7,669 research outputs found
Spanning Trees and bootstrap reliability estimation in correlation based networks
We introduce a new technique to associate a spanning tree to the average
linkage cluster analysis. We term this tree as the Average Linkage Minimum
Spanning Tree. We also introduce a technique to associate a value of
reliability to links of correlation based graphs by using bootstrap replicas of
data. Both techniques are applied to the portfolio of the 300 most capitalized
stocks traded at New York Stock Exchange during the time period 2001-2003. We
show that the Average Linkage Minimum Spanning Tree recognizes economic sectors
and sub-sectors as communities in the network slightly better than the Minimum
Spanning Tree does. We also show that the average reliability of links in the
Minimum Spanning Tree is slightly greater than the average reliability of links
in the Average Linkage Minimum Spanning Tree.Comment: 17 pages, 3 figure
Flavour-conserving oscillations of Dirac-Majorana neutrinos
We analyze both chirality-changing and chirality-preserving transitions of
Dirac-Majorana neutrinos. In vacuum, the first ones are suppressed with respect
to the others due to helicity conservation and the interactions with a
(``normal'') medium practically does not affect the expressions of the
probabilities for these transitions, even if the amplitudes of oscillations
slightly change. For usual situations involving relativistic neutrinos we find
no resonant enhancement for all flavour-conserving transitions. However, for
very light neutrinos propagating in superdense media, the pattern of
oscillations is dramatically altered with respect to the
vacuum case, the transition probability practically vanishing. An application
of this result is envisaged.Comment: 14 pages, latex 2E, no figure
Nonprofit Church Leaders’ Perceptions and Lived Experiences Involving Innovation Competency and Change Management: A Phenomenological Study
Innovation competency among religious leaders has been an area of study as nonprofit researchers continue to discover that conventional ways of managing change are no longer effective when tackling present issues. Discussions regarding using innovation competency to manage change among religious leaders are vague, despite benefits to the nonprofit sector. The purpose of this qualitative phenomenological study was to explore the lived experiences of nonprofit church leaders to better understand how innovation competency has shaped organizational change results. Boyatzis’ effective job performance model was the conceptual framework that guided this study. Interview data were gathered from 14 participants who met the inclusion criteria of being a leader with innovation competency experience living in New York, New York. Data from the transcripts were inductively analyzed by using computer software and coded techniques for 10 emergent themes. Results revealed improved organizational performance for church leaders who used innovation competency in managing change, along with spirituality and faith. However, emerging themes showed diverse reasons for innovation competency use and its influences on leaders’ behavioral characteristics. Positive social change can be achieved by promoting innovation competency among religious leaders irrespective of spirituality, belief, and doctrine position regarding change management and organizational performance. Outcomes of this study may also provide useful information for religious leaders regarding implementing new ways and programs to help organizational growth
Community characterization of heterogeneous complex systems
We introduce an analytical statistical method to characterize the communities
detected in heterogeneous complex systems. By posing a suitable null
hypothesis, our method makes use of the hypergeometric distribution to assess
the probability that a given property is over-expressed in the elements of a
community with respect to all the elements of the investigated set. We apply
our method to two specific complex networks, namely a network of world movies
and a network of physics preprints. The characterization of the elements and of
the communities is done in terms of languages and countries for the movie
network and of journals and subject categories for papers. We find that our
method is able to characterize clearly the identified communities. Moreover our
method works well both for large and for small communities.Comment: 8 pages, 1 figure and 2 table
Classical Disordered Ground States: Super-Ideal Gases, and Stealth and Equi-Luminous Materials
Using a collective coordinate numerical optimization procedure, we construct
ground-state configurations of interacting particle systems in various space
dimensions so that the scattering of radiation exactly matches a prescribed
pattern for a set of wave vectors. We show that the constructed ground states
are, counterintuitively, disordered (i.e., possess no long-range order) in the
infinite-volume limit. We focus on three classes of configurations with unique
radiation scattering characteristics: (i)``stealth'' materials, which are
transparent to incident radiation at certain wavelengths; (ii)``super-ideal''
gases, which scatter radiation identically to that of an ensemble of ideal gas
configurations for a selected set of wave vectors; and (iii)``equi-luminous''
materials, which scatter radiation equally intensely for a selected set of wave
vectors. We find that ground-state configurations have an increased tendency to
contain clusters of particles as one increases the prescribed luminosity.
Limitations and consequences of this procedure are detailed.Comment: 44 pages, 16 figures, revtek
A bizarre foreign body in the appendix: A case report
Foreign bodies are rare causes of appendicitis and, in most cases, ingested foreign bodies pass through the alimentary tract asymptomatically. However, ingested foreign bodies may sometimes remain silent within the appendix for many years without an inflammatory response. Despite the fact that cases of foreign-body-induced appendicitis have been documented, sharp and pointed objects are more likely to cause perforations and abscesses, and present more rapidly after ingestion. Various materials, such as needles and drill bits, as well as organic matter, such as seeds, have been implicated as causes of acute appendicitis. Clinical presentation can vary from hours to years. Blunt foreign bodies are more likely to remain dormant for longer periods and cause appendicitis through obstruction of the appendiceal lumen. We herein describe a patient presenting with a foreign body in his appendix which had been swallowed 15 years previously. The contrast between the large size of the foreign body, the long clinical history without symptoms and the total absence of any histological inflammation was notable. We suggest that an elective laparoscopic appendectomy should be offered to such patients as a possible management optio
PANIC DISORDER, ANXIETY, AND CARDIOVASCULAR DISEASES
Different data indicate that psychological and/or emotional disorders may play an important role in the natural
history of heart diseases. Although the major evidence is that related to depression, epidemiological data would indicate
that anxiety and panic disorders are highly represented in cardiac patient, thus influencing mortality and morbidity.
