Using indirect blockmodeling for monitoring students roles in collaborative learning networks

Collaborative learning activities have shown to be useful to address educational processes in several contexts. Monitoring these activities is mandatory to determine the quality of the collaboration and learning processes. Recent research works propose using Social Network Analysis techniques to understand students' collaboration learning process during these experiences. Aligned with that, this paper proposes the use of the indirect blockmodeling network analytic technique for monitoring the behaviour of different social roles played by students in collaborative learning scenarios. The usefulness of this technique was evaluated through a study that analysed the students' interaction network in a collaborative learning activity. Particularly, we tried to understand the structure of the interaction network during that process. Preliminary results suggest that indirect blockmodeling is highly useful for inferring and analysing the students' social roles, when the behaviour of roles are clearly different among them. This technique can be used as a monitoring service that can be embedded in collaborative learning applications.Peer ReviewedPostprint (published version

FIRST REPORT OF USE OF LAND SNAILS FOR HETEROMYS GAUMERI (RODENTIA: HETEROMYIDAE) IN A SUBDECIDUOUS FOREST IN YUCATÁN, MÉXICO

Se presenta el primer registro de uso de caracoles terrestres por Heteromys gaumeri en la selva mediana subcaducifolia localizada en el Rancho Hobonil, Tzucacab, Yucatán, México. Siete por ciento de la población total (n= 789) de H. gaumeri usó caracoles que habitan en el área. Las especies fueron: Choanopoma largillierti y C. gaigei (Annulariidae), Neocyclotus dysoni (Cyclophoridae) y Drymaeus shattucki (Bulimulidae). Cincuenta y uno por ciento de las muestras de los roedores fueron hembras y el 49% machos. Los adultos representaron el 86% y los juveniles 14%. El uso de caracoles tuvo relación significativa entre sexos de los roedores y la estacionalidad (p< 0.01). Los caracoles fueron usados con mayor frecuencia en la estación de sequía por las hembras y por los machos adultos y juveniles en la de lluvias. Treinta y cinco por ciento de las hembras de la muestra que usaron caracoles estaban preñadas o lactantes. El género Choanopoma fue el más abundante y removido por H. gaumeri en ambas estaciones, mientras que Neocyclotus lo fue en la de lluvias y D. shattucki se encontró rara vez. Por lo observado consideramos que este ratón además de semillas come caracoles terrestres en esta región

Aspects of the Noisy Burgers Equation

The noisy Burgers equation describing for example the growth of an interface subject to noise is one of the simplest model governing an intrinsically nonequilibrium problem. In one dimension this equation is analyzed by means of the Martin-Siggia-Rose technique. In a canonical formulation the morphology and scaling behavior are accessed by a principle of least action in the weak noise limit. The growth morphology is characterized by a dilute gas of nonlinear soliton modes with gapless dispersion law with exponent z=3/2 and a superposed gas of diffusive modes with a gap. The scaling exponents and a heuristic expression for the scaling function follow from a spectral representation.Comment: 23 pages,LAMUPHYS LaTeX-file (Springer), 13 figures, and 1 table, to appear in the Proceedings of the XI Max Born Symposium on "Anomalous Diffusion: From Basics to Applications", May 20-24, 1998, Ladek Zdroj, Polan

A Pinned Polymer Model of Posture Control

A phenomenological model of human posture control is posited. The dynamics are modelled as an elastically pinned polymer under the influence of noise. The model accurately reproduces the two-point correlation functions of experimental posture data and makes predictions for the response function of the postural control system. The physiological and clinical significance of the model is discussed.Comment: uuencoded post script file, 17 pages with 3 figure

Kappa-symmetric Derivative Corrections to D-brane Dynamics

We show how the superembedding formalism can be applied to construct manifestly kappa-symmetric higher derivative corrections for the D9-brane. We also show that all correction terms appear at even powers of the fundamental length scale $l$. We explicitly construct the first potential correction, which corresponds to the kappa-symmetric version of the $\partial^4 F^4$, which one finds from the four-point amplitude of the open superstring.Comment: 20 pages. Minor changes, added reference

Update statistics in conservative parallel discrete event simulations of asynchronous systems

