876 resultados para Roma - Politica e governo - 30 A.C.-476


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The maturation pattern of sexual reproduction in Hizikia fusiformis (Harvey) Okamura (Sargassaceae, Phaeaophyta) was examined in 2003 at Yunao Bay, Nanao Island, Shantou, China. Maturation began in mid-April (seawater temperature 19-21 degrees C), reached the peak in mid-May (maturation rate ca. 70%, and seawater temperature 23.5-25 degrees C) and finished in late-June (seawater temperature 27.5-30 degrees C). The Hizikia plants continued to gain the length from the beginning of maturation season to reach a maximum mean length of 34.8 cm in mid-May, after which the mean length was reduced drastically due to the senescence and rupture of the larger plants in size. The major portion of the mature plants belonged to the larger plants between April and May, but to the smaller ones in June. It is suggested that the plant must achieve a critical size before reproductive maturation occurred. There was a positive relationship between the number of receptacles (NR), as well as the reproductive allocation (RA), and the plant size of Hizikia population, with the recorded maximum values of NR and RA being 1220 and 64.3% respectively, for a single plant.

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The dibenzofuran (DF)-degrading bacterium, Janibacter terrae strain XJ-1, was isolated from sediment from East Lake in Wuhan, China. This strain grows aerobically on DF as the sole source of carbon and energy; it has a doubling time of 12 hours at 30 degrees C; and it almost completely degraded 100 mg/L-1 DF in 5 days, producing 2,2',3-trihydroxybiphenyl, salicylic acid, gentisic acid, and other metabolites. The dbdA (DF dioxygenase) gene cluster in the strain is almost identical to that on a large plasmid in Terrabacter sp. YK3. Unlike Janibacter sp. strain YY-1, XJ-1 accumulates gentisic acid rather than catechol as a final product of DF degradation.

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Photosynthetic responses to irradiance and temperature of "leaves" and receptacles were compared in February ( vegetative stage) and May ( reproductive stage) in the seaweed, Hizikia fusiforme ( Harvey) Okamura (Sargassaceae, Phaeophyta) from Nanao Island, Shantou, China. Irradiance-saturated photosynthesis (P-max) was significantly higher in receptacles than in "leaves" on a fresh weight basis, and that of "leaves" was greater in May than in February at ambient seawater temperatures. The optimum temperature for P-max was 30 degrees C for both "leaves" and receptacles, being 5 - 10 degrees C higher than the ambient seawater temperature. The apparent photosynthetic efficiencies were greater in receptacles than in "leaves" within the tested temperature range of 10 - 40 degrees C. The irradiance for saturating photosynthesis for both "leaves" and receptacles was temperature-dependent, with the highest values ( about 200 mu mol photons m(-2) s(-1)) at 30 degrees C.

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The occurrence of the microcystins in the water bodies, especially in drinking water resources, has received considerable attentions. In situ chemical oxidation is a promising cost-effective treatment method to remove MC from water body. This research investigated the reaction kinetics of the oxidation of MCRR by permanganate. Experimental results indicate that the reaction is second order overall and first order with respect to both permanganate and MCRR, and has an activation energy of 18.9 kJ/mol. The second-order rate constant ranges from 0.154 to 0.225 l/mg/min at temperature from 15 to 30 degrees C. The MCRR degradation rates can be accelerated through increasing reaction temperature and oxidant concentration. The reaction under acid conditions was slightly faster than under alkaline conditions. The half-life of the reaction was less than 1 min, and more than 99.5% of MCRR was degraded within 10 min. (c) 2005 Elsevier Ltd. All rights reserved.

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Population parameters of Daphnia rosea were studied at various concentrations of Chlorella sp. (0.25, 0.75 and 3.0 mg C l(-1)) at several temperatures (20, 25, 28, and 30 degrees C) in the laboratory. Although there were some differences in the degrees of the effects of the various temperature-food combinations, both food and temperature exerted influences on almost all of the main population parameters of D. rosea. At a water temperature of 28 degrees C, growth and reproduction were reduced, and at the lowest food level (0.25 mgC l(-1)), reproduction failed. D, rosea did not survive at 30 degrees C in spite of abundant food supply, indicating that 30 degrees C is a physiological limit. A positive relationship between body length and brood size was recognized at high and medium food levels. The slope of the regression was the highest at the highest food level and at the lowest temperature (20 degrees C). The low food level exerted a negative influence on the net reproductive rate by lowering the size of egg-bearing females, by decreasing the brood size of each size class, by decreasing the brood number per female, and by increasing the period of empty brood chamber. High water temperature (28 degrees C) also exerted a negative influence on the net reproductive rate in a similar way. For the better understanding of the key factors driving the midsummer dynamics of daphnids in the field, it may be of crucial importance to compare the population parameters of the field populations with experimentally derived values under controlled conditions of food concentration and temperature.

