Análise da via Wnt e seu envolvimento no processo da tumorigênese do câncer colo-retal

O câncer colo-retal (CCR) representa o quarto tipo de câncer mais freqüente no Brasil entre homens e mulheres e a sobrevida para esse tipo de neoplasia é considerada boa, se a doença for diagnosticada em estádio inicial. Neste tipo de câncer a progressão do adenoma (tumor benigno) para o adenocarcinoma (tumor maligno) é dependente do acúmulo de mutações em diversos oncogenes e genes supressores de tumor. Estas mutações podem levar a alterações de importantes vias de sinalização que controlam estes eventos como, por exemplo, as vias Wnt e EGFR. No entanto, os mecanismos moleculares e celulares mediados por estas vias durante a progressão do CCR permanecem por serem definidos. Neste trabalho foi avaliada a participação da via Wnt e do EGFR durante a progressão do CCR usando células Caco-2, uma linhagem celular derivada de adenocarcinoma de cólon humano como modelo. As células foram tratadas com EGF, ativador da via EGFR, e cloreto de lítio (LiCl), um conhecido inibidor da enzima GSK-3β e conseqüentemente, ativador da via Wnt, ou alternativamente com a combinação de ambas drogas. Após os tratamentos, foi avaliada a morfologia celular, localização e expressão de proteínas juncionais, os padrões proliferativos e do ciclo celular e o potencial tumorigênico (migração e formação de colônias). Nossos resultados mostram que a localização subcelular das proteínas juncionais claudina-1 e β-catenina foi alterada após tratamento com EGF e LiCl, porém a expressão não foi afetada. A localização nuclear de β-catenina, um marcador da ativação da via Wnt, foi observada após tratamento com ambos os compostos, no entanto estes agentes modularam a enzima GSK-3β de forma diferencial. Além disso, tratamento com EGF aumentou a capacidade proliferativa e migratória da célula, mas não alterou a formação de colônias. LiCl, apesar de ser um conhecido ativador da via Wnt, inibiu o aumento da proliferação e migração causado pelo EGF, como visto pelo tratamento das células com EGF+LiCl, e reduziu a formação de colônias. Nossos resultados revelaram que LiCl possui uma atividade supressora de tumor o que pode representar um novo papel para este composto como um possível agente terapêutico para o tratamento do CCR.

Liquid salt cooled flexible conversion ratio fast reactor: Neutronic design

This paper presents the neutronic design of a liquid salt cooled fast reactor with flexible conversion ratio. The main objective of the design is to accommodate interchangeably within the same reactor core alternative transuranic actinides management strategies ranging from pure burning to self-sustainable breeding. Two, the most limiting, core design options with unity and zero conversion ratios are described. Ternary, NaCl-KCl-MgCl2 salt was chosen as a coolant after a rigorous screening process, due to a combination of favourable neutronic and heat transport properties. Large positive coolant temperature reactivity coefficient was identified as the most significant design challenge. A wide range of strategies aiming at the reduction of the coolant temperature coefficient to assure self-controllability of the core in the most limiting unprotected accidents were explored. However, none of the strategies resulted in sufficient reduction of the coolant temperature coefficient without significantly compromising the core performance characteristics such as power density or cycle length. Therefore, reactivity control devices known as lithium thermal expansion modules were employed instead. This allowed achieving all the design goals for both zero and unity conversion ratio cores. The neutronic feasibility of both designs was demonstrated through calculation of reactivity control and fuel loading requirements, fluence limits, power peaking factors, and reactivity feedback coefficients. © 2009 Elsevier B.V. All rights reserved.

The use of non-dimensional parameters to study stress in lithiumion battery electrode storage particles

Mechanical degradation is thought to be one of the causes of capacity fade within Lithium-Ion batteries. In this work we develop a coupled stress-diffusion model for idealized spherical storage particles, which is analogous to the development of thermal strains. We then non-dimensionalize the model and identify three important parameters that control the development of stress within these particles. We can therefore use a wide number of values for these parameters to make predictions about the stress responses of different materials. The maximum stress developed within the particle for different values of these parameters are plotted as stress maps. A two dimensional model of a battery was then developed, in order to study the effect of particle morphology. Copyright © 2012 by ASME.

