Understanding magnetic hyperthermia performance within the "Brezovich criterion": beyond the uniaxial anisotropy description.

Careful determination of the heating performance of magnetic nanoparticles under AC fields is critical for magnetic hyperthermia applications. However, most interpretations of experimental data are based on the uniaxial anisotropy approximation, which in the first instance can be correlated with the particle aspect ratio. This is to say, the intrinsic magnetocrystalline anisotropy is discarded, under the assumption that the shape contribution dominates. We show in this work that such a premise, generally valid for large field amplitudes, does not hold for describing hyperthermia experiments carried out under small field values. Specifically, given its relevance for in vivo applications, we focus our analysis on the so-called "Brezovich criterion", H·f = 4.85 × 108 A m-1 s-1. By means of a computational model, we show that the intrinsic magnetocrystalline anisotropy plays a critical role in defining the heat output, determining also the role of the shape and aspect ratio of the particles on the SLP. Our results indicate that even small deviations from spherical shape have an important impact on optimizing the heating performance. The influence of interparticle interactions on the dissipated heat is also evaluated. Our results call, therefore, for an improvement in the theoretical models used to interpret magnetic hyperthermia performance.

Lipoatrofia semicircular en trabajadores de oficinas: una situación que no desaparece tan rápidamente / Semicircular lipoatrophy in public office workers. A situation that does not disappear so quickly

Introducción: La lipoatrofia semicircular (LS) es un trastorno caracterizado por depresiones en forma de banda en la cara anterolateral de los muslos. Objetivos: determinar la prevalencia de los casos de LS en varias instituciones públicas y privadas de la Provincia de Barcelona, España. Material y Métodos: se realizó estudio retrospectivo, en 969 trabajadores de oficinas públicas y privadas, entre 2018 y 2022. A todos los casos se les realizó examen físico completo con mediciones, fotografía y seguimiento de las lesiones. Los resultados fueron analizados mediante el programa Instat Graphpad 3.10 y se aplicó la prueba de Fischer para determinar la significancia estadística. Resultados: se diagnosticaron 96 casos de los cuales 92 eran mujeres. Prevalencia: 9,9%. El promedio de edad fue 49 años (27-64). La mayoría de las lesiones se localizaron en los muslos en forma bilateral. Las lesiones de LS al final del estudio no desaparecieron en el 60% de los casos, mientras que en un 40% si lo hicieron. Conclusiones: Las lesiones de LS toman un tiempo muy variable para revertir, suele ser un proceso lento cuya duración se mide habitualmente en años. Ni el teletrabajo, ni el índice de masa corporal, tuvieron relación estadísticamente significativa en la desaparición de las lesiones. (AU)

Introduction: Semicircular lipoatrophy (LS) is a disorder characterized by band-shaped depressions on the anterolateral aspect of the thighs. Objectives: to determine the prevalence of LS cases in various public and private institutions in the Province of Barcelona, Spain. Material and Methods: a retrospective study was carried out on 969 workers from public and private offices, between 2018 and 2022. All cases underwent a complete physical examination with measurements, photography, and follow-up of injuries. The results were analyzed using the Instat Graphpad 3.10 program and the Fischer test was applied to determine statistical significance. Results: 96 cases were diagnosed, of which 92 were women. Prevalence: 9.9%. The average age was 49 years (27-64). Most of the lesions were located on the thighs bilaterally. LS lesions at the end of the study did not disappear in 60% of cases, while in 40% they did. Conclusions: LS lesions take a highly variable time to reverse, it is usually a slow process whose duration is usually measured in years. Neither teleworking nor the body mass index had a statistically significant relationship in the disappearance of the lesions (AU)

Predictive value of CDKN2A/p16INK4a expression in the malignant transformation of oral potentially malignant disorders: Systematic review and meta-analysis.

