360 research outputs found
Physarum boats: If plasmodium sailed it would never leave a port
Plasmodium of \emph{Physarum polycephalum} is a single huge (visible by naked
eye) cell with myriad of nuclei. The plasmodium is a promising substrate for
non-classical, nature-inspired, computing devices. It is capable for
approximation of shortest path, computation of planar proximity graphs and
plane tessellations, primitive memory and decision-making. The unique
properties of the plasmodium make it an ideal candidate for a role of amorphous
biological robots with massive parallel information processing and distributed
inputs and outputs. We show that when adhered to light-weight object resting on
a water surface the plasmodium can propel the object by oscillating its
protoplasmic pseudopodia. In experimental laboratory conditions and
computational experiments we study phenomenology of the plasmodium-floater
system, and possible mechanisms of controlling motion of objects propelled by
on board plasmodium
Pattern formation of reaction-diffusion system having self-determined flow in the amoeboid organism of Physarum plasmodium
The amoeboid organism, the plasmodium of Physarum polycephalum, behaves on
the basis of spatio-temporal pattern formation by local
contraction-oscillators. This biological system can be regarded as a
reaction-diffusion system which has spatial interaction by active flow of
protoplasmic sol in the cell. Paying attention to the physiological evidence
that the flow is determined by contraction pattern in the plasmodium, a
reaction-diffusion system having self-determined flow arises. Such a coupling
of reaction-diffusion-advection is a characteristic of the biological system,
and is expected to relate with control mechanism of amoeboid behaviours. Hence,
we have studied effects of the self-determined flow on pattern formation of
simple reaction-diffusion systems. By weakly nonlinear analysis near a trivial
solution, the envelope dynamics follows the complex Ginzburg-Landau type
equation just after bifurcation occurs at finite wave number. The flow term
affects the nonlinear term of the equation through the critical wave number
squared. Contrary to this, wave number isn't explicitly effective with lack of
flow or constant flow. Thus, spatial size of pattern is especially important
for regulating pattern formation in the plasmodium. On the other hand, the flow
term is negligible in the vicinity of bifurcation at infinitely small wave
number, and therefore the pattern formation by simple reaction-diffusion will
also hold. A physiological role of pattern formation as above is discussed.Comment: REVTeX, one column, 7 pages, no figur
High incidence of silent myocardial ischemia in elderly patients with non insulin-dependent diabetes mellitus
Celem badania była ocena częstości występowania
niemego niedokrwienia mięśnia sercowego u bezobjawowych
chorych na cukrzycę w podeszłym wieku
(> 60 lat). Wstępnym etapem badania była maksymalna
próba wysiłkowa na bieżni ruchomej. Spośród
140 chorych u 54 (38,6%) nie udało się osiągnąć
diagnostycznego poziomu wysiłku podczas
próby lub nie można jej było wykonać z innych przyczyn,
u 39 z 86 chorych (45,3%) uzyskano pozytywny
wynik próby wysiłkowej. W drugim etapie tej pracy
u 93 chorych z dodatnią próbą wysiłkową, ale
u których nie można było uzyskać maksymalnego
wysiłku, wykonano scyntygrafię z użyciem talu w
teście z dipirydamolem. U 39 z 93 chorych (41,9%),
u których wystąpiły zaburzenia perfuzji, rozpoznano
nieme niedokrwienie mięśnia sercowego. U 18
chorych z niemym niedokrwieniem mięśnia sercowego,
którzy wyrazili zgodę, wykonano koronarografię.
U 17 spośród 18 chorych (94,4%) stwierdzono
znacznego stopnia zwężenia naczyń wieńcowych,
co potwierdziło duże znaczenie predykcyjne tej metody.
