An extended computational model of the circulatory system for designing ventricular assist devices.

An extended computational model of the circulatory system has been developed to predict blood flow in the presence of ventricular assist devices (VADs). A novel VAD, placed in the descending aorta, intended to offload the left ventricle (LV) and augment renal perfusion is being studied. For this application, a better understanding of the global hemodynamic response of the VAD, in essence an electrically driven pump, and the cardiovascular system is necessary. To meet this need, a model has been established as a nonlinear, lumped-parameter electrical analog, and simulated results under different states [healthy, congestive heart failure (CHF), and postinsertion of VAD] are presented. The systemic circulation is separated into five compartments and the descending aorta is composed of three components to accurately yield the system response of each section before and after the insertion of the VAD. Delays in valve closing time and blood inertia in the aorta were introduced to deliver a more realistic model. Pump governing equations and optimization are based on fundamental theories of turbomachines and can serve as a practical initial design point for rotary blood pumps. The model's results closely mimic established parameters for the circulatory system and confirm the feasibility of the intra-aortic VAD concept. This computational model can be linked with models of the pump motor to provide a valuable tool for innovative VAD design.

冬枣果实对不同贮藏条件的生理反应及耐贮性研究

本文以我国特有的冬枣果实为试材，系统地研究了冬枣果实在室温、低温和不同O2和CO2浓度气调贮藏条件下的生理特性、风味品质和贮藏性，提出了适合于冬枣果实生理特性的气调指标和贮藏时间;分析了冬枣在不同贮藏条件下果实硬度、颜色、叶绿素和花青素、可溶性固形物、可滴定酸、Vc、乙醇和乙酸乙酯等物质成分的含量变化及与果实风味品质的关系;同时也分析了多酚氧化酶（PPO）、苯丙氨酸解氨酶（PAL）、过氧化物酶（POD）、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、多聚半乳糖醛酸酶（PG）和脂氧合酶（LOX）的活性变化情况以及丙二醛（MDA）含量和膜透性的变化情况，揭示了它们与冬枣果实转红、酒化、褐变、软化、衰老、及耐贮性的关系。对冬枣果实在气调贮藏中的生理反应和品质变化的研究，为形成冬枣果实采后商业化贮藏的系列配套技术提供了理论依据。试验结果表明： 1、冬枣果实在不同贮藏环境下品质的变化：随着贮藏时间的延长，冬枣果实Vc含量呈明显下降的趋势，CA处理能有效地抑制果实Vc含量的下降;不同贮藏条件对冬枣果实SSC影响不大;冬枣果实花青素的含量随贮藏时间逐渐下降，高O2浓度（70%）动态气调与其它处理相比，能更有效保持冬枣果实果皮的颜色及花青素和叶绿素的含量，以及果实的亮度、颜色饱和度和色度;同时，还能降低贮藏前期冬枣果实乙醇释放量。 2、冬枣果实在不同贮藏环境下生理的变化：（1） PG 酶是影响冬枣果实软化的主要因素，冬枣果实中存在内切和外切两种PG 酶，在冬枣果实的成熟过程中，Exo-PG和Endo-PG迅速积累，并呈现较高的活性，多聚半乳糖醛酸酶活性与冬枣果实的软化密切相关。CA贮藏与普通冷藏相比，可有效地抑制冬枣果实多聚半乳糖醛酸酶的活性和延缓果实软化，其中以5% O2的CA贮藏的效果最好。（2）膜质过氧化是造成冬枣果实褐变的主要因素，在室温下冬枣果实细胞膜透性随贮藏时间逐渐上升，CA贮藏在贮藏前中期可有效控制MDA含量的上升和果实褐变的发生，有利于降低膜脂过氧化程度，保护细胞膜结构并延缓果实衰老。冬枣果实褐变与PPO活性关系不大，但与膜透性及膜质过氧化作用的产物—丙二醛（MAD）含量变化显著相关。（3）冬枣果实采收时的SOD活性很低，在25 C下，果实SOD活性急剧上升，低温贮藏条件下，果实SOD活性出现两次高峰，第一次高峰为果实后熟的标志，第二次高峰标志着果实的衰老。（4）在不同贮藏条件下，冬枣果实PAL活性均随贮藏期的延长而呈现下降趋势。 3、影响冬枣果实贮藏性的生理因素：冬枣果实的衰老与活性氧代谢失调和防御体系活力下降有关，随着果实衰老的出现，果实的POD、CAT等保护酶活性均呈现明显下降的趋势。气调贮藏在前期能显著提高冬枣果实POD的活性，而在后期又显著抑制了POD活性的上升，说明POD在果实贮藏初期表现为保护效应，而在后期则表现为伤害效应。 4、冬枣果实适宜的贮藏条件：与普通冷藏相比，气调贮藏（CA）能明显地延缓果实衰老，减少腐烂和褐变，保持风味品质和延长贮藏时间。其中以较高O2浓度的（10% O2 + 0% CO2）气调贮藏效果最好。气调贮藏与杀菌剂配合有利于延长冬枣的贮藏期，0.1%的施保克和0.1%戴挫霉处理能有效控制冬枣果实贮藏期间的腐烂，延长贮藏时间，施保克的防腐效果好于戴挫霉。 5、拮抗菌和病原菌处理对冬枣果实抗性相关酶的诱导：接种拮抗菌+病原菌或只接种病原菌能诱导冬枣果实蛋白含量的显著升高，说明拮抗菌和病原菌处理诱导了果实病原相关蛋白的积累。在常温条件下，拮抗菌和病原菌处理抑制了冬枣果实的CAT酶活性，诱导了SOD和POD活性的上升。同时果实的蛋白含量也显著升高。在低温条件下，CAT和SOD活性受抑制，POD、PPO和 PAL活性被诱导并显著高于正常果实。这说明拮抗菌处理的冬枣果实可能通过加强氧化酶活性的方式来达到抗病的效果。拮抗菌和病原菌处理后，该部分组织的氧化酶活性加强，它们可以分解毒素，促进伤口愈合，抑制病原菌水解酶活性，从而抵抗病害的扩展。PAL是催化莽草酸途径的关键酶，可合成酚、植保素和木质素，而这些物质均与植物抗性有关。