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A growth trial was conducted at 30 degrees C to investigate the effect of body size on growth and energy budget of Nile tilapia. The average initial body weights of the four size groups tested were 9.3, 34.1, 80.3 and 172.4 g, respectively. Fish were fed to satiation twice a day with a diet containing 35.6% crude protein. Food consumption (C-max: kJ/day) increased with body size (W: g) according to the relationship: Ln C-max = 1.45 + 0.42 LnW. The final body contents of dry matter, crude protein and ash per unit body weight increased with increasing body size while contents of fat and energy were independent of body size. Specific growth rates of wet weight, dry weight, protein and energy decreased as the fish increased in size. Feed efficiencies in wet weigh, dry weight and crude protein decreased with increasing body size, while that of energy remained unchanged. The proportions of energy intake allocated to the various components (faecal energy, excretory energy, heat production and recovered energy) of the energy budget were not significantly affected by body size, and the average budget was: 100IE-18.5(+/- 1.33)FE + 5.9 (+/- 3.09)(ZE + UE) + 49.3(+/- 3.77)HE + 26.3(+/- 6.23)RE, where IE, FE, (ZE + UE), HE and RE represent gross energy intake, faecal energy, excretory (non-faecal) energy loss, heat production and recovered energy (growth), respectively. It is suggested that the decrease in growth rate in larger fish is mainly due to the decrease in relative food intake. (C) 1997 Elsevier Science B.V.

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Nile tilapia weighing 8.29-11.02 g were fed a practical diet at seven ration levels (starvation, 0.5, 1, 2, 3, 4% body weight per day and satiation) twice a day at 30 degrees C. Feed consumption, apparent digestibility, nitrogenous excretion and growth were determined directly, and heat production was calculated by difference of energy budget. The relationship between specific growth rate in wet weight (SGR(w), percentage per day) and ration size (RL, percentage per day) was a decelerating curve described as SGR(w) = 2.98 (1 - e(-0.61(RL-0.43))). The apparent digestibility coefficients for dry matter and protein showed a decreasing pattern with increasing ration while the apparent digestibility coefficient of energy was not significantly affected by ration size. The proportion of gross energy intake lost in nitrogenous excretion tended to decrease with increasing ration. Feed efficiency was highest, and the proportion of gross energy intake channelled to heat production was lowest, at an intermediate ration level (2% per day). The energy budget at the satiation level was: 100IE = 16.9FE + 1.2(ZE + UE) + 62.3HE + 19.6RE, where IE, FE, (ZE + UE), HE and RE represent gross energy intake, faecal energy, excretory (non-faecal) energy loss, heat production and recovered energy (growth), respectively. (C) 1997 Elsevier Science B.V.

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Young grass carp (12-13 g) were kept at five ration levels ranging from starvation to ad libitum feeding at 30-degrees-C. They were fed duckweed. Food consumption, absorption efficiency and growth were determined directly, and metabolism and nitrogenous excretion calculated indirectly from energy and nitrogen budgets, respectively. The relationship between specific growth rate and ration size was linear. Absorption efficiency for energy was not affected by ration size and averaged 50.6 +/- 0.57% (mean +/- s.e.). Depending on ration size, energy lost in excretion accounted for 4.5-5.9% of the food energy, energy channelled to metabolism accounted for 34.4-48.3% of the food energy, and energy retained as growth accounted for 6.7-11.9% of the food energy. Regardless of ration, a constant proportion of food energy (30.7%) was accounted for by feeding metabolism (total metabolism minus fasting metabolism). The energy budget at the maximum ration was: 100 C = 49.1F + 4.5U + 3.6R(fa) + 30.9R(fe) + 11.9G, where C, F, U, R(fa), R(fe) and G represent food consumption, faecal production, excretion, fasting metabolism, feeding metabolism and growth, respectively.

