重庆老龙洞二叠系-三叠系界线地层微生物岩研究

The largest mass extinction in the Phanerozoic happened at the end of the Permian. The microbialites formed in the extreme environments after the mass extinction has become a hotspot for geologists and paleontologists throughout the world. The dendroid microbialites that were described for the first time in 1999 from the Permian-Triassic boundary section at Laolongdong, Chongqing, have been studied by many geologists from China and overseas. Two important viewpoints about their origin have been proposed. Some researchers believed that they resemble Quaternary travertine shrubs in form, and may belong to microbialites. Some other researchers proposed that the dendroid structure is composed of clots formed by coccoidal cynaobacteria, and is microbialite. Our detailed survey on the section reveals that: (1) there is an interval of speckled “microbialite” in the section, and it underlies the dendroid “microbialite”, (2) the dendroid “microbialite” does not always have dendroid appearance; they are dendroid only in very local places; they are not dendroid in most places; for this reason, they are not comparable to recent tufa; (3) the volume of the dendroid structure greatly increases toward the top of the dendroid microbialite interval: accounting to 70% of the whole rock in the top part. This distribution pattern implies that the formation of this structure may be related to downward migration of the diagenetic fluid. Examination of thin sections reveals that the dendroid structure or point-like structure in the “microbialite” look as lighter areas in the thin sections and are composed of large blocky clear calcites containing scattered yellow dirty small calcite rhombi and irregular “points” of relict lime mudstone or wackestone or packstone. Their formation is by any one of the following two processes: (1) dissolution → filling of large blocky calcite; (2) dolomitization → dedolomitization → dissolution by meteoric fresh water → filling by large blocky calcites. It has been found that there are at least two sea-level falls during the P-T transition. As the sea level fall, the carbonate deposits came into supratidal environment, and suffered dolomitization caused by evaporative fluid or mixing water of sea water and meteoric water. Since the fluid migrated downward from the top of the deposits and in random pathway, the dolomitization formed dendroid or speckled dolomitic areas. As the deposits came into subaerial environments, the meteoric fresh water migrated along the dendroid or speckled dolomitic area with higher porosity, and dissolution happened, which caused the rock became spongy or alveolate. In later time, after the strata came into phreatic zone, large clear blocky calcites grew in and filled the pores in the spongy areas. The dendroid and speckled structure were formed in this way, rather than composed of clots formed by coccoid cyanobecteria. The microbial fossils in Laolongdong section include two types. The first is the tube-like cyanobecteria in middle Bed 3, which are generally less than 1 mm in length, taper toward one end, and are internally filled by microspars. They are straight or sinuous, with micritic wall 0.005~0.01 mm thick. Since this kind of microbial fossils are abundant in middle Bed 3, this rock belongs to microbialite. The second type occurs in Bed 5 and lower and middle Bed 6. They are irregular globular in shape, generally 0.2 ~ 0.5 mm in size, with several outward progresses, and internally filled by one layer of needle-like calcite cements on the wall and the large blocky calcite in the inner space. According to their shape and preservation way, it is inferred that this kind of fossils were formed from some kind of bacterial colony. The bacterial colony may be cuticle in composition, since it has some hardness as it is indicated by its resistance to deposit loading. These organisms discomposed during diagenetic time, and formed good porosity. In later diagenetic time, these pores were firstly cemented by needle-like calcites and later filled by large blocky calcites. So, the bacterial colony promoted the formation of dendroid and speckled structures. However, they did not always form such structures. On the other hand, even though no bacterial colony or other microbes or any kind of fossils were present, dendroid or speckled structures can form. Bed 4 of Laolongdong section contains abundant gastropods but no microbial fossils, and is not microbialite, even though it is speckled. The top of Bed 6 is dendroid, but contain no microbial fossils, and is not micrbialite.

