2024
Francesca Borghi, Thierry Ralph Nieus, Davide E Galli, Paolo Milani
https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2024.1465789/full
Giacomo Nadalini, Alexander Dallinger, Davide Sottocorno, Francesco Greco, Francesca Borghi, Paolo Milani
https://advanced.onlinelibrary.wiley.com/doi/full/10.1002/aelm.202400717
Mirko Maturi, Lorenzo Migliorini, Sara Moon Villa, Tommaso Santaniello, Natalia Fernandez-Delgado, Sergio Ignacio Molina, Paolo Milani, Alberto Sanz de León, Mauro Comes Franchini
This work describes the development and characterization of tetragonal barium titanate nanoparticles (BTO NPs) and their surface functionalization with dopamine dodecylamine (DDA), a lipophilic organic ligand. The so-obtained lipophilic NPs (BTO-DDA) are then formulated at low loadings (< 5 wt.%) into liquid photocurable resins for vat photopolymerization (VP) and 3D printed into solid objects. The printed composites are mechanically characterized in order to assess the effect of the nanomaterial on the mechanical properties of the 3D printed polymer, revealing no significant variations in the mechanical properties (tensile or flexural) of the nanocomposites compared to the original polymer matrix. In light of these results, the printed nanocomposites are studied in terms of their capacity to generate a separation of charge by the piezoelectric effect, typical of the BTO crystal structure. This study reveals that BTO-loaded nanocomposites display outstanding piezoelectric coefficients as high as 50 pC/N when BTO-DDA is formulated at 3.0 wt.%, only slightly less than one-third of the piezoelectric coefficient previously reported for bulk BTO, while preserving the mechanical properties of the polymer matrix.
https://onlinelibrary.wiley.com/doi/full/10.1002/adfm.202407077
Migliorini, L., Valaperta, G., Acocella, F., Santaniello, T., Castelli, N., Perin, A., Cavaliere, F., Vertemati, M., Zuccotti, G.V. and Milani, P., 2024. Conductive Gel Phantoms for Training in Electrosurgery. Advanced Materials Interfaces, p.2400246.
https://onlinelibrary.wiley.com/doi/full/10.1002/admi.202400246
Davide Cipollini, Filippo Profumo, Lambert Schomaker, Paolo Milani, Francesca Borghi
https://www.frontiersin.org/articles/10.3389/fmats.2024.1385792/full
G. Martini, E. Tentori, M. Mirigliano, D. E. Galli, P. Milani and F. Mambretti
https://www.frontiersin.org/articles/10.3389/fphy.2024.1400919/full
Migliorini, L., Santaniello, T. and Milani, P., Printing Electrically Conductive Patterns on Polymeric and 3D-Printed Systems. In Resilient Hybrid Electronics for Extreme/Harsh Environments (pp. 93-113). CRC Press.
Zixin Huo, Wenjie Yang, Javad Harati, Ajinkya Nene, Francesca Borghi, Claudio Piazzoni, Paolo Milani, Shifeng Guo, Massimiliano Galluzzi, Diana Boraschi
Stefano Radice, Filippo Profumo, Francesca Borghi, Andrea Falqui, Paolo Milani
https://onlinelibrary.wiley.com/doi/full/10.1002/aelm.202400434
Tommaso Pajola, Anika Padin, Benjamin Blowers, Francesca Borghi, Alessandro Minguzzi, Emiliano Bonera, Alberto Vertova, Marcel Di Vece
https://chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/cphc.202400594
M. Siano, B. Paroli, S. Cialdi, S. Olivares, M. Paris, E. Suerra, M. Potenza.
In this work we experimentally demonstrate high sensitive strictly-local identification of azimuthal index of Laguerre–Gauss (LG) beams, with less than 160 photon counts. To this aim, detection of the azimuthal index of LG beams is performed with an innovative interferometer relying on a monolithic birefringent crystal, thus ensuring stability without the need of any feedback or thermal drift compensation. By first generating a reference interference pattern with a standard TEM00 mode, we then detect the value of the azimuthal index of a LG beam from the lateral shift of the pattern with respect to the reference one. An experimental setup has been realized to prove the effectiveness of the proposed scheme, which requires to access only a small portion (5%) of the entire wavefront. Moreover, being intrinsically endowed with extreme robustness and stability, we achieve effective high sensitive detection of the azimuthal index by collecting less than 160 photons only, while at the same time keeping the local features. Limitations and possible applications are also discussed.
https://dx.doi.org/10.1016/j.optcom.2024.130349
L. Teruzzi, L. Cremonesi, M.A.C. Potenza
Instruments based on light obscuration sensors are widely used for measuring the size distribution of insoluble sub-visible particles in liquid suspensions, being fast and suitable for in situ and real-time measurements. Such instruments are typically calibrated by means of reference polystyrene spherical particles with a specific refractive index, which unavoidably leads to systematic errors when determining the size of particles of different materials. In this paper, we propose a reliable and consistent method to overcome this limitation by setting the refractive index value according to the sample, thus achieving an improved particle size distribution (PSD) measurement. An ad hoc, ready-to-use, open source code with a graphical interface able to drive an in-line instrument and obtain a real-time correction to the PSD has been developed. The method has been extensively validated with several oil emulsions characterized by different refractive index values and the results have been compared with an independent optical method. As an example of application, we have adopted this approach for the analysis of dust suspended in meltwater of an ice core from a glacier in the Aosta Valley (Italy). We believe that our approach will strongly improve the accuracy in characterizing liquid suspensions and reduce discrepancies between data obtained with different methods. The code has been made publicly available at: https://instrumentaloptics.fisica.unimi.it/dedalo/ and on the GitHub page of the corresponding author (https://github.com/LucaTeruzzi/DEDALO).
S. Cialdi, E. Suerra, S. Altilia, S. Olivares, B. Paroli, M. Potenza, M. Siano, M. Paris
In this paper, we address the use of a calcite crystal-based local detector for the discrimination of the orbital angular momentum of quantum radiation produced by parametric down-conversion, using only a portion of the beam. Specifically, we propose and experimentally demonstrate that discrimination can be achieved by exploiting the introduction of a precise and controlled spatial shift between two replicas of the state within the crystals. This approach utilizes a robust and intrinsically stable monolithic configuration, obviating the need for feedback mechanisms or thermal drift compensation. Our method offers a promising avenue for enhancing the reliability and efficiency of quantum communication systems, and we believe that this technology could significantly advance the development of quantum communication techniques, where information encoding is based on orbital angular momentum, or spatially distributed orbital angular momentum detection.
