Native NIR-emitting single colour centres in CVD diamond

Single-photon sources are a fundamental element for developing quantum technologies, and sources based on colour centres in diamonds are among the most promising candidates. The well-known NV centres are characterized by several limitations, thus few other defects have recently been considered. In the present work, we characterize in detail native efficient single colour centres emitting in the near infra-red in both standard IIa single-crystal and electronic-grade polycrystalline commercial CVD diamond samples. In the former case, a high-temperature annealing process in vacuum is necessary to induce the formation/activation of luminescent centres with good emission properties, while in the latter case the annealing process has marginal beneficial effects on the number and performances of native centres in commercially available samples. Although displaying significant variability in several photo physical properties (emission wavelength, emission rate instabilities, saturation behaviours), these centres generally display appealing photophysical properties for applications as single photon sources: short lifetimes, high emission rates and strongly polarized light. The native centres are tentatively attributed to impurities incorporated in the diamond crystal during the CVD growth of high-quality type IIa samples, and offer promising perspectives in diamond-based photonics.Comment: 27 pages, 10 figures. Submitted to "New Journal of Phsyics", NJP-100003.R

A quantum logical and geometrical approach to the study of improper mixtures

We study improper mixtures from a quantum logical and geometrical point of view. Taking into account the fact that improper mixtures do not admit an ignorance interpretation and must be considered as states in their own right, we do not follow the standard approach which considers improper mixtures as measures over the algebra of projections. Instead of it, we use the convex set of states in order to construct a new lattice whose atoms are all physical states: pure states and improper mixtures. This is done in order to overcome one of the problems which appear in the standard quantum logical formalism, namely, that for a subsystem of a larger system in an entangled state, the conjunction of all actual properties of the subsystem does not yield its actual state. In fact, its state is an improper mixture and cannot be represented in the von Neumann lattice as a minimal property which determines all other properties as is the case for pure states or classical systems. The new lattice also contains all propositions of the von Neumann lattice. We argue that this extension expresses in an algebraic form the fact that -alike the classical case- quantum interactions produce non trivial correlations between the systems. Finally, we study the maps which can be defined between the extended lattice of a compound system and the lattices of its subsystems.Comment: submitted to the Journal of Mathematical Physic

Evidence of light guiding in ion-implanted diamond

We demonstrate the feasibility of fabricating light-waveguiding microstructures in bulk single-crystal diamond by means of direct ion implantation with a scanning microbeam, resulting in the modulation of the refractive index of the ion-beam damaged crystal. Direct evidence of waveguiding through such buried microchannels is obtained with a phase-shift micro-interferometric method allowing the study of the multimodal structure of the propagating electromagnetic field. The possibility of defining optical and photonic structures by direct ion writing opens a range of new possibilities in the design of quantumoptical devices in bulk single-crystal diamond

Exploiting the interplay between cross-sectional and longitudinal data in Class III malocclusion patients

The aim of the study was to investigate how to improve the forecasting of craniofacial unbalance risk during growth among patients affected by Class III malocclusion. To this purpose we used computational methodologies such as Transductive Learning (TL), Boosting (B), and Feature Engineering (FE) instead of the traditional statistical analysis based on Classification trees and logistic models. Such techniques have been applied to cephalometric data from 728 cross-sectional untreated Class III subjects (6–14 years of age) and from 91 untreated Class III subjects followed longitudinally during the growth process. A cephalometric analysis comprising 11 variables has also been performed. The subjects followed longitudinally were divided into two subgroups: favourable and unfavourable growth, in comparison with normal craniofacial growth. With respect to traditional statistical predictive analytics, TL increased the accuracy in identifying subjects at risk of unfavourable growth. TL algorithm was useful in diffusion of information from longitudinal to cross-sectional subjects. The accuracy in identifying high-risk subjects to growth worsening increased from 63% to 78%. Finally, a further increase in identification accuracy, up to 83%, was produced by FE. A ranking of important variables in identifying subjects at risk of growth worsening, therefore, has been obtained

Micro-beam and pulsed laser beam techniques for the micro-fabrication of diamond surface and bulk structures

Micro-fabrication in diamond is involved in a wide set of emerging technologies, exploiting the exceptional characteristics of diamond for application in bio-physics, photonics, radiation detection. Micro ion-beam irradiation and pulsed laser irradiation are complementary techniques, which permit the implementation of complex geometries, by modification and functionalization of surface and/or bulk material, modifying the optical, electrical and mechanical characteristics of the material. In this article we summarize the work done in Florence (Italy) concerning ion beam and pulsed laser beam micro-fabrication in diamond.Comment: 14 pages, 5 figure

Peptide-Tetrapyrrole Supramolecular Self-Assemblies: State of the Art.

