Mesoporous TiO2 Thin Films: State of the Art

Mesoporous TiO2 thin films (MTTFs), thanks to their particularly high surface area, controlled porosity, high flexibility in composition, and surface design, are promising candidates in different application fields such as sensors, self-cleaning coatings, lithium-ion batteries (LIBs), photocatalysis, and new-generation solar cells. This chapter is focused on the synthetic and post-synthesis aspects that can affect the TiO2 mesoporous structure and consequently the MTTF properties. In particular, after a brief summary of TiO2 properties, all experimental conditions to prepare MTTFs are reviewed as well as the main characterization techniques employed to study their physicochemical and photocatalytic properties. An overview of the main applications of MTTFs is also proposed, mainly focused on the use of MTTFs in sensors and LIBs

An Evaluation of Researchers' Migration Patterns in Europe using Digital Trace Data

The comprehension of the mechanisms behind the mobility of skilled workers is of paramount importance for policy making. The lacking nature of official measurements motivates the use of digital trace data extracted from ORCID public records. We use such data to investigate European regions, studied at NUTS2 level, over the time horizon of 2009 to 2020. We present a novel perspective where regions roles are dictated by the overall activity of the research community, contradicting the common brain drain interpretation of the phenomenon. We find that a high mobility is usually correlated with strong university prestige, high magnitude of investments and an overall good schooling level in a region

President Obama’s Humble Face: An Authentic or a Socially Desirable Posturing? A Study on Reactions to Obama’s Autobiographical Self-Disclosures

Referring to the mainstream studies based on the personalization’s hypothesis, which positively evaluates signals of dominance shown by leaders, the analysis of Obama’s rhetoric stays a relevant exception. His risky recall, during his political talks, of his social difficulties as a child of a mixed couple was in fact one of the more surprising aspects of his success. Nevertheless, reactions to his autobiographical sharing were scarcely explored. Based on the idea that these self-disclosures signal his responsivity toward the audience of low social condition and can, therefore, be defined as a sign of humility, this research aims to test if coherence between Obama’s words and his facial expressions of contempt, due to the seriousness of social injustices endured in his childhood, may influence the receivers’ perception of such unexpected communication. Before reading a brief autobiographical sharing taken from a “Back-to-school” speech, a highly ritualized monolog the US President addresses each year to students, 175 Italian participants were presented with a photo of Obama displaying either an expression of contempt (taken from the video of the speech) or a neutral expression. Comparisons between self-assessments of perceptions and reactions of participants assigned to the two experimental conditions show that a facial expression of contempt, coherent with words describing his school difficulties, has been crucial for perceiving this humble political discourse as authentic and not as a simple socially desirable posturing. More studies seem to be needed, however, to understand how humble speech could enhance the positive face of leaders or backfire against them

Coherent x-ray wavefront reconstruction of a partially illuminated Fresnel zone plate

International audienceA detailed characterization of the coherent x-ray wavefront produced by a partially illuminated Fresnel zone plate is presented. We show, by numerical and experimental approaches, how the beam size and the focal depth are strongly influenced by the illumination conditions, while the phase of the focal spot remains constant. These results confirm that the partial illumination can be used for coherent diffraction experiments. Finally, we demonstrate the possibility of reconstructing the complex-valued illumination function by simple measurement of the far field intensity in the specific case of partial illumination

Three-dimensional high-resolution quantitative microscopy of extended crystals

International audienceHard X-ray lens-less microscopy raises hopes for a non-invasive quantitative imaging, capableof achieving the extreme resolving power demands of nanoscience. However, a limit imposedby the partial coherence of third generation synchrotron sources restricts the sample size tothe micrometer range. Recently, X-ray ptychography has been demonstrated as a solution forarbitrarily extending the fi eld of view without degrading the resolution. Here we show thatptychography, applied in the Bragg geometry, opens new perspectives for crystalline imaging.The spatial dependence of the three-dimensional Bragg peak intensity is mapped and the entiredata subsequently inverted with a Bragg-adapted phase retrieval ptychographical algorithm.We report on the image obtained from an extended crystalline sample, nanostructured froma silicon-on-insulator substrate. The possibility to retrieve, without transverse size restriction,the highly resolved three-dimensional density and displacement fi eld will allow for theunprecedented investigation of a wide variety of crystalline materials, ranging from life scienceto microelectronics

Attività di testing rapido HIV al Pride di Torino per determinare politiche strategiche e organizzative tra gli MSM

L’offerta del test HIV presso un evento sociale frequentato prevalentemente da giovani uomini che fanno sesso con uomini (MSM) fornisce una possibilità unica di intervenire nel processo di diagnosi precoce dell’HIV. Il progetto Torino Fast Track City permette di osservare elementi organizzativi utili per l’organizzazione dei test rapidi sul territorio, al tempo stesso l’adesione a COBATEST Network fornisce la possibilità di osservare un campione determinando le variabili utili per la costruzione di strategie di intervento e campagne di prevenzione. La somministrazione dei test rapidi HIV da parte delle associazioni è uno strumento chiave per incrementare il numero di soggetti che si sottopongono al test, accedono alle cure precocemente e vengono informati sulle terapie e sui possibili comportamenti a rischio

