Sociology and Systems Analysis

The Management and Technology (MMT) Area of IIASA organizes, from time to time, seminars on topics that are of interest in connection with the work at the Institute. Since MMT sees the importance of investigating the broader management aspects when using systems analytical tools, it was of great interest to have Professor Henk Becker from the University of Utrecht give a seminar on "Sociology of Systems Analysis". As his presentation at this seminar should be of interest to a wider audience, it is now presented in the IIASA Collaborative Paper Series

BPR best practices for the healthcare domain

Healthcare providers are under pressure to work more efficiently and in a more patient-focused way. One possible way to achieve this is to launch Business Process Redesign (BPR) initiatives, which focus on changing the structure of the involved processes and using IT as an enabler for such changes. In this paper, we argue that a list of historically successful improvement tactics, the BPR best practices, are a highly suitable ingredient for such efforts in the healthcare domain. Our assessment is based on the analysis of 14 case studies. The insights obtained by the analysis also led to an extension of the original set of best practices

Expansion in perfect groups

Let Ga be a subgroup of GL_d(Q) generated by a finite symmetric set S. For an integer q, denote by Ga_q the subgroup of Ga consisting of the elements that project to the unit element mod q. We prove that the Cayley graphs of Ga/Ga_q with respect to the generating set S form a family of expanders when q ranges over square-free integers with large prime divisors if and only if the connected component of the Zariski-closure of Ga is perfect.Comment: 62 pages, no figures, revision based on referee's comments: new ideas are explained in more details in the introduction, typos corrected, results and proofs unchange

Growth Differentiation Factor 15 at 1 Month After an Acute Coronary Syndrome Is Associated With Increased Risk of Major Bleeding.

BACKGROUND: Growth differentiation factor-15 (GDF-15) is related to major bleeding when measured at initial presentation in patients with acute coronary syndromes (ACSs) treated with dual antiplatelet therapy. It is unknown whether follow-up measurements provide additional information. The objective of this study was to investigate whether GDF-15 measured 1 month after an ACS provides additional information beyond the baseline levels with regard to the risk of major bleeding. METHODS AND RESULTS: GDF-15 was measured at baseline and at 1 month after an ACS in 4049 patients included in the PLATelet inhibition and patient Outcomes (PLATO) trial. The association between 1-month GDF-15 level and non-coronary artery bypass grafting surgery-related major bleeding was assessed by a multivariable Cox model, adjusting for baseline GDF-15, age, anemia, impaired renal function, history of gastrointestinal bleeding, and sex. Elevated GDF-15 (>1800 ng/L) at 1 month was associated with an increased risk of non-coronary artery bypass grafting-related major bleeding (3.9% versus 1.2%; hazard ratio, 3.38; 95% CI, 1.89-6.06), independent of baseline GDF-15. Patients who had elevated GDF-15 levels at baseline and subsequent nonelevated GDF-15 at 1 month had a similar risk as patients who had nonelevated levels at both measurements. CONCLUSIONS: GDF-15 at 1 month after an ACS is related to the risk of bleeding during DAPT and provides additional information on the bleeding risk beyond baseline GDF-15 levels. GDF-15 levels may therefore be useful as part of decision support concerning long-term antithrombotic treatment in patients post-ACS. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00391872

Fundamental studies of the adhesion of explosives to textile and non-textile surfaces

This paper describes the use of atomic force microscopy (AFM) to investigate the interactions between explosives crystals and different surfaces. Crystals of TNT, PETN and RDX were mounted onto tipless AFM cantilevers and repeatedly brought into contact with a range of surfaces (n = 15), including textile and non-textile surfaces. The adhesion force during each contact was measured, and the results are presented in this work. The results suggest that explosives crystals display a higher adhesion to smoother, non-textile surfaces, particularly glass. This finding may be of use for forensic explosives investigators when deciding the best types of debris to target for explosives recovery

The N-methyl-d-aspartate receptor antagonist CPP alters synapse and spine structure and impairs long-term potentiation and long-term depression induced morphological plasticity in dentate gyrus of the awake rat

