Natural convection in metal foams with open cells

This paper presents a combined experimental and numerical study on natural convection in open-celled metal foams. The effective thermal conductivities of steel alloy (FeCrAlY) samples with different relative densities and cell sizes are measured with the guarded-hot-plate method. To examine the natural convection effect, the measurements are conducted under both vacuum and ambient conditions for a range of temperatures. The experimental results show that natural convection is very significant, accounting for up to 50% of the effective foam conductivity obtained at ambient pressure. This has been attributed to the high porosity (ε > 0.9) and inter-connected open cells of the metal foams studied. Morphological parameters characterizing open-celled FeCrAlY foams are subsequently identified and their cross-relationships are built. The non-equilibrium two-equation energy transfer model is employed, and selected calculations show that the non-equilibrium effect between the solid foam skeleton and air is significant. The study indicates that the combined parameter, i.e., the porous medium Rayleigh number, is no longer appropriate to correlate natural convection by itself when the Darcy number is sufficiently large as in the case of natural convection in open-celled metal foams. Good agreement between model predictions and experimental measurements is obtained. © 2005 Elsevier Ltd. All rights reserved.

Theory of ozone isotopic effects and various electron transfer reactions

Three separate topics, each stimulated by experiments, are treated theoretically in this dessertation: isotopic effects of ozone, electron transfer at interfaces, and intramolecular directional electron transfer in a supramolecular system.

The strange mass-independent isotope effect for the enrichment of ozone, which has been a puzzle in the literature for some 20 years, and the equally puzzling unconventional strong mass-dependent effect of individual reaction rate constants are studied as different aspects of a symmetry-driven behavior. A statistical (RRKM-based) theory with a hindered-rotor transition state is used. The individual rate constant ratios of recombination reactions at low pressures are calculated using the theory involving (1) small deviation from the statistical density of states for symmetric isotopomers, and (2) weak collisions for deactivation of the vibrationally excited ozone molecules. The weak collision and partitioning among exit channels play major roles in producing the large unconventional isotope effect in "unscrambled" systems. The enrichment studies reflect instead the non-statistical effect in "scrambled" systems. The theoretical results of low-pressure ozone enrichments and individual rate constant ratios obtained from these calculations are consistent with the corresponding experimental results. The isotopic exchange rate constant for the reaction ^(16)O + ^(18)O ^(18)O→+ ^(16)O ^(18)O + ^(18)O provides information on the nature of a variationally determined hindered-rotor transition state using experimental data at 130 K and 300 K. Pressure effects on the recombination rate constant, on the individual rate constant ratios and on the enrichments are also investigated. The theoretical results are consistent with the experimental data. The temperature dependence of the enrichment and rate constant ratios is also discussed, and experimental tests are suggested. The desirability of a more accurate potential energy surface for ozone in the transition state region is also noted.

Electron transfer reactions at semiconductor /liquid interfaces are studied using a tight-binding model for the semiconductors. The slab method and a z-transform method are employed in obtaining the tight-binding electronic structures of semiconductors having surfaces. The maximum electron transfer rate constants at Si/viologen^(2-/+) and InP /Me_(2)Fc^(+/O) interfaces are computed using the tight-binding type calculations for the solid and the extended-Huckel for the coupling to the redox agent at the interface. These electron transfer reactions are also studied using a free electron model for the semiconductor and the redox molecule, where Bardeen's method is adapted to calculate the coupling matrix element between the molecular and semiconductor electronic states. The calculated results for maximum rate constant of the electron transfer from the semiconductor bulk states are compared with the experimentally measured values of Lewis and coworkers, and are in reasonable agreement, without adjusting parameters. In the case of InP /liquid interface, the unusual current vs applied potential behavior is additionally interpreted, in part, by the presence of surface states.

Photoinduced electron transfer reactions in small supramolecular systems, such as 4-aminonaphthalimide compounds, are interesting in that there are, in principle, two alternative pathways (directions) for the electron transfer. The electron transfer, however, is unidirectional, as deduced from pH-dependent fluorescence quenching studies on different compounds. The role of electronic coupling matrix element and the charges in protonation are considered to explain the directionality of the electron transfer and other various results. A related mechanism is proposed to interpret the fluorescence behavior of similar molecules as fluorescent sensors of metal ions.