Experimental and theoretical comparison between static and dynamic torsional soil tests

The dynamic properties of dry Leighton Buzzard sand have been investigated using a resonant column test apparatus. These data are compared with very low frequency cyclic tests on identical specimens of sand. The comparison indicates that the properties of dry sand are independent of frequency. A simple one-dimensional model of kinematic hardening plasticity is used to predict the dynamic behaviour of the sand. The input parameters for this model are based on the results of static tests. These may be conducted on standard laboratory equipment with only minor modifications. The predictions are in good agreement with the measured data.

Las ciencias del mar en la Argentina

La situación de las ciencias del mar en la Argentina se puede caracterizar como una de ‘excelencia en aislamiento’. El tema dominante de las discusiones mantenidas por el comité que preparó este informe fue la virtual inexistencia de coordinación entre programas de investigación, equipo para realizar tareas de campo y personal científico y de apoyo en las instituciones. La coordinación que existe ocurre gracias a enormes esfuerzos individuales y a relaciones personales. Si bien en muchos lugares hay investigadores destacados y entusiastas, casi todos sufren de aislamiento físico, mínima financiación y la necesidad de prestar servicios por contrato para llevar adelante su trabajo. Además, como suelen carecer de interacción científica con colegas, les resulta muy difícil diseñar programas con una perspectiva amplia del ecosistema. Muchos laboratorios padecen de problemas estructurales, en especial la carencia de equipamiento moderno y destrezas actualizadas. Muy pocos reúnen una masa crítica de investigadores, y aun aquellos que congregan a muchos científicos no parecen practicar la coordinación entre proyectos ni usan mecanismos que faciliten una interacción constructiva. No se advierten programas que utilicen técnicas moleculares más allá de un nivel superficial. No hay bibliotecas adecuadas, por lo que es poco realista que las autoridades institucionales pretendan que resulten publicaciones de alto vuelo y de circulación internacional. Las mejores instituciones se encuentran diseminadas entre Ushuaia y Buenos Aires, pero hay escasas reuniones nacionales en las que establecer contactos, intercambiar ideas y diseñar colaboraciones. Con una excepción, no hay buques oceanográficos disponibles para investigar y las embarcaciones menores son pocas, lo que impide realizar estudios sobre la plataforma e incluso cercanos a la costa. Algunos de los mejores grupos han concentrado su actividad en el área costera, lo que limita seriamente el alcance de sus investigaciones. El comité formuló algunas recomendaciones, detalladas al final del informe, que permitirían comenzar a atacar estas carencias. Una necesidad fundamental sería un plan oceanográfico nacional que reconozca la magnitud de la plataforma argentina, la importancia de las ciencias del mar y la escala de los problemas que encaran sus disciplinas. Un elemento crítico de tal plan sería la necesidad de apoyar amplios estudios integradores, para comprender cómo peces y mamíferos marinos utilizan la productividad del Mar Argentino, desde la costa hasta más allá del borde de la plataforma. El plan también debería encarar la financiación unificada y el uso compartido de embarcaciones y equipo de alto costo. Por último, debería asegurar recursos para apoyar a estudiantes y, más importante aún, promover la creación de oportunidades laborales para graduados, lo que contribuiría a solucionar el problema de la fuga de cerebros que al presente acosa a estas disciplinas. Las recomendaciones contenidas en este informe acerca de reflexionar y reorganizar la infraestructura científica en el más alto nivel gubernamental no podrán encontrar aplicación sin que haya coordinación y comunicación entre la comunidad de científicos del mar en la Argentina. Las ciencias marinas necesitan unificar su discurso para explicar la importancia del ambiente oceánico y sus recursos para la nación, y para presentar recomendaciones en orden de prioridad para el futuro.

The study of biological characteristics and heavy metal determination of Cd, Pb, Fe, V, Ni in the muscle, liver and gonad tissues of kingfish Scomberomorus commerson in the coastal waters of the Hormozagan Province (Persian Gulf)

