992 resultados para Bracciolini, Poggio, 1380-1459


Relevância:

10.00% 10.00%

Publicador:

Relevância:

10.00% 10.00%

Publicador:

Resumo:

重建古气候、古环境已成为当今全球变化研究的热点。5000以来是人类有文字记录的历史时期,其气候与植被变化与人类活动十分密切,对这一时期的气候变化的研究,具有重要的理论意义。 植被的状况可以在相当大的程度上反映气候的状况。孢子和花粉由于其个体小、产量高和易于保存而成为植被演替和古气候、古环境研究的重要手段之一。 孢粉组合的变化可以很好地反映植被的演替,吉林地区地层沉积比较稳定,本文选取哈尼湖钻孔360-0cm(5112-0aBP)的沉积物进行孢粉分析,共采取样品85个,平均时间分辨率约为60年。样品中花粉含量非常丰富,种类以乔木为主,其百分含量多在80%以上,最高可达96%,根据花粉组成在钻孔上的变化,结合花粉沉积率进行样品的分析,自下而上可分为4个花粉组合带,进而得出5000年以来该区气候演化大致可分为4个阶段:阶段1(5112-3784aBP),阔叶类乔木占优势,湿生及水生草本比较丰富,气候温暖湿润;阶段2( 3784 -1380aBP)针叶类乔木占优势,湿生及水生草本消失,气候变凉干;阶段3( 1380 -994aBP),以松为主的针叶类仍占绝对优势,喜温湿的灌木草本含量持续下降,说明气候继续变冷变干;阶段 4( 994-0aBP),植物种类比较丰富,湿生植物的沉积率明显增高,气候变的更加湿润。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

自然生境中,风是一种重要的生态/环境因子,已经引起生态学家的广泛兴趣。然而,目前对风和竞争如何共同影响植物行为的理解还很少。本文基于野外控制实验,研究赖草(Leymus secalinus)、黍(Panicum miliaceum)、油蒿(Artemisia ordosica)和雾冰藜(Bassia dasyphylla)四种沙生植物生长和形态特征对风和竞争的综合反应,以及降雨量变化是否修饰风和竞争的生态学效应。 风和竞争显著影响赖草和黍的生长和形态特征。赖草和黍的总生物量和分蘖数受密度效应影响较大,没有竞争的植株生物量和分蘖数都显著高于有竞争的植株。赖草和黍的根冠比和株高则受风因素的显著影响:风速越大,植株越趋向于降低株高并将更多的生物量分配到地下部分。除赖草株高显著外,竞争和风对两种植物生长和形态特征的交互作用不明显。 在风、竞争和水分实验中,风、竞争及其交互作用对油蒿和雾冰藜形态特征均有显著影响。油蒿株高在中风环境中最大,而雾冰藜株高在大风环境中最小;油蒿基径在弱风环境中最小,而雾冰藜则相反。种内竞争情况下的油蒿株高和基径显著高于种间竞争,而雾冰藜则相反。种内竞争情况下的油蒿株高和基径随风速的增大而减小;种间竞争情况下的油蒿株高和基径在弱风环境中最小,中等风区最大。油蒿和雾冰藜的分枝数都受竞争的显著影响,种间竞争情况下的油蒿分枝数显著高于种内竞争,而雾冰藜则相反。风显著影响油蒿的茎重比和雾冰藜的冠重比。油蒿的茎重比随风速的降低而降低。弱风环境中,雾冰藜的冠重比显著高于强风环境下的。风和竞争的交互作用显著影响油蒿生物量。种内竞争情况下,油蒿生物量在大风环境中最大,中风环境中最小;种间竞争情况下,油蒿生物量在中风环境中最大,弱风环境最小。水分显著影响油蒿的茎重比,以及雾冰藜的根冠比和基径,而对这两个种的其他生长和形态特征无显著影响。低水分情况下,油蒿的茎重比显著较高,雾冰藜的基径显著较低,并且分配更多生物量到地上部分。 这些结果初步表明,单优群落中的优势种或呈聚集分布的种群中,植株的生长符合“密度效应”原则,即密度越大,单株植物的生物量越小;并且在大风环境中,趋向于分配更多生物量到地下部分。种内竞争情况下油蒿幼苗的竞争能力强于种间竞争,这可能是自然群落中的油蒿不是聚集分布的一个原因。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This work was supported by grants from the National Basic Research Program of China (973 Program, 2007CB411600), the National Natural Science Foundation of China (30621092, 30623007), and Bureau of Science and Technology of Yunnan Province.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