Dieta hiperlipídica com ou sem adição de sal modula diferentemente a produção de peptídeo natriurético atrial e a expressão de renina em camundongos

Estudo dos efeitos de uma dieta rica em sal e / ou gordura saturada em grânulos de peptídeo natriurético atrial (ANP), hipertensão, expressão da renina e ultraestrutura cardíaca em camundongos C57Bl / 6. Camundongos machos adultos jovens foram separados em quatro grupos (n = 12) e alimentados com uma das seguintes dietas por 9 semanas: dieta padrão para roedores (Grupo P), dieta hiperlipídica (Grupo HL), dieta hipersódica (Grupo HS) e dieta hiperlipídica e hipersódica simultaneamente (HL-HS). Foram examinados: alterações no ANP sérico, ultra-estrutura dos cardiomiócitos produtores de ANP, estrutura do ventrículo esquerdo, pressão arterial sanguínea, expressão da renina no rim, taxa de filtração glomerular (TFG), eficiência alimentar, parâmetros lipídicos e glicídicos. Os animais alimentados com dieta hiperlipídica mostraram um pequeno aumento na produção de ANP, discreta hipertrofia ventricular esquerda, aumento da eficiência alimentar, dislipidemia e hiperglicemia. Animais alimentados com dieta hipersódica tiveram um grande aumento na produção de grânulos de ANP e correspondente elevação do seu nível sérico, hipertrofia ventricular esquerda, hipertensão arterial, diminuição dos níveis de renina e aumento da TFG. A combinação das duas dietas (HL-HS) teve um efeito aditivo. A ingestão de uma dieta com alto teor de sal e lipídeos induz alterações ultraestruturais dos cardiomiócitos, aumento da produção de ANP e elevação de seu nível sérico e reduz a quantidade de renina no rim.

Nonclassical excitation and quantum interference in a three level atom

Non-classical properties and quantum interference (QI) in two-photon excitation of a three level atom (|1〉), |2〉, |3〉) in a ladder configuration, illuminated by multiple fields in non-classical (squeezed) and/or classical (coherent) states, is studied. Fundamentally new effects associated with quantum correlations in the squeezed fields and QI due to multiple excitation pathways have been observed. Theoretical studies and extrapolations of these findings have revealed possible applications which are far beyond any current capabilities, including ultrafast nonlinear mixing, ultrafast homodyne detection and frequency metrology. The atom used throughout the experiments was Cesium, which was magneto-optically trapped in a vapor cell to produce a Doppler-free sample. For the first part of the work the |1〉 → |2〉 → |3〉 transition (corresponding to the 6S_1/2F = 4 → 6P_3/2F' = 5 → 6D_5/2F" = 6 transition) was excited by using the quantum-correlated signal (Ɛ_s) and idler (Ɛ_i) output fields of a subthreshold non-degenerate optical parametric oscillator, which was tuned so that the signal and idler fields were resonant with the |1〉 → |2〉 and |2〉 → |3〉 transitions, respectively. In contrast to excitation with classical fields for which the excitation rate as a function of intensity has always an exponent greater than or equal to two, excitation with squeezed-fields has been theoretically predicted to have an exponent that approaches unity for small enough intensities. This was verified experimentally by probing the exponent down to a slope of 1.3, demonstrating for the first time a purely non-classical effect associated with the interaction of squeezed fields and atoms. In the second part excitation of the two-photon transition by three phase coherent fields Ɛ₁ , Ɛ₂ and Ɛ₀, resonant with the dipole |1〉 → |2〉 and |2〉 → |3〉 and quadrupole |1〉 → |3〉 transitions, respectively, is studied. QI in the excited state population is observed due to two alternative excitation pathways. This is equivalent to nonlinear mixing of the three excitation fields by the atom. Realizing that in the experiment the three fields are spaced in frequency over a range of 25 THz, and extending this scheme to other energy triplets and atoms, leads to the discovery that ranges up to 100's of THz can be bridged in a single mixing step. Motivated by these results, a master equation model has been developed for the system and its properties have been extensively studied.

Ocorrência e ecotoxicidade de desreguladores endócrinos químicos em ambientes aquáticos e em sistemas de tratamento de esgoto

