ED-XRF analysis for Cultural Heritage: Is quantitative evaluation always essential?

Energy Dispersive X-Ray Fluorescence (ED-XRF) is a very suitable tool for examination of Cultural Heritage materials because of its simplicity, with no requirement for any sample preparation and the possibility of operating with portable instruments, and it can probably be considered the most useful non-destructive analytical technique for ancient valuable objects of archaeological, historical or artistic interest. As regards the possibility of getting quantitative analysis in archaeometric applications, the problems arising from the limited sensitivity in detecting low Z elements, the irregular shape or the non-homogeneous composition of the sample have generated a widespread opinion that only semi-quantitative analyses are possible in XRF applications to archaeometry. In fact, this is always true for non-homogeneous samples as, typically, painting layers. On the contrary, the problems deriving from limited sensitivity in detecting matrix light elements as well as from irregular surface under analysis can be solved in most cases. Notwithstanding, working on unique and not standardized objects requires to pay attention on details and to know how to choose correct parameters and calculation algorithms to obtain reliable results. Indeed opportunities to deal with these objects are very limited and results have implication in other fields, so that each information about materials and production technique is of great interest. Two typical materials of archaeological interest showing particular features are considered - namely high corroded metallic artefacts and ceramics - revealing that, even if in cultural heritage field detailed quantitative analysis is the goal, it is not always necessary as also qualitative information by XRF spectra increase the knowledge of artefact

Looking for common fingerprints in Leonardo’s pupils through nondestructive pigment characterization

Non-invasive, portable analytical techniques are becoming increasingly widespread for the study and conservation in the field of cultural heritage, proving that a good data handling, supported by a deep knowledge of the techniques themselves, and the right synergy can give surprisingly substantial results when using portable but reliable instrumentation. In this work, pigment characterization was carried out on 21 Leonardesque paintings applying in situ X-ray fluorescence (XRF) and fiber optic reflection spectroscopy (FORS) analyses. In-depth data evaluation allowed to get information on the color palette and the painting technique of the different artists and workshops . Particular attention was paid to green pigments (for which a deeper study of possible pigments and alterations was performed with FORS analyses), flesh tones (for which a comparison with available data from cross-sections was made), and ground preparation

On the Complexity of tt-Closeness Anonymization and Related Problems

An important issue in releasing individual data is to protect the sensitive information from being leaked and maliciously utilized. Famous privacy preserving principles that aim to ensure both data privacy and data integrity, such as $k$-anonymity and $l$-diversity, have been extensively studied both theoretically and empirically. Nonetheless, these widely-adopted principles are still insufficient to prevent attribute disclosure if the attacker has partial knowledge about the overall sensitive data distribution. The $t$-closeness principle has been proposed to fix this, which also has the benefit of supporting numerical sensitive attributes. However, in contrast to $k$-anonymity and $l$-diversity, the theoretical aspect of $t$-closeness has not been well investigated. We initiate the first systematic theoretical study on the $t$-closeness principle under the commonly-used attribute suppression model. We prove that for every constant $t$ such that $0\leq t<1$, it is NP-hard to find an optimal $t$-closeness generalization of a given table. The proof consists of several reductions each of which works for different values of $t$, which together cover the full range. To complement this negative result, we also provide exact and fixed-parameter algorithms. Finally, we answer some open questions regarding the complexity of $k$-anonymity and $l$-diversity left in the literature.Comment: An extended abstract to appear in DASFAA 201

Parameterized Complexity of the k-anonymity Problem

The problem of publishing personal data without giving up privacy is becoming increasingly important. An interesting formalization that has been recently proposed is the $k$-anonymity. This approach requires that the rows of a table are partitioned in clusters of size at least $k$ and that all the rows in a cluster become the same tuple, after the suppression of some entries. The natural optimization problem, where the goal is to minimize the number of suppressed entries, is known to be APX-hard even when the records values are over a binary alphabet and $k=3$, and when the records have length at most 8 and $k=4$ . In this paper we study how the complexity of the problem is influenced by different parameters. In this paper we follow this direction of research, first showing that the problem is W[1]-hard when parameterized by the size of the solution (and the value $k$). Then we exhibit a fixed parameter algorithm, when the problem is parameterized by the size of the alphabet and the number of columns. Finally, we investigate the computational (and approximation) complexity of the $k$-anonymity problem, when restricting the instance to records having length bounded by 3 and $k=3$. We show that such a restriction is APX-hard.Comment: 22 pages, 2 figure

