氨化度对聚丙烯腈聚合进程和原液性能的影响

聚丙烯腈(PAN)溶液是制备高性能碳纤维原丝的纺丝溶液,通过氨化改性PAN溶液进行纺丝,可获得结构均质、致密、性能优良的原丝。在丙烯腈/甲基丙烯酸甲酯/衣康酸(AN/MA/ITA)三元聚合体系中加入不同量氨水,研究不同氨化度对PAN转化率、分子量及分布、黏度和亲水性等的影响。结果表明,当氨化度低于20%时,对PAN转化率和分子量及分布影响较小;当氨化度大于20%时,PAN溶液转化率由91.73%降低至87.2%,重均分子量由28.5×10^(4)降低至24.5×10^(4),数均分子量由9.4×10^(4)降低至7.6×10^(4),分布系数由2.98升至3.4,对聚合反应进程和原液指标有明显影响。聚会体系加入氨水后,随着氨化度增加,聚合原液旋转黏度和接触角持续降低,原液旋转黏度由11.9×10^(4)cP下降至9.8×10^(4)cP,接触角由70.1°降低至60.3°,原液亲水性明显改善。

氨化度监控法在锅炉清洗液调配中的应用

针对发电厂锅炉化学清洗时柠檬酸调配存在的问题,提出采用氨化度监控法进行调配,介绍清洗液的配制方法,通过不同条件下柠檬酸浓度检测试验,验证该方法的可行性,并分析了该方法的应用情况及效果,结果表明采用该方法调配清洗液,技术合理、数据准确度高、简便易行。

氨化方式对聚丙烯腈原丝结构和性能的影响

氨化的聚丙烯腈溶液(PAN)是获得均质致密结构、优良理化性能原丝的必要手段。通过丙烯腈(AN)聚合体系加入氨水和聚合结束后在聚合原液中通入氨气,得到不同氨化程度的PAN原液,经干喷湿纺纺丝制成PAN初生纤维和原丝,研究两种氨化方式对PAN纤维截面、初生纤维膨润度和原丝体密度、原丝强度和模量的影响。结果表明,氨化原液容易获得圆形截面的PAN纤维,且聚合体系氨化的原液在氨化度达到16%时,即可获得圆度为0.91的圆形截面,而聚合原液氨化其氨化度需达到28%,才可获得相同圆度(0.91)的截面。氨化后PAN纤维更致密,表现为初生纤维膨润度更低、原丝体密度更高;氨化度小于28%时,聚合体系氨化的原液比聚合原液氨化的原液得到的PAN初生纤维膨润度低、原丝体密度高。氨化度在20%~24%适宜范围,氨化后原丝强度和模量均值较高,且原丝强度和模量CV值明显减少。PAN纤维如需达到相同膨润度、体密度以及强度和模量CV值,聚合体系氨化原液所需的氨化度更低。

Solubility and phase diagrams of hydroxyl manganese chloride

In the course of the basic research on the ammonia-evaporation reaction of manganese monoxide （MnO）, hydroxyl manganese chloride （Mn2（OH）3Cl） was found. The solubility and phase diagrams of the hydroxyl manganese chloride were investigated. The aqueous thermostat and vibrating bed were used to determine the solubility of hydroxyl manganese chloride in water, ammonium chloride and manganese chloride system, and the phase diagrams of multicomponent system were drawn. The research results indicate that hydroxyl manganese chloride has been produced in laboratory and is in favor of the solid-liquid separation at high temperature.

Purification of Inositol. Studies on the Phase Equilibrium of the System C 6H 12 O 6 NH 4Cl C 2H 5OH H 2O(C 2H 5 OH/H 2O =0.90, by wt ) at 35℃

The solubilities and the refractive indices of the saturated solution in the system C 6H 12 O 6 NH 4Cl C 2H 5OH-H 2O ( C 2H 5OH / H 2O=0.90, by wt ) at 35℃ have been determined. The isotherms and refractive indices of the system at 35℃ consist of 2 branches, corresponding to C 6H 12 O 6( H 2O and NH 4Cl. The composition of eutectic solution is C 6H 12 O 6: 4.40 %, NH 4Cl: 13.86 %, C 2H 5OH: 38.88 %.

