19,584 research outputs found
Multi-Step Knowledge-Aided Iterative ESPRIT for Direction Finding
In this work, we propose a subspace-based algorithm for DOA estimation which
iteratively reduces the disturbance factors of the estimated data covariance
matrix and incorporates prior knowledge which is gradually obtained on line. An
analysis of the MSE of the reshaped data covariance matrix is carried out along
with comparisons between computational complexities of the proposed and
existing algorithms. Simulations focusing on closely-spaced sources, where they
are uncorrelated and correlated, illustrate the improvements achieved.Comment: 7 figures. arXiv admin note: text overlap with arXiv:1703.1052
Quantum dynamics of localized excitations in a symmetric trimer molecule
We study the time evolution of localized (local bond) excitations in a
symmetric quantum trimer molecule. We relate the dynamical properties of
localized excitations such as their spectral intensity and their temporal
evolution (survival probability and tunneling of bosons) to their degree of
overlap with quantum tunneling pair states. We report on the existence of
degeneracy points in the trimer eigenvalue spectrum for specific values of
parameters due to avoided crossings between tunneling pair states and
additional states. The tunneling of localized excitations which overlap with
these degenerate states is suppressed on all times. As a result local bond
excitations may be strongly localized forever, similar to their classical
counterparts.Comment: 9 pages, 12 figures. Improved version with more discussions. Some
figures were replaced for better understanding. Accepted in Phys. Rev.
Finite size analysis of a two-dimensional Ising model within a nonextensive approach
In this work we present a thorough analysis of the phase transitions that
occur in a ferromagnetic 2D Ising model, with only nearest-neighbors
interactions, in the framework of the Tsallis nonextensive statistics. We
performed Monte Carlo simulations on square lattices with linear sizes L
ranging from 32 up to 512. The statistical weight of the Metropolis algorithm
was changed according to the nonextensive statistics. Discontinuities in the
m(T) curve are observed for . However, we have verified only one
peak on the energy histograms at the critical temperatures, indicating the
occurrence of continuous phase transitions. For the regime, we
have found continuous phase transitions between the ordered and the disordered
phases, and determined the critical exponents via finite-size scaling. We
verified that the critical exponents , and depend
on the entropic index in the range in the form , and . On the other hand, the critical exponent does not
depend on . This suggests a violation of the scaling relations and and a nonuniversality of the
critical exponents along the ferro-paramagnetic frontier.Comment: accepted for publication in Phys. Rev.
Customer engagement: Growing relevance in marketing research
Within marketing research, the number of studies about customer engagement has been growing, emerging mainly after 2005 (Brodie et al., 2011), which reflects the increasing interest of researchers on the topic. The purpose of this study is to provide a systematic literature review to answer to the research question: “What marketing research has been conducted on customer engagement until now and what could be future avenues for research?”info:eu-repo/semantics/publishedVersio
Authenticity in international marketing field: Systematic literature review
Purpose:This study aims to usea systematic literature review process to get the state of the art on the concept of authenticity in marketing field. The review question defined is: “What marketing research has been conducted on authenticity in international marketing until now and whatcould be future avenues for research?”.info:eu-repo/semantics/publishedVersio
The Friedreich ataxia GAA repeat expansion mutation induces comparable epigenetic changes in human and transgenic mouse brain and heart tissues
Friedreich ataxia (FRDA) is caused by a homozygous GAA repeat expansion mutation
within intron 1 of the FXN gene, leading to reduced expression of frataxin protein.
Evidence suggests that the mutation may induce epigenetic changes and heterochromatin
formation, thereby impeding gene transcription. In particular, studies using FRDA patient
blood and lymphoblastoid cell lines have detected increased DNA methylation of specific
CpG sites upstream of the GAA repeat and histone modifications in regions flanking the
GAA repeat. In this report we show that such epigenetic changes are also present in
FRDA patient brain, cerebellum and heart tissues, the primary affected systems of the
disorder. Bisulfite sequence analysis of the FXN flanking GAA regions reveals a shift in
the FRDA DNA methylation profile, with upstream CpG sites becoming consistently
hypermethylated and downstream CpG sites becoming consistently hypomethylated. We
also identify differential DNA methylation at three specific CpG sites within the FXN
promoter and one CpG site within exon 1. Furthermore, we show by chromatin
immunoprecipitation (ChIP) analysis that there is overall decreased histone H3K9
acetylation together with increased H3K9 methylation of FRDA brain tissue. Further
studies of brain, cerebellum and heart tissues from our GAA repeat expansion-containing
FRDA YAC transgenic mice reveal comparable epigenetic changes to those detected in
FRDA patient tissue. We have thus developed a mouse model that will be a valuable
resource for future therapeutic studies targeting epigenetic modifications of the FXN gene
to increase frataxin expression
Influence of the external pressure on the quantum correlations of molecular magnets
The study of quantum correlations in solid state systems is a large avenue
for research and their detection and manipulation are an actual challenge to
overcome. In this context, we show by using first-principles calculations on
the prototype material KNaCuSiO that the degree of quantum
correlations in this spin cluster system can be managed by external hydrostatic
pressure. Our results open the doors for research in detection and manipulation
of quantum correlations in magnetic systems with promising applications in
quantum information science
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