856 research outputs found
Correlation, Network and Multifractal Analysis of Global Financial Indices
We apply RMT, Network and MF-DFA methods to investigate correlation, network
and multifractal properties of 20 global financial indices. We compare results
before and during the financial crisis of 2008 respectively. We find that the
network method gives more useful information about the formation of clusters as
compared to results obtained from eigenvectors corresponding to second largest
eigenvalue and these sectors are formed on the basis of geographical location
of indices. At threshold 0.6, indices corresponding to Americas, Europe and
Asia/Pacific disconnect and form different clusters before the crisis but
during the crisis, indices corresponding to Americas and Europe are combined
together to form a cluster while the Asia/Pacific indices forms another
cluster. By further increasing the value of threshold to 0.9, European
countries France, Germany and UK constitute the most tightly linked markets. We
study multifractal properties of global financial indices and find that
financial indices corresponding to Americas and Europe almost lie in the same
range of degree of multifractality as compared to other indices. India, South
Korea, Hong Kong are found to be near the degree of multifractality of indices
corresponding to Americas and Europe. A large variation in the degree of
multifractality in Egypt, Indonesia, Malaysia, Taiwan and Singapore may be a
reason that when we increase the threshold in financial network these countries
first start getting disconnected at low threshold from the correlation network
of financial indices. We fit Binomial Multifractal Model (BMFM) to these
financial markets.Comment: 32 pages, 25 figures, 1 tabl
Scalar--flat K\"ahler metrics with conformal Bianchi V symmetry
We provide an affirmative answer to a question posed by Tod \cite{Tod:1995b},
and construct all four-dimensional Kahler metrics with vanishing scalar
curvature which are invariant under the conformal action of Bianchi V group.
The construction is based on the combination of twistor theory and the
isomonodromic problem with two double poles. The resulting metrics are
non-diagonal in the left-invariant basis and are explicitly given in terms of
Bessel functions and their integrals. We also make a connection with the LeBrun
ansatz, and characterise the associated solutions of the SU(\infty) Toda
equation by the existence a non-abelian two-dimensional group of point
symmetries.Comment: Dedicated to Maciej Przanowski on the occasion of his 65th birthday.
Minor corrections. To appear in CQ
Balancing Minimum Spanning and Shortest Path Trees
This paper give a simple linear-time algorithm that, given a weighted
digraph, finds a spanning tree that simultaneously approximates a shortest-path
tree and a minimum spanning tree. The algorithm provides a continuous
trade-off: given the two trees and epsilon > 0, the algorithm returns a
spanning tree in which the distance between any vertex and the root of the
shortest-path tree is at most 1+epsilon times the shortest-path distance, and
yet the total weight of the tree is at most 1+2/epsilon times the weight of a
minimum spanning tree. This is the best tradeoff possible. The paper also
describes a fast parallel implementation.Comment: conference version: ACM-SIAM Symposium on Discrete Algorithms (1993
HP1γ function is required for male germ cell survival and spermatogenesis
<p>Abstract</p> <p>Background</p> <p>HP1 proteins are conserved components of eukaryotic constitutive heterochromatin. In mammals, there are three genes that encode HP1-like proteins, termed HP1α, HP1β and HP1γ, which have a high degree of homology This paper describes for the first time, to our knowledge, the physiological function of HP1γ using a gene-targeted mouse.</p> <p>Results</p> <p>While targeting the <it>Cbx3 </it>gene (encoding the HP1γ protein) with a conditional targeting vector, we generated a hypomorphic allele (<it>Cbx3</it><sup><it>hypo</it></sup>), which resulted in much reduced (barely detectable) levels of HP1γ protein. Homozygotes for the hypomorphic allele (<it>Cbx3</it><sup><it>hypo</it>/<it>hypo</it></sup>) are rare, with only 1% of <it>Cbx3</it><sup><it>hypo</it>/<it>hypo </it></sup>animals reaching adulthood. Adult males exhibit a severe hypogonadism that is associated with a loss of germ cells, with some seminiferous tubules retaining only the supporting Sertoli cells (Sertoli cell-only phenotype). The percentage of seminiferous tubules that are positive for L1 ORF1 protein (ORF1p) in <it>Cbx3</it><sup><it>hypo</it>/<it>hypo </it></sup>testes is greater than that for wild-type testes, indicating that L1 retrotransposon silencing is reversed, leading to ectopic expression of ORF1p in <it>Cbx3</it><sup><it>hypo</it>/<it>hypo </it></sup>germ cells.</p> <p>Conclusions</p> <p>The <it>Cbx3 </it>gene product (the HP1γ protein) has a non-redundant function during spermatogenesis that cannot be compensated for by the other two HP1 isotypes. The <it>Cbx3</it><sup><it>hypo</it>/<it>hypo </it></sup>spermatogenesis defect is similar to that found in <it>Miwi2 </it>and <it>Dnmt3L </it>mutants. The <it>Cbx3 </it>gene-targeted mice generated in this study provide an appropriate model for the study of HP1γ in transposon silencing and parental imprinting.</p
Promoción del uso del web docente en la Universidad de Navarra: estrategia seguida y evaluación
This paper presents the strategy adopted by the University of Navarre in school year 2001-2002 and 2002-2003 to promote the use of websites for academic purposes. Data on the outcome of the project implementation are also provided.
