Los conceptos de biología adquiridos en el proceso de aprendizaje

AbstractAn extensive survey is given of the properties of various specification mechanisms based on initial algebra semantics

Partial arithmetical data types of rational numbers and their equational specification

Upon adding division to the operations of a field we obtain a meadow. It is conventional to view division in a field as a partial function, which complicates considerably its algebra and logic. But partiality is one out of a plurality of possible design decisions regarding division. Upon adding a partial division function ÷ to a field Q of rational numbers we obtain a partial meadow Q (÷) of rational numbers that qualifies as a data type. Partial data types bring problems for specifying and programming that have led to complicated algebraic and logical theories – unlike total data types. We discuss four different ways of providing an algebraic specification of this important arithmetical partial data type Q (÷) via the algebraic specification of a closely related total data type. We argue that the specification method that uses a common meadow of rational numbers as the total algebra is the most attractive and useful among these four options. We then analyse the problem of equality between expressions in partial data types by examining seven notions of equality that arise from our methods alone. Finally, based on the laws of common meadows, we present an equational calculus for working with fracterms that is of general interest outside programming theory

Remote Sensing of Permafrost by Ground-Penetrating Radar at Two Airports in Arctic Canada

Over a cycle of seasons, ground-penetrating radar studies were carried out at Inuvik and Rankin Inlet, Northwest Territories. The two airports are part of the Forward Operating Location (FOL) program of the Department of National Defence and have been slated for significant upgrading of runways, taxiways and parking aprons. This provided a good opportunity to investigate the extent of permafrost and its seasonal variation at two locations distributed over a wide geographic area. The study method involved specific and repeated traverses with a Pulse EKKO III ground-penetrating radar unit. The survey was successful in locating massive ice bodies, imaging several existing problem areas beneath runways and mapping the seasonal depth of thaw in permafrost. The study results imply that future monitoring at FOL sites should be continued in light of suggested ground stability problems due to global warming.Key words: Canadian Arctic, ground-penetrating radar, permafrost, global warming,  airport, Forward Operating LocationMot clés: Arctic canadien,  géoradar, pergélisol, réchauffement atmosphéric, aéroport, Emplacemen Avancés d’opération

Recovery from addiction: Behavioral economics and value-based decision making.

Behavioral economics provides a general framework to explain the shift in behavioral allocation from substance use to substance-free activities that characterizes recovery from addiction, but it does not attempt to explain the internal processes that prompt those behavioral changes. In this article we outline a novel analysis of addiction recovery based on computational work on value-based decision making (VBDM), which can explain how people with addiction are able to overcome the reinforcement pathologies and decision-making vulnerabilities that characterize the disorder. The central tenet of this account is that shifts in molar reinforcer preferences over time from substance use to substance-free activities can be attributed to changes in evidence accumulation rates and response thresholds in the context of choices involving substance use and substance-free alternatives. We discuss how this account can be reconciled with the established mechanisms of action of psychosocial interventions for addiction and demonstrate how it has the potential to empirically address longstanding debates regarding the nature of impairments to self-control in addiction. We also highlight conceptual and methodological issues that require careful consideration in translating VBDM to addiction and recovery