Chirality-that is, left or right handedness-is present in many scientific areas, and particularly in condensed matter physics. Inversion symmetry breaking relates chirality with skyrmions, which are protected field configurations with particle-like and topological properties. Here we show that a kagome magnet, with Heisenberg and DzyaloshinskiiMoriya interactions, causes non-trivial topological and chiral magnetic properties. We also find that under special circumstances, skyrmions emerge as excitations, having stability even at room temperature. Chiral magnonic edge states of a kagome magnet offer, in addition, a promising way to create, control and manipulate skyrmions. This has potential for applications in spintronics, that is, for information storage or as logic devices. Collisions between these particle-like excitations are found to be elastic at very low temperature in the skyrmionskyrmion channel, albeit without mass-conservation. Skyrmion-antiskyrmion collisions are found to be more complex, where annihilation and creation of these objects have a distinct non-local nature.

The ground-state electronic, structural, and magnetic properties of small silver clusters, Agn (2≤n≤22), have been studied using a linear combination of atomic Gaussian-type orbitals within the density functional theory. The results show that the silver atoms, which are diamagnetic in bulk environment, can be magnetic when they are grouped together in clusters. The Ag13 cluster with icosahedral symmetry has the highest magnetic moment per atom among the studied silver clusters. The cluster symmetry and the reduced coordination number specific of small clusters reveal as a fundamental factor for the onset of the magnetism.PACS numbers: 36.40. Cg,36.40.Qv,31.15.Ar In the last two decades, the research field of clusters has shown a rapid development in both experimental and theoretical investigations [1], since the clusters are well suited for several applications. For example, there has been a traditional interest in applications to catalysis [2], due to the considerable surface/volume ratio of clusters. More recently, clusters or nanoparticles that possess magnetic properties have offered exciting new opportunities for biomedical applications including (i) magnetic separation of labeled cells; (ii) therapeutic drug delivery; (iii) hyperthermic treatment for malignant cells; (iv) contrast enhancement agents for magnetic resonance imaging applications; (v) and also very recently for manipulating cell membranes [3].Clusters are on the border line between atoms and bulk and thereby, they play an important role in understanding the transition from the microscopic structure to the macroscopic structure of matter. Although 4d and 5d transition metal atoms have unfilled localized d states, none of them are magnetic. Only a few of the 3d transition metals form magnetic solids. Thus, from the magnetic point of view, one of the long standing problems in condensed matter physics is to understand why some nonmagnetic metals become magnetic when they condense into clusters. There are two factors characteristic of clusters that mainly contribute to the onset and enhancement of the magnetism, namely, the reduced coordination number and the high symmetry since that, symmetry enables degeneracy and degeneracy spawns magnetism [4]. According to this, an icosahedral structure is a good candidate for the appearance of the magnetism because the maximal degeneracy of an irreducible representation of the icosahedra (I h ) group is 5 whereas all other cluster symmetries allow at most three-fold degeneracy, as was reported by Reddy et al. for Pd, Rh, and Ru [5].In this letter, we present first-principles calculations on small silver clusters exhibiting an important magnetism, * Email address: fampl@usc.es which has not been predicted until now. In the present work, we study the evolution of the magnetism of silver clusters as a function of the cluster size and special emphasis is placed on the effects of cluster symmetry. The magnetic behavior that we got is very interesting, if not astonishing, compared with the silver bulk magnetic p...

There are few reports studying the aetiology of onychomycosis in children in Spain. To study childhood dermatophyte onychomycosis, a retrospective study of children was carried out, who were <16 years of age with dermatophyte onychomycosis diagnosed between 1987 and 2007. Of 4622 nail samples from 3550 patients, 218 came from 181 children up to 16 years old. Onychomycosis caused by dermatophytes was demonstrated in 28 (15.5%) cases. Trichophyton rubrum (18 cases) was the most prevalent species, followed by Trichophyton tonsurans (five cases), Trichophyton mentagrophytes var. interdigitale (four cases) and Trichophyton mentagrophytes var. mentagrophytes (one case). Concomitant dermatophytosis at other locations was confirmed in seven cases (25%). Toenail onychomycosis was associated with tinea pedis in five cases. Distal and lateral subungual onychomycosis was the most common clinical pattern. The superficial white type was found in two cases of toenail onychomycosis caused by T. rubrum and T. tonsurans. During the period of study, only 5.1% of all investigated people were children up to 16 years. The prevalence of onychomycosis tended to increase over the years and represented 15.5% of all nail dystrophies in children. Therefore, dermatologists must consider onychomycosis in the differential diagnosis of nail alterations in children and always perform a mycological study to confirm the diagnosis.

The static response properties and the structural stability of silver clusters in the size range 1 ≤ n ≤ 23 have been studied using a linear combination of atomic Gaussian-type orbitals within the density functional theory in the finite field approach. The Kohn-Sham equations have been solved in conjuction with a generalized gradient approximation (GGA) exchange-correlation functional. A proof that the finite basis set GGA calculation holds the Hellmann-Feynman theorem is also included in the Appendix. The calculated polarizabilities of silver clusters are compared with the experimental measurements and the jellium model in the spillout approximation. Despite the fact that the calculated polarizabilities are in good agreement with both of them, we have found that the polarizability appears to be strongly correlated to the cluster shape and the highest occupied-lowest unoccupied molecular-orbital gap.

From October 1994 to November 1995, a prospective study aiming to detect dermatophytes on the scalp was undertaken in 5000 unselected school children aged between 3 and 16 years (mean age 8.34 years, SD +/- 3.83). Thirty-two (0.64%) had dermatophytes in the scalp, 22. (0.44%) had tinea capitis and 10 were asymptomatic scalp carriers. It is important to point out that 33% of the patients with tinea capitis and 60% of the asymptomatic scalp carriers also had ringworm in other body sites. There was a significantly higher proportion of cases of tinea capitis (P < 0.001)(particularly due to Trichophyton tonsurans, P < 0.001) and of cases of asymptomatic scalp carriers (P < 0.05) (particularly due to Trichophyton tonsurans, P < 0.001) in the immigrant population of African origin. In all the child index cases with positive scalp cultures (tinea capitis and carriers), the household members were studied clinically and mycologically. One child had a body ringworm caused by Microsporum canis. Twelve adults had positive cultures with dermatophytosis (one tinea capitis and eleven body ringworm). Three adult patients were also carriers of dermatophytes in other body sites. Our data indicate a change in the causative agents of tinea capitis seen in Madrid over a 12-month period, with cases due to antropophilic species (T. tonsurans, T. soudanense, M. audouinii and T. violaceum) occurring in the immigrant population from Africa; as a consequence, there is an emergence of T. tonsurans in the Spanish population.