The rr-Bell numbers

The notion of generalized Bell numbers has appeared in several works but there is no systematic treatise on this topic. In this paper we fill this gap. We discuss the most important combinatorial, algebraic and analytic properties of these numbers which generalize the similar properties of the Bell numbers. Most of these results seem to be new. It turns out that in a paper of Whitehead these numbers appeared in a very different context. In addition, we introduce the so-called $r$-Bell polynomials

Neural Stem Cell Spreading on Lipid Based Artificial Cell Surfaces, Characterized by Combined X-ray and Neutron Reflectometry

We developed a bioadhesive coating based on a synthetic peptide-conjugate (AK-cycloRGDfC]) which contains multiples of the arginyl-glycyl-aspartic acid (RGD) amino acid sequence. Biotinylated AK-cycloRGDfC] is bound to a supported lipid bilayer via a streptavidin interlayer. Layering, hydration and packing of the coating is quantified by X-ray and neutron reflectometry experiments. AK-cycloRGDfC] binds to the streptavidin interlayer in a stretched-out on edge configuration. The highly packed configuration with only 12% water content maximizes the number of accessible adhesion sites. Enhanced cell spreading of neural stem cells was observed for AK-cycloRGDfC] functionalized bilayers. Due to the large variety of surfaces which can be coated by physisorption of lipid bilayers, this approach is of general interest for the fabrication of biocompatible surfaces

RACINE2: A software application for processing spatial distribution of root lenght density from intersections on trench profiles

A field method has been developed to quantify root length density (RLD) from root intersection density (RID) measured on a trench-profile, using modelling RID-RLD relationships. For 2D spatial distribution mapping of RID (at 5-cm scale for example), the large amount of data is processed and converted into RLD and root distances (ARD) through modeling. Calculations and RLD mapping can be performed quickly using a new freeware: RACINE2, tailored to this field method. The software also allows a simple modeling of potential root exploration ratio in the soil (PRER) taking ARD into account. The software contains published models calculating RLD from RID for several crops (maize, sorghum, sugarcane, rice), ARD from RLD and PRER from RD. Models may be changed or added into RACINE2. RLD, ARD and PRER are calculated for each spatial unit. They can be mapped. Data can be exported to a spreadsheet or a surface mapping software for further analysis. It is also possible to import data into RACINE2 from a spreadsheet. RACINE2 thus makes studies about root-soil interactions, root growth and root uptake easier. Some examples of field results calculated by RACINE2 are presented (RLD, ARD and RER profiles and maps). They point out differences of PRER when taking (or not taking) into account 2D spatial root distribution. Taking into account spatial variability of root system in relation with soil characteristics may be important for root water and nutrient uptake in field conditions. (Résumé d'auteur

Sugarcane root system depth in three different countries

THE SUGARCANE root system depth is crucial as it determines the potential depth of soil available for water and nutrient uptake by the crop. It was reported in an early publication that these roots could grow quite deep (6 m), but otherwise very little data are available on the root system depth. The present study was carried out in three countries: Côte d'Ivoire (var. NCo376), Brazil (var. RB72454) and Réunion, France (var. R570) at various sugarcane growth stages. There were no shoot or root growth constraints (deep soil with enough water). For plant cane, the root front growth (RF in cm) was linear. In Côte d'Ivoire, from 45 to 160 days after planting (DAP), RF = 0.81 DAP; R2 = 0.91. On the island of Réunion, from 100 to 280 DAP, sugarcane root front growth was: RF = 0.56 DAP; R2 = 0.70. When DAP was replaced by thermal time (TT: sum of degree-days), the root front growth patterns were quite similar in Réunion and Côte d'Ivoire (RF = 0.045 and 0.049 TT, respectively). In ratoon conditions, RF was stable when roots from the previous cycle were still in the soil at the onset of the cropping season. Thus, the observed root depth was approximately 4 m in Brazil and Réunion, even though the environment and cultivars were different. These findings showed that, when there is no marked crop growth constraint, roots of modern commercial sugarcane varieties can grow to depths of about 4 m in ratoon crops. While these values were lower than those reported in previous studies, they were higher than those generally accepted at present. (Résumé d'auteur

Imagen icónica, imagen fantasmática. Reflexiones para el desarrollo de una pedagogía poética.

El ámbito de la creación es una especie de periferia, una trastienda desde la que el mundo se contempla como un artificio, como un conjunto de cosas realizadas (fabricadas, producidas o creadas). Iniciar al aprendiz en la creación supone conseguir que se traslade desde el mundo hasta su trastienda, desde la condición de usuario a la de creador. Este tránsito, que una vez experimentado parece que tan sólo requiere de un simple cambio de atención suele ir acompañado al principio de un gran esfuerzo que convierte dicho desplazamiento en una verdadera iniciación. Iniciarse en la creación implica adquirir una nueva mentalidad que haga compatible la consideración de la consistencia del mundo como conjunto de cosas que se reconocen, que funcionan y tienen sentido, con la inconsistencia del mundo como artificio. El creador, para serlo, necesita transitar con naturalidad entre ambos mundos

El espacio matriz y las arquitecturas incipientes. Reflexiones para el desarrollo de un apedagogía poética.

Una parte de la crisis de la pedagogía del llamado «dibujo artístico» en las escuelas de arquitectura, que se manifiesta en la gran divergencia de criterios sobre sus contenidos e incluso sobre su pertinencia, tiene su origen, desde nuestro punto de vista, en ciertos malentendidos sobre lo que la expresión «dibujo artístico» significa dentro y fuera de la enseñanza académica. Por «dibujo artístico» se puede entender el dibujo practicado por los artistas en esa situación límite que es crear cuando se intenta partir «desde cero» o, al menos, cuando se está dispuesto a poner en duda las configuraciones o las tipologías habituales dadas por buenas en cierto momento histórico

Spatial 2D distribution and depth of sugarcane root system in a deep soil

Sugarcane root system depth is a key parameter for water and mineral uptake but it is still very little known. Rooting depth of sugarcane (variety R570) has been determined in a deep soil in Reunion Island. In depth, it is therefore difficult to use the soil core method. Over a 1.5 m wide soil profile, roots were counted down the root front using a 5cmx5cm mesh grid to spatialize results. Data were entered into the RACINE2 software. It calculates root length density (RLD) and from RLD, distances between roots (ARD), producing, 2D root distribution maps and depth-related RLD profiles. Below 2 m, RLD was weak but not nil, and root fronts on the 4 measurement sites were 405, 390, 400, and 325 cm deep. RLD decreases with depth from .6 to .01 cm cm-3 at a 2 m depth. There was a power relationship between depth and RLD. ARD values are lower than 10 cm at 2-m depth. Below 3 meters, they fluctuated between 10 and 50 cm. If roots in the soil can absorb water up to 5 cm, roots below 1.5 m may allow survival in case of drought. The study was carried out in good crop conditions, in deep soil. Findings bring new important information for Reunion Island, where it was thought that RF was less than 2 m in depth (data used in crop models). These results also contribute to a better understanding of the sugarcane root system. (Résumé d'auteur