541 resultados para 1512
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[ES]La fibrilación ventricular (VF) es el primer ritmo registrado en el 40\,\% de las muertes súbitas por paro cardiorrespiratorio extrahospitalario (PCRE). El único tratamiento eficaz para la FV es la desfibrilación mediante una descarga eléctrica. Fuera del hospital, la descarga se administra mediante un desfibrilador externo automático (DEA), que previamente analiza el electrocardiograma (ECG) del paciente y comprueba si presenta un ritmo desfibrilable. La supervivencia en un caso de PCRE depende fundamentalmente de dos factores: la desfibrilación temprana y la resucitación cardiopulmonar (RCP) temprana, que prolonga la FV y por lo tanto la oportunidad de desfibrilación. Para un correcto análisis del ritmo cardiaco es necesario interrumpir la RCP, ya que, debido a las compresiones torácicas, la RCP introduce artefactos en el ECG. Desafortunadamente, la interrupción de la RCP afecta negativamente al éxito en la desfibrilación. En 2003 se aprobó el uso del DEA en pacientes entre 1 y 8 años. Los DEA, que originalmente se diseñaron para pacientes adultos, deben discriminar de forma precisa las arritmias pediátricas para que su uso en niños sea seguro. Varios DEAs se han adaptado para uso pediátrico, bien demostrando la precisión de los algoritmos para adultos con arritmias pediátricas, o bien mediante algoritmos específicos para arritmias pediátricas. Esta tesis presenta un nuevo algoritmo DEA diseñado conjuntamente para pacientes adultos y pediátricos. El algoritmo se ha probado exhaustivamente en bases de datos acordes a los requisitos de la American Heart Association (AHA), y en registros de resucitación con y sin artefacto RCP. El trabajo comenzó con una larga fase experimental en la que se recopilaron y clasificaron retrospectivamente un total de 1090 ritmos pediátricos. Además, se revisó una base de arritmias de adultos y se añadieron 928 nuevos ritmos de adultos. La base de datos final contiene 2782 registros, 1270 se usaron para diseñar el algoritmo y 1512 para validarlo. A continuación, se diseñó un nuevo algoritmo DEA compuesto de cuatro subalgoritmos. Estos subalgoritmos están basados en un conjunto de nuevos parámetros para la detección de arritmias, calculados en diversos dominios de la señal, como el tiempo, la frecuencia, la pendiente o la función de autocorrelación. El algoritmo cumple las exigencias de la AHA para la detección de ritmos desfibrilables y no-desfibrilables tanto en pacientes adultos como en pediátricos. El trabajo concluyó con el análisis del comportamiento del algoritmo con episodios reales de resucitación. En los ritmos que no contenían artefacto RCP se cumplieron las exigencias de la AHA. Posteriormente, se estudió la precisión del algoritmo durante las compresiones torácicas, antes y después de filtrar el artefacto RCP. Para suprimir el artefacto se utilizó un nuevo método desarrollado a lo largo de la tesis. Los ritmos desfibrilables se detectaron de forma precisa tras el filtrado, los no-desfibrilables sin embargo no.
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Esta coleção, geralmente conhecida por Grineu, foi compilada por Johann Huttich e publicada por Simon Grineu, que também escreveu e assinou o prefácio. A primeira edição, "muito e rara e de inestimável valor", segundo Borba de Moraes, foi publicada na Basiléia por Jo. Hervagium, em 1532. Dessa edição, a Biblioteca Nacional do Rio de Janeiro possui um exemplar que pertencia à Biblioteca da Ajuda. A obra foi reimpressa em Paris, em 1532, e novamente na Basiléia, em 1537. Esta edição foi acrescida da carta de Maximilianus Transilvanus, secretário de Carlos V, ao Cardeal de Salzburgo. Dentre as várias ediçoes, a mais completa é a de 1555. Relata as grandes navegações e as expedições de Cristovão Colombo, Pedro Alonso, Pinzoni, Americo Vespucio, dentre outros
