936 resultados para 13368-026
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Thirteen morphometric and seven meristic characters, length-weight relationship and food and feeding habits of Otolithoides biauritus of Bombay coast (Maharashtra, India) were studied. Compared morphometric characters revealed positive allometric growth and high correlation ("r" ranging 0.898 - 0.996) between each other. Meristic characters were observed to be B sub(vii), D sub(1) 8-10, D sub(2) 27-31, P 17-20, V 5-7 and 7-10. Number of gill rackers on the first left gill arch ranged from 15 to 19. Length-weight relationship for both sexes together worked out to be W = 0.026, L super(2.646). The species is a predator, feeding mainly on motile Acetes, small fish and Loligo in order of preference.
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干旱区和半干旱区生长的植物具有复杂的生存机制,以确保其能够在特定的环境中生存和发展。植物在干旱的荒漠条件下的生存,与其特殊的种子萌发机制密切相关,这种机制能够确保植物在合适的时间与地点进行种子萌发与幼苗生长发育。在植物的生活史中,种子对极端环境具有最大的忍耐力,而萌发的幼苗对环境胁迫的忍耐程度最小。在干旱区生长的植物往往具有特殊的萌发机制使萌发出的幼苗能够度过对外界的敏感期,对于植物的生存具有重要意义。 毛乌素沙地是我国的四大沙地之一,该地区具有水分短缺,蒸发强烈,风沙剧烈和生境异质性高的特征。本文假设生长在这种极端环境中的植物也发展出了“适时适地”的种子萌发和幼苗生长的适应对策。为了验证以上的假设,本文选取毛乌素沙地不同生境中生长的两种优势固沙禾草——流动沙丘上生长的沙鞭(Psammochloa villosa)和固定沙丘上生长的赖草(Leymus secalinus)为研究材料,通过野外调查、温室控制实验和实验室控制实验的方法,从生理生态学的角度探讨这两种植物的种子萌发和幼苗生长过程对沙丘环境的适应对策,主要对比它们在种子休眠、萌发和幼苗早期生长过程中对沙丘生境适应性的异同点。研究结果表明: (1)新成熟的沙鞭和赖草的种子为适应冬季低温而发展出生理性的内生休眠——非深度生理休眠。沙鞭和赖草的种子分别需要经过4周和8周的低温层积处理(3-5ºC)来完全打破休眠。另外,划破种皮或者部分切除胚乳也能够促进种子的萌发,这进一步证明两种植物的种子具有非深度生理休眠。然而,切除胚乳在不同程度上影响它们的幼苗生长。由非深度生理休眠、温度和损伤种皮/胚乳调节的部分萌发机制能够确保两种植物的种子即使在条件适宜的情况下只有部分种子萌发,从而分散植物生存的风险性。 (2)毛乌素沙地的小量降水(无法触发萌发)使种子经常遭受湿润-干燥的交替胁迫过程。种子先在湿润条件下吸涨1d或者2d,然后在室温下干燥0-8天。尽管在经历反复吸涨和自然干燥脱水后仍能够保持萌发能力,沙鞭和赖草种子的萌发特性却发生了不同的变化:和各自的对照相比,沙鞭种子萌发率相同而萌发速率降低;赖草种子的萌发率和萌发速率都降低,部分种子进入休眠状态。沙鞭和赖草萌发出的幼苗可能由于没有后续降雨或者因沙蚀而遭受干燥胁迫,但是其幼苗在生长早期能够忍耐一定程度的干燥,再次湿润后部分幼苗能够恢复生长。