形成花纹,故称为"花丝"。

An Antioxidant Acidic Polysaccharide from Cuscuta chinensis

An acidic polysaccharide, H2, was isolated from the alkali-extract CHC of seeds of Cuscuta chinensis Lam. with the molecular weight more than 1.0 x 10(6). Chemical and spectroscopic studies led to the structure determination as follows: the backbone chain consists of 1, 6-linked-beta -D Galp, 1,4-linked-X -D Galp, 1,4-linked-beta -D GalA and 1,2- or 1,4-linked-beta -L Rhap having branching points at position O-3 of some 1,6-linked-beta -D Galp residues (one among eight) and O-4 or O-2 of 1,2- or 1,4-linked-beta -L Rhap residues to terminal beta -D-galactopyranose. The side chains composed of terminal Galp, 1,6-linked-beta -D Galp, 1,4-linked beta -D Galp and 1,3,6-linked-beta -D Galp also linked at position O-3 of 1,6-linked-beta -D Galp residues in the backbone chain. beta -L-arabinofuranosyl and terminal beta -L-rhamnopyranosyl residues existed in the periphery of this polysaccharide linked to O-3 of 1,6-linked-beta -D Galp residues in the backbone chain and the side chains. The polysaccharide H2 increased significantly the survival rate of PC12 cells indicating that it had protective effects against H2O2 insult.

F-Actin Visualization in Generative and Sperm Cells of Living Pollen of Rice Using a GFP-Mouse Talin Fusion Protein

Green fluorescent protein (GFP) fused to the F-actin binding domain of mouse talin labels the actin cytoskeleton in the living generative and sperm cells of a third generation transgenic rice (Oryza sativa L.) plant, A005-G-T-1-2. Observations were made on pollen at four major developmental stages, viz. I. uni-nucleate microspore stage; II. early bi-cellular pollen stage; III. late bi-cellular pollen stage; and IV. tri-cellular pollen stage. At each of these developmental stages vegetative nucleus, generative nucleus/ cell, and sperm cells were seen undergoing continuous and coordinated motion and migration. These movements seemed to be influenced by associated microfilament networks existing in the pollen. Based on these observations we propose that it is the interaction between the microfilament networks (usually one existing in the central cytoplasm and another in the cortex) that controls the dynamic movement of the vegetative nucleus, generative nucleus/cell and sperm cells. Furthermore, we have also observed that there is an array of microfilaments (oriented mostly parallel to the long axis of the cell) existing in the generative and sperm cells. As far as we are aware, this is the first report showing the existence of microfilaments in living generative and sperm cells of rice pollen. The implication and significance of the existence of microfilaments in generative and sperm cells in rendering self-propelled motion of these cells in relation to their passage and movement in the pollen tube and embryo sac for fertilization were discussed.

Actin Visualization in Living Immature Pollen of Rice Using a GFP-Mouse Talin Fusion Protein

Green fluorescent protein (GFP) fused to the F_actin binding domain of mouse talin labels the actin cytoskeleton in the immature pollen of stable transformed rice (Oryza sativa L.) plants. Actin microfilaments could be visualized only in the late_developmental stage of the immature pollen. During this developmental stage, microfilaments, initially composed of very short fibrils, develop into a very complex and novel network that sometimes totally and sometimes partially encloses the vegetative nucleus and the spherical shaped generative cell in the central cytoplasm of the immature pollen. The behavior of the actin microfilamentous structure throughout the late_developmental stage of the immature pollen is extremely dynamic, and the likelihood of this structure in generating forces for vegetative nucleus and generative cell movement in the immature pollen has been discussed. No actin filaments were visualized in the spherical generative cells.

Experimental investigation and multi-objective optimization of wire electrical discharge machining(WEDM) of 5083 aluminum alloy

The experimental analysis presented aims at the selection of the most optimal machining parameter combination for wire electrical discharge machining （WEDM） of 5083 aluminum alloy. Based on the Taguchi experimental design （L9 orthogonal array） method, a series of experiments were performed by considering pulse-on time, pulse-off time, peak current and wire tension as input parameters. The surface roughness and cutting speed were considered responses. Based on the signal-to-noise （S/N） ratio, the influence of the input parameters on the responses was determined. The optimal machining parameters setting for the maximum cutting speed and minimum surface roughness were found using Taguchi methodology. Then, additive model was employed for prediction of all （34） possible machining combinations. Finally, a handy technology table has been reported using Pareto optimality approach.

In situ Localization and Isolation of Actin Filaments from Pollen Tubes of Amaryllis vittata Ait

Actin filaments (AFs) in un-fixed pollen tubes of Amaryllis vittata Ait were visualized after TRITC-phalloidin staining with DMSO as a permeabilising agent. Typically, strands or hundles of microfilaments (Mfs) were distributed in the extreme tip as well as pollen tubes in a form of network.Fluorescent granules or circles of various sizes were frequently found that continued with the filamentous structures. In addition, a more brightly stained structure, possibly Mf organizing center, was observed. Treatment of pollen tubes with cytochalasin D(CD)for increasing time intervals (5-40 minutes) caused gradual reduction of strands until flurescent granules filled up the pollen tubes. Mcanwhile, cytoplasmie streaming was inhibited completely. Though closely associated with vegetative nuclei (VN) and generative cells (GC), AFs were not found in the cytoplasm of GC.Mg++concentration greatly affected the isolated Mfs.

Cloning, Expression and Activity Analysis of a Novel Fibrinolytic Serine Protease from Arenicola cristata

The full-length c DNA of a protease gene from a marine annelid Arenicola cristata was amplified through rapid amplification of c DNA ends technique and sequenced. The size of the c DNA was 936 bp in length, including an open reading frame encoding a polypeptide of 270 amino acid residues. The deduced amino acid sequnce consisted of pro- and mature sequences. The protease belonged to the serine protease family because it contained the highly conserved sequence GDSGGP. This protease was novel as it showed a low amino acid sequence similarity(< 40%) to other serine proteases. The gene encoding the active form of A. cristata serine protease was cloned and expressed in E. coli. Purified recombinant protease in a supernatant could dissolve an artificial fibrin plate with plasminogen-rich fibrin, whereas the plasminogen-free fibrin showed no clear zone caused by hydrolysis. This result suggested that the recombinant protease showed an indirect fibrinolytic activity of dissolving fibrin, and was probably a plasminogen activator. A rat model with venous thrombosis was established to demonstrate that the recombinant protease could also hydrolyze blood clot in vivo. Therefore, this recombinant protease may be used as a thrombolytic agent for thrombosis treatment. To our knowledge, this study is the first of reporting the fibrinolytic serine protease gene in A. cristata.