26 Giugno, 2017 14:00

MOX Colloquia

Imaging the brain microstructure with diffusion-weighted MRI

Maxime Taquet, University of Louvain and Harvard Medical School

Aula Consiglio, VII piano - Dipartimento di Matematica, Politecnico di Milano - Edificio 14

abstract

abstract

The brain microstructure is the complex organization of axons, neurons and other cells that support the neural functions. Its mapping at the whole-brain level holds promise to the identification and characterization of neurological and psychiatric disorders as well as the assessment of response to treatment. Diffusion-weighted imaging has been at the forefront of developments of brain microstructure imaging. It is based on the recording of movements of pools of water molecules as they hit the cellular barriers in the brain. In this talk, I will provide a gentle introduction to DWI and microstructure imaging, present some recent developments and outline exciting challenges that the field is currently facing.

Maxime Taquet is a post-doctoral research fellow at Harvard Medical School and the University of Louvain and currently studies medicine as a graduate-entry student at the University of Oxford.

26 Giugno, 2017 16:00

Seminario Matematico e Fisico di Milano

BIFURCATIONS OF MULTI-VORTEX CONFIGURATIONS IN ROTATING BOSE-EINSTEIN CONDENSATE

Dmitry Pelinovsky, McMaster University

Sala di Rappresentanza, Dipartimento di Matematica, Via Saldini 50

abstract

abstract

Global bifurcations along the family of radially symmetric vortices are analyzed for the Gross-Pitaevskii equation with a symmetric harmonic potential and a chemical potential under the steady rotation. The families are constructed in the small-amplitude limit when the chemical potential is close to an eigenvalue of the Schrodinger operator for a quantum harmonic oscillator. Each bifurcation results in the disappearance of a pair of negative eigenvalues in the Hessian operator at the radially symmetric vortex. The distributions of vortices in the bifurcating families are analyzed by using symmetries of the Gross-Pitaevskii equation and the zeros of Hermite-Gauss eigenfunctions. The vortex configurations that can be found in the bifurcating families are the asymmetric vortex, the asymmetric vortex pair, and the vortex polygons.

Maxime Taquet is a post-doctoral research fellow at Harvard Medical School and the University of Louvain and currently studies medicine as a graduate-entry student at the University of Oxford.

21 Giugno, 2017 10:15 in punto

MOX Seminar

Copyright, Licensing and Patents for Scientific Software

Carlo Piana, Array

Aula Consiglio, 7th Floor - Dept. of Mathematics, Politecnico di Milano - Edificio 14, via Bonardi 9

abstract

abstract

Carlo Piana will outline the legal protection of software in terms of copyright, patents and other applicable laws, from an historical and practical viewpoint. Moving from the legal background, he will introduce the concepts of Free and open source software (FOSS) licensing and practice in different areas, from traditional C-style programming, to the embedded and Software as a Service (cloud) worlds. He will cover the different licensing models under the different copyleft categories, and the business models that he have encountered in his legal and activists' life, providing the basic tools to understand licensing and compliance when using and working with FOSS.
Carlo Piana is an IT lawyer based in Milano, partner and founder of Array (array.eu), serves as external General Counsel of the Free Software Foundation Europe (fsfe.org)

Maxime Taquet is a post-doctoral research fellow at Harvard Medical School and the University of Louvain and currently studies medicine as a graduate-entry student at the University of Oxford.

20 Giugno, 2017 14:00

Sezione di Finanza Quantitativa

The macroeconomic effects of ECB Asset Purchases at the ZLB in four major Euro Area countries (co-author Guido Bulligan)

Simone Emiliozzi, Banca d’Italia

Aula Seminari VI piano

abstract

abstract

In this paper we propose a nonlinear structural FAVAR model that is able to handle the ZLB on nominal interest rates in order to examine the impact of ECB asset purchases on macroeconomic and financial variables in the four largest economies of the Euro area. We find that they have an heterogeneous e ffect in stimulating real activity variables of the countries considered while they seem eff ective in increasing inflation in the Euro Area. The portfolio rebalancing and the bank lending channel are the main drivers for the transmission of ECB asset purchases shocks to the real economy while con fidence and the exchange rate channel seem to play a minor role instead. Furthermore we propose a new shadow rate for the EA that is estimated using information coming from both financial and macroeconomic variables and compare it with alternatives proposed in the literature. Finally we compute the the lift-off probability for the ECB monetary policy short-term interest rate (MRO) and find that, as of December 2015, the Euro Area would escape the ZLB trap in the second half of 2019.

