Heterogeneous nucleation experiments bridging the scale from molecular ion clusters to nanoparticles     

Winkler PM  Steiner G  Vrtala A  Vehkamäki H  Noppel M  Lehtinen KE  Reischl GP  Wagner PE  Kulmala M 《Science (New York, N.Y.)》2008,319(5868):1374-1377

Generation, investigation, and manipulation of nanostructured materials are of fundamental and practical importance for several disciplines, including materials science and medicine. Recently, atmospheric new particle formation in the nanometer-size range has been found to be a global phenomenon. Still, its detailed mechanisms are mostly unknown, largely depending on the incapability to generate and measure nanoparticles in a controlled way. In our experiments, an organic vapor (n-propanol) condenses on molecular ions, as well as on charged and uncharged inorganic nanoparticles, via initial activation by heterogeneous nucleation. We found a smooth transition in activation behavior as a function of size and activation to occur well before the onset of homogeneous nucleation. Furthermore, nucleation enhancement for charged particles and a substantial negative sign preference were quantitatively detected.  相似文献   

The antibacterial lectin RegIIIgamma promotes the spatial segregation of microbiota and host in the intestine   总被引：1，自引：0，他引：1  

Vaishnava S  Yamamoto M  Severson KM  Ruhn KA  Yu X  Koren O  Ley R  Wakeland EK  Hooper LV 《Science (New York, N.Y.)》2011,334(6053):255-258

The mammalian intestine is home to ~100 trillion bacteria that perform important metabolic functions for their hosts. The proximity of vast numbers of bacteria to host intestinal tissues raises the question of how symbiotic host-bacterial relationships are maintained without eliciting potentially harmful immune responses. Here, we show that RegIIIγ, a secreted antibacterial lectin, is essential for maintaining a ~50-micrometer zone that physically separates the microbiota from the small intestinal epithelial surface. Loss of host-bacterial segregation in RegIIIγ(-/-) mice was coupled to increased bacterial colonization of the intestinal epithelial surface and enhanced activation of intestinal adaptive immune responses by the microbiota. Together, our findings reveal that RegIIIγ is a fundamental immune mechanism that promotes host-bacterial mutualism by regulating the spatial relationships between microbiota and host.  相似文献   

An outbreak of acute disease and mortality in Atlantic salmon (Salmo salar) post‐smolts in Norway caused by Tenacibaculum dicentrarchi     

ystein Klakegg  Takele Abayneh  Aud Kari Fauske  Michael Fülberth  Henning Srum 《Journal of fish diseases》2019,42(6):789-807

An outbreak of disease characterized by skin ulcers, fin rot and mortality was observed a few days after the transfer of Atlantic salmon (Salmo salar) from a freshwater smolt production facility to a land‐based seawater post‐smolt site. Dead and moribund fish had severe skin and muscle ulcers, often 2–6 cm wide, particularly caudal to the pectoral fins. Microscopic examination of smears from ulcers and head kidney identified long, slender Gram‐negative rods. Histopathological analysis revealed abundance of long, slender Tenacibaculum‐like bacteria in ulcers and affected fins. Genetic characterization using multilocus sequence analysis (MLSA) of seven housekeeping genes, including atpA, dnaK, glyA, gyrB, infB, rlmN and tgt, revealed that the isolates obtained during the outbreak were all clustered with the Tenacibaculum dicentrarchi‐type strain (USC39/09^T) from Spain. Two bath challenge experiments with Atlantic salmon and an isolate of T. dicentrarchi from the outbreak were performed. No disease or mortality was observed in the first trial. In the second trial with a higher challenge dose of T. dicentrarchi and longer challenge time, we got 100% mortality within 48 hr. This is the first reported outbreak of disease caused by T. dicentrarchi in Norwegian farmed Atlantic salmon.  相似文献   

桉树的抗旱性研究进展   总被引：9，自引：0，他引：9  

李春阳  Kari Tuomela 《世界林业研究》1998,11(3):22-27

在干旱和半干旱地区,为了成功地栽培桉树,许多学者从不同角度对桉树种群的抗旱性机理和它们对不同干旱环境的反应进行了研究和探讨。结果认为,桉树种群的遗传基因能适应于干旱的环境。生长在水分短缺条件下的植株,是通过各种途径保持组织水含量在细胞免受伤害的临界值以上而达到其适应。一般来说,具有旱生植物特征的桉树种群对干旱的适应能力较强,它们能够生存在较干旱的环境条件下,但不可能从湿润的气候环境中取得生长优势。  相似文献   

Mutations in voltage‐gated sodium channels from pyrethroid resistant salmon lice (Lepeophtheirus salmonis)     

