310 research outputs found
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Dealing with propositional ambiguity in business process improvement
If it is true that people express their views about organisational issues in ambiguous terms then one needs to address this ambiguity instead of the ‘problems’ to find an appropriate methodological approach to resolving or dissolving problem situations in the organisation. This paper highlights and discusses those issues, which therefore relate to ambiguityin relation to decision making tasks within organisations, and the related Soft Systems Methodology / Systems Thinking school of thought, which traditionally constrains such ambiguities. A model of these issues is presented in terms of the Business Process Improvement (BPI) task to highlight these interdependencies
Biosorption of simulated aqueous solution containing acidic dyes by Azolla filliculoides
Biosorption of acidic dyes using the live fern Azolla filliculoides was studied in a discontinuous system. Dye parameters, dye initial concentration and contact time were studied in temperature range of 25-30 ºC and pH=7. It was shown that increasing the 23initial concentration of dye and its contact time resulted in decreasing the dye taking quantity by the absorbent. Also, type of dye has an effective role in the process. The highest dye taking capacity was reported in the concentration of 15 mg/L that was 64.52%, 37.53%, and 32.98% for acidic red 14, blue 25, and yellow 17 dyes respectively. Adsorption isotherm models of Langmuir, Freundlich, Dubinin- Radushkovich, and Temkin were analyzed in different concentrations. Adsorption kinetic data were considered by kinetic models of pseudo-first-order and pseudo-secondorder
Tissue microarrays and their use for preparation of reference slides for educational purposes in histology and histopathology
Use of Tissue array was first applied in 1998, and has received a significant amount of attention from the research community ever since. In this technique, a large number (up to 1000) of cylindrical tissue core extracted from \"donor\" paraffin block are deposited into \"recipient\" block. The aim was modification of the technique of tissue array for manual preparation of the recipient block and production of slides of educational interest in histology and histopathology. The area of interest was localized with the help of stained section, the area was punctured, and the cylindrical core of tissue removed was then introduced into another (recipient) paraffin block. Puncture method was suitable only for parenchymatous organs (liver, kidney, heart, spleen, etc.) but longitudinal sections were required for tubular (gastrointestinal tract, urinary tract, genital tract) and hollow organs (gallbladder, urinary bladder) and brain. The method described is of importance in procurement of materials for preparation of slides for educational purposes and in overcoming the shortage of these materials especially in the field of pathology African Journal of Health Sciences Vol. 13 (3-4) 2006: pp. 66-6
Direct transition to high-dimensional chaos through a global bifurcation
In the present work we report on a genuine route by which a high-dimensional
(with d>4) chaotic attractor is created directly, i.e., without a
low-dimensional chaotic attractor as an intermediate step. The high-dimensional
chaotic set is created in a heteroclinic global bifurcation that yields an
infinite number of unstable tori.The mechanism is illustrated using a system
constructed by coupling three Lorenz oscillators. So, the route presented here
can be considered a prototype for high-dimensional chaotic behavior just as the
Lorenz model is for low-dimensional chaos.Comment: 7 page
Exact equqations and scaling relations for f-avalanche in the Bak-Sneppen evolution model
Infinite hierarchy of exact equations are derived for the newly-observed
f-avalanche in the Bak-Sneppen evolution model. By solving the first order
exact equation, we found that the critical exponent which governs the
divergence of the average avalanche size, is exactly 1 (for all dimensions),
confirmed by the simulations. Solution of the gap equation yields another
universal exponent, denoting the the relaxation to the attractor, is exactly 1.
We also establish some scaling relations among the critical exponents of the
new avalanche.Comment: 5 pages, 1 figur
Transmission of Information in Active Networks
Shannon's Capacity Theorem is the main concept behind the Theory of
Communication. It says that if the amount of information contained in a signal
is smaller than the channel capacity of a physical media of communication, it
can be transmitted with arbitrarily small probability of error. This theorem is
usually applicable to ideal channels of communication in which the information
to be transmitted does not alter the passive characteristics of the channel
that basically tries to reproduce the source of information. For an {\it active
channel}, a network formed by elements that are dynamical systems (such as
neurons, chaotic or periodic oscillators), it is unclear if such theorem is
applicable, once an active channel can adapt to the input of a signal, altering
its capacity. To shed light into this matter, we show, among other results, how
to calculate the information capacity of an active channel of communication.
Then, we show that the {\it channel capacity} depends on whether the active
channel is self-excitable or not and that, contrary to a current belief,
desynchronization can provide an environment in which large amounts of
information can be transmitted in a channel that is self-excitable. An
interesting case of a self-excitable active channel is a network of
electrically connected Hindmarsh-Rose chaotic neurons.Comment: 15 pages, 5 figures. submitted for publication. to appear in Phys.
Rev.
