Electron-induced oxygen desorption from the TiO2(011)-2x1 surface leads to self-organized vacancies     

Dulub O  Batzilln M  Solovev S  Loginova E  Alchagirov A  Madey TE  Diebold U 《Science (New York, N.Y.)》2007,317(5841):1052-1056

When low-energy electrons strike a titanium dioxide surface, they may cause the desorption of surface oxygen. Oxygen vacancies that result from irradiating a TiO2(011)-2x1 surface with electrons with an energy of 300 electron volts were analyzed by scanning tunneling microscopy. The cross section for desorbing oxygen from the pristine surface was found to be 9 (+/-6) x 10(-17) square centimeters, which means that the initial electronic excitation was converted into atomic motion with a probability near unity. Once an O vacancy had formed, the desorption cross sections for its nearest and next-nearest oxygen neighbors were reduced by factors of 100 and 10, respectively. This site-specific desorption probability resulted in one-dimensional arrays of oxygen vacancies.  相似文献   

Stomatal patterning and differentiation by synergistic interactions of receptor kinases     

Shpak ED  McAbee JM  Pillitteri LJ  Torii KU 《Science (New York, N.Y.)》2005,309(5732):290-293

Coordinated spacing and patterning of stomata allow efficient gas exchange between plants and the atmosphere. Here we report that three ERECTA (ER)-family leucine-rich repeat-receptor-like kinases (LRR-RLKs) together control stomatal patterning, with specific family members regulating the specification of stomatal stem cell fate and the differentiation of guard cells. Loss-of-function mutations in all three ER-family genes cause stomatal clustering. Genetic interactions with a known stomatal patterning mutant too many mouths (tmm) revealed stoichiometric epistasis and combination-specific neomorphism. Our findings suggest that the negative regulation of ER-family RLKs by TMM, which is an LRR receptor-like protein, is critical for proper stomatal differentiation.  相似文献   

Hexameric structure and assembly of the interleukin-6/IL-6 alpha-receptor/gp130 complex     

Boulanger MJ  Chow DC  Brevnova EE  Garcia KC 《Science (New York, N.Y.)》2003,300(5628):2101-2104

Interleukin-6 (IL-6) is an immunoregulatory cytokine that activates a cell-surface signaling assembly composed of IL-6, the IL-6 alpha-receptor (IL-6Ralpha), and the shared signaling receptor gp130. The 3.65 angstrom-resolution structure of the extracellular signaling complex reveals a hexameric, interlocking assembly mediated by a total of 10 symmetry-related, thermodynamically coupled interfaces. Assembly of the hexameric complex occurs sequentially: IL-6 is first engaged by IL-6Ralpha and then presented to gp130in the proper geometry to facilitate a cooperative transition into the high-affinity, signaling-competent hexamer. The quaternary structures of other IL-6/IL-12 family signaling complexes are likely constructed by means of a similar topological blueprint.  相似文献   

European seasonal and annual temperature variability, trends, and extremes since 1500   总被引：2，自引：0，他引：2  

Luterbacher J  Dietrich D  Xoplaki E  Grosjean M  Wanner H 《Science (New York, N.Y.)》2004,303(5663):1499-1503

Multiproxy reconstructions of monthly and seasonal surface temperature fields for Europe back to 1500 show that the late 20th- and early 21st-century European climate is very likely (>95% confidence level) warmer than that of any time during the past 500 years. This agrees with findings for the entire Northern Hemisphere. European winter average temperatures during the period 1500 to 1900 were reduced by approximately 0.5 degrees C (0.25 degrees C for annual mean temperatures) compared to the 20th century. Summer temperatures did not experience systematic century-scale cooling relative to present conditions. The coldest European winter was 1708/1709; 2003 was by far the hottest summer.  相似文献   

Toll-like receptor 4-dependent activation of dendritic cells by beta-defensin 2   总被引：1，自引：0，他引：1  

Biragyn A  Ruffini PA  Leifer CA  Klyushnenkova E  Shakhov A  Chertov O  Shirakawa AK  Farber JM  Segal DM  Oppenheim JJ  Kwak LW 《Science (New York, N.Y.)》2002,298(5595):1025-1029

beta-Defensins are small antimicrobial peptides of the innate immune system produced in response to microbial infection of mucosal tissue and skin. We demonstrate that murine beta-defensin 2 (mDF2beta) acts directly on immature dendritic cells as an endogenous ligand for Toll-like receptor 4 (TLR-4), inducing up-regulation of costimulatory molecules and dendritic cell maturation. These events, in turn, trigger robust, type 1 polarized adaptive immune responses in vivo, suggesting that mDF2beta may play an important role in immunosurveillance against pathogens and, possibly, self antigens or tumor antigens.  相似文献   

Effectiveness of donor natural killer cell alloreactivity in mismatched hematopoietic transplants     

Ruggeri L  Capanni M  Urbani E  Perruccio K  Shlomchik WD  Tosti A  Posati S  Rogaia D  Frassoni F  Aversa F  Martelli MF  Velardi A 《Science (New York, N.Y.)》2002,295(5562):2097-2100

T cells that accompany allogeneic hematopoietic grafts for treating leukemia enhance engraftment and mediate the graft-versus-leukemia effect. Unfortunately, alloreactive T cells also cause graft-versus-host disease (GVHD). T cell depletion prevents GVHD but increases the risk of graft rejection and leukemic relapse. In human transplants, we show that donor-versus-recipient natural killer (NK)-cell alloreactivity could eliminate leukemia relapse and graft rejection and protect patients against GVHD. In mice, the pretransplant infusion of alloreactive NK cells obviated the need for high-intensity conditioning and reduced GVHD. NK cell alloreactivity may thus provide a powerful tool for enhancing the efficacy and safety of allogeneic hematopoietic transplantation.  相似文献   

