970 resultados para Müller
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尽管多金属氧酸盐 (POMs)的研究已有180多年的历史,但大量的POMs结构在最近几十年才被陆续解析出来[1~4].其中 ,同多钒酸盐由于钒配位几何形状的多样性,结构最为丰富 ,例如:[V4 O12 ]4-[5],[V5O14 ]3-[6],[V10 O2 8]6-[7] ,[V15O4 2 ]9-[8],[V13 O3 4 ]3-[9].值得注意的是,在这些化合物中,钒的化合价均处于最高氧化态+5价.由于+4价钒不易在溶液中(尤其是水中)稳定存在,因此在以往的常压溶液合成中具有混合价态的同多钒酸盐报道很少.与饱和价态的同多钒酸盐相比,混价多钒酸盐具有更为新奇的电荷分布和拓扑学几何构型,并且在 POMs的理论研究和抗病毒药物、电存储材料以及磁性材料等应用领域有特殊的研究和开发价值[1,10,11].因此,制备具有混价的新型同多钒酸盐一直倍受关注.近年来,水热合成技术的引入使同多钒酸盐合成化学迅速发展.水热体系提供了一个特殊的反应环境 [12 ],使制备各种具有混合价态的同多钒酸盐成为可能.Müller等[13]对这一领域开...
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异毛虫科(Paraonidae)和海稚虫科(Spionidae)是环节动物门(Annelida),多毛纲(Polychaeta)中两个常见的科,其成体在海洋生态系统尤其是海洋底栖动物群落中占有重要地位。中国近海异毛虫科和海稚虫科种类极为常见,在潮间带和潮下带均有分布。但由于此两科种类个体小,采集和鉴定困难,在中国一直没有系统的分类学研究。 本论文选择异毛虫科和海稚虫科为研究对象,以中国科学院海洋研究所海洋生物标本馆馆藏的3000余号成体标本为主要研究材料,结合攻读博士学位期间对全国各海域的补充采集标本和从其它单位借用的标本,在认真阅读相关文献和比对某些种类模式标本的基础上,首次对此两科的中国种类进行了全面系统的分类学和地理分布研究。结果如下: 1. 本文记述了中国海域异毛虫科4属18种,其中包括3新纪录种;海稚虫科16属39种,包括7新种,10新纪录种。各鉴定种类均进行了详细的分类学特征描述,并附有形态学结构图。对罕见种类的标本和保存状况较差、光学显微镜无法获得可靠分类学信息的标本进行了扫描电镜观察,并拍摄有电镜照片。 2. 对中国海域有关异毛虫科和海稚虫科种类记录进行了系统的分类学修订,澄清了部分种类特别是一些常见种类分类学研究中存在的错误和混淆。(1)通过大量阅读文献和反复比较检查标本,认为以前我国文献记录的海稚虫科奇异稚齿虫属的奇异稚齿虫Paraprionospio pinnata (Ehlers, 1901)实际包括3种,即扭鳃奇异稚齿虫Paraprionospio inaequibranchia (Caullery, 1914)、枫香树奇异稚齿虫Paraprionospio coora Wilson, 1990和冠奇异稚齿虫Paraprionospio cristata sp. nov.,其中扭鳃奇异稚齿虫和枫香树奇异稚齿虫在中国海属首次记录,冠奇异稚齿虫为一新种。枫香树奇异稚齿虫主要分布于黄海,其分布南界为121°30′ E, 34°30′ N, 扭鳃奇异稚齿虫分布于南海,其分布北界为114°00′ E, 21°45′ N,冠奇异稚齿虫分布区域较广,从长江口到南海的沿岸水域均有分布。奇异稚齿虫是分布在智利、南加利福尼亚、西墨西哥(可能还有安哥拉)的种,在我国海域未见分布。(2)将在我国北方沿海非常常见但长期被记录为鳞腹钩虫Scolelepis (Scolelepis) squamata (Müller, 1806)(海稚虫科)的标本重新鉴定为一个新种,即红纹腹钩虫Scolelepis (Scolelepis) daphoinos sp. nov.;鳞腹钩虫分布于北大西洋和地中海沿岸水域,在我国海域未见分布。(3)明确了中国海Prionospio steenstrupi复合体种类。此复合体所包含的种类在形态上十分相似,分类学研究时极易混淆。在已有的文献记录中,该复合体中国种类包括两种,玛氏稚齿虫Prionospio (Prionospio) malmgreni Claparède, 1870和西沙稚齿虫Prionospio (Prionospio) sishaensis Wu & Chen, 1964。