Towards a Social Learning Space for Open Educational Resources

We identify a number of meanings of "Open", as part of the motivating rationale for a social media space tuned for learning, called SocialLearn. We discuss why online social learning seems to be emerging so strongly at this point, explore features of social learning, and identify some of the dimensions that we believe characterize the social learning design space, before describing the emerging design concept and implementation.

Conditioning of stochastic 3-D fracture networks to hydrological and geophysical data

The geometry and connectivity of fractures exert a strong influence on the flow and transport properties of fracture networks. We present a novel approach to stochastically generate three-dimensional discrete networks of connected fractures that are conditioned to hydrological and geophysical data. A hierarchical rejection sampling algorithm is used to draw realizations from the posterior probability density function at different conditioning levels. The method is applied to a well-studied granitic formation using data acquired within two boreholes located 6 m apart. The prior models include 27 fractures with their geometry (position and orientation) bounded by information derived from single-hole ground-penetrating radar (GPR) data acquired during saline tracer tests and optical televiewer logs. Eleven cross-hole hydraulic connections between fractures in neighboring boreholes and the order in which the tracer arrives at different fractures are used for conditioning. Furthermore, the networks are conditioned to the observed relative hydraulic importance of the different hydraulic connections by numerically simulating the flow response. Among the conditioning data considered, constraints on the relative flow contributions were the most effective in determining the variability among the network realizations. Nevertheless, we find that the posterior model space is strongly determined by the imposed prior bounds. Strong prior bounds were derived from GPR measurements and helped to make the approach computationally feasible. We analyze a set of 230 posterior realizations that reproduce all data given their uncertainties assuming the same uniform transmissivity in all fractures. The posterior models provide valuable statistics on length scales and density of connected fractures, as well as their connectivity. In an additional analysis, effective transmissivity estimates of the posterior realizations indicate a strong influence of the DFN structure, in that it induces large variations of equivalent transmissivities between realizations. The transmissivity estimates agree well with previous estimates at the site based on pumping, flowmeter and temperature data.

Niche dynamics in space and time.

Niche conservatism, the tendency of a species niche to remain unchanged over time, is often assumed when discussing, explaining or predicting biogeographical patterns. Unfortunately, there has been no basis for predicting niche dynamics over relevant timescales, from tens to a few hundreds of years. The recent application of species distribution models (SDMs) and phylogenetic methods to analysis of niche characteristics has provided insight to niche dynamics. Niche shifts and conservatism have both occurred within the last 100 years, with recent speciation events, and deep within clades of species. There is increasing evidence that coordinated application of these methods can help to identify species which likely fulfill one key assumption in the predictive application of SDMs: an unchanging niche. This will improve confidence in SDM-based predictions of the impacts of climate change and species invasions on species distributions and biodiversity.

Assessing sedimentary evolution by means of Sr-isotope ratios : 3 case studies on the Caribbean plate : (Cretaceous: Nicoya Peninsula, Costa Rica, Tertiary: Hess Rise, and La Désirade, Guadeloupe, France)

