934 resultados para Virgilio Maron, 70-19 a.C.
Resumo:
A bioassay study was conducted using three organic pesticides to determine their comparative toxicity to fingerlings of Hypophthalmichthys molitrix. There was wide variation in the toxicity of different pesticides with 24 hr LC sub(50) values ranging from 0.000403 to 0.294 mg/l. Endosulfan appeared to be the most toxic, whereas BHC was the least.
Resumo:
涡度相关技术是唯一能直接测定大气与植被间CO2通量的标准方法。随着全球变化研究的深入,人类活动干扰下陆地生态系统碳通量研究越来越受到关注,对草地生态系统的研究更是备受关注。本研究选择位于内蒙古典型的农牧交错区——多伦县的典型克氏针茅草地和被开垦的农田为研究对象,利用涡度相关技术,结合各环境因子,在不同时间尺度上探讨了控制内蒙古草地生态系统碳通量可能的生理机制。利用一年多净生态系统CO2气体交换(NEE)通量的观测,量化了这个地区草地生态系统的碳储备量,并进一步阐明了开垦对该区域生态系统物质能量流动的影响。我们还利用Keeling同位素曲线与微气象技术相结合的方法把生态系统夜间呼吸区分为自养呼吸和异养呼吸;同时利用同化箱式法,把草地生态系统白天群落呼吸进行了区分,进一步了解了不同生态过程对净碳通量的贡献。 结果表明,控制该地区生态系统碳通量主要的环境因子是土壤含水量(VWC)和温度。两个生态系统的植被叶面积指数(LAI)和生物量在非干旱季都要高于干旱季,因而两个生态系统在非干旱季不同环境因子的不同梯度下的NEEmax都比干旱季的要高。两个生态系统NEE的最大日变幅和日最大值在非旱季与旱季十分接近,说明即使土壤水分有所改善,但由于这个地区贫瘠的土壤限制了生态系统的净碳交换量而使这两个生态系统的固碳能力依旧不高。无论是旱季还是非旱季,草地生态系统呼吸的温度敏感系数Q10都随土壤含水量的增加而增加,这除了水分的促进作用外,另外就是生长旺季根生物量的增加。而在两个生长季里农田生态系统的Q10都随土壤含水量的变化不是很规则,这主要是因为农作改变了植被类型和土壤的物理结构从而引起生态系统微环境、微生物活性以及根生物量的改变,结果影响生态系统呼吸对温度的敏感性。 在连续两个生长季里,两个生态系统碳通量随季节的变化都有明显的日变化,7月份的日变化最大,而且农田生态系统的NEE日变幅大于草地生态系统NEE的日变幅。两个生态系统每个月NEE的日最大值都出现在上午8~9点左右,而生态系统的呼吸(RE)的日最大值都发生在下午14~16点左右。冬季两个生态系统各组分碳通量的日进程几乎都没有差异,系统基本处于碳平衡状态。进入春季,幼小的植被限制了生态系统的碳同化。期间的耕作促进了土壤CO2的大量释放,同时较频繁的降雨不仅影响植被吸收光以进行光合固定碳,同时也进一步加大了农田CO2的释放,结果农田生态系统释放的CO2比草地生态系统多。夏季,两个生态系统都是吸收碳的库,农田生态系统因较高的LAI和较低的生态系统呼吸温度敏感性使其NEP远高于草地生态系统的NEP,是一个较强的碳库。秋末,草地生态系统几乎处于碳平衡的状态。农作物的收割,使得大量含不溶性物质较低枯叶和秸秆残留在地里,农田生态系统呼吸释放的碳量显著高于同期草地释放的碳量。通过2005~2006年对两个生态系统碳通量进行一整年的观测,发现两个生态系统年净固碳量相当,草地净固定71.3 g C m-2,农田净固定64.4 g C m-2。但秋季的收获使农田生态系统近70%的生物量被收走,降低了该系统的固碳能力。 为进一步了解不同生态过程对净碳通量的贡献量,我们利用浓度梯度-同位素法与微气象技术相结合的方法,初步将生态系统呼吸区分为自养呼吸和异养呼吸。草地生态系统在生长旺季自养呼吸占总呼吸80%以上,而农田生态系统在生长季阶段异养呼吸所占整个生态呼吸的比例从60%上升至作物成熟时的80%以上。降雨不仅显著增加草地生态系统呼吸的释放量,而且主要是显著增加了异养呼吸的释放量。此外,我们还利用同化箱式法对草地生态系统的群落呼吸进行区分,结果显示群落总呼吸(Re)有明显的季节变化,最高值在生长季中期。凋落物分解、土壤有机质呼吸、根呼吸和地上植被呼吸在整个生长季平均分别占总生态系统呼吸的19.4%、37.8%、9.8%和32.9%。构建各组分呼吸通量与温度的指数关系,结果显示根呼吸的温度敏感系数最大,土壤有机质的温度敏感性最低。降雨后首先促进了异养呼吸,随后植物的呼吸也开始变大,群落呼吸释放的最高峰出现在雨后第二天。 本研究初步分析了控制内蒙古农牧交错区草地生态系统碳通量的主要因子,量化了该区域草地生态系统的碳储备量,并进一步阐述了开垦对该区域生态系统碳通量的影响。同时尝试不同方法对生态系统碳通量进行了区分,得出了一些具有生态学意义的结果,为进一步探讨控制生态系统碳通量的生理机制提供了可能。