Long-term morphological synaptic changes associated with homosynaptic long-term potentiation (LTP) and heterosynaptic long-term depression (LTD) in vivo, in awake adult rats were analyzed using three-dimensional (3-D) reconstructions of electron microscope images of ultrathin serial sections from the molecular layer of the dentate gyrus. For the first time in morphological studies, the specificity of the effects of LTP and LTD on both spine and synapse ultrastructure was determined using an N-methyl-d-aspartate (NMDA) receptor antagonist CPP (3-[(R)-2-carboxypiperazin-4-yl]-propyl-1-phosphonic acid). There were no differences in synaptic density 24 h after LTP or LTD induction, and CPP alone had no effect on synaptic density. LTP increased significantly the proportion of mushroom spines, whereas LTD increased the proportion of thin spines, and both LTP and LTD decreased stubby spine number. Both LTP and LTD increased significantly spine head evaginations (spinules) into synaptic boutons and CPP blocked these changes. Synaptic boutons were smaller after LTD, indicating a pre-synaptic effect. Interestingly, CPP alone decreased bouton and mushroom spine volumes, as well as post-synaptic density (PSD) volume of mushroom spines.These data show similarities, but also some clear differences, between the effects of LTP and LTD on spine and synaptic morphology. Although CPP blocks both LTP and LTD, and impairs most morphological changes in spines and synapses, CPP alone was shown to exert effects on aspects of spine and synaptic structure

Three-sphere low-Reynolds-number swimmer with a passive elastic arm

One of the simplest model swimmers at low Reynolds number is the three-sphere swimmer by Najafi and Golestanian. It consists of three spheres connected by two rods which change their lengths periodically in non-reciprocal fashion. Here we investigate a variant of this model in which one rod is periodically actuated while the other is replaced by an elastic spring. We show that the competition between the elastic restoring force and the hydrodynamic drag produces a delay in the response of the passive elastic arm with respect to the active one. This leads to non-reciprocal shape changes and self-propulsion. After formulating the equations of motion, we study their solutions qualitatively and numerically. The leading-order term of the solution is computed analytically. We then address questions of optimization with respect to both actuation frequency and swimmer\u2019s geometry. Our results can provide valuable conceptual guidance in the engineering of robotic microswimmers

Evaluating the Cost of Enforcement by Agent-Based Simulation:A Wireless Mobile Grid Example

The subject of this paper is the cost of enforcement, to which we take a satisficing approach through the examination of marginal cost-benefit ratios. Social simulation is used to establish that less enforcement can be beneficial overall in economic terms, depending on the costs to system and/or stakeholders arising from enforcement. The results are demonstrated by means of a case study of wireless mobile grids (WMGs). In such systems the dominant strategy for economically rational users is to free-ride, i.e. to benefit from the system without contributing to it. We examine the use of enforcement agents that police the system and punish users that take but do not give. The agent-based simulation shows that a certain proportion of enforcement agents increases cooperation in WMG architectures. The novelty of the results lies in our empirical evidence for the diminishing marginal utility of enforcement agents: that is how much defection they can foreclose at what cost. We show that an increase in the number of enforcement agents does not always increase the overall benefits-cost ratio, but that with respect to satisficing, a minimum proportion of enforcement agents can be identified that yields the best results. © 2013 Springer-Verlag

Oscillation enhanced search for new interaction with neutrinos

We discuss the measurement of new physics in long baseline neutrino oscillation experiments. Through the neutrino oscillation, the probability to detect the new physics effects such as flavor violation is enhanced by the interference with the weak interaction. We carefully explain the situations that the interference can take place. Assuming a neutrino factory and an upgraded conventional beam, we estimate the feasibility to observe new physics numerically and point out that we can search new interactions using some channels, for example $\nu_{\mu} \to \nu_{\mu}$, in these experiments. We also discuss several models which induce the effective interactions interfering with the weak interaction, and show that some new physics effects are large enough to be observed in the oscillation enhanced way.Comment: 25 pages, 20 figure