A aplicabilidade de um método selecionado de medição indireta de vitelogenina (Vtg) em plasma sanguíneo de peixe, baseado na quantificação de fosfato álcali-lábil (alkali-labile phosphate-ALP) para acessar estrogenicidade em água, foi investigada na presente tese. O método foi originalmente desenvolvido para a espécie de peixe Carassius carassius (Carpa cruciana) e aplicado pela primeira vez na espécie Oreochromis niloticus (Tilápia do Nilo) no presente estudo. Com o objetivo de acessar a sensibilidade do método, em uma primeira etapa da investigação foram realizados estudos laboratoriais com soluções estoques de 17-ethinylestradiol (EE2), 17-estradiol (E2), e estrona (E1). Os efeitos destes hormônios foram investigados com base tanto na concentração quanto na carga, utilizando-se para tanto, unidades experimentais com volumes distintos (2 L e 130 L). Após a validação do método de ALP, a estrogenicidade foi avaliada nas seguintes águas contaminadas: (i) afluente e efluente de uma grande estação de tratamento de esgotos convencional (ETE) e de uma estação descentralizada de tratamento de esgoto de pequeno porte (Ecossistema Engenheirado-DEE); (ii) água superficial (SW) e água subterrânea (GW) coletadas em uma área de brejo contaminada com gasolina; (iii) água de uma lagoa urbana (LRF) da cidade do Rio de Janeiro, com alta densidade populacional e descarte clandestino de esgoto. Na segunda etapa foram analisados em microalgas os efeitos (outros que não disrupção endócrina) causados pelos hormônios EE2, E2 e E1. Os hormônios foram testados individualmente e em misturas, em culturas individuais e combinada (S+) das espécies de microalgas unicelulares P. subcapitata e D. subspicatus. Com base nos níveis de ALP para a espécie de peixe e no EC50 para as espécies de algas, os resultados mostraram que o EE2 e o E2 causaram disrupção endócrina superior e foram mais tóxicos do que o E1 para peixes e microalgas respectivamente. Quando em misturas (E+) de concentrações equivalentes (EE2:E2:E1), os estrogênios resultaram em efeito aditivo para as espécies O. niloticus e P. subcapitata, e menos que aditivo para D. subspicatus e cultivo misto de algas (S+). Culturas contendo ambas as espécies de algas (S+) por um longo período de exposição (96 h) resultaram na atenuação dos efeitos tóxicos causados pela exposição, tanto individual (EE2, E2 ou E1), quanto na mistura (E+) dos estrogênios, medidos em termos de EC50 (T0h 0,07; 0,09; 0,18; e 0,06 g mL-1; e T96h 1,29; 1,87; 5,58; e 4,61 g mL-1, respectivamente). O DEE apresentou uma maior eficiência na remoção dos disrutores endócrinos do que a ETE convencional. Foi detectada estrogenicidade em amostras da LRF, e de água SW e GW em área brejosa contaminada com gasolina. Os resultados dos ensaios sugerem que as interações (efeitos aditivos ou menos que aditivo) causadas pela mistura dos estrogênios assim como, as interações entre as espécies de algas afetaram o resultado final dos ensaios ecotoxicológicos. Um fator raramente abordado em estudos ecotoxicológicos que foi destacado na presente tese refere-se à importância de considerar não somente a concentração e a dosagem, mas também a carga aplicada e o volume das unidades experimentais. Devido à boa sensibilidade do O. niloticus quando exposto às concentrações relativamente baixas dos estrogênios, a combinação do método de ALP com os biomarcadores auxiliares (particularmente MN) pode ser um protocolo adequado para a detecção de estogenicidade e genotoxicidade respectivamente em diferentes ambiente aquáticos contaminados, como parte de um programa de monitoramento ambiental