Podsumowując, stwierdzono, że częstość niemego niemego
niedokrwienia mięśnia sercowego u chorych
na cukrzycę typu 2 w podeszłym wieku jest bardzo
wysoka (26,3%). Te wyniki sugerują, że wczesna
intensywna diagnostyka zmian w naczyniach wieńcowych
może się okazać niezbędna jako uzupełnienie
rutynowego postępowania w tej grupie chorych.The present study was designed reveal the incidence
of silent myocardial ischemia in asymptomatic
elderly non-insulin-dependent diabetic (NIDDM) patients
(aged over 60 years). As a first step screening,
maximal treadmill exercise test was performed. Of
140 patients studied, 54 (38.6%) were unable or not
expected to achieve diagnostic levels of exercise
during treadmill testing. A positive exercise test was
noted in 39 of 86 (45.3%) subjects. As a second step
examination, dipyridamole thallium scintigraphy
was performed for 93 subjects who exhibited a positive
exercise test and could not perform a maximal
exercise test. Abnormal perfusion pattern was
found in 39 of 93 (41.9%), who were finally considered to have a silent myocardial ischemia. Coronary
angiography was performed in 18 subjects with
diagnosis of silent myocardial ischemia, who gave
their consent. Significant coronary artery stenosis
was in fact found in 17 of 18 (94.4%) subjects studied,
confirming a very high positive predictive value
of this diagnostic procedure. In conclusion, elderly
NIDDM patients (aged over 60 years) had an
extremely high prevalence (estimated 26.3%) of silent
myocardial ischemia. This evidence suggests that
early and intensive detection may be needed as
a part of routine care for this grou
A biologically inspired network design model
A network design problem is to select a subset of links in a transport network that satisfy passengers or cargo transportation demands while minimizing the overall costs of the transportation. We propose a mathematical model of the foraging behaviour of slime mould P. polycephalum to solve the network design problem and construct optimal transport networks. In our algorithm, a traffic flow between any two cities is estimated using a gravity model. The flow is imitated by the model of the slime mould. The algorithm model converges to a steady state, which represents a solution of the problem. We validate our approach on examples of major transport networks in Mexico and China. By comparing networks developed in our approach with the man-made highways, networks developed by the slime mould, and a cellular automata model inspired by slime mould, we demonstrate the flexibility and efficiency of our approach
Direct measurements of the effects of salt and surfactant on interaction forces between colloidal particles at water-oil interfaces
The forces between colloidal particles at a decane-water interface, in the
presence of low concentrations of a monovalent salt (NaCl) and of the
surfactant sodium dodecylsulfate (SDS) in the aqueous subphase, have been
studied using laser tweezers. In the absence of electrolyte and surfactant,
particle interactions exhibit a long-range repulsion, yet the variation of the
interaction for different particle pairs is found to be considerable. Averaging
over several particle pairs was hence found to be necessary to obtain reliable
assessment of the effects of salt and surfactant. It has previously been
suggested that the repulsion is consistent with electrostatic interactions
between a small number of dissociated charges in the oil phase, leading to a
decay with distance to the power -4 and an absence of any effect of electrolyte
concentration. However, the present work demonstrates that increasing the
electrolyte concentration does yield, on average, a reduction of the magnitude
of the interaction force with electrolyte concentration. This implies that
charges on the water side also contribute significantly to the electrostatic
interactions. An increase in the concentration of SDS leads to a similar
decrease of the interaction force. Moreover the repulsion at fixed SDS
concentrations decreases over longer times. Finally, measurements of three-body
interactions provide insight into the anisotropic nature of the interactions.
The unique time-dependent and anisotropic interactions between particles at the
oil-water interface allow tailoring of the aggregation kinetics and structure
of the suspension structure.Comment: Submitted to Langmui
Emergence of self-organized amoeboid movement in a multi-agent approximation of Physarum polycephalum
The giant single-celled slime mould Physarum polycephalum exhibits complex morphological adaptation and amoeboid movement as it forages for food and may be seen as a minimal example of complex robotic behaviour. Swarm computation has previously been used to explore how spatio-temporal complexity can emerge from, and be distributed within, simple component parts and their interactions. Using a particle-based swarm approach we explore the question of how to generate collective amoeboid movement from simple non-oscillatory component parts in a model of P. polycephalum. The model collective behaves as a cohesive and deformable virtual material, approximating the local coupling within the plasmodium matrix. The collective generates de-novo and complex oscillatory patterns from simple local interactions. The origin of this motor behaviour distributed within the collective rendering is morphologically adaptive, amenable to external influence and robust to simulated environmental insult. We show how to gain external influence over the collective movement by simulated chemo-attraction (pulling towards nutrient stimuli) and simulated light irradiation hazards (pushing from stimuli). The amorphous and distributed properties of the collective are demonstrated by cleaving it into two independent entities and fusing two separate entities to form a single device, thus enabling it to traverse narrow, separate or tortuous paths. We conclude by summarizing the contribution of the model to swarm-based robotics and soft-bodied modular robotics and discuss the future potential of such material approaches to the field. © 2012 IOP Publishing Ltd
Cellular Automata Applications in Shortest Path Problem
Cellular Automata (CAs) are computational models that can capture the
essential features of systems in which global behavior emerges from the
collective effect of simple components, which interact locally. During the last
decades, CAs have been extensively used for mimicking several natural processes
and systems to find fine solutions in many complex hard to solve computer
science and engineering problems. Among them, the shortest path problem is one
of the most pronounced and highly studied problems that scientists have been
trying to tackle by using a plethora of methodologies and even unconventional
approaches. The proposed solutions are mainly justified by their ability to
provide a correct solution in a better time complexity than the renowned
Dijkstra's algorithm. Although there is a wide variety regarding the
algorithmic complexity of the algorithms suggested, spanning from simplistic
graph traversal algorithms to complex nature inspired and bio-mimicking
algorithms, in this chapter we focus on the successful application of CAs to
shortest path problem as found in various diverse disciplines like computer
science, swarm robotics, computer networks, decision science and biomimicking
of biological organisms' behaviour. In particular, an introduction on the first
CA-based algorithm tackling the shortest path problem is provided in detail.