Greta Carmona‐Antoanzas  Kari O Helgesen  Joseph L Humble  Claudia Tschesche  Marit J Bakke  Louise Gamble  Michaël Bekaert  David I Bassett  Tor E Horsberg  James E Bron  Armin Sturm 《Pest management science》2019,75(2):527-536

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Enzymatic and Acidic Hydrolysis of Cationized Waxy Maize Starch Granules     

Robin Manelius  Kari Nurmi  Eric Bertoft 《Cereal Chemistry》2000,77(3):345-353

A series of wet‐cationized starch granules from waxy maize with different degrees of substitution (DS) were solubilized with either 2.2M HCl (lintnerization) or with the α‐amylase of Bacillus amyloliquefaciens. The maximum rate of the enzymatic hydrolysis occurred in starches with intermediate DS. It appeared that the cationic substituents interfered with the binding to the active site of the enzyme at high levels of substitution. The DS remained fairly constant in the granular residues after the enzymatic attack. The rate of the acidic hydrolysis increased with increasing DS but the final level of solubilization slightly decreased. The DS of the residual starch material decreased to 40% of the original level, showing that a large part of the cationic groups was found within the amorphous parts of the granules. A dry‐cationized sample with a high DS was also treated with the acid and lost a major part of its substituents at low levels of lintnerization. Probably most of the substituents were associated with the surface and channels of these granules. The cationized starches possessed branches that were resistant to isoamylase attack and the samples also contained β‐amylolysis resistant dextrins. The proportion of resistant dextrins in the granular residues decreased after lintnerization, but remained constant after the enzymatic hydrolysis.  相似文献   

Relationships Between Gluten Rheological Properties and Hearth Loaf Characteristics     

Kari M. Tronsmo  Ellen Merethe Magnus  Ellen Mosleth Frgestad  J. David Schofield 《Cereal Chemistry》2003,80(5):575-586

The rheological properties of fresh gluten in small amplitude oscillation in shear (SAOS) and creep recovery after short application of stress was related to the hearth breadbaking performance of wheat flours using the multivariate statistics partial least squares (PLS) regression. The picture was completed by dough mixing and extensional properties, flour protein size distribution determined by SE‐HPLC, and high molecular weight glutenin subunit (HMW‐GS) composition. The sample set comprised 20 wheat cultivars grown at two different levels of nitrogen fertilizer in one location. Flours yielding stiffer and more elastic glutens, with higher elastic and viscous moduli (G′ and G″) and lower tan δ values in SAOS, gave doughs that were better able to retain their shape during proving and baking, resulting in breads of high form ratios. Creep recovery measurements after short application of stress showed that glutens from flours of good breadmaking quality had high relative elastic recovery. The nitrogen fertilizer level affected the protein size distribution by an increase in monomeric proteins (gliadins), which gave glutens of higher tan δ and flatter bread loaves (lower form ratio).  相似文献   

Comparison of Small and Large Deformation Rheological Properties of Wheat Dough and Gluten     

Kari M. Tronsmo  Ellen M. Magnus  Pernille Baardseth  J. David Schofield  Anette Aamodt  Ellen Mosleth Frgestad 《Cereal Chemistry》2003,80(5):587-595

The rheological properties of dough and gluten are important for end‐use quality of flour but there is a lack of knowledge of the relationships between fundamental and empirical tests and how they relate to flour composition and gluten quality. Dough and gluten from six breadmaking wheat qualities were subjected to a range of rheological tests. Fundamental (small‐deformation) rheological characterizations (dynamic oscillatory shear and creep recovery) were performed on gluten to avoid the nonlinear influence of the starch component, whereas large deformation tests were conducted on both dough and gluten. A number of variables from the various curves were considered and subjected to a principal component analysis (PCA) to get an overview of relationships between the various variables. The first component represented variability in protein quality, associated with elasticity and tenacity in large deformation (large positive loadings for resistance to extension and initial slope of dough and gluten extension curves recorded by the SMS/Kieffer dough and gluten extensibility rig, and the tenacity and strain hardening index of dough measured by the Dobraszczyk/Roberts dough inflation system), the elastic character of the hydrated gluten proteins (large positive loading for elastic modulus [G′], large negative loadings for tan δ and steady state compliance [J_e⁰]), the presence of high molecular weight glutenin subunits (HMW‐GS) 5+10 vs. 2+12, and a size distribution of glutenin polymers shifted toward the high‐end range. The second principal component was associated with flour protein content. Certain rheological data were influenced by protein content in addition to protein quality (area under dough extension curves and dough inflation curves [W]). The approach made it possible to bridge the gap between fundamental rheological properties, empirical measurements of physical properties, protein composition, and size distribution. The interpretation of this study gave indications of the molecular basis for differences in breadmaking performance.  相似文献