Relationship of actin, microtubules, and crosswall synthesis during septation in Aspergillus nidulans

A significant limitation of neural networks is that the representations they learn are usually incomprehensible to humans. We have developed an algorithm, called TREPAN, for extracting comprehensible, symbolic representations from trained neural networks. Given a trained network, TREPAN produces a decision tree that approximates the concept represented by the network. In this article, we discuss the application of TREPAN to a neural network trained on a noisy time series task: predicting the Dollar-Mark exchange rate. We present experiments that show that TREPAN is able to extract a decision tree from this network that equals the network in terms of predictive accuracy, yet provides a comprehensible concept representation. Moreover, our experiments indicate that decision trees induced directly from the training data using conventional algorithms do not match the accuracy nor the comprehensibility of the tree extracted by TREPAN.     

Changes in actin filament organization during pseudopod formation

Fluorescent phalloidin has been introduced into Dicytostelium amoebae in order to visualize dynamic changes in the localization of F-actin during pseudopod extension. Phalloidin was initially localized to the peripheral cortex of the cell. Newly formed pseudopods were not fluorescent, indicating that phalloidin was tightly bound to existing F-actin filaments and could not rapidly relocalize to newly formed filaments. As pseudopod extension proceeded, the fluorescent signal disappeared from the region directly underlying the expansion zone, leaving a gap in the actin cortex. Similar results were obtained in both wild-type cells and those lacking myosin II heavy chain. The disappearance of the fluorescent signal from the cortical region underlying the new pseudopod is presumed to be due to breakdown of the actin cortex and dispersion of the remnants. These results suggest that new pseudopods are not built upon the existing actin cortex but rather that the cortex is locally solated as part of the construction of the new actin network.     

Heterologous expression of rat epitope-tagged histamine H2 receptors in insect Sf9 cells

1. Rat histamine H2 receptors were epitope-tagged with six histidine residues at the C-terminus to allow immunological detection of the receptor. Recombinant baculoviruses containing the epitope-tagged H2 receptor were prepared and were used to infect insect Sf9 cells. 2. The His-tagged H2 receptors expressed in insect Sf9 cells showed typical H2 receptor characteristics as determined with [125I]-aminopotentidine (APT) binding studies. 3. In Sf9 cells expressing the His-tagged H2 receptor histamine was able to stimulate cyclic AMP production 9 fold (EC50=2.1+/-0.1 microM) by use of the endogenous signalling pathway. The classical antagonists cimetidine, ranitidine and tiotidine inhibited histamine induced cyclic AMP production with Ki values of 0.60+/-0.43 microM, 0.25+/-0.15 microM and 28+/-7 nM, respectively (mean+/-s.e.mean, n=3). 4. The expression of the His-tagged H2 receptors in infected Sf9 cells reached functional levels of 6.6+/-0.6 pmol mg(-1) protein (mean+/-s.e.mean, n=3) after 3 days of infection. This represents about 2 x 10(6) copies of receptor/cell. Preincubation of the cells with 0.03 mM cholesterol-beta-cyclodextrin complex resulted in an increase of [125I]-APT binding up to 169+/-5% (mean+/-s.e.mean, n=3). 5. The addition of 0.03 mM cholesterol-beta-cyclodextrin complex did not affect histamine-induced cyclic AMP production. The EC50 value of histamine was 3.1+/-1.7 microM in the absence of cholesterol-beta-cyclodextrin complex and 11.1+/-5.5 microM in the presence of cholesterol-beta-cyclodextrin complex (mean+/-s.e.mean, n=3). Also, the amount of cyclic AMP produced in the presence of 100 microM histamine was identical, 85+/-18 pmol/10(6) cells in the absence and 81+/-11 pmol/10(6) cells in the presence of 0.03 mM cholesterol-beta-cyclodextrin complex (mean+/-s.e.mean, n=3). 6. Immunofluorescence studies with an antibody against the His-tag revealed that the majority of the His-tagged H2 receptors was localized inside the insect Sf9 cells, although plasma membrane labelling could be identified as well. 7. These experiments demonstrate the successful expression of His-tagged histamine H2 receptors in insect Sf9 cells. The H2 receptors couple functionally to the insect cell adenylate cyclase. However, our studies with cholesterol complementation and with immunofluorescent detection of the His-tag reveal that only a limited amount of H2 receptor protein is functional. These functional receptors are targeted to the plasma membrane.     

