V_{us} from hyperon semileptonic decays

A model-independent determination of the CKM matrix element V_{us} from five measured strangeness-changing hyperon semileptonic decays is performed. Flavor SU(3) symmetry breaking effects in the leading vector and axial-vector form factors are analyzed in the framework of the 1/N_c expansion of QCD. A fit to experimental data allows one to extract the value V_{us}=0.2199\pm 0.0026, which is comparable to the one from K_{e3} decays. This reconciliation is achieved through second-order symmetry breaking effects of a few percent in the form factors f_1, which increase their magnitudes over their SU(3) predictions.Comment: 23 pages, Revtex4, 12 tables, no figure

An open toss problem

We discuss some particular cases of the following problem. Each of m persons tosses a coin. Those who get heads stay for the next round. Those who get tails are eliminated; however, if all persons get tails in a round, they move to the next round (as if each of them had got a head). The problem is to find the possibility that exactly one person is left after r rounds. All coins are considered identical but not necessarily fair

Radiative corrections to all charge assignments of heavy quark baryon semileptonic decays

In semileptonic decays of spin-1/2 baryons containing heavy quarks up to six charge assignments for the baryons and lepton are possible. We show that the radiative corrections to four of these possibilities can be directly obtained from the final results of the two possibilities previously studied. There is no need to recalculate integrals over virtual or real photon momentum or any traces.Comment: 15 pages, 2 figures, RevTex. Extended discussion. Final version to appear in Physical Review

One-loop vertex integrals in heavy-particle effective theories

We give a complete analytical computation of three-point one-loop integrals with one heavy propagator, up to the third tensor rank, for arbitrary values of external momenta and masses.Comment: 10 pages, Latex, to appear in J. Phys.

La función preventiva de los daños punitivos en las relaciones de consumo

En la presente ponencia se busca exponer que los daños punitivos regulados en el artículo 52 bis de la Ley de Defensa del Consumidor 24240 cumplen una función preventiva. En virtud de ello, cabe entender que la función preventiva reconocida en el Código Civil y Comercial de la Nación cobra especial relevancia en la relación de consumo. En efecto, la prevención de daños se encuentra previsto en el artículo 42 de la Constitución Nacional, constituyendo un derecho fundamental en el sistema protectorio del consumidor. De esta manera, el objetivo que se plantea es que mediante la imposición de daños punitivos se incentive a los proveedores a que adopten las medidas razonables de seguridad tendientes a prevenir los daños que injustamente pueda recibir, constituyendo un mecanismo eficaz de prevención al alcance del consumidor, principalmente para aquellos que se encuentre en una situación de vulnerabilidad.Facultad de Ciencias Jurídicas y Sociale

La función preventiva de los daños punitivos en las relaciones de consumo

En la presente ponencia se busca exponer que los daños punitivos regulados en el artículo 52 bis de la Ley de Defensa del Consumidor 24240 cumplen una función preventiva. En virtud de ello, cabe entender que la función preventiva reconocida en el Código Civil y Comercial de la Nación cobra especial relevancia en la relación de consumo. En efecto, la prevención de daños se encuentra previsto en el artículo 42 de la Constitución Nacional, constituyendo un derecho fundamental en el sistema protectorio del consumidor. De esta manera, el objetivo que se plantea es que mediante la imposición de daños punitivos se incentive a los proveedores a que adopten las medidas razonables de seguridad tendientes a prevenir los daños que injustamente pueda recibir, constituyendo un mecanismo eficaz de prevención al alcance del consumidor, principalmente para aquellos que se encuentre en una situación de vulnerabilidad.Facultad de Ciencias Jurídicas y Sociale

On the structure of large N cancellations in baryon chiral perturbation theory

We show how to compute loop graphs in heavy baryon chiral perturbation theory including the full functional dependence on the ratio of the Delta--nucleon mass difference to the pion mass, while at the same time automatically incorporating the 1/N cancellations that follow from the large-N spin-flavor symmetry of baryons in QCD. The one-loop renormalization of the baryon axial vector current is studied to demonstrate the procedure. A new cancellation is identified in the one-loop contribution to the baryon axial vector current. We show that loop corrections to the axial vector currents are exceptionally sensitive to deviations of the ratios of baryon-pion axial couplings from SU(6) values

