Effects of Salinity Fluctuation Frequency on the Growth, Molting Rate and Hemolymph 20-Hydroxyecdysone Concentration in Juvenile Chinese shrimp, Fenneropenaeus chinensis

This experiment was conducted to examine the effects of salinity fluctuation frequency on the growth, molting rate and hemolymph 20-hydroxyecdysone （20-HE） concentration for juvenile Fenneropenaeus chinensis with an initial wet body weight of 1.115 g±0.012 g. The salinity of the control treatment （represented by DO） was 28 throughout the experiment, whereas treatments D2, D4, D6 and D8 were subjected to different salinity fluctuation frequencies of 2, 4, 6 and 8 d, respectively. The range of salinity fluctuation was 4. The salinity in treatments D2, D4, D6 and D8 was kept at 28 for 2, 4, 6 and 8d, respectively; each original salinity was decreased abruptly to salinity 24, which first lasted for another 2 d and was then raised to its initial value 28. This constituted a salinity fluctuation cycle and afterwards the cycle repeated. It was found that： 1） The weight gain of shrimp in treatment D4 was 202.9% and significantly higher than that in treatment DO （P〈0.05）. The molting rate in treatment D2 was the lowest, while that in treatment D6 was the highest and significantly higher than those in treatments DO and D2 （P〈0.05）. 2） The hemolymph 20-HE concentration of shrimps in all treatments was at low levels and increased first gradually during the inter-molt period and then increased sharply. It reached a peak value during the pre-molt stage, and then decreased abruptly during the post-molt stage when the lowest level occurred. 3） During the post-molt stage, the hemolymph 20-HE concentration in treatment D2 was 7.47pg μL^-1 and significantly higher than that in treatment DO （P〈0.05）. There were, however, no significant differences in hemolymph 20-HE concentration among all five treatments during the inter-molt stage （P〉0.05）. During the pre-molt stage, the hemolymph 20-HE concentration in treatment D6 was significantly higher than that in treatment DO （P〈0.05）, whereas the hemolymph 20-HE concentration in treatment D2 was significantly lower than that in other treatments （P〈0.05）. Adequate salinity fluctuation promoted the molting rate through increasing hemolymph 20-HE concentration at the pre-molt stage.

Epidermal collagenase activity and its induction by 20-hydroxyecdysone in the fiddler crab Uca pugilator

The epidermal collagenase activity and its induction by 20-hydroxyecdysone in Uca pugilator were investigated. Zymographic electrophoresis showed four bands of collagenase activity, 16, 19, 22 and 29 kDa in molecular weight, with the former two accounting for 60% and 36% , respectively, of the total collagenase activity. The collagenase activity varies during the molting cycle. Among the molt stages tested, Premolt Stage Do exhibited the highest epidermal collagenase activity for both the 16 and 19 kDa isoenzymes and, as the molt stage proceeded, the enzymatic activity of these two isoenzymes decreased, with the lowest activity for both found in Premolt Stage D3 -4 - Injection of 20-hydroxyecdysone significantly induced the activity of the 16 kDa eollagenase in the epidermis of Uca pugilator, suggesting that the activity of this isoenzyme is under molting hormone control. Although 20-hydroxyeedysone injection did not result in a statistically significant increase in the activity of the 19 kDa isoenzyme, a tendency of the induction was nonetheless demonstrated. This is the first report on epidermal collagenase activity and its induction by the molting hormone in a crustacean .