The understanding of sedimentary evolution is intimately related to the knowledge of the exact ages of the sediments. When working on carbonate sediments, age dating is commonly based on paleontological observations and established biozonations, which may prove to be relatively imprecise. Dating by means of strontium isotope ratios in marine bioclasts is the probably best method in order to precisely date carbonate successions, provided that the sample reflects original marine geochemical characteristics. This requires a precise study of the samples including its petrography, SEM and cathodoluminescence observations, stable carbon and oxygen isotope geochemistry and finally the strontium isotope measurement itself. On the Nicoya Peninsula (Northwestern Costa Rica) sediments from the Piedras Blancas Formation, Nambi Formation and Quebrada Pavas Formation were dated by the means of strontium isotope ratios measured in Upper Cretaceous Inoceramus shell fragments. Results have shown average 87Sr/86Sr values of 0.707654 (middle late Campanian) for the Piedras Blancas Formation, 0.707322 (Turonian-Coniacian) for the Nambi Formation and 0.707721 (late Campanian-Maastrichtian) for the Quebrada Pavas Formation. Abundant detrital components in the studied formations constitute a difficulty to strontium isotope dating. In fact, the fossil bearing sediments can easily contaminate the target fossil with strontium mobilized form basalts during diagenesis and thus the obtained strontium isotope ratios may be influenced significantly and so will the obtained ages. The new and more precise age assignments allow for more precision in the chronostratigraphic chart of the sedimentary and tectonic evolution of the Nicoya Peninsula, providing a better insight on the evolution of this region. Meteor Cruise M81 dredged shallow water carbonates from the Hess Rise and Hess Escarpment during March 2010. Several of these shallow water carbonates contain abundant Larger Foraminifera that indicates an Eocene-Oligocene age. In this study the strontium isotope values ranging from 0.707847 to 0.708238 can be interpreted as a Rupelian to Chattian age of these sediments. These platform sediments are placed on seamounts, now located at depths reaching 1600 m. Observation of sedimentologic characteristics of these sediments has helped to resolve apparent discrepancies between fossil and strontium isotope ages. Hence, it is possible to show that the subsidence was active during early Miocene times. On La Désirade (Guadeloupe France), the Neogene to Quaternary carbonate cover has been dated by microfossils and some U/Th-ages. Disagreements subsisted in the paleontological ages of the formations. Strontium isotope ratios ranging from 0.709047 to 0.709076 showed the Limestone Table of La Désirade to range from an Early Pliocene to Late Pliocene/early Pleistocene age. A very late Miocene age (87Sr/86Sr =0.709013) can be determined to the Detrital Offshore Limestone. The flat volcanic basement had to be eroded by wave-action during a long-term stable relative sea-level. Sediments of the Table Limestone on La Désirade show both low-stand and high-stand facies that encroach on the igneous basement, implying deposition during a major phase of subsidence creating accommodation space. Subsidence is followed by tectonic uplift documented by fringing reefs and beach rocks that young from the top of the Table Limestone (180 m) towards the present coastline. Strontium isotope ratios from two different fringing reefs (0.707172 and 0.709145) and from a beach rock (0.709163) allow tentative dating, (125ky, ~ 400ky, 945ky) and indicate an uplift rate of about 5cm/ky for this time period of La Désirade Island. The documented subsidence and uplift history calls for a new model of tectonic evolution of the area.

A continuous strain-space model of viral evolution within a host

Viruses rapidly evolve, and HIV in particular is known to be one of the fastest evolving human viruses. It is now commonly accepted that viral evolution is the cause of the intriguing dynamics exhibited during HIV infections and the ultimate success of the virus in its struggle with the immune system. To study viral evolution, we use a simple mathematical model of the within-host dynamics of HIV which incorporates random mutations. In this model, we assume a continuous distribution of viral strains in a one-dimensional phenotype space where random mutations are modelled by di ffusion. Numerical simulations show that random mutations combined with competition result in evolution towards higher Darwinian fitness: a stable traveling wave of evolution, moving towards higher levels of fi tness, is formed in the phenoty space.

The interactional space in CLIL (Content and Language Integrated Learning) and EFL (English as a Foreign Language) classrooms

Aquest estudi pretén investigar els intercanvis verbals mestre/a – aprenent(s) en dos contextos d'instrucció diferents: classes amb un enfocament AICLE (Aprenentatge Integrat de Continguts Curriculars i Llengua Estrangera) on s’aprenen continguts no lingüístics a través de l’anglès, per una banda, i classes 'tradicionals' d'anglès com a llengua estrangera, on l’anglès és alhora objecte d’estudi i vehicle de comunicació, per una altra banda. Més concretament, les preguntes que formula el/la mestre/a, la producció oral dels aprenents i el 'feedback' del/de la mestre/a en els episodis d’atenció a la forma s’han estudiat a la llum de les principals teories provinents del camp de l’Adquisició de Segones Llengües (SLA) per tal de demostrar el seu paper en l’aprenentatge de l’anglès. El corpus de dades prové de l’enregistrament de 7 sessions AICLE i d'11 sessions EFL enregistrades en format àudio i vídeo en dos centres públics d’Educació Primària (EP) de Catalunya. A cadascuna de les escoles, el/la mateix/a mestre/a és l’encarregat/da dels dos tipus d’instrucció amb el mateix grup d’aprenents (10-11 anys d’edat), fet que permet eliminar variables individuals com l'aptitud dels aprenents o l'estil del/de la mestre/a.Els resultats mostren un cert nombre de similituds discursives entre AICLE i EFL donat que ambdós enfocaments tenen lloc en el context-classe amb unes característiques ben definides. Tal com apunta la recerca realitzada en aquest camp, la instrucció AICLE reuneix un seguit de condicions idònies per un major desenvolupament dels nivells de llengua anglesa més enllà de les classes ‘tradicionals’ d’anglès. Malgrat això, aquest estudi sembla indicar que el potencial d'AICLE pel que fa a facilitar una exposició rica a l’anglès i una producció oral significativa no s’explota degudament. En aquest sentit, els resultats d’aquest estudi poden contribuir a la formació dels futurs professors d'AICLE si es busca l’assoliment d’una complementarietat d’ambdós contextos amb l’objectiu últim de millorar els nivells de domini de la llengua anglesa.