Resumo:
预测下世纪中叶,大气CO_2浓度将高到目前的两倍(即达到700μ1•1~(-1))。CO_2倍增对植物地上部的影响已经有了较多的研究,胆是由于方法学上的困难,至今关于倍增CO_2对植物根及根区微生物的研究仍是非常匮乏。本文应用国际上最新的根研究方法,以根系为中心,研究开顶式CO_2C熏蒸培养室中,CO_2倍增条件下根系与地上部,根系与根区微生物[共生的泡囊-丛枝菌根(VAM)真菌,非共生的土壤微生物]的关系。 1. CO_2倍增对根系的影响目前CO_2倍增对根系影响的研究多集中在根生物量的测定,或根/冠比值的测定,而善于其它参数如根长度则很少涉及,而根表面的反应目前还未见文献报道。本实验以幼苗期小麦“青323”(Triticum aestivum)、水稻“中作 29”(Oryza sativa)、大豆“科农4号”(Glycine max)、玉米“农大3138”(Zea mays)、甜高粱“M-81E”(Sorghum saccharatum)为材料,研究CO_2倍增对植物生物量的影响,发现CO_2倍增使C_3植物水稻、大豆的地上部、根系干重均显著增加,使小麦的根系干重显著增加,地上部无显著差异;C_4植物玉米和甜高粱的地上部和根系均没有显著反应。植物干重反应资料表明在光合产物的分配方面,C_3和C_4植物之间存在巨大的差异。 为了解根系获取土壤资源的能力的变化,我们对根系总长度和总表面积进行了分析。用样格交叉法研究根系长度的变化,结果显示,幼苗期的小麦、大豆的根系长度均被显著促进,尤其值得注意的是,尽管玉米根系干重没有显著改变,但是根长度已发生显著变化。同时应用研究根系表面积的最新方法-Na NO_2吸附法,研究发现幼苗期小麦、水稻和大豆的根系表面积在CO_2倍增条件下均显著增加,C_4植物玉米的根表面积亦有显著增加,但甜高粱的根表面积却没有显著反应,这说明即使在C_4植物类型中,根系表面积的反应在不同物种间仍存在很大差异。由于根长度和根表面积增幅大于根干重的增幅,所以推断在CO_2倍增条件下,植物根系细根比例增加,这有利于植物获取更多的养分。由于不同植物之间根系的反应不同,这将改变群落中原有的根系竞争关系,从而影响群落中物种的组成。 2. CO_2倍增对VAM真菌侵染强度和活力的影响本文应用NBT染色法,并结合浸染强度等级和活力等级标准,首次对CO_2倍增条件下,植物VAM真菌的侵染强度和活力的变化进行了检测。对比常规的酸性品红乳酸甘油法和NBT法,发现两者在显示侵染强度时元显著差异,但后者能同时用于侵染活力等级的研究。对幼苗期大豆以及不同生长期的小麦和玉米根系VAM真菌的侵染强度和活力进行观测,结果显示,倍增CO_2对大豆的侵染强度和活力均没有显著效应;使幼苗期玉米的侵染强度显著增加,但侵染活力无显著差异,但随生长期的推移,侵染强度所受的CO_2倍增效应逐渐减小,与14天苗龄(DAP)和35DAP相比,侵染活力在22DAP时所受效应最大;使10DAP小麦的VAM侵染强度和活力均显著增加,而且这种效应在30DAP小麦中的表现与10DAP小麦的相同。说明C_3、C_4植物中,菌根真菌对CO_2倍增反应不同,这也许是C_3、C_4植物对CO_2倍增反应不同的原因之一。倍增CO_2改善了VAM真菌的发育,所以较之于非菌根侵染植物,菌根侵染植物将因为CO_2倍增而获益更多,另一方面不同种植物中,VAM真菌的发育反应不同,这将使植物群落中,根系获取无机营养的竞争能力发生变化,最终影响植物群落的物种丰度和生物多样性以及群落的演替。 3. CO_2倍增对非共生土壤微生物的影响CO_2倍增使生长70天的小麦、垂柳(Salix babylonica)、藜(Chenopodium album)、繁穗苋(Amaranthus cruentus)品种“红苋K112”的地上部和根系的生物量增加。以这些植物所在土壤为材料,用氯仿熏蒸直接提取法研究土壤微生物生物量C(C_(mic))和生物量N(N_(mic))的变化,发现CO_2倍增尽管使各类型植物的C_4植物)土壤中C_(mic)的变化趋势不完全相同(小麦和藜所在土壤的C_(mic)下降,垂柳中C_(mic)升高,而在繁穗苋中无显著差异),但N_(mic)在各物种所在土壤中均有不同程度的上升,在繁穗苋中增幅最大。C_(mic):N_(mic)比值在4个物种所在土壤中均明显下降,这意味着CO_2倍增后在植物生长后期,土壤微生物活性提高,分解植物凋落物和土壤中其它有机质的能力加强,从而改善贫瘠土壤中有机质质量。 4.CO_2倍增对植物呼吸和光合作用及C素积累的影响 1)CO_2倍增对植物暗呼吸的影响:以杜仲(Eucommia ulmoides)、紫花苜蓿(Medicago sativa)和玉米等10种植物的离体成熟叶片或整株为材料,研究不同测定温度(15~35 ℃)下,CO_2倍增对植物暗呼吸的影响。