6,243 research outputs found
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Real time imaging of two-dimensional iron oxide spherulite nanostructure formation
The formation of complex hierarchical nanostructures has attracted a lot of attention from both the fundamental science and potential applications point of view. Spherulite structures with radial fibrillar branches have been found in various solids; however, their growth mechanisms remain poorly understood. Here, we report real time imaging of the formation of two-dimensional (2D) iron oxide spherulite nanostructures in a liquid cell using transmission electron microscopy (TEM). By tracking the growth trajectories, we show the characteristics of the reaction front and growth kinetics. Our observations reveal that the tip of a growing branch splits as the width exceeds certain sizes (5.5–8.5 nm). The radius of a spherulite nanostructure increases linearly with time at the early stage, transitioning to nonlinear growth at the later stage. Furthermore, a thin layer of solid is accumulated at the tip and nanoparticles from secondary nucleation also appear at the growing front which later develop into fibrillar branches. The spherulite nanostructure is polycrystalline with the co-existence of ferrihydrite and Fe3O4 through-out the growth. A growth model is further established, which provides rational explanations on the linear growth at the early stage and the nonlinearity at the later stage of growth. [Figure not available: see fulltext.]
A Novel Cytoplasmic Protein with RNA-binding Motifs Is an Autoantigen in Human Hepatocellular Carcinoma
In hepatocellular carcinoma (HCC), autoantibodies to intracellular antigens are detected in 30–40% of patients. Patients with chronic hepatitis or liver cirrhosis develop HCC, and when this occurs, some patients exhibit autoantibodies of new specificities. It has been suggested that these novel autoantibody responses may be immune system reactions to proteins involved in transformation-associated cellular events. One HCC serum shown to contain antibodies to unidentified cellular antigens was used to immunoscreen a cDNA expression library, and a full length cDNA clone was isolated with an open reading frame encoding 556 amino acids with a predicted molecular mass of 62 kD. The 62-kD protein contained two types of RNA-binding motifs, the consensus sequence RNA–binding domain (CS-RBD) and four hnRNP K homology (KH) domains. This protein, provisionally called p62, has close identity (66–70%) to three other proteins at the amino acid sequence level, and all four proteins may belong to a family having CS-RBD in the NH2-terminal region and four KH domains in the mid-to-COOH– terminal region. The homologous proteins are: KH domain–containing protein overexpressed in cancer (Koc); zipcode binding protein, a protein which binds to a conserved nucleotide element in chicken β-actin mRNA (ZBP1); and a protein which binds to a promoter cis element in Xenopus laevis TFIIIA gene (B3). p62 protein is cytoplasmic in location, and autoantibodies were found in 21% of a cohort of HCC patients. Patients with chronic hepatitis and liver cirrhosis, conditions which are frequent precursors to HCC, were negative for these autoantibodies, suggesting that the immune response might be related to cellular events leading to transformation. However, the possible involvement of p62 autoantigen as a factor in the transformation process remains to be elucidated
Orthogonal Range Reporting and Rectangle Stabbing for Fat Rectangles
In this paper we study two geometric data structure problems in the special
case when input objects or queries are fat rectangles. We show that in this
case a significant improvement compared to the general case can be achieved.
