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Comparing Chemical Reaction Networks:A Categorical and Algorithmic Perspective
No full textWe study chemical reaction networks (CRNs) as a kernel language for concurrency models with semantics based on ordinary differential equations. We investigate the problem of comparing two CRNs,i.e., to decide whether the trajectories of asource CRN can be matched by a target CRN under an appropriate choice of initial conditions. Using a categorical framework, we extend and relate model-comparison approaches based on structural (syntactic) and on dynamical (semantic) properties of a CRN, proving their equivalence. Then, we provide an algorithm to compare CRNs, running linearly in time with respect to the cardinality of all possible comparisons. Finally, we apply our results to biological models from the literature
Access to Medicines and European Market Integration
No full textIn this paper we document a process of price convergence in the European market for pharmaceuticals and relate it to access to innovative medicines in individual countries. The EU is a peculiar case study, where free circulation of goods exists, but pricing policies are designed and implemented by Member States. Thanks to a unique census database on product sales and launches
for fifteen EU countries, we detect a process of price convergence, both in nominal and in real
terms. Therefore, we find that a faster rate of price convergence and a lower income per capita are
associated with stronger delays in launches of new medicines. Moreover, country delays tend to
be higher for innovative and first in class chemical compounds. Our results suggest that inefficiencies arise from drugs regulation, when countries widely differ in income per capita, public finance
sustainability conditions, and regulatory frameworks. Policies of external reference pricing tend to
exacerbate welfare losses. A policy of differential pricing is suggested, in order to take into account
both therapeutic value and willingness to pay
Binary and multi-class classification of parkinsonian disorders with support vector machines based on quantitative brain MR and graph-based features
No full textDesign of acoustic metamaterials through nonlinear programming
No full textThe dispersive wave propagation in a periodic metamaterial with tetrachiral topology and inertial local resonators is investigated. The Floquet-Bloch spectrum of the metamaterial is compared with that of the tetrachiral beam lattice material without resonators. The resonators can be designed to open and shift frequency band gaps, that is, spectrum intervals in which harmonic waves do not propagate. Therefore, an optimal passive control of the frequency band structure can be pursued in the metamaterial. To this aim, a suitable constrained nonlinear optimization problem on a compact set of admissible geometrical and mechanical parameters is stated. According to functional requirements, the particular set of parameters which determines the largest low-frequency band gap between a pair of consecutive branches of the Floquet-Bloch spectrum is obtained. The optimization problem is successfully solved by means of a version of the method of moving asymptotes, combined with a quasi-Monte Carlo multi-start technique.
Subjects: Materials Science (cond-mat.mtrl-sci)
Cite as: arXiv:1603.07717 [cond-mat.mtrl-sci]
(or arXiv:1603.07717v2 [cond-mat.mtrl-sci] for this version
Towards an Economy of the Body
No full textThis paper focuses on three main cases: Étienne-Jules Marey (1830-1904), Georges Demeny (1850-1917) and the Gilbreths (Frank B. Gilbreth, 1868-1924 and Lillian M. Gilbreth, 1878-1972), and their respective studies of movement.
More specifically, it investigates Marey’s and Demeny’s experiments with fix plate chronophotography (1883-1886) focused on human locomotion, Demeny’s research with chronophotography on sensitive strip and celluloid film studying gymnastics (1888-1892), and Frank and Lillian Gilbreth’s work on the cyclograph (as expounded in Fatigue Study and Applied Motion Study).
Firstly, the paper analyzes the three different procedural protocols of these experiments in order to identify their similarities and differences and to understand what, if any, experimental model they give rise to. It scrutinizes in particular: a) the position of the scientist’s body in the experimental field and its role in theory (the training of the observer’s/scientist’s body); b) the preparation of the body of the subjects to be analyzed (before the experiments) and the way these bodies were posed in the experimental field (during the experiments); c) the status of the camera’s mechanical body.
