Effects of boundary conditions on magnetization switching in kinetic Ising models of nanoscale ferromagnets

Magnetization switching in highly anisotropic single-domain ferromagnets has been previously shown to be qualitatively described by the droplet theory of metastable decay and simulations of two-dimensional kinetic Ising systems with periodic boundary conditions. In this article we consider the effects of boundary conditions on the switching phenomena. A rich range of behaviors is predicted by droplet theory: the specific mechanism by which switching occurs depends on the structure of the boundary, the particle size, the temperature, and the strength of the applied field. The theory predicts the existence of a peak in the switching field as a function of system size in both systems with periodic boundary conditions and in systems with boundaries. The size of the peak is strongly dependent on the boundary effects. It is generally reduced by open boundary conditions, and in some cases it disappears if the boundaries are too favorable towards nucleation. However, we also demonstrate conditions under which the peak remains discernible. This peak arises as a purely dynamic effect and is not related to the possible existence of multiple domains. We illustrate the predictions of droplet theory by Monte Carlo simulations of two-dimensional Ising systems with various system shapes and boundary conditions.Comment: RevTex, 48 pages, 13 figure

First-principles study of TMNan (TM= Cr, Mn, Fe, Co, Ni; n = 4-7) clusters

Geometry, electronic structure, and magnetic properties of TMNan (TM=Cr-Ni; n = 4-7) clusters are studied within a gradient corrected density functional theory (DFT) framework. Two complementary approaches, the first adapted to all-electron calculations on free clusters, and the second been on plane wave projector augmented wave (PAW) method within a supercell approach are used. Except for NiNan, the clusters in this series are found to retain the atomic moments of the TM atoms, and the magnetic moment presented an odd-even oscillation with respect to the number of Na atoms. The origin of these odd-even oscillations is explained from the nature of chemical bonding in these clusters. Differences and similarities between the chemical bonding and the magnetic properties of these clusters and the TMNan (TM = Sc, V and Ti; n = 4-6) clusters on one hand, and TM-doped Au and Ag clusters on the other hand, are discussed

Calcul des multiplets de spin de l'ion Cr

La luminescence de Cr3+ a été étudiée de manière extensive et la dépendance du spectre d’absorption avec la distance Cr-0 a été mise en évidence1,2’3. Dans le présent travail on a calculé les intégrales électrostatiques (a, b, c, d, e, f, g, h, i, j)7, nécessaires à la détermination des multiplets de spin. Mais du fait de la délocalisation de l’orbitale eg dans la région de l’outersphère, nous nous sommes ramenés au modèle proposé par Tanabe et Sugano1. L’influence de la distance Cr-0 (0.19 à 0.22 nm) sur la structure électronique a été étudiée, et à partir des diagrammes de termes, on a discuté les résultats expérimentaux relatifs aux grenats dopés au chrome

Behavioural lateralization in domestic pigs (Sus scrofa)—variations between motor functions and individuals

Motor lateralization is hypothesized to depend on the complexity of the motor function, but it might at the same time reflect hemispheric dominance within an individual across motor functions. We investigated possible motor lateralization patterns in four motor functions of different complexity (snout use in a manipulative task, foot use in two-stepping tasks and tail curling) in the domestic pig, a tetrapod species relevant as farm animal but also as a model in human neuroscience. A significant majority of our sample showed individual biases for manipulation with their snout and for curling their tail. Interestingly, the tail curling was lateralized towards the right at the population level and showed stronger lateralization patterns than the snout. Using a cluster analysis with combined tail and snout laterality, we identified groups of individuals with different lateralization patterns across motor functions that potentially reflect the individuals’ hemispheric dominance. To conclude, our results suggest that pigs show lateralization patterns that depend on the motor function and on the individual. Such individual lateralization patterns might have broader implications for animal personality and welfare. Our study lays the methodological groundwork for future research on laterality in pigs

