1,373 research outputs found
Commensurate lattice distortion in the layered titanium oxypnictides NaTiO ( As, Sb) determined by X-ray diffraction
We report single crystal X-ray diffraction measurements on
NaTiO ( = As, Sb) which reveal a charge superstructure that
appears below the density wave transitions previously observed in bulk data.
From symmetry-constrained structure refinements we establish that the
associated distortion mode can be described by two propagation vectors, and , with (Sb) or (As), and primarily involves in-plane displacements of the Ti atoms
perpendicular to the Ti--O bonds. The results provide direct evidence for
phonon-assisted charge density wave order in NaTiO and identify
a proximate ordered phase that could compete with superconductivity in doped
BaTiSbO
Local corrugation and persistent charge density wave in ZrTe3 with Ni intercalation
The mechanism of emergent bulk superconductivity in t ransition-metal intercalated ZrTe3 is investigated by studying the effect of Ni doping on the band structure and charge density wave (CDW). The study reports theoretical and experimental results in the range of Ni0.01ZrTe3 to Ni0.05ZrTe3. In the highest doped samples, bulk superconductivity with Tc < TCDW is observed, with a reduced TCDW compared with pure ZrTe3. Relativistic ab initio calculations reveal that Ni incorporation occurs preferentially through intercalation in the van der Waals gap. Analysis of the structural and electronic effects of intercalation indicate buckling of the Te sheets adjacent to the Ni site akin to a locally stabilized CDW-like lattice distortion. In contrast to the changes of TCDW observed in resistivity, experiments with low-temperature x-ray diffraction, angle-resolved-photoemission spectroscopy, as well as temperature-dependent resistivity reveal the nearly unchanged persistence of the CDW into the regime of bulk superconductivity. The CDW gap is found to be unchanged in its extent in momentum space, with the gap size also unchanged or possibly slightly reduced upon Ni intercalation. Both experimental observations suggest that superconductivity coexists with the CDW in NixZrTe3
A reaction-diffusion model for the growth of avascular tumor
A nutrient-limited model for avascular cancer growth including cell
proliferation, motility and death is presented. The model qualitatively
reproduces commonly observed morphologies for primary tumors, and the simulated
patterns are characterized by its gyration radius, total number of cancer
cells, and number of cells on tumor periphery. These very distinct
morphological patterns follow Gompertz growth curves, but exhibit different
scaling laws for their surfaces. Also, the simulated tumors incorporate a
spatial structure composed of a central necrotic core, an inner rim of
quiescent cells and a narrow outer shell of proliferating cells in agreement
with biological data. Finally, our results indicate that the competition for
nutrients among normal and cancer cells may be a determinant factor in
generating papillary tumor morphology.Comment: 9 pages, 6 figures, to appear in PR
SCI
Persistent homology is a powerful tool in Topological Data Analysis (TDA) to capture the topological properties of data succinctly at different spatial resolutions. For graphical data, the shape, and structure of the neighborhood of individual data items (nodes) are an essential means of characterizing their properties. We propose the use of persistent homology methods to capture structural and topological properties of graphs and use it to address the problem of link prediction. We achieve encouraging results on nine different real-world datasets that attest to the potential of persistent homology-based methods for network analysis
Multidimensional Data Visual Exploration by Interactive Information Segments
Visualization techniques provide an outstanding role in KDD process for data analysis and mining. However, one image does not always convey successfully the inherent information from high dimensionality, very large databases. In this paper we introduce VSIS (Visual Set of Information Segments), an interactive tool to visually explore multidimensional, very large, numerical data. Within the supervised learning, our proposal approaches the problem of classification by searching of meaningful intervals belonging to the most relevant attributes. These intervals are displayed as multiâcolored bars in which the degree of impurity with respect to the class membership can be easily perceived. Such bars can be reâexplored interactively with new values of userâdefined parameters. A case study of applying VSIS to some UCI repository data sets shows the usefulness of our tool in supporting the exploration of multidimensional and very large data
Relationships between CYP2D6 phenotype, breast cancer and hot flushes in women at high risk of breast cancer receiving prophylactic tamoxifen: results from the IBIS-I trial
Licensed under a Creative Commons Attribution Non-Commercial Share Alike Licens
Women and Illegal Activities: Gender Differences and Women's Willingness to Comply Over Time
In recent years the topics of illegal activities such as corruption or tax evasion have attracted a great deal of attention. However, there is still a lack of substantial empirical evidence about the determinants of compliance. The aim of this paper is to investigate empirically whether women are more willing to be compliant than men and whether we observe (among women and in general) differences in attitudes among similar age groups in different time periods (cohort effect) or changing attitudes of the same cohorts over time (age effect) using data from eight Western European countries from the World Values Survey and the European Values Survey that span the period from 1981 to 1999. The results reveal higher willingness to comply among women and an age rather than a cohort effect. Working Paper 06-5
Geographic constraints on social network groups
Social groups are fundamental building blocks of human societies. While our
social interactions have always been constrained by geography, it has been
impossible, due to practical difficulties, to evaluate the nature of this
restriction on social group structure. We construct a social network of
individuals whose most frequent geographical locations are also known. We also
classify the individuals into groups according to a community detection
algorithm. We study the variation of geographical span for social groups of
varying sizes, and explore the relationship between topological positions and
geographic positions of their members. We find that small social groups are
geographically very tight, but become much more clumped when the group size
exceeds about 30 members. Also, we find no correlation between the topological
positions and geographic positions of individuals within network communities.
These results suggest that spreading processes face distinct structural and
spatial constraints.Comment: 10 pages, 5 figure
Natural Compatibilism, Indeterminism, and Intrusive Metaphysics
The claim that common sense regards free will and moral responsibility as compatible with determinism has played a central role in both analytic and experimental philosophy. In this paper, we show that evidence in favor of this ânatural compatibilismâ is undermined by the role that indeterministic metaphysical views play in how people construe deterministic scenarios. To demonstrate this, we re-examine two classic studies that have been used to support natural compatibilism. We find that although people give apparently compatibilist responses, this is largely explained by the fact that people import an indeterministic metaphysics into deterministic scenarios when making judgments about freedom and responsibility. We conclude that judgments based on these scenarios are not reliable evidence for natural compatibilism
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