A cluster model with random anisotropy for hysteresis jumps in CeNi1−x_{1-x}Cux_{x} alloys

Some Cerium compounds exhibit hysteresis cycles with sharp macroscopic jumps in the magnetization at very low temperatures. This effect is attributed to the formation of clusters in which the anisotropy competes with the applied magnetic field. Here, we present a simple model where a lattice of ferromagnetically coupled spins is separated in clusters of random sizes and with random anisotropy. Within this model, we obtain hysteresis cycles presenting jumps that behave in a similar way that the experimental ones, and that disappear when increasing the temperature. The results are in good agreement with the hysteresis cycles measured at very low temperatures in CeNi$_{1-x}$Cu$_{x}$ and the comparison with these experimental results allows to discriminate the relative importance of the mechanisms driving the thermal evolution of the cycles.Comment: Accepted in PR

Convolutional Goppa Codes

We define Convolutional Goppa Codes over algebraic curves and construct their corresponding dual codes. Examples over the projective line and over elliptic curves are described, obtaining in particular some Maximum-Distance Separable (MDS) convolutional codes.Comment: 8 pages, submitted to IEEE Trans. Inform. Theor

El bibliòfil Bernat d'Esplugues (+1433), notari i escrivà del Consell de la ciutat

La historiografia sobre la ciutat de Barcelona no ha prestat, en general, gaire atenció a l'escrivania municipal dels segles XIV i XV, ni tampoc als professionals que hi treballaven, a excepció de l'atenció mostrada per alguns fedataris que ocuparen càrrecs polítics de certa rellevància en moments d'especial significació històrica; pensem, per exemple, en el notari Antoni Vinyes, conseller i ambaixador del municipi

Contenido polínico de la atmósfera de la ciudad de Orense, primeros resultados (marzo 1986-marzo 1987)

El presente trab•jo rcooge los primeroo resultadO< del contenido poltnico de la atmWcra de la ciudad de Orcnse, regisrradoo durante el periodo de un año (!5 de Ma11.o de 1.986-14 de :>tara> de 1987) dentro de un programa P<e-;sto a largo plazo y por el que se pretcadc conocer las fluctuaciones anuales e intcrenualcs en dicha ciudad Un 101al de 35 pcrr.Jcs rcllejan ol contenido pollnico por periodos de dos a tres dios a lo largo del año. Pinu.s es d géocro más abundante de los rtprescnlados con m~ximos en t i mes de mayo, le siguen Ptouuuzs (abril) y Quercm (mayo); entre las familias las Gramintae y PDpilionoctat son las más abu ndante.~In this J'"pcr WC have collea ed pollcn·count rcadings fur tbe city or Orense, rcgistered over • period or onc ycar (15th march l986- 14th march 1987). This ;, part of a long-tcnn programm: of im·cstigation through whic.:h we y,rjs)¡ 10 discover the annual and in· terannllal fi uct.uu tion of the pollcn-count in thi.s city. Thi rt yfivc graphs reflect the pol!cn· couot for periods OÍ IWO lO threc days tal:en throoghoul the year. Of the specics rcprcscntcd here Pimu is the most :Jbundant, with maximum oounts in may, folloy.ocd by Plarwn;s (in april). and Quw:UJ (may). The moSI abundan! amoog thc familic! are thc Gronuncoe ond the PapUionautu