市政污泥干化焚烧处理技术探究

市政污泥含有重金属、化学污染物、有机质以及多种病原体,常规处理方式的缺点为成本高、水资源消耗大,干化焚烧工艺经过脱水和高温焚烧两道工序,能够大幅降低污泥中污染物的含量。为了探究该工艺技术的应用方法,研究过程分别开展干化实验和焚烧实验,确定含水率、有机质含量、干化温度的合理取值范围,对焚烧残渣中的重金属元素进行分析,进而在此基础上设计出干化焚烧处理工艺系统。经过实测,锌、铅、镍、砼、总铬、六价铬的浓度分别为0.02、0.01、0.005、0.01、0.01、0.003 mg/L,远低于国家标准规定的限值,说明系统在残渣处理方面表现出较高的环保性。此外,针对烟气排放的检测结果显示:颗粒物、SO_(x)、NO_(x)、CO、二噁英的排放浓度分别为9.4、0.7、100.6、5.6、0.04 mg/Nm 3,不仅低于国家标准,同时也低于欧盟标准,达到了优异的控制效果,表明系统在烟气排放方面具有良好的环保性能。

Characterization of pancreatic stem cells derived from adult human pancreas ducts by fluorescence activated cell sorting

AIM： To isolate putative pancreatic stem cells （PSCs） from human adult tissues of pancreas duct using serumfree, conditioned medium. The characterization of surface phenotype of these PSCs was analyzed by flow cytometry. The potential for pancreatic lineage and the capability of β-cell differentiation in these PSCs were evaluated as well. METHODS： By using serum-free medium supplemented with essential growth factors, we attempted to isolate the putative PSCs which has been reported to express nestin and pdx-1. The MatrigelTM was employed to evaluate the differential capacity of isolated cells. Dithizone staining, insulin content/secretion measurement, and immunohistochemistry staining were used to monitor the differentiation. Fluorescence activated cell sorting （FACS） was used to detect the phenotypic markers of putative PSCs. RESULTS： A monolayer of spindle-like cells was cultivated. The putative PSCs expressed pdx-1 and nestin. They were also able to differentiate into insulin-, glucagon-, and somatostatin-positive cells. The spectrum of phenotypic markers in PSCs was investigated; a similarity was revealed when using human bone marrow-derived stem cells as the comparative experiment, such as CD29, CD44, CD49, CD50, CD51, CD62E, PDGFR-α, CD73 （SH2）, CD81, CD105（SH3）. CONCLUSION： In this study, we successfully isolated PSCs from adult human pancreatic duct by using serumfree medium. These PSCs not only expressed nestin and pdx-1 but also exhibited markers attributable to mesenchymal stem cells. Although work is needed to elucidate the role of these cells, the application of these PSCs might be therapeutic strategies for diabetes mellitus.

Skeletal myogenesis by human embryonic stem cells

We have examined the myogenic potential of human embryonic stem （hES） cells in a xeno-transplantation animal model. Here we show that precursors differentiated from hES cells can undergo myogenesis in an adult environment and give rise to a range of cell types in the myogenic lineage. This study provides direct evidences that hES cells can regenerate both muscle and satellite cells in vivo and are another promising cell type for treating muscle degenerative disorders in addition to other myogenic cell types.

Experimental and Theoretical Analysis of the Impinging Stream Drying

The experiments of one-stage semi-circular and two-stage semi-circular impinging stream drying as well as the vertical and semi-circular combined impinging stream drying were carried out. The velocity distribution and the mean residence time of particles, and the influence of various factors on drying characteristics were studied. A mathematical model of granular material drying in a semi-circular impinging stream dryer was proposed, in which the flow characteristics as well as the heat and mass transfer mechanisms were considered. Reasonable numerical methods were used to solve the equations. Under various conditions, the calculated results agree well with the experimental data. The unsteady-state drying dynamic equation, as well as the variations of drying rate and moisture content versus time were obtained. The results indicate that constant drying rate period does not exist in a semi-circular impinging stream dryer. Appropriate semi-circular stage number and curvature radius, flow-rate ratio, air velocity, and higher inlet air temperature should be used for enhancing the drying process.