克氏针茅(Stipa krylovii Roshev.)草原植物凋落物分解特性及其对环境变化的响应

凋落物的分解对生物地球化学循环起着重要的作用。本研究以位于中国北方农牧交错区（内蒙古多伦县）的半干旱克氏针茅(Stipa krylovii Roshev.)草原生态系统为背景，针对凋落物分解研究中的几个关键过程和问题进行了探讨。研究内容包括该生态系统中几种常见植物凋落物的分解速率，在分解过程中的养分动态，凋落物的混合效应（即非加性效应）及其机制，全球变化引起的土壤有效N、P和降水增加对凋落物分解的影响及其对草原生态系统碳储量的影响等。 通过对克氏针茅、糙隐子草(Cleistogenes squarrosa Trin.)、双齿葱(Allium bidentatum Fisch.)、野韭(Allium ramosum L. Sp. Pl.)和冰草(Agropyron cristatum Gaertn.)的叶、茎、根凋落物的研究发现，叶和茎的分解速率与凋落物初始N和P含量呈显著正相关，根系的分解速率与初始C/N比呈显著负相关。根系凋落物一般比叶和茎凋落物分解速率快，而且具有更快的养分周转速率。有些凋落物混合在一起分解后对分解速率产生了混合效应（混合凋落物的实际分解速率偏离于基于组分凋落物计算的预期分解速率），同时它们对养分（主要是N、P、Ca、Mg）的固定或释放被延后。混合效应发生与否以及混合效应的方向主要取决于组分凋落物的特点，而与凋落物多样性的高低没有明显的关系。混合凋落物对养分动态的负作用，能降低退化生态系统遭到干扰后养分的损失，而且养分释放时间的延后有助于某些植物更好地生长，有利于退化草原生态系统恢复过程中植被结构的改善。 由于凋落物的质量对分解速率的影响重大，凋落物的化学组成很可能对混合凋落物分解过程中的非加性效应起重要作用，然而迄今为止没有明确的结论。本文研究发现，具有不同初始N、P含量的凋落物（同一物种）混合在一起分解后产生了正的非加性效应，非加性效应的强弱与组分凋落物初始N、P含量的差异大小有关。而且，非加性效应与P含量差异大小的相关性比与N的强，这可能与研究地点土壤中P的含量相对更为缺乏有关。这一研究结果表明，凋落物的化学组成在有些情况下确实与非加性效应有关。 通过施肥和浇水试验，研究了全球变化引起的土壤有效N、P和水分的增加对具有不同生活型和化学组成的两种优势草原植物，即双齿葱和克氏针茅凋落物分解的直接影响。结果发现，向土壤中添加N肥或N、P复合肥，在短期内（100天）加速了这两种植物的分解速率。高质量凋落物（双齿葱）的分解更容易受到土壤水分条件的限制，而低质量凋落物（克氏针茅）的分解对土壤养分有效性更敏感。土壤中有效养分的增加会提高分解凋落物对养分的固定，有利于退化生态系统中养分的保持。双齿葱对内蒙古半干旱典型草原的碳循环和养分动态的贡献，比克氏针茅要更大。研究结果提示人们，对草原生态系统的碳循环和养分动态进行模拟时，需要对不同化学组成的凋落物分别加以考虑。 本文还探讨了土壤有效N长期增加后对两种优势草原植物（克氏针茅和冷蒿(Artemisia frigida Willd)）凋落物分解的综合影响，并进一步区分了由土壤有效N增加引起的凋落物质量改变的间接作用和土壤状况改变的直接作用。结果发现，土壤有效N长期增加后对凋落物的分解速率没有明显影响，但是显著加速了分解凋落物对养分的固定，这可能是由于凋落物质量对分解的促进作用和土壤状况对分解的抑制作用相互抵消的原因所造成的。向土壤中添加N素后，地上部植被生产力不可避免的会提高，尽管短期内会加速凋落物的分解速率，但从长远来看，对凋落物的分解速率不会产生影响，所以估计土壤有效N增加后最终会提高草原生态系统的净碳储量。 通过本研究，对中国北方农牧交错区（内蒙古多伦县）半干旱克氏针茅草原生态系统的养分循环过程有了初步的了解，验证了混合凋落物分解过程中非加性效应发生的可能性，并且证明组分凋落物的初始化学组成对这种非加性效应确实起着重要作用。本研究说明全球变化对不同植物种凋落物分解的影响是不同的，而且因研究时间长短的不同对凋落物分解的影响会发生变化。研究结果为草原生态系统碳和养分循环过程的模拟提供了必要的基础资料，为混合凋落物分解过程中非加性效应发生的可能机制提供了强有力的证据，对在全球变化背景下人们对草原生态系统碳和养分循环过程的认识和模拟有着重要的参考价值。

寄生植物在入侵植物防治中的作用——以两种菟丝子为例

生物入侵在全世界广泛发生，目前已经受到全球关注。入侵生物对群落生物多样性和生态系统功能造成严重威胁，导致严重的环境问题和惨重的经济损失。薇甘菊(Mikania micrantha)、五爪金龙(Ipomoea cairica)和南美蟛蜞菊(Wedelia trilobata)是我国华南地区危害最严重的三种外来入侵种，其中以薇甘菊危害最严重，是世界十大有害杂草之一。从20世纪80年代发生以来，薇甘菊已在我国广东农林区域造成严重危害。 机械防治、化学防治和传统的生物防治等治理措施，未能有效治理外来入侵种的危害，直到使用本地种菟丝子(Cuscuta spp)的防治策略。与从原产地引进有害生物天敌的传统生物防治方法不同，本地种由于适应当地气候且与其他物种协同进化，因此，对生态环境潜在的负作用小。从2000年，被发现寄生和抑制薇甘菊之后，菟丝子被认为是防治薇甘菊的有效措施。 为了探讨菟丝子寄生对外来入侵种的治理，及对入侵群落的恢复，本研究在内伶仃岛的林地(入侵种群落被引入菟丝子寄生1-4年)，以及东莞、深圳和海丰的干扰样地(入侵种群落被菟丝子自然寄生5年以上)开展野外调查。在每个样地分别设立外来种入侵亚群和菟丝子治理亚群，通过测定群落结构与组成、土壤性质与养分含量，以及外来种和菟丝子的生长与养分含量等参数之后，本研究得出以下主要结论。 (1) 虽然，被寄生的外来入侵种薇甘菊、五爪金龙和南美蟛蜞菊通过调节资源分配以抵御南方菟丝子(Cuscuta australis)的寄生影响，但是，菟丝子寄生导致外来入侵种生物量降低、繁殖能力下降、养分含量降低。虽然，很多寄生植物都是广谱寄生，能同时寄生多种寄主植物，但是，在本研究的被入侵的群落中，菟丝子主要寄生外来入侵植物。尤其是寄生于南美蟛蜞菊和薇甘菊的菟丝子，生长旺盛、繁殖能力强，表现出高度的适应性。因此，菟丝子对外来入侵种(南美蟛蜞菊和薇甘菊)有寄生偏好性，并对本地种的负面影响小。 (2) 通过吸收寄主的养分，田野菟丝子(Cuscuta campestris)有效地抑制了薇甘菊的危害。由于入侵种的凋落物养分含量高且分解效率高，而且，菟丝子能够促进其它凋落物的分解，并使难以被植物吸收的养分转化成易于被吸收利用的状态。因此，菟丝子与薇甘菊的寄生作用导致土壤养分含量的升高。在薇甘菊被抑制之后，本地种利用丰富的土壤养分资源，提高生长适应性，增强抵抗入侵的能力，甚至抵制薇甘菊的再生。 (3) 菟丝子的寄生作用改变了外来寄主与本地非寄主的竞争平衡，促进本地植物的生长与重建。在外来种被抑制之后，本地种的丰度和群落的物种多样性逐渐增加。本地种如：野葛(Pueraria lobata)和芦苇(Phragmites australis)，取代了入侵群落中的入侵种，成了群落的优势种。而其它原先被薇甘菊抑制的本地草本、藤本和灌木，在引入菟丝子防治之后长势较好。群落稳定性与物种多样性密切相关，被治理群落本地种的增加有利于群落的演替与稳定。 (4) 被干扰的生态系统往往更容易被外来种入侵，而外来入侵种又常导致人工干扰生境的严重退化。在人工干扰样地的菟丝子对薇甘菊的抑制效果与在林地的效果一致，导致被寄生的薇甘菊生长衰退、养分竞争能力下降、入侵危害能力降低。而在薇甘菊被菟丝子治理之后，土壤养分资源增加，入侵群落的物种丰度和生物多样性提高。本 地种的重建与本地群落的恢复密切相关，利于本地被治理群落的稳定，促进被干扰植被的恢复。 菟丝子是一种治理外来入侵种危害的有效措施，适用于破碎的生境和被干扰的生态系统，尤其是在采用目前防治措施难以治理的情况下。本研究为本地种防治外来入侵种提供科学依据，且表明以入侵地的本地种治理外来入侵种有可能成为有效且可持续发展的生物防治策略。

