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The key role of interband transitions in hot-electron–modulated TiN films
Get PDFTitanium nitride (TiN) is an emerging new material in the field of plasmonics, both for its linear and nonlinear optical properties. Similarly to noble metals, like, e.g., gold (Au), the giant third-order optical nonlinearity of TiN
following excitation with fs-laser pulses has been attributed to the generation of hot electrons. Here we provide a numerical study of the Fermi smearing mechanism
associated with photogenerated hot carriers and subsequent interband transitions modulation in TiN films. A detailed comparison with Au films is also provided, and saturation effects of the permittivity modulation for increasing pump fluence are discussed
The Galileo for Science (G4S 2.0) project: Measurement of the Gravitational Redshift with the Galileo satellites DORESA and MILENA
Get PDFTheG4S2.0project represents an important opportunity to perform fundamental physics measurements with the two Galileo-FOC satellites DORESA and MILENA in elliptic orbits. In this paper, we discuss the possibility to improve the current constraints on local position invariance via a new measurement of the gravitational redshift, taking into account both a new model of the satellites and more in-depth considerations on non-gravitational perturbations
A comparison of three Fe3+ chelating agents used in Fricke gel dosimetry
Get PDF“Fricke solutions” have been used for ionizing radiation dosimetry since 1927. The system consists of an acidic solution of Fe2+ ions, which oxidize to Fe3+ upon irradiation. The addition of the Fricke solution to a tissue-equivalent hydrogel matrix allows 3D dose-mapping, that is the basis of Fricke gel dosimetry. Fricke gel dosimeters still have some drawbacks that hinder its practical usage for 3D mapping, namely signal diffusion effects and spontaneous color changes due to auto-oxidation. To limit these effects, the use of ferric ion ligands has been introduced. In this study, we compared the dosimetric optical response of Fricke gels made with xylenol orange and two alternative ligands suck us methylthymol blue and 5-sulfosalicylic acid
Photostimulation mechanism of an amphiphilic azobenzene
Get PDFThe development of new tools for controlling cell behavior is a hot argument in the scientific community, with important implications in bio-physics, medicine and the advancement of innovative biotechnology. Recently, we proposed an amphiphilic azobenzene, named Ziapin2, able to insert in the plasma membrane and modulate cell capacitance via photoisomerization. This phototransducer allows the use of light for living cell control. Here, we evaluate the dependence of the cell response on the exploited light power density. We enhance our knowledge of the stimulation mechanisms by experimental data and simulation directly correlating the cell response to the Ziapin2 photoisomerization process
i-φ-MaLe: A novel hybrid machine learning phasor-based approach to retrieve a full-set of solar-induced fluorescence metrics and biophysical parameters
Get PDFSolar-induced fluorescence (F) is crucial to monitor vegetation health, as it provides information about photosynthetic processes. Our new method, i-φ-MaLe, simultaneously estimates F spectra, Leaf Area Index (LAI), Chlorophyll Content (Cab), Absorbed Photosynthetic Active Radiation (APAR) and F Quan- tum Yield (Fqe) from canopy reflectance spectra by coupling the phasor approach with Machine Learning (ML) techniques. We validated i-φ-MaLe on simulations and spectra acquired for increasing spectrometer-canopy distances, up to 100 m (where O2 bands are affected by atmospheric oxygen absorption). The reliability of i-φ- MaLe in such complex experimental scenarios paves the way to new perspectives concerning the real time monitoring of vegetation stress status on high scales
High-sensitivity monitoring of VOCs in air via FTIR spectroscopy using a multipass gas cell setup
Get PDFThe exposure to volatile organic compounds (VOCs) constitutes a serious environmental health concern. Currently, different typologies of sensors are able to track the VOCs presence in workplaces, but they are limited in terms of chemical selectivity and sensitivity. Here, we apply Infrared (IR) spectroscopy combined to a multipass cell in order to extend the sensitivity of this technique down to the part per million (ppm) level. We calibrate the system for four compounds of interest and finally test the recognition performances on mixture of VOCs
On the transverse coherence of X-ray radiation from micron-sized electron beams
Get PDFIn this work, we investigate the transverse coherence properties of X-ray radiation from micron-sized electron beams in undulator sources. We evi- dence deviations from the well-known Van Cittert and Zernike theorem when the beam emittance becomes comparable to, or smaller than, the radiation wavelength. In these conditions, we show that the coherence properties of the emitted X-rays strongly depend on the absolute position across the observation plane and exhibit unexpected oscillations caused by the peculiar features of the single-electron ra- diation pattern. Relevance to current facilities and future fourth-generation light sources approaching the diffraction limit is also highlighted
Beyond disciplinary frontiers: The value of the history of science in teaching
Get PDF“The legitimate, safe, fruitful method, capable of preparing a mind to accept a physical hypothesis is the historical one”, argued the French theoretical physicist Pierre Duhem, in La th ́eorie physique: son objet et sa structure (1906). Starting from this position of thought, with this contribution we want to broaden our gaze to try to briefly outline an “overall conception” of the history of science, in the light of its possible declinations and its epistemological implications, beyond the disciplinary frontiers, to foster a true education of the mind or, better, to understand, according to the French style, the formative value of a philosophical history of science
A survey on Roma Tre University students' physics initial knowledge
Get PDFIn this work, we show and analyze the results of a survey that investigated the initial physics knowledge at the entrance of some scientific degree courses of Roma Tre University. In this way, we reflect on the basic knowledge possessed by students upon leaving high school, and on their scientific literacy
Entangled research methods for the building of coherent conceptual thematic learning paths and connecting research with praxis
Get PDFIn this work we present our content-research studies aimed at iden- tifying conceptual learning pathways in physics for students of different ages and for teacher education in the 30 years of research of the Udine Physics Education Re- search Unit (UPERU). They are based on the Model of Educational Reconstruction (MER) revisited by focusing on disciplinary fundamental concepts of the selected topic, aiming at conceptual change with respect to the knots that differentiate com- mon sense from scientific ideas. Learning trajectories are sought in the pathways, with tools, strategies and methods studied for the purpose. The research involves analysis of learning processes using mixed methods. Contexts are scholastic and university ones, as well as formal and non-formal, like the Games Experiments Ideas (GEI) exhibition or theaters. Attention is paid to the disciplinary content and methods that establish physics, in epistemological terms, within a basic culture and in teacher education, with specific studies on the guidance and construction of active citizenship and university teaching innovation. The topics covered are classical physics, quantum mechanics, optical, atomic, nuclear and gamma spec- troscopy, relativistic dynamics and superconductivity. For teacher education, the Metacultural-Experiential-Design-Situated (MEDS) model was developed with 20 years of experimentation