[en] We report zero-field ⁵⁵Mn NMR investigations of a single crystal LaMnO₃ carried out up to 90 K. The temperature dependence of the resonance frequency is compared with determinations of the staggered magnetization from μSR and neutron diffraction on the very same single crystal. Large deviations are found and discussed

[en] It is interesting to consider the problem of the presence of defects in the semiconductor binary compounds by observing their elemental tetrahedron distortions, caused by the creation of vacancies and interstitial atoms within the tetrahedra and so on. Our model thus considers the system A(Vz_xZ_1-x) and (A_1-yVa_y)Z as composed of five defect tetrahedron configurations where A is a cation atom, Z an anion atom, V_a-cation vacancy, V_z-anion vacancy. In this communication we present far infra-red (FIR) spectra obtained at the DAFNE facility of Frascati national laboratory (INFN) using its synchrotron radiation. Two samples of CdTe are considered: sample-1 was grown by the PVT technique and sample-2 using the same technique but on the basis of, polycrystalline CdTe previously purified from oxygen in hydrogen atmosphere. In this paper we have shown that FIR can register defects in crystals. (authors)

[en] This paper discusses gene expression changes in the skin of mice treated by monoenergetic 14 MeV neutron irradiation and the possibility of monitoring the resultant lipid depletion (cross-validated by functional genomic analysis) as a marker of radiation exposure by high-resolution FT-IR (Fourier transform infrared) imaging spectroscopy. The irradiation was performed at the ENEA Frascati Neutron Generator (FNG), which is specifically dedicated to biological samples. FNG is a linear electrostatic accelerator that produces up to 1.0 x 10¹¹ 14-MeV neutrons per second via the D-T nuclear reaction. The functional genomic approach was applied to four animals for each experimental condition (unirradiated, 0.2 Gy irradiation, or 1 Gy irradiation) 6 hours or 24 hours after exposure. Coregulation of a subclass of keratin and keratin-associated protein genes that are physically clustered in the mouse genome and functionally related to skin and hair follicle proliferation and differentiation was observed. Most of these genes are transiently upregulated at 6 h after the delivery of the lower dose delivered, and drastically downregulated at 24 h after the delivery of the dose of 1 Gy. In contrast, the gene coding for the leptin protein was consistently upregulated upon irradiation with both doses. Leptin is a key protein that regulates lipid accumulation in tissues, and its absence provokes obesity. The tissue analysis was performed by monitoring the accumulation and the distribution of skin lipids using FT-IR imaging spectroscopy. The overall picture indicates the differential modulation of key genes during epidermis homeostasis that leads to the activation of a self-renewal process at low doses of irradiation. (orig.)

[en] The narrow-gap II-VI and IV-VI alloys are convenient objects for studying the electron-phonon interaction. However, the concentration of free carriers in the IV-VI alloys is rather high (∼10¹⁸ cm^-3), which complicates studying this effect, by the optical reflection method. The concentration of free carriers in the narrow-gap Hg_1-xZn_xTe alloys is considerably lower (∼10¹⁶ cm^-3). Therefore, the plasma component exerts less effect on the lattice reflection spectrum. The reflection spectra of Hg_1-xZn_xTe crystals with x = 0.1-1 were studied in the far-IR region in the range of 30-700 cm^-1 at 40-300 K. Using the dispersion analysis and the Kramers-Kronig method, the frequencies of the TO phonons of the HgTe-like and ZnTe-like modes were determined depending on the composition. It is shown that the reconstructed phonon spectrum involves two modes. The temperature dependences of the frequencies of the TO phonons and the damping parameter were measured for the narrow-gap alloy with x = 0.1 in the range of 80-200 K. A decrease in the frequency of the TO phonon of the soft mode in the vicinity of the inversion point of the bands at T = 110 K was for the first time found by optical methods. The damping parameter slightly increases in the vicinity of this temperature. The result obtained qualitatively agreed with the theoretical model of Kawamura et al., which makes allowance for the effect of the electron-phonon interaction on the frequency of the soft mode in the IV-VI compounds

No abstract available

[en] The latest generation of storage rings, both light sources and colliders, needs improved diagnostics systems to achieve the challenging design parameters. Although many commercially available diagnostics can be used to characterize performance in real time, modern high-luminosity and low-emittance accelerators need much more sophisticated and sensitive diagnostics devices. DAΦNE (Double Annular Φ-Factory for Nice Experiments), the LNF (Laboratori Nazionali di Frascati) e"+/e"− Φ-factory, is a collider working at an energy of 1.02 GeV in the centre of mass. The existing luminosity diagnostics at DAΦNE cannot explain the 30% discrepancy between the extrapolated 10-bunch peak luminosity and the standard fill pattern made by colliding 100 bunches. Ruling out the presence of nonlinear contributions and/or saturation of the existing KLOE (Kaon Long Experiment) detector when used as a precision luminosity monitor, new diagnostic approaches are needed. Here we describe the technique that we introduced at DAΦNE based on multi-pixel time-resolved infrared detectors. Preliminary results are presented and discussed. (paper)

[en] Infrared spectroscopy may deliver important information on defects created in CdTe monocrystals grown from Cd and Te components purified in a hydrogen atmosphere before the crystallization process. Reflectivity spectra on different CdTe samples were collected with a FTIR spectrometer using a standard Hg lamp and the IR synchrotron radiation source of the DAFNE synchrotron facility at Frascati. In the 500-2000 cm^-1 frequency region, the characteristic vibrational spectra of oxygen and hydrogen bounded to Cd and Te in the monocrystalline CdTe were observed. Moreover the rich fine structure around the CdTe phonon frequency range has been resolved and the preliminary assignment of several lines has been performed. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] The infrared spectro microscopy is a quite recent technique rapidly developing thanks to the availability of new instruments and new brilliant synchrotron radiation sources in different areas and in particular to biomedical researches. In order to achieve a diffraction limited spatial resolution in tissue samples, we performed experiments at SINBAD, the synchrotron infrared beamline of the Laboratori Nazionali di Frascati. We characterized the chemical composition of prostate tissue samples taken from patients affected by prostate cancer disease. Different sizes of the pinholes were considered for the measurements. In the case of prostate tissue sections the results show the possibility to determine the intensity ratio of the CH₂ and CH₃ bands set at 2930 cm^-1 and 2960 cm^-1, respectively. Experiments were also performed with a pinhole of 5 μm of diameter and the differences in both histological and chemical compositions of such samples were determined. (authors)

[en] Far infrared reflection spectra of Hg_1-xZn_xTe with x=0.1 to 1 have been measured in the temperature range 40-300 K and spectral region 30-700 cm^-1. For the first time reduction of TO and coupled plasmon-LO-phonon HgTe-like modes was observed near the inversion point in the narrow-gap alloy Hg_0.9Zn_0.1Te. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

No abstract available