M. Pallavera, T. Sanvito, L. Cremonesi, C. Artoni, A. Falqui, M.A.C. Potenza
A growing body of literature is raising concerns about the spread of nano- and microplastics and the hazards they pose to the environment and on human health. There is still a limited understanding of their sources and formation mechanisms, making their release and uptake difficult to track and quantify. Among the obstacles to the progress in this field there is the lack of reliable methods for quantitative studies, leading to a potential underestimation of the extent of their release and the related risks. In this paper, the application of an optical method for studying the release of sub-micrometric plastics in water by polypropylene containers certified for alimentary use is described. The results show evidence of negligible release when the temperature of the water is kept below the manufacturer’s specifications, whereas a rampant increase occurs beyond these conditions, irrespective of the thermal history of the sample. Particles with a diameter distribution that spans one order of magnitude are observed, ranging from ≈200 nm to 2 µm, and their refractive index and shape is characterized with light scattering measurements. This work focuses on particle release and does not assess toxicity or effects on living organisms.
2023
Migliorini, L., Santaniello, T., Falqui, A., & Milani, P. (2023). ACS Applied Nano Materials, 6(10), 8999-9007.
Filippo Profumo, Francesca Borghi, Andrea Falqui, Paolo Milani, Journal of Physics D: Applied Physics 56,35
Giacomo Nadalini, Francesca Borghi, Paolo Piseri, Marcel Di Vece, Physica E: Low-dimensional Systems and Nanostructures 151, 115708
M.A.C. Potenza, L. Cremonesi
We discuss how the range of information available from microparticle analysis can be extended in a number of applications by measuring a specific set of optical properties of individual particles using light scattering. Central to these measurements are the real and imaginary components of the forward scattered field, the former being equal to the extinction cross-section except for a few particle-independent constants. Although still a niche technique, it has some inherent advantages and great potential for particle characterization, especially in the challenging near-wavelength size range. A selection of cases is covered from an experimental point of view, while some essential models are introduced to illustrate the underlying physical phenomena. We present a benchmark of experimental results from the literature and other examples that support optical diagnostics applied in science and industrial processes. As a key point of this work, we show that by accessing the fundamental properties of scatterers the inversion of light scattering data can be avoided. This provides model-independent results closer to application requirements without the drawbacks of case-specific assumptions.
B. Paroli, G. Martini, M.A.C. Potenza, M. Siano, M. Mirigliano, P. Milani
Among several approaches to tackle the problem of energy consumption in modern computing systems, two solutions are currently investigated: one consists of artificial neural networks (ANNs) based on photonic technologies, the other is a different paradigm compared to ANNs and it is based on random networks of non-linear nanoscale junctions resulting from the assembling of nanoparticles or nanowires as substrates for neuromorphic computing. These networks show the presence of emergent complexity and collective phenomena in analogy with biological neural networks characterized by self-organization, redundancy, and non-linearity. Starting from this background, we propose and formalize a generalization of the perceptron model to describe a classification device based on a network of interacting units where the input weights are non-linearly dependent. We show that this model, called “receptron”, provides substantial advantages compared to the perceptron as, for example, the solution of non-linearly separable Boolean functions with a single device. The receptron model is used as a starting point for the implementation of an all-optical device that exploits the non-linearity of optical speckle fields produced by a solid scatterer. By encoding these speckle fields we generated a large variety of target Boolean functions. We demonstrate that by properly setting the model parameters, different classes of functions with different multiplicity can be solved efficiently. The optical implementation of the receptron scheme opens the way for the fabrication of a completely new class of optical devices for neuromorphic data processing based on a very simple hardware.
M. Siano, G. Geloni, B. Paroli, D. Butti, T. Lefèvre, S. Mazzoni, G. Trad, U. Iriso, A.A. Nosych, L. Torino, M.A.C. Potenza
FOCUS (Fast Monte CarlO approach to Coherence of Undulator Sources) is a new GPU-based simulation code to compute the transverse coherence of undulator radiation from ultra-relativistic electrons. The core structure of the code, which is written in the language C++ accelerated with CUDA, combines an analytical description of the emitted electric fields and massively parallel computations on GPUs. The combination is rigorously justified by a statistical description of synchrotron radiation based on a Fourier optics approach. FOCUS is validated by direct comparison with multi-electron Synchrotron Radiation Workshop (SRW) simulations, evidencing a reduction in computation times by up to five orders of magnitude on a consumer laptop. FOCUS is then applied to systematically study the transverse coherence in typical third- and fourth-generation facilities, highlighting peculiar features of undulator sources close to the diffraction limit. FOCUS is aimed at fast evaluation of the transverse coherence of undulator radiation as a function of the electron beam parameters, to support and help prepare more advanced and detailed numerical simulations with traditional codes like SRW.
G. Melzi, E. Nozza, M.A. Frezzini, S. Canepari, R. Vecchi, L. Cremonesi, M. Potenza, M. Marinovich, E. Corsini
The toxicity of particulate matter (PM) is strictly associated with its physical-chemical characteristics, such as size or chemical composition. While these properties depend on the origin of the particles, the study of the toxicological profile of PM from single sources has rarely been highlighted. Hence, the focus of this research was to investigate the biological effects of PM from five relevant sources of atmospheric PM: diesel exhaust particles, coke dust, pellet ashes, incinerator ashes, and brake dust. Cytotoxicity, genotoxicity, oxidative, and inflammatory response were assessed in a bronchial cell line (BEAS-2B). BEAS-2B cells were exposed to different concentrations (25, 50, 100, and 150 μg/mL medium) of particles suspended in water. The exposure lasted 24 h for all the assays performed, except for reactive oxygen species, which were evaluated after 30 min, 1 h, and 4 h of treatment. The results showed a different action of the five types of PM. All the tested samples showed a genotoxic action on BEAS-2B, even in the absence of oxidative stress induction. Pellet ashes seemed to be the only ones able to induce oxidative stress by boosting the formation of reactive oxygen species, while brake dust resulted in the most cytotoxic. In conclusion, the study elucidated the differential response of bronchial cells to PM samples generated by different sources. The comparison could be a starting point for a regulatory intervention since it highlighted the toxic potential of each type of PM tested.
2022
Migliorini, L., Villa, S. M., Santaniello, T., & Milani, P. (2022). Nano Futures, 6(3), 032001.
Valentina Migliorati, Alessandra Del Giudice, Alberto Casu, Andrea Falqui, Alessandro Podestà, Paolo Milani, Francesca Borghi, Journal of Physical Chemistry C 126, 31, 13477–13484
https://doi.org/10.1021/acs.jpcc.2c04022
Piazzoni, M., Piccoli, E., Migliorini, L., Milana, E., Iberite, F., Vannozzi, L., … & Santaniello, T. (2022). Soft Robotics, 9(2), 224-232.
