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The evolution of genome size has been discussed in relation to the evolution of various biological traits. In the present study, the genome sizes of 22 dictyopteran species were estimated by Feulgen image analysis densitometry and 6-diamidino-2-phenylindole (DAPI)-based flow cytometry. The haploid genome sizes (C-values) of termites (Isoptera) ranged from 0.58 to 1.90 pg, and those of Cryptocercus wood roaches (Cryptocercidae) were 1.16 to 1.32 pg. Compared to known values of other cockroaches (Blattaria) and mantids (Mantodea), these values are low. A relatively small genome size appears to be a (syn)apomorphy of Isoptera + Cryptocercus, together with their sociality. In some phylogenetic groups, genome size evolution is thought to be influenced by selective pressure on a particular trait, such as cell size or rate of development. The present results raise the possibility that genome size is influenced by selective pressures on traits associated with the evolution of sociality.  相似文献   

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The concentrations of aerosols (NH4NO3, (NH4)2SO4 and NH4Cl) and of gases (HCl(g), HNO3(g), NH3(g) were determined by denuder methods under different conditions (in the absence of fog, before, during and after fog events). At this site situated in an urban region, high concentrations of the gaseous strong acids HCl(g) and HNO3(g) are observed. NH4Cl and NH4NO3 aerosols represent a major fraction of the Cl and NO3 aerosols (<2.4 μm)collected by denuders. During a fog event, very high concentrations of SO42− were found in small aerosols, which are attributed to the aqueous phase oxidation of SO2 under the influence of high pH due to the presence of NH3. Differences in SO42− concentrations measured in aerosols (<2.4 μm) and in fog droplets were probably due to mass-transport limitations of the SO2 oxidation. Ammonium sulfate aerosols represent in some cases a significant fraction of the total S present (SO2(g) + SO42−. Soluble aerosols and gases contribute to the composition of fogwater and are released again after fog dissipation.  相似文献   

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测定了酚类、烷基苯类和硝基苯类的12种化学品,以及3个环境水样对剑尾鱼和稀有(鱼句)鲫的96 h LCO,96 h LC50,96 h LC100值.结果表明,剑尾鱼和稀有(鱼句)鲫的幼鱼对化学品和环境水样的敏感性无显著性差异,对于化学品和环境水样,剑尾鱼和稀有(鱼句)鲫是较为理想的毒性试验材料.   相似文献   

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以紫贻贝为受试生物,采用半静态暴露的方式,研究了全氟辛酸(PFOA)在紫贻贝体内的富集特征、器官分布与消除规律.结果表明,紫贻贝可快速富集PFOA,整贝在不同浓度PFOA暴露下,于4~6d达到平衡态,半衰期为0.34~0.44d(约8~10h),生物富集系数(BCFs)为5.10~9.55mL/g.PFOA在紫贻贝鳃和内脏团中的富集作用大于外套膜、性腺和闭壳肌.紫贻贝中PFOA的含量在净化6~9d后趋于空白组水平,主要代谢途径可能为鳃的作用.紫贻贝对PFOA的富集作用与暴露浓度相关,浓度越低,吸收系数和生物富集系数越大.  相似文献   

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Chorionic villus sampling (CVS) was performed on a 40-year-old woman at 9 1/2 menstrual weeks because of advanced maternal age. The direct preparation showed 46,XY,dup(10)(q11.2q23.2). CVS long-term culture and fetal tissue revealed a rare additional abnormality: 48,XXXY,dup(10)(q11.2q23.2). This abnormality represented the major cell line (>85 per cent in 691 cells) in an (XY)/XXY/XXXY/(XXXXY) mosaic (all cell lines presumably bearing the dup(10q); the presence of XY and XXXXY cell lines is uncertain). To our knowledge, this is the first report of trisomy 10q11-q23 and of prenatally detected 48,XXXY in chorionic villi. The mosaic could have resulted from early post-zygotic non-disjunctions in a 46,XY,dup(10q) or 47,XXY,dup(10q) zygote. The results from DNA studies of four polymorphisms, mapped to Xp and Xq, support this theory. The literature on prenatally detected cases with sex chromosome tetrasomy and pentasomy and those with additional autosomal abnormalities is reviewed. The reported case underlines the problem of false-negative findings when only direct CVS preparations are karyotyped.  相似文献   

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Aljustrel mines were classified as having high environmental hazard due to their large tailings volume and high metal concentrations in waters and sediments.To assess acid mine drainage impacted systems whose environmental conditions change quickly,the use of biological indicators with short generation time such as diatoms is advantageous.This study combined geochemical and diatom data,whose results were highlighted in 3 groups:Group 1,with low p H(1.9–5.1)and high metal/metalloid(Al,As,Cd,Co,Cu,Fe,Mn,Ni,Pb,Zn;0.65–1032 mg/L)and SO_4(405–39124 mg/L)concentrations.An acidophilic species,Pinnularia aljustrelica,was perfectly adapted to the adverse conditions;in contrast,teratological forms of Eunotia exigua were found,showing that metal toxicity affected this species.The low availability of metals/metalloids in sediments of this group indicates that metals/metalloids of the exchangeable fractions had been solubilized,which in fact enables metal/metalloid diatom uptake and consequently the occurrence of teratologies;Group 2,with sites of near neutral p H(5.0–6.8)and intermediate metal/metalloid(0.002–6 mg/L)and SO_4(302–2179 mg/L)concentrations;this enabled the existence of typical species of uncontaminated streams(Brachysira neglectissima,Achnanthidium minutissimum);Group 3,with samples from unimpacted sites,showing low metal/metalloid(0–0.8 mg/L)and SO_4(10–315 mg/L)concentrations,high pH(7.0–8.4)and Cl contents(10–2119 mg/L)and the presence of brackish to marine species(Entomoneis paludosa).For similar conditions of acidity,differences in diversity,abundance and teratologies of diatoms can be explained by the levels of metals/metalloids.  相似文献   

