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81.
详细研究达拉阶标准剖面的ting化石,计有14属74种及亚种,其中未定种1种,建立6个ting化石带,自下而上依次为:Profusulinella priscoidea-P.parva带,Profusulinella aljutovica-Taitzehoella taitzehoensis extensa带,Fusulinella obesa-F.eopulchra带,Fusulina lanceolata-Fusulinella vozhgalensis带,Fusulina pakhrPnsis-Pseu-dostaffella paradoxa带及Fusulina cylindrica-F,quasifusulinoides带。标准剖面的达拉阶应与国际地层表中的巴什基尔阶上部和莫斯科阶相当。  相似文献   
82.
Dibrachys boarmiae was recently found as a parasitoid of the pistachio twig borer moth, Kermania pistaciella, an important pistachio pest in Iran. Several biological and behavioural aspects of the wasp were studied under controlled conditions using three different lepidopterous host species, K. pistaciella, Sitotroga cerealella and Galleria mellonella. Development time from egg to adult decreases from 54 days at 15°C to 12.6 days at 32.5°C. The thermal constant was estimated 270°D, and the lower development threshold was at 9.9°C. Longevity of females that had the opportunity to oviposit and access to food (honey) was on average 23 days, and 134 offspring were produced during 13 days of oviposition. Ninety percent of ovipositions occur during the first 10 days of the parasitoid's life, although no pre-oviposition period was found. If females were deprived of food, longevity as well as fecundity, were drastically reduced to 8 days and only 79 offspring respectively. Females were able to mate immediately after emergence and the sex ratio of the progeny was strongly female biased on all examined hosts, especially on the largest host G. mellonella (0.08 male). When females were kept with a male throughout their life, the total number of progeny decreased to 92 wasps on average but the sex ratio was unaffected. The parasitoid significantly preferred to attack the pre-pupal stage, and this influenced the size of clutches allocated to different host stages. The parasitoid laid larger clutches on bigger hosts.  相似文献   
83.
早寒武世马哈螺类的骨骼化特征、分类和演化意义   总被引:3,自引:0,他引:3  
马哈螺类(maikhanellids)是已知最古老的单板类,以往缺乏系统研究,并在分类上争议较大,文中以滇东早寒武世梅树村阶微小骨骼化石的丰富材料为依据,详细阐述该类群的形态特征和超微结构,探讨其亲缘关系和演化趋势,研究表明,马哈螺类由6个属组成,包括Maikhanella,Ramenta,Ramentoides gen.nov.,Mediata gen.nov.,Yunnanopleure和Purella。各属之间壳形变化较大,但裸露的壳顶和普遍发育的鳞片状或条状突起表明它们在明显的亲缘关系,并显示两个演化方向,即Maikhanella Ramentoides gen.nov.Ramenta和Maikhanella Mediata gen.nov.Yunanopleura-Purella。马哈螺类分布于梅树村期早,中期,Maikhanella是最原始的马哈螺,最先出现在梅树村阶小歪头山段,也是中谊村段下磷矿层唯一的马哈螺,而在该段上磷矿层马哈螺类发生了明显的属种分异,在大少段所有的马哈螺类突然消失,马哈螺类的壳体曾被描述为:骨针状的外骨骼”,“骨片状外骼”和“包裹在中间基质中的骨针”,但当前研究表明,以Maikhanella pristinis和Ramenta cambrina为代表的马哈螺类的内壳层具有早期单板类中较常见的水平交错纤状结构,指示了马哈螺类具有致密成层的壳壁,文中新建2亚科,2属和5种,即Maikhanellinae subfamily nov.,Purellinae subfamily nov.,Maikhanella Perelegans sp.nov.,Ramenta superata sp.nov.,Ramentoides latispinus gen.et sp.nov.,Mediata kunyangensis gen.et sp.nov.,Yunnanopleura longidens sp.nov。  相似文献   
84.