Francesca Borghi, Francesca Soavi, Paolo Milani
. Aharon, D.R. Ceratti, N.P. Jasti, L. Cremonesi, Y. Feldman, M.A.C. Potenza, G. Hodes, D. Cahen
Adding a 2D character to halide perovskite (HaP) active layers in ambient-protected cells can improve their stability drastically, which is not obvious from the hydrophobicity of the large cations that force the HaP into a 2D structure. Results of two-photon confocal microscopy are reported to study inherent photo-stability of 2D Pb iodide HaPs in the interior of single crystals. Compared to 3D HaP crystals, 2D ones have higher photo-stability and, under a few sun-equivalent conditions, self-heal efficiently after photo-damage. Using both photoluminescence (PL) intensities (as function of time after photo-damage) and spectra, self-healing dynamics of 2D HaP (C4H9NH3)2PbI4, 2D/3D (C4H9NH3)2(CH3NH3)2Pb3I10 and 3D MAPbI3 are compared. Differences in response to photo-damage and self-healing ability from different degrees of photo-damage are found between these HaPs. Based on the findings, a possible chemical mechanism for photo-damage and self-healing of the 2D HaPs is suggested: the layered lattice arrangement limits out-diffusion of degradation products, facilitating damage reversal, leading to better 2D HaP photo-stability and self-healing uniformity than for 2D/3D HaPs. One implication of the layered structures’ resilience to photo-damage is transfer of their increased stability to devices made with them, such as photovoltaic solar cells and light-emitting diodes.
M.A.C. Potenza, L. Cremonesi
A quasi-universality property of Mie scattering was reported in a recent publication by C.M. Sorensen [J. Quant. Spectrosc. Radiat. Transf. (2013) 131, 3]: the authors represent the forward scattered intensity, normalized by the differential Rayleigh cross section, as a function of the coupling parameter. Here we provide clear experimental evidence of this result; the Sorensen plots are produced without any free parameter for pure water droplets suspended in air and oil-in-water emulsions measured by the Single Particle Extinction and Scattering method. In addition, as inferred by Sorensen, we find that non-spherical objects deviate from the quasi-universality behavior of spheres by applying the same approach to mineral dust. Notably, the larger discrepancies occur in the wavelength-scale size range. These plots can widen the field of diagnostics in the critical micrometric size range.
B. Paroli, L. Cremonesi, M. Siano, M. Potenza
We propose multiplexing and demultiplexing of Orbital Angular Momentum (OAM) states realized with incoherent beams to increase the effective transmission area in a free space optical communication link. The overlapped states of the beams have been effectively distinguished using a hybrid OAM-Amplitude scheme exploiting only a small portion of the entire wavefront at the receiver. The method has been theoretically formalized and the transmission experimentally tested up to 1 Mbit/s. The proposed method is suitable for high density transmission in long-distance free space optical communication systems.
M. Siano, B. Paroli, M.A.C. Potenza, L. Teruzzi, U. Iriso, A.A. Nosych, E. Solano, L. Torino, D. Butti, A. Goetz, T. Lefevre, S. Mazzoni, G. Trad
In this paper we report on recent two-dimensional (2D) electron beam size measurements with a nonconventional synchrotron radiation interferometric technique based on x-ray heterodyne near field speckles (HNFS). The method relies on Fourier analysis of the random speckle patterns generated by a water suspension of nanospheres to assess the full 2D transverse coherence of the incoming x rays. The horizontal and vertical electron beam sizes are then retrieved by means of statistical optics approaches. The manuscript thoroughly describes the HNFS technique, and shows experimental results obtained at the ALBA Synchrotron Light Source. By changing the machine coupling, beam sizes as small as 5 microns are measured, thus improving on past measurements reported in the literature and proving the HNFS diagnostics suitable for low-emittance particle beams.
2021
Migliorini, L., Piazzoni, C., Pohako‐Esko, K., Di Girolamo, M., Vitaloni, A., Borghi, F., … & Milani, P. (2021). Advanced Functional Materials, 31(27), 2102180.
Dotan, T., Berg, Y., Migliorini, L., Villa, S. M., Santaniello, T., Milani, P., & Shacham-Diamand, Y. (2021). Microelectronic Engineering, 237, 111478.
Villa, S. M., Maturi, M., Santaniello, T., Migliorini, L., Locatelli, E., Franchini, M. C., & Milani, P. (2021). Sensors and Actuators A: Physical, 332, 113196.
C. Ravasio, L. Cremonesi, C. Artoni, B. Delmonte, V. Maggi, M.A.C. Potenza
We describe an optical approach based on Digital Holography for single-particle characterization of mineral dust and micrometric particles, focusing on the analysis of airborne particles in meltwater from Antarctic ice cores. We record the holograms formed by the superposition of the transilluminating reference beam and the waves scattered by single particles. Taking a cue from recent approaches in the field and holography methods, we process the holograms to recover both optical and morphological properties of single dust grains. As a considerable advantage over traditional light-scattering-based methods, holograms give the extinction cross section of each particle and, by numerically reconstructing the wavefront propagation, an unambiguous image of each particle whereby we derive its cross-sectional shape and size. Measurements have been carried out on samples collected from the recent EAIIST (East Antarctic International Ice Sheet Traverse) project, some of which show evidence of volcanic events. The vast majority of the detected particles show significant deviations from the isometric shape, as confirmed by both image reconstruction and extinction cross section analysis. By our analysis, we observe that experimental data have an extinction cross section up to 3 times lower than that of spherical particles with the same volume. Therefore, these deviations have an appreciable impact on the aerosol contribution to radiative forcing: retrieving particle shape may improve the modeling of the radiative properties of mineral dust and reduce the associated uncertainties.
B. Paroli, M. Siano, M.A.C. Potenza
We describe an innovative data transmission scheme exploiting optical vortices to multiplex and demultiplex independent data channels in a standard asynchronous laser link. We report extensive results of the proof of concept of the method, successfully used to transmit two parallel ASCII strings, demultiplexed and decoded in the far field of the radiation beam. A phase locked two arms interferometer is proved to be effective even accessing a small portion of the beam only. Results prove the robustness and reliability of the method to perform dense-code free space transmissions over long distances even in presence of wavefront distortions. Applications and the extension to a larger number of parallel channels are discussed.
.R. Ceratti, A.V. Cohen, R. Tenne, Y. Rakita, L. Snarski, N.P. Jasti, L. Cremonesi Plaja, R. Cohen, M. Weitman, I. Rosenhek-Goldian, I. Kaplan-Ashiri, T. Bendikov, V. Kalchenko, M. Elbaum, M.A.C. Potenza, L. Kronik, G. Hodes, D. Cahen
We find significant differences between degradation and healing at the surface or in the bulk for each of the different APbBr3 single crystals (A = CH3NH3+, methylammonium (MA); HC(NH2)2+, formamidinium (FA); and cesium, Cs+). Using 1- and 2-photon microscopy and photobleaching we conclude that kinetics dominate the surface and thermodynamics the bulk stability. Fluorescence-lifetime imaging microscopy, as well as results from several other methods, relate the (damaged) state of the halide perovskite (HaP) after photobleaching to its modified optical and electronic properties. The A cation type strongly influences both the kinetics and the thermodynamics of recovery and degradation: FA heals best the bulk material with faster self-healing; Cs+ protects the surface best, being the least volatile of the A cations and possibly through O-passivation; MA passivates defects via methylamine from photo-dissociation, which binds to Pb2+. DFT simulations provide insight into the passivating role of MA, and also indicate the importance of the Br3- defect as well as predicts its stability. The occurrence and rate of self-healing are suggested to explain the low effective defect density in the HaPs and through this, their excellent performance. These results rationalize the use of mixed A-cation materials for optimizing both solar cell stability and overall performance of HaP-based devices, and provide a basis for designing new HaP variants.