Biological studies and heavy metal (Ni, v, Fe, Pb,Cd) determination in liver, gonad and muscle of Scomberomorus commerson were carried out from Oct 2006 to Sept 2007 in Hormozgan coastal waters. 599 Samples were gutted for reproduction and nutrition studies, fork length and weight were measured to nearest cm and g respectively. Meanwhile 40 samples were also investigated for heavy metal studies. All specimens were collected from two major landing sites (Bandar Lengeh & Bandar Abbas). Minimums & maximum fork length & weight were 29, 128 cm & 235 and 15350 g respectively.Isometric growth was shown according to our study and b was estimated 2.9 (overall), 2.91(male) & 2.89 (female). The average relative gut length was 0.52± 0.007 and it was determined that S. commerson is a carnivorous. More than 99 percent of gut content was different teleost fishes. Gastro somatic index had two peaks in Nov & Jan (before spawning) and with a decreased trend in July, the spawning period. Occurrence of empty stomach was estimated % 65.77. Maximum amount of condition factor was in Dec. Spawning season was started from June. The average of Absolute & relative fecundity (to weight unit) was 1217149±179315 and 178.2±15.58 respectively. Lm50% was estimated 75 cm for females. Sex ratio was 0.97: 1 (male: female). Chi- Square test showed no significant difference (p>0.05). Maximum amount of hepatosomatic index was estimated in March.Metal concentrations were determined using either Flame Atomic Absorption Spectroscopy (for Fe) or Graphite Furnace Atomic Absorption Spectroscopy (for Pb,Cd,Ni and V). The mean concentration (μg/g dry weight)of Pb,Cd,Ni,V and Fe in the liver were 0.0309, 0.0268, 0.0672, 0.0077, 2.5159 in the gonad 0.0440 ,0.0295, 0.1096, 0.0000, 1.4449 and in the muscle 0.0244, 0.0324, 0.0656, 0.0128, 1.6138 respectively. The maximum metal concentrations were below the maximum permissible limits for human consumption recommended by the USEPA, WHO and the UK. The results of Kendall's Tau-b correlation coefficient were as follows: The Liver tissue: There were significant positive linear relationships between accumulation of V, Fe, and Pb with Fork length, Pb and Fe with weight, GSI with Pb, Cd, V and 109 Fe, and a negative linear relationships between HSI with accumulation of V and Fe, Fork length, weight and GSI. The Gonad tissue: There were significant positive linear relationships between GSI with accumulation of Pb, Cd, Fe, Fork length and weight, a negative linear relationship between HSI with Fork length, weight and GSI. The Muscle tissue: There were significant positive linear relationships between accumulations of V, Fe with Fork length and weight factors and as well as GSI with Cd, V, Fe, Pb, Fork length and weight,a negative linear relationship between HSI with Fork length, weight, Cd, Fe and GSI. The results of Mann-Whitney U tests (P≤0.05) show that there were significant differences between summer and autumn from heavy metal contents in the studied tissues point of view. The only exceptions were for Ni in the liver, gonads and muscle and as well as there were significant differences between male and female from heavy metal contents in the studied tissues. The only exceptions were for Pb in muscle, Ni in liver, gonad and muscle, V in muscle, and Cd and Fe in gonads.

Triplophysa rosa sp nov.: a new blind loach from China

A new blind loach of Triplophysa Rendahl 1933 was collected from a subterranean pool in a cave at Wulong County, Chongqing City, China, in November 2002. The new species, named Triplophysa rosa sp. nov., can be distinguished from its congeners by the following unique characters: eyes vestigial; 9 branched dorsal-fin rays; 12 branched pectoral-fin rays; 7 branched pelvic-fin rays; 6 branched anal-fin rays; 7 + 7 branched caudal-fin rays; distal margin of dorsal-fin concave; tip of pelvic-fin surpasses vertical level of anus; caudal-fin deeply forked; whole body scaleless and colourless. (c) 2005 The Fisheries Society of the British Isles.

Nuclear matrix of the most primitive eukaryote Archezoa

Accumulating evidence suggests that unicellular Archezoa are the most primitive eukaryotes and their nuclei are of significance to the study of evolution of the eukaryotic nucleus. Nuclear matrix is an ubiquitous important structure of eukaryotic nucleus; its evolution is certainly one of the most important parts of the evolution of nucleus. To study the evolution of nuclear matrix, nuclear matrices of Archezoa are investigated. Giardia lamblia cells are extracted sequentially. Both embedment-free section EM and whole mount cell EM of the extracted cells show that, like higher eukaryotes, this species has a residual nuclear matrix in its nucleus and rich intermediate filaments in its cytoplasm, and the two networks connect with each other to form a united network. But its nuclear matrix does not have nucleolar matrix and its lamina is not as typical as that of higher eukaryotes; Western blotting shows that lamina of Giardia and two other Archezoa Entamoeba invadens and Trichomonas vaginali all contain only one polypeptide each which reacts with a mammalia anti-lamin polyclonal serum and is similar to lamin B (67 ku) of mammlia in molecular weight. According to the results and references, it is suggested that nuclear matrix is an early acquisition of the eukaryotic nucleus, and it and the "eukaryotic chromatin" as a whole must have originated very early in the process of evolution of eukaryotic cell, and their origin should be an important prerequisite of the origin of eukaryotic nucleus; in the iamin (gene) family, B-type lamins (gene) should be the ancestral type and that A-type lamins (gene) might derive therefrom.