In my master thesis I studied  the dynamics of the sinus node by means of modelling and simulation, in cooperation with the physiologist Björn Wohlfart and my physics tutor Gunnar Ohlén. The sinus node  is the natural pacemaker of the heart and  is placed in the right atrium. It consists of hundreds of thousands individual pacemaker cells, each of which acts as an electric oscillator with its own natural frequency. All of these cells have to be sufficiently coupled in order to synchronize to a common frequency and initiate a regular heartbeat. I carried this subject with me as a started my PhD-studies. After a while, my research became more abstract,  focusing  on general properties of synchronization in large assemblies of limit cycle oscillators with varying natural frequencies. Such synchronization  can be compared to a phase transition, in which  the level of order in a medium suddenly increases as a parameter changes. The most well-known examples are  water that freezes and metal that becomes magnetic as the temperature drops.

Complex wave fronts in a synchronized oscillator lattice


Östborn P.

Simulations of sinus nodal behaviour

Master thesis, April 24, 1998.

Östborn P.

Dynamics of the sinus node during poor intercellular coupling

Licentiate thesis, May 2, 2001.

Östborn P., Wohlfart B., Ohlen G.

Arrhythmia as a result of poor intercellular coupling in the sinus node: a simulation study

Journal of Theoretical Biology 211(3), pp 201-217, 2001

Östborn P., Ohlen G., Wohlfart W.

Simulated sinoatrial exit blocks explained by circle map analysis

Journal of Theoretical Biology 211(3), pp 219-227, 2001

Östborn P.

Functional role of the connective tissue and the gap junction distribution in the sinus node

To be submitted to Journal of Theoretical Biology

Östborn P.

Phase transition to frequency entrainment in a long chain of pulse-coupled oscillators

Physical Review E 66, 016105, July 2002

Östborn P., Åberg S., Ohlen G.

Phase transitions towards frequency entrainment in large oscillator lattices

Physical Review E 68, 015104(R), July 2003

Östborn P.

Phase transitions in large oscillator lattices

PhD thesis, November 21, 2003.

Östborn P.

Frequency entrainment in long chains of oscillators with random natural frequencies in the weak coupling limit

Physical Review E 70, 016120, July 2004

Sträng J. E., Östborn P.

Wave patterns in frequency entrained oscillator lattices

Physical Review E 72, 056137, November 2005

Östborn P.

Renormalization of oscillator lattices with disorder

Physical Review E 79, 051114, May 2009