RESUMO
In the rapidly growing field of spintronics, simultaneous control of electronic and magnetic properties is essential, and the perspective of building novel phases is directly linked to the control of tuning parameters, for example, thickness and doping. Looking at the relevant effects in interface-driven spintronics, the reduced symmetry at a surface and interface corresponds to a severe modification of the overlap of electron orbitals, that is, to a change of electron hybridization. Here we report a chemically and magnetically sensitive depth-dependent analysis of two paradigmatic systems, namely La1-xSrxMnO3 and (Ga,Mn)As. Supported by cluster calculations, we find a crossover between surface and bulk in the electron hybridization/correlation and we identify a spectroscopic fingerprint of bulk metallic character and ferromagnetism versus depth. The critical thickness and the gradient of hybridization are measured, setting an intrinsic limit of 3 and 10 unit cells from the surface, respectively, for (Ga,Mn)As and La1-xSrxMnO3, for fully restoring bulk properties.
RESUMO
ULTRASPIN is an apparatus devoted to the measurement of the spin polarization (SP) of electrons ejected from solid surfaces in a UHV environment. It is designed to exploit ultrafast light sources (free electron laser or laser high harmonic generation) and to perform (photo)electron spin analysis by an arrangement of Mott scattering polarimeters that measure the full SP vector. The system consists of two interconnected UHV vessels: one for surface science sample cleaning treatments, e-beam deposition of ultrathin films, and low energy electron diffraction/AES characterization. The sample environment in the polarimeter allows for cryogenic cooling and in-operando application of electric and magnetic fields. The photoelectrons are collected by an electrostatic accelerator and transport lens that form a periaxial beam that is subsequently directed by a Y-shaped electrostatic deflector to either one of the two orthogonal Mott polarimeters. The apparatus has been designed to operate in the extreme conditions of ultraintense single-X-ray pulses as originated by free electron lasers (up to 1 kHz), but it allows also for the single electron counting mode suitable when using statistical sources such as synchrotron radiation, cw-laser, or e-gun beams (up to 150 kcps).
RESUMO
BACKGROUND: Vernal Keratoconjunctivitis (VKC) is a rare chronic ocular inflammatory disease and it mainly affects boys in the first decade of life. Although it is a self-limiting disease, patients may present many phases characterized by an exacerbation of inflammatory symptoms with a consequent decline of the quality of life. PURPOSE: define the clinical and immunological profile of patients affected by VKC and investigate their familiar history of autoimmune disorders and their autoimmunity pattern. PATIENTS AND METHODS: 28 children were enrolled (20 males, 71%) aged between 4 and 14 years of life affected by VKC. Family history of allergic and immunological diseases was collected for each patient. In particular, it was asked whether some components of their families were affected by Hashimoto's thyroiditis, type I diabetes, psoriasis or rheumatoid arthritis and Systemic Lupus Erythematosus (SLE). All VKC children underwent a serological evaluation of anti-nuclear antibodies (ANA). RESULTS: A family history of immunological disorders was found in 46% of patients, 28% of Hashimoto's thyroiditis, 14% of type I diabetes, 14% of psoriasis, and 1 of Systemic Lupus Erythematosus. Furthermore, 35% of patients was ANA positive and they corresponded to patients with a higher ocular score and with the most important clinical symptoms. CONCLUSIONS: the detection of ANA positivity and of a familiar history of autoimmune disorders in a high percentage of children with VKC may help us to better understand the association of this ocular inflammatory disease with systemic autoimmune disorders and atopic condition.
Assuntos
Autoimunidade , Conjuntivite Alérgica/imunologia , Adolescente , Anticorpos Antinucleares/análise , Criança , Pré-Escolar , Feminino , Humanos , Hipersensibilidade/imunologia , MasculinoRESUMO
Previous studies have reported a high prevalence of allergy in children with Habitual Snoring (HS), but the relationship between allergy in the early years of life and the subsequent development of this Sleep Disordered Breathing (SDB) is yet to be elucidated. The purpose of the present study was to determine the role of early, under 36 months of age, allergic sensitization to food (with or without sensitization to airborne allergens) in determining the development of HS 8-10 years after. One hundred and forty-eight children (10-14 years, mean age 12 years) with a history of food allergy were selected. Under the age of 36 months, atopic status was assessed by skin prick test for a panel of airborne and food allergens. Questionnaires filled in by parents were used to collect information on children's snoring and associated symptoms. HS was defined as snoring three or more times per week. At 1-3 years of age 54 children were positive to food allergens alone, and 94 were positive also to airborne allergens. After 8-10 years of life, when patients were aged between 10 and 14 years, habitual snoring was reported in 37 children. Furthermore, among the 54 children under three years of age sensitized only to food, 8 became HS while of the 94 children sensitized to both food and inhalants allergens 29 developed HS. The difference between those two groups was statistically significant (p=0.04). We reported a significant risk of developing HS in children with early allergic sensitization. Specifically this risk was higher when food allergy was associated with inhalant allergy. The onset of upper airway inflammation due to allergic triggers in subjects under three years of age may be related to the subsequent development of SDB after 8-10 years.