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We report on the earliest modern mongooses of Africa, from the late Miocene (ca. 7 Ma) of the hominid locality TM 266, Toros-Menalla, Chad. The material is based on fragmentary dentitions of three individuals. The main diagnostic feature of the Chadian species is the great development of the shear in the carnassials, which distinguishes the Chadian specimens from all extant herpestids except Herpestes and Galerella. In comparison with most extinct and extant Herpestes, the species from Toros-Menalla differs by a markedly smaller size and, depending on the species, relatively more elongated carnassials, more transversely elongated M1 and more reduced p4. On the basis of a great morphological similarity and the absence of significant differences, we assign our material to Galerella sanguinea; the Chadian finding therefore represents the earliest appearance of an extant species of Herpestidae. This record ties the first appearance of the genus to a minimum age of ca. 7 Ma, which is consistent with the estimated divergence date of 11.4 Ma known from the literature for the species of Galerella.  相似文献   

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阳离子絮凝剂P(AM-DAC)的合成、表征及应用   总被引:2,自引:0,他引:2  
以丙烯酰胺(AM)和丙烯酰氧乙基三甲基氯化铵(DAC)为单体,过硫酸钾(KPS)为引发剂,通过水溶液聚合的方法合成了阳离子絮凝剂P(AM-DAC)。探讨了单体配比、单体浓度、引发剂用量、反应时间、反应温度等因素对阳离子聚丙烯酰胺(CPAM)主要性能的影响。实验得出了较佳的反应条件:聚合温度为70℃,引发剂用量为0.16%,单体配比m(AM):m(DAC)=1:8,总单体浓度为20%,反应时间3 h。在上述条件下,所得阳离子聚丙烯酰胺絮凝剂的特性黏数为18.692 4 dL/g,在其加入量为0.003%的条件下处理巡司河污水,上层清液透光率达90.7%,污泥脱水率达89.2%。并对该聚合物絮凝剂的结构和热行为进行了表征。  相似文献   

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从1983~1998年,沿加拿大不列颠哥伦比亚海岸,我们监测了21处大蓝鹭(Ardea herodias)结巢处卵内多氯二苯并-p-二恶英 (PCDDs)、二苯并呋喃(PCDFs) 和多氯联苯 (PCBs)的污染情况。20世纪90年代早期,主要的同类物如1,2,3,7,8-PnCDD、 1,2,3,6,7,8-HxCDD、2,3,7,8-TCDD、2,3,7,8-TCDF、1,2,3,7,8,9-HxCDD 和2,3,4,7,8-PnCDF在纸浆厂分子氯漂白技术被新的漂白技术替代以及氯基酚类木材保存剂和抗木材变色剂的使用被严格地限制之后有显著下降。被捕食的鱼与大蓝鹭卵内污染物水平之间的强正线性回归说明,每天在本地摄食的食物是大蓝鹭暴露于污染物的一个重要路径。从1985年到1991年,在某些栖居地的大蓝鹭卵内所测到的毒当量浓度(TEQs)足以在小鹭体内产生胚胎毒性。尽管PCDD/Fs有所减少,但估计整个80年代有些城市中苍鹭栖居地的毒当量浓度由于多氯联苯的作用而居高不下。  相似文献   

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We describe here the first case of neonatal death due to the hyperornithinaemia, hyperammonaemia, and homocitrullinuria (HHH) syndrome and the first prenatal diagnosis of this disorder in a subsequent pregnancy in this family.  相似文献   

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All species included in the Polysphincta genus-group develop as ectophagous parasitoids of active spiders, killing their hosts prior to pupation. However, little information regarding natural history and ovipositing behavior of most species are available. In this study we inspected 85 webs of Araneus omnicolor to evaluate the frequency of parasitism and host size preferences of the wasp Hymenoepimecis sp. We also described the web characteristics of normal and parasitized spiders and the wasp ovipositing behavior. About 41% of the adult females of A. omnicolor inspected were parasitized. The highest incidence of parasitism was observed among relatively small females while no egg or larva was found in large individuals. Araneus omnicolor builds a strong web composed of an orb and barrier threads, where the spider rests within a curled leaf. The parasitoid larva builds its cocoon within this refuge, and modified cocoon webs were not observed. The ovipositing behavior of Hymenoepimecis sp. was very similar to that of Hymenoepimecis argyraphaga parasitizing Leucauge argyra, including the position of the sting, the killing of a previously attached larva, and the expelling of the egg from the base of the ovipositor.  相似文献   

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For more than a decade, a popular theory amongst scholars of science-policy interactions has been that research is most effective at informing policy and decision-making processes when it is credible, relevant and legitimate (CRELE) with multiple audiences simultaneously. In this paper, we argue that this triad reflects a primarily intra-scientific perspective, rather than the needs and considerations of policy-makers themselves. Using over seventy semi-structured interviews with policy-makers, we present alternative criteria for effective science-policy interactions based on experiences in the urban water sector. We find that applicability, comprehensiveness, timing and accessibility (ACTA) better summarises the most important aspects of scientific research when it comes to influencing decision-making, while finding that CRELE was a poor predictor of policy-maker concerns. Whilst the ACTA quartet effectively gives double-billing to the ‘relevance’ component of CRELE, credibility and legitimacy were much lower priorities for policy-makers interviewed. This article questions whether CRELE is a useful mindset for researchers interested in policy influence. These findings will be of interest to those engaged in debates related to effective science-policy interactions more broadly, and researchers that want to marshal policy influence more specifically.  相似文献   

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