The covalent and noncovalent association of self-assembling peptides and tetrapyrroles was explored as a way to generate systems that mimic Nature's functional supramolecular structures. Different types of peptides spontaneously assemble with porphyrins, phthalocyanines, or corroles to give long-range ordered architectures, whose structure is determined by the features of both components. The regular morphology and ordered molecular arrangement of these systems enhance the photochemical properties of embedded chromophores, allowing applications as photo-catalysts, antennas for dye-sensitized solar cells, biosensors, and agents for light-triggered therapies. Chemical modifications of peptide and tetrapyrrole structures and control over the assembly process can steer the organization and influence the properties of the resulting system. Here we provide a review of the field, focusing on the assemblies obtained from different classes of self-assembling peptides with tetrapyrroles, their morphologies and their applications as innovative functional materials

Bone-Anchored Hearing Aids Fitted According to NAL and DSL Procedures in Adults with Mixed Hearing Loss

BACKGROUND: Bone-anchored hearing aids represent a valid alternative for patients with conductive/mixed hearing loss who cannot use hearing aids. To date, these devices have given good audiological results, thanks to various fitting prescription programs (i.e., National Acoustic Laboratories and Desired Sensation Level). The aim of this study is to compare 2 types of fitting algorithms (National Acoustic Laboratories and Desired Sensation Level) implemented for bone-anchored hearing devices. METHODS: We retrospectively enrolled 10 patients followed at our operative unit, suffering from bilateral symmetrical mixed hearing loss and who underwent bone-anchored hearing aid implantation. All patients experienced each prescriptive procedure, National Acoustic Laboratories and Desired Sensation Level, for 7 months (on average), and they were subjected to audiological tests and questionnaires to evaluate the best program. RESULTS: National Acoustic Laboratories and Desired Sensation Level prescriptions yielded similar results. Desired Sensation Level allowed less amplification of the low frequencies than the National Acoustic Laboratories prescription, and these differences were the only statistically significant. Desired Sensation Level allowed better disyllabic word and sentence recognition scores only in quiet and not in noisy conditions. The subjective questionnaires showed similar results. At the end of the trial sessions, more patients (60%) definitively chose the Desired Sensation Level program for their device. These patients were those with a worse hearing threshold. CONCLUSION: The 2 prescriptive programs allowed similar results although patients with a worse threshold seem to prefer the DSL program. This is the first evaluation of the 2 prescriptive programs, National Acoustic Laboratories versus Desired Sensation Level, for bone conduction devices available in the literature. Further studies are needed to confirm this initial finding

The importance of being little: MA-XRF on manuscripts on a Venetian island

The XRF scanning spectrometer developed in the framework of CHNet-INFN (Cultural Heritage Network - National Institute of Nuclear Physics), is specifically customised for cultural heritage applications, designed with a focus on having a lightweight scanner (weighing approximately 10 kg), easy to handle and thus easily transportable in two medium-sized boxes. The research presented here deals with the study of a set of choir books preserved in the Abbey of San Giorgio Maggiore on the homonymous island in Venice. Produced for the Abbey itself from the mid-15th century onwards, the manuscripts have never left the island, making the study of the materials of particular interest as they have undergone little or no modification over time. During their history in the Abbey, however, the volumes have been disassembled and reassembled in various ways, bringing complexity to the current cataloguing work. Thus, analytical investigations of the pigments and painting techniques might help identify the original arrangement of displaced leaves and provide evidence for the attribution of individual illuminations to certain artists. Thanks to its easy transportability, it was possible to take the scanner to the small island by means of the water-based Venetian public transport. Selected results are presented, derived from the high-quality MA-XRF maps obtained