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星间激光通信中,由粗跟踪系统和精跟踪系统组成的复合轴系统完成了系统的大范围、高精度跟踪任务。对复合轴系统进行了基于Z变换的数字模拟以研究其带宽设计。根据计算的卫星轨迹和粗跟踪系统机械误差,得到了粗跟踪系统的带宽设计结果;给出了粗跟踪系统和精跟踪系统的配合工作关系;得到了精跟踪系统的带宽设计结果;最后研究了在中高频扰动下,复合轴系统的带宽设计。以上结果为星间激光通信中的复合轴系统控制系统设计提供了重要依据。
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以宽度为50fs的超短脉冲和负单轴晶体CsLiB6O10(CLBO)为例,对非线性光学晶体中低阶群速度色散(GVD)导致的超短高斯脉冲和超高斯脉冲的脉冲展宽进行了理论分析。在光参量相互作用过程中,对初始无啁啾和有啁啾调制的超短高斯脉冲的脉冲展宽机制和因素进行了数值计算,得出群速度色散导致超短脉冲的寻常光比非寻常光脉冲展宽更严重;波长越短,脉冲展宽越大;当晶体长度等于色散长度时,脉冲宽度增加为初始时的√2倍,色散长度越短,超短脉冲展宽越明显。
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植物血红蛋白在共生固氮根瘤中主要是对固氮酶进行嫌氧保护,确保固氮酶活性,在植物根中协助氧的运输或作为感觉氧压的信号分子.豆科植物凝集素功能之一是对相应专一的根瘤菌有识别作用,并有利于根瘤菌的聚集和侵染。本论文将非豆科结瘤植物Parasponia andersonii血红蛋白基因及豌豆凝集索基因转入水稻,目的是此二基因表达后,豌豆凝集素可聚集、识别豌豆根瘤菌,并有助于它们的侵染,血红蛋白则可对根瘤菌固氮酶进行嫌氧保护,保障其发挥固氮作用,从而为实现水稻结瘤和固氮打下初步基础。 本论文将带有Parasponia血红蛋白基因的pL305质粒,带有潮霉素磷酸转移酶基因及Parasponia血红蛋白基因的农杆菌双元载体质粒pLX412-Hb用花粉管通道法转化水稻l用pLX412-Hb和带有Bar基因、豌豆凝集素基因、Parasponia血红蛋白基因的质粒pLHB用基因枪法转化水稻幼胚及愈伤组织,带有pLX412-Hb的Agrobactmum tumefaciens LBA4404转化烟草,得到如下结果: 1.用pL305质粒花粉管通道法转化水稻,运作1512朵花,得到707粒种子.将230粒种子萌发,发芽220粒;白化苗4株,成苗206株;计发芽率96%,白化苗率1.7%,成苗率90%。取120株提取DNA以Parasponia血红蛋白基因为探针进行点杂交,有6株为阳性结果,阳性率5%.再取4株DNA点杂交阳性植株DNA,以Parasponia血红蛋白基因为探针进行Southem杂交,有3株有阳性结果,阳性率为75%,照此推算转化植株约占总植株的4%.目前,这些转基因植株已开花结实。 2.用pLX412-Hb质粒花粉管通道法转化水稻,运作743朵花,得到340粒种子。将120粒种子萌发,发芽117粒,白化苗3株,成苗111株;计发芽率97. 5%,白化苗率2. 5%,成苗率92. 5%.取30株提取DNA以Parasponia血红蛋白基因为探针进行点杂交,有4株为阳性结果,阳性率13%。再取4株DNA点杂交呈阳性的植株DNA,以Parasponia血红蛋白基因为探针进行Southern杂交,有2株有阳性结果,阳性率为50%,照此推算转化植株约占总植株的7%。目前部分转基因植株巳开花结实. 3.用pLX412 - Hb质粒基因枪法转化水稻幼胚及愈伤组织,抗性筛选得到15株再生植株,以Parasponia血红蛋白基因为探针进行点杂交,有14株为阳性结果,阳性率93%.取7株DNA点杂交呈阳性的植株DNA,以Parasponia血红蛋白基因为探针进行Southern杂交,都为阳性结果,阳性率为100%,照此推算转化植株约占总植株的93%.目前,部分转基因植株已开花结实. 4.用pLX412 -Hb质粒通过Agrobacterrum tumeFaciens LBA4404转化烟草,抗性筛选得到的再生植株以Parasponia血红蛋白基因为探针进行Southern杂交,结果为阳性. 5.用pLHB基因枪法转化的愈伤组织,抗性筛选得到已分化出绿芽点的愈伤组织,以Parasponia血红蛋白基因为探针或以豌豆凝集素基因为探针进行Southern杂交,杂交结果均为阳性. 6.最近国外巳发现大麦有血红蛋白基因.本论文以大麦血红蛋白cDNA为探针对未转基因的水稻进行Southern杂交,结果有阳性带。说明水稻有与大麦血红蛋白基因高度同源序列。以Parasponia血红蛋白基因为探针时杂交结果为阴性,说明水稻血红蛋白基因与Parasponiaa血红蛋白基因核苷酸序列相差较大. 7.提取Southern杂交证明有Parasponia血红蛋白基因整合的水稻根及叶总RNA,以Parasponia血红蛋白基因cDNA为探针进行RNA点杂交,结果根总RNA为阳性,叶总RNA为阴性。初步证明Parasponia血红蛋白基因在水稻根中表达。 8.提取未转基因的水稻根及叶RNA,以大麦血红蛋白基因cDNA为探针进行RNA点杂交,结果:根总RNA为阳性结果,叶总RNA为阴性结果.初步证明水稻血红蛋白基因在水稻根中表达。 总之,本论文证明已将Parasponia血红蛋白基因整合进水稻植株染色体,将豌豆凝集素基因、Parasponia血红蛋白基因整合进水稻愈伤组织染色体,初步证明水稻有血红蛋白基因,内外源血红蛋白基因都有组织特异性表达,从而为本研究的战略设想奠定初步基础。
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IgA抗体是介导机体粘膜免疫的主要因子,其在粘膜分泌物中能有效地阻止外界抗原(包括可溶性抗原、病原微生物以及存在于食物中的致癌物质)附着或侵入粘膜上皮,从而避免这些外来物给机体造成损伤,保持机体粘膜完整并避免胃肠道疾病、呼吸道疾病及泌尿生殖道各种疾病的发生。为了能有效地利用IgA抗体的免疫保护功能,解决诸多困扰人类的粘膜性疾病,前人从很多方面对IgA抗体做了大量的研究,得到很多有意义的结果。本文试图总结这些研究成果,结合最新的研究进展,对IgA抗体的结构、功能及调控等进行评述。
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The vibration response of piled foundations due to ground-borne vibration produced by an underground railway is a largely-neglected area in the field of structural dynamics. However, this continues to be an important aspect of research as it is expected that the presence of piled foundations can have a significant influence on the propagation and transmission of the wavefield produced by the underground railway. This paper presents a comparison of two methods that can be employed in calculating the vibration response of a piled foundation: an efficient semi-analytical model, and a Boundary Element model. The semi-analytical model uses a column or an Euler beam to model the pile, and the soil is modelled as a linear, elastic continuum that has the geometry of a thick-walled cylinder with an infinite outer radius and an inner radius equal to the radius of the pile. The boundary element model uses a