Antimicrobial Action of Compounds from Marine Seaweed     

María José Pérez  Elena Falqué  Herminia Domínguez 《Marine drugs》2016,14(3)

Seaweed produces metabolites aiding in the protection against different environmental stresses. These compounds show antiviral, antiprotozoal, antifungal, and antibacterial properties. Macroalgae can be cultured in high volumes and would represent an attractive source of potential compounds useful for unconventional drugs able to control new diseases or multiresistant strains of pathogenic microorganisms. The substances isolated from green, brown and red algae showing potent antimicrobial activity belong to polysaccharides, fatty acids, phlorotannins, pigments, lectins, alkaloids, terpenoids and halogenated compounds. This review presents the major compounds found in macroalga showing antimicrobial activities and their most promising applications.  相似文献   

Francesca Gherardi     

Elena Tricarico 《水产资源保护:海洋与淡水生态系统》2013,23(2):183-183

  相似文献   

Effects of dietary soy isoflavones on estrogenic activity,cortisol level,health and growth in rainbow trout,Oncorhynchus mykiss          下载免费PDF全文

Maria Rita Pastore  Elena Negrato  Carlo Poltronieri  Giuseppe Barion  Maria Messina  Francesca Tulli  Cristina Ballarin  Lisa Maccatrozzo  Giuseppe Radaelli  Daniela Bertotto 《Aquaculture Research》2018,49(4):1469-1479

Soy isoflavones (the phytoestrogens genistein, daidzein and glycitein) may act as estrogen receptor agonists or antagonists. The aim of this study was to examine the effect of dietary isoflavones on growth, reproduction and health in rainbow trout (Oncorhynchus mykiss). Rainbow trout fed three experimental diets containing different concentrations of isoflavones (0, 500 and 1,500 ppm). Growth, estrogenic activity, plasma estradiol levels, gonadal development, state of stress and histological changes in selected tissues were evaluated at the end of 70 days. Neither growth performance nor the relative mRNA levels of Insulin Growth Factor I (igf‐I) in the liver were influenced by different levels of dietary isoflavones. Plasma and liver vitellogenin (VTG) protein levels and plasma 17‐β‐estradiol (E₂) were unaffected by treatments, although the correlation between plasma levels of E₂ and VTG densitometry values was significant (p < .05). The fish gonadosomatic index (GSI) did not significantly differ among the three experimental groups but correlated with plasma VTG densitometry values (p < .05). Plasma, muscle and fin cortisol concentrations fell within the normal welfare range and were not correlated with isoflavone levels. Histologically, the distal intestine showed a normal morphology with well‐differentiated enterocytes and in the liver hepatocytes were also normal. A supranuclear accumulation of lipid droplets in enterocytes and some lipid droplets in hepatocytes were observed in all tested groups, suggesting an impact of basal dietary lipid on transport/metabolism of fat in the fish. Overall, the present results suggest that the doses of isoflavones tested do not compromise rainbow trout reproduction, growth and health.  相似文献   

Pan‐continental invasion of Pseudorasbora parva: towards a better understanding of freshwater fish invasions     

Rodolphe E Gozlan  Demetra Andreou  Takashi Asaeda  Kathleen Beyer  Rachid Bouhadad  Dean Burnard  Nuno Caiola  Predrag Cakic  Vesna Djikanovic  Hamid R Esmaeili  Istvan Falka  Duncan Golicher  Akos Harka  Galina Jeney  Vladimír Kováč  Jiří Musil  Annamaria Nocita  Meta Povz  Nicolas Poulet  Tomas Virbickas  Christian Wolter  A Serhan Tarkan  Elena Tricarico  Teodora Trichkova  Hugo Verreycken  Andrzej Witkowski  Chun Guang Zhang  Irene Zweimueller  J Robert Britton 《Fish and Fisheries》2010,11(4):315-340

In recent years, policy‐makers have sought the development of appropriate tools to prevent and manage introductions of invasive species. However, these tools are not well suited for introductions of non‐target species that are unknowingly released alongside intentionally‐introduced species. The most compelling example of such invasion is arguably the topmouth gudgeon Pseudorasbora parva, a small cyprinid species originating from East Asia. A combination of sociological, economical and biological factors has fuelled their rapid invasion since the 1960s; 32 countries (from Central Asia to North Africa) have been invaded in less than 50 years. Based on a combination of monitoring surveys (2535 populations sampled) and literature reviews, this paper aims to quantify and characterise important invasion parameters, such as pathways of introduction, time between introduction and detection, lag phase and plasticity of life history traits. Every decade, five new countries have reported P. parva introduction, mainly resulting from the movement of Chinese carps for fish farming. The mean detection period after first introduction was 4 years, a duration insufficient to prevent their pan‐continental invasion. High phenotypic plasticity in fitness related traits such as growth, early maturity, fecundity, reproductive behaviour and the ability to cope with novel pathogens has predisposed P. parva to being a strong invader. The Pseudorasbora parva invasion has provided quantitative data for the development of 1) early warning systems across different spatial scales; 2) rapid eradication programmes prior to natural spread in open systems and 3) sound risk assessments with emphasis on plasticity of life history traits.  相似文献