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A Nucara

Publications and source records attributed to A Nucara.

6 recordsLinked to original sources
PubMed2006

Far-infrared absorption of La1-xCaxMnO3-y at high pressure.

The first far-infrared absorption spectra of manganite samples at pressures P up to 10 GPa were obtained on La1-xCaxMnO3-y by use of synchrotron radiation. For x=0.25 and 0.20 (y=0), P promotes partial metallization at room temperature through a strong reduction of the insulating gap. An x=0.20 sample with y=0.08 does not show any charge delocalization effect up to 10 GPa. An Urbach-like model of disordered Jahn-Teller wells is shown to well fit the far-infrared band edge and allows one to obtain a reliable pressure dependence of the energy gap.

Journal Article↗
PubMed2005

A comparative EPR, infrared and Raman study of natural and deproteinated tooth enamel and dentin.

The aim of the present work was to investigate how the native signal observed in the electron paramagnetic resonance (EPR) spectrum of tooth enamel and dentin is associated with the organic content of the two tissues. This was achieved by comparing the EPR native signal and the optical bands (Raman and infrared, IR) associated with organic components of tooth enamel and dentin, in natural and deproteinated samples. The main results were: (a) in natural samples, the organic optical bands are more intense in dentin than in enamel, in contrast with the EPR native signal which shows similar intensity in the two tissues; (b) after deproteination, the optical organic bands are completely suppressed in both dentin and enamel, while the EPR native signal is eliminated only in dentin. It is suggested that the IR and Raman organic bands are originated in the bulk of the organic matrix, while the paramagnetic centres associated with the EPR native signal are located in the organic-mineral interface.

Dental Enamel↗
PubMed2000

Spectral distribution of infrared synchrotron radiation by an insertion device and its edges: A comparison between experimental and simulated spectra

The first measurements of the spectral distribution of infrared radiation emitted by an undulator are reported. They are compared with calculations including both velocity and acceleration terms. Measurements have been performed at the beam line SIRLOIN (Spectroscopie en InfraRouge Lointain). The agreement between the observations and this first exact numerical solution shows that the inclusion of the velocity term in the submillimeter frequency range is necessary. Moreover, structures due to undulator edges are observed in the far infrared and mid-infrared range, while the interference pattern due to redshifted harmonics of the undulator is dominating in the mid-infrared to near infrared.

Journal Article↗
PubMed1998

SINBAD, a brilliant IR source from the DAPhiNE storage ring.

SINBAD is the Italian IR synchrotron radiation beamline, designed to work at wavelengths greater than 10 micro m. It is being installed on DAPhiNE, a new collider that is designed to work at 0.51 GeV with a beam current up to 5 A. Due to such a high current, the IR extracted from a bending magnet will be more brilliant than that of a black body at 2000 K by two orders of magnitude at 100 micro m. The beamline optical system, projected by ray-tracing simulation, consists of six mirrors that first focus the radiation on a wedged CVD diamond-film window and then transfer the collimated beam to the experimental area where a Michelson interferometer will be installed.

Journal Article↗