Subunit assembly and guanine nucleotide exchange activity of eukaryotic initiation factor-2B expressed in Sf9 cells

Eukaryotic initiation factor-2B (eIF-2B) is a guanine nucleotide exchange factor (GEF) that plays a key role in the regulation of protein synthesis. In this study, we have used the baculovirus-infected Sf9 insect cell system to express and characterize the five dissimilar subunits of rat eIF-2B. GEF activity was detected in extracts of Sf9 cells expressing the epsilon-subunit alone and was greatly increased when all five subunits were coexpressed. In addition, high GEF activity was observed in extracts containing a four-subunit complex lacking the alpha-subunit. Assembly of an eIF-2B holoprotein was confirmed by coimmunoprecipitation of all five subunits. Gel filtration chromatography revealed that recombinant eIF-2B had the same molecular mass as eIF-2B purified from rat liver and that it did indeed possess GEF activity. Phosphorylation of the substrate eIF-2 inhibited the GEF activity of the five-subunit eIF-2B; this inhibition required the eIF-2B alpha-subunit. The results demonstrate that eIF-2Balpha functions as a regulatory subunit that is not required for GEF activity, but instead mediates the regulation of eIF-2B by substrate phosphorylation. Furthermore, eIF-2Bepsilon is necessary and is perhaps sufficient for GEF activity in vitro.     

Interaction of glucocorticosteroid receptor and wild-type or mutated 90-kDa heat shock protein coexpressed in baculovirus-infected Sf9 cells

Coexpression of the human glucocorticosteroid receptor (hGR) and chicken 90-kDa heat shock protein alpha (chsp90) in recombinant baculovirus-infected Sf9 cells is a system that provides a large quantity of wild-type chsp90-hGR complexes able to bind hormone ([3H]triamcinolone acetonide; TA), sedimenting at 8 S, and displaceable to 11 S by BF4 and D7 alpha anti-chsp90 monoclonal antibodies. Thus, we were able to examine the effects of selective chsp90 mutations on hetero-oligomeric complex formation. Two deletions involved hydrophilic regions, A between amino acids 221 and 290 and B between amino acids 530 and 581, and the third, Z, removed a central leucine heptad repeat region (amino acids 392-419). When these chsp90 mutants were expressed, the lack of displacement of [3H]TA receptor complexes on sucrose gradient by specific chsp90 antibodies was consistent with the formation of [3H]TA receptor complexes containing only endogenous insect hsp90. By using an immunoadsorption method and sedimentation analysis, we found that the deletion of region A precluded the interaction of chsp90 with the hGR, while B and Z deletions led to formation of abnormal complexes with the hGR, which displayed large forms (> 10 S), were unable to bind hormone, and apparently formed only small amounts of tightly bound nuclei hGR upon in vivo hormone treatment. As a whole, the data are consistent with distinct roles of hsp90 regions in hGR function.     

Both microtubules and actin filaments are required for efficient postendocytotic traffic of the polymeric immunoglobulin receptor in polarized Madin-Darby canine kidney cells

It has been postulated that membrane traffic in polarized epithelial cells requires both actin filaments and microtubules. We have tested this hypothesis by analyzing the effect of cytochalasin D (cytoD; an actin-disrupting agent), by itself or in combination with nocodazole (a microtubule depolymerizing agent), on postendocytic traffic in Madin-Darby canine kidney cells. CytoD treatment inhibited basolateral to apical transcytosis of IgA in polymeric immunoglobulin receptor-expressing cells by approximately 45%, but had little effect on basolateral recycling of transferrin. Apical recycling of IgA was also inhibited by approximately 20%. Like nocodazole, cytoD acted at an early step in transcytosis, and inhibited translocation of IgA between the basolateral early endosomes and the apical recycling endosome. There was little inhibition of the subsequent release of IgA from the apical recycling endosome of cytoD- or nocodazole-treated cells. Order-of-addition experiments suggest that the cytoD-sensitive step preceded the nocodazole-sensitive step. Treatment with both cytoD and nocodazole inhibited transcytosis 95%. These results suggest that in addition to microtubules, efficient postendocytic traffic in polarized epithelial cells also requires actin filaments.     

