Effects of diversification among assets in an agent-based market model

We extend to the multi-asset case the framework of a discrete time model of a single asset financial market developed in Ghoulmie et al (2005). In particular, we focus on adaptive agents with threshold behavior allocating their resources among two assets. We explore numerically the effect of this diversification as an additional source of complexity in the financial market and we discuss its destabilizing role. We also point out the relevance of these studies for financial decision making.Comment: 12 pages, 5 figures, accepted for publication in the Proceedings of the Complex Systems II Conference at the Australian National University, 4-7 December 2007, Canberra, ACT Australi

La diplomacia, como factor de comunicación del sistema inter-estatal

Cuentan las crónicas que de la embajada enviada por Carlomagno al califa abasida Harun el Raschid, únicamente regresó en el año 801 un superviviente, el judío Isaac, pues sus compañeros de misión fueron muertos en el viaje. Y eso que se trataba de un contacto entre dos de los monarcas más poderosos de la época. El 2 de diciembre de 1989 en aguas de la isla de Malta y a bordo del buque Máximo Gorki, se reunieron en amigable conferencia Mijail Gorbachov y George Bush. Cientos de periodistas cubrieron la información del suceso y millones de personas pudieron seguir por la televisión, en todo el mundo, el desarrollo de la cumbre soviético-norteamericana. Tan sólo mil ciento ochenta y ocho anos separaban ambos hechos. Comparar los cambios experimentados en este corto período de tiempo por los sistemas de comunicación y por los modos diplomáticos ilustra, como pocos ejemplos pueden hacerlo, la transformación experimentada por las relaciones entre los hombres y entre los pueblos

A great enigma of the Italian Renaissance: paleopathological study on the death of Giovanni dalle Bande Nere (1498-1526) and historical relevance of a leg amputation.

The Medici project consisted in archeological and paleopathological researches on some members of the great dynasty of the Italian Renaissance. The remains of Giovanni de' Medici, so-called "dalle Bande Nere" (Forli 1498- Mantua 1526) has not been investigated yet. The enigma of the fatal injury and leg amputation of the famous Captain excited curiosity of paleopathologists, medical scientists and Italian Society of Orthopedic and Traumatology which contributed to realize the project of exhumation and study of his skeletal remains. The aim of the study is to report the first anthropological and paleopathological results. The tomb of Giovanni and his wife Maria Salviati was explored and the skeletal remains were investigated. Anthropological and paleopathological examination defined: age at death, physical constitution and activity, skeletal diseases. The bony fragments of the leg were studied macroscopically, under stereoscopic microscope, at X-ray and CT scans to detect type of injury and level of amputation. The skeleton and muscular insertions of Giovanni revealed a young-adult and vigorous man, subjected to stresses of military activity since adolescence. Right tibia was amputated below the proximal half of diaphysis leaving long tibio-fibular fragments with a horizontal cut only at the lateral portion. Thus, the surgeon limited to complete the traumatic hemi-amputation. Amputation in the Sixteenth Century technically consisted in guillotine incisions below the knee using crescent shaped knife and bony saw, usually leaving a quite long tibial fragment. Amputations in the Sixteenth Century were contaminated and grossly performed not providing vascular binding nor wound closure. The surgeon performed the procedure in conformity with surgical knowledge of that period

A Multi Agent Model for the Limit Order Book Dynamics

In the present work we introduce a novel multi-agent model with the aim to reproduce the dynamics of a double auction market at microscopic time scale through a faithful simulation of the matching mechanics in the limit order book. The agents follow a noise decision making process where their actions are related to a stochastic variable, "the market sentiment", which we define as a mixture of public and private information. The model, despite making just few basic assumptions over the trading strategies of the agents, is able to reproduce several empirical features of the high-frequency dynamics of the market microstructure not only related to the price movements but also to the deposition of the orders in the book.Comment: 20 pages, 11 figures, in press European Physical Journal B (EPJB

External fixation for displaced intra-articular fractures of the calcaneum

A minimally-invasive procedure using percutaneous reduction and external fixation can be carried out for Sanders' type II, III and IV fractures of the os calcis. We have treated 54 consecutive closed displaced fractures of the calcaneum involving the articular surface in 52 patients with the Orthofix Calcaneal Mini-Fixator. Patients were followed up for a mean of 49 months (27 to 94) and assessed clinically with the Maryland Foot Score and radiologically with radiographs and CT scans, evaluated according to the Score Analysis of Verona. The clinical results at follow-up were excellent or good in 49 cases (90.7%), fair in two (3.7%) and poor in three (5.6%). The mean pre-operative Böhler's angle was 6.98° (5.95° to 19.86°), whereas after surgery the mean value was 21.94° (12.58° to 31.30°) (p < 0.01). Excellent results on CT scanning were demonstrated in 24 cases (44.4%), good in 25 (46.3%), fair in three (5.6%) and poor in two (3.7%). Transient local osteoporosis was observed in ten patients (18.5%), superficial pin track infection in three (5.6%), and three patients (5.6%) showed thalamic displacement following unadvised early weight-bearing. The clinical results appear to be comparable with those obtainable with open reduction and internal fixation, with the advantages of reduced risk using a minimally-invasive technique