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101.
Ichnology and sedimentology of a tide‐influenced delta in the Ordovician from the northeastern Alborz range of Iran (Kopet Dagh region) 下载免费PDF全文
Aram Bayet‐Goll Carlos Neto de Carvalho 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2016,49(3):327-350
The Middle–Late Ordovician Ghelli Formation in the Kopet Dagh region northeastern Alborz range of Iran is composed of siliciclastic rocks deposited in a variety of turbidite to marginal marine environments (deep marine clastic fan and related environments and prodelta, distal delta front, proximal delta front and distributary channels). The ichnology of the middle member of the Ghelli Formation is here reported. Combined sedimentological and ichnological analysis allows recognition of a tide‐influenced deltaic succession in the middle member of the Ghelli Formation consisting of three main facies associations: lower distributary channels, delta front and prodelta facies. Twenty‐two ichnogenera have been identified in this marginal marine succession: Arenicolites, Arthrophycus, Bergaueria, Chondrites, Conichnus, Cruziana, Cylindrichnus, Didymaulichnus, Diplichnites, Diplocraterion, Helminthopsis, Gyrochorte, Lockeia, Macaronichnus, Monomorphichnus, Palaeophycus, Planolites, Rosselia, Rusophcus, Skolithos, Teichichnus and ?Scolicia. Their distribution is clearly linked with lithofacies and depositional palaeoenvironments. The ichnological analysis reveals that the trace fossil suites developed in these environments indicate low diversity and low to moderate abundance of burrows, poor development of tiering and sporadic distribution. Low ichnodiversity and low bioturbation intensities with higher bioturbation clusters consist of facies‐crossing ichnogenera, and the impoverishment of suspension‐feeding trophic types indicates ‘stressed’, non‐archetypal expression of the Cruziana ichnofacies. The periodic higher intensities of bioturbation due to variations in hydrodynamic regimes of tidal currents reflect the archetypal of the Cruziana ichnofacies (and rare Skolithos ichnofacies). 相似文献
102.
Examining the link between dietary specialization and foraging modes of stream‐dwelling brown trout Salmo trutta 下载免费PDF全文
The aim of this study was to explore differences in dietary specialization across two foraging modes (benthic v. surface‐drift foraging) of stream‐dwelling brown trout Salmo trutta. The degree of inter‐individual niche variation within each foraging mode was high, but the dietary specialization was maintained between foraging modes. This study supports the view that if aquatic invertebrates are more abundant and accessible than surface prey, the individuals will not specialize on surface prey (surface‐drift foraging). 相似文献
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雄性麋鹿的吼叫行为、序位等级与成功繁殖 总被引:14,自引:1,他引:14
为探讨雄性麋鹿(Elaphurus davidianus)的吼叫行为与序位等级的关系,以及这种关系在成功繁殖中的作用。2000年7-8月,在北京麋鹿苑选定12头成体雄鹿,用目标取样法观察记录每头鹿的吼叫、圈群和交配行为的发生频次。用有效比值[被雌鹿接受的频次/雄鹿圈群(或交配)的总频次]来衡量雄鹿圈群行为(或交配行为)的有效性。依据雄鹿在发情期的表现状态,把雄鹿归为3类:占有雌鹿群的“群主”(4头)、未占有雌鹿群而挑战“群主”的“挑战者”(5头)和远离繁殖群的“单身汉”(3头)。不同序位等级雄鹿的吼叫频次、圈群(或交配)行为频次、圈群行为(或交配行为)的有效值存在显著差异(P<0.05)。对吼叫行为的分析表明:“群主”吼叫频次最高,“单身汉”吼叫频次最低。“群主”的有效值最高,“单身汉”的有效值最低。据此认为雄性麋鹿的吼叫行为与其序位等级密切相关,而序位等级又决定了雄鹿参与繁殖的机会。此外,还记录到占群雄鹿的警戒吼叫,这是对Wemmer et al.(1983)警戒吼叫行为仅见于雌鹿的观察结果的补充。 相似文献
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Graça Soveral Catarina Prista Teresa F. Moura Maria C. Loureiro‐Dias 《Biology of the cell / under the auspices of the European Cell Biology Organization》2011,103(1):35-54
In yeast, the presence of orthodox aquaporins has been first recognized in Saccharomyces cerevisiae, in which two genes (AQY1 and AQY2) were shown to be related to mammal and plant water channels. The present review summarizes the putative orthodox aquaporin protein sequences found in available genomes of yeast and filamentous fungi. Among the 28 yeast genomes sequenced, most species present only one orthodox aquaporin, and no aquaporins were found in eight yeast species. Alignment of amino acid sequences reveals a very diverse group. Similarity values vary from 99% among species within the Saccharomyces genus to 34% between ScAqy1 and the aquaporin from Debaryomyces hansenii. All of the fungal aquaporins possess the known characteristic sequences, and residues involved in the water channel pore are highly conserved. Advances in the establishment of the structure are reviewed in relation to the mechanisms of selectivity, conductance and gating. In particular, the involvement of the protein cytosolic N‐terminus as a channel blocker preventing water flow is addressed. Methodologies used in the evaluation of aquaporin activity frequently involve the measurement of fast volume changes. Particular attention is paid to data analysis to obtain accurate membrane water permeability parameters. Although the presence of aquaporins clearly enhances membrane water permeability, the relevance of these ubiquitous water channels in yeast performance remains obscure. 相似文献
109.
构建高产谷胱甘肽啤酒酵母基因工程菌提高啤酒抗老化能力的研究 总被引:4,自引:1,他引:4
根据同源重组的原理,将来源于啤酒酵母工业菌株G03的γ-谷氨酰半胱氨酸合成酶基因(GSH1)和筛选标记Kan取代质粒pRJ-5中18S rDNA内部约340bp的DNA片段,构建重组质粒pRKG。以pRKG为模版,PCR得到以18S rDNA为整合位点包含GSH1和Kan的基因片段18S rDNA::(Kan-GSH1)。用此片段转化啤酒酵母工业菌株G03,通过G418抗性筛选得到啤酒酵母工程菌。实验室小试表明,工程菌的谷胱甘肽含量比受体菌株提高16.6%,啤酒的抗老化能力得到了显著提高,而常规指标没有发生显著变化。连续传代5次后胞内GSH含量基本不变遗传稳定性良好。由于表达γ-谷氨酰半胱氨酸合成酶的基因来源于受体菌株自身,是通过自克隆技术改造工业啤酒酵母的一次有益的尝试。 相似文献
110.
Cooperation of Aspergillus nidulans enzymes increases plant polysaccharide saccharification 下载免费PDF全文
Robson Tramontina Diogo Robl Gabriela Piccolo Maitan‐Alfenas Ronald P. de Vries 《Biotechnology journal》2016,11(7):988-992
Efficient polysaccharide degradation depends on interaction between enzymes acting on the main chain and the side chains. Previous studies demonstrated cooperation between several enzymes, but not all enzyme combinations have been explored. A better understanding of enzyme cooperation would enable the design of better enzyme mixtures, optimally profiting from synergistic effects. In this study, we analyzed the cooperation of several enzymes involved in the degradation of xylan, glucan, xyloglucan and crude plant biomass from Aspergillus nidulans by single and combined incubations with their polymeric substrate. Positive effects were observed between most enzymes, although not always to the same extent. Moreover, the tailor made cocktails formulated in this study resulted in efficient release of glucose from plant biomass. This study also serves as an example for the complex cooperation that occurs between enzymes in plant biomass saccharification and how expression in easily‐accessible hosts, such as Pichia pastoris, can help in revealing these effects. 相似文献