DON AGUSTÍN NIETO CABALLERO ANDANTE DE LA EDUCACIÓN

Entre los pocos maestros inolvidables del autor figura don Agustin Nieto Caballero, un ilustre educador bogotano que, a partir de las teorias psicologicas, pedagogicas y filosoficas de Jhon Dewey, Ovide Decroly, Maria Montesori y Henri Bergson, instituyo en Colombia la Escuela Nueva, y fundo con otros colombianos no menos notables, en 1914, el Gimnasio Moderno que tanta influencia ha tenido en el desarrollo edeucativo del pais y de America Latina. El presente articulom, a la vez que destaca el aporte de Nieto Caballero a la luz de las ideas fundamentales de sus mentores, rinde homenaje al Maestro que hizo posible una audaz renovacion de la educacion colombiana

Optical Properties of Heavy Fermion Systems with SDW Order

The dynamical conductivity $\sigma (\omega)$, reflectivity $R(\omega)$, and tunneling density of states $N(\omega)$ of strongly correlated systems (like heavy fermions) with a spin-density wave (SDW) magnetic order are studied as a function of impurity scattering rate and temperature. The theory is generalized to include strong coupling effects in the SDW order. The results are discussed in the light of optical experiments on heavy-fermion SDW materials. With some modifications the proposed theory is applicable also to heavy fermions with localized antiferromagnetic (LAF) order.Comment: 9 pages, 10 figure

4f-local magnetic moments in the metals and alloys with SDW-instability

The usual interaction between localized magnetic moments and itinerant electrons (RKKY-coupling) is modified by the additional coupling between nesting electrons and hole parts of the Fermi surface. It is shown that the presence of localized magnetic moments of magnetic impurities leads to the appearance of spin-density-waves in the itinerant electron system even in the case where nesting is bad and the constant of triplet electron-electron interaction is small. In order to calculate the magnetic phase diagram we also introduce the effect of the scattering of the itinerant electrons on the localized spin fluctuations. In addition the influence of external magnetic field on the Néel temperature and magnetic structure is discussed and new experiments are proposed.L'hamiltonien considéré dans cet article décrit les interactions entre les moments magnétiques localisés et les électrons de conduction (terme RKKY), ainsi que le couplage entre les électrons et les trous de la surface de Fermi possédant un terme de « nesting ». La présence d'impuretés ayant un moment magnétique localisé conduit à l'apparition d'ondes de densité de spin pour les électrons de conduction. Ceci reste vrai même dans le cas où le terme de « nesting » et la constante de couplage triplet entre électrons et trous sont très petits. Le calcul du diagramme des phases magnétiques a été fait en tenant compte de la diffusion des électrons par les fluctuations des spins localisés. L'influence du champ magnétique extérieur sur la température de Néel et la structure magnétique a été étudiée. Nous espérons que des expériences de diffraction de neutrons sous champ magnétique pourront confirmer notre proposition

Advanced nuclear fuel cycle for the RF using actinides breeding in thorium blankets of fusion neutron source

The possible role of existing thorium reserves in the Russian Federation on engaging thorium in being currently closed (U-Pu)—fuel cycle of nuclear power of the country is considered. The application efficiency of thermonuclear neutron sources with thorium blanket for the economical use of existing thorium reserves is demonstrated. The aim of the work is to find solutions of such major tasks as the reduction of both front-end and back-end of nuclear fuel cycle and an enhancing its protection against the uncontrolled proliferation of fissile materials by means of the smallest changes in the fuel cycle. During implementation of the work we analyzed the results obtained earlier by the authors, brought new information on the number of thorium available in the Russian Federation and made further assessments. On the basis of proposal on the inclusion of hybrid reactors with Th-blanket into the future nuclear power for the production of light uranium fraction 232 + 233+234U, and 231Pa, we obtained the following results: 1 The fuel cycle will shift from fissile 235U to 233U which is more attractive for thermal power reactors. 2 The light uranium fraction is the most "protected" in the uranium component of fuel and mixed with regenerated uranium will in addition become a low enriched uranium fuel, that will weaken the problem of uncontrolled proliferation of fissile materials. 3 231Pa doping into the fuel stabilizes its multiplying properties that will allow us to implement long-term fuel residence time and eventually to increase the export potential of all nuclear power technologies. 4 The thorium reserves being near city Krasnoufimsk are large enough for operation of large-scale nuclear power of the Russian Federation of 70 GW (e.) capacity during more than a quarter century. The general conclusion: the inclusion of a small number of hybrid reactors with Th-blanket into the future nuclear power will allow us substantially to solve its problems, as well as to increase its export potential