Relationship between viscoelastic transition and yield behavior of phenolphthalein poly(ether ketone)

The viscoelastic behavior of phenolphthalein poly(ether ketone) (PEK-C) and its relationship to yielding was studied. The following phenomena were observed: (1) The relaxation behavior at strain near yield closely approximated that at low strain but near the T-g; (2) the temperature and strain rate dependence of yield stress could be modeled by the one-process Eyring theory and the value of the activation volume was the same as that of the glass transition; and (3) according to the Zhurkov-Bueche equation, the cu transition was related to the yield behavior. All these results indicated that the glass transition was the main factor that controlled the yield behavior. (C) 1996 John Wiley & Sons, Inc.

SIMPLE-MODELS FOR STRESS-RELAXATION AND YIELD PHENOMENON OF PHENOLPHTHALEIN POLY(ETHER KETONE)

According to stress relaxation curves of phenolphthalein poly(ether ketone) (PEK-C) at different temperatures and the principle of time-temperature equivalence, the master curves of PEK-C at arbitrary reference temperatures are obtained. A coupling model (Kohlrausch-Williams-Watts) is applied to explain quantitatively the different temperature dependence of stress relaxation behavior and the relationship between stress relaxation and yield phenomenon is established through the coupling model.

Cultivation of the brown alga Hizikia fusiformis (Harvey) Okamura: controlled fertilization and early development of seedlings in raceway tanks in ambient light and temperature

Commercial cultivation of the dioecious brown macroalga Hizikia fusiformis (Harvey) Okamura in East Asia depends on the supply of young seedlings from regenerated holdfasts or from wild population. Recent development of synchronized release of male and female gametes in tumble culture provides a possibility of mass production of young seedlings via sexual reproduction. In this paper, we demonstrate that controlled fertilization can be efficiently realized in ambient light and temperature in a specially designed raceway tank in which the sperm-containing water has been recirculated. The effective fertilization time of eggs by sperm was found to be within six hours. Fast growth and development of the young seedlings relied on the presence of water currents. Velocity tests demonstrated that young seedlings of 2-3 mm in length could withstand a water current of 190 cm s(-1) stop without detachment. Culture experiments at 24 h postfertilization showed that elongation of both the seedlings and their rhizoids were not hampered by high irradiance up to 600 mu mol photons m(-2) stop s(-1) stop. However, growth was slightly retarded if cultured at a temperature of 16 degrees C compared to other culture temperatures of 22, 25 and 29 degrees C. No seedling detachment was observed after transfer of the young seedlings to raft cultivation in the sea after one and 1.5 months post-fertilization, indicating the feasibility of obtaining large quantity of seedlings in such a system.

Nitrogen deposition and carbon sequestration in alpine meadows

Nitrogen deposition experiments were carried out in alpine meadow ecosystems in Qinghai-Xizang Plateau in China, in order to explore the contribution of nitrogen deposition to carbon sequestration in alpine meadows. Two methods were used in this respect. First, we used the allocation of N-15 tracer to soil and plant pools. Second, we used increased root biomass observed in the nitrogen-amended plots. Calculating enhanced carbon storage, we considered the net soil CO2 emissions exposed to nitrogen deposition in alpine meadows. Our results show that nitrogen deposition can enhance the net soil CO2 emissions, and thus offset part of carbon uptake by vegetation and soils. It means that we have to be cautious to draw a conclusion when we estimate the contribution of nitrogen deposition to carbon sequestration based on the partitioning of N-15 tracer in terrestrial ecosystems, in particular in N-limited ecosystems. Even if we assess the contribution of nitrogen deposition to carbon sequestration based on increased biomass exposed to nitrogen deposition in terrestrial ecosystems, likewise, we have to consider the effects of nitrogen deposition on the soil CO2 emissions.