检测p2 4抗原的诊断试剂在AIDS研究和防治方面具有重要意义。为研制国产HIVp2 4抗原诊断试剂 ,根据国内外文献 ,合成了HIVp2 4抗原的六个肽段 :G -A 12 ,D -R 16 ,P -S 18,A -G 2 3(HIV - 2ROD) ,P -S 18,N -I 15以及D -C 2 2。六个肽段中 ,N -I 15肽和D -C 2 2肽用于制备McAb ,其余 4个用于制备山羊抗血清。除D -R 16肽的滴度较低 (1∶2 0 0 0 )外 ,其余三个肽的抗血清滴度都在 1∶10 0 0 0以上。McAb中 ,N -I 15肽的反应比D -C 2 2肽要强 ,但两者的腹水滴度相同 ,均为 1∶10 0 0。单抗铺板检测病毒 p2 4抗原的非特异性反应比较强。用山羊抗血清铺板 ,1∶80 0 0的稀释度检测效果最好。用我们研制的抗体检测不出裂解HIV - 1ⅢB中 p2 4 ,却能够测出Abbott公司p2 4抗原诊断试剂盒的阳性对照 (HIVAG - 1)。用北海道大学免疫科学研究所研制的单抗和人阳性血清做的交叉对照实验表明 ,可能是由于合成肽免疫产生的抗体与裂解病毒p2 4的亲和力较差引...