本文将该复合体中国种类修正为5种,分别是包氏稚齿虫Prionospio (Prionospio) bocki Söderström, 1920、开普敦稚齿虫Prionospio (Prionospio) dubia Maciolek, 1985、太平洋稚齿虫Prionospio (Prionospio) pacifica sp. nov.、欢乐稚齿虫Prionospio (Prionospio) paradisea Imajima, 1990和西沙稚齿虫Prionospio (Prionospio) sishaensis Wu & Chen, 1964。现在大多数分类学者认为玛氏稚齿虫是一个不可鉴定种,该种的原始描述可能包括数种,且模式标本已丢失。(4)将中国海记录的矮小离稚齿虫Apoprionospio pygmaea (Hartman, 1961)更正为卡米拉离稚齿虫Apoprionospio kirrae Wilson, 1990;将中国海记录的科氏光稚虫Spiophane kroyeri Grube, 1860更正为深蓝光稚虫Spiophanes fuscatus sp. nov.。 3. 比较研究了中国海域异毛虫科和海稚虫科的区系特点,详细分析了两科中国海种类的组成。认为中国种类在区系组成上属于印度-马来区系,异毛虫科中国海特有种较少,仅2种,占该科中国种数的11%;而海稚虫科中国海特有种较多,共9种,占该科中国种数的23%。中国海异毛虫科种类组成和日本、俄罗斯附近水域的组成较为相似,中国海海稚虫科种类组成和日本、澳大利亚附近水域的组成较为相似。
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河蚬(Corbicula fluminea Müller,1774)是原产自我国及东南亚地区的一种淡水双壳类生物,后随船只的往来传遍了世界各地,是许多江河和湖泊生态系统中的关键物种之一,也是欧美等地河湖中数量最多的外来物种[1-4].河蚬具有惊人的气候和环境适应能力,对外界环境的变化,河蚬不像其他一些水生生物那样从一个生态系统中消失,而是改变自己去适应外界的变化,从而继续生存下去.为此,许多学者对它的地理分布、生态环境、形态结构及生长繁殖等方面做过专门研究.
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双壳类生物其壳体在生长过程中记录了高分辨率的环境信息(年、季,甚至周),同时双壳类生物具有广泛的地理分布,在海洋和淡水生态系统中均有大量种类的存在并广泛地存在于古地层中,双壳类生物这些特点使其成为古气候古环境研究的理想对象。 现生壳体的就位研究就是对特定环境产物(壳体)的一些环境替代指标(碳、氧同位素、微量元素等)的环境意义的标定。根据“将今论古”观点,这些认识不仅仅是对现生生物壳体本身的认识,其基本原理、基本关系都可以用于过去环境的重建。因此可以说,对于现代生物壳体的相关研究是利用双壳类壳体化石识别和提取古气候环境信息的前提和基础。 然而人们对于双壳类的认识还十分有限,尤其是对现代生物壳体的就位分析研究还不是很多。对壳体碳、氧同位素及各种微量元素的气候环境指示意义还存在很大争议,这严重阻碍了利用古生物壳体进行提取古气候环境信息。我们对现代淡水双壳类生物河蚬(Corbicula fluminea Müller, 1774)进行了相关研究,取得了一些成果,获得了一些有意的结论,为利用古河蚬壳体,乃至其他双壳类壳体化石重建古气候古环境奠定了基础,扫除了一些障碍,它们主要包括: 1 河蚬壳体不同断面上碳、氧同位素的差异及其意义 通过对河蚬壳体不同断面上同位素的研究发现:河蚬壳体碳同位素在同一生长环的不同位置不存在显著的差异,并使得壳体碳同位素变化序列在不同断面上同样不存在显著差异,因此在做碳同位素时间序列研究时可以不考虑不同断面差异的问题,而在取样过程中可以通过延长取样的长度来获得足够量的样品进行碳同位素的测定;河蚬壳体氧同位素在同一生长环不同位置上存在差异,而导致氧同位素变化序列在不同断面上也存在差异,因此在进行壳体就位分析研究时,选取不同断面上氧同位素变化序列对研究结果影响较大,存在壳体断面选择的问题。而在取样过程中取样的长度应控制在一定范围内,避免同一生长环上距离较远位置粉末的混合。 壳体最大生长线的断面不仅方便取样分析和获得详细的信息,更重要的是其同位素记录的主要是水体环境信息,所以选取壳体最大生长线的断面进行壳体就位分析研究是合理的。 