4,139 research outputs found
Complex networks as an emerging property of hierarchical preferential attachment
Real complex systems are not rigidly structured; no clear rules or blueprints
exist for their construction. Yet, amidst their apparent randomness, complex
structural properties universally emerge. We propose that an important class of
complex systems can be modeled as an organization of many embedded levels
(potentially infinite in number), all of them following the same universal
growth principle known as preferential attachment. We give examples of such
hierarchy in real systems, for instance in the pyramid of production entities
of the film industry. More importantly, we show how real complex networks can
be interpreted as a projection of our model, from which their scale
independence, their clustering, their hierarchy, their fractality and their
navigability naturally emerge. Our results suggest that complex networks,
viewed as growing systems, can be quite simple, and that the apparent
complexity of their structure is largely a reflection of their unobserved
hierarchical nature.Comment: 12 pages, 7 figure
Phase transition of the susceptible-infected-susceptible dynamics on time-varying configuration model networks
We present a degree-based theoretical framework to study the
susceptible-infected-susceptible (SIS) dynamics on time-varying (rewired)
configuration model networks. Using this framework, we provide a detailed
analysis of the stationary state that covers, for a given structure, every
dynamic regimes easily tuned by the rewiring rate. This analysis is suitable
for the characterization of the phase transition and leads to three main
contributions. (i) We obtain a self-consistent expression for the
absorbing-state threshold, able to capture both collective and hub activation.
(ii) We recover the predictions of a number of existing approaches as limiting
cases of our analysis, providing thereby a unifying point of view for the SIS
dynamics on random networks. (iii) We reinterpret the concept of hub-dominated
phase transition. Within our framework, it appears as a heterogeneous critical
phenomenon : observables for different degree classes have a different scaling
with the infection rate. This leads to the successive activation of the degree
classes beyond the epidemic threshold.Comment: 14 pages, 11 figure
Bench to bedside: A role for erythropoietin in sepsis
Sepsis is the systemic inflammatory response to infection and can result in multiple organ dysfunction syndrome with associated high mortality, morbidity and health costs. Erythropoietin is a well-established treatment for the anaemia of renal failure due to its anti-apoptotic effects on red blood cells and their precursors. The extra-haemopoietic actions of erythropoietin include vasopressor, anti-apoptotic, cytoprotective and immunomodulating actions, all of which could prove beneficial in sepsis. Attenuation of organ dysfunction has been shown in several animal models and its vasopressor effects have been well characterised in laboratory and clinical settings. Clinical trials of erythropoietin in single organ disorders have suggested promising cytoprotective effects, and while no randomised trials have been performed in patients with sepsis, good quality data exist from studies on anaemia in critically ill patients, giving useful information of its pharmacokinetics and potential for harm. An observational cohort study examining the microvascular effects of erythropoietin is underway and the evidence would support further phase II and III clinical trials examining this molecule as an adjunctive treatment in sepsis
Captivate Your Audience by Turning PowerPoint Presentations into Interactive E-Learning Content
Adobe® Captivate software provides educators with a tool to create interactive distance learning modules. This article describes how Adobe® Captivate was used to increase engagement of volunteer learners. An Adobe® Captivate module was created for the University of Idaho Master Gardener program to educate and test new Master Gardener volunteers on the pesticide policy of the University of Idaho. The data collected from the online course demonstrated that it was an effective and time-efficient way to educate volunteers. Hosting the course in a learning management system, such as eXtension.org Moodle campus, also provided the necessary university documentation for volunteer training
Studies of trace elements in sediments
Thesis. (Ph.D.) Massachusetts Institute of Technology. Dept. of Geology and Geophysics, 1954.Vita.Bibliography: leaves 93-98.by Edward Joseph Young.Ph.D
Exact analytical solution of irreversible binary dynamics on networks
In binary cascade dynamics, the nodes of a graph are in one of two possible states (inactive, active), andnodes in the inactive state make an irreversible transition to the active state, as soon as their precursors satisfya predetermined condition. We introduce a set of recursive equations to compute the probability of reachingany final state, given an initial state, and a specification of the transition probability function of each node.Because the naive recursive approach for solving these equations takes factorial time in the number of nodes, wealso introduce an accelerated algorithm, built around a breath-first search procedure. This algorithm solves theequations as efficiently as possible in exponential time
Polarized Broad-Line Emission from Low-Luminosity Active Galactic Nuclei
In order to determine whether unified models of active galactic nuclei apply
to low-luminosity objects, we have undertaken a spectropolarimetric survey of
of LINERs and Seyfert nuclei at the Keck Observatory. The 14 objects observed
have a median H-alpha luminosity of 8x10^{39} erg/s, well below the typical
value of ~10^{41} erg/s for Markarian Seyfert nuclei. Polarized broad H-alpha
emission is detected in three LINERs: NGC 315, NGC 1052, and NGC 4261. Each of
these is an elliptical galaxy with a double-sided radio jet, and the
emission-line polarization in each case is oriented roughly perpendicular to
the jet axis, as expected for the obscuring torus model. NGC 4261 and NGC 315
are known to contain dusty circumnuclear disks, which may be the outer
extensions of the obscuring tori. The detection of polarized broad-line
emission suggests that these objects are nearby, low-luminosity analogs of
obscured quasars residing in narrow-line radio galaxies. The nuclear continuum
of the low-luminosity Seyfert 1 galaxy NGC 4395 is polarized at p = 0.67%,
possibly the result of an electron scattering region near the nucleus.
Continuum polarization is detected in other objects, with a median level of p =
0.36% over 5100-6100 A, but in most cases this is likely to be the result of
transmission through foreground dust. The lack of significant broad-line
polarization in most type 1 LINERs is consistent with the hypothesis that we
view the broad-line regions of these objects directly, rather than in scattered
light.Comment: 28 pages, including 3 tables and 16 figures. Uses the emulateapj
latex style file. Accepted for publication in The Astrophysical Journa
N-(4,6-DimethylÂpyrimidin-2-yl)-4-(oxolan-2-ylamino)benzeneÂsulfonamide
The title compound, C16H20N4O3S, adopts an l-shaped conformation, as seen by the dihedral angle of 76.93 (7)° formed between the two aromatic rings. The most notable feature of the crystal packing is the formation of N—H⋯O and N—H⋯N hydrogen bonds that lead to supraÂmolecular chains orientated along the b axis
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