20-Hydroxyecdysone from Dacrycarpus imbricatus bark inhibits the proliferation of acute myeloid leukemia cells

Objective:To investigate the anti-proliferative effects of 20-hydroxyecdysone isolated from the bark of Dacrycarpus imbricatus(Blume) de Laub.Methods:Column chromatography was used for isolation of compounds from plant material.The structure of the isolated compound was identified by mass spectrometry and nuclear magnetic resonance techniques,including HSQC,HMBC,NOE-difference experiments.The isolated compound was tested for its anti-proliferative activity in acute myeloid leukemia(AML) and OCI-AML cells.Results:Compound 1 was isolated from the ethyl acetate fraction of Dacrycarpus imbricatus barks by column chromatography.Its chemical structure was identified as 20-hydroxyecdysone(20HE),a cholestane-type ecdysteroid,by a combination of mass spectrometry and nuclear magnetic resonance spectrometric analyses.Our goal was to test the anti-proliferative activity of 20 HE using the OCI-AML cell line.20 HE significantly decreased OCI cell number at a concentration of 1 mg/mL,whereas lower concentrations were ineffective.Moreover,this decrease was due to partial blockage of the G_1/S phase of the cell cycle,with a reduction of cells in the G_2M phase,not due to increased apoptosis.Conclusions:This indicates that 20 HE significantly decreases the number of cells in the G_1/S phase of the cell cycle in human AML cells.This is the first time that the anti-proliferative activity of 20 HE against a human tumor cell line has been reported.

20-Hydroxyecdysone Improves Neuronal Differentiation of Adult Hippocampal Neural Stem Cells in High Power Microwave Radiation-Exposed Rats

Objective The hippocampus is thought to be a vulnerable target of microwave exposure.The aim of the present study was to investigate whether 20-hydroxyecdysone(20E)acted as a fate regulator of adult rat hippocampal neural stem cells(NSCs).Furthermore,we investigated if 20E attenuated high power microwave(HMP)radiation-induced learning and memory deficits.Methods Sixty male Sprague-Dawley rats were randomly divided into three groups:normal controls,radiation treated,and radiation+20E treated.Rats in the radiation and radiation+20E treatment groups were exposed to HPM radiation from a microwave emission system.The learning and memory abilities of the rats were assessed using the Morris water maze test.Primary adult rat hippocampal NSCs were isolated in vitro and cultured to evaluate their proliferation and differentiation.In addition,hematoxylin&eosin staining,western blotting,and immunofluorescence were used to detect changes in the rat brain and the proliferation and differentiation of the adult rat hippocampal NSCs after HPM radiation exposure.Results The results showed that 20E induced neuronal differentiation of adult hippocampal NSCs from HPM radiation-exposed rats via the Wnt3a/β-catenin signaling pathway in vitro.Furthermore,20E facilitated neurogenesis in the subgranular zone of the rat brain following HPM radiation exposure.Administration of 20E attenuated learning and memory deficits in HPM radiation-exposed rats and frizzled-related protein(FRZB)reduced the 20E-induced nuclear translocation ofβ-catenin,while FRZB treatment also reversed 20E-induced neuronal differentiation of NSCs in vitro.Conclusion These results suggested that 20E was a fate regulator of adult rat hippocampal NSCs,where it played a role in attenuating HPM radiation-induced learning and memory deficits.

Genome-wide CRISPR screening reveals key genes and pathways associated with 20-hydroxyecdysone signal transduction in the silkworm(Bombyx mori)

Metamorphosis is a complex developmental process involving multiple pathways and a large number of genes that are regulated by juvenile hormone(JH)and 20-hydroxyecdysone(20E).Despite important progress in understanding various aspects of silkworm biology,the hormone signaling pathway in the silkworm remains poorly understood.Genome-wide screening using clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR-associated protein 9(Cas9)-based libraries has recently emerged as a novel method for analyzing genome function,enabling further research into essential genes,drug targets,and virus-host interaction.Previously,we constructed a genome-wide CRISPR/Cas9-based library of the silkworm(Bombyx mori)and successfully revealed the genes involved in biotic or abiotic stress factor responses.In this study,we used our silkworm CRISPR library and large-scale genome-wide screening to analyze the key genes in the silkworm 20E signaling pathway and their mechanisms of action.Functional annotation showed that 20E regulates key proteins in processes that mainly occur in the cytoplasm and nucleus.Pathway enrichment analysis showed that 20E can activate phosphorylation and may affect innate immunity,interfere with intracellular nutrition and energy metabolism,and eventually cause cell apoptosis.The screening results were experimentally validated by generating cells with knockout alleles of the relevant genes,which had increased tolerance to 20E.Our findings provide a panoramic overview of signaling in response to 20E in the silkworm,underscoring the utility of genome-wide CRISPR mutant libraries in deciphering hormone signaling pathways and the mechanisms that regulate metamorphosis in insects.

