87,357 research outputs found
Formaggio di malga trentino: ecologia microbica di un formaggio fermentato spontaneamente
No full textIl formaggio di Malga è uno dei prodotti più tipici della provincia trentina, ottenuto da latte crudo vaccino, esclusivamente nel periodo estivo, in malghe situate tra 1400 e 2000 m sul livello del mare. La malga è un sistema chiuso in cui le vacche pascolano, il latte viene prodotto e lavorato, il tutto nella stessa ambiente. Il latte viene processato a crudo esente da ogni tipo di addizione di starter e quindi le fermentazioni che si instaurano sono del tutto spontanee. L’obiettivo di questo lavoro è stato quello di caratterizzare i batteri lattici (LAB) autoctoni nelle prime fasi di produzione del formaggio di Malga e durante la stagionatura, in modo da correlare la microflora ai parametri tecnologici e le caratteristiche sensoriali. La produzione del formaggio è stata seguita per 36 giornate e sono stati prelevati campioni di latte di caldaia, cagliata, formaggio ad un giorno, un mese e sette mesi di stagionatura. È stata effettuata la conta di diversi generi microbici su terreni selettivi (PCA, M17, MRS, VRBA e KEA) incubati nelle condizioni ottimali. Tra i 614 ceppi isolati, 550 sono stati riconosciuti come LAB e caratterizzati genotipicamente combinando Randomly Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR), PCR specie-specifiche e sequenziamento parziale del gene 16S rRNA. La microflora dominante del latte risultava essere eterogenea e costituita da specie lattiche mesofile e non-lattiche psicrotrofe. Nel formaggio già dopo il primo giorno, i LAB diventavano dominanti: fino al primo mese di stagionatura, predominavano mesofili di forma coccica, identificati come Lactococcus lactis. Sono stati trovati anche Enterococcus faecalis e Streptococcus thermophilus. La carica delle popolazioni batteriche non lattiche dal primo giorno fino ai sette mesi di maturazione è diminuita in concomitanza con la diminuzione del pH. Dopo 7 mesi di stagionatura la microflora dominante del formaggio era costituita quasi esclusivamente da batteri lattici appartenenti principalmente alle specie Lactobacillus paracasei, Lactobacillus rhamnosus e Pediococcus pentosaceus
Authentication of satellite navigation signals by wiretap coding and artificial noise
No full textAbstract In order to combat the spoofing of global navigation satellite system (GNSS) signals, we propose a novel signal authentication method based on information-theoretic security. In particular, the satellite superimposes to the navigation signal an authentication signal containing a secret authentication message corrupted by artificial noise (AN). We impose the following properties: a)Authentication and navigation signals are synchronous,b)Authentication and navigation signals are orthogonal andc)The secret message is undecodable by the attacker due to the AN. The legitimate receiver synchronizes with the navigation signal and stores the samples of the authentication signal with the same synchronization. After the transmission of the authentication signal, through a separate public asynchronous ground channel (e.g., a secure Internet connection) additional information is made public allowing the receiver to a)Decode the authentication message, thus overcoming the effects of AN, andb)Verify the authentication message. We assess the performance of the proposed scheme by the analysis of both the secrecy capacity of the authentication message and the attack success probability under various attack scenarios
On Receiver Diversity for Grant-Free based Machine Type Communications
No full textGrant-free access schemes are steadily gaining momentum for emerging machine type communications and internet of things applications. Relying on variations of the classical ALOHA protocol to allow a vast population of users share a common channel in an uncoordinated fashion, these solutions have recently been embedded in international standards as well as proprietary commercial products. In this context, the use of multiple low-complexity receivers that act as relays, collecting packets from users and forwarding them towards a central unit represents an interesting approach to increase the efficiency of the system, which finds natural application in both terrestrial and non-terrestrial settings. To gain insights on the potential of such a configuration, this paper investigates a two-tier slotted ALOHA system under an erasure channel model. Closed form expressions for both end-to-end throughput and packet loss rate are derived for an arbitrary number of receivers, and the role of correlation among wireless channels connecting users to relays is thoroughly discussed. Non-trivial tradeoffs and systems design hints are highlighted, pinpointing some fundamental benefits and limitations of receiver diversity for grant-free based machine type communications
Evoluzione del profilo in acidi grassi insaturi durante la stagionatura del formaggio Pecorino DOP a latte pastorizzato.