Disassembly of actin filaments leads to increased rate and frequency of mitochondrial movement along microtubules

In activated sea urchin coelomocytes, cytoplasmic organelles move along distinct actin and microtubule dependent pathways, actin-based motility is driven by an unconventional myosin, and microtubule disassembly does not effect actin-dependent organelle motility [D'Andrea et al., 1994: J. Cell Sci. 107:2081-2094]. Given the growing evidence for potential interactions between components of the actin and microtubule cytoskeletons, we examined the effect of actin filament disassembly on the movement of mitochondria along microtubules in activated coelomocytes. Coelomocytes treated with cytochalasin B (CB), to disrupt actin filaments, exhibited a thinning of the cytoplasm, enhanced lateral undulation of microtubules, and ceased centripetal cortical flow of actin. Interestingly, the loss of actin filaments resulted in a approximately 1.5-fold increase in the average velocity of outward and inward moving mitochondria and increased the frequency of centripetal movement. To test if enhanced motility along microtubules was a consequence of decreased actin-myosin interaction, coelomocytes were treated with 2,3-butanedione monoxime (BDM), a potent inhibitor of myosin activity [Cramer and Mitchison, 1995: J. Cell Biol. 131:179-189]. BDM inhibited all types of actin-based motility observed in these cells including retrograde cortical flow, protrusion and retraction of the cell edge, and movement of intracellular organelles. Surprisingly, BDM treatment stopped the movement of mitochondria in CB-exposed cells, suggesting that BDM can also act as an inhibitor of organelle movement along microtubules. Collectively, these data demonstrated that microtubule-dependent mitochondrial motility and microtubule movement were sensitive to changes in the assembly state of the actin cytoskeleton.     

连铸钢包浇注过程中旋涡的形成机理

连铸钢包浇注末期出现的旋涡卷渣现象会对连铸钢水质量产生重要的影响,为了有效控制生产中的旋涡卷渣现象,对钢包浇注末期旋涡的产生机理开展详细研究.依据相似原理,构建了相似比为1∶6的钢包物理模型,对钢包浇注过程中旋涡产生及卷渣过程进行研究,分析了初始液面高度、出水口尺寸与布置位置、出水口结构等因素对旋涡形成规律的影响.结果表明：旋涡形成过程与初始液面高度无关;钢包出水口尺寸和布置位置对于旋涡形成过程影响显著.随着出水口直径的增大,旋涡临界高度逐渐增加;随着偏心率的增加,旋涡临界高度逐渐降低,最佳偏心率为3/4.提出三片挡块式出水口结构,可以显著降低钢包浇注末期的旋涡临界高度,降低高度达50％左右.     

Relationship between microtubule dynamics and lamellipodium formation revealed by direct imaging of microtubules in cells treated with nocodazole or taxol

Microtubules (MTs) contribute to the directional locomotion of many cell types through an unknown mechanism. Previously, we showed that low concentrations (<200 nM) of nocodazole or taxol reduced the rate of locomotion of NRK fibroblasts over 60% without altering MT polymer level [Liao et al., 1995: J. Cell Sci. 108:3473-3483]. In this paper, we directly measured the dynamics of MTs in migrating NRK cells injected with rhodamine tubulin and treated with low concentrations of nocodazole or taxol. Both drug treatments caused statistically significant reductions (approx. twofold) in growth and shortening rates and less dramatic effects on rescue and catastrophe transition frequencies. The percent time MTs were inactive (i.e., paused) increased greater than twofold in nocodazole- and taxol-treated cells, while the percent time growing was substantially reduced. Three parameters of MT dynamics were linearly related to the rates of locomotion determined previously: rate of shortening, percent time pausing and percent time growing. The number of MTs that came within 1 microm of the leading edge was reduced in drug-treated cells, suggesting that reduced MT dynamics may affect actin arrays necessary for cell locomotion. We examined two such structures, lamellipodium and adhesion plaques, and found that lamellipodia area was coordinately reduced with MT dynamics. No effect was detected on adhesion plaque density or distribution. In time-lapse recordings, MTs did not penetrate into the lamellipodium of untreated cells, suggesting that MTs affect lamellipodia either through their interaction with factors at the base of the lamellipodium or by releasing factors that diffuse into the lamellipodia. In support of the latter hypothesis, when all MTs were rapidly depolymerized by 20 microM nocodazole, we detected the rapid formation of exaggerated protrusions from the leading edge of the cell. Our results show for the first time a linear relationship between MT dynamics and the formation of the lamellipodium and support the idea that MT dynamics may contribute to cell locomotion by regulating the size of the lamellipodium, perhaps through diffusable factors.     