BACKGROUND: Management of oral potentially malignant disorders (OPMDs) is still challenging. Despite the diagnostic ascertainment by bioptic examination, this method is poorly informative of the prognosis and subsequent malignant transformation. Prognosis is based on histological findings by grading of dysplasia. Immunohistochemical expression of p16INK4a has been investigated in different studies, with controversial results. In this scenario, we systematically revised the current evidence about p16INK4a immunohistochemical expression and the risk of malignization of OPMDs. MATERIAL AND METHODS: After a proper set of keywords combination, 5 databases were accessed and screened to select eligible studies. The protocol was previously registered on PROSPERO (Protocol ID: CRD42022355931). Data were obtained directly from the primary studies as a measure to determine the relationship between CDKN2A/P16INK4a expression and the malignant transformation of OPMDs. Heterogeneity and publication bias were investigated by different tools, such as Cochran's Q test, Galbraith plot and Egger and Begg Mazumdar's rank tests. RESULTS: Meta-analysis revealed a twofold increased risk to malignant development (RR = 2.01, 95% CI = 1.36-2.96 - I2 = 0%). Subgroup analysis did not highlight any relevant heterogeneity. Galbraith plot showed that no individual study could be considered as an important outlier. CONCLUSION: Pooled analysis showed that p16INK4a assessment may arise adjunct tool to dysplasia grading, leading to an optimized determination of the potential progression to cancer of OPMDs. The p16INK4a overexpression analysis by immunohistochemistry techniques has a multitude of virtues that may facilitate its incorporation in the day-to-day prognostic study of OPMDs.

Linfoma primario de base de cráneo presentándose como oftalmoplejia aguda / Primary skull base lynphoma presenting as acute ophtalmoplegia

Primary Skull base lymphoma (PSBL) represents a rare manifestation of extranodal lymphoma. Aggressive non-Hodgkin´s lymphoma such as diffuse large B-cell lymphoma, constitute the most commonly encountered subtype of PBSL. We report the case of a 70-year-oldwoman with acute diplopia and ptosis of the right eye. Neurological examination showed palsy of right III, IV and VI cranial nerves. Brain imaging studies showed a lesion showed invading the floor of the sella turcica, both cavernous sinuses, the clivus and part of the sphenoid sinus. The patient underwent endonasal endoscopic resection of the lesion. The histological diagnosis was diffuse large B-cell lymphoma. No systemic disease was found on staging the patient. (AU)

El linfoma primario de base de cráneo (LPBC) representa una variante poco frecuente del linfoma extranodal. Los linfomas no-Hodgkin agresivos, tales como el linfoma difuso de células grandes B son el subtipo más frecuente que se presentan como LPBC. Describimos el caso de una paciente mujer de 70 años que acude a nuestro centro con una clínica aguda de diplopía y posterior ptosis del ojo derecho. En la exploración neurológica se constató parálisis de III, IV y VI pares derechos. Los estudios de imagen cerebral mostraron una lesión que invadía el suelo de la silla turca, ambos senos cavernosos, el clivus y parte del seno esfenoidal. Se realizó una exéresis endoscópica endonasal de la lesión. El examen histológico de la lesión fue compatible con un linfoma difuso de células grandes B. No se constató enfermedad sistémica en los estudios de extensión. (AU)

Overexpression of E-Cadherin Is a Favorable Prognostic Biomarker in Oral Squamous Cell Carcinoma: A Systematic Review and Meta-Analysis.

Oral squamous cell carcinoma (OSCC) is characterized by poor survival, mostly due to local invasion, loco-regional recurrence, and metastasis. Given that the weakening of cell-to-cell adhesion is a feature associated with the migration and invasion of cancer cells, different studies have explored the prognostic utility of cell adhesion molecules such as E-cadherin (E-cad). This study aims to summarize current evidence in a meta-analysis, focusing on the prognostic role of E-cad in OSCC. To find studies meeting inclusion criteria, Scopus, Web of Science, EMBASE, Medline, and OpenGrey databases were systematically assessed and screened. The selection process led to 25 studies, which were considered eligible for inclusion in the meta-analysis, representing a sample of 2553 patients. E-cad overexpression was strongly associated with longer overall survival (OS) with Hazard Ratio (HR) = 0.41 95% confidence interval (95% CI) (0.32-0.54); p < 0.001 and disease-free survival with HR 0.47 95% CI (0.37-0.61); p < 0.001. In terms of OS, patients with tongue cancer experienced better survivability when expressing E-cad with HR 0.28 95% CI (0.19-0.43); p < 0.001. Globally, our findings indicate the prognostic role of the immunohistochemical assessment of E-cad in OSCC and its expression might acquire a different role based on the oral cavity subsites.

