我国学前教育政策研究的回眸与展望:价值取向、研究范式与核心主题

在我国学前教育事业不断走向科学化和规范化的过程中,学前教育政策研究发挥了非常重要的作用。回顾我国学前教育政策研究的历史,可以发现相关研究者在价值取向上始终坚持学前教育政策研究应呼应国家重大政策、服务时代与社会变革需求、关注事业发展中的关键问题,体现了对公平和质量的持续求索,日益关注弱势群体及精准扶贫,并从宏观探讨逐渐转向对关键政策点的研究,重视多元利益主体的诉求。在研究范式上,我国学前教育政策研究经历了从结构功能主义到批判性分析范式、从理论思辨到实证研究的转向,实现了多元研究范式的并存和互补,研究视野随之逐渐开阔,并积极引入了跨学科视角。学前教育管理与办园体制、财政投入与师资队伍保障机制,学前教育资源扩大与均衡配置、弱势群体扶助、普惠发展,学前教育政策规范、质量保障及立法等是今后一段时期内我国学前教育政策研究的核心主题。

Prevention and Control Technology of Potato Soil-borne Diseases

In recent years,potato soil-borne diseases have occurred severely.The investigation shows that potato Fusarium wilt greatly affects potato yield,leading to a yield reduction rate of 21.8%.Potato powdery scab shows very mild symptoms on potato tuber,basically with no symptoms in some plots,but shows obvious symptoms on the root system.A large number of nodules which are produced on one side of the root system seriously affect water and fertilizer absorption function of the potato root system.Potato tubers expand slowly,leading to small potato tuber,low yield and low commodity rate.The fungus can survive in soil for more than 10 years.Potato soil-borne diseases are harmful and are difficult to control.Susceptible plants can be detected by high definition chromatographic control method and pathogen detection.For prevention and control of potato soil-borne diseases,first of all,disease-resistant varieties should be chosen and virus-free potato seeds are used for sowing.Secondly,metham and dazomet can be used to treat soil in order to prevent and control potato soil-borne diseases.The results showed that the dead seedling rate treated by metham was reduced from 35%to 12.5%compared with the blank control,and the yield was increased by 44.09 kg/ha,with an increase rate of 18.2%.Compared with the blank control,the dead seedling rate treated by dazomet was decreased from 35%to 7.5%,and the yield was increased by 38.10 kg/ha,with an increase rate of 15.7%.The soil treatment received obvious yield increase effect.

Key Technology for Virus-free Seed Potatoes Pre-elite Breeding

[Objectives]To establish a breeding system for pre-elite seed potatoes.[Methods]Shoot-tip seedlings were cultured with different medium,and then transplanted in different substrates.They were sprayed with nutrient solutions of different formulas.Potato minitubers were induced.[Results]The medium of MS+2.0 mg/L 6-BA,1.0 mg/L NAA+3%sugar was preferable for potato shoot tip culture.After virus detection,the virus-free potato seedlings were propagated.The medium composed of vermiculite,peat and perlite(1∶3∶1)was recommended for transplanting potato tissue culture seedlings in greenhouse.The three-dimensional spray method was used to produce pre-elite seed potatoes.The full-amount MS nutrient solution could increase the tuber number per plant to 55.Induction of minitubers is a better breeding technology for pre-elite seed potatoes.The optimal medium screened for induction of potato minitubers was MS+(5-7)mg/L 6-BA,with a dark culture duration of about 20 d.[Conclusions]The breeding technology established is suitable for the two-season cultivation areas in Zaozhuang.

Control of membrane fouling during hyperhaline municipal wastewater treatment using a pilot-scale anoxic/aerobic-membrane bioreactor system

