On the origin of satellite swarms

For a species to develop in nature, two basically two things are needed: an enabling technology and a "niche". In spacecraft design the story is basically the same. Both a suitable technology and a niche application need to be there before a new generation of spacecraft can be developed. Last century two technologies have emerged that had and still have a huge impact on the development of technical systems: Micro-Electronics (ME) and Micro-Systems Technology (MST). Both are ruled by Moore's Law that indicates that considerable technology updates appear at the pace of years or even months instead of decades. Systems that need a development time of more than a few years will inevitably be based on "out-dated" and thereby difficult to maintain and repair technology unless during the development constant redesigns are made. This makes the development of the system at least very expensive. Although expenses do not seem to be a frequent show stopper in the design of spacecraft, it is still very interesting to investigate what system architectures might evolve when the specific properties of the new technologies ME and MST are fully exploited. ME presently offers more than 2 billion transistors on a chip and MST offers mechanical systems like resonators, mechanical switches, propulsions units, gyroscopes and many other sensors that _t in a volume of a few square millimeters to a few centimeters. So it is possible to fit a lot of signal processing power together with the necessary sensors and actuators in a volume that is really very small compared to any know space system. Of course state-of-the art spacecraft will immediately outperform these units in all aspects apart from cost and quantity. For the _rst time it makes sense to envisage the operation of formations of tens to hundreds of satellites that are cheap because they are based on standard commercial COTS technology and system designs. These satellite swarms will not be the systems that replace all other space systems. But, like in nature, there is a niche where swarms are the optimal solution. It's time to start occupying this niche. Typical properties of a swarm in nature are robustness, redundancy, large area coverage, the lack a hierarchical command structure, limited processing power per unit and self-organization ("swarm-intelligence"). This paper discusses the technological trends that lead to satellite swarms, where they can go and what new science they can create

Aspects of insulin sensitivity in childhood and adolescence

Delemarre-van De Waal, H.A. [Promotor]Weissenbruch, M.M. van [Copromotor

The development of TGFβR1 PET tracers for in vivo imaging

This thesis focusses on the diagnosis of Pulmonary arterial hypertension (PAH). The disease is still difficult to diagnose as early symptoms related to PAH are vague and non-specific [1]. Right heart catheterization is the gold standard to diagnose PAH, but this technique is very invasive. Doppler echocardiography can be used to diagnose PAH in symptomatic patients, but in asymptomatic and mildly symptomatic patients its value has been questioned. Consequently, PAH is normally diagnosed when this pulmonary vascular disease is already advanced. Clearly, alternative non-invasive diagnostic tools for early detection of PAH are needed, which potentially may lead to a reduction in mortality rate. To date, there are no non-invasive molecular imaging methods to confirm the diagnosis of PAH. Multiple in vivo studies have revealed the importance of the transforming growth factor β (TGFβ) pathway in PAH. Consequently, imaging of ALK5 may provide opportunities to study the role of ALK5 in PAH, thereby providing better insight into the pathology and progression of this disease

Affective Monitoring: A Generic Mechanism for Affect Elicitation

In this paper we sketch a new framework for affect elicitation, which is based on previous evolutionary and connectionist modeling and experimental work from our group. Affective monitoring is considered a local match–mismatch process within a module of the neural network. Negative affect is raised instantly by mismatches, incongruency, disfluency, novelty, incoherence, and dissonance, whereas positive affect follows from matches, congruency, fluency, familiarity, coherence, and resonance, at least when an initial mismatch can be solved quickly. Affective monitoring is considered an evolutionary-early conflict and change detection process operating at the same level as, for instance, attentional selection. It runs in parallel and imparts affective flavor to emotional behavior systems, which involve evolutionary-prepared stimuli and action tendencies related to for instance defensive, exploratory, attachment, or appetitive behavior. Positive affect is represented in the networks by high-frequency oscillations, presumably in the gamma band. Negative affect corresponds to more incoherent lower-frequency oscillations, presumably in the theta band. For affect to become conscious, large-scale synchronization of the oscillations over the network and the construction of emotional experiences are required. These constructions involve perceptions of bodily states and action tendencies, but also appraisals as well as efforts to regulate the emotion. Importantly, affective monitoring accompanies every kind of information processing, but conscious emotions, which result from the later integration of affect in a cognitive context, are much rarer events