160 research outputs found
One-dimensional Cellular Automata in Quantum and Fermionic Theories
No full textThe thesis deals with quantum cellular automata (QCAs) and Fermionic quantum cellular automata (FQCAs) on one-dimensional lattices. With the term cellular automaton, we refer to a class of algorithms that can process information distributed on a regular grid in a local fashion. Its quantum counterpart—where at each site of the grid we can find a quantum system—represents a model for massive parallel quantum computation on finitely generated grids. The model is particularly well-suited for describing and simulating a vast class of physical phenomena.
The work presented in the thesis is threefold. We first introduce a new definition of QCA in terms of super maps, namely functions from quantum operations to quantum operations, that preserves locality and composition of transformations. Thereby, we define the so-called T-operator, i.e. a local operator that incorporates all the necessary information for univocally defining a QCA. The T-operator plays here the role of the Choi operator of the automaton.
Secondly, we classify all nearest-neighbor FQCAs over the one-dimensional lattice where each site contains one local Fermionic mode. We observe that the Fermionic automata are divided into two classes. In the first one, we find some FQCAs that are equivalent to a subset of quantum cellular automata. On the other hand, the second class of FQCAs has been found to have no quantum counterparts.
Finally, we report the experimental realization of a photonic platform to simulate the evolution of a one-dimensional quantum walk, i.e. a quantum cellular automaton whose action is linear in the field operators. Specifically, we observe the Zitterbewegung of a particle satisfying the Dirac dispersion relation. The theoretical background, numerical simulation, and optimization of the parameter space are discussed with special attention
La Convenzione europea dei Diritti dell'Uomo e la giurisprudenza della Corte di Strasburgo sulla libertà religiosa
No full textSr Curve for the Ain El Beida Section (Morocco): An Atlantic Perspective of the Mediterranean Salinity Crisis
No full textWe present a new 87Sr/86Sr curve for the time interval between 6.5 and 5.5 Ma of the Ain El Beida section (AEB, Atlantic side of Morocco). The location and the recessional-scale resolution of our curve allow to investigate the possible relationships between global paleoclimatic and palaeoceanographic trends and the high-amplitude hydrological changes of the Mediterranean during the Messinian salinity crisis (MSC). The values, obtained from planktic foraminifers, plot in the upper portion of the global ocean curve and show long- (at eccentricity scale) and short-term (precessional scale) oscillations; the latter are more evident during the maximum of eccentricity for both the 100 and 400 ka components, between 6.00 and 5.85 Ma. Negative 87Sr/86Sr anomalies are observed at insolation minima in phase with δ18O maxima, marking the glacial stages from TG34 to TG26. It is unclear whether these oscillations originated from local (river runoff) or global (glacial/interglacial) climatic forcing. Conversely, the evaporites of the coeval Primary Lower Gypsum (5.97–5.62 Ma) accumulated in the Mediterranean at insolation minima show positive anomalies at glacial stages TG32, 30, 28, and 26. Such an opposite trend is possibly related to the greater sensitivity of the Mediterranean Sea to river runoff during insolation maxima compared to the
global ocean, as recorded at the Moroccan Atlantic margin. These observations and the deviation toward lower values of the Mediterranean Sr isotope curve starting at around 6.5 Ma, support the hypothesis of a progressive restriction of the Atlantic connections since the early Messinian, leading to the MSC
Protein aggregation detection with fluorescent macromolecular and nanostructured probes: challenges and opportunities
No full textProtein aggregation is a phenomenon widespread in all organisms, that responds to a variety of external stimuli and is involved in complex functions such as storage and recycling of protein residues in crowded environments. In some cases, aggregation of proteins is related to serious human diseases. Understanding, monitoring and, eventually, intervening in the process of aggregation – in particular at its early stage – is a topic of high relevance and urgency. Recently, nanostructured materials have allowed for an unmet versatility and modularity in the field of sensing and inhibition of aggregation. Fluorescent oligomers and polymers, via controlled tuning of chemical functionalities, are yielding detailed comprehension of the interactions between probe candidates and protein aggregates; AIEgens are rapidly addressing many open challenges on sensitivity and signal enhancement; nanomaterials are increasingly serving as theranostic platforms, with multiple functionalities stemming from the assembly of components with complementary abilities. Here we review the most recent achievements in protein aggregation sensing based on macromolecular or nanostructured probes, highlighting the general experimental and computational findings that may serve as guidelines for the next generation of theranostic probes