Secondly and finally, the paper aims to show how all these regulatory norms serve and enable a certain economy of the body in two interconnected senses: a) economy as a form of reduction. The paper analyzes different ways the body inside the experimental field is isolated/deleted depending on whether it is the scientist’s body, the subject’s body under analysis or the body of the camera; b) economy as a system of efficiency. Beginning from M. Mauss’s notion of “techniques du corps” as a general theoretical framework as well as specific examples of disciplining effects on individuals (See Phéline, Christian. L'image accusatrice. Laplume, France: Association de critique contemporaine en photographie, 1985), this paper seeks to outline the historical role played by the abovementioned studies of the body in developing efficiency (and its relationship with work) as an object of knowledge
A probabilistic interpretation of set-membership filtering: application to polynomial systems through polytopic bounding
No full textSet-membership estimation is usually formulated in the context of set-valued calculus and no probabilistic calculations are necessary. In this paper, we show that set-membership estimation can be equivalently formulated in the probabilistic setting by employing sets of probability measures. Inference in set-membership estimation is thus carried out by computing expectations with respect to the updated set of probability measures PP as in the probabilistic case. In particular, it is shown that inference can be performed by solving a particular semi-infinite linear programming problem, which is a special case of the truncated moment problem in which only the zeroth order moment is known (i.e., the support). By writing the dual of the above semi-infinite linear programming problem, it is shown that, if the nonlinearities in the measurement and process equations are polynomial and if the bounding sets for initial state, process and measurement noises are described by polynomial inequalities, then an approximation of this semi-infinite linear programming problem can efficiently be obtained by using the theory of sum-of-squares polynomial optimization. We then derive a smart greedy procedure to compute a polytopic outer-approximation of the true membership-set, by computing the minimum-volume polytope that outer-bounds the set that includes all the means computed with respect to P
Leaf segmentation in plant phenotyping: a collation study
No full textImage-based plant phenotyping is a growing application area of computer vision in agriculture. A key task is the segmentation of all individual leaves in images. Here we focus on the most common rosette model plants, Arabidopsis and young tobacco. Although leaves do share appearance and shape characteristics, the presence of occlusions and variability in leaf shape and pose, as well as imaging conditions, render this problem challenging. The aim of this paper is to compare several leaf segmentation solutions on a unique and first-of-its-kind dataset containing images from typical phenotyping experiments. In particular, we report and discuss methods and findings of a collection of submissions for the first Leaf Segmentation Challenge of the Computer Vision Problems in Plant Phenotyping workshop in 2014. Four methods are presented: three segment leaves by processing the distance transform in an unsupervised fashion, and the other via optimal template selection and Chamfer matching. Overall, we find that although separating plant from background can be accomplished with satisfactory accuracy ( > 90 % Dice score), individual leaf segmentation and counting remain challenging when leaves overlap. Additionally, accuracy is lower for younger leaves. We find also that variability in datasets does affect outcomes. Our findings motivate further investigations and development of specialized algorithms for this particular application, and that challenges of this form are ideally suited for advancing the state of the art. Data are publicly available (online at http://www.plant-phenotyping.org/datasets ) to support future challenges beyond segmentation within this application domain
Pathways towards instability in financial networks
No full textThere is growing consensus that processes of market integration and risk diversification may come at the price of more systemic risk. Indeed, financial institutions are interconnected in a network of contracts where distress can either be amplified or dampened. However, a mathematical understanding of instability in relation to the network topology is still lacking. In a model financial network, we show that the origin of instability resides in the presence of specific types of cyclical structures, regardless of many of the details of the distress propagation mechanism. In particular, we show the existence of trajectories in the space of graphs along which a complex network turns from stable to unstable, although at each point along the trajectory its nodes satisfy constraints that would apparently make them individually stable. In the financial context, our findings have important implications for policies aimed at increasing financial stability. We illustrate the propositions on a sample dataset for the top 50 EU listed banks between 2008 and 2013. More in general, our results shed light on previous findings on the instability of model ecosystems and are relevant for a broad class of dynamical processes on complex networks