Electrical properties of LiNbO3 (electrolyte)/Cu (anode) bi-layers

In this work specific film structures of Li-Nb-O/Li/Li-Nb-O are investigated by AC Impedance Spectroscopy measurements at different temperatures. This gives the opportunity to investigate properties of the material itself and, at the same time, to consider the influence of the grain boundaries on the ionic behavior of the polycrystalline Lithium Niobate. On the other hand, LiNbO3/Li/Cu multi-layers are studied as electrolyte/anode bi-layers and potential parts of "Li-free" microbatteries. The Li deficiency in the as deposited Li-Nb-O films is cured by forming a "sandwich" of Li-Nb-O/Li/Li-Nb-O, which after annealing becomes ionic conductor. The electrical behavior of an annealed film depends on two sources. The first is due to properties of the material itself and the second is based on the network of the grain boundaries. The average size of the grains is strongly influenced by the structure of the ohmic-contact/substrate. The electrical behavior of the electrolyte/anode interface of the "Li-free" structure LiNbO3/Li/Cu/Au is very similar to the impedance measurements of the single LiNbO3 single films. The whole multilayer structure, though, presents a third relaxation time which is consistent of a small resistance. This resistance is independent of temperature and it seems that is due to the metallic interface Li/Cu/Au. © 2010 Elsevier B.V. All rights reserved.

Compensatory growth response in three-spined stickleback in relation to feed-deprivation protocols

Different protocols of food deprivation were used to bring two groups of juvenile three-spined sticklebacks Gaslerosteus aculeatus to the same reduced body mass in comparison with a control group fed daily ad libitum. One group experienced I week or deprivation then 2 weeks on maintenance rations. The second group experienced I week of ad lithium feeding followed by 2 weeks of deprivation. The deprived groups were reduced to a mean mass ore. 80% of controls. The compensatory growth response shown when ad libitum feeding was resumed was independent of the trajectory by which the three-spined sticklebacks had reached the reduced body mass. The compensatory response was Sufficient to return the deprived groups to the mass and length trajectories shown by the control group within 4 weeks. There was full compensation for dry mass and total lipid, but incomplete compensation for lipid-free dry mass. Hyperphagia and increased growth efficiency were present in the re-feeding phase, but there was a lag of a week before the hyperphagia was established. The consistency of the compensatory response of immature three-spined sticklebacks provides a potential model system for the analysis and prediction of appetite and growth in teleosts. (C) 2003 The Fisheries Society of the British isles.

Experimental and theoretical analysis of nondegenerate ultrabroadband chirped pulse optical parametric amplification

Experimental investigations of nondegenerate ultrabroadband chirped pulse optical parametric amplification have been carried out. The general mathematical expressions for evaluating parametric bandwidth, gain and gain bandwidth for arbitrary three-wave mixing parametric amplifiers are presented. In our experiments, a type-I noncollinear phase-matched optical parametric amplifier based on lithium triborate, which was pumped by a 5-ns second harmonic pulses from a Q-switched Nd:YAG operating at 10 Hz, seeded by a 14-fs Ti:sapphire laser at 800 nm, was presented. The 0.85 nJ energy of input chirped signal pulse with 57-FWHM has been amplified to 3.1 muJ at pump intensity 3 GW/cm(2), the corresponding parametric gain reached 3.6 x 10(3), the 53 nm-FWHM gain spectrum bandwidth of output signal has been obtained. The large gain and broad gain bandwidth, which have been confirmed experimentally, provide great potentials to amplify efficiently the broad bandwidth femtosecond light pulses to generate new extremes in power, intensity, and pulse duration using optical parametric chirped pulse amplifiers pumped by powerful nanosecond systems.

Color center conversion by femtosecond pulse laser irradiation in LiF : F-2 crystals

We report the observation of intense spontaneous emission of green light from LiF:F-2:F-3(+) centers in active channel waveguides generated in lithium fluoride crystals by near-infrared femtosecond laser radiation. While irradiating the crystal at room temperature with 405 nm light from a laser diode, yellow and green emission was seen by the naked eye. Stripe waveguides were fabricated by translating the crystal along the irradiated laser pulse, and their guiding properties and fluorescence spectra at 540 nm demonstrated. This single-step process inducing a waveguide structure offers a good prospect for the development of a waveguide laser in bulk LiF crystals.