Oral Chronic Hyperplastic Candidiasis and Its Potential Risk of Malignant Transformation: A Systematic Review and Prevalence Meta-Analysis.

Chronic hyperplastic candidiasis (CHC) is a prototypical oral lesion caused by chronic Candida infection. A major controversy surrounding CHC is whether this oral lesion owns malignant transformation (MT) potential. The aim of the present study was to evaluate current evidence on the MT of CHC and to determine the variables which have the greatest influence on cancer development. Bibliographical searches included PubMed, Embase, Web of Science, Scopus and LILACS. The cohort studies and case series used to investigate the MT of CHC were deemed suitable for inclusion. The quality of the enrolled studies was measured by the Joanna Briggs Institute scale. Moreover, we undertook subgroup analyses, assessed small study effects, and conducted sensitivity analyses. From 338 studies, nine were finally included for qualitative/quantitative analysis. The overall MT rate for CHC across all studies was 12.1% (95% confidential interval, 4.1-19.8%). Subgroup analysis showed that the MT rate increased when pooled analysis was restricted to poor quality studies. It remains complex to affirm whether CHC is an individual and oral, potentially malignant disorder according to the retrieved evidence. Prospective cohort studies to define the natural history of CHC and a consensus statement to clarify a proper set of diagnostic criteria are strongly needed. PROSPERO ID: CRD42022319572.

Dependence of Exchange Bias on Interparticle Interactions in Co/CoO Core/Shell Nanostructures.

This article reports the dependence of exchange bias (EB) effect on interparticle interactions in nanocrystalline Co/CoO core/shell structures, synthesized using the conventional sol-gel technique. Analysis via powder X-Ray diffraction (PXRD) studies and transmission electron microscope (TEM) images confirm the presence of crystalline phases of core/shell Co/CoO with average particle size ≈ 18 nm. Volume fraction (φ) is varied (from 20% to 1%) by the introduction of a stoichiometric amount of non-magnetic amorphous silica matrix (SiO2) which leads to a change in interparticle interaction (separation). The influence of exchange and dipolar interactions on the EB effect, caused by the variation in interparticle interaction (separation) is studied for a series of Co/CoO core/shell nanoparticle systems. Studies of thermal variation of magnetization (M-T) and magnetic hysteresis loops (M-H) for the series point towards strong dependence of magnetic properties on dipolar interaction in concentrated assemblies whereas individual nanoparticle response is dominant in isolated nanoparticle systems. The analysis of the EB effect reveals a monotonic increase of coercivity (HC) and EB field (HE) with increasing volume fraction. When the nanoparticles are close enough and the interparticle interaction is significant, collective behavior leads to an increase in the effective antiferromagnetic (AFM) CoO shell thickness which results in high HC and HE. Moreover, in concentrated assemblies, the dipolar field superposes to the local exchange field and enhances the EB effect contributing as an additional source of unidirectional anisotropy.

Self-reported depression and anxiety among COPD patients. A case-control study.

BACKGROUND: Anxiety and depression are the most prevalent mental disorders worldwide. However, the exact mechanisms linking chronic obstructive pulmonary disease (COPD) with depression and anxiety have not been identified. OBJECTIVES: To compare self-reported depression and anxiety among patients diagnosed with COPD in relation to healthy controls. DESIGN AND SETTING: Case control study at a public hospital institution in Spain. METHODS: We designed a case-control study. Patients were recruited using a consecutive sampling method from a single institution. Two groups were created: COPD and healthy controls. Data on medical history and demographic background were collected from the medical records. Self-reported depression levels were assessed using Beck's depression inventory (BDI). Self-reported anxiety was measured using the State-trait anxiety inventory (STAI). RESULTS: Fifty-two patients with COPD and fifty healthy patients were included in this study. BDI scores were higher for COPD patients (10.23 ± 6.26) than in the control group (5.2 ± 6.56). STAI-state scores were higher for COPD patients (41.85 ± 12.55) than for controls (34.88 ± 9.25). STAI-trait scores were higher for COPD patients (41.42 ± 10.01) than for controls (34.62 ± 9.19). CONCLUSIONS: This study showed that there were higher levels of depression and anxiety among COPD patients than among healthy controls.