In situ strontium isotope analysis on biogenic apatite: the use of Laser Ablation and Multi Collector Inductively Coupled Plasma Mass Spectrometer (LA–MC–ICPMS) in anthropological research
No full textThe use of LA–MC–ICPMS in anthropological research is an innovative approach for measuring strontium isotopic ratios of human enamel. This technique, due to its micro-destructivity, allows to exam 87Sr/86Sr on precious human remains, without the drawbacks of the dissolution method. Despite this advantage, the laser ablation technique (LA) is not without flaws, principally related to unavoidable analytical interferences. For these reasons, data obtained with the laser are usually less precise and accurate than data obtained with the classical dissolution method. In particular, problematic interferences are represented by 86Kr formed in the gas, by double-charged REE (Rare Earth Element), by 87Rb, and by other polyatomic isobaric interferences (i.e. 44Ca40Ar, 40Ca44Ca, 40Ca13P16O). In this work, we measured the Sr isotopic ratio of a shark tooth with both dissolution and LA method, to test the precision of the LA method. A shark tooth is a bio-apatite formed in a marine environment, thus its 87Sr/86Sr ratio reflects the modern marine ratio of ~0.7092. Our preliminary laser analyses show that we are able to reproduce the isotopic ratio of our shark tooth obtained by Sr chromatographic separation and HR–MC–ICPMS with a precision to the fourth decimal place and that this ratio reflects the modern sea water value. If confirmed by further studies, our preliminary results suggest that the LA technique is a reliable method to explore hominin movement and migrations
Hypermedia navigation: Differences between spatial cognitive styles
No full textRecently, many studies have investigated the role of individual and cognitive differences during Web navigation and Web searching. Despite this interest, no works have considered the role may assume individual differences in real-environment navigation during Web navigation. The aim of this work is to investigate the effect of different spatial cognitive styles: Landmark style (LS), Route style (RS) and Survey style (SS), on Web searching behaviour. In real-environment navigation, having a specific style determines the type of information individuals selected to navigate and orient themselves. We hypothesize that LS individuals are less proficient during Web exploration due to their analytical analysis of the environmental features. Vice versa SS individuals will show high performance on Web exploration for their holistic analysis of the World. We asked 30 College Students (10 LS, 10 RS, 10 SS) to solve three Web information tasks. The spatial cognitive style of participants was assessed through the Spatial Cognitive Style Test, and they were also asked to fill in a questionnaire about their internet and computer use. An ad hoc key-logger program for browsers was used to collect Web behaviour measures. In particular, the measures considered were: search engine tools used (e.g. back button), pages visited and revisited, time spent on information searching, and mouse cursor movements. The results showed significant differences between the spatial cognitive styles: LS seems to use a trial and error strategy in order to obtain the relevant information. Differences also emerged in the distribution of mouse cursor movements during Web navigation
Palaeoenvironmental setting and depositional model of upper Messinian microbialites of the Salento Peninsula (Southern Italy): A central Mediterranean Terminal Carbonate Complex
No full textThe Terminal Carbonate Complex (TCC) is an upper Messinian shallow-water succession characterized by abundant oolites deposits and microbial-derived carbonates mainly known from the Western Mediterranean. The importance of the TCC derives from the close relation of its deposition with the Messinian salinity crisis and from the presence of large and diversified microbialite assemblages, which represent a rare occurrence in the Cenozoic marine sedimentary record. In this paper we provide the first detailed description of a carbonate system closely comparable to the TCC located in the central Mediterranean. This succession crops out at the southern end of the Salento Platform (South-eastern Italy) and has been investigated by means of stratigraphic, sedimentary, palaeontological and Sr isotopes analyses. Special attention has been given to the microbialite facies, with a detailed textural characterization focused on the reconstruction of their depositional and palaeoenvironmental settings. The Salento Platform TCC mainly consists of oolites deposits, Porites colonization and a diversified microbialite assemblage including six different facies, which developed mostly under shallow-water, normal marine salinity and warm climatic conditions. The overall stacking pattern is given by the superposition of three main sequences, each one including lowstand, transgressive and highstand system tracts. The Salento Platform TCC is dated to the late Messinian; our microfacies and geochemical data suggest that it could have developed during the first stage of the MSC; these carbonates are in fact followed by a sharp unconformity sealed by thick breccia deposits, possibly related to the onset of the Messinian erosional surface and to the subsequent stages of the Messinian salinity crisis