沙鞭和赖草幼苗的耐干燥的“极限点”不同:当幼根长度为1 mm时,它们的幼苗忍耐干燥的时间分别是60d和30d;当幼根长度为4 mm时,它们的幼苗忍耐干燥的时间分别是14d和7d。沙鞭和赖草的种子和生长早期的幼苗的耐干燥性特性可能是它们对降雨量和降雨时间都不可预测的沙地生境的生存策略之一。 (3)不同的沙埋深度影响沙鞭和赖草的种子萌发和出苗。这两种植物的种子萌发和出苗都需1-2 cm的浅层沙埋。随着沙埋深度的增加,两种植物的种子萌发率和出苗率逐渐降低,强迫休眠率逐渐升高;萌发率与出苗率和沙埋深度呈负相关关系而休眠率和沙埋深度呈正相关关系。但是,沙鞭种子出苗的最大沙埋深度是8 cm,而赖草的则为4 cm。因强迫休眠而没有萌发的种子对维持一个长期的土壤种子库来说具有生态学优势,这些种子暴露在合适的萌发土壤深度时具有生长出幼苗的潜能。 (4)沙鞭和赖草的种子都具有大小的差异性,种子大小对沙鞭和赖草的种子在不同沙埋深度的出苗具有不同的影响。沙鞭的三种不同大小种子的平均质量分别为小,4.489 ± 0.012 mg (4 – 4.9 mg);中,5.457 ± 0.012 mg (5 – 5.9 mg)和大,6.415 ± 0.011 mg (6 – 6.9 mg)。赖草的两种不同大小种子的平均质量分别为小,3.083 ± 0.026 mg (3 – 3.5 mg)和大3.955 ± 0.028 mg (3.6 – 4.0 mg)。在相同的沙埋深度下,两种植物的大种子的出苗率都显著高于小种子。和小种子相比,两种植物的大种子由于贮藏更多的能量,所以在相同深度的沙埋中具有出苗率更高的生态优势,而大量小种子在沙埋中不能萌发,可以作为种子库保存在沙层中,这样就分散了一次性大量萌发给植物带来的冒险性。 (5)沙鞭和赖草的幼苗在生长过程中会遭受沙埋,其幼苗忍耐沙埋的能力与沙埋的相对深度(沙埋比例)和幼苗年龄有关。沙鞭和赖草幼苗的耐沙埋能力不同:沙鞭的2周龄幼苗可以忍耐达到株高100%的沙埋,而其1周龄幼苗只能忍耐75%的沙埋。赖草的1周龄和2周龄幼苗都只能忍耐75%的沙埋。沙埋之后,沙鞭和赖草幼苗的生物量,根/茎比以及根和茎的长度都受到不同程度的影响。赖草幼苗不能忍耐完全沙埋可能是限制它在流动沙丘上分布的一个原因。 (6)降雨量和降雨频率能够不同程度地影响沙鞭和赖草在不同沙层的萌发和出苗。这两种植物的种子萌发和出苗需要的最小降雨量不同:在一次浇水相当于5 mm降雨量后,沙鞭和赖草种子的萌发率都超过50%;但是使沙鞭和赖草的出苗率能够达到50%的降雨量分别为10 mm和15 mm。沙埋中的沙鞭和赖草种子的出苗对降雨的响应具有以下特征:两种植物种子的出苗随降雨量或者降雨频率的增加而增加;沙鞭的出苗率受到降雨量和降雨频率的显著影响,但是二者交互作用的影响不显著;赖草的出苗率受到降雨量、降雨频率以及二者交互作用的显著影响。 由非深度生理休眠,种子大小,干燥-湿润循环,沙埋和降雨调节的种子萌发和出苗机制确保了自然条件下沙鞭和赖草每次只有少量种子萌发和出苗,从而分散了两种植物在沙丘上的生存风险。 根据沙鞭和赖草在沙丘上的种子萌发和幼苗生长特性,本文为毛乌素沙地通过植物固沙恢复受损的沙地生态系统的种子飞播实践提出了几点建议。
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The authors thank the anonymous reviewer for helpful comments on the early version of the manuscript. This work was financially supported by the earmarked fund for Modern Agro-industry Technology Research System, the Science Fund for Young Scholars in Sichuan Province (Grant No: ZQ 026-017), and the National 863 Project of China (No. 2008AA101001).
