Propiedades morfológicas y ópticas de nanopartículas de oro producidas o procesadas mediante técnicas láser

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de Materiales. Fecha de lectura 10-05-200

Governance of/through Big Data (vol. 2)

These two volumes collect twenty five articles and papers published within the “Governance of/through Data” research project financed by the Italian Ministry of Universities. The research project, which was promoted by Roma Tre University, as project lead, and saw the participation of professors and reseachers from Bocconi University in Milan; LUMSA University in Rome; Salento University in Lecce and Turin Polytechnic, cover multiple issues which are here presented in five sections: Algorithms and artificial intelligence; Antitrust, artificial intelligence and data; Big Data; Data governance; Data protection and privacy

Nanoparticle-doped electrospun fiber random lasers with spatially extended light modes

Complex assemblies of light-emitting polymer nanofibers with molecular materials exhibiting optical gain can lead to important advance to amorphous photonics and to random laser science and devices. In disordered mats of nanofibers, multiple scattering and waveguiding might interplay to determine localization or spreading of optical modes as well as correlation effects. Here we study electrospun fibers embedding a lasing fluorene-carbazole-fluorene molecule and doped with titania nanoparticles, which exhibit random lasing with sub-nm spectral width and threshold of about 9 mJ cm^-2 for the absorbed excitation fluence. We focus on the spatial and spectral behavior of optical modes in the disordered and non-woven networks, finding evidence for the presence of modes with very large spatial extent, up to the 100 micrometer-scale. These findings suggest emission coupling into integrated nanofiber transmission channels as effective mechanism for enhancing spectral selectivity in random lasers and correlations of light modes in the complex and disordered material.Comment: 22 pages, 6 figure

Diverse regimes of mode intensity correlation in nanofiber random lasers through nanoparticle doping

Random lasers are based on disordered materials with optical gain. These devices can exhibit either intensity or resonant feedback, relying on diffusive or interference behaviour of light, respectively, which leads to either coupling or independent operation of lasing modes. We study for the first time these regimes in complex, solid-state nanostructured materials. The number of lasing modes and their intensity correlation features are found to be tailorable in random lasers made of light-emitting, electrospun polymer fibers upon nanoparticle doping. By material engineering, directional waveguiding along the length of fibers is found to be relevant to enhance mode correlation in both intensity feedback and resonant feedback random lasing. The here reported findings can be used to establish new design rules for tuning the emission of nano-lasers and correlation properties by means of the compositional and morphological properties of complex nanostructured materials.Comment: 30 pages, 10 figure

Chronic Endometritis Due to Common Bacteria Is Prevalent in Women With Recurrent Miscarriage as Confirmed by Improved Pregnancy Outcome After Antibiotic Treatment

Recurrent miscarriage (RM) is defined as 3 or more miscarriages before 20 weeks' pregnancy. In recent years, interest has been focused on chronic endometritis (CE), a subtle inflammation thought to be associated with RM. We aimed to evaluate the relationships between CE and RM. The records of 360 women with unexplained RM were retrospectively analyzed. Data from hysteroscopy, endometrial histology, endometrial culture, and polymerase chain reaction for chlamydia, performed before and after antibiotic treatment for CE, were analyzed. The occurrence of successful pregnancies within 1 year after treatment was also evaluated. Results showed that 208 (57.8%) women with RM showed CE at hysteroscopy; 190 (91.3%), positive at hysteroscopy, were also positive at histology, and 142 (68.3%) had positive cultures. Common bacteria were found in 110 (77.5%) patients. Mycoplasma and Ureaplasma were found in 36 (25.3%) patients and Chlamydia in 18 patients (12.7%). In 102 (71%) women, antibiogram-based antibiotic treatment normalized hysteroscopy, histology, and cultures (group 1); while in 40 (28.2%) patients, CE was still present at hysteroscopy (group 2). In 16 of the 66 patients positive at hysteroscopy, but not at cultures, the hysteroscopy becomes normal (group 3) after a Centers for Disease Control and Prevention-based therapy; while in 50 women, CE was still present (group 4). One year after treatment, group 1 showed a significantly higher number of pregnancies (78.4%) compared to group 2 (17.5%; P < .001) and group 4 (15.3%; P = .005). The CE is frequent in women with RM. Antibiotic treatment seems to be associated with an improved reproductive outcome

Pulsed laser deposition of a dense and uniform Au nanoparticles layer for surface plasmon enhanced efficiency hybrid solar cells

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Polarization fields in nitride nanostructures: ten points to think about

Macroscopic polarization, both of intrinsic and piezoelectric nature, is unusually strong in III-V nitrides, and the built in electric fields in the layers of nitride-based nanostructures, stemming from polarization changes at heterointerfaces, have a major impact on the properties of single and multiple quantum wells, high mobility transistors, and thin films. The concepts involved in the theory and applications of polarization in nitrides have encountered some resistance in the field. Here we discuss critically ten ``propositions'' aimed at clarifying the main controversial issues.Comment: RevTeX 5 pages, 2 embedded figure

Localized formation and size tuning of CdS nanocrystals upon irradiation of metal precursors embedded in polymer matrices

We present a method of spatial and dimensional controlled formation of CdS quantum dots into polymer matrices by light irradiation. The initial samples consist of Cd thiolate precursors doped in TOPAS polymer matrix. Under pulsed UV laser irradiation the precursors are photolysed driving to the nucleation of CdS nanocrystals, with increasing size and concentration, related to the number of UV pulses. The formed quantum dots are localized in the irradiated area, while the host polymer remains macroscopically unaffected by the UV irradiation. In this study we investigate how the formation of the nanocrystals (size, dimensions, and concentration) is affected by the use of different irradiation conditions (wavelength, number of pulses), revealing information about the different pathways followed during the formation. The change of the size of the dots results in the change of the peak of their emission due to the quantum size effect, which is studied by fluorescence measurements. The results are reinforced by TEM microscopy and by XRD measurements. The main advantages of the presented method are the size tuning of the produced dots and their spatial confinement inside the host matrix, not possible by the other methods used until now (thermal annealing, mixing etc.)

Electronic dielectric constants of insulators by the polarization method

We discuss a non-perturbative, technically straightforward, easy-to-use, and computationally affordable method, based on polarization theory, for the calculation of the electronic dielectric constant of insulating solids at the first principles level. We apply the method to GaAs, AlAs, InN, SiC, ZnO, GaN, AlN, BeO, LiF, PbTiO$_3$, and CaTiO$_3$. The predicted \einf's agree well with those given by Density Functional Perturbation Theory (the reference theoretical treatment), and they are generally within less than 10 % of experiment.Comment: RevTeX 4 pages, 2 ps figure