The diagnosis of panic disorder in patients with chest pain is crucial to a correct therapeutic approach, as well as to
reduce the risks and costs of inappropriate treatments.
Anxiety and panic may accelerate different direct and indirect processes involved in the pathogenesis of
cardiovascular diseases: lifestyle risk factors, arterial hypertension, myocardial perfusion, autonomic nervous system or
hypothalamus-pituitary-adrenal axis, platelet activation, and inflammation processes. Panic disorder seems to correlate
particularly with sudden death: this suggests that it may be considered one of the main inducers of life-threatening
arrhythmias, rather than to be linked to the development and progression of coronary atherosclerosis.
Beyond hard outcomes, panic disorders produce negative effects on both global adjustment and life quality that
may impair the course of the cardiac diseases. Interestingly, specific antipanic and anxiolytic agents seem to be
particularly effective upon life quality. In any case, adequate controlled clinical trials are necessary in order to confirm
the possibility of cardiovascular risk reduction by means of anxiety and panic disorder treatment
Levy-Student Distributions for Halos in Accelerator Beams
We describe the transverse beam distribution in particle accelerators within
the controlled, stochastic dynamical scheme of the Stochastic Mechanics (SM)
which produces time reversal invariant diffusion processes. This leads to a
linearized theory summarized in a Shchr\"odinger--like (\Sl) equation. The
space charge effects have been introduced in a recent paper~\cite{prstab} by
coupling this \Sl equation with the Maxwell equations. We analyze the space
charge effects to understand how the dynamics produces the actual beam
distributions, and in particular we show how the stationary, self--consistent
solutions are related to the (external, and space--charge) potentials both when
we suppose that the external field is harmonic (\emph{constant focusing}), and
when we \emph{a priori} prescribe the shape of the stationary solution. We then
proceed to discuss a few new ideas~\cite{epac04} by introducing the generalized
Student distributions, namely non--Gaussian, L\'evy \emph{infinitely divisible}
(but not \emph{stable}) distributions. We will discuss this idea from two
different standpoints: (a) first by supposing that the stationary distribution
of our (Wiener powered) SM model is a Student distribution; (b) by supposing
that our model is based on a (non--Gaussian) L\'evy process whose increments
are Student distributed. We show that in the case (a) the longer tails of the
power decay of the Student laws, and in the case (b) the discontinuities of the
L\'evy--Student process can well account for the rare escape of particles from
the beam core, and hence for the formation of a halo in intense beams.Comment: revtex4, 18 pages, 12 figure
Shear viscosity and chemical equilibration of the QGP
We have investigated, in the frame work of the transport approach, different
aspects of the QGP created in Heavy Ion Collisions at RHIC and LHC energies.
The shear viscosity has been calculated by using the Green-Kubo relation
at the cascade level. We have compared the numerical results for
obtained from the Green-Kubo correlator with the analytical formula in both the
Relaxation Time Approximation (RTA) and the Chapman-Enskog approximation (CE).
From this comparison we show that in the range of temperature explored in a
Heavy Ion collision the RTA underestimates the viscosity by about a factor of
2, while a good agreement is found between the CE approximation and Gree-Kubo
relation already at first order of approximation. The agreement with the CE
approximation supplies an analytical formula that allows to develop kinetic
transport theory at fixed shear viscosity to entropy density ratio, .
We show some results for the build up of anisotropic flows in a
transport approach at fixed shear viscosity to entropy density ratio, .
We study the impact of a T-dependent on the generation of the
elliptic flows at both RHIC and LHC. We show that the transport approach
provides, in a unified way, a tool able to naturally describe the
in a wide range of , including also the description of
the rise and fall and saturation of the observed at LHC.
Finally, we have studied the evolution of the quark-gluon composition employing
a Boltzmann-Vlasov transport approach that include: the mean fields dynamics,
associated to the quasi-particle model, and the elastic and inelastic
collisions for massive quarks and gluons. Following the chemical evolution from
an initial gluon dominated plasma we predict a quark dominance close to
paving the way to an hadronization via quark coalescence.Comment: 15 pages, 10 figures, Invited Talk given by S. Plumari at the 11th
International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio,
Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in
Journal of Physics: Conference Series (JPCS
Automated Analysis of MUTEX Algorithms with FASE
In this paper we study the liveness of several MUTEX solutions by
representing them as processes in PAFAS s, a CCS-like process algebra with a
specific operator for modelling non-blocking reading behaviours. Verification
is carried out using the tool FASE, exploiting a correspondence between
violations of the liveness property and a special kind of cycles (called
catastrophic cycles) in some transition system. We also compare our approach
with others in the literature. The aim of this paper is twofold: on the one
hand, we want to demonstrate the applicability of FASE to some concrete,
meaningful examples; on the other hand, we want to study the impact of
introducing non-blocking behaviours in modelling concurrent systems.Comment: In Proceedings GandALF 2011, arXiv:1106.081
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