Maxime Taquet is a post-doctoral research fellow at Harvard Medical School and the University of Louvain and currently studies medicine as a graduate-entry student at the University of Oxford.

19 Giugno, 2017 11:00

MOX Seminar

Electron Cooling Modelling

Andrea Latina, CERN - European Organization for Nuclear Research

Aula Seminari "F. Saleri", MOX

abstract

abstract

The aim of any cooling process is to reduce the phase-space occupancy of a beam of ions or (anti)protons as quickly as possible. This is of paramount importance in particle accelerators for high-energy physics, where the luminosity delivered to experiments is inversely proportional to the transverse size of the colliding beams. Among the few processes in use, Electron Cooling, where the beam is sent through a magnetized plasma of cold electrons, is the most efficient.
Only few codes that can simulate Electron Cooling exist, with a limited degree of realism. Yet a realistic simulation is crucial to take into account imperfections and improve the performance of the cooler in a real experimental environment. A new numerical model of the Electron Cooling will be presented: a hybrid model based on kinetic ions and fluid electrons, immersed in a solenoidal magnetic field. It combines the challenges of symplectic tracking in particle accelerators with concepts of plasma physics in presence of strong magnetic fields. After a short reminder of the principles involved, the major challenges will be presented and the model explained.
Contatto: carlo.defalco@polimi.it

Maxime Taquet is a post-doctoral research fellow at Harvard Medical School and the University of Louvain and currently studies medicine as a graduate-entry student at the University of Oxford.

16 Giugno, 2017 14:15 in punto

Sezione di Geometria, Algebra e loro applicazioni

Large sets of Kirkman triple systems

Junling Zhou, Department of Mathematics, Beijing Jiaotong University, P. R. China

Aula seminari III piano

abstract

abstract

Research on the existence of large sets of Kirkman triple systems (LKTS) extends from the mid-eighteen hundreds to the present. However this problem is still wide open until now. In this talk, direct and recursive constructions of LKTS will be reviewed. Some new results will be introduced.

Maxime Taquet is a post-doctoral research fellow at Harvard Medical School and the University of Louvain and currently studies medicine as a graduate-entry student at the University of Oxford.

16 Giugno, 2017 14:40 in punto

Sezione di Geometria, Algebra e loro applicazioni

Decompositions of the complete n-partite equipartite multigraph with any minimum leave and minimum excess

Tao Feng, Department of Mathematics, Beijing Jiaotong University, P. R. China

Aula seminari III piano

abstract

abstract

A decomposition of ?K_n(g) \ L, the complete n-partite equipartite multigraph with a subgraph L (called the leave) removed, into edge disjoint copies of a graph G is called a maximum group divisible packing of ?K_n(g) with G if L contains as few edges as possible. A decomposition of ?K_n(g) ? E, the complete n-partite equipartite multigraph union a graph E (called the excess), into edge disjoint copies of a graph G is called a minimum group divisible covering of ?Kn(g) with G if E contains as few edges as possible.

We continue Billington and Lindner’s work in [1] to examine all possible minimum leaves for maximum group divisible packings of ?Kn(g) with G and all possible excesses for minimum group divisible coverings of ?Kn(g) with G, where G is a triangle K3, or a triangle plus one dangling edge K3 + e, or K4 ? e [2, 3]. When G is K4, the problem is closely related with many other combinatorial con?gurations, such as balanced sampling plans excluding contiguous units, matching divisible designs, etc. We shall show that the obvious divisibility conditions are su?cient for the existence of matching divisible designs with block size four [4].