Self-reported depression and anxiety among COPD patients. A case-control study

Abstract BACKGROUND: Anxiety and depression are the most prevalent mental disorders worldwide. However, the exact mechanisms linking chronic obstructive pulmonary disease (COPD) with depression and anxiety have not been identified. OBJECTIVES: To compare self-reported depression and anxiety among patients diagnosed with COPD in relation to healthy controls. DESIGN AND SETTING: Case control study at a public hospital institution in Spain. METHODS: We designed a case-control study. Patients were recruited using a consecutive sampling method from a single institution. Two groups were created: COPD and healthy controls. Data on medical history and demographic background were collected from the medical records. Self-reported depression levels were assessed using Beck's depression inventory (BDI). Self-reported anxiety was measured using the State-trait anxiety inventory (STAI). RESULTS: Fifty-two patients with COPD and fifty healthy patients were included in this study. BDI scores were higher for COPD patients (10.23 ± 6.26) than in the control group (5.2 ± 6.56). STAI-state scores were higher for COPD patients (41.85 ± 12.55) than for controls (34.88 ± 9.25). STAI-trait scores were higher for COPD patients (41.42 ± 10.01) than for controls (34.62 ± 9.19). CONCLUSIONS: This study showed that there were higher levels of depression and anxiety among COPD patients than among healthy controls.

Asthma, much more than a respiratory disease: influence of depression and anxiety.

OBJECTIVE: The goals of this study are to compare self-reported depression and anxiety in subjects diagnosed of asthma and healthy controls. METHODS: We designed a case-control study. Subjects were recruited using a consecutive sampling method from a single institution. Two groups were created: Asthma and healthy controls. Data of medical history and demographic background were collected from the medical record. Self-reported depression level was assessed using Beck's depression inventory (BDI). Self-reported anxiety was measured with the "State-trait anxiety inventory" (STAI). RESULTS: Fifty-one subjects with asthma, and fifty healthy patients were included in this study. BDI scores (p<0.001) were higher for asthma (10.22±7.3) than in the control group (5.2±6.56). STAI state (p<0.001) was higher in asthma (42.61±11.5) than in controls (34.88±9.25). STAI trait (p<0.001) showed higher scores in asthma (43.14±10.89) than in controls (34.62±9.19). CONCLUSIONS: These study findings showed that BDI, and STAI trait and state scores are significantly higher in subjects who suffer from asthma than healthy controls.

The role of cortical perforations in allogeneic block grafting for lateral augmentation in maxilla: A randomized clinical trial.