Susceptibility of the Sf9 insect cell line to infection with adventitious viruses

Sf9, the insect cell line commonly used for gene expression by recombinant baculovirus (BV), can be infected by St. Louis encephalitis (SLE) virus, a flavivirus, resulting in a persistent, productive, and cytopathic infection, while retaining the ability to be infected with a recombinant baculovirus (rBV). We now demonstrate using double immunofluorescence that single cells are dually infected with SLE virus and rBV. Fourteen additional viruses including additional flaviviruses, other arbovirus classes, vesicular stomatitis virus (VSV), and herpes simplex virus, type 1 (HSV-1) failed to produce a cytopathic effect (CPE) in Sf9 cells. Plaque assays indicated infectious virus was present for several weeks post-inoculation for Yellow fever (YF), Dengue types 1 and 2 (DEN-1 and DEN-2), Gumbo limbo (GL), Eastern equine encephalomyelitis virus (EEE), Western equine encephalomyelitis virus (WEE), HSV-1, and VSV viruses. For HSV-1, GL, EEE, WEE and VSV, but not for YF, DEN-1 or DEN-2 viruses, this could be attributed solely to survival in the Sf9 cell culture media. Of the 14 viruses tested, only HSV-1 could be detected after 2 weeks in serum-free media. The data indicate that several viruses which are pathogenic for humans are stable for long periods of time at 27 degrees C in the serum-containing media used for cultivation of Sf9 cells. YF, DEN-1 and DEN-2 viruses may replicate in Sf9 cells at extremely low levels. This suggests that adventitious agents which do not produce obvious CPE or interfere with rBV infection or recombinant protein expression could contaminate Sf9 cell cultures or media.     

Tubulin-nucleotide interactions during the polymerization and depolymerization of microtubules

The interactions of nucleotides and their role in the polymerization of tubulin have been studied in detail. GTP promotes polymerization by binding to the exchangeable site (E site) of tubulin. The microtubules formed contain only GDP at the E site, indicating that hydrolysis of E site GTP occurs during or shortly after polymerization. Tubulin prepared by several cycles of polymerization and depolymerization will polymerize in the presence of ATP as well as GTP. Polymerization in ATP is preceded by a distinct lag period which is shorter at higher concentrations of ATP. As reported by others ATP will transphosphorylate bound GDP to GTP. Under polymerizing conditions the maximum level of GTP formation occurs at about the same time as the onset of polymerization, and the lag probably reflects the time necessary to transphosphorylate a critical concentration of tubulin. The transphosphorylated protein can be isolated and will polymerize without further addition of nucleotide. The transphosphorylated GTP is hydrolyzed and the phosphate released during polymerization. About 25% of the phosphate transferred from ATP is noncovalently bound to the subunit as inorganic phosphate and this fraction is also released during polymerization. The nonhydrolyzable analogue of GTP, GMPPNP, will promote microtubule assembly at high concentration. GMPPNP assembled microtubules do not depolymerize in Ca concentrations several fold greater than that which will completely depolymerize GTP assembled tubules; however, addition of Ca prior to inducing polymerization in GMPPNP prevents the formation of microtubules. Thus GTP hydrolysis appears to promote depolymerization rather than polymerization. GDP does not promote microtubule assembly but can inhibit GTP binding and GTP induced polymerization. GDP does not, however, induce the depolymerization of formed microtubules. These experiments demonstrate that tubulin polymerization can not be treated as a thermodynamically reversible process, but must involve one or more irreversible steps. Exchange experiments with [3H]GTP indicate that the "E" site on both microtubules and ring aggregates of tubulin is blocked and does not exchange rapidly. However, during polymerization and depolymerization induced by raising or lowering the temperature, respectively, all the E sites become transiently available and will exchange their nucleotide. This observation does not suggest a direct morphological transition between rings and microtubules. The presence of a blocked E site on the rings explains the apparent transphosphorylation and hydrolysis of "N" site nucleotide reported by others.     

