Multiparticie aggregation model for dendritic growth applied to experiments on amorphous Co-P alloys

We introduce a multiparticle biased diffusion limited aggregation model for dendritic growth. Its most relevant feature is that it includes the overall effect of strong applied electric fields and therefore applies to nonequilibrium situations. We compare simulations of a two species version of our model to actual experiments on preparation of amorphous Co-P alloys with very good agreement: The model accurately reproduces the dependence of composition, morphology, and growth time of the alloy on the current. We conclude with a discussion of specific predictions and possible generalizations of the model.Supported by DGICyT (Spain) through Grant No. PB92-0248 and by MEC/Fulbright. MJ.B. and J.M.R. acknowledge support from DGICyT (Spain) Grant No. MAT91-0031. Work at Los Alamos is performed under the auspices of the V.S. D.O.E.Publicad

Leibnizian, Galilean and Newtonian structures of spacetime

The following three geometrical structures on a manifold are studied in detail: (1) Leibnizian: a non-vanishing 1-form $\Omega$ plus a Riemannian metric \h on its annhilator vector bundle. In particular, the possible dimensions of the automorphism group of a Leibnizian G-structure are characterized. (2) Galilean: Leibnizian structure endowed with an affine connection $\nabla$ (gauge field) which parallelizes $\Omega$ and \h. Fixed any vector field of observers Z ($\Omega (Z) = 1$), an explicit Koszul--type formula which reconstruct bijectively all the possible $\nabla$'s from the gravitational ${\cal G} = \nabla_Z Z$ and vorticity $\omega = rot Z/2$ fields (plus eventually the torsion) is provided. (3) Newtonian: Galilean structure with \h flat and a field of observers Z which is inertial (its flow preserves the Leibnizian structure and $\omega = 0$). Classical concepts in Newtonian theory are revisited and discussed.Comment: Minor errata corrected, to appear in J. Math. Phys.; 22 pages including a table, Late

Weak distinction and the optimal definition of causal continuity

Causal continuity is usually defined by imposing the conditions (i) distinction and (ii) reflectivity. It is proved here that a new causality property which stays between weak distinction and causality, called feeble distinction, can actually replace distinction in the definition of causal continuity. An intermediate proof shows that feeble distinction and future (past) reflectivity implies past (resp. future) distinction. Some new characterizations of weak distinction and reflectivity are given.Comment: 9 pages, 2 figures. v2: improved and expanded version. v3: a few misprints have been corrected and a reference has been update

Modulation in the expression of SHP-1, SHP-2 and PTP1B due to the inhibition of MAPKs, cAMP and neutrophils early on in the development of cerulein-induced acute pancreatitis in rats

AbstractThe protein tyrosine phosphatases (PTPs) SHP-1, SHP-2 and PTP1B are overexpressed early on during the development of cerulein -induced acute pancreatitis (AP) in rats, and their levels can be modulated by some species of mitogen-activated protein kinases (MAPKs), the intracellular levels of cAMP and by general leukocyte infiltration, the latter at least for SHP-2 and PTP1B. In this study we show that cerulein treatment activates extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) but not p38 MAPK during the early phase of cerulein-induced AP (2h after the first injection of cerulein). Therefore, by using the MAPK inhibitors SP600125 (a specific JNK inhibitor) and PD98059 (a specific ERK inhibitor), we have unmasked the particular MAPK that underlies the modulation of the expression levels of these PTPs. JNK would act by preventing SHP-1 protein expression from increasing beyond a certain level. ERK 1/2 was the main MAPK involved in the increase in SHP-2 protein expression due to cerulein. JNK negatively modulated the SH2-domain containing PTPs. Both MAPKs played a role in the increase in PTP1B protein expression due to cerulein. Finally, by using the white blood cell inhibitors vinblastine sulfate, gadolinium chloride and FK506 (tacrolimus), we show that the macrophage activity or T-lymphocytes does not modulate the expression of any of the PTPs, although neutrophil infiltration was found to be a regulator of SHP-2 and PTP1B protein expression due to cerulein

On special partitions of [0, 1] and lineability within families bounded variation functions

