Giant magnetic anisotropy at nanoscale: overcoming the superparamagnetic limit

It has been recently observed for palladium and gold nanoparticles, that the magnetic moment at constant applied field does not change with temperature over the range comprised between 5 and 300 K. These samples with size smaller than 2.5 nm exhibit remanence up to room temperature. The permanent magnetism for so small samples up to so high temperatures has been explained as due to blocking of local magnetic moment by giant magnetic anisotropies. In this report we show, by analysing the anisotropy of thiol capped gold films, that the orbital momentum induced at the surface conduction electrons is crucial to understand the observed giant anisotropy. The orbital motion is driven by localised charge and/or spin through spin orbit interaction, that reaches extremely high values at the surfaces. The induced orbital moment gives rise to an effective field of the order of 103 T that is responsible of the giant anisotropy.Comment: 15 pages, 2 figures, submitted to PR

Surface magnetism in ZnO/Co3O4 mixtures

We recently reported the observation of room temperature ferromagnetism in mixtures of ZnO and Co3O4 despite the diamagnetic and antiferromagnetic character of these oxides respectively. Here we present a detailed study on the electronic structure of this material in order to account for this unexpected ferromagnetism. Electrostatic interactions between both oxides lead to a dispersion of Co3O4 particles over the surface of ZnO larger ones. As a consequence, the reduction of Co+3 to Co2+ at the particle surface takes place as evidenced by XAS measurements and optical spectrocopy. This reduction allows to xplain the observed ferromagnetic signal within the well established theories of magnetism.Comment: Accepted in Journal of Applied Physic

Growth-Induced In-Plane Uniaxial Anisotropy in V2_{2}O3_{3}/Ni Films

We report on a strain-induced and temperature dependent uniaxial anisotropy in V$_{2}$O$_{3}$/Ni hybrid thin films, manifested through the interfacial strain and sample microstructure, and its consequences on the angular dependent magnetization reversal. X-ray diffraction and reciprocal space maps identify the in-plane crystalline axes of the V$_{2}$O$_{3}$; atomic force and scanning electron microscopy reveal oriented rips in the film microstructure. Quasi-static magnetometry and dynamic ferromagnetic resonance measurements identify a uniaxial magnetic easy axis along the rips. Comparison with films grown on sapphire without rips shows a combined contribution from strain and microstructure in the V$_{2}$O$_{3}$/Ni films. Magnetization reversal characteristics captured by angular-dependent first order reversal curve measurements indicate a strong domain wall pinning along the direction orthogonal to the rips, inducing an angular-dependent change in the reversal mechanism. The resultant anisotropy is tunable with temperature and is most pronounced at room temperature, which is beneficial for potential device applications

Design factors that influence PCR amplification success of cross-species primers among 1147 mammalian primer pairs

BACKGROUND: Cross-species primers have been used with moderate success to address a variety of questions concerning genome structure, evolution, and gene function. However, the factors affecting their success have never been adequately addressed, particularly with respect to producing a consistent method to achieve high throughput. Using 1,147 mammalian cross-species primer pairs (1089 not previously reported), we tested several factors to determine their influence on the probability that a given target will amplify in a given species under a single amplification condition. These factors included: number of mismatches between the two species (the index species) used to identify conserved regions to which the primers were designed, GC-content of the gene and amplified region, CpG dinucleotides in the primer region, degree of encoded protein conservation, length of the primers, and the degree of evolutionary distance between the target species and the two index species. RESULTS: The amplification success rate for the cross-species primers was significantly influenced by the number of mismatches between the two index species (6–8% decrease per mismatch in a primer pair), the GC-content within the amplified region (for the dog, GC ≥ 50%, 56.9% amplified; GC<50%, 74.2% amplified), the degree of protein conservation (R(2 )= 0.14) and the relatedness of the target species to the index species. For the dog, 598 products of 930 primer pairs (64.3%) (excluding primers in which dog was an index species) were sequenced and shown to be the expected product, with an additional three percent producing the incorrect sequence. When hamster DNA was used with the single amplification condition in a microtiter plate-based format, 510 of 1087 primer pairs (46.9%) produced amplified products. The primer pairs are spaced at an average distance of 2.3 Mb in the human genome and may be used to produce up to several hundred thousand bp of species-specific sequence. CONCLUSION: The most important factors influencing the proportion of successful amplifications are the number of index species mismatches, GC-richness of the target amplimer, and the relatedness of the target species to the index species, at least under the single PCR condition used. The 1147 cross-species primer pairs can be used in a high throughput manner to generate data for studies on the genetics and genomics of non-sequenced mammalian genomes