Role of microtubules in milk secretion--action of colchicine on microtubules and exocytosis of secretory vesicles in rat mammary epithelial cells

Effect of colchicine on microtubules was studied in mammary epithelial cells treated both in vivo and in vitro with the alkaloid. Three hours after the intramammary infusion of colchicine, secretory activity of mammary epithelia ceased, milk constituents accumulated and were randomly distributed within the cytoplasm, sometimes leaking into the perialveolar connective tissue, and autophagic vacuoles were prevalent. It appeared that an accelerated involutionary process was occurring. No microtubules were observed after this treatment. In vitro treated cells appeared to be less affected by the alkaloid. Although numerous casein-containing secretory vesicles accumulated in the cytoplasm, lipid droplet accumulation was less, and fewer autophagic vacuoles were observed, although lysosomes were commonly observed. Occasionally, obliquely sectioned microtubules were found in cells treated with low concentrations of colchicine but were absent at higher colchicine concentrations; however, paracrystalline inclusions (tubulin aggregates) were observed in some cells at all concentrations of the drug. These observations provide evidence that drugs which interfere with microtubule integrity reduce the secretory activity in mammary epithelia. This evidence is consistent with the concept of an association of the microtubular system and the secretory process.     

Characterization of GRK2-catalyzed phosphorylation of the human substance P receptor in Sf9 membranes

G protein-coupled receptor kinases (GRKs) phosphorylate agonist-occupied G protein-coupled receptors (GPCRs), resulting in GPCR desensitization. GRK2 is one of the better studied of the six known GRKs and phosphorylates several GPCRs. In a previous study, we documented that GRK2 and GRK3 phosphorylate purified and reconstituted rat substance P receptor (rSPR) [Kwatra et al. (1993) J. Biol. Chem. 268, 9161-9164]. Here, we characterize in detail GRK2-catalyzed phosphorylation of human SPR (hSPR) in intact membranes. GRK2 phosphorylates hSPR in urea-washed Sf9 membranes in an agonist-dependent manner with a stoichiometry of 19 +/- 1 mol of phosphate/mol of receptor, which increases slightly (1.3-fold increase) in the presence of G beta gamma. Kinetic analyses indicate that receptor phosphorylation occurs with a Km of 6.3 +/- 0.4 nM and a Vmax of 1.8 +/- 0.1 nmol/min/mg; these kinetic parameters are only slightly affected by G beta gamma [Km = 3.6 +/- 1.0 nM and Vmax = 2.2 +/- 0.2 nmol/min/mg]. The lack of a strong stimulatory effect of G beta gamma on GRK2-catalyzed phosphorylation of hSPR is surprising since G beta gamma potently stimulates GRK2-catalyzed phosphorylation of beta 2-adrenergic receptor and rhodopsin. Involvement of G beta gamma endogenously present in membranes is ruled out as a source of high levels of hSPR phosphorylation, since receptor phosphorylation was not affected by guanine nucleotides that suppress or enhance the release of endogenous G beta gamma. The present study determines, for the first time, the kinetics of phosphorylation of a receptor substrate of GRK2 in intact membranes. Further, our results identify hSPR as a unique substrate of GRK2 whose phosphorylation is strong even in the absence of G beta gamma.     

Expression of bovine activin-A and inhibin-A in recombinant baculovirus-infected Spodoptera frugiperda Sf 21 insect cells

Currently, bioactive activin and inhibin for investigative purposes are obtained either by purification from bovine or porcine follicular fluid or have been kindly supplied in limited amounts by Genentech. The latter are recombinant formulations produced in cultured monkey kidney CV-1 cells. The aims of this study were to assess the potential of the baculovirus expression system as an alternative means to produce recombinant activin and inhibin. Towards these goals, two recombinant baculoviruses, AcBovACTA and AcBovINHA, were constructed. AcBovACTA contains a contiguous copy of the bovine beta A-inhibin/activin structural gene encoding the beta A-preproprotein whereas AcBovINHA contains contiguous copies of the bovine alpha-inhibin and beta A-inhibin/activin structural genes encoding the alpha- and beta A-preproproteins, respectively. Western blot analyses, using monoclonal antibodies specific for the mature portions of the alpha-inhibin and beta A-inhibin/activin subunits, demonstrated that Spodoptera frugiperda Sf21 cells infected with either recombinant virus secreted mature homodimeric activin-A into the medium. In addition, Sf21 cells infected with the recombinant AcBovINHA virus were found also to produce substantial amounts of the alpha-inhibin precursor protein. However, the mature portion of the latter is not secreted into the medium but is retained within infected cells in an incompletely processed form(s). The recombinant activin-A secreted by Sf21 cells infected with the AcBovACTA virus was shown to possess activin bioactivity when analysed by in vitor bioassay and, therefore, provides an alternative route to mammalian cell expression for the production of recombinant activin-A.     