Caratteristiche sedimentologiche dei depositi di ventaglio di rotta prodotti dal Fiume Secchia durante l’alluvione del 19 gennaio 2014
No full textLo studio sedimentologico dei depositi di ventaglio di rotta dell’alluvione del 19 gennaio 2014 presso
San Matteo (Modena) ha permesso di ottenere informazioni sull’evoluzione nel tempo e nello spazio
del sedimento fuoriuscito dall’alveo del Fiume Secchia in soli tre giorni. L’onda di piena ha allagato
la pianura verso nord-est creando un breve solco di erosione e un ventaglio di sabbie dallo spessore
massimo di circa 1 m. Il corpo sabbioso si è sviluppato fino ad una distanza dalla breccia di circa
600 m verso nord-est e 1,1 km verso est, dove la velocità della corrente si è mantenuta superiore
a 0,75 m/s. Nelle zone distali sono stati deposti limi argillosi (16-44% di argilla) fino a 5,4 km di
distanza presso Bastiglia, corrispondenti a velocità della corrente comprese tra 0,75 e 0,25 m/s. Le
sezioni stratigrafiche del corpo sabbioso presentano tre unità principali discontinue, dal basso verso
l’alto: 1) sabbia limosa poggiante direttamente sul terreno agricolo, fuoriuscita nella fase iniziale
dell’alluvione; 2) sabbie medie in discordanza erosiva contenenti abbondanti clasti di fango (16%)
costituiti da frammenti del terreno agricolo e dell’argine stesso prodotti dal progressivo allargamento
della breccia nell’argine; 3) sabbia media con una minore quantità di clasti fangosi (8%)
deposta all’inizio dei lavori di riparazione dell’argine.
Abstract
Sedimentological characteristics of the crevasse-splay deposits of the River Secchia flood of 19th
January 2014. The study of the R. Secchia flood of 19th January 2014 at San Matteo (Modena, Italy)
allows the evolution in time and space of the crevasse-splay deposits, which formed in just three days,
to be reconstructed. The flood propagated toward the north-east forming a small erosion surface
immediately downstream of the collapsed embankment and an irregular sand wedge with a maximum
thickness of about 1 m. The sand body covered an area of about 600 m toward the north-east and 1.1
km to the east, where the speed of the current was higher than 0.75 m/s. Laterally, a thin clayey silt
(16 to 44% of clay) layer was deposited up to 5.4 km away, in the area where the current speed
ranged between 0.75 and 0.25 m/s. The stratigraphic sections of the sand body show three main units,
from the bottom to the top: 1) a layer of silty sand resting directly above the soil, deposited during
the initial phase of the flood; 2) a medium sand layer containing abundant mud clasts (16%) which
are eroded fragments from the soil and the embankment produced by the progressive enlargement of
the breach; 3) a top sand layer with less abundant mud clasts (8%) deposited at the beginning of the
embankment repair works
Recupero, riuso e riqualificazione di un insieme di grandi servizi urbani dismessi. Recovery, reuse and technological re-qualification of a group of main disused urban services
No full textPhotonic cellular automaton simulation of relativistic quantum fields: Observation of Zitterbewegung
No full textQuantum cellular automaton (QCA) is a model for universal quantum computation and a natural candidate for digital quantum simulation of relativistic quantum fields. Here we introduce the first photonic platform for implementing QCA simulation of a free relativistic Dirac quantum field in 1+1 dimension, through a Dirac quantum cellular automaton (DQCA). Encoding the field position degree of freedom in the orbital angular momentum (OAM) of single photons, our state-of-the-art setup experimentally realizes eight steps of a DQCA, with the possibility of having complete control over the input OAM state preparation and the output measurement making use of two spatial light modulators. Therefore, studying the distribution in the OAM space at each step, we were able to reproduce the time evolution of the free Dirac field observing the Zitterbewegung, an oscillatory movement extremely difficult to see in a real-case experimental scenario that is a signature of the interference of particle and antiparticle states. The accordance between the expected and measured Zitterbewegung oscillations certifies the simulator performances, paving the way towards the application of photonic platforms to the simulation of more complex relativistic effects
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