硒、锌同位素MC-ICP-MS分析方法研究及其在生物和环境样品中的应用

一定元素的同位素组成被认为是该元素特有的“指纹”，同位素组成测量是地球化学、生命科学、环境化学、地质科学和核科学等领域重要的研究手段。利用同位素技术开展生命过程，地球系统中的物理、化学、生物过程及其资源、环境与灾害效应，资源勘探，污染物溯源等方面的研究，既是该技术的前沿研究主题，也使相关领域的研究更加“精细量化”，从而在新的科学纵深揭示出更加清晰的规律。 1992年多接收电感耦合等离子体质谱仪(MC-ICP-MS)的问世，为同位素分析提供了一种强有力的技术手段，与传统的热电离同位素质谱相比，MC-ICP-MS具有测量速度快、操作简便、灵敏度高等优点。而且，由于等离子体源产生的高温，在理论上能测量所有的金属元素和一些非金属元素，并已很好地解决了一些高电离电位元素同位素测量的难题（如Se, Zn, Hf等），用MC-ICP-MS准确、精密测量各种元素同位素组成的方法正在逐渐得到发展和完善。目前，MC-ICP-MS比较成熟的方法主要是针对核和地质科学研究中应用较多的U, Pb, Sm, Nd, Sr, Hf, B, Li等，在硒和锌同位素测量方法学的研究还相对较少（尤其是硒），对一些测量中受各种干扰较为严重的、原子量小于80 的元素同位素的测量技术还有待进一步深入探索和研究。锌、硒元素不仅与人类健康息息相关，而且随着质谱分析技术的发展，使其在环境地球化学、生命科学等领域有着广泛的应用前景。准确测量生物、食品、环境、地质等样品中的锌、硒元素含量、各种形态及其同位素组成受到越来越多的关注。锌、硒同位素准确测量的方法学研究，不仅可以广泛应用于各相关领域，也为锌和硒同位素基、标准物质研制奠定技术基础，从而为锌、硒元素含量和同位素测量提供量值溯源保障。 本工作针对锌和硒元素同位素组成以及生物、环境等样品中成分量准确测量存在的问题，通过使用六极杆碰撞室MC-ICP-MS进行准确测量锌和硒元素同位素的技术研究，结合在化学计量研究中的长期实践及相关文献，从方法学角度和应用方面得出以下结论： 1.MC-ICP-MS仪器测量主要参数，如炬管轴向位置、载气流量、碰撞气流量、仪器稳定性等对测量结果影响很大，要获得高精度的测量结果，须优化和固定参数设置，保持仪器的稳定状态。在六极杆碰撞室MC-ICP-MS测量锌同位素时，高纯氩气碰撞气模式是较为理想的模式，64Zn/66Zn、67Zn/66Zn、68Zn/66Zn同位素丰度比测量精度达到0.002－0.008％，70Zn/66Zn 测量精度达到0.01％；在高纯氢气和氩气碰撞气按一定比例混合的模式下， 76Se/80Se、77Se/80Se、78Se/80Se、82Se/80Se同位素丰度比测量精度达到0.004－0.005%。 2.采用高纯、高浓缩64Zn和66Zn配制了8个校正样品 (64Zn/66Zn：0.6－2.2)；用高纯、高浓缩同位素76Se和82Se配制了16个校正样品（76Se/82Se： 0.05－11.8），用这些样品分别测量并计算了仪器系统误差校正系数K，这些校正样品的K64/66 和 K76/82的相对标准偏差分别为0.034％和0.03％，均在仪器的测量不确定度范围内，说明在校正样品同位素变化范围内，仪器测量同位素丰度比的校正系数没有发生明显变化。 3.在硒同位素丰度比值测量中，氢气碰撞气的使用是SeH产生的重要原因之一，Ar/H在2－7之间都可以满足硒同位素比值测量的要求，即保证较高的硒灵敏度、较小的SeH生成比例、稳定的同位素比值测量结果。本工作建立了SeH的校正计算公式，在对测量结果的质量歧视进行校正时，77Se和78Se的校正更为复杂，因为它们除自身产生的SeH外，还分别受到了来自76SeH和77SeH的影响，故校正质量偏移时应首先对SeH进行校正。对于不同的SeH生成比例，经过校正后，硒的同位素丰度比校正值是一致的，并不受SeH生成比例变化影响。 4.通过对IDMS过程中的关键技术研究，明确了如何正确使用该方法以获得准确测量结果。IDMS方法在测量步骤中引入的不确定度影响因素相对于其它化学分析方法较少，并且可以被明确地表达出来，测量结果可直接溯源到国际单位，因此，该方法对化学计量学研究具有十分重要的意义。 5.建立了适用于ICP-MS测量血清、大豆粉、金枪鱼等多种复杂基体中锌和硒元素的样品前处理方法，建立了锌和硒的ICP-IDMS测量方法。将建立的方法应用于人血清标准物质研制、国家计量院之间的国际比对和合作研究中，取得的优异成绩验证了所建方法的可靠性和可比性。IDMS方法在样品前处理上不怕样品损失和高精度同位素丰度比测量的优点，使其在复杂基体中硒、锌的准确测量方面较其它分析方法具有独特的优势，可在生物、临床、环境、食品等方面的分析研究中广泛应用。