Room-temperature ferromagnetism in the mixtures of the TiO₂ and Co₃O₄ powders

We report here the observation of ferromagnetism (FM) at 300 K in mixtures of TiO₂ and Co₃O₄ powders despite the antiferromagnetic and diamagnetic characters of both oxides, respectively. The ferromagnetic behavior is found in the early stages of reaction and only for TiO₂ in anatase structure; no FM is found for identical samples prepared with rutile-TiO². Optical spectroscopy and x-ray absorption spectra confirm a surface reduction of octahedral Co^(+3) -> Co^(+2) in the mixtures which is in the origin of the observed magnetism

Theory of Mind and Emotion Regulation Difficulties in Adolescents With Borderline Traits

Objective: Dysfunctions in both emotion regulation and social cognition (understanding behavior in mental state terms, theory of mind or mentalizing) have been proposed as explanations for disturbances of interpersonal behavior in borderline personality disorder (BPD). This study aimed to examine mentalizing in adolescents with emerging BPD from a dimensional and categorical point of view, controlling for gender, age, Axis I and Axis II symptoms, and to explore the mediating role of emotion regulation in the relation between theory of mind and borderline traits. Method: The newly developed Movie for the Assessment of Social Cognition (MASC) was administered alongside self-report measures of emotion regulation and psychopathology to 111 adolescent inpatients between the ages of 12 to 17 (mean age = 15.5 years; SD = 1.44 years). For categorical analyses borderline diagnosis was determined through semi-structured clinical interview, which showed that 23% of the sample met criteria for BPD. Results: Findings suggest a relationship between borderline traits and "hypermentalizing" (excessive, inaccurate mentalizing) independent of age, gender, externalizing, internalizing and psychopathy symptoms. The relation between hypermentalizing and BPD traits was partially mediated by difficulties in emotion regulation, accounting for 43.5% of the hypermentalizing to BPD path. Conclusions: Results suggest that in adolescents with borderline personality features the loss of mentalization is more apparent in the emergence of unusual alternative strategies (hypermentalizing) than in the loss of the capacity per se (no mentalizing or undermentalizing). Moreover, for the first time, empirical evidence is provided to support the notion that mentalizing exerts its influence on borderline traits through the mediating role of emotion dysregulation. J. Am. Acad. Child Adolesc. Psychiatry, 2011;50(6): 563-573

First empirical evaluation of the link between attachment, social cognition and borderline features in adolescents

OBJECTIVE: Several developmental models of borderline personality disorder (BPD) emphasize the role of disrupted interpersonal relationships or insecure attachment. As yet, attachment quality and the mechanisms by which insecure attachment relates to borderline features in adolescents have not been investigated. In this study, we used a multiple mediational approach to examine the cross-sectional interplay between attachment, social cognition (in particular hypermentalizing), emotion dysregulation, and borderline features in adolescence, controlling for internalizing and externalizing symptoms. METHODS: The sample included 259 consecutive admissions to an adolescent inpatient unit (Mage=15.42, SD=1.43; 63.1% female). The Child Attachment Interview (CAI) was used to obtain a dimensional index of overall coherence of the attachment narrative. An experimental task was used to assess hypermentalizing, alongside self-report measures of emotion dyregulation and BPD. RESULTS: Our findings suggested that, in a multiple mediation model, hypermentalizing and emotion dysregulation together mediated the relation between attachment coherence and borderline features, but that this effect was driven by hypermentalizing; that is, emotion dysregulation failed to mediate the link between attachment coherence and borderline features while hypermentalizing demonstrated mediational effects. CONCLUSIONS: The study provides the first empirical evidence of well-established theoretical approaches to the development of BPD