M.A.C. Potenza
Easy and cheap optics experiences are described to teach undergraduate students the fundamental properties of Fourier transform on an experimental basis. By exploiting the eye as the Fourier transforming device, a common magnifying lens and quasi-coherent light from a small white LED, quantitative results can be easily obtained about the fundamental theorems in Fourier analysis. The concept of coherence is also introduced in an elementary way. This approach has been successfully adopted to teach third year students in Physics, who operated in a complete autonomous way during the COVID-19 lockdown without accessing any laboratory. This proves the effectiveness of the method. Thanks to its experimental simplicity it can be easily extended to teach and show the fundamental effects to a larger audience, including high school students.
M. Siano, B. Paroli, M.A.C. Potenza
A fascinating way of generating speckle patterns is by interfering the weak fields scattered by a disordered sample with the intense trans-illuminating beam. The resulting intensity fluctuations are known as Heterodyne Near Field Speckles. Thanks to the self-referencing layout, the intensity distribution allows direct assessment of the electric fields, thus preserving both amplitude and phase information. Originally observed with visible laser light, during the last years Heterodyne Near Field Speckles have been extended to partially coherent radiation and to X-ray beams. We give in this review a uniform argumentation of Heterodyne Near Field Speckles based on Fourier Optics, valid with both coherent and partially coherent illumination. Emphasis is given to the speckle size, a fundamental property of any speckle field and a basis for earlier and state-of-the-art development of the technique. We review the applications of Heterodyne Near Field Speckles in the fields of particle sizing, velocimetry, coherence measurements, X-ray wavefront sensing and X-ray phase-contrast imaging and tomography. Throughout the discussion, we also emphasize the common aspects shared with many different research areas, such as astronomical observations, holography and TEM imaging, thus evidencing the encompassing nature of the underlying physical principles.
M. Siano, D. Butti, A. Goetz, U. Iriso, T. Lefèvre, S. Mazzoni, A. Nosych, B. Paroli, M.A.C. Potenza, E. Solano, L. Teruzzi, L. Torino, G. Trad
We report on 2D beam size measurements with a novel interferometric technique named Heterodyne Near Field Speckles, capable of resolving few-micrometer beam sizes. It relies on the interference between the weak spherical waves scattered by a colloidal suspension and the intense transilluminating X-ray beam. Fourier analysis of the resulting speckles enables full 2D coherence mapping of the incoming radiation, from which the beam sizes along the two orthogonal directions are retrieved. We show experimental results obtained with 12.4 keV X-rays at the NCD-SWEET undulator beamline at ALBA, where the vertical beam size has been changed between 4 and 14 micrometers by varying the beam coupling. The results agree well with the estimated beam sizes from the pinhole calculations. Finally, we discuss recent investigations on alternative targets aimed at improving the signal-to-noise ratio of the technique.
2020
F. Simonetto, M. Marmonti, M.A.C. Potenza
We study the optical properties of glass exposed to ionizing radiation as it occurs in the space environment. Twenty-four glass types have been considered, both space-qualified and not space-qualified. Seventy-two samples (3 for each glass type) have been irradiated to simulate total doses of 10 and 30 krad imposed by a proton beam at KVI-Centre of Advanced Radiation Technology (Groeningen). Combining information concerning stopping power and proton fluence, the time required to reproduce any given total dose in a real environment can be easily obtained. The optical properties, such as spectral transmission and light scattering, have been measured before and after irradiation for each sample. Transmission has been characterized within the wavelength range of 200 to 1100 nm. Indications that systematical issues depend on the dopant or composition are found and described. Our work aims at extending the existing list of space-compliant glasses in terms of radiation damage.
B. Paroli, M. Siano, M.A.C. Potenza
We show a method to measure the topological charge of orbital angular momentum radiation in single-shot by exploiting the intrinsic local curvature of the helicoidal wavefront. The method is based on oriented Hartmann cells in a suitable detection scheme. We show experimental results and propose a Shack-Hartmann configuration with sectored photodiodes to improve resolution and detection time. The method can be applied for telecommunication applications in the far field of the radiation beam and more in general to measure the topological charge from a small portion of the radiation wavefront.
B. Paroli, M. Siano, M.A.C. Potenza
We introduce and report experimental realization of amethod to measure the topological charge of radiation carrying orbital angular momentum by accessing a small portion of the wavefront. The method exploits the superposition of matched-curvature beams in separated frequency bands to achieve a differential measure realized by a pair of phase-sensitive detectors. The method is suitable for long-distance communications.
L. Scalcinati, B. Paroli, M. Zannoni, M.A.C. Potenza
We exploit the properties of differential geometry of minimal surfaces to introduce a novel approach for characterizing wavefronts. Since Gaussian and mean curvatures describe global and local properties of any differentiable surface, a method for characterizing wavefronts endowed with non-trivial topological features has been introduced. We provide experimental evidence that the wavefront of an l = 1 radio-vortex at 30 GHz can be fully characterized by exploiting the wavefront phase in the far field of the source, accessing a small portion of the beam only. A particular care is dedicated to distinguish diffraction effects from the intrinsic curvature of the helicoidal wavefront. Results are applicable to the local measurement of the topological charge and to the local detection of orbital angular momentum radiation at the millimetric wavelengths.
L. Cremonesi, C. Minnai, F. Ferri, A. Parola, B. Paroli, T. Sanvito, M.A.C. Potenza
The influence of the internal structure of inhomogeneous particles on their radiative properties is an open issue repeatedly questioned inmany fields of science and technology. The importance of a refined description of the particle composition and structure, going beyond mean-field approximations, is generally recognized. Here, we focus on describing internal inhomogeneities from a statistical point of view. We introduce an analytical description based on the two-point density-density correlation function, or the corresponding static structure factor, to calculate the extinction cross sections. The model agrees with numerical predictions and is validated experimentally with colloidal aggregates in the 0.3–6 μm size range, which serve as an inhomogeneous model system that can be characterized enough to work without any free parameters. The model can be tightly compared to measurements with single particle extinction and scattering and spectrophotometry and suggests a simple behavior for 90° scattering from fractal aggregates as a function of extinction, which is also confirmed experimentally and numerically. We also discuss the case of absorbing particles and report the experimental results for water suspensions of black carbon for both the forward and 90° scattering properties. In this case, the total scattering and the extinction cross sections determine the single scattering albedo, which agrees with numerical simulations. The three parameters necessary to feed radiative transfer models, namely, extinction, asymmetry parameter, and single scattering albedo, can all be set by the analytical model, with explicit dependence on a few parameters. Results are applicable to radiative transfer problems in climate, paleoclimate, star and planetary formation, and nanoparticle optical characterization for science and industry, including the intercomparison of different optical methods such as those adopted by ISO standards.