Reconstitution of receptors and GTP-binding regulatory proteins (G proteins) in Sf9 cells. A direct evaluation of selectivity in receptor.G protein coupling

The selectivity in coupling of various receptors to GTP-binding regulatory proteins (G proteins) was examined directly by a novel assay entailing the use of proteins overexpressed in Spodoptera frugiperda (Sf9) cells. Activation of G proteins was monitored in membranes prepared from Sf9 cells co-expressing selected pairs of receptors and G proteins (i.e. alpha, beta1, and gamma2 subunits). Membranes were incubated with [35S]guanosine 5'-(3-O-thio)triphosphate (GTPgammaS) +/- an agonist, and the amount of radiolabel bound to the alpha subunit was quantitated following immunoprecipitation. When expressed without receptor (but with beta1gamma2), the G protein subunits alphaz, alpha12, and alpha13 did not bind appreciable levels of [35S]GTPgammaS, consistent with a minimal level of GDP/[35S]GTPgammaS exchange. In contrast, the subunits alphas and alphaq bound measurable levels of the nucleotide. Co-expression of the 5-hydroxytryptamine1A (5-HT1A) receptor promoted binding of [35S]GTPgammaS to alphaz but not to alpha12, alpha13, or alphas. Binding to alphaz was enhanced by inclusion of serotonin in the assay. Agonist activation of both thrombin and neurokinin-1 receptors promoted a modest increase in [35S]GTPgammaS binding to alphaz and more robust increases in binding to alphaq, alpha12, and alpha13. Binding of [35S]GTPgammaS to alphas was strongly enhanced only by the activated beta1-adrenergic receptor. Our data identify interactions of receptors and G proteins directly, without resort to measurements of effector activity, confirm the coupling of the 5-HT1A receptor to Gz and extend the list of receptors that interact with this unique G protein to the receptors for thrombin and substance P, imply constitutive activity for the 5-HT1A receptor, and demonstrate for the first time that the cloned receptors for thrombin and substance P activate G12 and G13.     

Numerical simulation of the molten-pool formation during the laser surface-melting process

The boundary-fixing method, by which the moving-boundary problem is reduced into the fixedboundary problem, has been applied to the numerical simulation of the molten-pool formation during the laser surface-melting process. A mathematical formulation and corresponding calculation scheme are developed for a model based on transient three-dimensional heat conduction with a moving solid-liquid interface. By the use of the boundary-fixing method, the heat balance at the solid-liquid interface is rigorously treated in the present numerical simulation. When the steady state is reached, the resulting molten pool is obtained without undulation in shape. The calculated results, based on an Al-32.7 wt pct Cu eutectic alloy, are discussed and compared with experimental data.     

The formation of AIN crystals in an Fe-Mn-Al-C alloy during the nitriding process

We observed the formation of AIN crystals in an Fe-Mn-Al-C alloy during a nitriding process. The composition of the alloy was Fe-30.4 wt pct Mn-8.7 wt pct Al-1.0 wt pct C. The nitriding process consisted of heating the Fe-Mn-Al alloy in pure nitrogen at 1000 °C for 1 hour. During nitriding, AIN crystals formed in the regions near the surface layer of the alloy. The aluminum nitride formed along specifically preferred orientations of the metal matrix. We discovered that the formation of the secondary arms of the AIN crystals was related to the direction of flux of the nitrogen, and we proposed a growth mechanism for the formation of secondary arms on the primary AIN plates. As the supply of nitrogen continued from the surface, the AIN Widmanstätten side plates formed the secondary arms growing on the leeward side of the primary AIN plates.     

不同煤种燃烧过程中NOx形成规律的数值模拟与分析

燃煤过程对大气造成的污染正日益引起人们的关注,控制NOx的排放是煤燃烧利用研究中亟需解决的课题.采用数值模拟方法,研究不同煤种在不同燃烧温度下NOx的生成规律,并对燃烧过程中的NOx生成的影响因素及抑制方法进行分析和归纳.结果表明:中挥发分煤(mv)燃烧生成的NOx最多,低挥发分煤(lv)燃烧生成的NOx最少;热力型NOx的生成与温度有直接的关系.因此,缩短燃烧产物在高温区的滞留时间有助于减少NOx的生成,减少反应中氧气的质量浓度能够抑制NOx的生成,其计算结果可为今后的工业性实验提供理论依据.