MOX Reports
The preprint collection of the Laboratory for Modeling and Scientific Computation MOX. It mainly contains works on numerical
analysis and mathematical modeling applied to engineering problems. MOX web site is mox.polimi.it
Found 1253 products
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11/2011 - 02/20/2011
Formaggia, L.; Minisini, S.; Zunino, P.
Stent a rilascio di farmaco: una storia di successo per la matematica applicata | Abstract | | In the last decades the adoption of mathematical models to support medical research has found a considerable increase of interest, stimulating
the activity of applied mathematicians. A better understanding of the physical and biological phenomena together with the availability of powerful and affordable computers has prompted the use of numerical simulation as a complement, even if not yet as a substitute, of animal experimentation and clinical trials. In the case considered here, namely that of particular drug
eluting devices used in the treatment of arteriosclerosis, it allows for the evaluation of the effect of different designs of the device, or different type of drugs. In this article we give a review of mathematical models used for simulating the functioning of drug eluting stents. We start by considering the simplest models, based on empirical formulae or ordinary differential equations, up to models based on systems of partial differential equations that describe the drug elution processes coupled with the diffusion and transport of the drug in biological tissues and blood flow. |
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10/2011 - 02/19/2011
Zunino, P.; Vesentini, S.; Porpora, A.; Soares, J.S.; Gautieri, A.; Redaelli, A.
Multiscale computational analysis of degradable polymers | Abstract | | Degradable materials have found a wide variety of applications in the biomedical field ranging from sutures, pins and screws for orthopedic surgery, local drug delivery, tissue engineering scaffolds, and endovascular stents. Polymer degradation is the irreversible chain scission process that breaks polymer chains down to oligomers and, finally, to monomers. These changes, which take place at the molecular scale, propagate through the space/time scales and not only affect the
capacity of the polymer to release drugs, bu also hamper the overall mechanical behavior of the device, whose spatial scale is denoted as macro-scale. A bottom-up multiscale analysis is applied to model the degradation mechanism which takes
place in PLA matrices. The macroscale model is based on diffusion-reaction equations for hydrolytic polymer degradation and erosion while the microscale model is based on atomistic simulations to predict the water diffusion as a function of the swelling degree of the PLA matrix. The diffusion coefficients are then passed to the macroscale model. In conclusion, the proposed multiscale analysis is capable to predict the evolution with time of several properties of water/PLA mixtures, according to the change of relevant indicators such as the extent of degradation
and erosion of the PLA matrix.
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09/2011 - 02/18/2011
Pigoli, D.; Sangalli, L.
Wavelets in Functional Data Analysis: estimation of multidimensional curves and their derivatives | Abstract | | A wavelet-based method is proposed to obtain accurate estimates of curves in more than one dimension and of their derivatives. By means
of simulation studies, we compare this novel method to another locally-adaptive estimation technique for multidimensional functional data, based on free-knot regression splines. This comparison shows that the proposed method is particularly attractive when the curves to be estimated present strongly localized features. The multidimensional wavelet estimation method is thus applied to multi-lead electrocardiogram records, where strongly localized features are indeed expected. |
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08/2011 - 02/17/2011
Ieva, F.; Paganoni, A.M.; Secchi, P.
Mining Administrative Health Databases for epidemiological purposes: a case study on Acute Myocardial Infarctions diagnoses | Abstract | | We present a pilot data mining analysis on the subset of the Public Health Database of Lombardia Region concerning hospital discharge data relative to Acute Myocardial Infarctions without ST segment elevation (NON-STEMI). The analysis is carried out using non linear semi parametric and parametric mixed effects models, in order to detect different patterns of growth in the number of NON-STEMI
diagnoses within the 30 largest clinical structures of Lombardia Region, along the time period 2000-2007. The analysis is a seminal example of statistical support to decision makers in clinical context, aimed at monitoring the diffusion of new procedures and the effects of health policy interventions. |
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07/2011 - 02/16/2011
Arioli, G.; Gamba, M.
Automatic computation of Chebyshev polynomials for the study of parameter dependence for hyperbolic systems | Abstract | | We introduce a new intrusive method for studying the parameter dependence of solutions of hyperbolic systems having sharp discontinuities.
Two applications to the study of solutions of Euler s system are presented. |
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06/2011 - 01/20/2011
Secchi, P.; Stamm, A.; Vantini, S.
Large p Small n Data: Inference for the Mean | Abstract | | We provide a generalization of Hotelling’s Theorem that enables inference (i)for the mean vector of a multivariate normal population and (ii) for the comparison of the mean vectors of two multivariate normal populations, when the number p of components is larger than the number n of sample units and the (common) covariance matrix is unknown. We find suitable test statistics and their p-asymptotic
distributions that allow the inferential analysis of large p small n data. |
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05/2011 - 01/18/2011
Arioli, G.; Gamba, M.
An algorithm for the study of parameter dependence for hyperbolic systems | Abstract | | We introduce a new technique for computing the explicit dependence of the result of the numerical integration of a conservation law with respect to one or more parameters. The method is intrusive, but it relies on an automatic differentiation algorithm, therefore it requires minimal modi cations of the code used for the plain numerical integration. We present
an example of application to the study of the shock tube, that is Euler s system of equations with discontinuous initial conditions. |
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04/2011 - 01/14/2011
Ieva, F.; Paganoni, A.M.; Pigoli, D.; Vitelli, V.
Multivariate functional clustering for the analysis of ECG curves morphology | Abstract | | Cardiovascular diseases are one of the main causes of death all over the world.
In this kind of pathologies, it is fundamental to be well-timed in order to obtain good prognosis in reperfusive treatment. In particular, an automatic classification procedure based on statistical analyses of tele-transmitted ECG traces would be very helpful for an early diagnosis. This work is a pilot analysis on electrocardiographic ECG) traces (both normal and pathological ones) of patients whose 12-leads pre-hospital ECG has been sent by life supports to 118 Dispatch Center of Milan. The statistical analysis consists of preliminary steps like reconstructing signals, wavelets denoising and removing the biological variability in the signals
through data registration.
Then, a multivariate functional k-means clustering of reconstructed and registered ECGs is performed, and performances of classification
method are validated. So a semi-automatic diagnostic procedure, based on the sole ECG’s morphology, is proposed to classify patients and predict pathologies. |
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