Programming the emergence in morphogenetically architected complex systems.

Large sets of elements interacting locally and producing specific architectures reliably form a category that transcends the usual dividing line between biological and engineered systems. We propose to call them morphogenetically architected complex systems (MACS). While taking the emergence of properties seriously, the notion of MACS enables at the same time the design (or "meta-design") of operational means that allow controlling and even, paradoxically, programming this emergence.

Functional geometry of the horizontal connectivity in the primary visual cortex.

We present a geometrical model of the functional architecture of the primary visual cortex. In particular we describe the geometric structure of connections found both in neurophysiological and psychophysical experiments, modeling both co-axial and trans-axial excitatory connections. The model shows what could be the deep structure for both boundary and figure completion and for morphological structures such as the medial axis of a shape.

The symplectic structure of the primary visual cortex.

We propose to model the functional architecture of the primary visual cortex V1 as a principal fiber bundle where the two-dimensional retinal plane is the base manifold and the secondary variables of orientation and scale constitute the vertical fibers over each point as a rotation-dilation group. The total space is endowed with a natural symplectic structure neurally implemented by long range horizontal connections. The model shows what could be the deep structure for both boundary and figure completion and for morphological structures, such as the medial axis of a shape.

Dynamical systems and cognitive linguistics: toward an active morphodynamical semantics.

We propose a novel dynamical system approach to cognitive linguistics based on cellular automata and spiking neural networks. How can the same relationship 'in' apply to containers as different as 'box', 'tree' or 'bowl'? Our objective is to categorize the infinite diversity of schematic visual scenes into a small set of grammatical elements and elucidate the topology of language. Gestalt-inspired semantic studies have shown that spatial prepositions such as 'in' or 'above' are neutral toward the shape and size of objects.

An introduction to the Mumford-Shah segmentation model.

Some papers of this special issue concern recent results on mathematical models of segmentation. As they are rather technical we propose here a pedagogical introduction for the non-mathematical reader. We briefly present the variational model of image segmentation proposed by David Mumford and we summarize some fundamental results of De Giorgi's school.

The neurogeometry of pinwheels as a sub-Riemannian contact structure.

We present a geometrical model of the functional architecture of the primary visual cortex (V1) and, more precisely, of its pinwheel structure. The problem is to understand from within how the internal "imminent" geometry of the visual cortex can produce the "transcendent" geometry of the external space. We use first the concept of blowing up to model V1 as a discrete approximation of a continuous fibration pi: R x P --> P with base space the space of the retina R and fiber the projective line P of the orientations of the plane.

[Cardiac Pacemakers, implantable defibrillators and IRM].

The IRM is formally contraindicated to the pacemaker and cardiac defibrillator wearers because of the risk of inhibition or inappropriate stimulations during the examination. However if the examination is essential, suitable programming of the apparatus and a constant monitoring of the heartbeat rate by a qualified doctor in cardiac stimulation must make it possible to avoid any accident.

[Effects of 50 to 60 Hz and of 20 to 50 kHz magnetic fields on the operation of implanted cardiac pacemakers].

Unlabelled: The effect of 50 Hz and 60 Hz (frequencies of current distribution) and 20 kHz to 50 kHz (frequencies of induction cooktop) magnetic interference on implanted pacemakers have been assessed with the present generation of device technology. Sixty patients implanted in 1998 and 1999 with dual chamber pacemakers from 9 different manufacturers were monitored with telemetry while passing through, and standing between a system of two coils. They generated a 50 Hz or a 60 Hz magnetic field at 50 microT.

[Effect of external electrical interference on pacemakers].

Cardiac pacemaker are sensitive to many kind of electromagnetic interference (EMI). However the low rate of reported effects is due to many protective features. Risks are minimal in everyday life conditions as airport detectors, electronic anti-thief systems, domestic electrical appliances and even mobile phones with the most recent models.

Low chronic pacing thresholds of steroid-eluting active-fixation ventricular pacemaker leads: a useful alternative to passive-fixation leads.

Active-fixation pacemaker leads enable pacing at various sites, have a low dislodgment rate, and are easier to extract than passive-fixation leads, though are usually not routinely implanted in the ventricle because of their higher pacing threshold. The long-term pacing threshold associated with an active-fixation steroid-eluting lead was prospectively measured in 18 women and 20 men. At a mean follow-up of 14 months (range 3-25 months), pacing threshold increased from 0.

Cumulative hazard analysis of J-wire fracture in the Accufix series of atrial permanent pacemaker leads.

Unlabelled: To permit a more complete analysis of J-wire fracture in the Accufix series of atrial permanent pacemaker leads, the time to occurrence of all known fractures and injuries has been redefined relative to the duration of risk exposure, that is, according to the interval of time between implant and occurrence of the event. This redefinition permits application of a cumulative hazards model to the data, which previously has not been explored. Predictors of J-wire fracture can be tested using this method.

Kaplan-Meier analysis of freedom from extraction or death in patients with an Accufix J retention wire atrial permanent pacemaker lead: a potential management tool.

Unlabelled: Morbidity (36 cases) and mortality (6 cases) have been reported in patients with Accufix J retention wire atrial leads. This has resulted in ongoing patient fluoroscopic monitoring as well as lead extractions. The estimated implanted worldwide population is 40,860.

Spontaneous versus extraction related injuries associated with Accufix J-wire atrial pacemaker lead: tracking changes in patient management.

Unlabelled: To make recommendations for management of potentially fatal failure of the Accufix series of atrial J-wire permanent pacemaker leads, we closely monitored the number of injuries and fatalities resulting either from spontaneous fracture of the J-wire or from attempts to extract the lead. In a population of 30,357 patients, 2,298 patients are enrolled in a prospective follow-up Multicenter Study, the remainder are patients with known clinical status from voluntary reporting, and 2,992 patients died following implant. In the remaining 27,365 patients, 6 deaths have been attributed to J-wire related injury (J-inj) while 13 were complications (E-inj) associated with 4,076 lead extraction procedures (3,974 intravascular (intra)/102 primary thoracotomy (PT).