Luis Flores

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Armando Marques-Guedes

UNL - New University of Lisbon

Felix Ovejero

Universitat de Barcelona

Martin Retamozo

Universidad Nacional de La Plata

Hugo Cadenas

Universidad de Chile

Eduardo Maura

Universidad Complutense de Madrid

Revista Ingenieria Industrial

Universidad del Bio-bio

Werner Bonefeld

University of York

Ricardo Milla Toro

EHESS-Ecole des hautes études en sciences sociales

Rodrigo G de Azevedo

Pontifícia Universidade Católica do Rio Grande do Sul

AD-Minister (Journal)

Universidad EAFIT

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Papers by Luis Flores

Limited Capacity of Human Adult Islets Expanded In Vitro to Redifferentiate Into Insulin-Producing Cells

Diabetes, 2007

Limited organ availability is an obstacle to the widespread use of islet transplantation in type ... more Limited organ availability is an obstacle to the widespread use of islet transplantation in type 1 diabetic patients. To address this problem, many studies have explored methods for expanding functional human islets in vitro for diabetes cell therapy. We previously showed that islet cells replicate after monolayer formation under the influence of hepatocyte growth factor and selected extracellular matrices. However, under these conditions, senescence and loss of insulin expression occur after &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;15 doublings. In contrast, other groups have reported that islet cells expanded in monolayers for months progressed through a reversible epithelial-to-mesenchymal transition, and that on removal of serum from the cultures, islet-like structures producing insulin were formed (1). The aim of the current study was to compare the two methods for islet expansion using immunostaining, real-time quantitative PCR, and microarrays at the following time points: on arrival, after monolayer expansion, and after 1 week in serum-free media. At this time, cell aliquots were grafted into nude mice to study in vivo function. The two methods showed similar results in islet cell expansion. Attempts at cell differentiation after expansion by both methods failed to consistently recover a beta-cell phenotype. Redifferentiation of beta-cells after expansion is still a challenge in need of a solution.

Direct and continuous measurements of the irreversibility line of high-T[sub c] superconductors using an automatic PID controller

by Luis Flores and Ernesto Altshuler

A system for the direct and continuous determination of the irreversibility line in high T c supe... more A system for the direct and continuous determination of the irreversibility line in high T c superconductors is described. The system, based on a standard ac susceptometer, operates by applying a controlled dc field to the sample that maximizes the imaginary ͑out-of-phase͒ component of the ac susceptibility. This control is achieved using a proportional-integral-derivative loop with the reference set to zero and with the magnetic field derivative of the imaginary component of the ac susceptibility taken as the feedback sample ͑error signal͒. To obtain a dc voltage proportional to this derivative a double lock-in detection scheme is used. This apparatus is able to carry out a continuous measurement of this line by sweeping the temperature in the range of interest while the sample is maintained, by the controller, at the irreversibility magnetic field at each temperature. Hence, the whole process is accomplished in the same time as a typical resistivityversus-temperature measurement, which is faster than other methods.

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