A. Goetz, D. Butti, U. Iriso, S. Mazzoni, A. Nosych, B. Paroli, M.A.C. Potenza, M. Siano, L. Teruzzi, L. Torino, G. Trad
Heterodyne Near Field Speckles (HNFS) is a special type of interferometry technique where radiation is scattered by nanoparticles suspended in a medium. The weak scattered waves and the intense transmitted beam form an interference pattern, which is modulated by the spatial coherence of the radiation and by the scattering properties of the nanoparticles. The random superposition of many such interference patterns results in a speckle field from which the spatial coherence of the radiation, thus the transverse beam profile, can be determined. In this contribution we present approaches for simulating the HNFS patterns from hard X-ray radiation and compare then with data from experiments at the ALBA synchrotron.
L. Cremonesi, M. Siano, B. Paroli, M. Potenza
We describe a light scattering technique for characterizing colloidal samples under constant flow. It exploits the properties of speckles in the deep Fresnel region—the so-called near field speckles—providing absolute scattering measurements of the static form factor of the sample, as described extensively by Mazzoni et al. [Rev. Sci. Instrum. 84, 043704 (2013)] for static samples. We exploit a strongly astigmatic beam for illuminating the scattering volume with a light sheet a few microns thick. This largely improves the sensitivity of the method to small signals. Moreover, by flowing the sample in the direction perpendicular to the light sheet, the transit times are reduced to a minimum, allowing for fast measurements. We tested the instrument with suspensions of calibrated colloidal polystyrene spheres with a size comparable to the light wavelength. In particular, we recovered the static form factors of suspensions of spherical particles and the phase lag of the zero-angle scattering amplitude, which both compare well to Mie theory predictions. We then applied the method to colloidal fractal aggregates of sub-wavelength particles and measured their fractal dimension. The instrument is designed to be operational in continuous flow analysis systems.
2019
M. Siano, M.A.C. Potenza, B. Paroli, U. Iriso, C.S. Kamma-Lorger, A.A. Nosych, S. Mazzoni, G. Trad
Experiments using the heterodyne near field speckle method (HNFS) have been performed at ALBA to characterize the spatial coherence of the synchrotron radiation, with the ultimate goal of measuring both the horizontal and vertical electron beam sizes. The HNFS technique consists on the analysis of the interference between the radiation scattered by a colloidal suspension of nanoparticles and the synchrotron radiation, which in this case corresponds to the hard x-rays (12keV) produced by the in-vacuum undulator of the NCD-Sweet beamline. This paper describes the fundamentals of the technique, possible limitations, and shows the first experimental results changing the beam coupling of the storage ring.
L. Serafini, A. Bacci, A. Bellandi, M. Bertucci, M. Bolognesi, A. Bosotti, F. Broggi, R. Calandrino, F. Camera, F. Canella, S. Capra, P. Cardarelli, M. Carrara, K. Cassou, A. Castoldi, R. Castriconi, G.M. Cattaneo, S. Cialdi, A. Cianchi, N. Coluccelli, C. Curatolo, A. Del Vecchio, S. Di Mitri, I. Drebot, K. Dupraz, A. Esposito, L. Faillace, M. Ferrario, C. Fiorini, G. Galzerano, M. Gambaccini, G. Ghiringhelli, D. Giannotti, D. Giove, F. Groppi, C. Guazzoni, P. Laporta, S. Leoni, A. Loria, P. Mangili, A. Martens, T. Mazza, Z. Mazzotta, C. Meroni, G. Mettivier, P. Michelato, L. Monaco, S. Morante, M. Moretti Sala, D. Nutarelli, S. Olivares, G. Onida, M. Opromolla, C. Pagani, R. Paparella, M.G.A. Paris, B. Paroli, G. Paternò, C. Paulin, L. Perini, M. Petrarca, V. Petrillo, E. Pinotti, P. Piseri, M.A.C. Potenza, F. Prelz, A. Pullia, E. Puppin, F. Ragusa, R. Ramponi, M. Romè, M. Rossetti Conti, A.R. Rossi, L. Rossi, M. Ruijter, P. Russo, S. Samsam, A. Sarno, D. Sertore, M. Sorbi, B. Spataro, M. Statera, F. Stellato, E. Suerra, A. Tagliaferri, A. Taibi, V. Torri, G. Turchetti, C. Vaccarezza, R. Valdagni, A. Vanzulli, F. Zomer, G. Rossi
The need of a fs-scale pulsed, high repetition rate, X-ray source for time-resolved fine analysis of matter (spectroscopy and photon scattering) in the linear response regime is addressed by the conceptual design of a facility called MariX (Multi-disciplinary Advanced Research Infrastructure for the generation and application of X-rays) outperforming current X-ray sources for the declared scope. MariX is based on the original design of a two-pass two-way superconducting linear electron accelerator, equipped with an arc compressor, to be operated in CW mode (1 MHz). MariX provides FEL emission in the range 0.2-8 keV with 108 photons per pulse ideally suited for photoelectric eect and inelastic X-ray scattering experiments. The accelerator complex includes an early stage that supports an advanced inverse Compton source of very high-flux hard X-rays of energies up to 180 keV that is well adapted for large area radiological imaging, realizing a broad science programme and serving a multidisciplinary user community, covering fundamental science of matter and application to life sciences, including health at preclinical and clinical level.
B. Paroli, M. Siano, L. Teruzzi, M.A.C. Potenza
We show a single-shot technique to measure topological and phase properties of radiation carrying orbital angular momentum. The single-shot method is effectively described as the one-dimensional case of a more general two-dimensional approach based on scanning interferometry (asymmetric lateral coherence). The validity of the method has been experimentally verified and the applicability to ultrarelativistic sources of hard x-rays has been discussed. The method is suitable to characterize phase and topological properties of x-ray sources by using simple apertures.
S. Maiorana, F. Teoldi, S. Silvani, A. Mancini, A. Sanguineti, F. Mariani, C. Cella, A. Lopez, M.A.C. Potenza, M. Lodi, D. Dupin, T. Sanvito, A. Bonfanti, E. Benfenati, D. Baderna
Traffic-related emissions include gas and particles that can alter air quality and affect human and environmental health. Limited studies have demonstrated that particulate debris thrown off from brakes are toxic to higher plants. The acute phytotoxicity of brake pad wear debris (BPWD) investigated using cress seeds grown in soil contaminated with increasing concentrations of debris. Two types of pads were used: a commercially available phenol based pad and an innovative cement-based pad developed within of the LIFE+ COBRA project. The results suggested that even through the BPWD generated by the two pads were similar in and morphology, debris from traditional pads were more phytotoxic than that from cementitious pads, causing significant alterations in terms of root elongation and loss of plasma membrane integrity.
B. Paroli, M. Siano, M.A.C. Potenza
We show a novel technique and a detection scheme for local measurements of Orbital Angular Momentum radiation based on the inversion of the transverse intrinsic curvature sign of minimal surfaces.