We show that there exists large algebraic structures (vector spaces, algebras, closed subspaces, etc.) formed entirely (except for 0), on one hand, by singular, nowhere monotonic functions on [0, 1] and, on the other hand, by absolutely continuous nowhere monotonic functions. Several tools, of independent interest, related to obtaining special partitions of R into uncountable collections will be provided and used. The results obtained in this note are either new or improved version of already existing ones.Depto. de Análisis Matemático y Matemática AplicadaFac. de Ciencias MatemáticasFALSEMinisterio de Ciencia e Innovación (MICINN)Junta de AndalucíaWISS 2025 projectunpu

Utilidad de la dermatoscopia en el diagnóstico de la escabiosis

Presentamos el caso de una paciente de 17 años de edad, previamente sana, que consultó por un cuadro de tres semanas de evolución consistente en prurito intenso de predominio nocturno y lesiones cutáneas, sin otra sintomatología sistémica acompañante. En tratamiento con bilastina 20 mg, no había presentado mejoría. La paciente negaba la existencia de convivientes cercanos afectos por los mismos síntomas. A la exploración física presentaba lesiones en forma de pápulas eritematosas milimétricas, alguna de ellas excoriada, a nivel de huecos interdigitales y zona periumbilical. Además, se apreciaba alguna lesión con morfología lineal, ligeramente descamativa, así como vesículas de contenido claro asociadas a las anteriores (fig. 1a). El examen con dermatoscopia de luz polarizada mostró los siguientes hallazgos (fig. 1b): sobre un fondo de eritema, la presencia de estructuras circulares blanco-amarillentas correspondientes a vesículas acarinas, así como una estructura lineal descamativa de morfología ondulada, en cuyo extremo se podía identificar un triángulo marrón..

Actividad ovina y diversificación de los modos de vida rurales en la alta montaña mexicana

UnpublishedTomo I . Sección: Sistemas Ganaderos-Economía y Gestión. Sesión: Sostenibilidad. Ponencia nº 3

A Note on Non-compact Cauchy surface

It is shown that if a space-time has non-compact Cauchy surface, then its topological, differentiable, and causal structure are completely determined by a class of compact subsets of its Cauchy surface. Since causal structure determines its topological, differentiable, and conformal structure of space-time, this gives a natural way to encode the corresponding structures into its Cauchy surface

A note on the existence of standard splittings for conformally stationary spacetimes

Let $(M,g)$ be a spacetime which admits a complete timelike conformal Killing vector field $K$. We prove that $(M,g)$ splits globally as a standard conformastationary spacetime with respect to $K$ if and only if $(M,g)$ is distinguishing (and, thus causally continuous). Causal but non-distinguishing spacetimes with complete stationary vector fields are also exhibited. For the proof, the recently solved "folk problems" on smoothability of time functions (moreover, the existence of a {\em temporal} function) are used.Comment: Metadata updated, 6 page

Líneas cutáneas prominentes: un nuevo criterio de sospecha en lesiones melanocíticas

Presentación del caso Una mujer de 64 años de edad, con daño actínico severo,consultó por una lesión pigmentada de reciente aparición enla cara externa de la pierna izquierda. La exploración clínica reveló que se trataba de una mácula pigmentada irregularde 7mm de diámetro mayor, de aspecto lentiginoso, en uncontexto de intenso fotodaño con la presencia de múltipleslentigos solares en el área cutánea circundante (fig. 1). Comentario Con la dermatoscopia de luz polarizada se apreciaba un discreto retículo pigmentado irregular, áreas de color marrón claro sin estructura, áreas hipopigmentadas y escasos puntos de distribución irregular. Llamaba la atención la presencia de unas líneas o surcos cutáneos prominentes, más claros que el resto de la lesión y que se entrecruzaban entre ellos,interrumpiendo las demás estructuras. Además, se podían observar vasos puntiformes en las zonas hipopigmentadas, más evidentes que en la piel circundante (fig. 2). Teniendo en cuenta el contexto clínico (se trataba de una lesión pigmentada plana de reciente aparición en una paciente con intenso daño solar) y los hallazgos dermatoscópicos, se extirpó la lesión. El estudio anatomopatológico fue de un melanoma maligno in situ, con un patrón de crecimiento lentiginoso. ..