The Cameron-Liebler problem for sets

Cameron-Liebler line classes and Cameron-Liebler k-classes in PG(2k+1,q) are currently receiving a lot of attention. Links with the Erd\H{o}s-Ko-Rado results in finite projective spaces occurred. We introduce here in this article the similar problem on Cameron-Liebler classes of sets, and solve this problem completely, by making links to the classical Erd\H{o}s-Ko-Rado result on sets. We also present a characterisation theorem for the Cameron-Liebler classes of sets

Partially Isometric Immersions and Free Maps

In this paper we investigate the existence of ``partially'' isometric immersions. These are maps f:M->R^q which, for a given Riemannian manifold M, are isometries on some sub-bundle H of TM. The concept of free maps, which is essential in the Nash--Gromov theory of isometric immersions, is replaced here by that of H-free maps, i.e. maps whose restriction to H is free. We prove, under suitable conditions on the dimension q of the Euclidean space, that H-free maps are generic and we provide, for the smallest possible value of q, explicit expressions for H-free maps in the following three settings: 1-dimensional distributions in R^2, Lagrangian distributions of completely integrable systems, Hamiltonian distributions of a particular kind of Poisson Bracket.Comment: 19 pages, 1 figur

Anatomia funzionale del Default Mode Network: studio della connettività funzionale in fMRI

Il Default-Mode Network (DMN) è una rete di aree cerebrali maggiormente attive durante il riposo (resting) che vanno incontro a calo dell'attività (deattivazione) quando il cervello è chiamato a eseguire dei compiti. Queste aree svolgerebbero quindi una "attività di fondo" destinata ad un lavoro mentale principalmente introspettivo e di elaborazione di piani, progetti e azioni. In questa tesi si vuole esaminare la relazione esistente tra l'attività a riposo e la rete di working memory (WM), che invece ha lo scopo di gestire informazioni sensoriali ed utilizzarle rapidamente per ottenere una risposta immediata. Molti studi hanno verificato l'esistenza di una relazione inversa tra le attività di DMN e WM: ad un aumento dell'attività di un sistema corrisponde un calo dell'attività dell'altro. Un altro aspetto che si vuole esaminare è la dipendenza di questa interazione dal carico di lavoro che la WM deve svolgere. Per questo gli esperimenti di Risonanza Magnetica Funzionale (fMRI) sono stati eseguiti sfruttando un task con vari livelli di difficoltà e di impegno per le aree collegate alla WM. I dati sono stati acquisiti mediante uno scanner fMRI presso il Dipartimento di Neuroscienze Cognitive della facoltà di Psicologia e Neuroscienze dell'Università di Maastricht. L'analisi dei dati successiva all'acquisizione è stata finalizzata a studiare la connettività funzionale, cioè la correlazione temporale tra due eventi neurofisiologici che si verifica in modo indipendente dalla connessione anatomica tra le aree ad essi collegate, per ottenere dei dati di base che confermino la validità del paradigma sperimentale. Abstract The Default-Mode Network (DMN) is a network of brain areas which are more active during resting states. They undergo a decrease in activity when the brain is involved in tasks. These areas may be involved in a wide range of spontaneous, self-oriented activities and thoughts, like envisioning the future, thinking about past or planning future actions. This thesis aims to examine the relationship between this default activity and the working memory network, which is instead involved in the management of sensory information, processed and rapidly used to obtain immediate responses. Many studies have assessed the existence of an inverse relationship between the activities in DMN and WM: an increase in the former's activity is related to a decrease in the latter's. A further feature we intended to examine is the dependence of this DMN-WM relationship on the amount of work that the WM network is called to do. For this reason the fMRI experiments were conducted using a multi-load task, which stimulated WM to different extents. The reported data were acquired using a fMRI scanner at the Department of Cognitive Neuroscience of the Faculty of Psychology and Neurosciences at Maastricht University. The data analysis following acquisition aimed to study the functional connectivity, i.e. the temporal correlation between two neurophysiological events which undergoes independently from their anatomical connections

Near-infrared photometry of the young open clusters NGC 1893 and Berkeley 86

We present photometry in the J and K near-infrared bands for two regions centered on the young open clusters NGC 1893 and Berkeley 86. We study 700 stars down to K = 17 in the field of NGC 1893, and about 2000 stars in the field of Berkeley 86 down to K$\sim$ 16.5, for which near-infrared photometry was insofar not available. Coupling J-K data with UBV photometry taken from literature, we produce reddening corrected colour-magnitude diagrams. We find that our data are consistent with previous determinations: the clusters are roughly coeval with an age between 4 and 6 million years. The mean reddening (measured as E(J-K)) values turn out to be 0.35 and 0.50 for NGC 1893 and Berkeley 86, respectively.Using colour-colour plots we discuss the presence of candidate pre-main sequence stars showing infrared excess. Candidates are found in both cluster regions, confirming the young age of these clusters.Comment: 9 pages, 12 figures, Astronomy & Astrophysics Main Journal Accepte

Elimination of Salmonella cross-contamination on eggs using antimicrobial coating

Gastro-intestinal infections caused by Salmonella strains, together with Campylobacter, are among the most common food-borne diseases in Italy (EFSA journal 2016). Therefore, it is important to avoid the spreading of bacterial colonization on different type of foods. A common vector of Salmonella are eggs, which can be contaminated by the laying hen (vertical or horizontal infection) or by contact with contaminated eggs of food (cross-contamination). At the moment, the Italian prevention practices to control Salmonella spreading are bacterial controls on laying hens and their environment and eggs brushing before packaging. Other countries allow eggs washing, but this process decreases the shelf-life of the product. This study investigates the efficiency of an antimicrobial coating to avoid Salmonella cross-contamination on eggs. Coating the eggs with a pectin-alginate polymer drastically improves their food safety and reduces the recovery of Salmonella colonies from the egg surface. Therefore, the occurrence of cross-contamination would be highly reduced as well. The positive effect of the coating itself showed to be highly effective even without the addition of antibacterial agents such as LAE. This active packaging could guarantee higher safety for eggs and opens the possibility to test this procedure on other food matrices common carriers of potentially pathogenic bacteria

Evaluation of the antimicrobial activity of a blend of monoglycerides against Escherichia coli and Enterococci with multiple drug resistance

Bacterial antibiotic resistance is a natural phenomenon, seriously affecting the treatment of infections. The biggest danger is that current antibiotics are not able to eradicate the resistant strains. In recent years, alternative antibacterial substances are being sought, which can help in these cases. Fatty acids and monoglycerides are known among the natural substances for their antimicrobial properties and, important detail, bacteria do not develop resistance to them. In this work, we studied the antimicrobial effects of a monoglyceride blend against some multi-resistant Enterococci and Escherichia coli strains. Based on literature data, a blend of fatty acids and their monoglycerides was created and its antimicrobial activity was evaluated against 37 strains of E. coli and 17 Enterococci presenting resistance to at least two antibiotics. A different behavior was observed in the two groups of bacteria, proving that alternative substances can be considerate for the potential treatment of multidrug-resistant strains