Influence of specific HSP70 domains on fibril formation of the yeast prion protein Ure2.

Ure2p is the protein determinant of the Saccharomyces cerevisiae prion state [URE3]. Constitutive overexpression of the HSP70 family member SSA1 cures cells of [URE3]. Here, we show that Ssa1p increases the lag time of Ure2p fibril formation in vitro in the presence or absence of nucleotide. The presence of the HSP40 co-chaperone Ydj1p has an additive effect on the inhibition of Ure2p fibril formation, whereas the Ydj1p H34Q mutant shows reduced inhibition alone and in combination with Ssa1p. In order to investigate the structural basis of these effects, we constructed and tested an Ssa1p mutant lacking the ATPase domain, as well as a series of C-terminal truncation mutants. The results indicate that Ssa1p can bind to Ure2p and delay fibril formation even in the absence of the ATPase domain, but interaction of Ure2p with the substrate-binding domain is strongly influenced by the C-terminal lid region. Dynamic light scattering, quartz crystal microbalance assays, pull-down assays and kinetic analysis indicate that Ssa1p interacts with both native Ure2p and fibril seeds, and reduces the rate of Ure2p fibril elongation in a concentration-dependent manner. These results provide new insights into the structural and mechanistic basis for inhibition of Ure2p fibril formation by Ssa1p and Ydj1p.

Influence of specific HSP70 domains on fibril formation of the yeast prion protein Ure2.

Ure2p is the protein determinant of the Saccharomyces cerevisiae prion state [URE3]. Constitutive overexpression of the HSP70 family member SSA1 cures cells of [URE3]. Here, we show that Ssa1p increases the lag time of Ure2p fibril formation in vitro in the presence or absence of nucleotide. The presence of the HSP40 co-chaperone Ydj1p has an additive effect on the inhibition of Ure2p fibril formation, whereas the Ydj1p H34Q mutant shows reduced inhibition alone and in combination with Ssa1p. In order to investigate the structural basis of these effects, we constructed and tested an Ssa1p mutant lacking the ATPase domain, as well as a series of C-terminal truncation mutants. The results indicate that Ssa1p can bind to Ure2p and delay fibril formation even in the absence of the ATPase domain, but interaction of Ure2p with the substrate-binding domain is strongly influenced by the C-terminal lid region. Dynamic light scattering, quartz crystal microbalance assays, pull-down assays and kinetic analysis indicate that Ssa1p interacts with both native Ure2p and fibril seeds, and reduces the rate of Ure2p fibril elongation in a concentration-dependent manner. These results provide new insights into the structural and mechanistic basis for inhibition of Ure2p fibril formation by Ssa1p and Ydj1p.