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In order to carry out Biometric studies, 75 samples were caught from 3 locations ( Tajan river, Sefidrud and Shirud) using Salic and the length (±1 mm) and weights (± 5 gr) of samples were determined. Using One-way ANOVA by SPPSS software, there wasn’t significant difference between locations in length and fecondity (P ≥0.01(, but there was significant difference between Shirud and tajan samples with sefidrud in weight ) P≤0.01(. In order to carry out genetic variation studies, 210 fish were caught from 3 different regions of the Iranian coastline (Khoshkrud, Tonekabon, Gorganrud) and 1 region in Azerbaijan (Waters of the Caspian Sea close to Kura River mouth) during 2008-2009 . Genomic DNA was extracted of fin using the phenol-chloroform. The quantity and quality of DNA from samples were assessed by spectrophptometer and 1% agarose gel electro-phoresis. PCR was carried out using 15 paired microsatellite primers. PCR products were separated on 8% polyacrylamide gels that were stained using silver nitrate. Molecular weight calculate using UVTech software. The recorded microsatellite genotypes were used as input data for the GENALEX software version 6 package in order to calculate allele and genotype frequencies, observed (Ho) and (He) expected heterozygosities and to test for deviations from Hardy-Weinberg equilibrium. Genetic distance between two populations was estimated from Nei standard genetic distance and genetic similarity index (Nei, 1972). Genetic differentiation between populations was also evaluated by the calculation of pairwise estimates of Fst and Rst values. From 15 SSR markers were used in this investigation, 9 of them were polymorph. Average of expected and observed heterozygosity was 0.54 and 0.49 respectively. Significant deviations from Hardy-Weinberg expectations were observed in all of location except Anzali lagoon- autumn in AF277576 and EF144125, Khoshkrud in EF144125 and Gorganrud and Kura in AF277576. Using Fst and Rst there was significant difference between locations ) P≤0.01(. According to Fst , the highest population differentiation (Fst= 0.217) was between Gorganrud and Khoshkrud that have the lowest Nm and the lowest (Fst= 0.086) was between Gorganrud and Tonekabon that have the highest Nm. Using Rst the highest population differentiation (Rst= 0.271) was between Tonekabon and spring Anzali lagoon and the lowest (Rst= 0.026) was between Tonekabon and Autumn Anzali 159 lagoon. Also the difference between Spring Anzali lagoon and Autumn Anzali lagoon was noticeable (Fst=0.15). AMOVA analysis with consideration of 2 sampling regions (Iran and Azerbaijan) and 7 sampling locations (Iran: Khoshkrud, Tonekabon, Gorganrud, Spring Anzali lagoon and Autumn Anzali lagoon ; Azerbaijan: the Kura mouth) revealed that almost all of the variance in data namely 83% )P≤0.01( was within locations, Genetic variances among locations was 14% )P≤0.01( and among regions was 3% )P≤0.01(. The genetic distance was the highest (0.646) between Gorganrud and Autumn Anzali lagoon populations, whereas the lowest distance (0.237) was between Gorganrud and Tonekabon River. Result obtained from the present study show that at least 2 different population of Rutilus frissi kutum are found in the Caspian sea,which are including the kura river population and the southern Caspian sea samples and it appears that there is more than one population in southern Caspian sea that should be attantioned in artifical reproduction Center and stoke rebilding.
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活性多糖的研究已成为多糖研究领域内的一个热点.对植物活性多糖的研究范围、重要意义及化学结构与构效关系方面的研究进展进行了综述分析,并对其应用前景作了介绍.
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微生物结皮是荒漠化治理中新的热点之一,但其关键形成生物——微型藻类如何通过群落结构的变化向地衣结皮、藓类结皮转变的机理仍是未知的。本文以时空替代法,将沙坡头流沙,4、8、17、34及42龄结皮当作同一群落演替进程中的6个阶段,通过系统聚类、主分量分析的方法首次对这一问题进行了研究,结果显示该地荒漠藻群落的原生演替朝着蓝藻总丰度和爪哇伪枝藻(Scytonema javanicum)丰度逐渐下降,纤细席藻(Phormidiumtenue)、绿藻、硅藻丰度逐渐增加的方向进行;多样性随群落演替的发展而增高;生物量
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通过生物学与土壤学、矿物学、糖化学和风沙物理学多学科实验方法的综合利用,对强度显著不同的多年老龄荒漠藻结皮、野外人工藻结皮、室内人工藻结皮进行研究,从多方面、多层次揭示了藻结皮胶结机理问题.结果发现强度最弱的室内人工藻结皮中藻体多分布在表面,胞外聚合物含量低,强度维持仅靠藻丝的机械束缚;野外人工藻结皮中大多数藻丝生长在深层,同时分泌更多胞外聚合物,当藻类单位生物量产生1.4倍以上的有机质时,部分胞外聚合物开始聚集结皮,表面低凹处形成一有机质层,使结皮强度提高2.5倍;当该有机质层吸附、截留了一定量尘埃、土
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本发明是一种单模高功率垂直腔面发射激光器,属半导体光电子领域。其特征在于,包括P型电极(1),P型Si衬底(2),金属键合层(3),P型分布布拉格反射镜(DBR)(4),氧化限制层(5),有源区(6),N型DBR(7),SiO2掩膜(8),聚酰亚胺或苯并环丁烯(BCB)(9),N电极(10),光子晶体(11),出光窗口(12)。在该结构的垂直腔面发射激光器中引入光子晶体,可增大氧化孔径,提高单模输出功率,同时采用键合技术将传统VCSEL外延片转移到Si衬底上和采用底部出光的设计,便于拉近VCSEL外延片有源区与Si衬底的距离,改善器件热学特性,进一步提高单模输出功率。
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Cr-doped InAs self-organized diluted magnetic quantum dots (QDs) are grown by low-temperature molecular-beam epitaxy, Magnetic measurements reveal that the Curie temperature of all the InAs:Cr QDs layers with Cr/In flux ratio changing from 0.026 to 0.18 is beyond 400 K. High-resolution cross sectional transmission electron microscopy images indicate that InAs:Cr QDs are of the zincblende structure. Possible origins responsible for the high Curie temperature are discussed.