Approximating Clustering of Fingerprint Vectors with Missing Values

The problem of clustering fingerprint vectors is an interesting problem in Computational Biology that has been proposed in (Figureroa et al. 2004). In this paper we show some improvements in closing the gaps between the known lower bounds and upper bounds on the approximability of some variants of the biological problem. Namely we are able to prove that the problem is APX-hard even when each fingerprint contains only two unknown position. Moreover we have studied some variants of the orginal problem, and we give two 2-approximation algorithm for the IECMV and OECMV problems when the number of unknown entries for each vector is at most a constant.Comment: 13 pages, 4 figure

Coherent coupling between Vanadyl Phthalocyanine spin ensemble and microwave photons: Towards integration of molecular spin qubits into quantum circuits

Electron spins are ideal two-level systems that may couple with microwave photons so that, under specific conditions, coherent spin-photon states can be realized. This represents a fundamental step for the transfer and the manipulation of quantum information. Along with spin impurities in solids, molecular spins in concentrated phases have recently shown coherent dynamics under microwave stimuli. Here we show that it is possible to obtain high cooperativity regime between a molecular Vanadyl Phthalocyanine (VOPc) spin ensemble and a high quality factor superconducting YBa2Cu3O7 (YBCO) coplanar resonator at 0.5 K. This demonstrates that molecular spin centers can be successfully integrated in hybrid quantum devices

Flash Thermography Mapping of Degradation Patterns in Archaeological Glass

The process of degradation in artefacts subjected to centuries of burial can be of great relevance above all in archaeological glass. Infrared thermography is a non-destructive method allowing to map the defects of the glass substrate, both produced during its manufacturing (e.g., bubbles and inclusions) and due to ageing. This research is focused on the use of different flash thermography methods for the mapping of superficial flakes on Roman glasses dating back to the I and II century A.D. The effectiveness of active thermography methods is evaluated to map degraded portions of archaeological glass considering their semitransparency and specific optical absorption

New perspectives on an “old” technique: Lipari obsidian and Neolithic communities investigated by Fission Track Dating

“Lipari obsidian and Neolithic human communities in the Aeolian islands” is a project aimed at studying the connection between obsidian flows on the island of Lipari and Neolithic populations on the Aeolian archipelago, in Italy. As it is well known, obsidian is of particular interest to trace prehistorical trading patterns; indeed, Lipari obsidian has the widest distribution and has been found in southern France, Dalmazia, Sicily and mainland Italy. The project outputs will give a general vision of both archaeological and volcanological aspects through thestratigraphic and radiometric dating of eruptions which produced obsidian, in relationship with the first phases of the human settlements and row material exploitation. To reach this goal, we are considering both raw materials (geological samples) from different flows and artifacts from Neolithic settlements (archaeological samples) on the Aeolian islands, and performing fission track dating to get the age of obsidian sources and artefacts. Obtained results are expected to shed some new light on the raw material procurement and on the ability of the Neolithic populations to move from their locations, with particular attention to the consequences of environmental features on the first human settlements on the Aeolian islands

Coherently coupling distinct spin ensembles through a high-Tc superconducting resonator

The problem of coupling multiple spin ensembles through cavity photons is revisited by using (3,5-dichloro-4- pyridyl)bis(2,4,6-trichlorophenyl) methyl (PyBTM) organic radicals and a high-T-c superconducting coplanar resonator. An exceptionally strong coupling is obtained and up to three spin ensembles are simultaneously coupled. The ensembles are made physically distinguishable by chemically varying the g factor and by exploiting the inhomogeneities of the applied magnetic field. The coherent mixing of the spin and field modes is demonstrated by the observed multiple anticrossing, along with the simulations performed within the input-output formalism, and quantified by suitable entropic measures

Storage and retrieval of microwave pulses with molecular spin ensembles

Abstract Hybrid architectures combining complementary quantum systems will be largely used in quantum technologies and the integration of different components is one of the key issues. Thanks to their long coherence times and the easy manipulation with microwave pulses, electron spins hold a potential for the realization of quantum memories. Here, we test diluted oxovanadium tetraphenyl porphyrin (VO(TPP)) as a prototypical molecular spin system for the Storage/Retrieval of microwave pulses when embedded into planar superconducting microwave resonators. We first investigate the efficiency of several pulse sequences in addressing the spins. The Carr-Purcell and the Uhrig Dynamical Decoupling enhance the memory time up to three times with three π pulses. We then successfully store and retrieve trains of up to 5 small pulses by using a single recovery pulse. These results demonstrate the memory capabilities of molecular spin ensembles when embedded into quantum circuits