C. Minnai, L. Cremonesi, P. Milani, M. Potenza
We report the fabrication of a simple and inexpensive device based on diffractive optics for spectrally resolved imaging. A brass surface manufactured on a metal lathe and a deformable, reflecting diffraction grating guarantee spatially and spectrally resolved images without the need for other optical elements. The grating is a metal-polymer nanocomposite replica of a plastic grating: reflectivity of the transparent dielectric substrate is obtained by the implantation of gold clusters, hence preserving deformability. The brass surface is a portion of a rotation ellipsoid, on which the deformable grating adheres to gain optical power. According to the optical tests performed on the system, the achieved spatial resolution of the system is ~80 μm, whereas limiting spectral resolution of about 3 nm is observed. Reflectivity of the zero-order reflection and the first order diffraction approaches 45% and 5% respectively. We detail the results for the reconstruction of an on-axis and off-axis pointlike source, and a vertically extended slit-like source with a 110 μm obstruction.
B. Paroli, M. Siano, M.A.C. Potenza
We describe a method for effectively distinguishing the radiation endowed with optical angular momentum, also known as optical vortex, from ordinary light. We show that by detecting the inversion of the transverse intrinsic curvature sign (ITICS) an optical vortex can be locally recognized. The method is effective under conditions of huge importance for the exploitation of optical vortices, such as the far field of the source and access to a small fraction of the wavefront only. The validity of the method has been verified with table-top experiments with visible light, and the results show that a measurement performed over a transverse distance smaller than 4% of the beam diameter distinguishes a vortex from a Gaussian beam with a significance of 93.4%. New perspectives are considered for the characterization of vortices, with potential impact on the detection of extra-terrestrial radiation as well as on broadcast communication techniques.
S. Mazzoni, F. Roncarolo, G. Trad, B. Paroli, M. Potenza, M. Siano, U. Iriso, C.S. Kamma-Lorger, A.A. Nosych
We present the recent developments of a study aimed at measuring the transverse beam profile using the Heterodyne Near Field Speckles (HNFS) method. The HNFS technique works by illuminating a suspension of Brownian nanoparticles with synchrotron radiation and studying the resulting interference pattern. The transverse coherence of the source, and therefore, under the conditions of validity of the Van Cittert and Zernike theorem, the transverse electron beam size is retrieved from the interference between the transmitted beam and the spherical waves scattered by each nanoparticle. We here describe the fundamentals of this technique, as well as the recent experimental results obtained with 12 keV undulator radiation at the NCD beamline at the ALBA synchrotron. The applicability of such a technique for future accelerators (e.g. CLIC or FCC) is also discussed.
L. Cremonesi, A. Passerini, A. Tettamanti, B. Paroli, B. Delmonte, S. Albani, F. Cavaliere, D. Viganò, G. Bettega, T. Sanvito, A. Pullia, M.A.C. Potenza
We describe a robust, portable, deployable instrument for multiparametric optical characterization of single airborne particles. It is based on the Single Particle Extinction and Scattering method with additional sensors at 45° and 90° angles. Four independent optical parameters are associated to each particle. Basically, it provides a rigorous measurement of the extinction cross section and the complex amplitude of the forward scattered field. Moreover, thanks to the multiparametric single particle approach, it is possible to roughly classify the particles within a size range from a few hundreds of nanometers to some micrometers. By assigning a reasonable single scattering albedo for each population, our data are enough to fit the phase function with acceptable uncertainties. We report here the results of tests performed with water droplets, generating well controlled data without any free parameters. Data analysis is described in detail. We also report measurements performed on urban aerosol collected in the city of Milan by recovering the optical properties and feeding radiative transfer models. The findings reported here support the importance of an accurate measurement of the phase function, as already established by the Community.
2018
M.A.C. Potenza, S.J. Veen, P. Schall, G.H. Wegdam
We investigate the incipient stages of the formation of aggregates of weakly attractive particles in microgravity. Using colloidal particles interacting with tunable critical Casimir forces, we drive the system increasingly out of equilibrium starting from near-equilibrium gas-solid coexistence, and follow the early stages of aggregation with near-field scattering. Contrary to measurements on ground that show a rapid exponential growth of aggregates, our microgravity measurements indicate that under pure diffusion-limited conditions, the formation of aggregates is still governed by a nucleation process over the investigated range of moderate attractive strength of a few k B T. By studying in detail the decrease of the critical radius with the increase of the attractive strength, we determine a surface tension of 115 nN/m, or , with σ the particle diameter, of the order of but larger than that for equilibrium colloidal liquids and crystals. These results highlight the importance of nucleation in the formation of non-equilibrium solid aggregates bound by weakly attractive forces.We show a novel technique and a detection scheme for local measurements of Orbital Angular Momentum radiation based on the inversion of the transverse intrinsic curvature sign of minimal surfaces.
L. Serafini, A. Bacci, F. Broggi, A. Bosotti, S. Coelli, C. Curatolo, I. Drebot, L. Faillace, D. Giannotti, D. Giove, C. Meroni, P. Michelato, L. Monaco, R. Paparella, F. Prelz, A.R. Rossi, D. Sertore, M. Statera, F. Tomasi, V. Torri, R. Saban, A. Esposito, A. Gallo, C. Vaccarezza, F. Camera, F. Castelli, S. Cialdi, F. Groppi, B. Paroli, G. Onida, L. Perini, V. Petrillo, N. Piovella, P. Piseri, M. Potenza, M. Rossetti Conti, G. Rossi, A. Castoldi, G. Galzerano, G. Ghiringhelli, C. Guazzoni, M. Moretti, E. Pinotti, E. Puppin, A. Tagliaferri, F. Stellato, M. Placidi, G. Turchetti, S. Di Mitri, R. Calandrino, A. Delvecchio, P. Cardarelli, M. Gambaccini, G. Paternò, A. Taibi, G. Mettivier, P. Russo, A. Sarno
MariX (Multidisciplinary advanced research infrastructure with X-rays) is a joint project of INFN and Universi-ty of Milan, aiming at developing a twin X-ray Source of advanced characteristics for the future Scientific Campus of the University of Milan. Presently in its design study phase, it will be built in the post Expo area located in north-west Milan district. The first component of the X-source MariX is BriXS (Bright and compact X-ray Source), a Compton X-ray source based on superconduct-ing cavities technology for the electron beam with energy recirculation and on a laser system in Fabry-Pérot cavity at a repetition rate of 100 MHz, producing 20-180 keV radiation for medical applications. The BriXS accelerator is also serving as injector of a 3.8 GeV superconductive linac, driving a X-ray FEL at 1 MHz, for providing co-herent, moderate flux radiation at 0.3-10 KeV at 1 MHz. Scientific case, layout and typical parameters of MariX will be discussed.
M.F. Simonsen, L. Cremonesi, G. Baccolo, S. Bosch, B. Delmonte, T. Erhardt, H.A. Kjær, M. Potenza, A. Svensson, P. Vallelonga
The Klotz Abakus laser sensor and the Coulter Counter are both used for measuring the size distribution of insoluble mineral dust particles in ice cores. While the Coulter Counter measures particle volume accurately, the equivalent Abakus instrument measurement deviates substantially from the Coulter Counter depending on the type of sample. We show that the difference between the Abakus and the Coulter Counter measurements is mainly caused by the irregular shape of dust particles in 5 ice core samples. The irregular shape leads means that the calibration routine based on standard spheres must be adjusted. This new calibration routine gives an increased accuracy on Abakus measurements, which may improve future ice core record intercomparisons. We derived an analytical model for extracting the aspect ratio of dust particles from the difference between Abakus and Coulter Counter data. For verification, we measured the aspect ratio of the same samples directly using a Single Particle Extinction and Scattering Instrument. The results demonstrate that the model is accurate enough to discern between 10 samples of aspect ratio 0.3 and 0.4 using only the comparison of Abakus and Coulter Counter data.