Translational cancer genomics research aims to ensure that experimental knowledge is subject to computational analysis, and integrated with a variety of records from omics and clinical sources. The data retrieval from such sources is not trivial, due to their redundancy and heterogeneity, and the presence of false evidence. In silico marker identification, therefore, remains a complex task that is mainly motivated by the impact that target identification from the elucidation of gene co-expression dynamics and regulation mechanisms, combined with the discovery of genotype–phenotype associations, may have for clinical validation. Based on the reuse of publicly available gene expression data, our aim is to propose cancer marker classification by integrating the prediction power of multiple annotation sources. In particular, with reference to the functional annotation for colorectal markers, we indicate a classification of markers into diagnostic and prognostic classes combined with susceptibility and risk factors.  相似文献   
85.
寒武纪没有化石苔藓动物的任何记录.最老的、毫无疑问的、真正的苔藓动物,发现于我国峡东地区的下奥陶统特马豆克阶地层中.这类苔藓动物以丰富但多样性低的变口目和少量的隐口目为代表.弗洛期的一些苔藓动物,在北美,英国和波罗的海地区(俄罗斯西北部)已相继发现,这时以Ceramopora?unapensis为代表的泡孔目苔藓动物开始出现,有一定的多样性.中奥陶世初期,苔藓动物迅速崛起,古生代狭唇纲的四个目--变口目、隐口目、泡孔目和管孔目(=环口目)苔藓动物都已经有了代表.由于奥陶纪是苔藓动物发生、演化发展和辐射的重要时期,因此,奥陶纪,特别是早奥陶世苔藓动物的任何新的发现,都有重要的意义.本文描述和解释的一个新的苔藓动物群,发现于安徽滁州琅琊山弗洛阶的红花园组上部.这个苔藓动物群由变口目爱沙尼亚苔虫亚目的两个种:Dianulites hexaporites(Pander),Orbiramus grandis sp.nov.和隐口目翼网苔虫亚目的一个种:Prophyllodi-ctya putilovensis Lavrentjeva组成.尽管这个苔藓动物群在局部地区可能还是低多样性的,但就整个世界范围而言,有一定的多样性,类似于同样以变口目苔藓动物占优势的比林根苔藓动物群,后一苔藓动物群产于波罗的海以东地区(俄罗斯西北部)同时代的地层中.  相似文献   
86.
摘要 目的:探讨血清癌胚抗原(CEA)、C-C基序趋化因子受体3(CCR3)、C-X-C趋化因子配体16(CXCL16)与Ⅰ期非小细胞肺癌(NSCLC)术后复发转移的关系。方法:选取2015年1月~2017年6月南京医科大学附属南京医院收治的186例接受手术切除的Ⅰ期NSCLC患者为NSCLC组,根据术后是否发生复发转移分为复发转移组和未复发转移组,另选取60名健康体检者为对照组。采用酶联免疫吸附法检测血清CEA、CCR3和CXCL16水平,分析其与Ⅰ期NSCLC患者病理特征的关系。采用多因素Cox回归分析Ⅰ期NSCLC患者术后复发转移的影响因素,采用受试者工作特征(ROC)曲线分析血清CEA、CCR3和CXCL16对Ⅰ期NSCLC患者术后复发转移的预测价值。结果:与对照组比较,NSCLC组血清CEA、CCR3和CXCL16水平升高(P<0.05)。血清CEA、CCR3和CXCL16水平与Ⅰ期NSCLC患者肿瘤直径、分化程度和TNM分期有关(P<0.05)。随访5年,失访5例,181例Ⅰ期NSCLC患者术后复发转移为20.99%。多因素Cox回归分析显示,肿瘤直径≥2 cm、低分化、TNM分期ⅠB期和CEA、CCR3、CXCL16升高为Ⅰ期NSCLC患者术后复发转移的独立危险因素(P<0.05)。ROC曲线分析显示,血清CEA、CCR3和CXCL16联合预测Ⅰ期NSCLC患者术后复发转移的曲线下面积(AUC)大于CEA、CCR3和CXCL16单独预测。结论:血清CEA、CCR3和CXCL16水平升高与Ⅰ期NSCLC患者术后复发转移独立相关,血清CEA、CCR3、CXCL16联合预测Ⅰ期NSCLC患者术后复发转移的价值较高。  相似文献   
87.