BACKGROUND: The need of decortication on the recipient site remains unclear for bone regeneration. To our knowledge, there are no human clinical trials that studied the influence of decortication on cancellous allogeneic block grafting. PURPOSE: The aim of the present study is to evaluate the influence of perforating the cortex of the recipient site on cancellous allogeneic block graft integration and revascularization in the maxilla. MATERIAL AND METHODS: Twenty-six patients referred for lateral bone augmentation were included in this clinical trial. Patients received freeze-dried bone allograft cancellous blocks obtained from the iliac crest; cortical perforations of the recipient bed were performed in the test group while in the control group it was left intact. After a 4-month healing period another surgery was performed to place dental implants, and a bone biopsy was collected using a trephine. All samples underwent micro-CT scans, and were processed for histomorphometric and immunohistochemical analysis. Implant survival comparisons were made using a repeated measures analysis of variance (ANOVA) while all other variables were compared using the analysis of covariance (ANCOVA). RESULTS: One hundred and nineteen implants were placed into 110 augmented sites. One hundred percent implant survival rate was reported during 24 months follow-up period. No differences were reported in bleeding on probing at 1 (5.6 vs 9%) and 2 years (13.2 vs 12.1%), probing pocket depth at 1 (3.4 ± 0.95 vs 3.6 ± 1.12 mm) and 2 years (3.8 ± 1.02 vs 4.1 ± 1.46 mm), and marginal bone loss at 1 (0.2 ± 0.52 vs 0.3 ± 0.57 mm) and 2 years (0.6 ± 0.91 vs 0.5 ± 0.87 mm). No statistically significant differences were found in the micro-CT and histomorphometric analysis in terms of newly formed bone (25.7 ± 11.2% vs 22.3 ± 9.7%), soft tissue (33.0 ± 14.7% vs 36.5 ± 15.7%), remnant allograft (39.3 ± 20.4% vs 41.2 ± 22.7%), and bone mineralization (57.2 ± 10.6% vs 53.8 ± 8.7%). Perforating the cortex of the recipient site had no significant effect on angiogenesis as shown by immunohistochemical analysis of CD34 positive blood vessels (39.21 ± 10.53/mm2 vs 34.16 ± 12.67/mm2 ). CONCLUSION: Cancellous allogeneic bone block grafts are a clinically acceptable alternative for horizontal bone augmentation. Cortical perforations of the recipient site in the maxilla did not improve angiogenesis nor bone formation within the block graft.

Lipoatrofia semicircular en trabajadores de oficinas públicas / Semicircular Lipoatrophy in Public Office Workers

Introducción: La lipoatrofia semicircular (LS) es un trastorno benigno del tejido subcutáneo, de causa no bien conocida, caracterizada por depresiones semicirculares en la cara anterolateral de los muslos y menos frecuentemente en abdomen o brazos. Método: Estudio observacional, prospectivo, longitudinal, en 449 trabajadores de oficina, localizados en varios edificios de la ciudad de Castelldefels, Provincia de Barcelona, España, entre julio 2018 y abril 2021 a los que se les realizó identificación, mediciones, fotografía y controles periódicos de la LS. Los resultados fueron analizados mediante el programa Instat Graphpad y se aplicó la prueba de Fischer para determinar la significancia estadística. Resultados: Se diagnosticaron 74 casos de LS en un total de 449 trabajadores. Prevalencia: 16,48%. De los 74 casos identificados, 71 eran mujeres (95,9%). El promedio de edad fue 49,18 años (27-64). La mayoría de las lesiones se localizaron en los muslos en forma bilateral. Las lesiones de LS no desaparecieron en el 66,6% de los casos, mientras que en un 33,3% si lo hicieron. El teletrabajo y el índice de masa corporal no resultaron factores significativos en la desaparición de las lesiones. Conclusiones: La LS es una alteración infrecuente del tejido subcutáneo, en la que influyen una serie de factores que van desde el medio laboral, la susceptibilidad individual y el sexo femenino. La LS toma un tiempo muy variable para revertir, suele ser un proceso lento cuya duración se mide en años más que en meses. Ni el teletrabajo, ni el índice de masa corporal, tuvieron una relación estadísticamente significativa en la desaparición de las lesiones en esta serie. (AU)

Introduction: Semicircular lipoatrophy (LS) is a benign disorder of the subcutaneous tissue, of unknown cause, characterized by semicircular depressions on the anterolateral aspect of the thighs and less frequently in the abdomen or arms. Method: Observational, prospective, longitudinal study, in 449 office workers, from the same public institution, located in various buildings in the city of Castelldefels, Province of Barcelona, Spain, between July 2018 and April 2021 at that identification, measurements, photography and periodic controls of the LS were carried out. The results were analyzed using the Instat Graphpad program and the Fischer test was applied to determine statistical significance. Results: 74 cases of LS were diagnosed out of a total of 449 workers. Prevalence: 16.48%. Of the 74 cases identified, 71 were women (95.9%). The average age was 49.18 years (27-64). Most of the lesions were located on the thighs bilaterally. The LS lesions did not disappear in 66.6% of the cases, while in 33.3% they did. Teleworking and body mass index were not significant factors in the disappearance of the injuries. Conclusions: Semicircular lipoatrophy is an infrequent alteration of the subcutaneous tissue influenced by a series of factors ranging from work environment, individual susceptibility and female sex. LS lesions take a very variable time to reverse, it is usually a slow process whose duration is measured in years rather than months. Neither telework nor body mass index had a statistically significant relationship in the disappearance of injuries in this series. (AU)