结果表明:在较低温度(15 ℃、20 ℃)下,CO_2倍增对植物暗呼吸没有显著效应;在较高温度(30 ℃、35 ℃)时,多数被测植物的暗呼吸显著增强。由于植物在不同温度时它们的暗咱吸受CO_2倍增的促进幅度不同,这将导致不同地区(环境温度不同)的植物暗呼吸反应有差异,而且由于不同物种的暗呼吸增幅不同,综合光合效应,它们的生物量的反应也会不同。 2)CO_2倍增对整株植物的CO_2气体交换及植物C素积累的影响:利用自行设计的一套CO_2气体测定装置,首次尝试同步测定CO_2倍增条件下幼苗期小麦地下部和地上部的气体交换在昼夜24小时内的变化及C素的积累。发现CO_2倍增不仅使小麦地上部C素的积累增加,也使地下部释放的C素增加,但整株植物的C素收入仍高于对照两倍多,这从植物与环境的CO_2气体交换角度为CO_2倍增促进植物生物量的增加提供了依据。并首次提出:植物的整体性及植物所在的环境条件(主要是温度和光照强度)决定着植物暗呼吸对CO_2倍增的响应方式:被抑制或无效应。
Resumo:
首次报道了中国4种蝙蝠的G-带和C-带核型。大长舌果蝠(Eonycteris spelaea)二倍染色体数目(2n)为36,常染色体臂数(FN)为56;马来假吸血蝠(Megaderma spasma)2n=38,FN=70;黑髯墓蝠(Taphozous melanopogon)2n=42,FN=64;皱唇蝠(Chaerephon plicata)2n=48,FN=54。通过C-带显示,除着丝粒异染色质外,在皱唇蝠的许多染色体臂内和马来假吸血蝠染色体的端粒处也有较多的插入异染色质,大长舌果蝠的基因组中既有臂内异染色质也有端粒异染色质。
Resumo:
对养殖褐牙鲆( Paralichthys olivaceus) 的线粒体DNA Cytb 基因的部分序列进行测定,测得的目的DNA 片段的长 度为410 bp ,其A(104 bp) 、T(119 bp) 、C(117 bp) 、G(70 bp) 4 种碱基平均含量分别为25. 4 %、29. 0 %、28. 5 %、17. 1 %。 在28 个褐牙鲆个体中共出现了3 种单倍型。白化褐牙鲆出现的第1 种和第3 种单倍型个体数分别为10 尾(占白 化褐牙鲆样本数的90. 91 %) 和1 尾(9. 09 %) ;6 尾黑化褐牙鲆均出现第1 种单倍型(100 %) ;正常褐牙鲆出现的3 种 单倍型尾数分别为7 尾(占正常褐牙鲆样本数的55. 56 %) 、2 尾(22. 22 %) 和2 尾(22. 22 %) ;测得的序列与既知序列 间在第6 bp 、第19 bp 和第402 bp 碱基处出现差异。由于褐牙鲆Cytb 基因的高度同源性,研究其白化、黑化和正常 状态时出现的序列差异,对于寻找褐牙鲆白化机理研究的分子标记意义重大。
Resumo:
Suitable areas for fishing have been located in the middle and upper regions of the Mahanadi course of Hirakud reservoir. In the former the suitable period is during summer and beginning of monsoons, and in the latter in summer and winter months. The fishery of the reservoir is contributed by four species namely S. silondia, L. fimbriatus, C. mirgala and C. catla.
Resumo:
The first aim of this research was to identify fatty acids, amino acids composition of Thunnus tonggol roe and their changes during cold storage (-18'C). The second aim was to determine the changes of moisture, protein, fat and ash contents of the roe during one year cold storage (-18'C). 