No full textIl contributo riguarda lo studio del profilo in acidi grassi insaturi durante la maturazione del formaggio pecorino DO
Spatial GNSS Spoofing against Drone Swarms with Multiple Antennas and Wiener Filter
No full textSpoofing of global-navigation satellite system (GNSS) signals to induce a target position estimate is a relevant security threat to the navigation of drones. However, spoofing multiple drones simultaneously as they move in a swarm, without disrupting their formation, is a complex task. In this paper, we propose to transmit spoofing signals from the ground, such that the fake position can be estimated in any point of an area of the plane where the swarm is moving. To this end we filter the satellite-generated GNSS signals with a multidimensional linear filter, and transmit the filtered signal with multiple ground antennas. The multidimensional filter is designed according to a generalized Wiener-filter criterion, such that the fake signal is accurately reproduced (in terms of mean squared error (MSE)) in the whole spoofed area. We investigate the impact of various design parameters (among others, the size of the spoofed area, the number of ground antennas, and the number of spoofed satellites) on both the MSE, and the probability of acquisition of the spoofed signal by the drones
Formaggio: così genetica, tipo di allevamento e alimentazione influenzano l'aroma
No full textI composti organici volatili (VOC) contribuiscono a definire l’aroma del formaggio che è uno dei principali criteri di scelta da parte del consumatore. Recentemente abbiamo investigato il profilo aromatico di diverse tipologie di formaggi sia con tecniche gascromatografiche sia di spettrometria di massa (SPME/GC-MS e PTR-ToF-MS) per verificare la possibilità di utilizzare l’impronta aromatica come metodo di tracciabilità dei prodotti. In particolare, abbiamo considerato formaggi di diversa tipologia, provenienti da diverse aziende e alimentazioni e abbiamo studiato gli effetti delle caratteristiche produttive e della genetica delle vacche da latte sul loro profilo aromatico. Dai risultati emerge che l’aroma del formaggio è influenzato sia dalle caratteristiche produttive sia genetiche degli animali e può essere utilizzato come strumento di valorizzazione di prodotto o di processo produttivo
beta-Pseudopeptide foldamers. The homo-oligomers of (4R)-(2- oxo-1,3-oxazolidin-4-yl)-acetic acid (D-Oxac)
No full textA total synthesis in solution and a conformational analysis of the homo-oligomers of (4R)-(2-oxo-1,3-oxazolidin-4-yl)-acetic acid (D–Oxac) to the tetramer level are described. As the D–Oxac building block contains both an oxazolidin-2-one and a β-amino acid group, it may represent a new type of conformationally constrained tool for the construction of β-pseudopeptide foldamers. A conformational investigation using NMR and an extensive, unconstrained analysis with a Monte Carlo search to the octamer level, both in water and in chloroform, showed that these homo-oligomers tend to fold in a regular helical structure in a competitive solvent, such as water. Since aqueous solutions are of major relevance for biological systems, these molecules are good candidates for application to these environments
GNSS Spoofing Attack Detection By IMU Measurements Through A Neural Network
No full textSpoofing attacks against global navigation satellite system (GNSS) receivers are a serious threat to secure navigation, also in autonomous driving. Cars typically include, beyond the GNSS receiver, also an inertial measurement unit (IMU), whose data can be used to detect GNSS spoofing attacks. We consider a specific spoofing attack, with the spoofed trajectory that gradually diverges from the true trajectory, and we propose a spoofing detection method based on machine learning. First, a feature vector is designed, collecting the difference of two estimates of the device velocity, obtained from the GNSS receiver and the IMU. Then, a neural network (NN) is trained over a set of true and spoofed trajectories to detect the attack. We compare the proposed solution with an approximated Neyman-Pearson test and a literature reference direct comparison method, confirming the low error probabilities of our novel solution
Peptide-Based Biopesticides
No full textIn this presentation we describe the great potential of peptides as biopesticides. Currently Europe is greatly encouraging research in sustainable pest-management. Finding eco-friendly, effective alternatives to synthetic pesticides is of paramount importance, especially against the so-called priority pests of fruits and vegetables. For some of these pests, such as botrytis cinerea and peronospora viticola, no effective bio-alternatives to small organic molecules are available so far. Fungi belonging to the genus Trichoderma are distributed worldwide and have been used successfully in field trials against many crop pathogens. They produce peptaibols, a peculiar family of peptides, as part of their defense system against other microorganisms. Such secondary metabolites are known for their plantprotection properties: they (i) possess antimicrobial activity, (ii) act as stimulants of plant defences and growth (iii) elicit plant production of volatiles to attract natural enemies of herbivorous insects. By means of a versatile SPPS strategy, we produced several analogs of such naturally occurring peptides. With such compounds, we can circumvent both the health hazards and the unreliable effectiveness in open field connected with the use of antagonistic microorganisms as biological control agents, while keeping the biomolecules responsible for their beneficial effects. Our peptides have been tested (alone or in combination) both in vitro and in vivo against a variety of priority pests, such as the fungi Botrytis cinerea and Penicillum italicum, and the bacterium Pectobacterium carotovorum. We identified several peptaibol analogs with a broad-spectrum activity as biopesticides, able to completely inhibit the growth of B. cinerea and many other pathogens for over a week at low micromolar concentrations
Probing structural requirements of fMLP receptor: on the size of the hydrophobic pocket corresponding to residue 2 of the tripeptide
No full textThe conformationally constrained f-L-Met-Ac(n)c-L-Phe-OMe (n = 4,9-12) tripeptides, analogues of the chemoattractant f-L-Met-L-Leu-L-Phe-OH, were synthesized in solution by classical methods and fully characterized, These compounds and the published f-L-Met-Xxx-L-Phe-OMe (Xxx = Aib and Ac(n)c where n = 3, 5-8) analogues were compared to determine the combined effect of backbone preferred conformation and side-chain bulkiness at position 2 on the relation of 3D-structure to biological activity. A conformational study of all the analogues was performed in solution by FT-IR absorption and H-1-NMR techniques. In parallel, each peptide was tested for its ability to induce chemotaxis, superoxide anion production and lysozyme secretion from human neutrophils. The biological and conformational data are discussed in relation to the proposed model of the chemotactic receptor on neutrophils, in particular of the hydrophobic pocket accommodating residue 2 of the tripeptide
- …