We model the performance of an ideal closed chain of L processing elements that work in parallel in an asynchronous manner. Their state updates follow a generic conservative algorithm. The conservative update rule determines the growth of a virtual time surface. The physics of this growth is reflected in the utilization (the fraction of working processors) and in the interface width. We show that it is possible to nake an explicit connection between the utilization and the macroscopic structure of the virtual time interface. We exploit this connection to derive the theoretical probability distribution of updates in the system within an approximate model. It follows that the theoretical lower bound for the computational speed-up is s=(L+1)/4 for L>3. Our approach uses simple statistics to count distinct surface configuration classes consistent with the model growth rule. It enables one to compute analytically microscopic properties of an interface, which are unavailable by continuum methods.Comment: 15 pages, 12 figure

Renormalization group study of one-dimensional systems with roughening transitions

A recently introduced real space renormalization group technique, developed for the analysis of processes in the Kardar-Parisi-Zhang universality class, is generalized and tested by applying it to a different family of surface growth processes. In particular, we consider a growth model exhibiting a rich phenomenology even in one dimension. It has four different phases and a directed percolation related roughening transition. The renormalization method reproduces extremely well all the phase diagram, the roughness exponents in all the phases and the separatrix among them. This proves the versatility of the method and elucidates interesting physical mechanisms.Comment: Submitted to Phys. Rev.

Functional characterization of a melon alcohol acyl-transferase gene family involved in the biosynthesis of ester volatiles. Identification of the crucial role of a threonine residue for enzyme activity

Volatile esters, a major class of compounds contributing to the aroma of many fruit, are synthesized by alcohol acyl-transferases (AAT). We demonstrate here that, in Charentais melon (Cucumis melo var. cantalupensis), AAT are encoded by a gene family of at least four members with amino acid identity ranging from 84% (Cm-AAT1/Cm-AAT2) and 58% (Cm-AAT1/Cm-AAT3) to only 22% (Cm-AAT1/Cm-AAT4). All encoded proteins, except Cm-AAT2, were enzymatically active upon expression in yeast and show differential substrate preferences. Cm-AAT1 protein produces a wide range of short and long-chain acyl esters but has strong preference for the formation of E-2-hexenyl acetate and hexyl hexanoate. Cm-AAT3 also accepts a wide range of substrates but with very strong preference for producing benzyl acetate. Cm-AAT4 is almost exclusively devoted to the formation of acetates, with strong preference for cinnamoyl acetate. Site directed mutagenesis demonstrated that the failure of Cm-AAT2 to produce volatile esters is related to the presence of a 268-alanine residue instead of threonine as in all active AAT proteins. Mutating 268-A into 268-T of Cm-AAT2 restored enzyme activity, while mutating 268-T into 268-A abolished activity of Cm-AAT1. Activities of all three proteins measured with the prefered substrates sharply increase during fruit ripening. The expression of all Cm-AAT genes is up-regulated during ripening and inhibited in antisense ACC oxidase melons and in fruit treated with the ethylene antagonist 1-methylcyclopropene (1-MCP), indicating a positive regulation by ethylene. The data presented in this work suggest that the multiplicity of AAT genes accounts for the great diversity of esters formed in melon

Renormalization group and nonequilibrium action in stochastic field theory

We investigate the renormalization group approach to nonequilibrium field theory. We show that it is possible to derive nontrivial renormalization group flow from iterative coarse graining of a closed-time-path action. This renormalization group is different from the usual in quantum field theory textbooks, in that it describes nontrivial noise and dissipation. We work out a specific example where the variation of the closed-time-path action leads to the so-called Kardar-Parisi-Zhang equation, and show that the renormalization group obtained by coarse graining this action, agrees with the dynamical renormalization group derived by directly coarse graining the equations of motion.Comment: 33 pages, 3 figures included in the text. Revised; one reference adde

Analysis of river bed dynamic evolution following a landslide dam

Landslides and debris flows can strongly interact with the river network and its mass transport processes, determining modifications of the river pattern with consequent effects on the hydrodynamic phenomena, alterations of the existing morphologies and possible interferences with anthropic works. Modifications of the cross section geometry and channel slope may produce changes in the sediment budget, with consequent repercussions on the stream evolutionary dynamics and its equilibrium configuration, leading to a new river branch arrangement. In this paper, investigations were carried out on a gravel-bed reach in the middle valley of the Noce River in Basilicata (Italy), which in 2007 suffered a progressive morpho-hydrodynamic change caused by a landslide. Because of the phenomenon complexity, mainly due to the mutual interaction between the landslide and the river transport dynamics, an integrated approach that combines field observations and numerical modelling in a spatial scale and natural environment, rarely available in literature, is suggested. The results highlight a satisfying correspondence between the altimetric profiles obtained through the numerical models and those deriving from the field surveys.Peer ReviewedPostprint (published version