¿Qué responden los estudiantes del último año de educación secundaria, cuando en una situación fuera de contexto, se les pide escribir 10 oraciones que puedan deducirse de 3x+5y=10?

Este artículo tiene como objetivo difundir los resultados primarios de una encuesta realizada a 77 estudiantes del último nivel de educación secundaria en el marco de la educación pública de Uruguay, Argentina, Bolivia y Perú; los jóvenes entrevistados tienen entre 16 y 18 años de edad. Además, es una invitación a la comunidad de profesores de matemática a participar y continuar esta investigación con el fin de conocer las creencias de los estudiantes respecto a uno de los conceptos más trascendentes de la educación matemática como son las ecuaciones. Se pretende además sensibilizar en la urgencia de cuestionar y reformular nuestra práctica teniendo en cuenta los estudios académicos que se publican en torno al tema

Hacer matemática a nivel de enseñanza media, ¿es posible? El debate como herramienta

Hoy día no se concibe una clase de matemática en la que el profesor presente el conocimiento como "algo acabado", "hecho por otro", "sin imperfecciones". Se trata entonces, en la clase de matemática, de "hacer matemática" como lo hace el matemático. Pero ¿es esto posible a nivel de enseñanza media? Si es así, ¿cómo? Compartiremos parte de nuestra experiencia trabajando con la herramienta del debate y presentaremos una metodología de trabajo en el aula que permite construir el conocimiento por parte de los alumnos a la vez que contribuye a la evolución de la argumentación en la clase de matemática

The fate of intertidal microphytobenthos carbon: an in situ ¹³C-labeling study

At two intertidal sites (one sandy and one silty, in the Scheldt estuary, The Netherlands), the fate of microphytobenthos was studied through an in situ 13C pulse- chase experiment. Label was added at the beginning of low tide, and uptake of 13C by algae was linear during the whole period of tidal exposure (about 27 mg m-2 h-1 in the top millimeter at both sites). The 13C fixed by microphytobenthos was rapidly displaced toward deeper sediment layers (down to 6 cm), in particular at the dynamic, sandy site. The residence times of microphytobenthos with respect to external losses (resuspension and respiration) were about 2.4 and 5.6 d at the sandy and silly stations, respectively. The transfer of carbon from microphytobenthos to benthic consumers was estimated from the appearance of 13C in bacterial biomarkers, handpicked nematodes, and macrofauna. The incorporation of 13C into bacterial biomass was quantified by carbon isotope analysis of polar lipid derived fatty acids specific for bacteria. The bacterial polar lipid-derived fatty acids (i14:0, i15:0, a15:0, i16:0, and 18:1 omega 7c) showed rapid, significant transfer from benthic algae to bacteria with maximum labeling after 1 d. Nematodes became enriched after 1 h, and 13C assimilation increased until day 3. Microphytobenthos carbon entered all heterotrophic components in proportion to heterotrophic biomass distribution (bacteria > macrofauna > meiofauna). Our results indicate a central role for microphytobenthos in moderating carbon flow in coastal sediments

Análisis de una clase filmada

Realizamos un taller en el que presentamos una clase filmada en un curso de matemática en el último año de enseñanza media superior (bachillerato). en esa clase se trabajó con una tarea de final abierto (Zaslavsky, 1995, 2008). en el taller analizamos la clase utilizando el marco desarrollado por Karsenty & Arcavi (2017). procuramos privilegiar, en el análisis, el estudio de la tarea y de las interacciones que se dieron en el aula (Yackel, 2004)

First passage time statistics of Brownian motion with purely time dependent drift and diffusion

Systems where resource availability approaches a critical threshold are common to many engineering and scientific applications and often necessitate the estimation of first passage time statistics of a Brownian motion (Bm) driven by time-dependent drift and diffusion coefficients. Modeling such systems requires solving the associated Fokker-Planck equation subject to an absorbing barrier. Transitional probabilities are derived via the method of images, whose applicability to time dependent problems is shown to be limited to state-independent drift and diffusion coefficients that only depend on time and are proportional to each other. First passage time statistics, such as the survival probabilities and first passage time densities are obtained analytically. The analysis includes the study of different functional forms of the time dependent drift and diffusion, including power-law time dependence and different periodic drivers. As a case study of these theoretical results, a stochastic model for water availability from surface runoff in snowmelt dominated regions is presented, where both temperature effects and snow-precipitation input are incorporated

Seasonal Growth Rate of the Sponge Haliclona oculata (Demospongiae: Haplosclerida)

The interest in sponges has increased rapidly since the discovery of potential new pharmaceutical compounds produced by many sponges. A good method to produce these compounds by using aquaculture of sponges is not yet available, because there is insufficient knowledge about the nutritional needs of sponges. To gain more insight in the nutritional needs for growth, we studied the growth rate of Haliclona oculata in its natural environment and monitored environmental parameters in parallel. A stereo photogrammetry approach was used for measuring growth rates. Stereo pictures were taken and used to measure volumetric changes monthly during 1 year. Volumetric growth rate of Haliclona oculata showed a seasonal trend with the highest average specific growth rate measured in May: 0.012 ± 0.004 day−1. In our study a strong positive correlation (p < 0.01) was found for growth rate with temperature, algal biomass (measured as chlorophyll a), and carbon and nitrogen content in suspended particulate matter. A negative correlation (p < 0.05) was found for growth rate with salinity, ammonium, nitrate, nitrite, and phosphate. No correlation was found with dissolved organic carbon, suggesting that Haliclona oculata is more dependent on particulate organic carbon