We describe data structures that answer two- and three-dimensional orthogonal
range reporting queries in the case when the query range is a \emph{fat}
rectangle. Our two-dimensional data structure uses words and supports
queries in time, where is the number of points in the
data structure, is the size of the universe and is the number of points
in the query range. Our three-dimensional data structure needs
words of space and answers queries in time. We also consider the rectangle stabbing problem on a set of
three-dimensional fat rectangles. Our data structure uses space and
answers stabbing queries in time.Comment: extended version of a WADS'19 pape
How Combining Terrorism, Muslim, and Refugee Topics Drives Emotional Tone in Online News: A Six-Country Cross-Cultural Sentiment Analysis
This study looks into how the combination of Islam, refugees, and terrorism topics leads to text-internal changes in the emotional tone of news articles and how these vary across countries and media outlets. Using a multilingual human-validated sentiment analysis, we compare fear and pity in more than 560,000 articles from the most important online news sources in six countries (U.S., Australia, Germany, Switzerland, Turkey, and Lebanon). We observe that fear and pity work antagonistically—that is, the more articles in a particular topical category contain fear, the less pity they will feature. The coverage of refugees without mentioning terrorists and Muslims/Islam featured the lowest fear and highest pity levels of all topical categories studied here. However, when refugees were covered in combination with terrorism and/or Islam, fear increased and pity decreased in Christian-majority countries, whereas no such pattern appeared in Muslim-majority countries (Lebanon, Turkey). Variations in emotions are generally driven more by country-level differences than by the political alignment of individual outlets
The quality of reporting of pilot and feasibility cluster randomised trials: a systematic review
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Dynamic Covalent Synthesis of Crystalline Porous Graphitic Frameworks
Porous graphitic framework (PGF) is a two-dimensional (2D) material that has emerging energy applications. An archetype contains stacked 2D layers, the structure of which features a fully annulated aromatic skeleton with embedded heteroatoms and periodic pores. Due to the lack of a rational approach in establishing in-plane order under mild synthetic conditions, the structural integrity of PGF has remained elusive and ultimately limited its material performance. Here, we report the discovery of the unusual dynamic character of the C=N bonds in the aromatic pyrazine ring system under basic aqueous conditions, which enables the successful synthesis of a crystalline porous nitrogenous graphitic framework with remarkable in-plane order, as evidenced by powder X-ray diffraction studies and direct visualization using high-resolution transmission electron microscopy. The crystalline framework displays superior performance as a cathode material for lithium-ion batteries, outperforming the amorphous counterparts in terms of capacity and cycle stability. Insertion of well-defined, evenly spaced nanoscale pores into the two-dimensional (2D) layers of graphene invokes exciting properties due to the modulation of its electronic band gaps and surface functionalities. A bottom-up synthesis approach to such porous graphitic frameworks (PGFs) is appealing but also remains a great challenge. The current methods of building covalent organic frameworks rely on a small collection of thermodynamically reversible reactions. Such reactions are, however, inadequate in generating a fully annulated aromatic skeleton in PGFs. With the discovery of dynamic pyrazine formation, we succeeded in applying this linking chemistry to obtain a crystalline PGF material, which has displayed high electrical conductivity and remarkable performance as a cathode material for lithium-ion batteries. We envision that the demonstrated success will open the door to a wide array of fully annulated 2D porous frameworks, which hold immense potential for clean energy applications. We report the unusual dynamic characteristics of the C=N bonds in the pyrazine ring promoted under basic aqueous conditions, which enables the successful synthesis of two-dimensional porous graphitic frameworks (PGFs) featuring fully annulated aromatic skeletons and periodic pores. The PGF displayed high electrical conductivity and remarkable performance as a cathode material for lithium-ion batteries, far outperforming the amorphous counterparts in terms of capacity and cycle stability
Strong Casimir force reduction through metallic surface nanostructuring
The Casimir force between bodies in vacuum can be understood as arising from
their interaction with an infinite number of fluctuating electromagnetic
quantum vacuum modes, resulting in a complex dependence on the shape and
material of the interacting objects. Becoming dominant at small separations,
the force plays a significant role in nanomechanics and object manipulation at
the nanoscale, leading to a considerable interest in identifying structures
where the Casimir interaction behaves significantly different from the
well-known attractive force between parallel plates. Here we experimentally
demonstrate that by nanostructuring one of the interacting metal surfaces at
scales below the plasma wavelength, an unexpected regime in the Casimir force
can be observed. Replacing a flat surface with a deep metallic lamellar grating
with sub-100 nm features strongly suppresses the Casimir force and for large
inter-surfaces separations reduces it beyond what would be expected by any
existing theoretical prediction.Comment: 11 pages, 8 figure
Algorithms for Stable Matching and Clustering in a Grid
We study a discrete version of a geometric stable marriage problem originally
proposed in a continuous setting by Hoffman, Holroyd, and Peres, in which
points in the plane are stably matched to cluster centers, as prioritized by
their distances, so that each cluster center is apportioned a set of points of
equal area. We show that, for a discretization of the problem to an
grid of pixels with centers, the problem can be solved in time , and we experiment with two slower but more practical algorithms and
a hybrid method that switches from one of these algorithms to the other to gain
greater efficiency than either algorithm alone. We also show how to combine
geometric stable matchings with a -means clustering algorithm, so as to
provide a geometric political-districting algorithm that views distance in
economic terms, and we experiment with weighted versions of stable -means in
order to improve the connectivity of the resulting clusters.Comment: 23 pages, 12 figures. To appear (without the appendices) at the 18th
International Workshop on Combinatorial Image Analysis, June 19-21, 2017,
Plovdiv, Bulgari
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