115 research outputs found
Propagation of external regulation and asynchronous dynamics in random Boolean networks
Boolean Networks and their dynamics are of great interest as abstract
modeling schemes in various disciplines, ranging from biology to computer
science. Whereas parallel update schemes have been studied extensively in past
years, the level of understanding of asynchronous updates schemes is still very
poor. In this paper we study the propagation of external information given by
regulatory input variables into a random Boolean network. We compute both
analytically and numerically the time evolution and the asymptotic behavior of
this propagation of external regulation (PER). In particular, this allows us to
identify variables which are completely determined by this external
information. All those variables in the network which are not directly fixed by
PER form a core which contains in particular all non-trivial feedback loops. We
design a message-passing approach allowing to characterize the statistical
properties of these cores in dependence of the Boolean network and the external
condition. At the end we establish a link between PER dynamics and the full
random asynchronous dynamics of a Boolean network.Comment: 19 pages, 14 figures, to appear in Chao
Message-passing algorithms for optimal utilization of cognitive radio networks
Cognitive Radio has been proposed as a key technology to significantly improve spectrum usage in wireless networks by enabling unlicensed users to access unused resource. We present new algorithms that are needed for the implementation of opportunistic scheduling policies that maximize the throughput utilization of resources by secondary users, under maximum interference constraints imposed by existing primary users. Our approach is based on the Belief Propagation (BP) algorithm, which is advantageous due to its simplicity and potential for distributed implementation. We examine convergence properties and evaluate the performance of the proposed BP algorithms via simulations and demonstrate that the results compare favorably with a benchmark greedy strategy
Network inference using asynchronously updated kinetic Ising Model
Network structures are reconstructed from dynamical data by respectively
naive mean field (nMF) and Thouless-Anderson-Palmer (TAP) approximations. For
TAP approximation, we use two methods to reconstruct the network: a) iteration
method; b) casting the inference formula to a set of cubic equations and
solving it directly. We investigate inference of the asymmetric Sherrington-
Kirkpatrick (S-K) model using asynchronous update. The solutions of the sets
cubic equation depend of temperature T in the S-K model, and a critical
temperature Tc is found around 2.1. For T < Tc, the solutions of the cubic
equation sets are composed of 1 real root and two conjugate complex roots while
for T > Tc there are three real roots. The iteration method is convergent only
if the cubic equations have three real solutions. The two methods give same
results when the iteration method is convergent. Compared to nMF, TAP is
somewhat better at low temperatures, but approaches the same performance as
temperature increase. Both methods behave better for longer data length, but
for improvement arises, TAP is well pronounced.Comment: 6 pages, 4 figure
Ocular Manifestations of the Sturge–Weber Syndrome
Sturge–Weber syndrome (SWS) or encephalotrigeminal angiomatosis is a non-inherited congenital disorder characterized by neurologic, skin, and ocular abnormalities. A somatic activating mutation (R183Q) in the GNAQ gene during early embryogenesis has been recently recognized as the etiology of vascular abnormalities in SWS. Approximately, half of the patients with SWS manifest ocular involvement including glaucoma as the most common ocular abnormality followed by choroidal hemangioma (CH). The underlying pathophysiology of glaucoma in SWS has not been completely understood yet. Early onset glaucoma comprising 60% of SWS glaucoma have lower success rates after medical and surgical treatments compared with primary congenital glaucoma. Primary angle surgery is associated with modest success in the early onset SWS glaucoma while the success rate significantly decreases in late onset glaucoma. Filtration surgery is associated with a higher risk of intraoperative and postoperative choroidal effusion and suprachoroidal hemorrhage. CH is reported in 40–50% of SWS patients. The goal of treatment in patients with CH is to induce involution of the hemangioma, with reduction of subretinal and intraretinal fluid and minimal damage to the neurosensory retina. The decision for treating diffuse CHs highly depends on the patient’s visual acuity, the need for glaucoma surgery, the presence of subretinal fluid (SRF), its chronicity, and the potential for visual recovery
Dynamic mean-field and cavity methods for diluted Ising systems
We compare dynamic mean-field and dynamic cavity as methods to describe the
stationary states of dilute kinetic Ising models. We compute dynamic mean-field
theory by expanding in interaction strength to third order, and compare to the
exact dynamic mean-field theory for fully asymmetric networks. We show that in
diluted networks the dynamic cavity method generally predicts magnetizations of
individual spins better than both first order ("naive") and second order
("TAP") dynamic mean field theory
Numerical Study of Scouring pattern around Bridge pier in 180-degree bend Divergent and Convergent Using SSIIM software
Bridges are the most important river structures that are destroyed due to erosion. The change in the shape of the river geometry along the course of the river leads to erosion of the river bed and can also affect scour around the pier. Therefore, in this paper, the effect of the convergence and divergence ratio of 15% in the 180º bend was investigated on the amount of scour around the pier of the circular bridge using the SSIIM numerical model. The results showed that the SSIIM software has a high ability and accuracy in determining the scour pattern in bend channels. The most scour depth appeared in the bend with 15% convergence and it increased by 1.75 and 2.33 times compared to the uniform and divergent bend, respectively. Also, the most sedimentation height occurred in the bend with 15% convergence and it increased by 3.25 and 4.33 times compared to the uniform and divergent bend, respectively
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