月表热参数模型与月壤厚度的被动微波遥感理论分析

利用被动微波遥感亮度温度数据反演月壤厚度是“嫦娥”探月工程的科学目标之一，也是人类探测月壤厚度的一种新的尝试。深入研究月表太阳辐射、月球内部热流以及月表温度的分布和变化规律，是解译遥感数据，反演月壤厚度的前提条件，也为进一步开展月球探测、开发利用月球资源乃至建立月球基地相关研究工作提供必要的参考。 本文根据月表有效太阳辐照度与太阳常数、日月距离和太阳辐射入射角的关系，建立了月表有效太阳辐照度的实时模型如下： (1) 其中， (2) (3) 通过对月表有效太阳辐照度实时模型的各个参数分析发现，影响月表有效太阳辐照度变化的主要因素是日地距离和太阳辐射入射角的变化。对模型的误差分析表明，从1950年到2050年的100年内，月表有效太阳辐照度计算结果的误差百分比小于0.28％，能更准确地反映月表有效太阳辐照度的变化情况。从2007年月表有效太阳辐照度的计算结果发现，该年内的月表有效太阳辐照度变化在1321.5～1416.6 W•m-2之间，平均为1368.0 W•m-2，一个月内的变化最小幅度为6.0 W•m-2，最大幅度为23.6 W•m-2。 在月表有效太阳辐照度的实时模型基础上，根据能量守恒和Stefan-Boltzmann定律，本文还得出了月表温度分布模型如下： (4) 其中，初始条件由下式决定， (5) 通过与月表温度实际观测结果的比较发现，当月表反射率、热发射率和热惯量分别取0.127、0.94和125 J•m-2•s-1/2•K-1时，模型的计算结果与实际观测值比较符合，能较好地预测理想条件下的月表温度。 月表热参数研究的一个重要应用就是解译对月被动微波遥感的亮度温度数据。在对月被动微波遥感探测中，辐射计获得的亮度温度反映了月球表层的热辐射特性。月球表层的热辐射与其自身的热状况紧密相关，结合文中建立的月表热参数模型，根据辐射传播理论进一步分析了对月微波遥感探测中，月球表层在不同情况下对亮度温度的贡献，确定了亮度温度随月表温度和月壤厚度的变化关系，对被动微波遥感探测月壤厚度的可能性和可能达到的精度进行了估算。 对月球表层的热辐射传播的分析发现，对月被动微波遥感探测获得的亮度温度受月球表层热辐射的控制，与月壤厚度具有指数相关性，并受到月表温度的影响。当月壤和月岩的复介电常数分别为2 + 0.005 j和9 + 1 j、相对磁导率均为1时，对应3.0GHz、7.8GHz、19.35GHz和37.0GHz四个频率的亮度温度与月壤厚度及月表温度的关系可分别近似表示为， 3.0GHz亮度温度： (6) 7.8GHz亮度温度： (7) 19.35GHz亮度温度： (8) 37.0GHz亮度温度： (9) 当月壤厚度和月表温度分别在0.5m~30m和100K~400K之间变化时，上述四个频率的亮度温度变化范围分别在212.5K～252.8K、207.4 K～266.7K、193.8 K～288.6K和174.0 K～310.9K之间。对于较低频率的被动微波遥感，亮度温度随月壤厚度的增大逐渐增大并趋于稳定；对较高频率的被动微波遥感，亮度温度随月壤厚度的增大会产生起伏波动，不利于用单波段反演月壤厚度。亮度温度梯度在频率较高时梯度较大，在很小的月壤厚度范围内很快就趋于0，不利于厚度较大时的月壤厚度反演，但对于厚度较小时的月壤厚度反演精度较高；同时，除3.0GHz外，7.8GHz、19.35GHz和37.0GHz三个频率的亮度温度梯度随月表温度的升高降幅较大，尤其是19.35GHz，适合在夜间对月壤厚度较小的地区进行更精确的探测。对于3.0GHz，其亮度温度梯度受月表温度变化的影响很小，能反映出较深层月壤厚度的信息，可以对月球进行全球全天时探测。若辐射计的分辨率为0.02K，3.0GHz频率对10m厚月壤的判别精度达到0.07m；对于20m厚月壤的精度为1.4m。当月壤厚度小于0.5m时，随着月壤厚度从0到0.5m增加，月球表层的亮度温度贡献呈先减小后增大的趋势，从而使某一亮度温度值可能对应存在两种不同的月壤厚度。因此，对于月壤厚度小于0.5m的区域，利用单波段被动微波遥感亮度温度反演月壤厚度是比较困难的。 在对月被动微波遥感探测中，可以利用月球夜晚时段的亮度温度数据判别月壤厚度是否小于0.5m。当月表温度为100K时，3.0GHz、7.8GHz、19.35GHz和37.0GHz四个频率的亮度温度判别参考值分别为212.9K、207.4K、193.5K和174.1K；月表温度为240K时，上述四个频率的亮度温度判别参考值分别为220.8K、226.8K、234.1K和237.2K。当亮度温度小于参考值时表示月壤厚度小于0.5m，反之，表示月壤厚度大于0.5m。更进一步地，可以根据月表温度的影响系数对月岩是否裸露于月表进行判断。当3.0GHz、7.8GHz、19.35GHz和37.0GHz四个频率的月表温度影响系数接近0.77、0.82、0.84和0.85时，可以认为月岩直接暴露于月表。

