Solidification mechanism of the sediment formed by particle settling – Analysis of the formation of the solidified layer

In various industrial processes, it is important to prevent the solidification in order to maintain the slurry properties. In order to predict the formation of the sediment and solidified layer, the gravitational sedimentation behavior of the slurries obtained by changing the slurry pH and the time change in the formation of sediment were observed. As a result, we can predict the solidification time and precisely predict the formation of the solidified layer and determine suitable conditions for the storage of slurries.     

Experimental study about the agglomeration behavior in slurry prepared by adding excess polyelectrolyte dispersant

In our previous paper we found that the particles in the slurry can agglomerate by adding larger amount of polyelectrolyte dispersant compared to that needed to attain well dispersion. Thus, the dependency of initial particle concentration on the agglomeration and its mechanism in slurry prepared by adding excess polyelectrolytes was experimentally discussed. It was shown that agglomeration behavior strongly depends on the additive amount of polyelectrolytes, not on the polyelectrolyte concentration in the solution. It was also found that the dominant factor of agglomeration in slurry prepared by adding extra polyelectrolytes should be the compression of the electrical double layer by the increased counter ion concentration, not by the so called depletion effect or by pH change. Interestingly, the final sediment had a relatively high packing fraction and good flowability in the case of the agglomerated slurry with extra polyelectrolytes compared to that of the agglomerated slurry with an additional NaCl solution.     

Development of a novel slurry condensation method by applying dispersant instead of flocculant

A novel filtration technique has been developed by adding the dispersant instead of the flocculant used in conventional solid–liquid separation technique. Slurries were prepared by controlling the pH values in order to control the dispersion and flocculation degree of particles. The prepared slurries were condensed by gravitational settling condensation or by pressure filtration condensation. On the gravitational settling condensation for the flocculated slurry, the cake was formed on the filter media and then the filtration could not be continued unless the formed cake was excreted by a mechanical hand-scraping device. In addition, the volumetric concentration of the condensate obtained from the flocculated slurry was at most 15 vol.%. On the other hand, the condensate obtained from the dispersed slurry still possessed fluidity when the concentration reached almost 40 vol.%, therefore we could collect the condensate without any hand-scraping devices. Furthermore, cake formation did not occur for the dispersed slurry, suggesting that the continuous filtration condensation is possible.     

低温高强度堵剂T201的研制与应用

吐哈油田储层低渗 ,微裂缝相对较发育 ,地温低 ,长期注水后油井温度在 70℃左右 ,注水井温度 5 0～ 6 0℃。以成胶时间和凝胶粘度为主要评价指标 ,从HPAM /多元酚 /醛体系出发 ,通过组分及其用量的筛选 ,得到了低温堵剂T2 0 1的基本配方如下 :0 .2 %～ 0 .5 %HPAM 0 .0 3%～ 0 .0 4多元酚 0 .2 %醛 0 .4 %～ 0 .4 5 %延缓稳定剂亚硫酸氢盐 0 .0 6 %～ 0 .0 8%催化剂铵盐 ;HPAM分子量为 6 .0× 10 6～ 8.0× 10 6,水解度 15 %～ 2 0 %。 0 .5 %HPAM的堵剂溶液室温、170s-1粘度为 2 2mPa·s,在 4 0～ 70℃下成胶时间为 17～ 5h ,形成的凝胶室温、1.5s-1粘度为 4 7～ 14Pa·s。T2 0 1更适合低温油藏。 2 0 0 1年实施的 12井次注水井调剖作业 ,成功率 10 0 % ,有效率 90 %。在施工中采取了如下工艺作法 :按井况调整堵剂配方 ;交联剂略过量 ;用低浓度聚合物溶液将注入的堵剂替至半径 2～ 3m处 ;控制注入压力。详细介绍了 4口注水井调剖施工情况及结果。图 4表 7参 1。     

Methylenetetrahydrofolate reductase gene polymorphism and ischemic stroke in Japanese

Hyperhomocyst(e)inemia has been identified as an independent risk factor for atherosclerotic and thromboembolic diseases such as coronary artery disease, cerebral artery disease, and venous thrombosis. Recently, the alanine/valine (A/V) gene polymorphism of 5,10-methylenetetrahydrofolate reductase (MTHFR), one of the key enzymes that catalyzes the remethylation of homocysteine, was reported. The VV genotype is correlated with increased plasma homocyst(e)ine levels as a result of the reduced activity and increased thermolability of this enzyme. In this study, we examined the association between the V allele of the MTHFR gene and ischemic stroke in an elderly Japanese population. The diagnosis of cerebral infarction of all study patients was confirmed by CT of the brain. The MTHFR genotype was analyzed by polymerase chain reaction followed by HinfI digestion. In 256 stroke patients and 325 control subjects, the frequencies of the V allele were 0.45 and 0.32, respectively. The odds ratios and 95% confidence intervals adjusted for the other risk factors were, respectively, 1.51 (1.02 to 2.23) for the AV genotype and 3.35 (1.94 to 5.77) for the VV genotype compared with the AA genotype. Both of these effects were statistically significant (P=0.041 and P<0.001, respectively). In patients with multiple infarcts in particular, the allele frequency of the V mutation was 0.56, and the association between the V allele and stroke was highly significant. Plasma homocyst(e)ine levels were significantly higher in patients with the VV genotype than in patients with the AA or AV genotype, especially those with low plasma folate levels. The V allele of the MTHFR gene was significantly associated with cerebral infarction in an elderly Japanese population in a codominant manner. The VV genotype may contribute to risk for ischemic stroke through a predisposition to increased plasma homocyst(e)ine levels, and dietary folate supplementation may be of benefit, particularly to patients with this genotype.     