constant-element BEM formulation for the halfspace, and a rectangular discretisation of the circular pile-soil interface. The piles are modelled as Timoshenko beams. Pile-soil-pile interactions are inherently accounted for in the BEM equations, whereas in the semi-analytical model these are quantified using the superposition of interaction factors. Both models use the method of joining subsystems to incorporate the incident wavefield generated by the underground railway into the pile model. Results are computed for a single pile subject to an inertial loading, pile-soil-pile interactions, and a pile group subjected to excitation from an underground railway. The two models are compared in terms of accuracy, computation time, versatility and applicability, and guidelines for future vibration prediction models involving piled foundations are proposed.
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甲基叔丁基醚(MTBE)作为一种新型的无铅汽油添加剂被广泛应用以减少含铅汽油对空气的污染。简要介绍了MTBE的理化性质和MTBE的急性毒性、代谢、生殖、遗传毒性,就其对环境的污染以及其防治作了综述,指出了我国开展MTBE有关研究的重要性。
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Pulses of 15 psec duration were generated by an injection laser with an external dispersive resonator operating in the active mode-locking regime. This regime was attained by subjecting the laser diode to a current of high frequency equal to the intermode interval in the external resonator. The duration of the pulses was determined by an autocorrelation method in which the second harmonic was generated in an LiIO//3 crystal.
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A technique based on the integrations of the product of amplified spontaneous emission spectrum and a phase function over one mode interval is proposed for measuring gain spectrum for Fabry-Perot semiconductor lasers, and a gain correction factor related to the response function of the optical spectrum analyzer (OSA) is obtained for improving the accuracy of measured gain spectrum. The gain spectra with a difference less than 1.3 cm(-1) from 1500 to 1600 nm are obtained for a 250-mum-long semiconductor laser at the OSA resolution of 0.06, 0.1, 0.2, and 0.5 nm. The corresponding gain correction factor is about 9 cm(-1) at the resolution of 0.5 nm. The gain spectrum measured at the resolution of 0.5 nm has the same accuracy as that obtained by the Hakki-Paoli method at the resolution of 0.06 nm for the laser with the mode interval of 1.3 nm.
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A complete set of match calculation methods for optimum sizing of PV/wind hybrid system is presented. In this method, the more accurate and practical mathematic models for characterizing PV module, wind generator and battery are adopted; combining with hourly measured meteorologic data and load data, the performance of a PV/wind hybrid system is determined on a hourly basis; by fixing the capacity of wind generators, the whole year's LPSP (loss of power supply probability) values of PV/wind hybrid systems with different capacity of PV array and battery bank are calculated, then the trade-off curve between battery bank and PV array capacity is drawn for the given LPSP value; the optimum configuration which can meet the energy demand with the minimum cost can be found by drawing a tangent to the trade-off curve with the slope representing the relationship between cost of PV module and that of the battery. According to this match calculation method, a set of match calculation programs for optimum sizing of PV/wind hybrid systems have been developed. Applying these match calculation programs to an assumed PV/wind hybrid system to be installed at Waglan island of Hong Kong, the optimum configuration and its hourly, daily, monthly and yearly performances are given. (C) 2003 Elsevier Science Ltd. All rights reserved.