Reproductive effects of prenatal exposure to nonylphenol on zebrafish (Danio rerio)

Mature female and male zebrafish were separated and exposed to nonylphenol (NP) at 0.1, 1, 10, 50, 100 and 500 mu g/L, respectively, for 3 weeks. Gonadosomatic index (GSI) in both sexes and vitellogenin (VTG) induction in males was measured as the bioindicators for the impairment to the parents. The results indicated that 50 mu g/L of NP was the non-observed effect concentration (NOEC) for GSI and VTG induction. Afterwards, the 50 mu g/L NP exposed females and males, and the control females and males were cross-wise pair-bred in the control water for one week to examine the reproductive effects. The embryonic cathepsin D (CAT D) activity, eggshell thickness, fecundity, hatching rate and malformation (vertebral column flexure) rate of offspring were determined in the four pair-bred groups. While endpoints remained unchanged in the groups with exposed males, prenatal exposure of females to 50 mu g/L of NP resulted in the impairment of reproduction in groups with exposed females including inhibition of CAT D activity (P < 0.05), decrease of eggshell thickness (by 23.6%) and elevation of malformation rate (P < 0.001). These results suggested NP could induce reproductive damage to zebrafish at NOEC for parents. The results also imply that alterations of CAT D activity and eggshell thickness may be more sensitive biomarkers to indicate the reproductive effects caused by endocrine disrupting chemicals. (c) 2005 Elsevier Inc. All rights is reserved.

