85 research outputs found
Experimental Evidence For Self-Similar Structures In The Aggregation Of Porphyrins In Aqueous Solutions
We have studied the aggregation of the porphyrin t-H₂Pagg in aqueous solution by light scattering. The intensity profile of the elastically scattered light, studied in the exchanged wave-vector range 0.2 ≤ q ≤ 31.4 μ m⁻¹, indicates that the aggregation produces large monodisperse clusters having a fractal structure, and is driven by diffusion-limited aggregation kinetics. Additional measurements performed at different q values confirm such a picture giving a hydrodynamic radius R(H) consistent with the radius of gyration R(g) measured by elastic scattering. This is explained taking into account the q² dependence observed in the mean decay rate of the intensity-intensity correlation function and the effect on this latter dynamical quantity of anisotropies in the cluster structure
Laser Controlled Synthesis of Noble Metal Nanoparticle Arrays for Low Concentration Molecule Recognition
Nanostructured gold and silver thin films were grown by pulsed laser deposition. Performing the process in an ambient gas (Ar) leads to the nucleation and growth of nanoparticles in the ablation plasma and their self-organization on the substrate. The dependence of surface nanostructuring of the films on the deposition parameters is discussed considering in particular the number of laser pulses and the ambient gas nature and pressure. The performance of the deposited thin films as substrates for surface-enhanced Raman spectroscopy (SERS) was tested against the detection of molecules at a low concentration. Taking Raman maps on micrometer-sized areas, the spatial homogeneity of the substrates with respect to the SERS signal was tested
Stabilization of mid-sized silicon nanoparticles by functionalization with acrylic acid
We present an enhanced method to form stable dispersions of medium-sized silicon nanoparticles for solar cell applications by thermally induced grafting of acrylic acid to the nanoparticle surface. In order to confirm their covalent attachment on the silicon nanoparticles and to assess the quality of the functionalization, X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier spectroscopy measurements were carried out. The stability of the dispersion was elucidated by dynamic light scattering and Zeta-potential measurements, showing no sign of degradation for months
Time-of-Flight Neutron Imaging on IMAT@ISIS: A New User Facility for Materials Science
The cold neutron imaging and diffraction instrument IMAT at the second target station of the pulsed neutron source ISIS is currently being commissioned and prepared for user operation. IMAT will enable white-beam neutron radiography and tomography. One of the benefits of operating on a pulsed source is to determine the neutron energy via a time of flight measurement, thus enabling energy-selective and energy-dispersive neutron imaging, for maximizing image contrasts between given materials and for mapping structure and microstructure properties. We survey the hardware and software components for data collection and image analysis on IMAT, and provide a step-by-step procedure for operating the instrument for energy-dispersive imaging using a two-phase metal test object as an example
Bilingualism in university students: further evidence of metalinguistic benefits
This empirical study aims at assessing metalinguistic abilities in Italian-English bilinguals compared to both Italian and English monolinguals. 40 University students (age range: 20-29 y.-old), enrolled in humanistic studies, of middle class background, were recruited partly in Italy and partly in UK. They were all administered a subtest of a metalinguistic ability test devised for adults, the subtest Comprehension, existing in Italian and in English version. Results showed significant metalinguistic superiority of bilinguals over monolinguals in the most complex, type of responsesm although English monolinguals outperformed Italian monolinguals. No differences appeared between simultaneous and consecutive bilinguals
Propagation of laser generated plasmas through inert gases
AbstractA fast photo imaging technique has been used to characterize the expansion dynamics of a laser generated silver plasma propagating through background inert gases (He and Ar) at different pressures. The time evolution of the expanding plasma was investigated in the framework of currently available phenomenological models. Mixed-propagation model gives an accurate description of the initial and late plasma expansion stages in Ar when proper input parameters are taken into account. In He, only the initial quasi-linear expansion and shock wave formation were observed along the space available to plasma motion
Metalinguistic abilities in Italian-English adult bilinguals . A comparison with Italian-speaking and English-speaking monolinguals.
This empirical research studies long-term effects of different types of early biligualism on metalinguistic abilities at young adult age. A sample of 40 university students has been recruited and subdivided into a bilingual Italian-English group and a monolingual group, itself subdivided into Italian monolinguals, tested in Italy, and English monolinguals, tested in UK. Students received a metalinguistic ability test specific for adults (TAM-3, Pinto, Iliceto, 2007), existing also in English version. Bilinguals, as a whole, significantly ourperformed monolinguals, and monolinguals of either type performed at very similar level, irrespective of the linguistic version of the test
METALINGUISTIC AWARENESS. THEORY, DEVELOPMENT AND MEASUREMENT INSTRUMENTS
The book presents an overview on the concept of metalinguistic awareness from a theoretical linguistic, developmental, and applied perspective and then describes three tests for assessing metalinguistic awareness from 4 years-old to adult age
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