Beads and Stamps in the Middle Orinoco: Archaeological Evidence for Interaction and Exchange in the Atures Rapids from AD 1000 to 1480

The area of the Atures Rapids in the Middle Orinoco River (Venezuela), where multiple Indigenous communities gathered to trade goods, has been identified as a prominent center of commerce since early colonial times. However, the exchange activities taking place there between local and nonlocal actors before European colonization are poorly understood, based only on the ethnohistoric record. This article presents an archaeometric analysis of stone beads and ceramic roller stamps, items previously associated with trade practices, from two recently excavated sites in the region, Picure (AD 1030–1480) and Rabo de Cochino (AD 1000–1440); it assesses their provenance, production, and value. We propose that Picure was a site of a bead-manufacturing workshop and a place where roller stamps were exchanged. The stamps were acquired and produced by different potting groups. Analysis of the chaîne opératoire and production techniques shows processes of adaptation and emulation associated with the multiple, multiethnic communities during the period from AD 1000 to 1480. Both beads and stamps are linked to identity regalia that were likely used as part of ceremonies taking place in the area of the Rapids, as indicated by the numerous and monumental petroglyphs found on the islands

Iron therapy substantially restores qEEG maturational lag among iron-deficient anemic infants

Objective: To use quantitative electroencephalography (qEEG) to assess the impact of iron-deficiency anemia on central nervous system maturation in the first year of life. Method: Twenty-five infants (3–12 months old) presenting ferropenic anemia (IDA) and 25 healthy controls (CTL1), matched by age/gender with the former, were studied in two stages. Electroencephalogram during spontaneous sleep was recorded from all participants; the fast Fourier transform was calculated to obtain absolute power (AP) and relative power (RP) qEEG measures. In the first stage, a qEEG comparison between CTL1 and IDA was performed. Second stage consisted in comparing qEEG of the IDA infants before and after supplementation with iron (IDA-IS group), and comparing qEEG of the IDA-IS group with another control age-matched group (CTL2). Non-parametric multivariate permutation tests (NPT) were applied to assess differences between CTL1 and IDA groups, as well as IDA vs. IDA-IS, and IDA-IS vs. CTL2. Results: More power in slow frequency bands and less power in fast frequency bands in 64% of IDA babies were observed. NPT evinced higher alpha AP and RP (P < 0.001), less theta AP, and less delta and theta RP in CTL1 than in IDA. After iron-restoration therapy, alpha AP and RP increased while theta AP and theta and delta RP decreased, reaching almost normal values. Discussion: This work reveals CNS developmental delay through the study of qEEG (less rapid and more slow frequencies) which recovered significantly with iron supplementation. It is concluded that IDA constitutes a high risk factor for a lag of CNS maturation.CONACYT-Project No. CO1/40257-A1

Entre La Pedrera y Araracuara: la arqueología del medio río Caquetá

Between La Pedrera and Araracuara: the archeology of the middle Caquetá river. The archaeology of the middle Caquetá River, in the Colombian Amazon, only became known in the 1970s through the results of pioneering research projects in Araracuara and La Pedrera. These investigations identified different ceramic sequences at both locales, documented a large number of petroglyphs, and for the first time recorded black and brown anthropic soils in the Northwest Amazon. Subsequent research emphasized the study of environmental archives (archaeobotanical and geoarchaeological) and recorded early and middle Holocene preceramic occupations. The latter are particularly important because associated archaeobotanical data suggest these populations cultivated a range of edible plants, several of them domesticated in other regions. The archaeology of the middle Caquetá River region, however, still holds a number of important questions about both pre-ceramic occupations and the extensive habitation sites of ceramic groups. As regards the latter, it is particularly important to evaluate the extent to which these occupations can be affiliated as part of the broad ceramic traditions known for Amazonia and the Orinoco basin. In order to evaluate the state of our knowledge and encourage the development of future archaeological research in the region, in this article we summarise existing information about the archaeology of the middle Caquetá River and present new preliminary data produced in recent years