Coherent X-ray imaging of single nanowires

L'imagerie par diffraction des rayons X coh´erents (CDI) en condition de Bragg est utilis´e pour ´etudier la d´eformation de nano-objets uniques. Ceci est possible grˆace au d´eveloppement d'optique focalisante, comme les lentilles de Fresnel (FZP), produisant un faisceau sub-micronique coh´erent. Les nanostructure ´etudi´ees sont reconstruite avec des algorithmes d'inversion `a partir de donn´ees de diffraction, sous la forme d'un objet complexe, o`u l'amplitude correspond `a la densit´e ´electronique 3D et la phase correspond `a la projection de la d´eformation de l'objet (par rapport `a un r´eseau cristallin parfait) dans la direction du vecteur de diffraction. Dans ce travail, nous avons ´etudi´e la d´eformation dans des nanofils h´et´erognes (nanofil de GaAs avec une mono-couche de boˆıtes quantiques de InAs) et homog`enes (silicium fortement contraint sur isolant (sSOI)). Lorsqu'un faisceau focalis´e de rayons X est utilis´e, `a la fois l'amplitude et la phase de l'onde incidente doivent ˆetre connu pour une ´etude quantitative. Le faisceau focalis´e utilis´e pendant les exp´eriences a ´et´e recontruit avec la technique CDI, et les effets de cette fonction d'illumination sur l'imagerie de nanofils contraints ont ´et´e ´etudi´es. Mots-cl´es: Imagerie par diffraction x coh´erente, contrainte, nanofils, algorithms d'inversionThe coherent diffraction imaging technique (CDI) in Bragg condition can be used to study strain in single nanowires. This is possible due to the recent development of dedicated focusing optics, e.g. Fresnel Zone Plate (FZP), offering the possibility of focusing x-ray beams to sub-micron sizes while preserving a coherent beam. This technique allows to reconstruct (using phase retrieval algorithms) the studied nanostructure as a complex-valued density map, where the amplitude corresponds to the electronic density and the phase to the displacement of the atoms with respect to a perfect crystalline lattice projected onto the scattering vector. The application of CDI to image the strain into heterogeneous (GaAs nanowire with an insertion of 1 monolayer of quantum dots and InSb nanowire with and insertion of InP) and homogeneous highly stressed nano-structures (strained Silicon-on-Insulator lines) has been studied in this work. When using focused X-ray beams, both the amplitude and of the incoming wavefield must be known for a quantitative reconstruction. CDI has been used to reconstruct the coherent wavefield used during experiments and the effects of this illumination function for the imaging of strained nanowires have been also studied. Keywords: Coherent X-ray diffraction imaging, strain, nanowires, phase retrieval algorith

Imagerie de nanofils uniques par diffraction cohérente des rayons X

The coherent diffraction imaging technique (CDI) in Bragg condition can be used to study strain in single nanowires. This is possible due to the recent development of dedicated focusing optics, e.g. Fresnel Zone Plate (FZP), offering the possibility of focusing x-ray beams to sub-micron sizes while preserving a coherent beam. This technique allows to reconstruct (using phase retrieval algorithms) the studied nanostructure as a complex-valued density map, where the amplitude corresponds to the electronic density and the phase to the displacement of the atoms with respect to a perfect crystalline lattice projected onto the scattering vector. The application of CDI to image the strain into heterogeneous (GaAs nanowire with an insertion of 1 monolayer of quantum dots and InSb nanowire with and insertion of InP) and homogeneous highly stressed nano-structures (strained Silicon-on-Insulator lines) has been studied in this work. When using focused X-ray beams, both the amplitude and of the incoming wavefield must be known for a quantitative reconstruction. CDI has been used to reconstruct the coherent wavefield used during experiments and the effects of this illumination function for the imaging of strained nanowires have been also studied. Keywords: Coherent X-ray diffraction imaging, strain, nanowires, phase retrieval algorithmL'imagerie par diffraction des rayons X coh´erents (CDI) en condition de Bragg est utilis´e pour ´etudier la d´eformation de nano-objets uniques. Ceci est possible grˆace au d´eveloppement d'optique focalisante, comme les lentilles de Fresnel (FZP), produisant un faisceau sub-micronique coh´erent. Les nanostructure ´etudi´ees sont reconstruite avec des algorithmes d'inversion `a partir de donn´ees de diffraction, sous la forme d'un objet complexe, o`u l'amplitude correspond `a la densit´e ´electronique 3D et la phase correspond `a la projection de la d´eformation de l'objet (par rapport `a un r´eseau cristallin parfait) dans la direction du vecteur de diffraction. Dans ce travail, nous avons ´etudi´e la d´eformation dans des nanofils h´et´erognes (nanofil de GaAs avec une mono-couche de boˆıtes quantiques de InAs) et homog`enes (silicium fortement contraint sur isolant (sSOI)). Lorsqu'un faisceau focalis´e de rayons X est utilis´e, `a la fois l'amplitude et la phase de l'onde incidente doivent ˆetre connu pour une ´etude quantitative. Le faisceau focalis´e utilis´e pendant les exp´eriences a ´et´e recontruit avec la technique CDI, et les effets de cette fonction d'illumination sur l'imagerie de nanofils contraints ont ´et´e ´etudi´es. Mots-cl´es: Imagerie par diffraction x coh´erente, contrainte, nanofils, algorithms d'inversio