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The present overview summarizes data from one year's study during the period of 1379 to 1380 in the regions by "Anzali" lagoon called "Abkenar" and "Hendkhale". Specimens from this lagoon obtained weekly during mordad and shahrivar mounths (July 21 to september 21). The study included 67 types of 5 phytoplanktonal phylum. In "Abkenar" region Cyanobacters with maximum of 97% and minimum of 64.5% of total combination of phytoplanktones made the dominating combination during the period of study , while in "hendkhale" chyrsophyta with maximum of 89% and minimum of 38.7% of total phytoplanktonal was the dominating figure at the same period of time. Researches on ecological parameteres showed that the avarage dissolved oxygen in -Abkenar" and "hendlchale" regions was 10.7 and 8.0 mg/lit respectivly, also total rate of Phosphat in these regions was 0.085 and 0.15 mg/lit respectivly. This study showed that the rates of Nitrat and Amonium in "Abkenar" region was 0.043 and 0.79 mg / lit while for the same substances in "Ilendkhale" measured 0.08 and 0.7 mg I lit respective. Also the avarage rate of chlorophyll a in these two areas measured 58,38 and 40.45 j.un /ht respectivly. Depending on results of correlation cofficient in "Abkenar" region we had Cyanobacters , water and air temperature , Chlorophyll a and total amount of Phosphat as a poitive correlation with transparency while Amonium and Nitrat showed , a negative correlation , EC and finally dissolved oxygen showed a very low rate of correlation coffiocient. To perform this research 5 genus of Cyanobacteres horn "Anzali" lagoon have been isolated and cultured in a laboratorial conditions Later by using Mouse Bioassay method one of these genus identified as a toxic algae. Levels of LD50 with intra peritoneal injection of toxin on mouse in 24 hours was 660 mg/kg and Levels of LC50 by using Bioassay method on Artemia and Daphnia has been shown 618 and 1000 mg kg respectively. Also the physiological effects of were investigated. algae on two types of Cypronides family called Cyprinus carpi° and Hypophrthabnichthys Resultes of blood analyses of Cypronides who were feeded by toxic algae showed a significant decline (P < 0.05) in white and red blood cells and their hematocrites. Levels of LDH , SGOT and SGPT in their blood serum had a significant increase in porportion to control group (P < 0.05) but there was no evidance a differences in Total Protein levels. Pathological studies show damage and destruction of hepato pancreas and kidney of these fishes. Signs and symptoms of intoxication caused by Cyanobacter called Planktohrix agardlltii in mouse and fish show heptotoxic character. This toxin belongs to cyclicpeptides of microcystines group.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Schizothorax zarudnvi, is an endemic fish of east country waters. (Triple lagoons of Hamoon and relevant water resources) that in the world it is reported in this resource specially. This fish named Hamoon mahi is one of the most economically valuable species in this region. Because of the recent years droughts, Hamoon logoon has been drive since 2000. Also, semi-wells (a semi natural resource) were affected drastically by recent drought years and their volume reduced to nearly one third of their real volume and resulted in changing at growth and reproduction physiology process in Schizothorax zanidnyi, brood stocks. Beginning of this project was done from October 2003. It's field studies begun (brood catching) since November 2001 by two methods including entangling gairs and at semi wells of Sistan that (Beach seine) had maximum rate of preparing qualified brood stocks. Broods transferred to Cyprinidea reproduction work shop of Zahak and after taking primary measures they stored in to the edaphic pools. Increasing the success safety factor (coefficient) for artificial reproduction of Sthizothorax zarudnyi , identifying the appropriate tune for Hormonal acceptance (physiological preparation of broods) is needed , so this important work was done regularly by histological studies and GSI measurements since November. Highest GSI rates of females (%80.51) and highest IV stage abundance of sexual maturity (%l 00) were observed an march. On the base of this date, Hormone therapy was done on broods on march. The used hormones are as follows Hypophysis. extraction, GnRHa and Anti Dopamin at the dozes of 3-6 ml, 20-30kg and 10-15 ml per kg body weight respectively and 2-3 times from 11-12-80 they were injected. Injected broods kept in to two circumstances, flow-through (rounded pool) and stagnant systems. In stagnant system 14 and 19 individuals of female and male (Schizothorax zauiulnri) broods, respectively injected in 11th, 15111, 19th, and 24th of march 1380. Non of the injected broods in 11 and 15 and 19th march (in stagnant Condition) answered to Hormone therapy. After final injection broods had general less activity and a few of them died. Mean temperature of brood pond waters (daily) which were injected. Fluctuated between 10-25-13. 63°c but injected broods on 24th march had different characteristics. They had pale color and had few fecundity. In this stage of injection they hadn't any successful vulation. After injection, Mean daily water temperature was 15, 88-17, 54°c. In Flowing system, 13-16 individual of males and females respectively were injected on 15th, 19th, 22th and 23th march. None of injected producers on 15th and 19th march with mean daily water temperature of 10, 25-12°c were prepared for spawning but injected producers on 22nd an 23th march with mean daily water temperature of 13.5-1 rc responded about 75-100 percent. (Schizothorax zarudnyi) brood stocks were prepared for spawning after 353-428 hours/day from final injection. Diameter of obtained eggs (before fertilization) was between 1.9-2.3 min and of fertilized eggs was 3.8mm. Fertilized eggs of (Schizothorax zarudnyi) were hatched after 6-7 days with mean water temperature of 17.08°c. Mean length of on one day larvae was 9.47 mm. Larvae was 9.47 mm. Larvae adsorbed the whole yolk sac after , 5-6 days at 17- 1°c and were prepared for releasing in to edaphic pools. Because of the lack of necessary and complementary facilities in the region , they had to release them in to veniros and growing them for 8 days. At the end of 18th day , 35000 larvae (at first) released into an edaphic pond with a volume of 150m2. After growing them for one moth , mean length and weight of new hatched larvae was 29.41 mm and 1.12►r , respectively. With respect to results of this investigation , artificial reproduction of (Schizothorax zarudnyi) Can be possible at 14-17°C and flowing water with Hormonal treatment. It -s breeding has increased development than other cultural specious in the region. Due to high economical value of this specious in Sistan and ti-s specialization east waters of Iran and having high resistance and proper growth There is a need of it's development and reproduction and culture in fish culture fanns (edaphic ponds• two-purpose pools) at the region and country.