Complex Remanence vs. Simple Persistence: Are Hysteresis and Unit-Root Processes observationally equivalent?

The hysteresis terminology has mainly been used in two fields of economics, unemplyment and international trade, with a different meaning however, involving either linear autoregressive macro behaviour or non- linear heterogenous mico behaviour. There may nonetheless be observational equivalence between the 'persistence' characterising unit- root processes and the 'remanence' created by the aggregation of non- linear dynamics. Stochastic simulations are employed to analyse the properties of the output of an hysteretic system, subject to white noise and random walk inputs. Non-linear hysteretic systems are found to generate a sizeable proportion - two-thirds - of stationary output from stationary input, and to possibly generate an output cointegrated with the corresponding input. Such processes therefore appear significantly different from an integrated process. This stresses the specific relevance of a non-linear approach to hysteresis.hysteresis, non-linearity, aggregation, heterogeneity, experimental economics

Arthropod Communities and Red-headed Woodpecker (Melanerpes erythrocephalus) Habitat Selection

Red-headed woodpecker populations are near-threatened. Their habitat selection and reproductive success may be related to the availability of arthropods. We sampled the arthropod community within 0.04 ha plots surrounding known nests and compared these findings to plots without nests in the same fragments of forest or park in Cook County, IL. After 14 days, the traps were recovered, yielding close to 45,000 arthropods across 10 orders. Nest and control site differences were not statistically significant. Differences between park and forest diversity were not statistically significant either, but the greater diversity values in forests were consistent with expectations. We conclude that factors other than arthropod availability are likely controlling red-headed woodpecker habitat selection

EVALUATION OF PHENYLALANINE ISOTOPES USING AN ISOLATED ORGAN PERFUSION MODEL

The objective of the research was to evaluate the possibility of isotopic discrimination between two isotopomers of phenylalanine during the hydroxylation to tyrosine. Phenylalanine hydroxylation of L-[1-13C]phenylalanine and L-{ring- 2H5]phenylalanine were evaluated in three in vitro experiments, as well as an isolated liver perfusion model. The in vitro experiment involved an assay system using purified phenylalanine hydroxylase enzyme in a buffer medium. The isolated liver perfusion was set up to examine the first-pass hepatic metabolism of phenylalanine. Tyrosine production from the unlabeled phenylalanine as well as the two isotopomers was measured by spectrophotometric assay and high-performance liquid chromatography (HPLC). Gas chromatography-mass spectrometry (GC-MS) analysis was used to measure the enrichment of 13C-tyrosine and 2H4-tyrosine in a third in vitro experiment as well as labeled tyrosine and phenylalanine enrichments in the liver perfusion experiments. In a kinetic assay, the rate of production of 2H4-tyrosine (from hydroxylation 2H5- phenylalanine), was found to be significantly lower (p < 0.01) than the rate of production of unlabeled or 13C-tyrosine. When overall tyrosine production was measured by HPLC, the 2H4 -tyrosine production was found to be significantly lower than from both unlabeled and 13C-tyrosine (p 0.05) or tyrosine (p > 0.05) enrichments. The lack of significant difference between enrichments of 13C-phenylalanine and 2H5-phenylalanine, or 13C- tyrosine and 2H4-tyrosine indicates that the discrimination at the enzymatic level is not large enough to affect hepatic enrichment. This study suggests that, although discrimination may exist between L-[1-13C]phenylalanine and L-[ring-2H5]phenylalanine, the liver is not likely the site for such discrimination

El eterno retorno de las crisis financieras... O cómo frenarlas

Nos damos el lujo de reproducir la conferencia que realizó el economista francés Frédéric Lordon en la Universidad Nacional de La Plata invitado por el CIEPYC. Analizó el germen y la evolución de las crisis financieras que se vienen produciendo en el sistema financiero, haciendo hincapié en el último episodio ocurrido a raíz de las hipotecas subprime en los Estados Unidos. También planteó propuestas de política monetaria para evitar el surgimiento de burbujas.Conferencia organizada por el CIEPYC en la Biblioteca de la Universidad Nacional de La Plata el día 21 de noviembre de 2007.Centro de Investigación en Economía Política y Comunicación (CIEPYC

Los fondos de pensiones como proyecto político y como utopía social

Este capítulo no considera el ascenso d

Petrophysical Characterization of Shaly Sand Reservoirs in Well UK-05 Eastern Niger Delta Basin, Nigeria

A petrophysical evaluation of Well UK-05 in the eastern Niger Delta Basin was carried out in order to determine reservoir zones, their porosity, permeability, fluid saturation and the effect of shaliness on the petrophysical parameters. Using interactive petrophysics software version 3.5, twenty five (25) reservoir zones were identified. The porosity values range from 15.77- 4.66% and permeability from 2.76-546.54 mD. The Archie’s, Simandoux, Dual-porosity, Waxman and Smith, and the Indonesian models were used to determine the fluid saturation. The water and hydrocarbon saturation values using the Indonesian model are 21.67-50.49% and 49.51-78.33% respectively. They slightly differ from the ones obtained using Simandoux, Dual Water and Waxman and Smith model (20.72-49.88% and 50.12- 9.22%, 18.26-50.49% and 49.51-81.74%, 14.67-48.26% and 51.74-5.33% for water and hydrocarbon saturation respectively). The interpreted lithology shows that the formation penetrated by the Well UK-05 is dominated by alternating sands and shales with the sand being the dominant lithology. These lithostratigraphic characteristics correspond to those of the parallic Agbada Formation. The effective porosity values obtained range from 14.93 to 34.66%, which are lower than 0.013% to 94.08% obtained by other authors since they did not take into consideration the effect of shaliness. This shows that the more the shale volume, the higher the uncertainty of actual porosity of the reservoir