60 samples of longtail tuna (Thunnus tonggol) ovaries were randomly collected form Bandar-e-Abbas landings. The samples were frozen at-30'C and kept in cold store at -18'C for one year. According to a time table, the samples were examined for identification of fatty acids, amino acids, moisture, protein, fat, ash, peroxide and T.V.N. and their changes were evaluated during this time. The results showed that 26 fatty acids were identified. The unsaturated fatty acids (UFA) and saturated fatty acids (SFA) were 62.33 and 37.6%, respectively, in fresh roe. So that, DHA (C22:6) and oleic acid (C18:1) had high amounts (24.79 and 21.88%) among the UFA and palmitic acid (C16:0) was the most content (22.75%) among the SFA. The PUFA/SFA was 0.91. Also, 17 amino acids were identified that essential amino acids (EAA) and nonessential amino acids (NE) were 10478 and 7562 mg/100g, respectively, and E/NE was 1.38. Among the EAA and NE, lysine (2110mg/100g) and aspartic acid (1924 mg/100g) were the most contents. Also, results showed that moisture, ash, protein and fat contents were 72.74, 1.8, 19.88 and 4.53%, respectively, in fresh roe. The effects of freezing and cold storage on the roes showed that UFA and SFA contents have reached to 49.83 and 48.07%, respectively, at the end of cold storage. It indicated that these compounds change to each other during frozen storage. Also, n-3 and n-6 series of fatty acids were 32.75 and 1.61% in fresh roe. But their contents decreased to 22.96 and 1.25% at the end of period. Among the fatty acids, 22:6 and C16:0 had the most changes. The changes of fatty acids were significantly at 95% level except for C15:1, C18:3(n-3) and C20:4(n-6). All of the amino acids decreased in frozen storage and their changes were significantly (P<0.05). EAA was 7818 mg/100g and E/NE was 1.27 at the end of storage period. Among the amino acids, leucine and lysine had the most changes. Moisture, ash, protein and fat contents were 70.13, 1.82, 19.4 and 6.51%, respectively, at the end of storage period. The peroxide value and T.V.N. increased during storage. So that, their contents have reached to 5.86 mg/kg and 26.37 mg/100 g, respectively, at the end of frozen storage. The best shelf life of Thunnus tonggol roe was 6 or 7 months, because of lipid oxidation and increasing of peroxide.
