734 research outputs found
Topological self-similarity on the random binary-tree model
Asymptotic analysis on some statistical properties of the random binary-tree
model is developed. We quantify a hierarchical structure of branching patterns
based on the Horton-Strahler analysis. We introduce a transformation of a
binary tree, and derive a recursive equation about branch orders. As an
application of the analysis, topological self-similarity and its generalization
is proved in an asymptotic sense. Also, some important examples are presented
Unified View of Scaling Laws for River Networks
Scaling laws that describe the structure of river networks are shown to
follow from three simple assumptions. These assumptions are: (1) river networks
are structurally self-similar, (2) single channels are self-affine, and (3)
overland flow into channels occurs over a characteristic distance (drainage
density is uniform). We obtain a complete set of scaling relations connecting
the exponents of these scaling laws and find that only two of these exponents
are independent. We further demonstrate that the two predominant descriptions
of network structure (Tokunaga's law and Horton's laws) are equivalent in the
case of landscapes with uniform drainage density. The results are tested with
data from both real landscapes and a special class of random networks.Comment: 14 pages, 9 figures, 4 tables (converted to Revtex4, PRE ref added
Reciprocity as a foundation of financial economics
This paper argues that the subsistence of the fundamental theorem of contemporary financial mathematics is the ethical concept ‘reciprocity’. The argument is based on identifying an equivalence between the contemporary, and ostensibly ‘value neutral’, Fundamental Theory of Asset Pricing with theories of mathematical probability that emerged in the seventeenth century in the context of the ethical assessment of commercial contracts in a framework of Aristotelian ethics. This observation, the main claim of the paper, is justified on the basis of results from the Ultimatum Game and is analysed within a framework of Pragmatic philosophy. The analysis leads to the explanatory hypothesis that markets are centres of communicative action with reciprocity as a rule of discourse. The purpose of the paper is to reorientate financial economics to emphasise the objectives of cooperation and social cohesion and to this end, we offer specific policy advice
Modification of cell surface properties of Pseudomonas alcaligenes S22 during hydrocarbon biodegradation
Biodegradation of water insoluble hydrocarbons can be significantly increased by the addition of natural surfactants one. Very promising option is the use of saponins. The obtained results indicated that in this system, after 21 days, 92% biodegradation of diesel oil could be achieved using Pseudomonas alcaligenes. No positive effect on the biodegradation process was observed using synthetic surfactant Triton X-100. The kind of carbon source influences the cell surface properties of microorganisms. Modification of the surface cell could be observed by control of the sedimentation profile. This analytical method is a new approach in microbiological analysis
Educational Experiences and Shifts in Group Consciousness: Studying Women
This study takes a multifaceted approach to group consciousness. The authors assessed changes in women’s feminist consciousness due to their exposure to feminism through women’s studies. Feminist consciousness was measured at the beginning and end of a semester during which some research participants were enrolled in an introductory women’s studies course. Women’s studies students were compared with students who were interested, but not enrolled, in women’s studies. As expected, women’s studies students showed an increase on several aspects of feminist consciousness, whereas non-women’s studies students did not. Non-women’s studies students became less sensitive to sexism. It is also noteworthy that, although they became more feminist, women’s studies students did not become more negative toward men.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69064/2/10.1177_0146167299025003010.pd
Alternative approach to the optimality of the threshold strategy for spectrally negative Levy processes
Consider the optimal dividend problem for an insurance company whose
uncontrolled surplus precess evolves as a spectrally negative Levy process. We
assume that dividends are paid to the shareholders according to admissible
strategies whose dividend rate is bounded by a constant. The objective is to
find a dividend policy so as to maximize the expected discounted value of
dividends which are paid to the shareholders until the company is ruined.
Kyprianou, Loeffen and Perez [28] have shown that a refraction strategy (also
called threshold strategy) forms an optimal strategy under the condition that
the Levy measure has a completely monotone density. In this paper, we propose
an alternative approach to this optimal problem.Comment: 16 page
Subglacial lake drainage detected beneath the Greenland ice sheet
The contribution of the Greenland ice sheet to sea-level rise has accelerated in recent decades. Subglacial lake drainage events can induce an ice sheet dynamic response—a process that has been observed in Antarctica, but not yet in Greenland, where the presence of subglacial lakes has only recently been discovered. Here we investigate the water flow paths from a subglacial lake, which drained beneath the Greenland ice sheet in 2011. Our observations suggest that the lake was fed by surface meltwater flowing down a nearby moulin, and that the draining water reached the ice margin via a subglacial tunnel. Interferometric synthetic aperture radar-derived measurements of ice surface motion acquired in 1995 suggest that a similar event may have occurred 16 years earlier, and we propose that, as the climate warms, increasing volumes of surface meltwater routed to the bed will cause such events to become more common in the future
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