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Determination of arsenic species by large-volume field amplified stacking injection-capillary zone electrophoresis (LV-FASI-CZE) is reported in this paper. Whole column injection was employed. The optimum buffer pH for the separation of weak acids was discussed. It was found that the optimum buffer to analyze the stacked arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA) was 25 mm phosphate at pH 6.5. However, the optimum buffer to analyze the concentrated arsenite (As(III)) was 20 mm phosphate - 10 mm borate at pH 9.28. The limits of detection of the method developed were 0.026 mg/L for As(III), 0.023 mg/L for As(V), 0.043 mg/L for MMA, and 0.018 mg/L for DMA. An enrichment factor of 34-100 for several arsenic species was obtained. In the end, this method was applied to determine the arsenic concentration in the environmental reference materials to show the usefulness of the method developed.
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调查了沈阳市细河河水及其沿岸地下水水质中石油类和美国环保局(USEPA)"黑名单"上的16种优先控制多环芳烃(PAHs)的有机污染现状,评价细河污染带来的生态风险。结果表明:细河河水中石油类浓度和16种PAHs总浓度范围分别为0.031~1.819mg.L-1和0.026~0.384μg.L-1,平均浓度分别为1.007mg.L-1和0.151μg.L-1;细河沿岸地下水中石油类浓度和16种PAHs总浓度范围分别为0.020~0.987mg.L-1和0.051~0.389μg.L-1,平均浓度分别为0.364mg.L-1和0.133μg.L-1;细河河水和地下水中的石油类污染严重;河水中的PAHs浓度在流经规模较大的城镇或乡镇处出现高值点,苯并(b)荧蒽和苯并(k)荧蒽在河水与地下水中的检出率较高,对水生生态系统健康构成了潜在的威胁。
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In this paper, the water relaxation enhancement behavior of Gd-diethylenetriamine pentaacetic acid(DTPA) in water and in aqueous solution of bovine serum albumine(BSA) has been studied. The T-1 relaxivity of Gd-DTPA in BSA solution is higher than that in aqueous solution. The results indicate that Gd-DTPA can integrate non-covalently with BSA mainly in forms of (Gd-DTPA) . BSA, (Gd-DTPA)(2) . BSA, for which the apparent equilibrium constant is 0.026 mmol(-1).L,0.0018 mmol(-2).L-2 respectively. This method would be used to study the interactivities between protein and contrast agent.
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A poly(4-vinyl)pyridine (PVP)/Pd film electrode was constructed for the electrocatalytic detection of hydrazine. The preparation of the PVP/GC electrode was performed by electropolymerization of the monomer 4-vinylpyridine onto the surface of a glassy carbon electrode. Subsequently, palladium is electrodeposited onto the polymer modified electrode surface. The ion-exchange function of PVP polymer is helpful to this process in view of the tetrachlorapalladate anion. Compared with the Pd/GC electrode, the modified electrode displays a better mechanical stability in a flowing stream. The PVP/Pd film electrode exhibits higher sensitivity when detecting hydrazine with a detection limit of 0.026 ng (S/N=3).
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Heterotrophic culture of microalgae to develop methods of increasing biomass productivity and storage lipids has brought new insight to commercial biodiesel production. To understand the relationship between heterotrophy and lipid production, the effects of carbon sources on the growth and lipid accumulation of Chlorella sorokiniana GXNN01 was studied. The alga exhibited an increased growth rate in response to the addition of carbon sources, which reached the stationary phase after 48 h at 30A degrees C. In addition, glucose and NaAc had a significant effect on the lipid accumulation during the early-stationary phase. Specifically, the lipid content was 0.237 +/- 0.026 g g(-1) cell dry weight and 0.272 +/- 0.041 g L-1 when glucose was used as the carbon source, whereas the lipid content reached 0.287 +/- 0.018 g g(-1) cell dry weight and 0.288 +/- 0.008 g L-1 when NaAc was used as the carbon source. The neutral lipid content was found to first decrease and then increase over time during the growth phase. A glucose concentration of 20 mmol L-1 gave the maximal lipid yield and the optimum harvest time was the early-stationary phase.