Steroid hormone 20-hydroxyecdysone disturbs fat body lipid metabolism and negatively regulates gluconeogenesis in Hyphantria cunea larvae

The steroid hormone 20-hydroxyecdysone(20E)has been described to regulate fat body lipid metabolism in insects,but its accurate regulatory mechanism,especially the crosstalk between 20E-induced lipid metabolism and gluconeogenesis remains largely unclear.Here,we specially investigated the effect of 20E on lipid metabolism and gluconeogenesis in the fat body of Hyphantria cunea larvae,a notorious pest in forestry.Lipidomics analysis showed that a total of 1907 lipid species were identified in the fat body of H.cunea larvae assigned to 6 groups and 48 lipid classes.The differentially abundant lipids analysis showed a significant difference between 20E-treated and control samples,indicating that 20E caused a remarkable alteration of lipidomics profiles in the fat body of H.cunea larvae.Further studies demonstrated that 20E accelerated fatty acidβ-oxidation,inhibited lipid synthesis,and promoted lipolysis.Meanwhile,the activities of pyruvate carboxylase,phosphoenolpyruvate carboxykinase,fructose-1,6-bisphosphatase,and glucose-6-phosphatase were dramatically suppressed by 20E in the fat body of H.cunea larvae.As well,the transcriptions of genes encoding these 4 rate-limiting gluconeogenic enzymes were significantly downregulated in the fat body of H.cunea larvae after treatment with 20E.Taken together,our results revealed that 20E disturbed fat body lipid homeostasis,accelerated fatty acidβ-oxidation and promoted lipolysis,but negatively regulated gluconeogenesis in H.cunea larvae.The findings might provide a new insight into hormonal regulation of glucose and lipid metabolism in insect fat body.

Protective effects of 20-hydroxyecdysone on H_2 O_2-induced cytotoxicity in human neuroblastoma SH-SY5Y cells

The aim of this study was to investigate the possible protective effects and mechanisms of 20-hydroxyecdysone, an insect steroid hormone, on HEO2-induced cytotoxicity in human neuroblastoma SH-SYSY cells. Pretreatment with 20-hydroxyecdysone significantly elevated the cell viability and decreased LDH leakage in H2O2-treated SH-SY5Y cells. 20-Hydroxyecdysone also dramatically reduced malondialdehyde （MDA） contents and enhanced the superoxide dismutase （SOD） activities under oxidative stress conditions. Furthermore, 20-hydroxyecdysone pretreatment inhibited apoptosis by decreasing the Bax/Bcl-2 ratio and attenuating the activation of caspase-3. These results suggest that 20-hydroxyecdysone can protect SH-SYSY cells against H2O2-induced cytotoxicity and might potentially be used to treat neurodegenerative diseases induced by oxidative stress and anontosis.

BmMD-2A responds to 20-hydroxyecdysone and regulates Bombyx mori silkworm innate immunity in larva-to-pupa metamorphosis

