84 research outputs found
Exchange Anisotropy in Epitaxial and Polycrystalline NiO/NiFe Bilayers
(001) oriented NiO/NiFe bilayers were grown on single crystal MgO (001)
substrates by ion beam sputtering in order to determine the effect that the
crystalline orientation of the NiO antiferromagnetic layer has on the
magnetization curve of the NiFe ferromagnetic layer. Simple models predict no
exchange anisotropy for the (001)-oriented surface, which in its bulk
termination is magnetically compensated. Nonetheless exchange anisotropy is
present in the epitaxial films, although it is approximately half as large as
in polycrystalline films that were grown simultaneously. Experiments show that
differences in exchange field and coercivity between polycrystalline and
epitaxial NiFe/NiO bilayers couples arise due to variations in induced surface
anisotropy and not from differences in the degree of compensation of the
terminating NiO plane. Implications of these observations for models of induced
exchange anisotropy in NiO/NiFe bilayer couples will be discussed.Comment: 23 pages in RevTex format, submitted to Phys Rev B
From bi-layer to tri-layer Fe nanoislands on Cu3Au(001)
Self assembly on suitably chosen substrates is a well exploited root to
control the structure and morphology, hence magnetization, of metal films. In
particular, the Cu3Au(001) surface has been recently singled out as a good
template to grow high spin Fe phases, due to the close matching between the
Cu3Au lattice constant (3.75 Angstrom) and the equilibrium lattice constant for
fcc ferromagnetic Fe (3.65 Angstrom). Growth proceeds almost layer by layer at
room temperature, with a small amount of Au segregation in the early stage of
deposition. Islands of 1-2 nm lateral size and double layer height are formed
when 1 monolayer of Fe is deposited on Cu3Au(001) at low temperature. We used
the PhotoElectron Diffraction technique to investigate the atomic structure and
chemical composition of these nanoislands just after the deposition at 140 K
and after annealing at 400 K. We show that only bi-layer islands are formed at
low temperature, without any surface segregation. After annealing, the Fe atoms
are re-aggregated to form mainly tri-layer islands. Surface segregation is
shown to be inhibited also after the annealing process. The implications for
the film magnetic properties and the growth model are discussed.Comment: Revtex, 5 pages with 4 eps figure
Structure of ultrathin films of Co on Cu(111) from normal-incidence x-ray standing wave and medium-energy ion scattering measurements
Abnormal amygdala activation profile in pedophilia
Despite considerable public interest research in neurobiological correlates of pedophilia is scarce. Since amygdala activation is central for emotional valuation, arousal, and salience, we investigated the activation profile of this structure in 10 male subjects with pedophilia (exclusively attracted to boys), all convicted sex-offenders and sentenced to forensic psychiatric treatment along with ten male heterosexual matched controls. We used a sexually non-explicit functional Magnetic Resonance Imaging (fMRI) paradigm with images of men, women, boys or girls randomly embedded in neutral target/non-target geometrical symbols. We applied statistical parametric mapping (SPM2) and SPSS 14 for image processing and analysis. While controls activated significantly less to pictures of children compared to adults, the activation profile was reversed in subjects with pedophilia, who exhibited significantly more activation to children than adults. The highest activation was observed for boys in the patient group, and for women in control participants. Our data show enhanced activation to children's pictures even in an incidental context and suggest the provocative hypothesis that a normally present mechanism for reduced emotional arousal for children relative to adults is reversed in pedophilia, suggesting a neural substrate associated with deviant sexual preference in this condition. More extensive research in this field would be of benefit for both the victims and the offenders
La Campana de Gracia: Any L Batallada 2601 - 1919 febrero 15
Some pathological manifestations of diabetes in the eye include retinopathy, cataracts and elevated intraocular pressure (IOP). Loss of retinal ganglion cells (RGCs) in non-proliferative stages of diabetic retinopathy and small increases in IOP in diabetic patients has raised the possibility that diabetes affects the development and progression of ocular hypertension and glaucoma. The Ins2Akita mutation is known to cause diabetes and retinopathy on a C57BL/6J (B6) background by as early as 3 months of age. Here, the impact of the Akita mutation on glaucoma was assessed using DBA/2J (D2) mice, a widely used mouse model of ocular hypertension induced glaucoma. In D2.Ins2Akita/+ mice, the contribution of diabetes to vascular permeability, IOP elevation, RGC loss, and glaucoma development was assessed. D2.Ins2Akita/+ mice developed a severe diabetic nephropathy and early mortality between 6-8 months of age. This agrees with previous reports showing that the D2 background is more susceptible to diabetes than the B6 background. In addition, D2.Ins2Akita/+ mice had vascular leakage, astrocyte reactivity and a significant increase in IOP. However no RGC loss and no anterograde axonal transport dysfunction were found at 8.5 months of age. Therefore, our data show that despite severe diabetes and an increased IOP compared to controls, RGCs do not lose axon transport or degenerate. This may be due to a DBA/2J-specific genetic modifier(s) that could provide novel and important avenues for developing new therapies for diabetic retinopathy and possibly glaucoma
Stress determination and magnetization reversal detection in FeSiAl(N) films using magnetic force microscopy with in-plane magnetic field capability
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