聚合物锂离子电池和生物燃料电池的相关研究

本论文分为两个部分研究了铿离子电池和生物燃料电池中的关键材料，主要的创新点和结论如下。采用聚合物电解质是提高铿二次电池性能的有效方法之一。聚合物电解质良好电导率、高铿离子迁移数、宽电化学窗口以及好的机械性能是其应用于铿二次电池中的关键。论文的第一部分主要讨论了聚合物、增塑剂和无机纳米粒子等对复合电解质体系的化学和物理性质的影响。我们采用溶液浇注一浸渍法制备了各种纳米复合聚合物电解质，例如开发出基于PVDFHFP或梳状聚合物基体的全固态以及聚合物和碳酸醋形成的胶体聚合物电解质体系。首次制备了具有较高离子电导率的单离子聚合物电解质。考察了两类纳米粒子填充物对体系的影响：一种是“惰性”发烟硅；另一种是“活性”蒙脱土。比较了全固态和胶体聚合物电解质体系电化学性质的不同之处。采用电化学交流阻抗，示差扫描量热法，X衍射，拉曼光谱，红外光谱，扫描电镜，循环伏安等方法详细研究了聚合物电解质中各组分对体系离子电导率和机械性能的影响。研究结果表明，纳米复合物为开发具有特定电化学和机械性能的电解质提供了一种有效的途径，它对聚合物电解质的物理性质影响明显。纳米粒子的加入增强了体系的机械性能，同时也使体系对溶剂的吸附能力增加。在全固态聚合物电解质中加入增塑剂，形成胶体态聚合物电解质，体系的电导率大大增加。所制备的胶体复合物电解质的室温电导率可以达到10-3s cm-1的数量级，机械强度好，阳离子迁移数高。指出选择合适的添加剂及复合方法，控制界面的结构和形态，形成尽可能多的高导电的界面，是获得电导率高和机械性能良好的聚合物电解质的有效途径。并讨论了聚合物电解质在铿离子电池中的应用。 近年来，针对生物燃料电池的研究得到了广泛关注，其中实现蛋白质酶分子和电极之间的直接电子传递是研究中的热点。论文的第二部分主要研究了生物燃料电池中的酶电极。通过对碳纳米管（MWNTs）进行预处理，使其表面带有功能性官能团，从而可以实现酶分子在碳纳米管表面的固定，同时还保持了其生物活性。采用吸附法将微过氧化物酶-11（MP-11）或葡萄糖氧化酶（GOx）等生物分子固定到MWNTs上制成酶修饰电极，研究MWNTs对酶和电极之间电子传递的促进作用。当酶分子（MP-11，GOX）固定到MWNTs表面后，循环伏安结果显示出一对可逆的氧化还原峰，对应酶分子的直接电子转移。研究结果表明这种方法可以扩展到固定其他生物酶分子以及实现蛋白质酶分子和电极之间的直接电化学，可以获得一系列氧化还原酶分子的电化学参数，如反应速率常数等。同时，我们还研究了酶修饰电极对其底物的电催化反应。研究结果表明，该修饰电极对底物的电化学反应表现出较好的催化活性。我们还研究了酶分子在MWNTs修饰铂微电极上的电化学行为。这些研究为研制生物燃料电池提供了一种固定酶以及制备电极材料较好的方法。

聚甲基丙烯酸多缩乙二醇二酯－锂盐－溶剂三组份凝胶聚合物电解质的制备、导电性能和导电机理研究

由极性聚合物-碱金属盐构成的聚合物固体电解质（SPE）是一类很有前途的离子导电材料。但此类SPE，比通常非水介质电解质溶液约低3个数量级，故极需发展电导率更高的新型SPE材料。目前，由极性（或交联）聚合物、碱金属盐和高介电常数溶剂三组份构成的新一代SPE正在崛起，其室温电导率的达10~（－3）S·cm~(-1)。本工作以甲基丙烯酸多缩乙二醇二酯为大分子单体，研究了三组份凝胶电解质的制备、各组分的变化和温度等对膜强度和电导率的影响；并研究了该凝胶体系中离子传导机理。