Soft Sensor for Ammonia Concentration at the Ammonia Converter Outlet Based on an Improved Group Search Optimization and BP Neural Network

The ammonia synthesis reactor is the core unit in the whole ammonia synthesis production. The ammonia concentration at the ammonia converter outlet is a significant process variable, which reflects directly the production efficiency. However, it is hard to be measured reliably online in real applications. In this paper, a soft sensor based on BP neural network (BPNN) is applied to estimate the ammonia concentration. A modified group search optimization with nearest neighborhood (GSO-NH) is proposed to optimize the weights and thresholds of BPNN. GSO-NH is integrated with BPNN to build a soft sensor model. Finally, the soft sensor model based on BPNN and GSO-NH (GSO-NH-NN) is used to infer the outlet ammonia concentration in a real-world application. Three other modeling methods are applied for comparison with GSO-NH-NN. The results show that the soft sensor based on GSO-NH-NN has a good prediction performance with high accuracy. Moreover, the GSO-NH-NN also provides good generalization ability to other modeling problems in ammonia synthesis production.

Nitrification intensity and ammonia-oxidizing bacteria and archaea in different wetland plant rhizosphere soils

In order to explore the nitrogen removal process in constructed wetlands(CW s),the moisture,ammonia nitrogen(NH4+-N),nitrate nitrogen(NO3"-N)and nitrification intensity in three wetland plant rhizosphere soils(Acorns calamus,Typha orientalis,Iris pseudacorus)were investigated at a relatively normal temperature range of15to25The relative abundance of ammonia-oxidizing bacteria(AOB)and ammonia-oxidizing archaea(AOA)were also achieved using fluorescence in situ hybridization(FISH).It is found that T.orientalis achieves the highest nitrification intensity of2.03m g(h?kg)while the second is I.pseudacorrs(1.74m g/(h?kg)),and followed by A.calamus(1.65m g/(h?kg))throughout the experiment.FISH reveals that the abundance of bacteria(1010g_1wet soil)is higher than that of archaea(109g_1wet soil),and AOBare the dominant bacteria in the ammonia oxidation process.The abundance of AOB in te rhizosphere soils from high to low T.orientalis(1.88x1010g"1),I pseudacorus(1.23x1010g1),A.calamus(5.07x109g"1)while the abundance of AOA from high to low ae I.pseudacorus(4.00x109g1),A.calamus(3.52x109g"1),T.orientalis(3.48x109g"1).The study provides valuable evidence of plant selection for nitrogen removal in CWs.

Effect of substrate concentration on stability of anammox biofilm reactors

Ammonium and nitrite are two substrates of anammox bacteria, but they are also inhibitors under high concentrations. The performance of two anaerobic ammonium-oxidizing (anammox) upflow biofilm (UBF) reactors was investigated. The results show that anammox UBFs become unstable under nitrogen loading rate (NLR) applied higher than 1.0 g/(L·d). The consumptions of acidity in the anammox reaction lead to the increase of pH, which is as high as 8.70-9.05. Free nitrous acid concentration is accompanied to be lower than the affinity constant of anammox bacteria, and then starvation effect appears. Moreover, free ammonia concentration increases to 57-178 mg/L, resulting in inhibitory effect on the anammox bacteria. Both negative effects contribute to the instability of the anammox bioreactors.

Thermodynamics of solubility of Cu_2(OH)_2CO_3 in ammonia-ammonium chloride-ethylenediamine(En)-water system

In order to decrease the evaporating rate of ammonia and increase the solubility of copper in the solution,ethylenediamine was added into the ammonia-ammonium chloride system to leach the copper-containing oxide ores.The thermodynamic model was constructed and the solubility of malachite Cu2(OH)2CO3 in the ammonia-ammonium chloride-ethylenediamine(En)-water system was calculated using the exponential computation method based on both mass balance and charge balance.It is found that the solubility of copper can be increased and the free ammonia concentration can be decreased by submitting partial ammonia with ethylenediamine.The lower free ammonia concentration in the solution is a guarantee to the lower evaporating rate of ammonia.The conditions of malachite Cu2(OH)2CO3 converting to atacamite Cu(OH)1.5Cl0.5 were also studied.A group of experiments were designed to validate the veracity of the results of the thermodynamic calculation.It is found that the thermodynamic model is reliable and it can guide the leaching process.

