Hydrogen embrittlement of Type 4340 steel has been investigated by straining round-notched specimens in 10(5) Pa hydrogen atmosphere at a constent cross-head spead of 1.4x10(-4) mm/s. The circumferentially notched spe...Hydrogen embrittlement of Type 4340 steel has been investigated by straining round-notched specimens in 10(5) Pa hydrogen atmosphere at a constent cross-head spead of 1.4x10(-4) mm/s. The circumferentially notched specimens exhibited a significant embrittlement when their mechanical behaviour in hydrogen was compared with that in air. Although the effect of notch depth on fracture strength in air is negligible, an increase in the depth of notch increase susceptibility to embrittlement when testing in gaseous hydrogen. However, analysis of the effects is complicated by the facts that (i) the specimens show some degree of notch severity even when strained in air and (ii) the behaviour is complicated by the localised plastic deformation that may occur for relatively shallow notches. Such effects are eliminated at high stress concentration factors, so there is a systematic loss in fracture stress in hydrogen as the notch sensitivity increases from K-t=2.6 to 5.7 (where a 87% reduction of fracture stress occurs) but a relatively stable value is then reached even for very severe notching by fatigue pre-cracking. Whether or not the effect is due to increasing concentration of hydrogen in the triaxial stress region ahead of the notch, there is no doubt that increasing the stress concentration makes hydrogen more effective as an embrittlement agent.展开更多
Background Early withdraw from invasive mechanical ventilation （MV） followed by noninvasive MV is a new strategy for changing modes of treatment. This study was conducted to estimate the feasibility and the efficacy...Background Early withdraw from invasive mechanical ventilation （MV） followed by noninvasive MV is a new strategy for changing modes of treatment. This study was conducted to estimate the feasibility and the efficacy of early extubation and sequential noninvasive MV commenced at beginning of pulmonary infection control window in patients with exacerbated hypercapnic respiratory failure caused by chronic obstructive pulmonary diseases （ C OPD ）. Methods A prospective, randomized controlled study was conducted in eleven teaching hospitals＇ respiratory or medical intensive care units in China. Ninety intubated COPD patients with severe hypercapnic respiratory failure triggered by pulmonary infection （pneumonia or purulent bronchitis） were involved in the study. When the pulmonary infection had been controlled by antibiotics and comprehensive therapy, the “pulmonary infection control window （PIC window）” has been reached. Each case was randomly assigned to study group （extubation and noninvasive MV via facial mask immediately） or control group （ invasive MV was received continuously after PIC window by using conventional weaning technique）. Results Study group （n = 47 ） and control group （n = 43 ） had similar clinical characteristics initially and at the time of PIC window. Compared with control group, study group had shorter duration of invasive MV [ （6. 4±4. 4） days vs （ 11.3±6. 2） days, P =0. 0001, lower rate of ventilator associated pneumonia （VAP） （3/47 vs 12/43, P=0.014）, fewer days in ICU [（12 ＋8） days vs 16 ＋ 11） days, P =0.047] and lower hospital mortality （ 1/47 vs 7/43, P =0. 025）. Conclusions In COPD patients requiring intubation and lnvasive MV for hypercapnic respiratory failure, which is exacerbated by pulmonary infection, early extubation followed by noninvasive MV initiated at the start of PIC window may decrease significantly the duration of invasive MV, the risk of VAP and hospital mortality.展开更多
The heavy chain Fd genes and K chain genes of immunoglobulin were amplified by RT-PCR from PBL of three volunteer donors with HIV-positive. Phage antibody library was constructed with the Fd genes and K chain genes us...The heavy chain Fd genes and K chain genes of immunoglobulin were amplified by RT-PCR from PBL of three volunteer donors with HIV-positive. Phage antibody library was constructed with the Fd genes and K chain genes using pComb3 as vector. Three-round selection against coated gpl20 showed specific enrichment of phage antibodies. After the third round selection, 40 out of 50 clones exhibited gpl20 binding capacity. The specificity of the clones was verified by ELISA and competition inhibition ELISA. The V_H was derived from subgroups V_Ⅱ and V_Ⅲ, V_L belonged to subgroups V_K Ⅰ and V_K Ⅲ with DNA sequencing. These results suggest that the antibodies obtained are specific to gpi20.展开更多
