Topological susceptibility with a single light quark flavour

One of the historical suggestions to tackle the strong CP problem is to take the up quark mass to zero while keeping $m_d$ finite. The $\theta$ angle is then supposed to become irrelevant, i.e. the topological susceptibility vanishes. However, the definition of the quark mass is scheme-dependent and identifying the $m_u=0$ point is not trivial, in particular with Wilson-like fermions. More specifically, up to our knowledge there is no theoretical argument guaranteeing that the topological susceptibility exactly vanishes when the PCAC mass does. We will present our recent progresses on the empirical check of this property using $N_f=1+2$ flavours of clover fermions, where the lightest fermion is tuned very close to $m^{PCAC}_u$=0 and the mass of the other two is kept of the order of magnitude of the physical $m_s$. This choice is indeed expected to amplify any unknown non-perturbative effect caused by $m_u\not=m_d$. The simulation is repeated for several $\beta$s and those results, although preliminary, give a hint about what happens in the continuum limit.Comment: 8 pages, 3 figures, Presented at Lattice2017, the 35th International Symposium on Lattice Field Theory at Granada, Spain (18-24 June 2017

Exploring the landscape of reflection

open4noopenFrison, Daniela; Fedeli, Monica; Tino, Concetta; Minnoni, ErikaFrison, Daniela; Fedeli, Monica; Tino, Concetta; Minnoni, Erik

Work-related teaching and learning methods to foster generic skills in Higher Education. An Italian experience

open5siWithin the framework of modernisation of higher education systems in Europe, universities are invited to go beyond a knowledge-based perspective focused on disciplinary approaches and to be more concentrated on encouraging generic skills to deal with today’s complex and unpredictable career paths. The literature about Work-Related Learning and Work-Integrated Learning offers evidence to research regarding contributions of work-related experiences to the development of generic skills. The first part of the article presents a literature review carried out following the matching among three main keywords: work-related learning, generic skills, and higher education. Resources focused on the integration/teaching of generic skills in formal curriculum or in co-curriculum work-related activities and they were collected in order to explore the link between work-related learning in higher education and the development of generic skills. The focus is to identify valuable considerations to improve teaching strategies and methods. The second part presents an Italian work-related experience developed within the course of “Organizational Intervention Research Methods,” which involved 22 master’s degree students. The work-related assignment will be described in addition to the content analysis process of the 22 collected texts and the findings about the development of generic skills.openDaniela, Frison; Concetta, Tino; Jonathan, W., Tyner; Monica, FedeliFrison, Daniela; Tino, Concetta; Jonathan, W.; Tyner, ; Fedeli, Monic

BLASFEO: basic linear algebra subroutines for embedded optimization

BLASFEO is a dense linear algebra library providing high-performance implementations of BLAS- and LAPACK-like routines for use in embedded optimization. A key difference with respect to existing high-performance implementations of BLAS is that the computational performance is optimized for small to medium scale matrices, i.e., for sizes up to a few hundred. BLASFEO comes with three different implementations: a high-performance implementation aiming at providing the highest performance for matrices fitting in cache, a reference implementation providing portability and embeddability and optimized for very small matrices, and a wrapper to standard BLAS and LAPACK providing high-performance on large matrices. The three implementations of BLASFEO together provide high-performance dense linear algebra routines for matrices ranging from very small to large. Compared to both open-source and proprietary highly-tuned BLAS libraries, for matrices of size up to about one hundred the high-performance implementation of BLASFEO is about 20-30% faster than the corresponding level 3 BLAS routines and 2-3 times faster than the corresponding LAPACK routines

Metal-histidine-glutamate as a regulator of enzymatic cycles: a case study of carbonic anhydrase.

International audienceHistidine is a very common metal ligand in metalloenzymes. Besides being an efficient Lewis base, its electronic properties are essential to shape the metal ability to catalyze the reaction. Here we show that histidine's properties can be tuned, in turn, by an easy proton transfer to a nearby glutamate. We study this situation in Human Carbonic Anhydrase II (HCA II) in which one of the three histidines bound to zinc (His119) interacts also with a glutamate residue (Glu117). Proton transfer from His119 to Glu117 has been hypothesized in the past, however realistic modeling is performed here for the first time. We show that the carboxylate group of Glu117 behaves only as a hydrogen bond acceptor in the hydroxy form of HCA II. On the other hand, our results suggest that Glu117 could exist either as a hydrogen bond acceptor or as a proton acceptor in the aqua form of HCA II, the two isomers having almost the same thermodynamic stability. We propose that this proton shift may be used by the enzyme to facilitate the final displacement of bicarbonate by water

A comparative study of semiempirical, ab initio, and DFT methods in evaluating metal-ligand bond strength, proton affinity, and interactions between first and second shell ligands in Zn-biomimetic complexes

International audienceAlthough theoretical methods are now available which give very accurate results, often comparable to the experimental ones, modeling chemical or biological interesting systems often requires less demanding and less accurate theoretical methods, mainly due to computer limitations. Therefore, it is crucial to know the precision of such less reliable methods for relevant models and data. This has been done in this work for small zinc-active site models including O- (H2O and OH-) and N-donor (NH3 and imidazole) ligands. Calculations using a number of quantum mechanical methods were carried out to determine their precision for geometries, coordination number relative stability, metal–ligand bond strengths, proton affinities, and interaction energies between first and second shell ligands. We have found that obtaining chemical accuracy can be as straightforward as HF geometry optimization with a double-f plus polarization basis followed by a B3LYP energy calculation with a triple-f quality basis set including diffuse and polarization functions. The use of levels as low as PM3 geometry optimization followed by a B3LYP single-point energy calculation with a double-tzeta quality basis including polarization functions already yields useful trends in bond length, proton affinities or bond dissociation energies, provided that appropriate caution is taken with the optimized structures. The reliability of these levels of calculation has been successfully demonstrated for real biomimetic cases