908 research outputs found
Partial Preferences for Mediated Bargaining
In this work we generalize standard Decision Theory by assuming that two
outcomes can also be incomparable. Two motivating scenarios show how
incomparability may be helpful to represent those situations where, due to lack
of information, the decision maker would like to maintain different options
alive and defer the final decision. In particular, a new axiomatization is
given which turns out to be a weakening of the classical set of axioms used in
Decision Theory. Preliminary results show how preferences involving complex
distributions are related to judgments on single alternatives.Comment: In Proceedings SR 2014, arXiv:1404.041
Analogy between turbulence and quantum gravity: beyond Kolmogorov's 1941 theory
Simple arguments based on the general properties of quantum fluctuations have
been recently shown to imply that quantum fluctuations of spacetime obey the
same scaling laws of the velocity fluctuations in a homogeneous incompressible
turbulent flow, as described by Kolmogorov 1941 (K41) scaling theory. Less
noted, however, is the fact that this analogy rules out the possibility of a
fractal quantum spacetime, in contradiction with growing evidence in quantum
gravity research. In this Note, we show that the notion of a fractal quantum
spacetime can be restored by extending the analogy between turbulence and
quantum gravity beyond the realm of K41 theory. In particular, it is shown that
compatibility of a fractal quantum-space time with the recent Horava-Lifshitz
scenario for quantum gravity, implies singular quantum wavefunctions. Finally,
we propose an operational procedure, based on Extended Self-Similarity
techniques, to inspect the (multi)-scaling properties of quantum gravitational
fluctuations.Comment: Sliglty modified version of the article about to appear in IJMP
The influence of light attenuation on the biogeomorphology of a marine karst cave: a case study of Puerto Princesa Underground River, Palawan, the Philippines
Karst caves are unique biogeomorphological systems. Cave walls offer habitat for microorganisms which in-turn have a geomorphological role via their involvement in rock weathering, erosion and mineralisation. The attenuation of light with distance into caves is known to affect ecology, but the implications of this for biogeomorphological processes and forms have seldom been examined. Here we describe a semi-quantitative microscopy study comparing the extent, structure, and thickness of biocover and depth of endolithic penetration for samples of rock from the Puerto Princesa Underground River system in Palawan, the Philippines, which is a natural UNESCO World Heritage Site.
Organic growth at the entrance of the cave was abundant (100% occurrence) and complex, dominated by phototrophic organisms (green microalgae, diatoms, cyanobacteria, mosses and lichens). Thickness of this layer was 0.28 ± 0.18 mm with active endolith penetration into the limestone (mean depth = 0.13 ± 0.03 mm). In contrast, phototrophs were rare 50 m into the cave and biofilm cover was significantly thinner (0.01 ± 0.01 mm, p < 0.000) and spatially patchy (33% occurrence). Endolithic penetration here was also shallower (< 0.01 mm, p < 0.000) and non-uniform. Biofilm was found 250 m into the cave, but with a complete absence of phototrophs and no evidence of endolithic bioerosion.
We attribute these findings to light-induced stress gradients, showing that the influence of light on phototroph abundance has knock-on consequences for the development of limestone morphological features. In marine caves this includes notches, which were most well-developed at the sheltered cave entrance of our study site, and for which variability in formation rates between locations is currently poorly understood
Designing and engineering evolutionary robust genetic circuits
<p>Abstract</p> <p>Background</p> <p>One problem with engineered genetic circuits in synthetic microbes is their stability over evolutionary time in the absence of selective pressure. Since design of a selective environment for maintaining function of a circuit will be unique to every circuit, general design principles are needed for engineering evolutionary robust circuits that permit the long-term study or applied use of synthetic circuits.</p> <p>Results</p> <p>We first measured the stability of two BioBrick-assembled genetic circuits propagated in <it>Escherichia coli </it>over multiple generations and the mutations that caused their loss-of-function. The first circuit, T9002, loses function in less than 20 generations and the mutation that repeatedly causes its loss-of-function is a deletion between two homologous transcriptional terminators. To measure the effect between transcriptional terminator homology levels and evolutionary stability, we re-engineered six versions of T9002 with a different transcriptional terminator at the end of the circuit. When there is no homology between terminators, the evolutionary half-life of this circuit is significantly improved over 2-fold and is independent of the expression level. Removing homology between terminators and decreasing expression level 4-fold increases the evolutionary half-life over 17-fold. The second circuit, I7101, loses function in less than 50 generations due to a deletion between repeated operator sequences in the promoter. This circuit was re-engineered with different promoters from a promoter library and using a kanamycin resistance gene (<it>kanR</it>) within the circuit to put a selective pressure on the promoter. The evolutionary stability dynamics and loss-of-function mutations in all these circuits are described. We also found that on average, evolutionary half-life exponentially decreases with increasing expression levels.</p> <p>Conclusions</p> <p>A wide variety of loss-of-function mutations are observed in BioBrick-assembled genetic circuits including point mutations, small insertions and deletions, large deletions, and insertion sequence (IS) element insertions that often occur in the scar sequence between parts. Promoter mutations are selected for more than any other biological part. Genetic circuits can be re-engineered to be more evolutionary robust with a few simple design principles: high expression of genetic circuits comes with the cost of low evolutionary stability, avoid repeated sequences, and the use of inducible promoters increases stability. Inclusion of an antibiotic resistance gene within the circuit does not ensure evolutionary stability.</p
SUSApp: a mobile app for measuring and comparing questionnaire-based usability assessments
Usability questionnaires are one of the most used methods to
measure usability in terms of the user’s subjective satisfaction.
However, most of the usability questionnaires do not provide a
complete environment to store measurements and compare
different usability values of application categories and versions
over the long term, which makes it difficult to study the usability
of a software product or even the usability of different versions of
such products over time, hindering the facility to obtain
comparisons and thresholds in usability measurements for
different product lines. In this paper we present SUSApp, a tool
conceived for the analysis of usability through the SUS (System
Usability Scale) questionnaire, which is one of the most popular
ones. This tool was conceived for mobile platforms, and it is
intended to easily analyze usability by storing and recovering past
evaluations, and allowing to statistically compare usability
measurements among different software products and applications
categories. In addition, a user testing is presented. This has
provided acceptable usability results concerning SUSApp in an
experiment with real usersThis work has been partially supported by the funding projects
«eMadrid-CM», granted by the Madrid Research Council (project
code S2013/ICE-2715), and «Flexor» granted by the Spanish
Government (project code TIN2014-52129-R
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