2 通过河蚬壳体高分辨率同位素组成与气候、环境参数定量对比研究明确了河蚬壳体碳、氧同位素所指示的气候环境意义 将河蚬壳体氧同位素测定值与理论计算平衡值进行对比研究,发现河蚬壳体与水体在氧同位素上达到平衡,但由于河蚬在冬季停止生长(T< 17 ℃ ),壳体对冬季时期水体信息是没有记录的,总的来说河蚬壳体记录了5月—11月左右的水体信息。河蚬壳体与水体在氧同位素上的平衡使得其成为夏季水体信息的良好替代指标。 壳体碳同位素值比预测平衡值偏负。导致壳体碳同位素不平衡的原因主要有动力学分馏作用和新陈代谢作用。动力学分馏发生在CO2的水化和氢氧化过程中,含有12C和16O 的CO2比含有重同位素的CO2活跃,因此在壳体钙化过程中发生氧、碳同位素的同步分馏,可以造成18O 约4‰和13C约10‰ ~ 15‰的亏损,所以动力学分馏使壳体的δ18O和δ13C成一定的正相关关系,并且这种分馏作用主要存在于快速成骨成壳生物中。虽然壳体的碳、氧同位素显示出一定的正相关性,但是由于壳体氧同位素的平衡,表明动力学分馏作用不是壳体碳同位素偏负的主要原因。新陈代谢作用主要是指壳体在形成中利用了呼吸作用产生的富集12C的CO2,其主要影响壳体的碳同位素,对氧同位素的影响很小甚至可以忽略。本研究河蚬壳体碳同位素的偏负及所有壳体碳同位素时间序列均显示出随壳高增大而负向的变化表明新陈代谢作用的影响是壳体与水体之间碳同位素不平衡的主要因素。壳体碳同位素的不平衡现象将导致直接利用其提取水体信息的不准确性。因此能否以及如何将新陈代谢作用对壳体碳同位素的影响排除出去成为壳体碳同位素研究的焦点。 3 河蚬壳体形成中利用新陈代谢产生的二氧化碳比例的室内养殖研究 室内养殖实验发现:随着养殖水体碳同位素的升高,养殖过程中形成的河蚬(样品A和样品B)其壳体碳同位素也随之升高,表明了δ13CDIC对壳体碳同位素的影响。壳体碳同位素值比预测平衡值偏负,这主要是由于壳体在形成过程中新陈代谢作用产生的二氧化碳的参与造成的。根据计算,壳体A在实验中沉淀部分壳体利用新陈代谢碳的比例(M值)为24%~43%,平均值为33%;壳体B为33%~75%,平均值为58%。M值随生物的生长呈下降变化,这与先前的一些研究认为M值随生物的生长呈升高变化并不一致,这说明在实验中河蚬主要是通过增加对DIC的吸收和利用来满足壳体对物质量增加的需求,而造成这种现象的原因可能是由于室内养殖环境变化情况与野外存在显著差异。个体差异以及室内养殖条件与野外情况的区别使得无法将δ13Cmeta对壳体的影响分离出去,因此只有通过对大量野外河蚬个体进行研究才能判断出是否可以以及如何将新陈代谢作用对壳体碳同位素的影响排除。 4 花溪地区河蚬壳体利用新陈代谢产生的二氧化碳比例的研究 生物软体碳同位素(δ13Ctissues)可以用来替代生物新陈代谢作用产生的碳的同位素(δ13Cmeta)组成,因此对河蚬δ13Ctissues进行了相关研究。花溪地区河蚬软体的个体样品与若干壳高接近的混合样品在有机碳同位素(δ13Ctissues)上差别很小,说明壳高大小接近的河蚬个体,软体有机碳同位素之间的差异很小,因此在进行相关研究中不需要对每一个河蚬个体都进行软体碳同位素的测定。不同大小个体之间δ13Ctissues 存在一定的差异,表现出随着壳高的增大,δ13Ctissues 先降低后增高的变化趋势, 可能表明河蚬在生长过程中其食性会发生一定的变化。经过盐酸处理的样品与未处理的样品在δ13Ctissues 上并未显示出显著的差异,这说明样品中无机碳酸盐岩的含量很低,因此对δ13Ctissues 的测定影响很小,因此以后在处理相同样品时可以省去加盐酸这一步骤。河蚬与河蚌在δ13Ctissues 十分接近,而田螺与二者差异显著,这说明同为双壳类的河蚬和河蚌在食性上比较一致,并且与腹足类的田螺存在明显的不同。 河蚬壳体碳同位素组成与壳高显示出显著的负相关关系,这主要是由于生物新陈代谢作用的结果。因此,壳体碳同位素组成与壳高之间负相关关系可以看做是碳同位素生命效应存在的一种指示剂。 花溪地区河蚬壳体利用新陈代谢碳的比例,M值变化范围为19.8% ~26.8%,平均值为22.6 %± 2.5,并且M值与壳高具有显著的正相关性,M = 0.39H + 17.36(n = 18, R2 = 0.74),这与对很多野生壳体的研究结果是一致的。不同物种之间以及同种生物在不同地区之间,M与壳高的回归方程是不同的,但就花溪地区而言,新陈代谢作用对壳体碳同位素组成的影响利用上述回归方程是可以去除的,从而实现利用古河蚬壳体提取古水体信息的目的。因此利用现代壳体建立M与壳高之间的回归方程是利用古壳体化石提取水体信息的前提和基础。 