20E-hydroxyecdysone(20E)plays important roles in larval molting and metamorphosis in insects and is also involved in the insect innate immune response.Insect metamorphosis is a highly successful strategy for environmental adaptation and is the most vulnerable stage during which the insect is susceptible to various pathogens.20E regulates a series of antimicrobial peptides(AMPs)through the immunodeficiency(IMD)pathway activation in Drosophila;nevertheless,whether other immune pathways are involved in 20E-regulated insect immunity is unknown.Our previous studies showed that BmMD-2A is a member of the MD-2-related lipid recognition(ML)family of proteins that are involved in the Bombyx mori innate immunity Toll signaling pathway.In this study,we further demonstrate that BmMD-2A is also positively regulated by 20E,and the BmMD-2A neutralization experiment suggested that 20E activates some downstream immune effect factors,the AMP genes against Escherichia coli and Staphylococcus aureus,through the regulation of BmMD-2A in larval metamorphosis,implying that B.mori may use the Toll-ML signaling pathway to maintain innate immune balance in the larval-pupal metamorphosis stage,which is a different innate immunity pathway regulated by 20E compared to the IMD pathway in Drosophila.

Identification of LmUAP1 as a 20-hydroxyecdysone response gene in the chitin biosynthesis pathway from the migratory locust, Locusta migratoria

In Locusta migratoria, we found that two chitin biosynthesis genes, UDP N-acetylglucosamine pyrophosphorylase gene LmUAP1 and chitin synthase gene Lm- CHS1, are expressed mainly in the integument and are responsible for cuticle formation. However, whether these genes are regulated by 20-hydroxyecdysone （20E） is still largely unclear. Here, we showed the developmental expression pattern ofLmUAP1, LmCHS1 and the corresponding 20E titer during the last instar nymph stage of locust. RNA interference （RNAi） directed toward a common region of the two isoforms of LmEcR （LmEcRcom） reduced the expression level of LmUAP1, while there was no difference in the expression of LmCHS1. Meantime, injection of 20E in vivo induced the expression of LmUAP1 but not LmCHS1. Further, we found injection-based RNAi of LmEcRcom resulted in 100% mortality. The locusts failed to molt with no apolysis, and maintained in the nymph stage until death. In conclusion, our preliminary results indicated that LmUAP1 in the chitin biosynthesis pathway is a 20E late-response gene and LmEcR plays an essential role in locust growth and development, which could be a good potential target for RNAi-based pest control.

Juvenile hormone membrane signaling phosphorylates USP and thus potentiates 20-hydroxyecdysone action in Drosophila

Juvenile hormone(JH) and 20-hydroxyecdysone(20 E) coordinately regulate development and metamorphosis in insects. Two JH intracellular receptors, methoprene-tolerant(Met) and germ-cell expressed(Gce), have been identified in the fruit fly Drosophila melanogaster. To investigate JH membrane signaling pathway without the interference from JH intracellular signaling, we characterized phosphoproteome profiles of the Met gce double mutant in the absence or presence of JH in both chronic and acute phases.Functioning through a potential receptor tyrosine kinase and phospholipase C pathway, JH membrane signaling activated protein kinase C(PKC) which phosphorylated ultraspiracle(USP) at Ser35, the PKC phosphorylation site required for the maximal action of 20 E through its nuclear receptor complex Ec RUSP. The usp;mutant, in which Ser was replaced with Ala at position 35 by genome editing, showed decreased expression of Halloween genes that are responsible for ecdysone biosynthesis and thus attenuated 20 E signaling that delayed developmental timing. The usp;mutant also showed lower Yorkie activity that reduced body size. Altogether, JH membrane signaling phosphorylates USP at Ser35 and thus potentiates 20 E action that regulates the normal fly development. This study helps better understand the complex JH signaling network.

Steroid hormone 20-hydroxyecdysone promotes CTL1-mediated cellular immunity in Helicoverpa armigera