地外物质中铂族等亲铁元素的分析及应用

长久以来，对于陨石金属相的全岩研究主要使用中子活化分析方法（INAA），该方法具有灵敏度高、无损样品及制样简单等优点，但它无法测定所有铂族元素（PGEs）。随着分析技术的发展，电感耦合等离子质谱（ICP-MS）越来越广泛地应用于地质学领域，但在地外物质的应用中研究较少。 本论文在分析方法上，首先在国内开展了球粒陨石金属相和铁陨石的主、微量元素的ICP-AES和ICP-MS实验分析方法研究，对四块球粒陨石的金属相以及四块铁陨石进行了分析，初步讨论了星云凝聚和小行星热变质中亲铁元素的变化特征，进一步揭示了星云的凝聚过程、以及铁陨石的结晶过程。对新发现的乌拉斯台铁陨石所做的研究表明，该陨石和新疆陨石可能为成对陨石。并将研究延伸到地外撞击事件的研究中，通过对浙江煤山P/T界线层的样品进行分析，对当时的生物大灭绝事件给出了合理解释。 乌拉斯台铁陨石是在我国新疆新发现的一块铁陨石，其发现地点距离新疆铁陨石（Armanty）约130公里。我们应用ICP-MS分析了乌拉斯台铁陨石（IIIE），以及新疆铁陨石（IIIE）、南丹铁陨石（IIICD）和Mundrabilla铁陨石（IIICD）的全岩组成，结果显示和参考文献有很好的一致性，证明了该分析方法的可行性。我们对乌拉斯台铁陨石进行了系统的岩石学、矿物学、以及微量元素分析，该陨石的岩石结构属于粗粒八面体，铁纹石带宽为1.2  0.2 mm。合纹石以各种微观结构大量存在于该陨石中。陨磷镍铁矿以富镍（30.5-55.5%）的形式出现在合纹石中，或者与陨硫铁，陨硫铬铁矿等共生。并通过计算获知该陨石的冷却速率约为20℃/Myr。其岩石矿物学特征和全岩组成和新疆铁陨石相似，二者都落在IIIE化学群的范围，因此，我们将乌拉斯台铁陨石划分为IIIE化学群，并初步认为和新疆铁陨石是成对陨石。同时，对吉林球粒陨石（H5）、安龙球粒陨石（H5）、以及南极陨石GRV 9919（L3）和GRV 021603（H3）四块球粒陨石金属相进行的研究显示，球粒陨石金属相的亲铁元素配分模式主要与元素的挥发性相关，具有难熔元素基本上平坦分布，而中等和强挥发性元素随其挥性的增高而趋于贫化的特征。 铂族元素的研究不仅在讨论星云凝聚过程中亲铁元素的分异、金属-硅酸盐分异与核-幔的形成，以及金属熔体的结晶分异方面有着重要的意义，对于讨论地外物质的示踪也有着重要的作用。铂族元素在地壳中高度亏损，但在大部分地外物质中富集，因此通常将Ir的异常已否作为是否有地外物质加入的重要依据之一。距今2.51亿年前的二叠纪-三叠纪（P/T界线）时期，发生了地质历史上最大规模的生物灭绝事件，然而对于该事件的诱因却一直存有争议，主要存在两种观点：“地外撞击”和“火山喷发”。我们使用锍镍火试金和同位素稀释法，结合Te共沉淀， 应用ICP-MS分析技术，对我国煤山二叠纪-三叠纪界线层的样品进行了Ir、Ru、Rh、Pt和Pd的测定。火试金方法结果显示Ir的含量为0.053 ng/g，而同位素稀释法对P/T界线事件层样品的分析结果显示，Ir的含量在0.005-0.028 ng/g，两种分析方法的结果均显示没有Ir的正异常。