D.R. Ceratti, Y. Rakita, L. Cremonesi, R. Tenne, V. Kalchenko, M. Elbaum, D. Oron, M.A.C. Potenza, G. Hodes, D. Cahen
Self-healing, where a modification in some parameter is reversed with time without any external intervention, is one of the particularly interesting properties of halide perovskites. While there are a number of studies showing such self-healing in perovskites, they all are carried out on thin films, where the interface between the perovskite and another phase (including the ambient) is often a dominating and interfering factor in the process. Here, self-healing in perovskite (methylammonium, formamidinium, and cesium lead bromide (MAPbBr3, FAPbBr3, and CsPbBr3)) single crystals is reported, using two-photon microscopy to create damage (photobleaching) ≈110 µm inside the crystals and to monitor the recovery of photoluminescence after the damage. Self-healing occurs in all three perovskites with FAPbBr3 the fastest (≈1 h) and CsPbBr3 the slowest (tens of hours) to recover. This behavior, different from surface-dominated stability trends, is typical of the bulk and is strongly dependent on the localization of degradation products not far from the site of the damage. The mechanism of self-healing is discussed with the possible participation of polybromide species. It provides a closed chemical cycle and does not necessarily involve defect or ion migration phenomena that are often proposed to explain reversible phenomena in halide perovskites.
V. Galbiati, L. Cornaghi, E. Gianazza, M.A. Potenza, E. Donetti, M. Marinovich, E. Corsini
This study aimed to characterize unwanted immune effects of nanoparticles (NP) using THP-1 cells, human whole blood and enriched peripheral blood monocytes. Commercially available silver NP (AgNP < 100 nm, also confirmed by Single Particle Extinction and Scattering) were used as prototypical NP. Cells were treated with AgNP alone or in combination with classical immune stimuli (i.e. LPS, PHA, PWM) and cytokine assessed; in addition, CD54 and CD86 expression was evaluated in THP-1 cells. AgNP alone induced dose-related IL-8 production in all models, with higher response observed in THP-1 cells, possibly connected to different protein corona formation in bovine versus human serum. AgNP potentiated LPS-induced IL-8 and TNF-α, but not LPS-induced IL-10. AgNP alone induced slight increase in IL-4, and no change in IFN-γ production. While responses to PHA in term of IL-4 and IFN-γ production were not affected, increased PWM-induced IL-4 and IFN-γ production were observed, suggesting potentiation of humoral response. Reduction in PHA-induced IL-10 was observed. Overall, results indicate immunostimulatory effects. THP-1 cells work as well as primary cells, representing a useful and practical alternative, with the awareness that from a physiological point of view the whole blood assay is the one that comes closest to reality.
C. Goy, M.A.C. Potenza, S. Dedera, M. Tomut, E. Guillerm, A. Kalinin, K. Voss, A. Schottelius, N. Petridis, A. Prosvetov, G. Tejeda, J.M. Fernã¡ndez, C. Trautmann, F. Caupin, U. Glasmacher, R.E. Grisenti
The fast evaporative cooling of micrometer-sized water droplets in a vacuum offers the appealing possibility to investigate supercooled water – below the melting point but still a liquid – at temperatures far beyond the state of the art. However, it is challenging to obtain a reliable value of the droplet temperature under such extreme experimental conditions. Here, the observation of morphology-dependent resonances in the Raman scattering from a train of perfectly uniform water droplets allows us to measure the variation in droplet size resulting from evaporative mass losses with an absolute precision of better than 0.2%. This finding proves crucial to an unambiguous determination of the droplet temperature. In particular, we find that a fraction of water droplets with an initial diameter of 6379±12 nm remain liquid down to 230.6±0.6 K. Our results question temperature estimates reported recently for larger supercooled water droplets and provide valuable information on the hydrogen-bond network in liquid water in the hard-to-access deeply supercooled regime.
V. Bernardoni, A.C. Forello, M. Federico, B. Paroli, M.A.C. Potenza, A. Pullia, R. Francesco, S. Tiziano, S. Valentini, G. Valli, R. Vecchi
Aerosol optical properties (i.e. scattering and absorption) are of great im-portance to assess aerosol effects e.g. on visibility and Earth radiation bal-ance. In this paper, we present innovative optical instrumentation developed at the Department of Physics of the University of Milan: a multi-wavelength polar photometer (PP_UniMI) and a Single Particle Extinction and Scatter-ing (SPES). PP_UniMI is a filter-based device providing the aerosol absorp-tion coefficient of aerosol at 4 wavelengths (). Such measurements are of interest to have insights into the -dependent behavior of aerosol absorption properties, which is still poorly understood especially for what concerns weakly absorbing aerosol components. SPES allows to determine the size and refractive index of single particles. In case of absorbing particles, also in-formation on the imaginary part of the refractive index – very important es-pecially in the field of global models – can be provided with little assump-tions. We describe the main features of the two instruments and their ad-vantages and limitations. Examples of application are also presented.
B. Paroli, A. Cirella, I. Drebot, V. Petrillo, M. Siano, M.A.C. Potenza
We show that phase properties and the local curvature of a wavefront with orbital angular momentum can be measured by the real part of the complex degree of coherence of radiation obtained with respect to an off-axis fixed point (asymmetric lateral coherence). The method can be implemented by exploiting a scan of double-slits along Cartesian axis. Because the method exploits simple apertures, it can be applied to measure topological and phase properties of stable sources in a wide range of wavelengths from microwaves to x-rays.
2017
F.P. Mariani, V. Bernardoni, F. Riccobono, R. Vecchi, G. Valli, T. Sanvito, B. Paroli, A. Pullia, M.A.C. Potenza
We apply to aerosols the optical method of Single Particle Extinction and Scattering recently proposed for characterizing liquid suspensions and specifically adapted to the aim. It provides simultaneous measurements of the real and imaginary parts of the field scattered in the forward direction by single airborne particles passing through a tightly focused laser beam. The intensity of transmitted light is collected in the forward direction, thus realizing a self-reference interferometric scheme relying on the fundamentals of the optical theorem. A high frequency (20Â MS/s), extended dynamics (12 bits) sampling is performed by a cheap segmented photodiode, and a specific pulse shape analysis is exploited to validate the signals against a precise mathematical model. We show that accessing two independent physical quantities allows to exploit physical models to recover the aerosol size distribution from the measurement of the refractive index, either real or even complex. Laboratory measurements have been performed with polydisperse aerosols made of water droplets and NaCl in the submicron range, and the system has been accurately characterized. Examples of measurements of graphite nanoparticles and Pyrethrum smoke are shown. Limitations are discussed.