Effects of soil moisture and soil depth on nitrogen mineralization process under Mongolian pine plantations in Zhanggutai sandy land, P. R. China

The rates of soil N mineralization at soil depths of 0-15, 15-30, 30-45 and45-60 cm and moisture regimes were measured at three sand-fixation plantations of Pinus sylvestrisvar. mongolica by laboratory aerobic incubation method. The results showed that average rates ofsoil net N-mineralization across soil depth varied from 1.06 to 7.52 mg · kg^(-1)·month^(-1) atsoil depths from 0 to 60 cm. Statistical analyses indicated that the effects of different soildepths, moistures and their interactions on net N-mineralization rates were significant (P < 0.05).The net N-mineralization rates significantly decreased with increasing soil depths and at depth 0-15cm accounted for 60.52% of that at depth of 0-60 cm. There was no difference in soil netN-mineralization rates between half and fully-saturated water treatments, however these rates weresubstantially higher than that without water treatment (P < 0.05). The factors influencing Nmineralization process have to be studied further in these semiarid pine ecosystems.

Effects of Guiyuanfang and autologous transplantation of bone marrow stem cells on rats with liver fibrosis

AIM: To investigate the therapeutic effects of Guiyuanfang and bone marrow stem cells (BMSCs) on rats with liver fibrosis.METHODS: Liver fibrosis model was induced by carbon tetrachloride, ethanol, high lipid and assessed biochemically and histologically. Liver function and hydroxyproline contents of liver tissue were determined.Serum hyaluronic acid (HA) level and procollagen Ⅲ level were performed by radioimmunoassay. The VG staining was used to evaluate the collagen deposit in the liver.Immunohistochemical SABC methods were used to detect transplanted BMSCs and expression of urokinase plasminogen activator (uPA).RESULTS: Serum transaminase level and liver fibrosis in rats were markedly reduced by Guiyuanfang and BMSCs. HA level and procollagen Ⅲ level were also reduced obviously,compared to model rats (HA: 47.18±10.97 ng/mL,48.96±14.79 ng/mL; PCⅢ: 22.48±5.46 ng/mL, 26.90±3.35ng/mL; P＜0.05).Hydroxyproline contents of liver tissue in both BMSCs group and Guiyuanfang group were far lower than that of model group (1 227.2±43.1 μg/g liver tissue, 1390.8±156.3 μg/g liver tissue; P＜0.01). After treatment fibrosis scores were also reduced. Both Guiyuanfang and BMSCs could increase the expression of uPA. The transplanted BMSCs could engraft, survive, and proliferate in the liver.CONCLUSION: Guiyuanfang protects against liver fibrosis.Transplanted BMSCs may engraft, survive, and proliferate in the fibrosis livers indefinitely. Guiyuanfang may synergize with BMSCs to improve recovery from liver fibrosis.

Xeno-free derivation and culture of human embryonic stem cells： current status, problems and challenges

Human embryonic stem cells （hESC） not only hold great promise for the treatment of degenerative diseases but also provide a valuable tool for developmental studies. However, the clinical applications of hESC are at present limited by xeno-contamination during the in vitro derivation and propagation of these cells. In this review, we summarize the current methodologies for the derivation and the propagation of hESC in conditions that will eventually enable the generation of clinical-grade cells for future therapeutic applications.

An Experimental Investigation of Agglomeration with One and Two Nozzle Atomisation

Water-droplet size and velocity measurements were taken throughout two different sprays produced by a single nozzle and two nozzles pointed towards each other. The aim of this investigation was to understand the manner in which the motion of the droplets in a spray leads to agglomeration of these droplets. It appears that the inertia of the droplets plays an important role in the redistribution of droplets throughout a spray. Larger droplets tend to concentrate at the outer portions of the spray, because they are able to maintain their radial momentum farther downstream of a nozzle, while the smaller droplets follow the airflow more closely and thus collect in the core of the spray. Agglomeration can result from both turbulent collisions and collisions due to the relative velocities of the droplets. The difference between the agglomeration rates in the sprays from a single nozzle and two-nozzles pointed towards each other was difficult to resolve in these experiments, although the results suggest that the outer portions of both sprays should be investigated more closely for evidence of agglomeration.

Progress of cellular dedifferentiation research

Differentiation, the stepwise specialization of cells, and transdifferentiation, the apparent switching of one cell type into another, capture much of the stem cell spotlight. But dedifferentiation, the developmental reversal of a cell before it reinvents itself, is an important process too. In multicellular organisms, cellular dedifferentiation is the major process underlying totipotency, regeneration and formation of new stem cell lineages. In humans, dedifferentiation is often associated with carcinogenesis. The study of cellular dedifferentiation in animals, particularly early events related to cell fate-switch and determination, is limited by the lack of a suitable,convenient experimental system. The classic example of dedifferentiation is limb and tail regeneration in urodele amphibians, such as salamanders. Recently, several investigators have shown that certain mammalian cell types can be induced to dedifferentiate to progenitor cells when stimulated with the appropriate signals or materials. These discoveries open the possibility that researchers might enhance the endogenous regenerative capacity of mammals by inducing cellular dedifferentiation in vivo.