Melt flow has an important influence on the microstructure formation of alloys. In this paper the growth behaviour of constrained crystals is systematically studied. It is discovered that the constrained crystals have...Melt flow has an important influence on the microstructure formation of alloys. In this paper the growth behaviour of constrained crystals is systematically studied. It is discovered that the constrained crystals have a quite complicated response to melt flow. It may grow upstream or downstream or keep its growth direction unchanged with the influence of melt flow. Also low growth velocity and high flow velocity favour the formation of spike-like crystal. A new model is suggested to explain these experimental results.展开更多
文摘Hydrogen embrittlement of Type 4340 steel has been investigated by straining round-notched specimens in 10(5) Pa hydrogen atmosphere at a constent cross-head spead of 1.4x10(-4) mm/s. The circumferentially notched specimens exhibited a significant embrittlement when their mechanical behaviour in hydrogen was compared with that in air. Although the effect of notch depth on fracture strength in air is negligible, an increase in the depth of notch increase susceptibility to embrittlement when testing in gaseous hydrogen. However, analysis of the effects is complicated by the facts that (i) the specimens show some degree of notch severity even when strained in air and (ii) the behaviour is complicated by the localised plastic deformation that may occur for relatively shallow notches. Such effects are eliminated at high stress concentration factors, so there is a systematic loss in fracture stress in hydrogen as the notch sensitivity increases from K-t=2.6 to 5.7 (where a 87% reduction of fracture stress occurs) but a relatively stable value is then reached even for very severe notching by fatigue pre-cracking. Whether or not the effect is due to increasing concentration of hydrogen in the triaxial stress region ahead of the notch, there is no doubt that increasing the stress concentration makes hydrogen more effective as an embrittlement agent.
文摘Background Early withdraw from invasive mechanical ventilation （MV） followed by noninvasive MV is a new strategy for changing modes of treatment. This study was conducted to estimate the feasibility and the efficacy of early extubation and sequential noninvasive MV commenced at beginning of pulmonary infection control window in patients with exacerbated hypercapnic respiratory failure caused by chronic obstructive pulmonary diseases （ C OPD ）. Methods A prospective, randomized controlled study was conducted in eleven teaching hospitals＇ respiratory or medical intensive care units in China. Ninety intubated COPD patients with severe hypercapnic respiratory failure triggered by pulmonary infection （pneumonia or purulent bronchitis） were involved in the study. When the pulmonary infection had been controlled by antibiotics and comprehensive therapy, the “pulmonary infection control window （PIC window）” has been reached. Each case was randomly assigned to study group （extubation and noninvasive MV via facial mask immediately） or control group （ invasive MV was received continuously after PIC window by using conventional weaning technique）. Results Study group （n = 47 ） and control group （n = 43 ） had similar clinical characteristics initially and at the time of PIC window. Compared with control group, study group had shorter duration of invasive MV [ （6. 4±4. 4） days vs （ 11.3±6. 2） days, P =0. 0001, lower rate of ventilator associated pneumonia （VAP） （3/47 vs 12/43, P=0.014）, fewer days in ICU [（12 ＋8） days vs 16 ＋ 11） days, P =0.047] and lower hospital mortality （ 1/47 vs 7/43, P =0. 025）. Conclusions In COPD patients requiring intubation and lnvasive MV for hypercapnic respiratory failure, which is exacerbated by pulmonary infection, early extubation followed by noninvasive MV initiated at the start of PIC window may decrease significantly the duration of invasive MV, the risk of VAP and hospital mortality.
文摘The heavy chain Fd genes and K chain genes of immunoglobulin were amplified by RT-PCR from PBL of three volunteer donors with HIV-positive. Phage antibody library was constructed with the Fd genes and K chain genes using pComb3 as vector. Three-round selection against coated gpl20 showed specific enrichment of phage antibodies. After the third round selection, 40 out of 50 clones exhibited gpl20 binding capacity. The specificity of the clones was verified by ELISA and competition inhibition ELISA. The V_H was derived from subgroups V_Ⅱ and V_Ⅲ, V_L belonged to subgroups V_K Ⅰ and V_K Ⅲ with DNA sequencing. These results suggest that the antibodies obtained are specific to gpi20.
文摘Melt flow has an important influence on the microstructure formation of alloys. In this paper the growth behaviour of constrained crystals is systematically studied. It is discovered that the constrained crystals have a quite complicated response to melt flow. It may grow upstream or downstream or keep its growth direction unchanged with the influence of melt flow. Also low growth velocity and high flow velocity favour the formation of spike-like crystal. A new model is suggested to explain these experimental results.