Phenotypical heterogeneity of CD4+CD8+ double-positive chronic T lymphoid leukemia

BACKGROUND: One of the most controversial areas in patient selection and donor allocation is the high-risk patient. Risk factors for mortality and major infectious morbidity were prospectively analyzed in consecutive United States veterans undergoing liver transplantation under primary tacrolimus-based immunosuppression. METHODS: Twenty-eight pre-liver transplant, operative, and posttransplant risk factors were examined univariately and multivariately in 140 consecutive liver transplants in 130 veterans (98% male; mean age, 47.3 years). RESULTS: Eighty-two percent of the patients had postnecrotic cirrhosis due to viral hepatitis or ethanol (20% ethanol alone), and only 12% had cholestatic liver disease. Ninety-eight percent of the patients were hospitalized at the time of transplantation (66% United Network for Organ Sharing [UNOS] 2, 32% UNOS 1). Major bacterial infection, posttransplant dialysis, additional immunosuppression, readmission to intensive care unit (P=0.0001 for all), major fungal infection, posttransplant abdominal surgery, posttransplant intensive care unit stay length of stay (P<0.005 for all), donor age, pretransplant dialysis, and creatinine (P<0.05 for all) were significantly associated with mortality by univariate analysis. Underlying liver disease, cytomegalovirus infection and disease, portal vein thrombosis, UNOS status, Childs-Pugh score, patient age, pretransplant bilirubin, ischemia time, and operative blood loss were not significant predictors of mortality. Patients with hepatitis C (HCV) and recurrent HCV had a trend towards higher mortality (P=0.18). By multivariate analysis, donor age, any major infection, additional immunosuppression, posttransplant dialysis, and subsequent transplantation were significant independent predictors of mortality (P<0.05). Major infectious morbidity was associated with HCV recurrence (P=0.003), posttransplant dialysis (P=0.0001), pretransplant creatinine, donor age, median blood loss, intensive care unit length of stay, additional immunosuppression, and biopsy-proven rejection (P<0.05 for all). By multivariate analysis, intensive care unit length of stay and additional immunosuppression were significant independent predictors of infectious morbidity (P<0.03). HCV recurrence was of borderline significance (P=0.07). CONCLUSIONS: Biologic and physiologic parameters appear to be more powerful predictors of mortality and morbidity after liver transplantation. Both donor and recipient variables need to be considered for early and late outcome analysis and risk assessment modeling.     

Influence of synthesis conditions on NO oxidation and NOx storage performances of La0.7Sr0.3MnO3 perovskite-type catalyst in lean-burn atmospheres

Synthesis conditions of catalysts can significantly affect catalytic activities for a certain reaction. Here, a series of the La_0.7Sr_0.3MnO₃ perovskite-type catalysts was prepared by the sol–gel method under the different synthesis conditions. The faster calefactive velocities during calcination of the xerogel precursors would produce a lot of the impurities and cause the dropped amount of the excessive oxygen in perovskite, as well as the aggregated particles and the decreased surface areas; the higher calcination temperature would sinter the perovskite phases seriously; and the initial pH value of the precursor solution would greatly affect the morphology of the catalysts including the shape and the size, which directly linked to their NO_x storage capacity. Moreover, our findings revealed that the NO oxidation ability was determined by the amount of the excessive oxygen species in the perovskite. Here, the optimum synthesis conditions were achieved with the calcination temperature of 700 °C, the calefactive velocity of 2 °C min⁻¹, and the precursor solution of pH = 8. This catalyst presented the best performances for the NO oxidization and NO_x storage, i.e. the NO-to-NO₂ conversion of 70.2% and the NO_x storage capacity of 170.4 μmol g⁻¹.     

Influence of Granule Character and Compaction on the Mechanical Properties of Sintered Silicon Nitride

The influence of granule character and compaction on the mechanical properties of sintered silicon nitride was studied as a function of the pH of the spray-dry slurry. The character and the compaction behavior of the spray-dried silicon nitride granules considerably affect the mechanical properties of the sintered body. Dense and hard granules resulting from a well-dispersed slurry retained their shape in green compacts and caused numerous pore defects in sintered body. Decreasing the slurry pH to a certain value (e.g., 7.9) caused slurry flocculation and reduced the granule density as well as the diametral compression strength of the granules. Sintered bodies fabricated with these weak granules contained fewer defects and showed remarkable strength increase.     

Catalytically active supercritical fluid to accelerate methanol synthesis

Supercritical phase 2-butanol significantly increased the conversion of methanol synthesis from syngas not only by the conventional promotion effect of supercritical fluid but also by the catalytic effect of 2-butanol solvent itself, breaking through the thermodynamic limitation of this reaction effectively.