沙棘(Hippophae rhamnoides L.)在低温和增强UV-B胁迫下的生态生理反应

植物生长和生产力受到自然界各种形式的生物和非生物胁迫因子的影响。这些胁迫包括低温、高温、盐碱、干旱、洪水、重金属、虫害、病害和紫外线辐射等等。而人类活动大大加剧了这些胁迫所带来的影响。由于人类污染而导致臭氧层衰减以及由此产生的地球表面紫外辐射增强已经成为全球气候变化的一个主要方面。UV-B胁迫，甚至当前的辐射水平，所带来的影响已经引起科学工作者的广泛关注。 为了生存和繁殖，植物不得不面临环境中各种潜在胁迫所带来的负面影响。然而，植物生活型的不可移动性决定了其逃避胁迫的局限性。因此，绝大多数植物都是通过对胁迫作出反应，通过修复或者更新组织来降低伤害。而植物应对环境变化的能力则是由其生长模式的种属特异性和本身的遗传组成所决定。在自然界，植物常常同时面临多种胁迫，这些胁迫所引发的植物反应可能具有叠加、协同或者拮抗作用。沙棘是一种具刺、具有固氮功能的多年生雌雄异株灌木，广泛分布于亚欧大陆的温带地区和亚洲亚热带的高海拔地区。在中国，沙棘常常被用作植被恢复中的先锋树种而大量栽培。本文采用沙棘作为模式植物，试图探索木本植物对低温，UV-B辐射增强以及其与干旱的复合胁迫的响应以及沙棘对这些胁迫响应是否具有种群差异性。 对来自南北两个种群的沙棘进行短日照和低温处理，检测了其在抗寒锻炼和抗寒性发育过程中存在的性别差异。结果表明，短日照和低温都分别能够诱导抗寒锻炼的发生，而两者同时存在对所有实验植株抗寒性的大小具有叠加效应。然而，短日照和低温所诱导的抗寒性在两个种群中都具有性别差异性，雄性植株比雌雄植株对短日照和低温更为敏感。同时，南北种群间也存在差异性，北方种群的植物比南方种群的植物对短日照和低温敏感，从而在短日照下抗寒锻炼的发生时间更早，低温诱导的抗寒性更大。短日照和低温诱导植物增加抗寒性的同时伴随着脱落酸的变化。脱落酸的变化因处理，种群和性别的不同而不同。这些生理反应表明不同的沙棘种群，不同的植株性别对同一环境胁迫可能存在不同的生存策略。 比较了来自高低两个海拔的沙棘种群对于干旱和UV-B辐射增强以及两者复合胁迫条件下的生理生态反应。干旱使两个种群中植株总的生物量，总叶面积，比叶面积，叶片含碳量，含磷量，木质素含量和碳氮比显著降低，使根冠比，粗根细根比和叶片脱落酸含量显著增加。干旱而非UV-B使得δ13C 值显著增加。但是，比较而言，来自高海拔的种群对干旱反应更为强烈，而来自低海拔的种群对UV-B更敏感。在UV-B辐射增强的处理下，干旱所诱导的脱落酸的积累被显著抑制。而且我们检测到在一些指标上存在显著的干旱×UV-B交互作用，如两个种群中在总生物量上，低海拔种群中在总叶面积，粗根细根比上，高海拔种群中在比叶面积，δ13C值，木质素含量上都存在明显的交互作用。这些结果表明这两个种群对胁迫具有不同的适应性反应，来自高海拔的种群比来自低海拔的种群更能够抵御干旱和UV-B胁迫。 室外实验表明，UV-B 去除/增补对沙棘高低两个海拔种群的影响都不大。对生物量的积累，植株高度以及一些常见的胁迫反应生理指标比如丙二醛、ABA 和游离脯氨酸都没有显著影响。UV-B 的效应比UV-A 大，植物反应在无UV 和仅有UV-A 的处理间没有什么区别。然而，UV-B 去除的两个处理和UV-B 存在的两个处理间存在显著区别。UV-B 使得两个种群都显著降低了比叶面积(SLA)，但却使长期用水效率增加。但UV-B对光合色素和光合系统II 的影响不大。总体看来，来自低海拔的种群对UV-B 更为敏感。 Plant is adversely affected by various abiotic and biotic stress factors. These stressors includelow temperature, heat, salt, drought, flooding, heavy metal toxicity, wounding by herbivores,infecting by pathogenic microorganisms, ultraviolet (UV) radiation and so on. Variousanthropogenic activities have accentuated the existing stress factors. One of the mostimportant aspects of global change is that of stratospheric ozone depletion caused by seriousanthropogenic pollution and the resulting increase in UV radiation reaching the surface of theEarth. Scientists have become concerned about the effects that considerable UV-B stress, evenat current levels. In order to survive and reproduce, plants have to be able to cope with lots of potentiallyharmful stress factors that are almost constantly present in their environment. Most plants’responses under stress are to neutralize the stress, repairing the damage or regrowing newtissue rather than to avoid it due to their sessile life style. The plant defense capacity dependson plant-specific modular growth patterns and genetic make-up that allows for flexibleresponses to changing environments. Plants usually encounter several stresses simultaneouslyunder field conditions, and the stresses may cause a variety of plant responses, which can beadditive, synergistic or antagonistic. Sea buckthorn (Hippophae rhamnoides L.), a thorny nitrogen fixing deciduously perennialshrub, which is widely distributed throughout the temperate zones of Asia and Europe and thesubtropical zones of Asia at high altitudes. It has been widely used in forest restoration as thepioneer species in China. In this paper, we used sea buckthorn as a model, tried to get some understand of how plants fight low temperature, enhanced UV-B radiation level and thatcombination of drought. And also, want to know whether does there exist some populationspecific responses to such stressors. Sexual differences in cold acclimation and freezing tolerance development of two contrastingsea buckthorn (Hippophae rhamnoides L.) ecotypes from northern and southern regions inChina were recorded after exposure to short day photoperiod (SD) and low temperature (LT).The results demonstrated that cold acclimation could be triggered by exposing the plants toSD or LT alone, and that a combination of both treatments had an additive effect on freezingtolerance in all plants tested. However, development of freezing tolerance was dependent onthe sex of plants under SD and LT, the males were clearly more responsive to SD and LT thanthe females in both ecotypes studied. On the other hand, development of freezing tolerancewas also ecotype-dependent, the northern ecotype was more responsive to SD and LT than thesouthern ecotype, resulting in earlier cold acclimation under SD and higher freezing toleranceunder LT. Moreover, development of freezing tolerance induced by SD and LT wasaccompanied by changes in ABA levels. These alterations in ABA levels were different indifferent treatments, ecotypes and sexes. Therefore, the differences in SD and LT-inducedphysiological responses showed that the different ecotypes and the different sexes mightemploy different survival strategies under environmental stress. Two contrasting populations from the low and high altitudinal regions were employed toinvestigate the effects of drought, UV-B and their combination on sea buckthorn. Droughtsignificantly decreased total biomass, total leaf area, specific leaf area，leaf carbon (C),phophous (P), lignin content and the ratio of C: N in both populations, and increasedroot/shoot ratio, fine root/coarse root ratio and abscisic acid content (ABA), in bothpopulations. Drought but not UV-B resulted in significantly greater carbon isotopecomposition (δ13C) values in both populations. However, the high altitudinal population wasmore responsive to drought than the low altitudinal population. The drought-inducedenhancement of ABA in the high altitudinal population was significantly suppressed in thecombination of drought and elevated UV-B. Moreover, significant drought × UV-B interactionwas detected on total biomass in both populations, total leaf area and fine root/coarse root inthe low altitudinal population, specific leaf area, δ13C value and leaf lignin content in the high altitudinal population. These results demonstrated that there were different adaptive responsesbetween two contrasting populations, the high altitudinal population exhibited highertolerance to drought and UV-B than the low altitudinal population. A field experiment was conducted to investigate effects of UV-B exclusion/supplementationon two altitudinal populations of sea buckthorn. UV-B exclusion or supplementation had littleeffects on both populations investigated. For instance, the total biomass, plant height andsome physiological index such as Malondialdehyde (MDA), ABA and free proline were notchanged significantly. The UV-B effects are more significant than that of UV-A, nodifferences were found between treatments of excluded UV and excluded UV-B. However,compared with treatments of UV-B exclusion (including absent of UV-B and all UV band),the present of UV-B (including near ambient environment and enhanced UV-B) significantdecreased specific leaf area, and increased long time water use efficiency as evaluated by δ13Cvalue. UV-B had little effects on photosynthetic pigments and Photosystem II (PSII). The lowaltitude population is more sensitive to UV-B than that of the high altitude population.