The effects of both moisture and temperature on the sporulation of an isolate of Beauveria bassiana , highly virulent to the Chagas' disease vector, Rhodnius prolixus , were studied in the laboratory under fluctuating regimes. Quantitative assays for conidial production from funguskilled cadavers from 10-day-old tests showed that recycling was highly dependent on the duration of exposure to high relative humidity (RH). On first-instar larval cadavers, sporulation reached more than 10 5 conidia/nymph under most regimes with a favourable phase combining high humidity (97% RH) and temperatures of 20 or 25 C for at least 12 h/day. Sporulation on third- and fifth-instar nymphs required a longer period (16 h/day or more) of favourable conditions (97% RH and 25 C) per day. The intensity of the conidial production from Rhodnius cadavers was enhanced when diurnal temperatures were high (28 and 35 C). From a vector control standpoint, daily high humidity requirements appear to be a crucial constraint. The recycling ability of B. bassiana on fungus-killed R. prolixus is most likely to contribute to the regulation of this triatomine vector if applications are made during the rainy seasons and in the most favourable habitats.  相似文献   
88.
Infestations of Dendroctonus frontalisZimm. are often observed to enlarge continuously by the colonization of new hosts in a pattern similar to a forest fire. This pattern of infestation growth presents unique problems in quantitatively estimating populations of D. frontalis. Beetle populations on each infested tree in an infestation go through five processes: attack, oviposition, reemergence, survivorship, and emergence. These processes, which have been described mathematically in the literature, each take several days for completion. In order to follow the distribution and abundance of D. frontalis throughout the course of development of a spot, we need a daily estimate of the number of beetles involved in each process on every tree. Since it is not practical to sample each tree daily, we developed a procedure whereby quantitative estimation procedures for within-tree populations were used in combination with the mathematical models for the life processes to produce a daily record of the number of adults successfully attacking trees, the number of eggs oviposited, the number of beetles reemerging, number of beetles surviving within the trees, and the number of beetles emerging. These daily estimates were then summarized for all trees in the spot for the duration of the infestation. The daily record of populations of D. frontalis, used with information on infestation geometry, were suggested to be of value in describing and elucidating several important facets of population dynamics including dispersal patterns within infestations, between tree beetle loss (mortality), and time lags among the various population processes. The information reported can be used to develop simulation models of population dynamics or to validate existing models.  相似文献   
89.
This paper is concerned with mathematical analysis of the critical domain-size problem for structured populations. Space is introduced explicitly into matrix models for stage-structured populations. Movement of individuals is described by means of a dispersal kernel. The mathematical analysis investigates conditions for existence, stability and uniqueness of equilibrium solutions as well as some bifurcation behaviors. These mathematical results are linked to species persistence or extinction in connected habitats of different sizes or fragmented habitats; hence the framework is given for application of such models to ecology. Several approximations which reduce the complexity of integrodifference equations are given. A simple example is worked out to illustrate the analytical results and to compare the behavior of the integrodifference model to that of the approximations.  相似文献   
90.
The Allee effect, a reduction of individual fitness at low population density that can lead to sudden and unannounced extinctions, has been shown to come about through a number of mechanisms, usually associated with group behavior or mate search. Recent papers show that it may arise through size-selective predation, without explicit assumptions relating individual fitness to population density. It arises from the shift that a predator induces in the population stage distribution of its prey. We study the parameter conditions that lead to such an emergent Allee effect. The emergent Allee effect occurs under fairly broad conditions. We show that stage-specific predation can also induce bistability between alternative states where both prey and predator are present. A perturbation analysis on the equilibria shows that all equilibria are highly robust to changes in predator density. Our work shows that when size-specific interactions are taken into account, bistabilities and catastrophic collapses are possible even in purely exploitative food webs, which has substantial implications for questions related to food web theory and conservation issues.  相似文献   
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