将PGE使用碳质球粒陨石标准化后，整个配分模式呈现出高度分异，Ir/Pd的比值为0.02-0.03CI，明显不同于各类陨石。相反，该界线层样品的PGE配分模式和西伯利亚玄武岩（甚至也可能和峨眉山玄武岩）相似，证明了该界线层样品中的PGE可能来源于玄武岩。P/T界线层样品中PGE的含量从富含黄铁矿的壳层24f向26层呈上升趋势，且在26层为最大值，然后在28层回落，这种趋势可能暗示了玄武岩最大规模的喷发可能出现在26层。该结果有力地证明了P/T界线时期的生物灭绝事件与火山喷发的相关性，给一直存有争议的二叠纪-三叠纪生物灭绝事件提供了新的证据。

Heat capacity and thermochemical study of trifluoroacetamide (C2H2F3NO)

The low-temperature heat capacities of trifluoroacetamide were precisely determined with a small sample precision automated adiabatic calorimeter over the temperature range from 78 to 404 K. A solid-to-solid phase transition, a fusion and a phase transition from a liquid crystalline phase to fully liquid phase have been observed at the temperatures of 336.911+/-0.102, 347.622+/-0.094 and 388.896+/-0.160 K, respectively. The molar enthalpies of these phase transitions as well as the chemical purity of the substance were determined to be 5.576+/-0.004, 11.496+/-0.007, 1.340+/-0.005 kJ mol(-1) and 99.30 mol%, respectively, on the basis of the heat capacity measurements. The molar entropies of the three phase transitions were calculated to be 16.550+/-0.012, 33.071+/-0.029 and 3.447+/-0.027 J mol(-1) K-1, respectively. Further researches of the thermochemical properties for this compound have been carried out by means of TG and DSC techniques. (C) 2000 Elsevier Science B.V. All rights reserved.