Membrane fouling limits the effects of long-term stable operation of membrane bioreactor （MBR）. Control of membrane fouling can extend the membrane life and reduce water treatment cost effectively. A pilot scale anoxic/aerobic-membrane bioreactor （A/O- MBR, 40 L/hr） was used to treat the hyperhaline municipal sewage from a processing zone of Tianjin, China. Impact factors including mixed liquid sludge suspension （MLSS）, sludge viscosity （Ix）, microorganisms, extracellular polymeric substances （EPS）, aeration intensity and suction/suspended time on membrane fouling and pollution control were studied. The relationships among various factors associated with membrane fouling were analyzed. Results showed that there was a positive correlation among MLSS, sludge viscosity and trans-membrane pressure （TMP）. Considering water treatment efficiency and stable operation of the membrane module, MLSS of 5 g/L was suggested for the process. There was a same trend among EPS, sludge viscosity and TMP. Numbers and species of microorganisms affected membrane fouling. Either too high or too low aeration intensity was not conducive to membrane fouling control. Aeration intensity of 1.0 m3/hr （gas/water ratio of 25：1） is suggested for the process. A long suction time caused a rapid increase in membrane resistance. However, long suspended time cannot prevent the increase of membrane resistance effectively even though a suspended time was necessary for scale off particles from the membrane surface. The suction/suspended time of 12 min/3 rain was selected for the process. The interaction of various environmental factors and operation conditions must be considered synthetically.

Establishment and drug sensitivity evaluation of murine ascites hepatocarcinoma cell line with high lymphatic metastatic potential (Hca-P/L_(6))

In order to provide a sensitive cell line model for investigating the mechanisms underlying the lymphatic metastasis of tumors and the effect of medicine against cells,a new murine ascites hepatocarcinoma cell line with high lymphatic metastatic potential(Hca-P/L_(6))was established and the effect of curcumin on biological behavior of Hca-P/L_(6) was observed.Murine ascites hepatocarcinoma cell strain with low lymphatic metastatic potential(Hca-P)was subcutaneously inoculated into the medioventral line of a mouse 615 and thefirst generation of metastatic tumor cells of inguinal lymph node(Hca-P/L_(1))was obtained.Then,Hca-P/L_(1) was screened by the route of mouse foot pad subcutaneously!lymph node!scale-up culture in vitro!mouse foot pad subcuta-neously forfive times consecutively.The sensitivity of two murine ascites hepatocarcinoma cell lines(Hca-P and Hca-P/L_(6))and two anchorage-dependent human hepato-carcinoma cell lines(SMC7721 and HepG_(2))to curcumin were studied by use of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT)assay after these cells had been pretreated by curcumin at the concentration of 15–240μmol/L for 48 h.After pretreatment by curcumin at the maximum non-cytotoxic dose of 15μmol/L in vitro,the effect of curcumin against cell proliferation of Hca-P and Hca-P/L6 was observed by inverted micro-scope,cell growth curve and cell population doubling time;the effects of curcumin on cell cycles of Hca-P/L6 and Hca-P were studied byflow cytometry(FCM).The results showed Hca-P/L_(6) spreading to the lymph nodes at multiple sites in mice was screened from Hca-P.The lymph node metastatic rate was 100%.Curcumin had significant growth inhibiting effect on both murine ascites and human hepatocarcinoma cell lines in a dose-dependent manner(P<0.05).At concentrations of 30–120μmol/L,curcu-min had more inhibition on murine ascites hepatocarci-noma cell lines than on human anchorage-dependent hepatocarcinoma cell lines.At concentrations of 60–240μmol/L,curcumin had more inhibition on Hca-P/L_(6) with the 50%inhibitory concentration(IC50)of 51.48μmol/L than on Hca-P with IC50 of 90.87μmol/L.After pretreatment by curcumin at the maximum non-cytotoxic dose of 15 mol/L for 7 days,the proliferations of Hca-P/L_(6) and Hca-P were inhibited(P<0.05)in a time-dependent manner(P<0.01)and the population doubling time of Hca-P/L6 and Hca-P was prolonged(P<0.01),and curcumin had more inhibition on Hca-P/L6 than on Hca-P(P<0.05).After pretreatment by 15μmol/L curcumin for 48 h,the morphous of Hca-P/L_(6) was influenced more seriously than that of Hca-P and the cell cycle was redistributed with Hca-P/L6 being blocked in the S phase and Hca-P in the S and G_(2)/M phases.Hca-P/L_(6) was validated to be more sensitive to curcumin than Hca-P.Hca-P/L_(6) is a novel sensitive cell line model for investigating the mechanisms underlying tumor lymphatic metastasis and the effect of the medicine against cells.