High electrical-to-green efficiency high stability intracavity-frequency-doubled Nd:YAG-LBO QCW 532 nm laser with a straight cavity

An electrical-to-green efficiency of more than 10% was demonstrated by intracavity-frequency-doubling a Q-switched diode-side-pumped Nd:YAG laser with a type II lithium triborate (LBO) crystal in a straight plano-concave cavity. An average power of 69.2 W at 532 nm was generated when electrical input power was 666 W. The corresponding electrical-to-green conversion efficiency is 10.4%. To the best of our knowledge, this is the highest electrical-to-green efficiency of second harmonic generation laser systems with side-pumped laser modules, ever reported. At about 66 W of green output power, the power fluctuation over 4 hours was better than +/-0.86%.

X-ray spectroscopy of hollow argon atoms formed on a beryllium surface

The X-rays induced during interaction of highly charged argon ions with a beryllium surface are reported. It is found that the K shell X-ray yield of single particle during interaction of hydrogen-like argon ions was 3.6 x 10(-3), which is five orders more than that of heliumlike argon ions. Moreover, due to the screening the 2s electron, no K X-ray was emitted during interaction of lithium-like argon ions with the beryllium surface. It is also found that the X-ray spectrum induced by Ar17+ interacting with residual gases is very different from that induced by Ar17+ interacting with the surfaces, that provided an experimental evidence for the existence of the hollow atoms below the surface.

Preparation of Microporous Membranes by Swift Heavy Ion Irradiation and Impedance Characterization

Polypropylene (PP) microporous membranes were successfully prepared by swift heavy ion irradiation and track-etching. Polypropylene foils were irradiated with Au-197 ions of kinetic energy 11.4 MeV.u(-1) (total energy of 2245.8 MeV) and fluence 1x10(8) ions.cm(-2) at normal incidence. The damaged regions produced by the gold ions along the trajectories were etched in H2SO4 and K2Cr2O7 solutions leading to the formation of cylindrical pores in the membranes. The pore diameters of the PP microporous membranes increased from 380 to 1610 nm as the etching time increased from 5 to 30 min. The surface and cross-section morphologies of the porous membranes were characterized by scanning electron microscopy (SEM). The micropores in the membranes were found to be cylindrical in shape, homogeneous in distribution, and equal in size. Some mathematical relations of the porosity of the PP microporous membranes were established by analytic derivation. The microporous membranes were used in lithium-ion batteries to measure their properties as separators. The electrical conductivity of the porous membrane immersed in liquid electrolyte was found to be comparable to that of commercial separators by electrochemical impedance spectroscopy (EIS). The results showed that the porosity and electrical conductivity were dependent on the ion fluence and etching time. By adjusting these two factors, microporous membranes with good porosity and electrical conductivity were made that met the requirements for commercial use.

利用重离子辐照及蚀刻技术制备锂离子电池隔膜

本文通过对目前锂离子电池市场及锂离子电池隔膜制备现状的研究，提出采用重离子辐照技术制备锂离子电池隔膜的新方法。拓展了重离子辐照技术的应用，为锂离子电池隔膜的国产化另辟蹊径。实验中，用能量25 MeV/u 的Kr86及11.4 MeV/u的197Au离子，以1×108 cm-2-5×109 cm-2剂量辐照聚丙烯薄膜，通过电导测量法监测蚀刻液的参数，包括温度、硫酸浓度、重铬酸钾浓度对径迹蚀刻速率的影响，得到适合的蚀刻条件；并用场发射扫描电镜对孔的形状及孔径大小进行表征；成功制备出孔径均匀、具有密度和大小可控的重离子径迹聚丙烯孔膜；对孔洞锥角的形成进行分析，给出锥角的计算公式，为利用重离子辐照技术制备锂离子电池隔膜提供了实验数据

Dynamic mechanical properties of gel polymer electrolytes containing ionic liquid

The copolymer of acrylonitrile (AN), methyl methacrylate (MMA) and poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) is synthesized in 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF(4)). The dynamic mechanical properties of the resulting gel polymer electrolytes containing ionic liquid are measured.