Diagnóstico de morte de pastagens nas regiões central e norte do Estado de Mato Grosso.

No Estado de Mato Grosso, na região compreendida pelos municípios de Rondonópolis, Cuiabá, Tangara da Serra, Diamantino, Sinop, Santa Helena, e Chapada dos Guimarães, não se observou problema significativo de morte de pastagens de Brachiaria brizantha, conforme diagnostico realizado no período de 27 de marco a 2 de abril de 2000, por pesquisadores da Embrapa Gado de Corte. Por meio de observações realizadas nas fazendas visitadas, bem como, através de informações obtidas junto a proprietários e/ou administradores, constatou-se que os raros casos de morte de pastagens na região estavam restritos a pequenas áreas dentro das pastagens. Excesso de umidade, em alguns casos (Tangara da Serra e Sinop) e estresse hídrico, em outro (Chapada dos Guimarães), foram as causas dos casos de morte de pastagens constatados nessa região.

Advanced Programming Language Features for Executable Design Patterns "Better Patterns Through Reflection

The Design Patterns book [GOF95] presents 24 time-tested patterns that consistently appear in well-designed software systems. Each pattern is presented with a description of the design problem the pattern addresses, as well as sample implementation code and design considerations. This paper explores how the patterns from the "Gang of Four'', or "GOF'' book, as it is often called, appear when similar problems are addressed using a dynamic, higher-order, object-oriented programming language. Some of the patterns disappear -- that is, they are supported directly by language features, some patterns are simpler or have a different focus, and some are essentially unchanged.

Context-Based Vision System for Place and Object Recognition

While navigating in an environment, a vision system has to be able to recognize where it is and what the main objects in the scene are. In this paper we present a context-based vision system for place and object recognition. The goal is to identify familiar locations (e.g., office 610, conference room 941, Main Street), to categorize new environments (office, corridor, street) and to use that information to provide contextual priors for object recognition (e.g., table, chair, car, computer). We present a low-dimensional global image representation that provides relevant information for place recognition and categorization, and how such contextual information introduces strong priors that simplify object recognition. We have trained the system to recognize over 60 locations (indoors and outdoors) and to suggest the presence and locations of more than 20 different object types. The algorithm has been integrated into a mobile system that provides real-time feedback to the user.

Estimativa de biomassa e estoque de carbono de uma floresta secundária em Minas Gerais.

Em virtude das preocupações mundiais com as quantidades acumuladas de gases de efeito estufa na atmosfera, 175 países assinaram, durante a ECO 92, no Rio de Janeiro, relatório sobre o Painel de Mudanças Climáticas, indicando a necessidade de reduzir as emissões desses gases. Um dos mecanismos, com essa finalidade que tem despertado grande interesse é o financiamento de grandes plantios de árvores visando o seqüestro de quantidades significativas de carbono através da fotossíntese. Tendo em vista que a legislação brasileira de meio ambiente determina a manutenção de uma reserva legal de pelo menos 20% de vegetação natural nas propriedades rurais do sudeste e, considerando-se a forte atividade agropecuária dessa região onde, na paisagem rural, predominam pastos, cultivos e reflorestamentos com Eucalyptus a recuperação das áreas de reserva legal pode atingir escala de interesse, além de contemplar demandas por uma maior proteção da biodiversidade. O presente estudo apresenta estimativas de biomassa e estoque de carbono de uma floresta secundária de cerca de 37 anos por meio de medições diretas, utilizando o método da árvore média. O estudo fitossociológico apontou sete espécies cujas árvores representam cerca de 80,5% de dominância e 77,9% de densidade do sítio, sendo Canudo de Pito, (Mabea fistulifera ? Euphorbiaceae) a espécie arbórea dominante. Obtiveram-se, para biomassa, estimativas de 64.005 Kg.ha-1 por densidade e, por dominância, 66.127 Kg.ha-1. A esses totais correspondem, respectivamente, em quantidades de carbono, 28.802 Kg.ha-1 e 29.757 Kg.ha-1.