Indoleamine 2,3-dioxygenase (IDO) is essential for dendritic cell activation and chemotactic responsiveness to chemokines

Indoleamine 2, 3-dioxygenase (IDO) is a rate-limiting enzyme for the tryptophan catabolism. In human and murine cells, IDO inhibits antigen-specific T cell proliferation in vitro and suppresses T cell responses to fetal alloantigens during murine pregnancy. In mice, IDO expression is an inducible feature of specific subsets of dendritic cells (DCs), and is important for T cell regulatory properties. However, the effect of IDO and tryptophan deprivation on DC func- tions remains unknown. We report here that when tryptophan utilization was prevented by a pharmacological inhibitor of IDO, 1-methyl tryptophan (1MT), DC activation induced by pathogenic stimulus lipopolysaccharide (LPS) or inflam- matory cytokine TNF-α was inhibited both phenotypically and functionally. Such an effect was less remarkable when DC was stimulated by a physiological stimulus, CD40 ligand. Tryptophan deprivation during DC activation also regu- lated the expression of CCR5 and CXCR4, as well as DC responsiveness to chemokines. These results suggest that tryptophan usage in the microenvironment is essential for DC maturation, and may also play a role in the regulation of DC migratory behaviors.

The Short-term Effects of Temperature and Free Ammonia on Ammonium Oxidization in Granular and Floccular Nitrifying System

The short-term effects of temperature and free ammonia (FA) on ammonium oxidization were investigated in this study by operating several batch tests with two different partial nitrification aggregates, formed as either granules or flocs. The results showed that the rate of ammonium oxidation in both cultures increased significantly as temperature increased from 10 to 30 °C. The specific ammonium oxidation rate with the granules was 2-3 times higher than that with flocs at the same temperature. Nitrification at various FA concentrations and temperatures combination exhibited obvious inhibition in ammonium oxidation rate when FA was 90 mg·L 1 and tempera- ture dropped to 10 °C in the two systems. However, the increase in substrate oxidation rate of ammonia at 30 °C was observed. The results suggested that higher reaction temperature was helpful to reduce the toxicity of FA. Granules appeared to be more tolerant to FA attributed to the much fraction of ammonia oxidizing bacteria (AOB) and higher resistance to the transfer of ammonia into the bacterial aggregates, whereas in the floc system, the bacteria distributed throughout the entire aggregate. These results may contribute to the applicability of the nitrifying granules in wastewater treatment operated at high ammonium concentration.

A Two-stage pH and Temperature Control with Substrate Feeding Strategy for Production of Gamma-aminobutyric Acid by Lactobacillus brevis CGMCC 1306

Methods to optimize the production of gamma-aminobutyric acid （GABA） by Lactobacillus brevis CGMCC 1306 were investigated. Results indicated that cell growth was maximal at pH 5.0, while pH 4.5 was pref-erable to GABA formation. The optimal temperature for cell growth （35 °C） was lower than that for GABA forma-tion （40 °C）. In a two-stage pH and temperature control fermentation, cultures were maintained at pH 5.0 and 35 °C for 32 h, then adjusted to pH 4.5 and 40 °C, GABA production increased remarkably and reached 474.79 mmol·L-1 at 72 h, while it was 398.63 mmol·L-1 with one stage pH and temperature control process, in which cultivation con-ditions were constantly controlled at pH 5.0 and 35 °C. In order to avoid the inhibition of cell growth at higher L-monosodium glutamate （L-MSG） concentrations, the two-stage control fermentation with substrate feeding strat-egy was applied to GABA production, with 106.87 mmol （20 g） L-MSG supplemented into the shaking-flask at 32 h and 56 h post-inoculation separately. The GABA concentration reached 526.33 mmol·L-1 at 72 h with the fer-mentation volume increased by 38%. These results will provide primary data to realize large-scale production of GABA by L. brevis CGMCC 1306.

Crystallographic and Morphological Sensitivity of N_(2) Activation over Ruthenium

Ruthenium(Ru)serves as a promising catalyst for ammonia synthesis via the Haber-Bosch process,identification of the structure sensitivity to improve the activity of Ru is important but not fully explored yet.We present here density functional theory calculations combined with microkinetic simulations on nitrogen molecule activation,a crucial step in ammonia synthesis,over a variety of hexagonal close-packed(hcp)and face-center cubic(fcc)Ru facets.Hcp{2130}facet exhibits the highest activity toward N_(2) dissociation in hcp Ru,followed by the(0001)monatomic step sites.The other hcp Ru facets have N_(2) dissociation rates at least three orders lower.Fcc{211}facet shows the best performance for N_(2) activation in fcc Ru,followed by{311},which indicates stepped surfaces make great contributions to the overall reactivity.Although hcp Ru{2130}facet and(0001)monatomic step sites have lower or comparable activation barriers compared with fcc Ru{211}facet,fcc Ru is proposed to be more active than hcp Ru for N_(2) conversion due to the exposure of the more favorable active sites over step surfaces in fcc Ru.This work provides new insights into the crystal structure sensitivity of N_(2) activation for mechanistic understanding and rational design of ammonia synthesis over Ru catalysts.

