2,461 research outputs found
Congestion-gradient driven transport on complex networks
We present a study of transport on complex networks with routing based on
local information. Particles hop from one node of the network to another
according to a set of routing rules with different degrees of congestion
awareness, ranging from random diffusion to rigid congestion-gradient driven
flow. Each node can be either source or destination for particles and all nodes
have the same routing capacity, which are features of ad-hoc wireless networks.
It is shown that the transport capacity increases when a small amount of
congestion awareness is present in the routing rules, and that it then
decreases as the routing rules become too rigid when the flow becomes strictly
congestion-gradient driven. Therefore, an optimum value of the congestion
awareness exists in the routing rules. It is also shown that, in the limit of a
large number of nodes, networks using routing based on local information jam at
any nonzero load. Finally, we study the correlation between congestion at node
level and a betweenness centrality measure.Comment: 11 pages, 8 figure
Essential Tools of Linear Algebra for Calculating Nuclear Spin Dynamics of Chemically Exchanging Systems
In this work, we describe essential tools of linear algebra necessary for
calculating the effect of chemical exchange on spin dynamics and polarization
transfer in various nuclear magnetic resonance (NMR) experiments. We show how
to construct Hamiltonian, relaxation, and chemical exchange superoperators in
the Liouville space, as well as demonstrate corresponding code in Python.
Examples of applying the code are given for problems involving chemical
exchange between NH3 and NH4+ at zero and high magnetic field and polarization
transfer from parahydrogen relevant in SABRE (signal amplification by
reversible exchange) at low magnetic field (0-20 mT). The presented methodology
finds utility for describing the effect of chemical exchange on NMR spectra and
can be extended further by taking into account non-linearities in the master
equation
Optimal routing on complex networks
We present a novel heuristic algorithm for routing optimization on complex
networks. Previously proposed routing optimization algorithms aim at avoiding
or reducing link overload. Our algorithm balances traffic on a network by
minimizing the maximum node betweenness with as little path lengthening as
possible, thus being useful in cases when networks are jamming due to queuing
overload. By using the resulting routing table, a network can sustain
significantly higher traffic without jamming than in the case of traditional
shortest path routing.Comment: 4 pages, 5 figure
Is type 2 diabetes really resolved after laparoscopic sleeve gastrectomy? Glucose variability studied by continuous glucose monitoring
The study was carried out on type 2 diabetic obese patients who underwent laparoscopic sleeve gastrectomy (LSG). Patients underwent regular glycemic controls throughout 3 years and all patients were defined cured from diabetes according to conventional criteria defined as normalization of fasting glucose levels and glycated hemoglobin in absence of antidiabetic therapy. After 3 years of follow-up, Continuous Glucose Monitoring (CGM) was performed in each patient to better clarify the remission of diabetes. In this study, we found that the diabetes resolution after LSG occurred in 40% of patients; in the other 60%, even if they showed a normal fasting glycemia and A1c, patients spent a lot of time in hyperglycemia. During the oral glucose tolerance test (OGTT), we found that 2 h postload glucose determinations revealed overt diabetes only in a small group of patients and might be insufficient to exclude the diagnosis of diabetes in the other patients who spent a lot of time in hyperglycemia, even if they showed a normal glycemia (<140 mg/dL) at 120 minutes OGTT. These interesting data could help clinicians to better individualize patients in which diabetes is not resolved and who could need more attention in order to prevent chronic complications of diabetes
The spectrum of states of Ba~nados-Teitelboim-Zanelli black hole formed by a collapsing dust shell
We perform canonical analysis of an action in which 2+1-dimensional gravity
with negative cosmological constant is coupled to cylindrically symmetric dust
shell. The resulting phase space is finite dimensional having geometry of SO(2;
2) group manifold. Representing the Poisson brackets by commutators results in
the algebra of observables which is a quantum double D(SL(2)q). Deformation
parameter q is real when the total energy of the system is below the threshold
of a black hole formation, and a root of unity when it is above. Inside the
black hole the spectra of the shell radius and time operator are discrete and
take on a finite set of values. The Hilbert space of the black hole is thus
finite-dimensional.Comment: 8 page
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