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249 results on '"Papagno L"'

65. Electronic structure of the K-(√3×√3)R30° on Al(111) at low and room temperature investigated by angular resolved EELS

Author

Papagno, L., Chiarello, G., Formoso, V., Santaniello, A., Cupolillo, A., and Colavita, E.

Abstract

The electronic excitations of a well ordered K-(√3×√3)R30° on Al(111) were investigated by using the angular resolved energy loss spectroscopy technique. Measurements were performed at low temperature (LT) where K atoms in the (√3×√3)R30° occupy the on-top sites and at room temperature (RT) where K atoms in (√3×√3)R30° are in substitutional sites. We found that the structural changes induce significant variation in the loss spectra. The excitation spectrum in the RT phase is ascribed to single-particle transitions involving states of the Al(111) surface with a (√3×√3)R30° vacancy structure; a new peak at 7.2 eV is interpreted as a multipole plasmon mode coming from the charge density profile predicted by calculations for the alloy surface phase. On the contrary, spectra in the LT exhibit single as well as collective excitations coming from states derived from the K adsorbate.

Published
2001
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72. Near-edge x-ray absorption fine-structure investigation of graphene

Author

Pacile, D., Papagno, M., Rodriguez, A. Fraile, Grioni, M., and Papagno, L.

Subjects
Interlayer States, Graphite, Spectra, Band-Structure, Electronic-Structure, Films
Abstract

We report the near-edge x-ray absorption fine-structure (NEXAFS) spectrum of a single layer of graphite (graphene) obtained by micromechanical cleavage of highly ordered pyrolytic graphite on a SiO2 substrate. We utilized a photoemission electron microscope to separately study single-, double-, and few-layers graphene samples. In single- layer graphene we observe a splitting of the pi* resonance and a clear signature of the predicted interlayer state. The NEXAFS data illustrate the rapid evolution of the electronic structure with the increased number of layers.

73. Prevalence of transmitted nucleoside analogue-resistant HIV-1 strains and pre-existing mutations in pol reverse transcriptase and protease region: Outcome after treatment in recently infected individuals

Author

Balotta, C., Berlusconi, A., Pan, A., Violin, M., Riva, C., Colombo, M. C., Gori, A., Papagno, L., Corvasce, S., Mazzucchelli, R., Facchi, G., Velleca, R., Saporetti, G., MASSIMO GALLI, Rusconi, S., and Moroni, M.

Subjects
Ritonavir, Genotype, Settore MED/17 - Malattie Infettive, Anti-HIV Agents, Gene Products, pol, Drug Resistance, Microbial, HIV Infections, Indinavir, HIV Reverse Transcriptase, Phenotype, Treatment Outcome, HIV Protease, Mutation, HIV-1, Humans, RNA, Viral, Reverse Transcriptase Inhibitors, Drug Therapy, Combination, Zidovudine, Retrospective Studies
Abstract

We retrospectively studied 38 Italian recently HIV-1-infected subjects who seroconverted from 1994 to 1997 to investigate: (i) the prevalence of nucleoside reverse transcriptase inhibitors (NRTI)-related mutations at primary infection; (ii) the proportion of naturally occurring mutations in reverse transcriptase (RT) and protease regions of patients naive for non-nucleoside RT inhibitors (NNRTIs) and protease inhibitors (PIs); (iii) the drug-susceptibility to NRTIs and PIs in subjects with NRTI- and/or PI-related mutations; and (iv) the outcome of seroconverters treated with various NRTIs or NRTI/PI regimens. Baseline HIV-1 plasma viraemia and absolute CD4 count at baseline could not be used to distinguish patients with NRTI- and/or PI-related pre-existing mutations from those with wild-type virus (P = 0.693 and P = 0.542, respectively). The frequency of zidovudine-related mutations was 21% in the study period. The response to treatment was not significantly different in subjects with or without genotypic zidovudine-related mutations at primary infection (P = 0.744 for HIV-1 RNA and P = 0.102 for CD4 cells). Some natural variation (2.6%) was present within regions 98-108 and 179-190 of RT involved in NNRTI resistance. The high natural polymorphism in the protease region present in our patients was similar to that reported by others. In our study some PI-associated substitutions, thought to be compensatory in protease enzymatic function, could confer intermediate to high PI-resistance. As discrepancies between genotypic and phenotypic results may exist in recent seroconverters, our data suggest that the role of transmitted NRTI- and PI-resistant variants remain to be fully elucidated in vivo.

76. Patterns of in vitro anti-human immunodeficiency virus type 1 antibody production in long-term nonprogressors

Author

Rusconi, S., Berlusconi, A., Papagno, L., Colombo, M.C., Demaddalena, C., Riva, A., Bagnarelli, P., Balotta, C., and Galli, M.

Subjects
HIV infection -- Development and progression, HIV antibodies -- Physiological aspects
Abstract

Rusconi, S.; Berlusconi, A.; Papagno, L.; Colombo, M.C.; Demaddalena, C.; Riva, A.; Bagnarelli, P.; Balotta, C.; Galli, M. "Patterns of in vitro Anti-Human Immunodeficiency Virus Type 1 Antibody Production in [...]

Published
1998

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