16,231 research outputs found
Time Evolution of Non-Lethal Infectious Diseases: A Semi-Continuous Approach
A model describing the dynamics related to the spreading of non-lethal
infectious diseases in a fixed-size population is proposed. The model consists
of a non-linear delay-differential equation describing the time evolution of
the increment in the number of infectious individuals and depends upon a
limited number of parameters. Predictions are in good qualitative agreement
with data on influenza.Comment: 21 page
High surface area, emulsion-templated carbon foams by activation of polyHIPEs derived from Pickering emulsions.
Carbon foams displaying hierarchical porosity and excellent surface areas of >1400 m2/g can be produced by the activation of macroporous poly(divinylbenzene). Poly(divinylbenzene) was synthesized from the polymerization of the continuous, but minority, phase of a simple high internal phase Pickering emulsion. By the addition of KOH, chemical activation of the materials is induced during carbonization, producing Pickering-emulsion templated carbon foams, or carboHIPEs, with tailorable macropore diameters and surface areas almost triple that of those previously reported. The retention of the customizable, macroporous open-cell structure of the poly(divinylbenzene) precursor and the production of a large degree of microporosity during activation leads to tailorable carboHIPEs with excellent surface areas
Analytic Kerr black hole lensing for equatorial observers in the strong deflection limit
In this paper we present an analytical treatment of gravitational lensing by
Kerr black holes in the limit of very large deflection angles, restricting to
observers in the equatorial plane. We accomplish our objective starting from
the Schwarzschild black hole and adding corrections up to second order in the
black hole spin. This is sufficient to provide a full description of all
caustics and the inversion of lens mapping for sources near them. On the basis
of these formulae we argue that relativistic images of Low Mass X-ray Binaries
around Sgr A* are very likely to be seen by future X-ray interferometry
missions.Comment: 19 pages, 9 figures, published on Phys. Rev.
Conformations Of A Model Protein Revealed By An Aggregating Cuᴵᴵ Porphyrin: Sensing The Difference
Aggregated t-CuP binds to poly-L-glutamate through supramolecular interactions, revealing itself to be an extremely sensitive probe for the major conformations of the polymeric scaffold
Beyond divide and rule: weak dictators, natural resources and civil conflict
We propose a model where an autocrat rules over an ethnically divided society. The dictator selects the tax rate over domestic production and the nation's natural resources to maximize his rents under the threat of a regime-switching revolution. We show that a weak ruler may let the country plunge in civil war to increase his personal rents. Inter-group fighting weakens potential opposition to the ruler, thereby allowing him to increase fiscal pressure. We show that the presence of natural resources exacerbatesthe incentives of the ruler to promote civil conflict for his own profit, especially if the resources are unequally distributed across ethnic groups. We validate the main predictions of the model using cross-country data over the period 1960-2007, and show that our empirical results are not likely to be driven by omitted observable determinants of civil war incidence or by unobservable country-specific heterogeneity.
Structural Properties of the Disordered Spherical and other Mean Field Spin Models
We extend the approach of Aizenman, Sims and Starr for the SK-type models to
their spherical versions. Such an extension has already been performed for
diluted spin glasses. The factorization property of the optimal structures
found by Guerra for the SK model, which holds for diluted models as well, is
verified also in the case of spherical systems, with the due modifications.
Hence we show that there are some common structural features in various mean
field spin models. These similarities seem to be quite paradigmatic, and we
summarize the various techniques typically used to prove the structural
analogies and to tackle the computation of the free energy per spin in the
thermodynamic limit.Comment: 24 page
A long-period, violently-variable X-ray source in a young SNR
Observations with the Newton X-ray Multimirror Mission (XMM) show a strong
periodic modulation at 6.67+/-0.03 hours of the X-ray source at the centre of
the 2,000-year-old supernova remnant RCW 103. No fast pulsations are visible.
If genetically tied to the supernova remnant, the source could either be an
X-ray binary, comprising a compact object and a low-mass star in an eccentric
orbit, or an isolated neutron star. In the latter case, its age-period
combination would point to a peculiar magnetar, dramatically slowed-down,
possibly by a supernova debris disc. Both scenarios require non-standard
assumptions on the formation and evolution of compact objects in supernova
explosions.Comment: Accepted for publication in Science. Published online via Science
Express on 2006, July 6. 17 pages, 7 figure
Finding a reflexive voice : -- researching the problems of implementing new learning practices within a New Zealand manufacturing organisation : a 100pt thesis presented in partial fulfilment of the requirements for the degree of Master of Management in Human Resources Management at Massey University
This study explored the social forces mediating manager's participation in a new reflexive participative learning practice designed to improve profitability within a New Zealand manufacturing organisation. Despite a large theoretical and managerial body of literature on organisational learning there has been little empirical investigation of how people experience and engage their reflexivity towards challenging the status-quo to create high level learning and new knowledge. Power was identified as a potential moderator of the reflexive learning experience and the variable relations of power and learning were constructed from a review of literature and these relationships were explored and investigated within the case study. Two prevailing discourses were identified as powerful moderators of public reflexivity, the traditionalist discourse which constructed managers actions and conversations towards insularism and survivalist concerns and the productionist discourse in which institutionalised production practices encircled and mediated managers actions and what constituted legitimacy in conversations. This study used a critical action research method to place the reflexive experience of managers and the researcher at the centre of the study and provide data representative of the social discourses that constructed variable freedoms and constraints upon the reflexive voice
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