Mermithid nematodes,such as Ovomermis sinensis,are used as biological control agents against many insect pests,including cotton bollworm(Helicoverpa armigera).However,given the host's robust immune system,the infection rate of O.sinensis is low,thus restricting its widespread use.To understand the host defense mechanisms against mermithid nematodes,we identified and characterized a protein involved in the recognition of O.sinensis,the potential O.sinensis-binding protein C-type lectin 1(HaCTLla and/or HaCTLIb),which was eluted from the surface of O.sinensis after incubation with H.armigera plasma.HaCTLIb is homologous to the previously reported HaCTLla protein.HaCTLI was predominantly expressed in hemocytes and was induced by the steroid hormone 20-hydroxyecdysone through ecdysone receptor(HaEcR)or ultraspiracle(HaUSP),or both.Binding assays confirmed the interactions of the HaCTLI proteins with O.sinensis but not with Romanomermis wuchangensis,a parasitic nematode of mosquito.Moreover,the HaCTL1 proteins were secreted into the hemocoel and promoted hemocyte-mediated encapsulation and phagocytosis.A knockdown of HaEcR and/or HaUSP resulted in compromised encapsulation and phagocytosis.Thus,HaCTLI appears to modulate cellular immunity in the defense against parasitic nematodes,and the 20-hydroxyecdysone-HaEcR-HaUSP complex is involved in regulating the process.

Rapid Determination of Endogenous 20-Hydroxyecdysone in Plants on MALDI-TOF/TOF Mass Spectrometry via Chemical Labeling Based on Boronate Affinity

20-Hydroxyecdysone(20E)derived from plants has a wide range of physiological and pharmacological ef ects on animals and humans,and rapid and sensitive methods for screening of the endogenous 20E in plants are thus required.Herein,a matrixassisted laser desorption/ionization time-of-f ight tandem mass spectrometry(MALDI-TOF/TOF MS)method is described for rapid and sensitive determination of endogenous 20E in plants.It is based on the use of the(3-(acridin-9-ylamino)phenyl)boronic acid(AYPBA)as the mass tag to assist the MS and tandem MS(MS^(n))analysis of 20E on MALDI-TOF/TOF MS.Good linearity was obtained with a determination coef cient(R^(2))larger than 0.99 in the range of 0.025–2.5μΜ.The limit of detection(LOD)was 2.4 fmol.Acceptable precision and accuracy were gained by intra-and inter-day analysis with relative standard deviations less than 19.5%and relative recoveries ranging from 85.7 to 105.2%.In addition,the AYPBA labeled 20E produced abundant characteristic fragment ions under the high energy collision-induced dissociation,which facilitated the identif cation of 20E by MS^(2)analysis on MALDI-TOF/TOF MS.Using the method,we enabled the identif cation and quantif cation of endogenous 20E in four herbs including Cyanotis arachoidea,Achyranthes bidentata,Spinacia oleracea and Chenopodium quinoa willd.,demonstrating the feasibility of the proposed method for screening of the endogenous 20E in plants.

20钢/316L复合管固液复合制坯工艺研究

双金属复合管在石油运输行业中应用前景广阔,结合性能是考察复合管是否合格的重要指标之一。为了能在轧制成形过程中得到高品质的复合管材,在复合管制坯过程中要求实现界面处的冶金复合。以20钢和316L为原材料,基于结合温度及元素扩散情况,采用固液复合方式,并且结合界面的温度模型及通过Pro CAST软件模拟,获得了外模最佳预热温度为1050—1100℃。通过现场试制界面处实现了冶金复合,在最佳温度范围既保证了固态20钢和液态316L之间能达到冶金复合,又能使元素有充分的扩散时间而增强了界面结合强度,同时又可以防止因元素过渡扩散而导致316L腐蚀性能下降。该方法为后续复合管连轧提供了优良的管坯,可实现高品质复合管的现场生产。