After the short presentation of shortest path algorithms arriving from the
relaxization of the CAs principles, the application of the CA-based shortest
path definition on the coordinated motion of swarm robotics is also introduced.
Moreover, the CA based application of shortest path finding in computer
networks is presented in brief. Finally, a CA that models exactly the behavior
of a biological organism, namely the Physarum's behavior, finding the
minimum-length path between two points in a labyrinth is given.Comment: To appear in the book: Adamatzky, A (Ed.) Shortest path solvers. From
software to wetware. Springer, 201
More resistant tendons obtained from the association of Heteropterys aphrodisiaca and endurance training
<p>Abstract</p> <p>Background</p> <p>Popular Brazilian medicine uses <it>Heteropterys aphrodisiaca </it>infusion as a tonic or stimulant, for the treatment of nervous debility and breakdown and for muscle and bone weakness. This study investigated the effects of <it>Heteropterys aphrodisiaca </it>infusion on the tendon properties and extracellular matrix of rats under endurance training.</p> <p>Methods</p> <p>Wistar rats were grouped as follows: CS- control sedentary, HS- <it>H. aphrodisiaca </it>sedentary, CT-control trained, HT- <it>H. aphrodisiaca </it>trained. The training protocol consisted in running on a motorized treadmill, five times a week, with weekly increase in treadmill speed and duration. Control groups received water while the HS and HT groups received <it>H. aphrodisiaca </it>infusion, daily, by gavage for the 8 weeks of training. Achilles tendons were frozen for biochemical and biomechanical analysis or preserved in Karnovsky's fixative, then processed for histomorphological analysis with light microscopy.</p> <p>Results</p> <p>Biomechanical analysis showed significant increase in maximum load, maximum stress, modulus of elasticity and stiffness of the HT animals' tendons. The metalloproteinase-2 activity was reduced in the HT group. The compression region of HT animals' tendons had a stronger and more intense metachromasy, which suggests an increase in glycosaminoglycan concentration in this region of the tendon. The most intense birefringence was observed in both compression and tension regions of HT animals' tendons, which may indicate a higher organizational level of collagen bundles. The hydroxyproline content increased in the HT group.</p> <p>Conclusions</p> <p>The association of endurance training with <it>H. aphrodisiaca </it>resulted in more organized collagen bundles and more resistant tendons to support higher loads from intense muscle contraction. Despite the clear anabolic effects of <it>Heteropterys aphrodisiaca </it>and the endurance exercise association, no side effects were observed, such as those found for synthetic anabolic androgenic steroids.</p
A physarum-inspired approach to supply chain network design
A supply chain is a system which moves products from a supplier to customers, which plays a very important role in all economic activities. This paper proposes a novel algorithm for a supply chain network design inspired by biological principles of nutrients’ distribution in protoplasmic networks of slime mould Physarum polycephalum. The algorithm handles supply networks where capacity investments and product flows are decision variables, and the networks are required to satisfy product demands. Two features of the slime mould are adopted in our algorithm. The first is the continuity of flux during the iterative process, which is used in real-time updating of the costs associated with the supply links. The second feature is adaptivity. The supply chain can converge to an equilibrium state when costs are changed. Numerical examples are provided to illustrate the practicality and flexibility of the proposed method algorithm
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