旱地地膜和秸秆双元覆盖栽培下小麦产量与水分效应

通过覆盖措施提高水分利用率对旱地农业生产具有重要意义。该文采用田间对比试验,研究了旱地冬小麦几种覆盖栽培下产量、水分利用率、土壤水分剖面和硝态氮的分布的差异。结果表明,地膜和秸秆双元覆盖模式下小麦籽粒产量比对照增产12.11%～17.65%,水分利用效率(WUE)比常规栽培提高7.2%～30.8%,土壤0～20 cm土层的含水量提高到12%～16%,硝态氮含量提高到4.70～10.17 mg/kg。地膜和秸秆双元覆盖模式能够显著的提高作物产量和水分利用率,并显著增加耕层土壤中水分含量和硝态氮含量,减轻了土壤剖面硝态氮的淋溶累积。

渭北旱塬冬小麦水·肥·产量关系研究

探讨了不同供水条件下土壤水分与作物产量的关系。[方法]以冬小麦品种长旱58为试材,设肥力和水分2因子高、中、低3水平9个处理组合,通过试验资料分析了不同养分和水分条件下作物的产量响应。利用2006年9月~2007年7月的气象资料研究了冬小麦不同生育期耗水量。[结果]各生育期耗水量占全生育期总耗水量的百分比以孕穗灌浆期最大,达45.6%,其次为拔节期,约21.5%,越冬期最小,约8.4%。底墒对旱作作物产量具有重要影响,施肥量过量会影响农田水分循环过程,使得高产农田的产量随降水量的变化而波动。[结论]提高作物土壤耗水量和土壤底墒利用率是黄土高原旱地农业实现高产稳产的关键。

半湿润区农田生态系统氮肥对不同基因型冬小麦产量构成的影响

施N对“NR9405”、“9430”、“偃师9号”、“小偃6号”、“陕229”、“西农2208”、“矮丰3号”和“商188”这8种不同基因型冬小麦产量构成影响的田间试验结果表明,单株分蘖成穗数、单位面积粒数和单位面积株数的差异同时受基因和N素营养水平控制。“矮丰3号”和“小偃6号”单株分蘖成穗数最多,分别为2.00分蘖穗/株和1.72分蘖穗/株,“9430”最少,为0.85分蘖穗/株。从不同基因型看,施N比不施N处理增加0.74穗/株,每穗粒数在不同基因型间存在极显著差异,以“西农2208”最多,为36.73粒/穗,“NR9405”最少,为24.35粒/穗,施N对每穗粒数无显著影响。单位面积株数主要受施N影响,基因型间差异相对较小。基因型和施N同时显著影响单位面积粒数和千粒重,但基因型对千粒重的影响程度大于N肥。从2个施N水平看,单位面积籽粒产量存在显著差异,“矮丰3号”、“西农2208”、“偃师9号”、“陕229”、“9430”、“小偃6号”、“商188”和“NR9405”依次减小,“矮丰3号”为435g/m2,“NR9405”为316g/m2,相差119g/m2。施N可极显著增加单位面积籽粒产量,不同基因...

Assessment effects of cage culture on nitrogen and phosphorus dynamics in relation to fallowing in a shallow lake in China

Nitrogen and phosphorus dynamics in relation to fallowing in a fish cage farm was investigated in a shallow lake in China. Four sampling sites were set: beneath the cages, at the cage sides, and 50 and 100 m east of the cage farm. Total nitrogen (TN) and total phosphorus (TP) in lake water and sediment were analyzed during a 2-year rearing cycle. The cage culture had a fish yield of 16.3-39.2 tonnes in the study period. Based on the mass balance equation, 1533-3084 kg TN and 339-697 kg TP were contributed to the lake environment. Nitrogen and phosphorous concentrations showed greater increase in the first culture period than in the second rearing cycle. No obvious changes were found at the sampling sites 50 and 100 m east of the cages during the study periods. Main impacts were found close to the cages (beneath the cages and at the cage side); the sampling points at the cage side showed relatively high TN and TP sedimentation. After 3 months of fallowing, water TN and TP decreased significantly but the sediment TN and TP contents remained high. Therefore, recovery seems to happen during fallowing but attention should be paid to whether the culture continues to operate in the future.

Differentiate performance of eight filter media in vertical flow constructed wetland: Removal of organic matter, nitrogen and phosphorus

A comparative study was conducted to reveal the differentiate effects of eight different filter media including gravel, zeolites, anthracite, shale, vermiculite, ceramic filter media, blast furnace steel slag and round ceramsite. The study mainly related to the eight different filter media's removal performances of organic matter, nitrogen and phosphorus in the vertical flow constructed wetland simulated system, which treating wastewater at hydraulic loading rate of 1000-2500 mm/d. The results indicated that the removal effects were closely related to the physical and chemical properties of medium materials. Anthracite-filled system had the highest removal rate for the total organic carbon (TOC), up to 70%, and the removal rates of other systems ranged from 20% to 30%. As for the five-day biochemical oxygen demand (BOD5), anthracite-filled and steel slag-filled systems had the highest removal rates, also up to 70%, as well as other systems all exceeded 50%. At the same time, for the total nitrogen (TN) and NH4(+)-N, the zeolites-filled and ceramic-filled systems had the best performances with the removal rates of more than 70%, the other way round, the removal rates of other systems were only about 20%. The distinguishable effects were also observed in removal performances of total phosphorus (TP) and total dissoluble phosphorus (TDP). The removal rates of TP and TDP in steel slag-filled systems were more than 90%, a much higher value, followed by that of the anthracite-filled system, more than 60%, but those of other systems being the less. Our study provided a potential mechanism to optimize the filter media design for the vertical flow constructed wetlands.