Sparsely Faceted Arrays: A Mechanism Supporting Parallel Allocation, Communication, and Garbage Collection

Conventional parallel computer architectures do not provide support for non-uniformly distributed objects. In this thesis, I introduce sparsely faceted arrays (SFAs), a new low-level mechanism for naming regions of memory, or facets, on different processors in a distributed, shared memory parallel processing system. Sparsely faceted arrays address the disconnect between the global distributed arrays provided by conventional architectures (e.g. the Cray T3 series), and the requirements of high-level parallel programming methods that wish to use objects that are distributed over only a subset of processing elements. A sparsely faceted array names a virtual globally-distributed array, but actual facets are lazily allocated. By providing simple semantics and making efficient use of memory, SFAs enable efficient implementation of a variety of non-uniformly distributed data structures and related algorithms. I present example applications which use SFAs, and describe and evaluate simple hardware mechanisms for implementing SFAs. Keeping track of which nodes have allocated facets for a particular SFA is an important task that suggests the need for automatic memory management, including garbage collection. To address this need, I first argue that conventional tracing techniques such as mark/sweep and copying GC are inherently unscalable in parallel systems. I then present a parallel memory-management strategy, based on reference-counting, that is capable of garbage collecting sparsely faceted arrays. I also discuss opportunities for hardware support of this garbage collection strategy. I have implemented a high-level hardware/OS simulator featuring hardware support for sparsely faceted arrays and automatic garbage collection. I describe the simulator and outline a few of the numerous details associated with a "real" implementation of SFAs and SFA-aware garbage collection. Simulation results are used throughout this thesis in the evaluation of hardware support mechanisms.

Clinical Use of the Volume-Time Curve for Endotracheal Tube Cuff Management

BACKGROUND: Previous investigation showed that the volume-time curve technique could be an alternative for endotracheal tube (ETT) cuff management. However, the clinical impact of the volume-time curve application has not been documented. the purpose of this study was to compare the occurrence and intensity of a sore throat, cough, thoracic pain, and pulmonary function between these 2 techniques for ETT cuff management: volume-time curve technique versus minimal occlusive volume (MOV) technique after coronary artery bypass grafting. METHODS: A total of 450 subjects were randomized into 2 groups for cuff management after intubation: MOV group (n = 222) and volume-time curve group (n = 228). We measured cuff pressure before extubation. We performed spirometry 24 h before and after surgery. We graded sore throat and cough according to a 4-point scale at 1, 24, 72, and 120 h after extubation and assessed thoracic pain at 24 h after extubation and quantified the level of pain by a 10-point scale. RESULTS: the volume-time curve group presented significantly lower cuff pressure (30.9 +/- 2.8 vs 37.7 +/- 3.4 cm H2O), less incidence and intensity of sore throat (1 h, 23.7 vs 51.4%; and 24 h, 18.9 vs 40.5%, P < .001), cough (1 h, 19.3 vs 48.6%; and 24 h, 18.4 vs 42.3%, P < .001), thoracic pain (5.2 +/- 1.8 vs 7.1 +/- 1.7), better preservation of FVC (49.5 +/- 9.9 vs 41.8 +/- 12.9%, P = .005), and FEV1, (46.6 +/- 1.8 vs 38.6 +/- 1.4%, P = .005) compared with the MOV group. CONCLUSIONS: the subjects who received the volume-time curve technique for ETT cuff management presented a significantly lower incidence and severity of sore throat and cough, less thoracic pain, and minimally impaired pulmonary function than those subjects who received the MOV technique during the first 24 h after coronary artery bypass grafting.