The project implementation had several components. First, we developed an e-content creation tool called Anai that is user-friendly. This allows people with very few computer skills to develop high-quality websites that have versatile features like weblogs, assessment systems, discussion tools, etc. Second, we organized several training sessions on the use of these tools.
Today, the number of professors using websites for academic purposes has increased significantly. At least 60% of the courses offered in the University of Navarre have a website. Nevertheless, among the professors, the level and extent of the use of the web vary considerably. 1) The content of most websites is limited to providing basic information about a course, such as course description, objectives, syllabus, criteria of evaluation, etc. 2) Some websites contain teaching notes, handouts and ideas to support students. The content is presented using a variety of formats such as Microsoft Word, Adobe PDF and Microsoft PowerPoint. 3) Very few courses use tools like forums, weblogs, assessment systems or digital video.
The key elements to ensure the effective implementation of the project include the following: user-friendly tools, institutional support and sustained efforts to train the users
Impact of Unexpected Events, Shocking News and Rumours on Foreign Exchange Market Dynamics
We analyze the dynamical response of the world's financial community to
various types of unexpected events, including the 9/11 terrorist attacks as
they unfolded on a minute-by-minute basis. We find that there are various
'species' of news, characterized by how quickly the news get absorbed, how much
meaning and importance is assigned to it by the community, and what subsequent
actions are then taken. For example, the response to the unfolding events of
9/11 shows a gradual collective understanding of what was happening, rather
than an immediate realization. For news items which are not simple economic
statements, and hence whose implications are not immediately obvious, we
uncover periods of collective discovery during which collective opinions seem
to oscillate in a remarkably synchronized way. In the case of a rumour, our
findings also provide a concrete example of contagion in inter-connected
communities. Practical applications of this work include the possibility of
producing selective newsfeeds for specific communities, based on their likely
impact
An HP1 isoform-specific feedback mechanism regulates Suv39h1 activity under stress conditions.
The presence of H3K9me3 and heterochromatin protein 1 (HP1) are hallmarks of heterochromatin conserved in eukaryotes. The spreading and maintenance of H3K9me3 is effected by the functional interplay between the H3K9me3-specific histone methyltransferase Suv39h1 and HP1. This interplay is complex in mammals because the three HP1 isoforms, HP1α, β, and γ, are thought to play a redundant role in Suv39h1-dependent deposition of H3K9me3 in pericentric heterochromatin (PCH). Here, we demonstrate that despite this redundancy, HP1α and, to a lesser extent, HP1γ have a closer functional link to Suv39h1, compared to HP1β. HP1α and γ preferentially interact in vivo with Suv39h1, regulate its dynamics in heterochromatin, and increase Suv39h1 protein stability through an inhibition of MDM2-dependent Suv39h1-K87 polyubiquitination. The reverse is also observed, where Suv39h1 increases HP1α stability compared HP1β and γ. The interplay between Suv39h1 and HP1 isoforms appears to be relevant under genotoxic stress. Specifically, loss of HP1α and γ isoforms inhibits the upregulation of Suv39h1 and H3K9me3 that is observed under stress conditions. Reciprocally, Suv39h1 deficiency abrogates stress-dependent upregulation of HP1α and γ, and enhances HP1β levels. Our work defines a specific role for HP1 isoforms in regulating Suv39h1 function under stress via a feedback mechanism that likely regulates heterochromatin formation
On the mass segregation of stars and brown dwarfs in Taurus
We use the new minimum spanning tree (MST) method to look for mass
segregation in the Taurus association. The method computes the ratio of MST
lengths of any chosen subset of objects, including the most massive stars and
brown dwarfs, to the MST lengths of random sets of stars and brown dwarfs in
the cluster. This mass segregation ratio (Lambda_MSR) enables a quantitative
measure of the spatial distribution of high-mass and low-mass stars, and brown
dwarfs to be made in Taurus.
We find that the most massive stars in Taurus are inversely mass segregated,
with Lambda_MSR = 0.70 +/- 0.10 (Lambda_MSR = 1 corresponds to no mass
segregation), which differs from the strong mass segregation signatures found
in more dense and massive clusters such as Orion. The brown dwarfs in Taurus
are not mass segregated, although we find evidence that some low-mass stars
are, with an Lambda_MSR = 1.25 +/- 0.15. Finally, we compare our results to
previous measures of the spatial distribution of stars and brown dwarfs in
Taurus, and briefly discuss their implications.Comment: 10 pages, 8 figures, accepted for publication in MNRA
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