Resumo:
黑长臂猿(H y lobates concolor) 是现生11 种长臂猿中其系统地位最低的灵长类。历史时期 长臂猿曾广泛分布在我国南部的大部省区。自公元4 世纪以来, 它们的分布发生了很大变化。分 布区从北到南, 从东到西急剧缩小, 现黑长臂猿缩小到只在海南岛、云南南部和越南北部, 已 分化为6 个亚种。分布于我国的5 亚种中, 海南亚种(H. c. hainanus) 现今仅20 余只, 是最 濒危的一个亚种; . 北部湾亚种(H. c. nasu tus) 50 年代曾在广西西南部发现, 60- 70 年代已绝 迹; 指名亚种(H. c. concolor) 主要分布于越南北部、滇南和滇中哀牢山。滇南约有100 余只, 滇中哀牢山可能有40- 60 群, 180- 240 只; 景东亚种(H. c. j ing d ong ensis) 为滇中无量山的 特有亚种, 现有100- 116 群, 430- 500 只; 滇西亚种(H. c. f u rvog aster) , 只分布在滇西南的 沧源、镇康、云县和耿马等地, 约有26- 42 群, 100- 150 只。现今, 黑长臂猿的分布区已不足 1 000Km 2, 总数量约1 000 只, 为高度濒危的灵长类动物。造成黑长臂猿濒危的主要原因是: 热 带和南亚热带原始森林的被破坏和缩小、人类活动的干扰使生境破碎和恶化、过度猎捕和长臂 猿自身的生物学弱点。目前, 中国的黑长臂猿已在9 个自然保护区中得到保护。
Resumo:
用维生素C含量为38、364和630mg/kg的三种饲料饲喂初体重为(23.19±0.58)g的长吻8个月,实验结果表明,38mg/kgVC饲料组饲喂的长吻表现出了典型的VC缺乏症状:体色发黑,脊椎侧弯,鳍边由开始的萎缩直到腐烂、贫血、特定生长率显著降低(p<0.05)。并且38mg/kgVC饲料组长吻的生理指标也受到影响:血清溶菌酶活性显著下降(p<0.05),肝脏的SOD活性及MDA含量均显著升高(p<0.05),血清皮质醇没有显著差异(p>0.05),但各处理组长吻肝脏中均未检测到诱导型HS
Resumo:
Microcystins are heptapeptide toxins produced by cyanobacteria. Microcystin-RR(MC-RR) is a common variant among the 80 variants identified so far. There have been many investigations documenting the toxic effects of microcystins on animals and higher plants, but little is known on the toxic effects of microcystins on algae, especially at molecular level. We studied the effects of MC-RR on gene expression profile of a few antioxidant enzymes and heat shock protein-70 (Hsp70) in Synechocystis sp. PCC6803. After two days post-exposure, a high dose toxin (5 mg/l, about 4.8 x 10(-3) mM) significantly increased expression levels of the genes gpx1, sodB, katG, acnB, gamma-TMTand dnaK2, while a relatively low dose toxin (1 mg/l, about 9.63 x 10(-4) mM) induced a moderate and slow increase of gene expression. Our results indicate that MC-RR could induce the oxidative stress in Synechocystis sp. PCC6803 and the increase in gene expression of antioxidant enzymes and Hsp70 might protect the organism from the oxidative damage. in addition, cell aggregation was observed during the early period of exposure, which might be a specific oxidative stress reaction to MC-RR. (C) 2008 Elsevier Ltd. All rights reserved.
Resumo:
This paper demonstrates the first mode-multiplexed system over 19-cell hollow-core photonic band gap fibre, at 2×20Gbps using the LP0,1 and LP2,1-like modes. © 2012 OSA.
Resumo:
This paper demonstrates the first mode-multiplexed system over 19-cell hollow-core photonic band gap fibre, at 2×20Gbps using the LP0,1 and LP2,1-like modes. © 2012 OSA.