Hydrodynamics in an expanded bed of large size ion-exchange resin, and natural product adsorption

Successful applications of expanded bed adsorption (EBA) technology have been widely reported in the literature for protein purification. Little has been reported on the recovery of natural products and active components of Chinese herbal preparations using EBA technology. In this study, the hydrodynamic behavior in an expanded bed of cation resin, 001 x 7 Styrene-DVB, was investigated. Ephedrine hydrochloride (EH) was used as a model natural product to test the dynamic binding capacity (DBC) in the expanded bed. EBA of EH directly from a feedstock containing powdered herbs has also been investigated. These particles are different from commercially available expanded bed adsorbents by virtue of their large size (20S to 1030 gm). When the adsorbent bed is expanded to approximately 1.3 to 1.5 times its settled bed height, the axial liquid-phase dispersion coefficient was found to be of the order 10(-5) m(2) s(-1), which falls into the range 1.0 x 10(-6) to 1.0 X 10(-5) m(2) s(-1) observed previously in protein purification. Because of the favorable column efficiency (low axial dispersion coefficient), the recovery yield and purification factor values of EH directly from a feedstock reached 86.5% and 18, respectively. The results suggest that EBA technology holds promise for the recovery of natural products and active components of Chinese herbal preparations.

A C-type lectin associated and translocated with cortical granules during oocyte maturation and egg fertilization in fish

Oocyte maturation and egg fertilization in both vertebrates and invertebrates are marked by orchestrated cytoplasmic translocation of secretory vesicles known as cortical granules. It is thought that such redistribution of cellular content is critical for asymmetrical cell division during early development, but the mechanism and regulation of the process is poorly understood. Here we report the identification, purification and cDNA cloning of a C-type lectin from oocytes of a freshwater fish species gibel carp (Carassius auratus gibelio). The purified protein has been demonstrated to have lectin activity and to be a Ca2+-dependent C-type lectin by hemagglutination activity assay. Immunocytochemistry revealed that the lectin is associated with cortical granules, gradually translocated to the cell surface during oocyte maturation, and discharged to the egg envelope upon fertilization. Interestingly, the lectin becomes phosphorylated on threonine residues upon induction of exocytosis by fertilization and returns to its original state after morula stage of embryonic development, suggesting that this posttranslational modification may represent a critical molecular switch for early embryonic development. (C) 2003 Elsevier Inc. All rights reserved.

施氮水平对黄土旱塬区小麦产量和土壤有机碳、氮的影响

施用氮肥是提高作物产量和土壤有机碳(SOC)、氮(TSN)含量的重要养分管理措施。利用长期田间试验(19842~007),定量评价了常规耕作条件下5个施氮水平N 0(N0)、45(N45)、90(N90)、135(N135)和180(N180)kg/hm2处理下,小麦子粒产量、SOC、TSN和氮肥利用效率的变化。研究了施氮水平对黄土旱塬区小麦产量、SOC和TSN积累的影响。结果表明,19842~007年期间,N0、N45、N90、N135和N180处理小麦产量的平均值依次为1.2、2.4、2.9、3.2和3.4t/hm2;N0处理的小麦产量随试验年限而降低,年降低幅度达67 kg/hm2(P<0.001);但增施氮肥处理小麦产量降低趋势得到显著控制,当施氮水平提高到N 90 kg/hm2时,产量随年限呈现出缓慢升高的趋势。随着施氮水平的提高,地上部氮肥利用率由40%(N45)降低到28%(N180)。不同施氮水平条件下,SOC含量随年限呈缓慢升高趋势。23年后(2007年),N0、N45、N90、N135和N180处理下,0—20 cm土层SOC储量依次为16.9、18.2、18.7、19.0和19.1 t/...