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Nanostructured FeAl intermetallics were prepared directly by mechanical alloying (MA) in a high-energy planetary ball-mill. The phase transformations and structural changes occurring in the studied material during mechanical alloying were investigated by X-ray diffraction (XRD). Transmission electron microscopy (TEM) was employed to examine the morphology of the powders. Thermal behavior of the milled powders was examined by differential scanning calorimetry (DSC). Disordered Fe(Al) solid solution was formed at the early stage. After 30 h of milling, Fe(Al) solid solution transformed into an ordered FeAl phase. The average crystallite size reduction down to about 12 nm was accompanied by the introduction of the average lattice strain up to 1.7%. The TEM picture showed that the size of milled powders was less than 30 nm. (c) 2007 Elsevier B.V. All rights reserved.

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We report on the material growth and device performance characterization of a strain-compensated In0.54Ga0.46As/In0.51Al0.49As quantum cascade laser at lambda similar to 8 mu m. For 2 mu s pulse at a 5 kHz repetition rate, laser action is achieved up to room temperature (30 degrees C). The tuning coefficient d lambda/dT is 1.37 nm K-1 between 83 K and 163 K and 0.60 nm K-1 in the range from 183 K to 303 K. The peak output power is reported to be similar to 11.3 mW per facet at 293 K and the corresponding threshold current density is 5.69 kA cm(-2).

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Methomyl, an extremely toxic pesticide, is widely used in agriculture. A strain named mdw-1 capable of degrading methomyl rapidly was successfully isolated from activated sludge in this study. It could utilize methomyl as the sole carbon or nitrogen source. The optimal temperature and medium pH for its growth and methomyl biodegradation were 30 degrees C and 7.0, respectively. It was identified as a Paracoccus sp. according to its morphological features, physiological and biochemical characteristics, and phylogenetic analysis based on the sequence of 16S rDNA. Gas chromatography-mass spectrometry (GC-MS) analysis showed that methomyl could be completely transformed to S-methyl-N-hydroxythioacetamidate in 10 h of incubation with the isolate mdw-1.