Radiosensitivity to high energy iron ions is influenced by heterozygosity for Atm, Rad9 and Brca1

Loss of function of DNA repair genes has been implicated in the development of many types of cancer. In the last several years, heterozygosity leading to haploinsufficiency for proteins involved in DNA repair was shown to play a role in genomic instability and carcinogenesis after DNA damage is induced, for example by ionizing radiation. Since the effect of heterozygosity for one gene is relatively small, we hypothesize that predisposition to cancer could be a result of the additive effect of heterozygosity for two or more genes critical to pathways that control DNA damage signaling, repair or apoptosis. We investigated the role of heterozygosity for Aim, Rad9 and Brad on cell oncogenic transformation and cell survival induced by 1 GeV/n Fe-56 ions. Our results show that cells heterozygous for both Aim and Rad9 or A tin and Brca1 have high survival rates and are more sensitive to transformation by high energy iron ions when compared with wild-type controls or cells haploinsufficient for only one of these proteins. Since mutations or polymorphisms for similar genes exist in a small percentage of the human population, we have identified a radiosensitive sub-population. This finding has several implications. First, the existence of a radiosensitive sub-population may distort the shape of the dose response relationship. Second, it would not be ethical to put exceptionally radiosensitive individuals into a setting where they may potentially be exposed to substantial doses of radiation. (C) 2010 COSPAR. Published by Elsevier Ltd. All rights reserved.

Hemizygosity for Atm and Brca1 influence the balance between cell transformation and apoptosis

Background: In recent years data from both mouse models and human tumors suggest that loss of one allele of genes involved in DNA repair pathways may play a central role in genomic instability and carcinogenesis. Additionally several examples in mouse models confirmed that loss of one allele of two functionally related genes may have an additive effect on tumor development. To understand some of the mechanisms involved, we examined the role of monoallelic loss or Atm and Brca1 on cell transformation and apoptosis induced by radiation. Methods: Cell transformation and apoptosis were measured in mouse embryo fibroblasts (MEF) and thymocytes respectively. Combinations of wild type and hemizygous genotypes for ATM and BRCA1 were tested in various comparisons. Results: Haploinsufficiency of either ATM or BRCA1 resulted in an increase in the incidence of radiation-induced transformation of MEF and a corresponding decrease in the proportion of thymocytes dying an apoptotic death, compared with cells from wild-type animals. Combined haploinsufficiency for both genes resulted in an even larger effect on apoptosis. Conclusions: Under stress, the efficiency and capacity for DNA repair mediated by the ATM/BRCA1 cell signalling network depends on the expression levels of both proteins.

Glucose-lowering activity of amino acid-N-phosphonic acid oxovanadium complexes and its interaction with DNA

Vanadium has well-documented lowering glucose properties both in vitro and in vivo. The design of new oxovanadium(IV) coordination compounds, intended for use as insulin-enhancing agents in the treatment of diabetes mellitus, can potentially benefit from a synergistic approach, in which the whole complex has more than an additive effect from its component parts. Biological testing with oxovanadium(IV) organic phosphonic acid, for insulin-enhancing potential included acute administration, by oral gavage in streptozotocin (STZ) diabetic rats. The complexes of oxovanadium(IV) amino acid-N-phosphonic acid exhibit higher lowering glucose activity in vivo. The interaction of the complexes of oxovanadium(IV) amino acid-N-phosphonic acid with DNA was investigated by agarose gel electrophoresis. The results indicated that these complexes have strong interaction with DNA.

Genetic parameter estimates for growth traits at early stage of Pacific abalone, Haliotis discus hannai Ino

Heritability and genetic and phenotypic correlations were estimated for juvenile growth traits of Pacific abalone Haliotis discus hannai Ino. The estimates were calculated from shell length and shell width measurements on progeny resulting from 12 half-sib families and 36 full-sib families obtained using artificial fertilization of mating three females to each male. The measurements were taken at 10, 20 and 30 d after fertilization. It was found that heritability estimates based on sire component ranged from 0.23 to 0.36 for shell length and 0.21 to 0.32 for shell width. Heritability estimates from dam component were larger than those from sire component at three ages, indicating presence of maternal effects, non-additive genetic effects and common environmental effects. Phenotypic correlations were significant at three ages (P < 0.05), with values of 0.92, 0.93 and 0.92, respectively. Genetic correlations from the paternal half-sib correlation analysis were highly positive at three ages, with values of 0.50, 0.78 and 0.81, respectively. The results suggest that selective breeding is an effective approach to improving growth traits of Pacific abalone stocks.