References

[1] E.J. Billington, C.C. Lindner, Maximum packings of uniform group divisible triple systems, J. Combin. Designs, 4 (1996), 397–404.

[2] X. Hu, Y. Chang, and T. Feng, Group divisible packings and coverings with any minimum leave and minimum excess, Graphs and Combinatorics, 32 (2016), 1423–1446.

[3] Y. Gao, Y. Chang, and T. Feng, Group divisible (K4 ? e)-packings with any minimum leave, arXiv:1705.08787.

[4] P.J. Dukes, T. Feng, A.C.H. Ling, Matching divisible designs with block size four, Discrete Math., 339 (2016), 790–799.

Maxime Taquet is a post-doctoral research fellow at Harvard Medical School and the University of Louvain and currently studies medicine as a graduate-entry student at the University of Oxford.

16 Giugno, 2017 15:30 in punto

Sezione di Geometria, Algebra e loro applicazioni

Designs with speci?c automorphism group

Yanxun Chang, Department of Mathematics, Beijing Jiaotong University, P. R. China

Aula seminari III piano

abstract

abstract

Let v, k and t be positive integers such that v > k > t. A Steiner t-wise balanced design (brie?y S(t,k,v)) is a pair (X,B), where X is a set of v points and B is a set of k-subsets of X (called blocks) such that every t-subset of X is contained in a unique block. An automorphism group of a S(t,k,v) (X,B) is a permutation group on X leaving B invariant. In this talk, we consider Steiner t-wise balanced design with speci?c automorphism. Some direct and recursive constructions on this topics are summarized.

Maxime Taquet is a post-doctoral research fellow at Harvard Medical School and the University of Louvain and currently studies medicine as a graduate-entry student at the University of Oxford.

15 Giugno, 2017 14:00

MOX Colloquia

Dynamical inverse problems in glucose metabolism of cancer

Michele Piana, Università di Genova, Dipartimento di Matematica

Aula Consiglio, VII piano - Dipartimento di Matematica, Politecnico di Milano - Edificio 14

abstract

abstract

Glucose metabolism in cancer can be mapped by using positron emission tomography (PET). however, PET data interpration requires the use of regularization techniques for both reconstructing functional images of tissue proliferation and detemining the kinetic parameters that explain the effectivenes of information flow between functional compartments. this talk will illustrate a mathematical model for glucose physiology in healthy and cancerous tissues and how such model can be numerically reduced in order to provide quantitative information on glucose pato-physiology

Michele Piana is Professor of Numerical Analysis at the Dipartimento di Matematica, Università di Genova, Research Associate at CNR - SPIN and Honorary Research Fellow at the Department of Physics, University of Glasgow. He is Principal Investigator of the 'Methods for Image and Data Analysis (MIDA)' group, which is a joint UNIGE-CNR research lab developing computational techniques for data interpretation in physics and physiology. He is currently vice-Rector for Research and Technology Transfer at the Università di Genova.

14 Giugno, 2017 14:15

Sezione di Analisi

A gradient flow approach to a porous medium equation with fractional pressure

Antonio Segatti, Università degli studi di Pavia

Aula seminari 3° piano

abstract

abstract

In this seminar I will show how a porous medium equation with fractional pressure,
that has been recently introduced and studied by Caffarelli and Vazquez,can be understood as
a Wasserstein gradient flow.
The results include the energy dissipation inequality, the regularizing effect and decay estimates for the L^p norms.
This is a joint work with S. Lisini and E. Mainini. dimat.unipv.it/segatti

Michele Piana is Professor of Numerical Analysis at the Dipartimento di Matematica, Università di Genova, Research Associate at CNR - SPIN and Honorary Research Fellow at the Department of Physics, University of Glasgow. He is Principal Investigator of the 'Methods for Image and Data Analysis (MIDA)' group, which is a joint UNIGE-CNR research lab developing computational techniques for data interpretation in physics and physiology. He is currently vice-Rector for Research and Technology Transfer at the Università di Genova.