Self-Perceived Handicap Associated With Dysphonia and Health-Related Quality of Life of Asthma and Chronic Obstructive Pulmonary Disease Patients: A Case-Control Study.

Purpose The association between voice alterations, health-related quality of life (HRQL), and chronic respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD), has previously been reported. The aim of this study was to test the hypothesis that HRQL and dysphonia-associated handicap of patients diagnosed with asthma or COPD are worse than healthy controls. Method A case-control study in which participants were recruited by a consecutive sampling method from a single institution was conducted. Three groups were created: (a) asthma (51 patients), (b) COPD (52 patients), and (c) 50 healthy controls. Self-reported handicap associated with dysphonia was assessed using the 30-item Voice Handicap Index (VHI-30); meanwhile, HRQL was tested via the European Quality of Life (EQ) Questionnaire and the EQ-visual analog scale. Also, aerodynamic assessment applied to phonation was assessed, and maximum phonation time and s/e index were registered. Results VHI scores were higher for asthma and COPD (7.19 ± 8.31 and 11.80 ± 15.18, respectively) than in the control group (3.72 ± 6.78). The EQ index was lower in asthma and COPD patients than in controls. The EQ-visual analog scale showed lower scores in asthma and COPD than in the controls. Conclusions HRQL was worse in COPD patients than in asthma patients. Even though the patient groups showed worse VHI and HRQL scores than the healthy controls, the scores fell within the normal variation range. No significant variations in the maximum phonation time index between groups were noted.

Change in the magnetic configurations of tubular nanostructures by tuning dipolar interactions.

We have investigated the equilibrium states of ferromagnetic single wall nanotubes by means of atomistic Monte Carlo simulations of a zig-zag lattice of Heisenberg spins on the surface of a cylinder. The main focus of our study is to determine how the competition between short-range exchange (J) and long-range dipolar (D) interactions influences the low temperature magnetic order of the nanotubes as well as the thermal-driven transitions involved. Apart from the uniform and vortex states occurring for dominant J or D, we find that helical states become stable for a range of intermediate values of γ = D/J that depends on the radius and length of the nanotube. Introducing a vorticity order parameter to better characterize helical and vortex states, we find the pseudo-critical temperatures for the transitions between these states and we establish the magnetic phase diagrams of their stability regions as a function of the nanotube aspect ratio. Comparison of the energy of the states obtained by simulation with those of simpler theoretical structures that interpolate continuously between them, reveals a high degree of metastability of the helical structures that might be relevant for their reversal modes.

Exchange Bias Effects in Iron Oxide-Based Nanoparticle Systems.

The exploration of exchange bias (EB) on the nanoscale provides a novel approach to improving the anisotropic properties of magnetic nanoparticles for prospective applications in nanospintronics and nanomedicine. However, the physical origin of EB is not fully understood. Recent advances in chemical synthesis provide a unique opportunity to explore EB in a variety of iron oxide-based nanostructures ranging from core/shell to hollow and hybrid composite nanoparticles. Experimental and atomistic Monte Carlo studies have shed light on the roles of interface and surface spins in these nanosystems. This review paper aims to provide a thorough understanding of the EB and related phenomena in iron oxide-based nanoparticle systems, knowledge of which is essential to tune the anisotropic magnetic properties of exchange-coupled nanoparticle systems for potential applications.

Spin-glass-like freezing of inner and outer surface layers in hollow γ-Fe2O3 nanoparticles.