Prediction of 30-day mortality in older patients with a first acute myocardial infarction

This study sought predictors of mortality in patients aged >or=75 years with a first ST-segment elevation myocardial infarction (STEMI) and evaluated the validity of the GUSTO-I and TIMI risk models. Clinical variables, treatment and mortality data from 433 consecutive patients were collected. Univariable and multivariable logistic regression analyses were applied to identify baseline factors associated with 30-day mortality. Subsequently a model predicting 30-day mortality was created and compared with the performance of the GUSTO-I and TIMI models. After adjustment, a higher Killip class was the most important predictor (OR 16.1; 95% CI 5.7-45.6). Elevated heart rate, longer time delay to admission, hyperglycemia and older age were also associated with increased risk. Patients with hypercholesterolemia had a significantly lower risk (OR 0.46; 95% CI 0.24-0.86). Discrimination (c-statistic 0.79, 95% CI 0.75-0.84) and calibration (Hosmer-Lemeshow 6, p = 0.5) of our model were good. The GUSTO-I and TIMI risk scores produced adequate discrimination within our dataset (c-statistic 0.76, 95% CI 0.71-0.81, and c-statistic 0.77, 95% CI 0.72-0.82, respectively), but calibration was not satisfactory (HL 21.8, p = 0.005 for GUSTO-I, and HL 20.6, p = 0.008 for TIMI). In conclusion, short-term mortality in elderly patients with a first STEMI depends most importantly on initial clinical and hemodynamic status. The GUSTO-I and TIMI models are insufficiently adequate for providing an exact estimate of 30-day mortality risk.

Centenarians and their hearts: a prospective registry with comprehensive geriatric assessment, electrocardiogram, echocardiography, and follow-up

Background Data on the cardiac characteristics of centenarians are scarce. Our aim was to describe electrocardiogram (ECG) and echocardiography in a cohort of centenarians and to correlate them with clinical data. Methods We used prospective multicenter registry of 118 centenarians (28 men) with a mean age of 101.5 ± 1.7 years. Electrocardiogram was performed in 103 subjects (87.3%) and echocardiography in 100 (84.7%). All subjects underwent a follow-up for at least 6 months. Results Centenarians with abnormal ECG were less frequently females (72% vs 93%), had higher rates of previous consumption of tobacco (14% vs 0) and alcohol (24% vs 12%), and scored lower in the perception of health status (6.8 ± 2.0 vs 8.3 ± 6.8). Centenarians with significant abnormalities in echocardiography were less frequently able to walk 6 m (33% vs 54%). Atrial fibrillation/flutter was found in 27 subjects (26%). Mean left ventricular (LV) ejection fraction was 60.0 ± 10.5%. Moderate or severe aortic valve stenosis was found in 16%, mitral valve regurgitation in 15%, and aortic valve regurgitation in 13%. Diastolic dysfunction was assessed in 79 subjects and was present in 55 (69.6%). Katz index and LV dilation were independently associated with the ability to walk 6 m. Age, Charlson and Katz indexes, and the presence of significant abnormalities in echocardiography were associated with mortality. Conclusions Centenarians have frequent ECG alterations and abnormalities in echocardiography. More than one fifth has atrial fibrillation, and most have diastolic dysfunction. Left ventricular dilation was associated with the ability to walk 6 m. Significant abnormalities in echocardiography were associated with mortality.

A general model of error-prone PCR

Pritchard, L., Corne, D., Kell, D.B., Rowland, J. & Winson, M. (2005) A general model of error-prone PCR. Journal of Theoretical Biology 234, 497-509.

The mixing of bubbles in two-dimensional bidisperse foams under extensional shear

Cox, S.J. (2006) The mixing of bubbles in two-dimensional bidisperse foams under extensional shear. Journal of Non-Newtonian Fluid Mechanics . 137:39-45.