Resumo:
Methyl parathion hydrolase (MPH) is an enzyme that catalyzes the degradation of methyl parathion, generating a yellow product with specific absorption at 405 nm. The application of MPH as a new labeling enzyme was illustrated in this study. The key advantages of using MPH as a labeling enzyme are as follows: (1) unlike alkaline phosphatase (AP), horseradish peroxidase (HRP), and glucose oxidase (GOD), MPH is rarely found in animal cells, and it therefore produces less background noise; (2) its active form in solution is the monomer, with a molecular weight of 37 kDa; (3) its turnover number is 114.70 +/- 13.19 s(-1), which is sufficiently high to yield a significant signal for sensitive detection; and (4) its 3D structure is known and its C-terminal that is exposed to the surface can be easily subjected to the construction of genetic engineering monocloning antibody-enzyme fusion for enzyme-linked immunosorbent assay (ELISA). To demonstrate its utility, MPH was ligated to an single-chain variable fragment (scFv), known as A1E, against a white spot syndrome virus (WSSV) with the insertion of a [-(Gly-Ser)(5)-] linker peptide. The resulting fusion protein MPH-A1E possessed both the binding specificity of the scFv segment and the catalytic activity of the MPH segment. When MPH-A1E was used as an ELISA reagent, 25 ng purified WSSV was detected; this was similar to the detection sensitivity obtained using A1E scFv and the HRP/Anti-E Tag Conjugate protocol. The fusion protein also recognized the WSSV in 1 mu L hemolymph from an infected shrimp and differentiated it from a healthy shrimp.
Resumo:
Previous studies have demonstrated that germinal vesicle of amphibian oocyte contains small nuclear ribonucleoprotein polypeptide C (SNRPC). In this study, a putative member of SNRPC was identified from Carassius auratus gibelio oocyte cDNA library. Its full-length cDNA has an open reading frame of 201 nt for encoding a peptide of 66 an, a short 5'-UTR of 19 nt and a long 3'-UTR of 347 nt including a polyadenylation signal and poly- (A) tail, and the deduced amino acid sequence has 47% identity with the C-terminal of the zebrafish small nuclear ribonucleoprotein polypeptide C. Western blot analysis revealed its oocyte-specific expression. Immunofluorescence localization indicated that its gene product localized to numerous nucleoli within the oocytes and showed dynamic changes with the nucleoli during oocyte maturation. RT-PCR and Western blot analysis further revealed its constant presence in the oocytes and in the embryos until hatching. The data suggested that the newly identified CagOSNRPC might be a nucleolar protein. (c) 2006 Elsevier Inc. All rights reserved.
Resumo:
The growth and energy budget for F-2 'all-fish' growth hormone gene transgenic common carp Cyprinus carpio of two body sizes were investigated at 29.2 degrees C for 21 days. Specific growth rate, feed intake, feed efficiency, digestibility coefficients of dry matter and protein, gross energy intake (I-E), and the proportion of I-E utilized for heat production (H-E) were significantly higher in the transgenics than in the controls. The proportion of I-E directed to waste products [faecal energy (F-E) and excretory energy loss (Z(E) + U-E) where Z(E) is through the gills and U-E through the kidney], and the proportion of metabolizable energy (M-E) for recovered energy (R-E) were significantly lower in the transgenics than in the controls. The average energy budget equation of transgenic fish was as follows: 100 I-E = 19.3 F-E + 6.0 (Z(E) + U-E) + 45.2 H-E + 29.5 R-E or 100 M-E = 60.5 H-E + 39.5 R-E. The average energy budget equation of the controls was: 100 I-E = 25.2 F-E + 7.4 (Z(E) + U-E) + 35.5 H-E + 31.9 R-E or 100 M-E = 52.7 H-E + 47.3 R-E. These findings indicate that the high growth rate of 'all-fish' transgenic common carp relative to their non-transgenic counterparts was due to their increased feed intake, reduced lose of waste productions and improved feed efficiency. The benefit of the increased energy intake by transgenic fish, however, was diminished by their increased metabolism.