5壳体碳同位素对不同环境条件的记录的室内养殖研究 不同养殖水箱中(不同的饲养环境),河蚬壳体碳同位素组成存在较大差别,这种差别主要是由于喂养的食物在碳同位素组成(控制水体碳同位素)上存在较大差别造成的。虽然壳体碳同位素组成记录的不是水体δ 13CDIC绝对值的变化,但它反映了不同环境中水体信息的差异和变化趋势,因此壳体碳同位素可以用作δ 13CDIC定性的替代指标,另外壳体碳同位素还可以用来区分来源不同的种群或个体,而这对于鉴定生物属种、判断来源和反演古环境都是十分有意义的。 实验中河蚬壳体与无机成因文石相比, 碳同位素组成平均偏负6.16 ‰,证明了生物新陈代谢影响的存在,这一恒定分馏值的出现主要反映了实验中壳体样品数量和大小分布问题,而不能说明河蚬壳体碳同位素是水体δ 13CDIC的定量替代指标。
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2007
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2008
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2008
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Modified nucleosides have been characterized as tumor markers for a number of malignant diseases. In order to use these markers in children, the age-dependence of the nucleoside levels in healthy children has to be established and taken into account in diagnostic decisions. In this study, the levels of 12 normal and modified nucleosides in urine of 166 healthy children and adolescents with an age between 1 day and 19 years are determined by reversed-phase HPLC, and age-dependent reference ranges are defined. The urinary nucleoside concentrations are related to the creatinine concentrations, which allows the use of randomly collected urine samples. All nucleoside levels in urine of children decrease with age, most pronounced during the first 4 years of life, and the age-dependence of the reference values of the individual nucleosides can be approximated by a mathematical function y = b(0) + b(1) (1/x) with the regression coefficients b(0) and b(1), the nucleoside levels y and the age x between 1 year and 19 years. In the very young children, the shifts in the nucleoside concentrations are more differentiated. Starting with low levels on the first day of life, the concentrations of all studied nucleosides rise up to an age of 1-2 months, when they reach their absolute maximum for all age periods, and then decrease. (C) 2004 Elsevier B.V. All rights reserved.
