Two dimensional electron gas confined over a spherical surface: Magnetic moment

Magnetism of capped nanoparticles, NPs, of non- magnetic substances as Au and ZnO is briefly reviewed. The source of the magnetization is discussed on the light of recent X-ray magnetic circular dichroism experiments. As magnetic dichroism analysis has pointed out impurity atoms bonded to the surface act as donor or acceptor of electrons that occupy the surface states. It is proposed that mesoscopic collective orbital magnetic moments induced at the surface states can account for the experimental magnetism characteristic of these nanoparticles. The total magnetic moment of the surface originated at the unfilled Fermi level can reach values as large as 10(2) or 10(3) Bohr magnetons

Metallic magnetic nanoparticles

In this paper, we reviewed some relevant aspects of the magnetic properties of metallic nanoparticles with small size ( below 4 nm), covering the size effects in nanoparticles of magnetic materials, as well as the appearance of magnetism at the nanoscale in materials that are nonferromagnetic in bulk. These results are distributed along the text that has been organized around three important items: fundamental magnetic properties, different fabrication procedures, and characterization techniques. A general introduction and some experimental results recently obtained in Pd and Au nanoparticles have also been included. Finally, the more promising applications of magnetic nanoparticles in biomedicine are indicated. Special care was taken to complete the literature available on the subject

Does ict resources improve the sport teaching processes in handball?

La motivación (M) y la capacidad de percepción-análisis (PA) del juego, variables del proceso de enseñanza-aprendizaje, fueron evaluadas tras utilizar diferentes recursos durante las explicaciones del entrenador. 71 jugadores(Sub-18) fueron divididos en dos grupos: G1 (n=35): recursos tradicionales; G2 (n=36): recursos multimedia. Se evaluó el nivel inicial (i) y final (f), tras 10 sesiones de entrenamiento. Ambas variables mejoraron significativamente en ambos grupos. Fueron mayores las mejoras del G2 en ambas variables (p<.001). Se hallaron únicamente diferencias intergrupales en la evaluación final en M y PA (p<.001), mostrando el Grupo 2 mejores resultados. Se concluye que la utilización de recursos multimedia posee un efecto positivo mayor que los recursos tradicionales sobre M y PA en jugadores de balonmano (Sub-18).Motivation (M) and game perception-analysis ability (PA), variables in the teaching-learning process, were evaluated after using different resources during the coach’s explanations. Seventy-one players (Under-18) were divided into 2 groups: G1 (n = 35) traditional resources; G2 (n = 36) multimedia resources. Initial (i) and final (f) levels of both variables were evaluated after 10 training sessions. Both variables showed a significant improvement in both groups. The improvements shown in G2 were greater in both variables (p<0.001). Intergroup differences were only found in the final evaluation in M and PA (p<0,001), where G2 obtained better results. It was concluded that using multimedia resources has a greater positive effect than traditional resources on M and PA in under-18 handball players

Interface double-exchange ferromagnetism in the Mn-Zn-O system: New class of biphase magnetism

In this Letter, we experimentally show that the room temperature ferromagnetism in the Mn-Zn-O system recently observed is associated with the coexistence of Mn^(3+) and Mn^(4+) via a double-exchange mechanism. The presence of the ZnO around MnO_2 modifies the kinetics of MnO_2 →Mn_2O_3 reduction and favors the coexistence of both Mn oxidation states. The ferromagnetic phase is associated with the interface formed at the Zn diffusion front into Mn oxide, corroborated by preparing thin film multilayers that exhibit saturation magnetization 2 orders of magnitude higher than bulk samples

Resultados a largo plazo de intervención de Magnuson-Stack modificada para la luxación anterior recidivante de hombro

Los autores han realizado una revisión largo plazo versus corto plazo con 29 pacientes tratados mediante la técnica de Magnuson-Stack por luxación anterior recidivante de hombro. Se encontró un empobrecimiento de los resultados globales, observándose empeoramiento de la estabilidad (pasan del 90.47% de resultados excelentes al 58.62%, así como del 9.52 de resultados malos al 31.03%), aumento del arco de movilidad (movilidad excelente del 57.14 al 82.75%), permaneciendo la función prácticamente inalterada.Twenty-nine patients with recurrent shoulder dislocation trailed surgicaly by modified Magnuson-Stack procedure are colected. The authors made a long-term versus short-term review of results. They have found a worsening of results in the total longterm review. They observe a worsening of the stability (90.47% excellent results in short-term but 58.62% in long-term) (9.52% bad results in short-term but 31.03% in long-term). There are an increase of range mobility (57.14% excellent in short-term versus 82.75% in long-term). The function remain unchanged

Electrochemical synthesis and magnetic properties of MFe_2O_4 (M = Fe, Mn, Co, Ni) nanoparticles for potential biomedical applications

In this study, we evaluate the magnetic properties and cytotoxic effect of magnetic nanoparticles (MNPs) based on magnetite and Mn, Co and Ni ferrites, obtained by electrochemical synthesis. These nanoparticles have almost spherical shape and an mode size of 9 +/- 1 nm. The electrochemical synthesis produces a single crystallographic phase with a spinel-like structure in all cases. Magnetization saturation at room temperature varies with the composition of the ferrites from M_S (Fe_3O_4) > M_S (MnFe_2O_4) > M_S (CoFe_2O_4) > M_S (NiFe_2O_4). Ferrite MNPs present low magnetic remanence indicating a superparamagnetic-like response at room temperature. However, the different values of magnetic anisotropy and size produce variations in the values of coercivity and susceptibility of the ferrite MNPs. The cytotoxicity of the different ferrites was evaluated by internalizing MNP in HeLa cancer cells. Although magnetite and Mn ferrite present low toxicity for all the concentrations studied, significant cytotoxic effect were observed when incubating the cells with high concentration of Co and Ni ferrites

