Dipolar Spin Ice States with a Fast Monopole Hopping Rate in CdEr_{2}X_{4} (X=Se, S).

Excitations in a spin ice behave as magnetic monopoles, and their population and mobility control the dynamics of a spin ice at low temperature. CdEr_{2}Se_{4} is reported to have the Pauling entropy characteristic of a spin ice, but its dynamics are three orders of magnitude faster than the canonical spin ice Dy_{2}Ti_{2}O_{7}. In this Letter we use diffuse neutron scattering to show that both CdEr_{2}Se_{4} and CdEr_{2}S_{4} support a dipolar spin ice state-the host phase for a Coulomb gas of emergent magnetic monopoles. These Coulomb gases have similar parameters to those in Dy_{2}Ti_{2}O_{7}, i.e., dilute and uncorrelated, and so cannot provide three orders faster dynamics through a larger monopole population alone. We investigate the monopole dynamics using ac susceptometry and neutron spin echo spectroscopy, and verify the crystal electric field Hamiltonian of the Er^{3+} ions using inelastic neutron scattering. A quantitative calculation of the monopole hopping rate using our Coulomb gas and crystal electric field parameters shows that the fast dynamics in CdEr_{2}X_{4} (X=Se, S) are primarily due to much faster monopole hopping. Our work suggests that CdEr_{2}X_{4} offer the possibility to study alternative spin ice ground states and dynamics, with equilibration possible at much lower temperatures than the rare earth pyrochlore examples.

Phage display peptide libraries in molecular allergology: from epitope mapping to mimotope-based immunotherapy.

Identification of allergen epitopes is a key component in proper understanding of the pathogenesis of type I allergies, for understanding cross-reactivity and for the development of mimotope immunotherapeutics. Phage particles have garnered recognition in the field of molecular allergology due to their value not only in competitive immunoscreening of peptide libraries but also as immunogenic carriers of allergen mimotopes. They integrate epitope discovery technology and immunization functions into a single platform. This article provides an overview of allergen mimotopes identified through the phage display technique. We discuss the contribution of phage display peptide libraries in determining dominant B-cell epitopes of allergens, in developing mimotope immunotherapy, in understanding cross-reactivity, and in determining IgE epitope profiles of individual patients to improve diagnostics and individualize immunotherapy. We also discuss the advantages and pitfalls of the methodology used to identify and validate the mimotopes.

[Clinical and subclinical neuropathy in patients with human immunodeficiency virus receiving antiretroviral therapy]. / Neuropatía clínica y subclínica de pacientes con virus de inmunodeficiencia humana en tratamiento antirretroviral.

INTRODUCTION: There is a clear association between human immunodeficiency virus (HIV) and peripheral neuropathy. Peripheral polyneuropathy (PPN) is the most frequent neurological complication due to both the infection itself and the neurotoxicity deriving from highly active antiretroviral therapies (HAART). AIMS: The aim of this study was to determine the incidence of symptomatic PPN associated to HAART and to find out the true prevalence rate of subclinical neuropathy following over several years' treatment. PATIENTS AND METHODS: In order to evaluate the incidence of symptomatic PPN we conducted a study of patients undergoing treatment with HAART with a combination of didanosine (ddI), lamivudine (3TC) and efavirenz, and its presence was confirmed both clinically and electromyographically. Moreover, to study the prevalence rate of asymptomatic or subclinical PPN we chose patients without PPN who had been receiving this treatment for more than two years, with a viral load that had remained undetectable for over a year and with no further risk factors for PPN, and submitted them to a voluntary electromyographic study for PPN. RESULTS: Of the 108 patients studied, only two cases of symptomatic PPN were found. CONCLUSIONS: The incidence rate of clinical neuropathy following the administration of HAART is low (1.85%); PPN is a rare cause of withdrawal. Nevertheless, the prevalence rate found for subclinical PPN in patients undergoing prolonged therapy is high (66%). We therefore find ourselves with a problem that is little known, rarely suspected and more common than is believed.