The effects of metabolic inhibition on insulin release and the cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) were studied in individually perifused pancreatic islets from ob/ob mice. The modest basal secretion in the presence of 3 mmol/l glucose was pulsatile with a frequency of approximately 0.2/min, although [Ca(2+)](i) was stable at approximately 100 nmol/l. Introduction of 11 mmol/l glucos...

Bergsten, Peter. Glucose-induced pulsatile insulin release from single islets at stable and oscillatory cytoplasmic Ca21. Am. J. Physiol. 274 (Endocrinol. Metab. 37): E796– E800, 1998.—The cytoplasmic Ca21 concentration ([Ca]i) and insulin release were measured simultaneously in mouse pancreatic islets cultured overnight. [Ca]i was 105 nM and insulin release 3 pmol ·g21 ·s21 at 3 mM glucose. An...

Internet Service Providers have at their disposal a powerful policy-based protocol for enforcing a fine grained control of Interdomain Routing: the Border Gateway Protocol. However, the price to pay for the flexibility of BGP is the lack of convergence guarantees. In this paper, we study the stability of BGP configurations. Namely, we tackle the problem of deciding if, given the policy configur...

Synchronization of coupled, self-excited oscillators in complex systems is a common occurance. This report examines the effects of thermal coupling through the walls of a building on temperature oscillations due to hysteretic thermostatic control. The specific case of three rooms is studied. A system of differential equations models the dynamics of each room temperature, accounting for on-off h...

The purpose of this study is to model and analyze by simulation the dynamics of endogenously created oscillations in real estate (housing) prices. A system dynamics simulation model is built to understand some of the structural sources of cycles in the key housing market variables, from the perspective of construction companies. The model focuses on the economic balance dynamics between supply ...

Understanding synchronous and traveling-wave oscillations, particularly as they relate to transitions between different types of behavior, is a central problem in modeling biological systems. Here, we address this problem in the context of central pattern generators (CPGs). We use contraction theory to establish the global stability of a traveling-wave or synchronous oscillation, determined by ...

Transmission power control is essential in WCDMA in order to optimize the bandwidth utilization which is critical when variable data rates are used. One remaining problem is oscillations in the output powers due to round-trip delays in the power control loops together with the power up-down command device. The oscillations are naturally quantified using discrete-time describing functions, which...

We study the dynamics and bifurcations of a semiconductor laser with delayed filtered feedback, where a part of the output of the laser re-enters after spectral filtering. This type of coherent optical feedback is more challenging than the case of conventional optical feedabck from a simple mirror, but it provides additional control over the output of the semiconductor laser by means of choosin...

We consider solutions to the second-harmonic generation equations in twoand three-dimensional dispersive media in the form of solitons localized in space and time. As is known, collapse does not take place in these models, which is why the solitons may be stable. The general solution is obtained in an approximate analytical form by means of a variational approach, which also allows the stabilit...

Stable and robust oscillations in the concentration of adenosine 3', 5'-cyclic monophosphate (cAMP) are observed during the aggregation phase of starvation-induced development in Dictyostelium discoideum. In this paper we use mathematical modelling together with ideas from robust control theory to identify two factors which appear to make crucial contributions to ensuring the robustness of thes...