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The atom pencil we describe here is a versatile tool that writes arbitrary structures by atomic deposition in a serial lithographic process. This device consists of a transversely laser-cooled and collimated cesium atomic beam that passes through a 4-pole atom-flux concentrator and impinges on to micron- and sub-micron-sized apertures. The aperture translates above a fixed substrate and enables the writing of sharp features with sizes down to 280 nm. We have investigated the writing and clogging properties of an atom pencil tip fabricated from silicon oxide pyramids perforated at the tip apex with a sub-micron aperture.
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The first calculation of triangular flow ν3 in Au+Au collisions at √sNN = 200A GeV from an event-by-event (3 + 1) d transport+hydrodynamics hybrid approach is presented. As a response to the initial triangularity Ie{cyrillic, ukrainian}3 of the collision zone, ν3 is computed in a similar way to the standard event-plane analysis for elliptic flow ν2. It is found that the triangular flow exhibits weak centrality dependence and is roughly equal to elliptic flow in most central collisions. We also explore the transverse momentum and rapidity dependence of ν2 and ν3 for charged particles as well as identified particles. We conclude that an event-by-event treatment of the ideal hydrodynamic evolution startingwith realistic initial conditions generates the main features expected for triangular flow. © 2010 The American Physical Society.
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During Franz Schubert’s penultimate year of 1827, he produced two profoundly important and mature works that are the focus of this recording project. The works are, in chronological order: • Winterreise (cycle of 24 songs on the poetry of Wilhelm Müller, 1794-1827) • Piano Trio in Eb Major, Op. 100, D. 929 A unique feature of the project is to present Winterreise in two poetic orders: as traditionally performed and published by Schubert, and in the final ordering published by the poet. The program notes accompanying the dissertation’s three compact discs have extensive information as well as comparative tables of Müller’s and Schubert’s final ordering of the cycle. There are significant differences in ordering, and ultimately the listener will determine which is more dramatically satisfying. Dark melancholy is the central emotion in Winterreise, which Schubert composed at various times throughout 1827 in a mood of corresponding gloom and distress. By contrast, the summer and fall of that year produced, in quick succession, the two glowing and remarkable Piano Trios in Bb and Eb, the second of which is included on these compact discs. The contrast between the trios and Winterreise follows the outward circumstances of Schubert’s life and health, a pattern of sorrow and later consolation and elation. The sound recordings for this dissertation recording project are available on three compact discs that can be found in the Digital Repository at the University of Maryland (DRUM). Winterreise was recorded in August 2009, at the University of Baltimore recital hall in Baltimore, Maryland with University of Maryland Professor François Loup. The trio, recorded in live performance in Baltimore in the spring of 2010, features two members of the Baltimore Symphony Orchestra: Qing Li, B.S.O. principal second violin, and Bo Li, B.S.O. section cellist.
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El estudio de la matemática permite la modelización de situaciones que conducen a la resolución de problemas. Por esto, es primordial que los estudiantes analicen los cambios que ocurren en diferentes fenómenos biológicos, económicos y sociales. Sin embargo, durante la escuela media, no se favorece demasiado el desarrollo del pensamiento y lenguaje variacional, base para la comprensión de los conceptos de la matemática de la variación y el cambio, es decir el cálculo. Por este motivo, este trabajo, enmarcado en el proyecto de investigación “Pensamiento y lenguaje variacional: bases para la construcción de conceptos del cálculo diferencial”, tiene como objetivo el análisis y valoración de los resultados obtenidos en una experiencia de aula centrada en el diseño, implementación y corrección de una guía de actividades que indaga las nociones que tienen los alumnos que ingresan al nivel universitario con respecto a variables, cambios, funciones, imagen, gráficas, expresión analítica, valor numérico y comportamiento de funciones.