The Computational Complexity of Symbolic Dynamics at the Onset of Chaos
In a variety of studies of dynamical systems, the edge of order and chaos has
been singled out as a region of complexity. It was suggested by Wolfram, on the
basis of qualitative behaviour of cellular automata, that the computational
basis for modelling this region is the Universal Turing Machine. In this paper,
following a suggestion of Crutchfield, we try to show that the Turing machine
model may often be too powerful as a computational model to describe the
boundary of order and chaos. In particular we study the region of the first
accumulation of period doubling in unimodal and bimodal maps of the interval,
from the point of view of language theory. We show that in relation to the
``extended'' Chomsky hierarchy, the relevant computational model in the
unimodal case is the nested stack automaton or the related indexed languages,
while the bimodal case is modeled by the linear bounded automaton or the
related context-sensitive languages.Comment: 1 reference corrected, 1 reference added, minor changes in body of
manuscrip
Estimating the intrinsic dimension of datasets by a minimal neighborhood information
Analyzing large volumes of high-dimensional data is an issue of fundamental importance in data science, molecular simulations and beyond. Several approaches work on the assumption that the important content of a dataset belongs to a manifold whose Intrinsic Dimension (ID) is much lower than the crude large number of coordinates. Such manifold is generally twisted and curved; in addition points on it will be non-uniformly distributed: two factors that make the identification of the ID and its exploitation really hard. Here we propose a new ID estimator using only the distance of the first and the second nearest neighbor of each point in the sample. This extreme minimality enables us to reduce the effects of curvature, of density variation, and the resulting computational cost. The ID estimator is theoretically exact in uniformly distributed datasets, and provides consistent measures in general. When used in combination with block analysis, it allows discriminating the relevant dimensions as a function of the block size. This allows estimating the ID even when the data lie on a manifold perturbed by a high-dimensional noise, a situation often encountered in real world data sets. We demonstrate the usefulness of the approach on molecular simulations and image analysis
Quantifying Self-Organization with Optimal Predictors
Despite broad interest in self-organizing systems, there are few
quantitative, experimentally-applicable criteria for self-organization. The
existing criteria all give counter-intuitive results for important cases. In
this Letter, we propose a new criterion, namely an internally-generated
increase in the statistical complexity, the amount of information required for
optimal prediction of the system's dynamics. We precisely define this
complexity for spatially-extended dynamical systems, using the probabilistic
ideas of mutual information and minimal sufficient statistics. This leads to a
general method for predicting such systems, and a simple algorithm for
estimating statistical complexity. The results of applying this algorithm to a
class of models of excitable media (cyclic cellular automata) strongly support
our proposal.Comment: Four pages, two color figure
Variación espacio-temporal en la dieta del coyote en la costa norte de Jalisco, México
El presente trabajo analiza los cambios a nivel local, en espacio y tiempo, que manifiesta el coyote en su dieta. Se desarrolló en una zona de Bosque Tropical Subcaducifolio de la costa norte de Jalisco, en donde se efectuaron recolectas de excrementos, de marzo del 1999 a abril del 2001, en cuatro sitios con condiciones diferentes. Las muestras fueron analizadas anualmente, estacionalmente (seca y húmeda), para toda el área y por sitios. Resultando que en general el material vegetal (44.20%) y mamÃferos (36.05%) alcanzaron el 80% de la frecuencia relativa de ocurrencia (FRO) de los elementos contenidos en su dieta, observandose cambios significativos entre las estaciones seca y húmeda en ambos grupos. Los elementos con mayor FRO fueron Vitex hemsleyi, Sigmodon mascotensis y Liomys pictus. El material vegetal consumido fue diferente entre sitios, registrándose la más altafrecuencia de consumo en el sitio 1 (47.35%) y la menor en el sitio 3 (22.22%), en cambio el consumo de mamÃferos fue mayor en el sitio 4 (44.83%) y la menor en el sitio 2 (30.77%). Estacionalmente el material vegetal mostró diferencias en los sitios 2 y 4, mamÃferos en los sitios 2 y 4, aves en el sitio 4 e insectos en el sitio 1. Se analizó la diversidad de categorÃas alimenticias consumidas, mediante el Ãndice de Shannon (H'), resultando H'= 2.33 para toda el área de estudio; entre sitios y estaciones se presentaron diferencias en los valores de H'. Se concluye que el carácter oportunista del coyote prevalece aún a nivel local, lo que pone de manifiesto su capacidad de adaptación a la disponibilidad y abundancia de recursos para su dieta.The present work analized the changes at local level in the food habits of coyote. This work was developed in a Tropical Subdeciduos Forest in the North Coast of Jalisco State. We collected scats from March 1999 to April2001, in four sites with different conditions. The scats were analized annually, seasonally (dry-wet), for the whole area and between sites. In general, the vegetal items (44.20%), and mammals (36.05%) reached 80% of relativefrecuency of ocurrence in the diet, observed significant changes between seasons in both groups. The elements with highest relative frequency of occurrence were Vitex hemsleyi, Sigmodon mascotensis and Liomys pictus. The relative frequency of ocurrence of vegetal items were different between sites, with highest values in site 1 (47.35%), and the lowest in site 3 (22.22%); the highest frequencies of mammals were in the site 4(44.83%) and the lowestin the site 2 (30.77%). Seasonally, vegetal items consumption were different in the site 2 and site 4, mammals were different in the site 2 and site 4, birds in the site 4, and insects in the site 1. Diversity of items, mesured with indexof Shannon (H'), value obtained in the diet of coyote H'= 2.33; diversity of items between sites and seasons were different too. We concludes that the opportunistic behavior of the coyote prevails at local level, showing widecapacity of adaptation in order to use the availability and abundance of feeding resources
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