Coronary MR imaging using free-breathing 3D steady-state free precession with radial k-space sampling.

PURPOSE: To investigate the potential of free-breathing 3D steady-state free precession (SSFP) imaging with radial k-space sampling for coronary MR-angiography (MRA), coronary projection MR-angiography and coronary vessel wall imaging. MATERIALS AND METHODS: A navigator-gated free-breathing T2-prepared 3D SSFP sequence (TR = 6.1 ms, TE = 3.0 ms, flip angle = 120 degrees, field-of-view = 360 mm(2)) with radial k-space sampling (384 radials) was implemented for coronary MRA. For projection coronary MRA, this sequence was combined with a 2D selective aortic spin tagging pulse. Coronary vessel wall imaging was performed using a high-resolution inversion-recovery black-blood 3D radial SSFP sequence (384 radials, TR = 5.3 ms, TE = 2.7 ms, flip angle = 55 degrees, reconstructed resolution 0.35 x 0.35 x 1.2 mm(3)) and a local re-inversion pulse. Six healthy volunteers (two for each sequence) were investigated. Motion artifact level was assessed by two radiologists. Results: In coronary MRA, the coronary lumen was displayed with a high signal and high contrast to the surrounding lumen. Projection coronary MRA demonstrated selective visualization of the coronary lumen while surrounding tissue was almost completely suppressed. In coronary vessel wall imaging, the vessel wall was displayed with a high signal when compared to the blood pool and the surrounding tissue. No visible motion artifacts were seen. Conclusion: 3D radial SSFP imaging enables coronary MRA, coronary projection MRA and coronary vessel wall imaging with a low motion artifact level.

Anisotropic dispersion, space competition, and the slowdown of the Neolithic transition

The front speed of the Neolithic (farmer) spread in Europe decreased as it reached Northern latitudes, where the Mesolithic (huntergatherer) population density was higher. Here, we describe a reaction diffusion model with (i) an anisotropic dispersion kernel depending on the Mesolithicpopulation density gradient and (ii) a modified population growth equation. Both effects are related to the space available for the Neolithic population. The model is able to explain the slowdown of the Neolithic front as observed from archaeological data

Right coronary MR angiography at 7 T: a direct quantitative and qualitative comparison with 3 T in young healthy volunteers.