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En el ámbito de la investigación en Matemática Educativa son conocidas las dificultades que plantean la enseñanza y el aprendizaje de contenidos del cálculo. En la búsqueda de alternativas que favorezcan un desarrollo adecuado de métodos de pensamiento propios de la matemática, diseñamos y pusimos a prueba una secuencia didáctica para la introducción del concepto de derivada. Consideramos como hipótesis básica que el desarrollo de ideas variacionales puede propiciar una mejor comprensión y apropiación de esta noción, adoptando la posición de que el manejo de sistemas de representación es fundamental para la actividad cognoscitiva del pensamiento. Presentamos algunas de las actividades trabajadas en clase y un breve análisis sobre su implementación y las respuestas de los alumnos.
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Satellite-derived remote-sensing reflectance (Rrs) can be used for mapping biogeochemically relevant variables, such as the chlorophyll concentration and the Inherent Optical Properties (IOPs) of the water, at global scale for use in climate-change studies. Prior to generating such products, suitable algorithms have to be selected that are appropriate for the purpose. Algorithm selection needs to account for both qualitative and quantitative requirements. In this paper we develop an objective methodology designed to rank the quantitative performance of a suite of bio-optical models. The objective classification is applied using the NASA bio-Optical Marine Algorithm Dataset (NOMAD). Using in situRrs as input to the models, the performance of eleven semi-analytical models, as well as five empirical chlorophyll algorithms and an empirical diffuse attenuation coefficient algorithm, is ranked for spectrally-resolved IOPs, chlorophyll concentration and the diffuse attenuation coefficient at 489 nm. The sensitivity of the objective classification and the uncertainty in the ranking are tested using a Monte-Carlo approach (bootstrapping). Results indicate that the performance of the semi-analytical models varies depending on the product and wavelength of interest. For chlorophyll retrieval, empirical algorithms perform better than semi-analytical models, in general. The performance of these empirical models reflects either their immunity to scale errors or instrument noise in Rrs data, or simply that the data used for model parameterisation were not independent of NOMAD. Nonetheless, uncertainty in the classification suggests that the performance of some semi-analytical algorithms at retrieving chlorophyll is comparable with the empirical algorithms. For phytoplankton absorption at 443 nm, some semi-analytical models also perform with similar accuracy to an empirical model. We discuss the potential biases, limitations and uncertainty in the approach, as well as additional qualitative considerations for algorithm selection for climate-change studies. Our classification has the potential to be routinely implemented, such that the performance of emerging algorithms can be compared with existing algorithms as they become available. In the long-term, such an approach will further aid algorithm development for ocean-colour studies.
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The authors present here a list of 32 mosses belonging to 15 families: Brachytheciaceae, Cryphaeaceae, Entodontaceae, Hedwigiaceae, Hypnaceae, Leptodontaceae, Meteoriaceae, Neckeraceae, Pilotrichaceae, Polytrichaceae, Pterobryaceae, Racopilaceae, Rigodiaceae, Stereophyllaceae, and Trachypodaceae, all collected in the mountainous forests of the Yungas of the NW of the Argentina (Jujuy, Salta, Catamarca and Tucumán provinces), and also in the rainforests from the NE of the country (Misiones province). Eight species: Atrichum polycarpum, Chrysohypnum elegantulum, Pilosium chlorophyllum, Pilotrichella flexilis, Porotrichodendron lindigii, Pseudotrachypus martinicensis, Steerecleus scariosus, and Thamnobryum fasciculatum are new records for the bryologic flora from Argentina. Braunia imberbis and Squamidium brasiliense are two new records for the bryophytic flora of the Catamarca province; Porotrichodendron superbum is new for the Salta province, while Forsstroemia coronata is the first record for the Catamarca and Jujuy provinces. Aerolindigia capillacea, Braunia reflexifolia, Chryso-hypnum diminutivum, Meteorium deppei and Meteoridium remotifolium are five new citations for the Jujuy province, and Schoenobryum concavifolium is new for the bryophytic flora of the Misiones province. Many studied species occur more frequently in the Yungas than in the NE rainforests; others show separated distribution but live in both areas, the Yungas and Paranaense area, and others are more or less restricted to the Paranaense rainforest of the NE of Argentina. The taxonomy of species is updated, and comments are included on bibliographical precedents, ecology and chorology of each taxon.