Disorder among surface spins is a dominant factor in the magnetic response of magnetic nanoparticle systems. In this work, we examine time-dependent magnetization in high-quality, monodisperse hollow maghemite nanoparticles (NPs) with a 14.8 ± 0.5 nm outer diameter and enhanced surface-to-volume ratio. The nanoparticle ensemble exhibits spin-glass-like signatures in dc magnetic aging and memory protocols and ac magnetic susceptibility. The dynamics of the system slow near 50 K, and become frozen on experimental time scales below 20 K. Remanence curves indicate the development of magnetic irreversibility concurrent with the freezing of the spin dynamics. A strong exchange-bias effect and its training behavior point to highly frustrated surface spins that rearrange much more slowly than interior spins. Monte Carlo simulations of a hollow particle corroborate strongly disordered surface layers with complex energy landscapes that underlie both glass-like dynamics and magnetic irreversibility. Calculated hysteresis loops reveal that magnetic behavior is not identical at the inner and outer surfaces, with spins at the outer surface layer of the 15 nm hollow particles exhibiting a higher degree of frustration. Our combined experimental and simulated results shed light on the origin of spin-glass-like phenomena and the important role played by the surface spins in magnetic hollow nanostructures.

Exchange bias effect in Au-Fe3O4 nanocomposites.

We report exchange bias (EB) effect in the Au-Fe3O4 composite nanoparticle system, where one or more Fe3O4 nanoparticles are attached to an Au seed particle forming 'dimer' and 'cluster' morphologies, with the clusters showing much stronger EB in comparison with the dimers. The EB effect develops due to the presence of stress at the Au-Fe3O4 interface which leads to the generation of highly disordered, anisotropic surface spins in the Fe3O4 particle. The EB effect is lost with the removal of the interfacial stress. Our atomistic Monte Carlo studies are in excellent agreement with the experimental results. These results show a new path towards tuning EB in nanostructures, namely controllably creating interfacial stress, and opens up the possibility of tuning the anisotropic properties of biocompatible nanoparticles via a controllable exchange coupling mechanism.

Learning from nature to improve the heat generation of iron-oxide nanoparticles for magnetic hyperthermia applications.

The performance of magnetic nanoparticles is intimately entwined with their structure, mean size and magnetic anisotropy. Besides, ensembles offer a unique way of engineering the magnetic response by modifying the strength of the dipolar interactions between particles. Here we report on an experimental and theoretical analysis of magnetic hyperthermia, a rapidly developing technique in medical research and oncology. Experimentally, we demonstrate that single-domain cubic iron oxide particles resembling bacterial magnetosomes have superior magnetic heating efficiency compared to spherical particles of similar sizes. Monte Carlo simulations at the atomic level corroborate the larger anisotropy of the cubic particles in comparison with the spherical ones, thus evidencing the beneficial role of surface anisotropy in the improved heating power. Moreover we establish a quantitative link between the particle assembling, the interactions and the heating properties. This knowledge opens new perspectives for improved hyperthermia, an alternative to conventional cancer therapies.

Controlling exchange bias in Co-CoOx nanoparticles by oxygen content.

We report on the occurrence of exchange bias on laser-ablated granular thin films composed of Co nanoparticles embedded in an amorphous zirconia matrix. The deposition method allows one to control the degree of oxidation of the Co particles by tuning the oxygen pressure at the vacuum chamber (from 2 x 10(-5) to 10(-1) mbar). The nature of the nanoparticles embedded in the nonmagnetic matrix is monitored from metallic, ferromagnetic (FM) Co to antiferromagnetic (AFM) CoO(x), with a FM/AFM intermediate regime for which the percentage of the AFM phase can be increased at the expense of the FM phase, leading to the occurrence of exchange bias in particles of about 2 nm in size. For an oxygen pressure of about 10(-3) mbar the ratio between the FM and AFM phases is optimum with an exchange bias field of about 900 Oe at 1.8 K. The mutual exchange coupling between the AFM and FM is also at the origin of the induced exchange anisotropy on the FM leading to high irreversible hysteresis loops, and the blocking of the AFM clusters due to proximity to the FM phase.