Assessing animal individuality: links between personality and laterality in pigs

Animal individuality is challenging to explain because individual differences are regulated by multiple selective forces that lead to unique combinations of characteristics. For instance, the study of personality, a core aspect of individuality, may benefit from integrating other factors underlying individual differences, such as lateralised cerebral processing. Indeed, the approach-withdrawal hypothesis (the left hemisphere controls approach behaviour, the right hemisphere controls withdrawal behaviour), may account for differences in boldness or exploration between left and right hemispheric dominant individuals. To analyse the relationships between personality and laterality we tested 80 male piglets with established laterality patterns for two motor functions (tail curling direction and the side of the snout used for manipulation) and a combined classification integrating both motor functions using cluster analysis. We analysed basal salivary testosterone and cortisol along with their behaviour in standardized tests as pre-established indicators of different personality traits (Boldness, Exploration, Activity, Sociability and Coping). We found that the direction of the single motor biases showed significant associations with few personality traits. However, the combined laterality classification showed more, and more robust, significant associations with different personality traits compared to the single motor biases. These results supported the approach-withdrawal hypothesis because right-biased pigs were bolder and more explorative in a context of novelty. Additionally, right-biased pigs were more sociable than left-biased pigs. Therefore, the present study indicates that personality is indeed related to lateralised cerebral processing and provides insight into the multifactorial nature of individuality

Klebsiella pneumoniae necrotizing fasciitis of the leg in an elderly French woman

Marguerite Monié,1 Laurence Drieux,2–4 Bernadette Nzili,1 Michèle Dicko,5 Catherine Goursot,1 Sandrine Greffard,6 Dominique Decré,3,4,7 Anthony Mézière1 1Assistance Publique-Hôpitaux de Paris (AP-HP), GHU Pitié Salpêtrière-Charles Foix, site Charles Foix, Service de Soins de Suite et Réadaptation orthogériatrique et polyvalent, Fondation d’Heur et Chemin Delatour, Ivry s/Seine, 2Assistance Publique-Hôpitaux de Paris, Hôpital Charles-Foix, Bactériologie-Hygiène, Paris, 3Sorbonne Universités, UPMC Univ Paris 06, CR7, Centre d’Immunologie et des Maladies Infectieuses, CIMI, team E13 (Bacteriology), Paris, 4INSERM, U1135, Centre d’Immunologie et des Maladies Infectieuses, CIMI, team E13 (Bacteriology), Paris, 5AP-HP, GHU Henri Mondor, Département de Médecine Interne et Gériatrie, Créteil, 6AP-HP, GHU Pitié Salpêtrière-Charles Foix, site Pitié Salpêtrière, Service de Médecine Gériatrique, Paris, 7AP-HP, Hôpital Saint-Antoine, Bactériologie-Hygiène, Paris, France Abstract: Klebsiella pneumoniae necrotizing fasciitis is a rare infection in regions outside of Asia. Here, we present a case of necrotizing fasciitis of the leg caused by K. pneumoniae in a 92-year-old French woman hospitalized in a geriatric rehabilitation unit. The patient initially presented with dermohypodermitis of the leg that developed from a dirty wound following a fall. A few hours later, this painful injury extended to the entire lower limb, with purplish discoloration of the skin, bullae, and necrosis. Septic shock rapidly appeared and the patient died 9 hours after the onset of symptoms. The patient was Caucasian, with no history of travel to Asia or any underlying disease. Computed tomography revealed no infectious metastatic loci. Blood cultures showed growth of capsular serotype K2 K. pneumoniae strains with virulence factors RmpA, yersiniabactin and aerobactin. This rare and fatal case of necrotizing fasciitis caused by a virulent strain of K. pneumoniae occurred in a hospitalized elderly woman without risk factors. Clinicians and geriatricians in particular should be aware of this important albeit unusual differential diagnosis. Keywords: necrotizing fasciitis, Klebsiella pneumoniae, elderl