Hyperhomocysteinemia independently causes and promotes atherosclerosis in LDL receptor-deficient mice

Background Hyperhomocysteine is an independent risk factor of coronary heart disease （CHD）. However, whether hyperhomocys teine affects the progression of atherosclerosis is unclear. In the present study, we examined the effect of hyperhomocysteine on the forma tion of atherosclerosis in low-density lipoprotein receptor-deficient （LDLr ） mice. Methods Forty-eight 7-week-old LDLr/ mice were assigned to the following groups： mice fed a standard rodent diet （control group）, mice fed a high-methionine diet （high-methionine group）, mice fed a high-fat diet （high-fat group）, and mice fed a diet high in both methionine and fat （high-methionine and high-fat group）. At the age of 19, 23, and 27 weeks, four mice at each interval in every group were sacrificed. Results At the end of the study, mice did not show atherosclerotic lesions in the aortic sinus and aortic surface until 27 weeks old in the control group. However, atherosclerotic lesions developed in the other three groups at 19 weeks. The amount of atherosclerotic lesions on the aortic surface was lower in the high-methionine group than in the high-fat group （P 〈 0.001）. Atherosclerotic lesions on the aortic surface in the high-methionine and high-fat group were the most severe. The mean area of atherosclerotic lesions in the aortic sinus compared with atherosclerotic lesions on the aortic surface was lower in the high-methionine group than in the high-fat group （P 〈 0.001）. Atherosclerotic lesions in the aortic sinus in the high-methionine and high-fat group were the most severe. Conclusions Homocysteinemia accelerates atherosclerotic lesions and induces early atherosclerosis independently in LDLrmice. Reducing the level of homocysteinemia may be beneficial for prevention and treatment of CHD.

Glutamate dehydrogenase and Na^+-K^+ ATPase expression and growth response of Litopenaeus vannamei to different salinities and dietary protein levels

Improvement in the osmoregulation capacity via nutritional supplies is vitally important in shrimp aquaculture.The effects of dietary protein levels on the osmoregulation capacity of the Pacific white shrimp(L.vannamei) were investigated.This involved an examination of growth performance,glutamate dehydrogenase(GDH) and Na+-K+ ATPase mRNA expression,,and GDH activity in muscles and gills.Three experimental diets were formulated,containing 25%,40%,and 50% dietary protein,and fed to the shrimp at a salinity of 25.After 20 days,no significant difference was observed in weight gain,though GDH and Na+-K+ ATPase gene expression and GDH activity increased with higher dietary protein levels.Subsequently,shrimp fed diets with 25% and 50% dietary protein were transferred into tanks with salinities of 38 and 5,respectively,and sampled at weeks 1 and 2.Shrimp fed with 40% protein at 25 in salinity(optimal conditions) were used as a control.Regardless of the salinities,shrimp fed with 50% dietary protein had significantly higher growth performance than other diets;no significant differences were found in comparison with the control.Shrimp fed with 25% dietary protein and maintained at salinities of 38 and 5 had significantly lower weight gain values after 2 weeks.Ambient salinity change also stimulated the hepatosomatic index,which increased in the first week and then recovered to a relatively normal level,as in the control,after 2 weeks.These findings indicate that in white shrimp,the specific protein nutrient and energy demands related to ambient salinity change are associated with protein metabolism.Increased dietary protein level could improve the osmoregulation capacity of L.vannamei with more energy resources allocated to GDH activity and expression.

Computational screening of O‐functional MXenes for electrocatalytic ammonia synthesis

The nitrogen reduction reaction(NRR)using new and efficient electrocatalysts is a promising al‐ternative to the traditional Haber‐Bosch process.Nevertheless,it remains a challenge to design efficient catalysts with improved catalytic performance.Herein,various O‐functional MXenes were investigated as NRR catalysts by a combination of density functional theory calculations and least absolute shrinkage and selection operator(LASSO)regression.Nb_(3)C_(2)O_(X) has been regarded as a promising catalyst for the NRR because of its stability,activity,and selectivity.The poten‐tial‐determining step is*NH_(2) hydrogenation to*NH3 with a limiting potential of-0.45 V.Further‐more,via LASSO regression,the descriptors and equations fitting the relationship between the properties of O‐functional MXenes and NRR activity have been proposed.This work not only pro‐vides a rational design strategy for catalysts but also provides machine learning data for further investigation.