B. Paroli, M.A.C. Potenza
Synchrotron, undulator and betatron radiations are generated from last generation and novel concept sources. The achievement of unprecedented radiation properties opens new opportunities in various research fields as well as novel potential applications. In particular, bright coherent X-rays and (Formula presented.) -rays have been recently obtained thanks to enormous efforts in technological advancements and research activities. We give in this work a uniform argumentation and comparison of the main fundamental emission processes and radiation properties of synchrotron, undulator and betatron radiations. Emphasis is given to spatial coherence and related diagnostics, a fundamental property for any ‘modern light source’ and a basis for recent important advancements.
M.A.C. Potenza, Z. Krpetic, T. Sanvito, Q. Cai, M. Monopoli, J.M. De Araujo, C. Cella, L. Boselli, V. Castagnola, P. Milani, K.A. Dawson
The shape and size of nanoparticles are important parameters affecting their biodistribution, bioactivity, and toxicity. The high-throughput characterisation of the nanoparticle shape in dispersion is a fundamental prerequisite for realistic in vitro and in vivo evaluation, however, with routinely available bench-top optical characterisation techniques, it remains a challenging task. Herein, we demonstrate the efficacy of a single particle extinction and scattering (SPES) technique for the in situ detection of the shape of nanoparticles in dispersion, applied to a small library of anisotropic gold particles, with a potential development for in-line detection. The use of SPES paves the way to the routine quantitative analysis of nanoparticles dispersed in biologically relevant fluids, which is of importance for the nanosafety assessment and any in vitro and in vivo administration of nanomaterials.
D. Biganzoli, M.A.C. Potenza, M. Robberto
We discuss the radiative transfer theory for translucent clouds illuminated by an extended background source. First, we derive a rigorous solution based on the assumption that multiple scatterings produce an isotropic flux. Then we derive a more manageable analytic approximation showing that it nicely matches the results of the rigorous approach. To validate our model, we compare our predictions with accurate laboratory measurements for various types of well-characterized grains, including purely dielectric and strongly absorbing materials representative of astronomical icy and metallic grains, respectively, finding excellent agreement without the need to add free parameters. We use our model to explore the behavior of an astrophysical cloud illuminated by a diffuse source with dust grains having parameters typical of the classic ISM grains of Draine & Lee and protoplanetary disks, with an application to the dark silhouette disk 114-426 in Orion Nebula. We find that the scattering term modifies the transmitted radiation, both in terms of intensity (extinction) and shape (reddening) of the spectral distribution. In particular, for small optical thickness, our results show that scattering makes reddening almost negligible at visible wavelengths. Once the optical thickness increases enough and the probability of scattering events becomes close to or larger than 1, reddening becomes present but is appreciably modified with respect to the standard expression for line-of-sight absorption. Moreover, variations of the grain refractive index, in particular the amount of absorption, also play an important role in changing the shape of the spectral transmission curve, with dielectric grains showing the minimum amount of reddening.
M.A.C. Potenza, L. Cremonesi, B. Delmonte, T. Sanvito, B. Paroli, A. Pullia, G. Baccolo, V. Maggi
Mineral dust aerosol in ice cores is one of the most important proxies for paleoclimate research. Under certain conditions, in the deeper part of ice cores, the pristine paleoclimate signal can be altered by in situ formation of dust aggregates, following the relocation of the impurities. Thus, aggregate detection is a critical indication for post-depositional processes. Clues for the presence of aggregates have been provided by anomalously large dust size distributions, while small aggregates were basically invisible to conventional dust analysis techniques. In this paper, we propose an optical approach to this problem based on the single-particle extinction and scattering (SPES) method, which allows researchers to distinguish between compact and non-compact particles through the analysis of samples populated by isometric particles contained in the core samples. This method can potentially be used during continuous flow analyses of ice cores. It allows for the detection of even the tiniest aggregates, falling within the typical size interval of aeolian mineral aerosol. This approach will potentially provide key evidence for assessing the integrity of paleoclimate records.
L. Barbieri, M. Gondola, M. Potenza, A. Villa, R. Malgesini
Electrical applications require the development of electric field sensors that can reproduce vector electric field waveforms with a very large spectral width ranging from 50 Hz to at least 70 MHz. This makes it possible to measure both the normal operation modes of electrical components and abnormal behaviors such as the corona emission and partial discharges. In this work, we aim to develop a fully dielectric sensor capable of measuring two components of the electric field using a wide class of optical crystals including anisotropic ones, whereas most of the efforts in this field have been devoted to isotropic crystals. We report the results of the measurements performed at 50 Hz and with a lightning impulse, to validate the sensor.
T. Sanvito, P. Bigini, M.V. Cavanna, F. Fiordaliso, M.B. Violatto, L. Talamini, M. Salmona, P. Milani, M.A.C. Potenza
Here we report the quantitative in situ characterization of size distribution evolution of polymeric nanoparticles incubated in murine serum, filtered and unfiltered murine blood. We used an analytical optical approach, named Single Particle Extinction and Scattering (SPES), which relies on the measurements of two independent parameters of single particles. SPES is based on a robust self-reference interference optical scheme which allows a rejection of the spurious signals coming from the background caused by the medium. We employed polystyrene nanoparticles as reference system and polydisperse poly(lactic-co-glycolic acid) nanoparticles. Our results demonstrate that SPES can be used for carrying out ex vivo analysis of nanoparticles to evaluate the modifications that NPs undergo in vivo following different routes of entry. Conversely, Dynamic Light Scattering is not able to provide reliable results for these systems due to the presence of the biological components in solution.
M. Siano, B. Paroli, M.A.C. Potenza, U. Iriso, A.A. Nosych, L. Torino, S. Mazzoni, G. Trad, A.N. Goldblatt
In this paper we extensively describe the heterodyne near field speckle method (HNFS) to characterize both spatial and temporal coherence of synchrotron radiation (SR). The method relies on Fourier analysis of near field speckles generated by scattering from nanoparticles suspended in a liquid. A criterion based on master curves of power spectra is introduced and validated by measurements on the visible light produced by the ALBA bending dipole. While spatial coherence measurements with HNFS have been reported, we present for the first time measurements of the temporal coherence of SR wavefronts with the HNFS method both for narrowband and white light beams. In the former case, using a band-pass filter, a coherence time of 40±10 fs is measured, in good agreement with the expected value of 43 fs for the filter inverse linewidth. Moreover, by exploiting the self-reference scheme of the technique, we show that coherence areas propagate carrying nonvanishing curvature. In the latter case, the measured coherence time of the incident SR without any monochromator is 1.6±0.4 fs, corresponding to a bandwidth of 240 nm at a peak wavelength of 350 nm. Exploiting the Wiener-Kintchine theorem, we also retrieve the SR power spectral density at the sample position from the measured temporal coherence function. Results are in good agreement with the measurements performed using a standard spectrometer, yielding a coherence time of 1.4 fs.