血清HMGB1、CCL20、HSP27水平与慢性牙周炎患者牙周病变程度的相关性分析

目的探讨血清高迁移率族蛋白1(HMGB1)、CC趋化因子配体20(CCL20)、热休克蛋白27(HSP27)水平与慢性牙周炎(CP)患者牙周病变程度的相关性。方法选取2021年9月至2023年8月在新乡医学院第一附属医院诊治的60例CP患者纳入观察组,根据1∶1原则,另选取同期牙周健康者60例纳入对照组。比较两组及不同牙周病变程度CP患者血清HMGB1、CCL20、HSP27水平,分析各指标水平与CP牙周病变程度的相关性及联合诊断价值,并分析不同血清水平患者发生CP的危险度。结果观察组血清HMGB1、CCL20、HSP27水平高于对照组(P<0.05);不同牙周病变程度CP患者血清HMGB1、CCL20、HSP27水平比较:轻度<中度<重度,且各指标水平与牙周病变程度均呈正相关(P<0.05);入院时HMGB1、CCL20、HSP27水平联合诊断CP的曲线下面积(AUC)为0.905,最佳诊断敏感度为91.67%,特异度为88.33%,约登指数0.800,且各指标高水平患者发生CP的危险度是低水平的1.105倍、1.034倍、1.105倍(P<0.05)。结论HMGB1、CCL20、HSP27在CP患者血清中呈异常高表达,各指标水平与牙周病变程度均呈正相关,且联合检测对CP具有较高诊断价值,可作为临床诊断CP、评估牙周病变程度的有效指标。

小麦新品种济儒麦20的选育

济儒麦20是济宁市农业科学研究院于2012年以丰收60为母本、08鉴75为父本,利用常规育种技术育成的小麦新品种。该品种产量水平高,抗病性好,高抗叶锈病和条锈病,高抗干热风,落黄好,越冬抗寒性1级。2021-2022年度参加山东省高肥水地组生产试验平均产量为9745.5kg/hm2,比对照济麦22增产5.3%。2022年通过山东省农作物品种审定委员会审定,审定编号:鲁审麦20220005。

2022年4—6月云南异常低温事件的低频特征及成因

利用NCEP/NCAR逐日再分析资料和云南省124个气象站观测资料,首先分析了2022年4—6月云南异常低温事件的极端性及低频振荡变化特征,然后分析了对流层中层和低层大气环流系统低频振荡配置的演变特征。结果表明:1)2022年云南春末夏初(4—6月)出现了气候变暖背景下罕见的极端异常低温事件。平均气温为1961年以来历史同期第5低,1991年以来最低年,全省有42个气象站平均气温达到或突破历史同期最低纪录。2)云南2022年春末夏初的平均气温存在10~20 d显著性周期,方差贡献为45.7%,与实际强降温过程对应关系较好。3)云南10~20 d低频振荡气温降低最大位相7(升高最大位相3),500 hPa上云南被南压的贝加尔湖低频异常高压(低压)与日本海低频异常低压(高压)环流系统间的偏北(偏南)气流控制;700 hPa上中国东部到南海被低频偏北(南)气流控制,低频气温降温(升温)区与之对应,云南被偏东(西)气流控制,位于降温(升温)区;海平面气压场上西伯利亚冷高压增强南移,将高纬度冷空气带到低纬度地区,从而影响云南气温的变化,造成了云南强冷空气过程的形成和发展。因此,高低空低频环流系统配置和演变导致了2022年4—6月云南异常低温事件。4)2022年4—6月,500 hPa上低频正异常高度扰动从高纬度向南传播到贝加尔湖附近,中低纬度低频正异常高度扰动从地中海附近向东移动到贝加尔湖一带,两支低频波列协同作用有利于我国东部和云南地区异常低温事件的产生、加强和维持。5)2022年春末夏初(4—6月),10~20 d低频振荡中,南支西风槽指数和西伯利亚高压指数分别超前云南低频气温7 d和5 d时达到最好的相关关系;这2个指数对云南异常低温过程预报具有很好的提前预示性。