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大兴安岭地区是我国地带性多年冻土和冻土湿地的主要分布区,近30年来,大兴安岭地区整体增温显著,气候变化的幅度加大,加之人类活动的频繁,冻土退化严重,冻土湿地出现了原有湿地萎缩和新生湿地扩张的现象。目前,对大兴安岭多年冻土湿地的研究还非常有限,且定性的研究较多,定量的研究极少,多数研究集中于冻土湿地的分布,冻土与湿地之间的机理探讨及描述多年冻土退化对湿地产生的影响等方面。 本论文通过室内培养实验,分析不同温度和湿度梯度及冻融作用下,大兴安岭不同多年冻土区湿地两层泥炭有机碳的矿化状况。结合回归模型,分析大兴安岭多年冻土湿地泥炭有机碳矿化对不同温度和湿度的响应,探讨在气候预案下,大兴安岭多年冻土湿地对气候变化的潜在响应。获得的主要结论如下: (1)大兴安岭多年冻土湿地存在着碳储层,其不同的冻土湿地区由于自然条件、融深等因素的不同,碳储层的厚度也存在着差异。多年冻土湿地含碳量和含氮量都很高,有机碳含量随剖面深度的增加有降低的趋势,泥炭全氮的含量随剖面深度变化复杂,这与湿地土壤形成的气候条件、微地貌和植被类型等有关。大兴安岭连续多年冻土区泥炭,C/N比要高于不连续多年冻土区湿地,并且有机碳含量与全氮含量存在着很好的耦合关系。 (2)大兴安岭多年冻土湿地泥炭有机碳矿化随温度的升高而升高,在培养温度5-20℃下,总的泥炭有机碳矿化量变化范围为18.55~112.91 mg g-1。虽然连续多年冻土区湿地泥炭有机碳矿化率和矿化量都要高于不连续多年冻土区湿地,但经过温度敏感性系数Q10分析,大兴安岭不连续多年冻土区湿地泥炭矿化对温度的响应更显著。从一元动力学方程分析结果来看,大兴安岭多年冻土湿地泥炭有机碳的矿化对15℃响应更显著。 (3)土壤湿度对大兴安岭多年冻土湿地泥炭有机碳矿化产生一定的影响,泥炭总矿化量出现了先随湿度的增加而增加,达到最适宜值后降低的趋势。从本论文的实验设置来看,大兴安岭多年冻土湿地泥炭有机碳矿化的最适宜湿度为60%WHC。利用二元回归模型很好地反映了湿度对大兴安岭多年冻土湿地泥炭矿化的影响,模型推测大兴安岭连续多年冻土区湿地泥炭有机碳矿化的最优湿度为10-20cm层63%WHC,20-30cm层65%WHC;不连续多年冻土区湿地有机碳矿化的最优湿度为10-20cm层65%WHC,20-30cm层59%WHC。 (4)大兴安岭多年冻土湿地泥炭有机碳矿化受温度和湿度的影响显著,其之间的交互作用同样显著。连续多年冻土区湿地有机碳矿化量要高于不连续多年冻土区湿地,这与其含有更高的有机碳和全氮有关。温度和湿度对泥炭有机碳矿化的影响可以用二元二次回归方程很好的表示(P<0.001),通过回归方程和方差分析,结果表明温度和湿度对大兴安岭多年冻土湿地泥炭有机碳矿化都非常重要。 (5)通过培养实验结果显示,虽然温度仍是影响大兴安岭多年冻土湿地泥炭有机碳矿化的主要因子,但随冻融作用处理次数的增加,冻土湿地泥炭有机碳矿化量和温度敏感性系数Q10值有增加的趋势,这意味着冻融作用对大兴安岭多年冻土湿地泥炭矿化产生了不小的影响。虽然冻融作用对大兴安岭多年冻土湿地的影响并不是很大,但大兴安岭处于寒温带,在气候变暖下,冻融过程的频率将加高,冻融作用对大兴安岭多年冻土湿地的影响不容忽视。 (6)大兴安岭地区近30年气候变化趋势分析表明,年均温增长显著,年降水量变化幅度大。在气候变化下,对于不连续多年冻土区,多年冻土不断的退缩及最终的消失,会使冻土湿地萎缩和消失,原有的典型的贫营养的泥炭藓沼泽湿地可能演化为富营养的苔草沼泽湿地或灌丛沼泽湿地,对于大片连续多年冻土区,冻土湿地的变化更加复杂,出现的湿地类型会更多。通过线性气候预案下的大兴安岭多年冻土湿地泥炭有机碳矿化分析,结果显示大兴安岭多年冻土湿地对气候变化响应显著,特别是对于变湿的环境。气候变化下,大兴安岭多年冻土湿地泥炭存在着潜在的分解,多年冻土湿地与气候变化之间存在着正反馈机制。 目前研究表明,大兴安岭地区对气候变化特别敏感,对大兴安岭冻土湿地的研究既填补了国内研究的空白,又对全球的碳循环研究提供了数据支持,并且加深了对冻土湿地生态过程的了解。

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简要介绍了快重离子与固体相互作用研究的状况和快重离子引起固体电子发射的机制 ,讨论了电子能损导致原子位移的 3种微观模型 ,即“库仑爆炸”模型、“热峰”模型和“激发排斥”模型 ,简述了研究电子发射的实验测量装置和测量方法 ,讨论了总电子发射产额与电子能损的关系以及靶俄歇电子和快传输电子测量在电子激发诱发辐照损伤微观机制研究中的应用 ,并介绍了重离子在 C靶中产生的离子径迹处的电子温度和聚丙稀靶中离子径迹势的提取方法

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从发酵L山梨糖的Gluconobacteroxydans和Bacilusmegaterium2980混和菌株的无细胞抽提液中分离到了2酮L古龙酸还原酶(KGR),测得其分子量为90kDa。动力学性质研究表明它为一个典型的MichaelisMenten氏酶,对2酮L古龙酸作用的Km值为342×10-3mol,最适作用pH为65,最适作用温度为30℃。2酮L古龙酸还原酶的合成不受L山梨糖和2酮L古龙酸的诱导,故推测2酮L古龙酸还原酶是Gluconobacteroxydans的一个组成酶。

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用室外盆栽试验的方法,将土壤磁效应与生物磁效应相结合,以草甸土为供试土壤,油菜为供试作物,研究了盆栽条件下,磁处理土壤对油菜(BrassicanapusL.)油菜生物学产量和品质的影响,进一步探讨了磁场处理对土壤健康质量的改善作用。研究结果表明,磁场强度处理土壤不仅可提高盆栽条件下油菜的生物学产量,还促使其维生素C含量得以增加,而且油菜叶柄和叶片内的硝酸盐含量也降低,说明磁处理可以使土壤健康质量得到改善。200mT磁场强度是适于油菜生长的最佳磁处理参数。