Synthesis and Study of Glutamine Acid Containing Citrates

Terms of synthesis were defined for the creation of new generation chelate fertilizers and for their experimental testing. Glutamine acid and citric acid containing chelate citrates of the general formulae M.gI.HL＇nHO were synthesized, where, M = Mn, Zn, Fe, Co, Cu; n = 0; 1; 1.5; gl-glutamine acid; HL-citric acid anion. Identity and composition of synthesized compounds were determined by microelemental analysis, melting temperature and X-ray diffraction analysis. X-ray diffraction analysis of the compounds and glutamine acid and citric acid （H4L） was used to determine their crystalline structure and roentgen-amorphous and iso-structural orders. Their solubility was studied in various solvents.

DFT Study of Geometrical and Vibrational Features of Sulfur Containing Amino Acids in Hydrated Media： L-Cysteine and L-Methionine

Geometry optimization at the B3LYP/6-31＋＋G＊ level of theory has been undertaken on clusters containing L-Met （L-methionine） or L-Cys （L-cysteine） surrounded by eight water molecules. The comparison of the structural parameters of L-Met and L-Cys with X-ray experimental values is in good agreement within 4.8%. This result shows that the privileged positions of water molecules and the possible hydrogen bonding network formed around the backbone of both AAs （amino acids） are adequate. Subsequent calculations of the harmonic vibrational modes followed by a post-processing treatment enable us to assign the vibrational modes of L-Met and L-Cys surrounded explicitly by eight water molecules. The frequencies of the assigned modes are in good agreement with available IR （infra red） and Raman values within 5%.

A comparable study of microbial community in aerobic granular sludge and activated sludge for wastewater treatment

Effect of ammonia at different concentrations on aerobic granular sludge and activated sludge was investigated in this study. Meanwhile, bacterial diversity variation and ammonia oxidizing bacterium （AOB） quantification within both kinds of sludge were monitored by terminal restriction fragment length polymorphism （T-RFLP） and real-time PCR （RT-PCR） technique, respectively. The results showed that the COD removal of both kinds of sludge changed slightly when the ammonia removal efficiency decreased gradually with the ammonia concentration increased from 100 mg L^-1 to 500 mg L^-1 Furthermore, activated sludge demonstrated higher ammonia removal ability than that of aerobic granular sludge （10%- 16%）. As revealed by T-RFLP, activated sludge was of higher ammonia removal ability and more abounding bacterial diversity than that of aerobic granular sludge, suggesting that the bacterial diversity was probably relevant to the ammonia removal. The RT-PCR results indicated that the AOB population size of activated sludge and aerobic granular sludge were 2.80× 10^4-3.44× 10^4cells （g dried sludge）^-1 and 7.83×10^4-1.18×10^5cells （g dried sludge）^-1, respectively. There is no obvious positive correlation between the ammonia removal ability and number of AOB in both kinds of sludge.

Effects of Silver Nanoparticles on Soil Ammonia-Oxidizing Microorganisms Under Temperatures of 25 and 5℃

The excellent bactericidal performance of silver nanoparticles （Ag NPs） has led to their wide applications, resulting in increasing concerns about their potential environmental impacts. This study evaluated the influences of different concentrations of Ag NPs （0, 1, 10, and 100 μg g^-1 dry soil） on the ammonia-oxidizing microorganisms in soil at cultivation temperatures of 25 and 5 ℃ for 37 d. The results showed that 1μg g^-1 dry soil of Ag NPs had no acute effects on the ammonia-oxidizing microorganisms. However, 10 and 100μg g^-1 dry soil of Ag NPs levels were found to significantly inhibit the activities of soil nitrification, with a decrease of 69.89% and 94.55%, respectively, at 25 ℃ and 61.65% and 83.79%, respectively, at 5℃ compared to the control （0 μg g^-1 dry soil of Ag NPs）. These levels of Ag NPs also obviously decreased soil urease activity from about 380.47 ± 0.07 （at 5℃） and 529.76 ± 13.44 （at 25℃） mg N g^-1 dry soil d^-1 to 61.70 ± 2.97 and 68.29 ± 8.22 mg N g^-1 dry soil d^-1, respectively, after 37 d of cultivation. Quantitative polymerase chain reaction showed the abundance of ammonia-oxidizing archaea and bacteria. For the same exposure time, the effects of Ag NPs on the activities of ammonia-oxidizing microorganisms and urease decreased with decreasing temperature. The threshold concentration of Ag NPs that induced negative effects on ammonia-oxidizing microorganisms was higher at 5 -C than at 25 -C. Therefore, the temperature has a major impact on the toxicity of Ag NPs to ammonia-oxidizing microorganisms and on the urease activity, with toxicity being reduced with decreasing temperature.