RBM20和MURC双基因杂合变异对心肌细胞结构和生物学特性的影响

目的探讨RNA结合基元蛋白20(RBM20)和肌肉相关卷曲螺旋蛋白(MURC)双基因杂合变异对人心肌细胞AC16(成人左心室心肌细胞系)结构和生物学特性的影响。方法构建对照组、空载组、野生组、MURC或RBM20单基因突变组、RBM20和MURC双基因突变组的心肌细胞AC16;采用Western blotting、免疫荧光染色和实时荧光定量PCR观察心肌细胞中RBM20和MURC定位、细胞表面积、骨架排列、骨架相关蛋白、细胞极性、细胞内钙浓度;采用流式细胞术检测心肌细胞凋亡;采用Ki-67染色检测心肌细胞增殖;采用划痕实验检测心肌细胞迁移。结果与RBM20或MURC单基因突变相比,RBM20和MURC双基因突变对心肌细胞结构和生物学特性影响更显著,表现为细胞表面积增大,细胞肥大相关基因肌球蛋白重链7和α肌动蛋白基因m RNA表达升高,骨架排列紊乱度升高,骨架蛋白β-tubulin和Vinculin荧光强度降低(均P<0.01);极性蛋白Part6荧光强度升高(P<0.05);心肌细胞凋亡率升高,增殖活性下降,迁移率增高,细胞内钙离子浓度升高(均P<0.01)。结论RBM20和MURC双基因杂合变异使心肌细胞结构及生物学特性发生改变,表现为细胞表面积增大,骨架排列紊乱,极性改变,凋亡率和迁移率升高,增殖活性和钙处理能力降低。

郑绿20在GGE双标图分析区试参试品种中的综合评价研究

对连续两年河南省绿豆多点试验的10个新品种农艺及产量性状进行变异性和相关性分析,探讨其相关关系;通过采用GGE双标图分析2019~2020年度河南省绿豆新品种鉴定试验参试品种,综合评价参试品种的丰产性、稳产性、适应性及各试点的试验代表性、鉴别力和区分能力。结果表明,株高、主茎分枝数、单株荚数的变异系数较大;单株荚数与主茎分枝、产量呈显著正相关,主茎节数与株高呈显著正相关。四个试点可以分为两个生态区,参试品种产量表现在双标图中能直观体现。安阳试点对品种有较强的鉴别能力,郑绿20具有较好的丰产性和稳产性,综合表现良好,具有推广价值。

形状系数对20 L球内铝粉分散特性的影响研究

为研究不同形状系数(SF)的铝粉在20 L球型容器中的分散特征,通过建立描述气流携带粉尘形成两相分散系的非稳态数值模型,包括气体流动和粉尘颗粒运动轨迹方程,开展非稳态数值模拟,分析粉尘SF分别为0.2、0.4、0.6、0.8和1.0条件下的粉尘空间分布以及球室中心的湍流动能、速度随时间变化。结果表明:球室内气流携带粉尘分散可以分为进粉、扩散、稳定和沉降4个阶段,其分散均匀性和最大速度值随SF的增加而增强;SF越大,即颗粒形状越接近球形,铝粉尘的分散性越好;SF越小,粉尘容易堆积在壁面附近;标称浓度一定时,SF≤0.4,浓度峰值随SF的增加而增加;SF>0.4,浓度峰值随SF的增加而减小;铝粉-空气混合物的湍流动能最大值随SF值的增加而降低;铝粉颗粒的速度峰值随SF值的增加而升高。

重熔对Al-Ti-La中间合金中Ti_(2)Al_(20)La相的影响

通过扫描电镜、X射线衍射和电子探针等分析研究了重熔过程中不同保温时间和温度对Al-Ti-La中间合金中Ti_(2)Al_(20)La相的含量、形态尺寸和稳定性的影响。结果表明:在750℃下,随着保温时间的延长,Ti_(2)Al_(20)La相的溶解度逐渐增大,含量由未处理的20.776%下降至13.72%,形态由块状演变为圆整和细小的片状,长宽比由2.33下降至1.52;在1000℃下,保温15 min后溶解度较大,含量降低至4.5%,形态演变为尖锐的长条状,长宽比上升至2.55;溶解产生的La原子与Al在晶界处形成La-Al金属间化合物(IMC),Ti原子在基体中的分布密度随保温时间的延长和保温温度的升高而增高,以游离态均匀分布在基体中。