Sacrolistesis postraumática sin lesión neurológica

Las fracturas transversas de sacro son raras pero aún lo son más aquellas en las que hay un desplazamiento o listeis de una vértebra sacra sobre otra. El sentido de desplazamiento viene condicionado por el mecanismo causante, pudiendo ser en flexión o en extensión. En las verdaderas listesis el sentido del traumatismo es en extensión, llevando a colocarse total o parcialmente la vértebra sacra superior por delante de la inferior. En determinados casos como pueden ser los politraumatizados, el diagnóstico puede ser difícil, por lo que es necesario realizar un estudio radiológico meticuloso. En estas fracturas ocurre frecuentemente una lesión de raíces lumbosacras de mayor o menor gravedad, aunque suele existir algún tipo de recuperación, incluso espontánea, con el transcurso del tiempo. Se presenta el caso de una mujer que presentó una sacrolistesis de S1 sobre S2 por haber sufrido caída de nalgas, sin existir ninguna lesión neurológica.Transverse fractures of the sacrum are rare, but fractures with displacement or listhesis of one sacral vertebra over another are even more infrequent. The direction of the displacement is conditioned by the causing mechanism and may occur in flexion or extension, in true listhesis, trauma occurs in extension, placing the superior sacral vertebra totally or partially in from of the inferior vertebra. In some cases, such as multiple traumas, the diagnosis can be difficult, and a careful radiologic study is required. A more or less severe injury of th lumbosacral roots frequently occurs in these fractures, although a certain degree of recovery takes place, even spontaneously, over time. We present the case of a 69 years old woman suffering from a sacrolisthesis of S1 over S2 after a fall on the buttocks with no neurological lesion

Effects of moderate static magnetic field on neural systems is a non-invasive mechanical stimulation of the brain possible theoretically?

Static magnetic fields have been shown to induce effects on the human brain. Different experiments seem to support the idea that moderate static magnetic field can exert some influence on the gating processes of the membrane channels. In this article we visit the order of magnitude of the energy magnetic terms associated with moderate applied field (between 10 and 200 milliteslas). It is shown that gradients of the Zeeman energy associated with the inhomogeneous applied fields can induce pressures of the order of 10^(-2)Pa. The surface tension generated by the magnetic pressure, on the surface delimiting the brain region subject to relevant field and gradients, is found to range between 10^(-1) and 1 mN.m^(-1). These pressures seem to be strong enough to interfere with the elastic and electrostatic energies involved in the channel activation-inactivation-deactivation mechanisms of biological membranes. It has been described that small mechanical force can activate voltage gated potassium channels. Moreover, stretch-activated ion channels are widely described in different biological tissues. Virtually, all these channels can modify their activity if stressed by a sufficient pressure delivered for enough time. We propose mechanical stimulation - possibly not exclusively - as a candidate mechanism how static magnetic field can produce effects in biological systems. It must be emphasized, that such field gradients were not previously proposed as a possible source of neural activity modification

Lipomatosis epidural lumbosacra idiopática: revisión de la bibliografía y caso clínico

La lipomatosis epidural es una afección que aparece generalmente en relación con hipercortisolismos endógenos o exógenos, siendo más raras las formas idiopáticas, de las que se han descrito únicamente 17 casos. Se presenta un nuevo caso con sintomatología compatible con estenosis de canal, y que tras estudios de imagen se demostró que correspondía con una lipomatosis epidural lumbosacra. Se le encomendó al paciente una reducción de peso, con lo que se alivió parcialmente la sintomatología, permaneciendo estable en la actualidad. Se revisa la bibliografía de este raro proceso, exponiendo los distintos hallazgos encontrados. Algunos autores proponen una reducción de peso, lo cual puede aliviar la sintomatología. Para casos rebeldes está indicada la laminectomía asociada al despegamiento de la grasa sin realizar exploración intradural.Epidural lipomatosis is an affection that is usually related to endogenic or exogenous hipercortisolism. Less frequently, it can be idiopathic. To date only 17 cases have been documented. A new case is presented in a patient suffering from symptoms resembling lumbar spinal stenosis. The radiological studies revealed a compression of the dural sac at lumbosacral levéis, caused by tissue similar in density to fat. Weight reduction, was recommended to the patients and a partial relief of symptoms was achieved. The authors reviewed the pathogeny of epidural lipomatosis and its various different treatments. In the idiopathic form, weight reduction is recomended first, reserving surgery for those cases that do not respond to this initial treatment. Surgical treatment should consist of laminectomy and fat debulking, and should not include intradural exploration

Thermal treatment effect on the mechanical, tribological and corrosion properties of Ni-W alloy obtained by direct and pulse plating electrodeposition

Ni-W electrodeposits have emerged as one of the most suitable alternatives to hard chromium mainly owing to their remarkable mechanical and tribological properties. Additionally, advanced technologies that require materials resistant to high temperatures could benefit from the use of Ni-W coatings. In this work, the effect of thermal treatment at different temperatures (300, 500, 700°C) on the characteristics of Ni-W coatings obtained by direct and pulse plating (PP) was studied. The morphology, composition, crystalline structure, hardness, wear rate, friction coefficient and corrosion resistance of the thermally treated coatings were analysed and compared with the performance of hard chromium coatings. The results indicate that the pulse-plated Ni-W coatings show better mechanical and tribological properties than the ones obtained by direct current. A significant improvement in hardness in Ni-W layers was achieved by thermal treatment, mainly in the films grown by PP, with minor changes in wear resistance and corrosion performance