PURPOSE: To objectively compare quantitative parameters related to image quality attained at coronary magnetic resonance (MR) angiography of the right coronary artery (RCA) performed at 7 T and 3 T. MATERIALS AND METHODS: Institutional review board approval was obtained, and volunteers provided signed informed consent. Ten healthy adult volunteers (mean age ± standard deviation, 25 years ± 4; seven men, three women) underwent navigator-gated three-dimensional MR angiography of the RCA at 7 T and 3 T. For 7 T, a custom-built quadrature radiofrequency transmit-receive surface coil was used. At 3 T, a commercial body radiofrequency transmit coil and a cardiac coil array for signal reception were used. Segmented k-space gradient-echo imaging with spectrally selective adiabatic fat suppression was performed, and imaging parameters were similar at both field strengths. Contrast-to-noise ratio between blood and epicardial fat; signal-to-noise ratio of the blood pool; RCA vessel sharpness, diameter, and length; and navigator efficiency were quantified at both field strengths and compared by using a Mann-Whitney U test. RESULTS: The contrast-to-noise ratio between blood and epicardial fat was significantly improved at 7 T when compared with that at 3 T (87 ± 34 versus 52 ± 13; P = .01). Signal-to-noise ratio of the blood pool was increased at 7 T (109 ± 47 versus 67 ± 19; P = .02). Vessel sharpness obtained at 7 T was also higher (58% ± 9 versus 50% ± 5; P = .04). At the same time, RCA vessel diameter and length and navigator efficiency showed no significant field strength-dependent difference. CONCLUSION: In our quantitative and qualitative study comparing in vivo human imaging of the RCA at 7 T and 3 T in young healthy volunteers, parameters related to image quality attained at 7 T equal or surpass those from 3 T.

New ideas need new space

We develop a setting with weak intellectual property rights, where firms' boundaries, location and knowledge spillovers are endogenous. We have two main results. The first one is that, if communication costs increase with distance, entrepreneurs concerned about information leakage have a benefit from locating away from the industry center: distance is an obstacle to collusive trades between members andnon-members. The second result is that we identify a trade-off for the entrepreneur between owning a facility (controlling all its characteristics) and sharing a facility with a {\it non-member} (an agent not involved in production), therefore losing control over some of its characteristics. We focus on ``location" as the relevant characteristic of the facility, but location can be used as a spatial metaphor for other relevant characteristics of the facility. For theentrepreneur, sharing the facility with non-members implies that the latter, as co-owners, know the location (even if they do not have access to it). Knowledge of the location for the co-owners facilitates collusion with employees, what increases leakage. The model yields a benefit for new plants from spatial dispersion (locating at the periphery of the industry), particularly so for new plants of new firms.We relate this result with recent empirical findings on the dynamics of industry location.

A dynamic choice model of hybrid behavior in the attribute-space

This paper presents a dynamic choice model in the attributespace considering rational consumers that discount the future. In lightof the evidence of several state-dependence patterns, the model isfurther extended by considering a utility function that allows for thedifferent types of behavior described in the literature: pure inertia,pure variety seeking and hybrid. The model presents a stationaryconsumption pattern that can be inertial, where the consumer only buysone product, or a variety-seeking one, where the consumer buys severalproducts simultane-ously. Under the inverted-U marginal utilityassumption, the consumer behaves inertial among the existing brands forseveral periods, and eventually, once the stationary levels areapproached, the consumer turns to a variety-seeking behavior. An empiricalanalysis is run using a scanner database for fabric softener andsignificant evidence of hybrid behavior for most attributes is found,which supports the functional form considered in the theory.

Hybrid consumption paths in the attribute space: A model and application with scanner data

This paper presents and estimates a dynamic choice model in the attribute space considering rational consumers. In light of the evidence of several state-dependence patterns, the standard attribute-based model is extended by considering a general utility function where pure inertia and pure variety-seeking behaviors can be explained in the model as particular linear cases. The dynamics of the model are fully characterized by standard dynamic programming techniques. The model presents a stationary consumption pattern that can be inertial, where the consumer only buys one product, or a variety-seeking one, where the consumer shifts among varied products.We run some simulations to analyze the consumption paths out of the steady state. Underthe hybrid utility assumption, the consumer behaves inertially among the unfamiliar brandsfor several periods, eventually switching to a variety-seeking behavior when the stationary levels are approached. An empirical analysis is run using scanner databases for three different product categories: fabric softener, saltine cracker, and catsup. Non-linear specifications provide the best fit of the data, as hybrid functional forms are found in all the product categories for most attributes and segments. These results reveal the statistical superiority of the non-linear structure and confirm the gradual trend to seek variety as the level of familiarity with the purchased items increases.

Variance reduction methods for simulation of densities on Wiener space

We develop a general error analysis framework for the Monte Carlo simulationof densities for functionals in Wiener space. We also study variancereduction methods with the help of Malliavin derivatives. For this, wegive some general heuristic principles which are applied to diffusionprocesses. A comparison with kernel density estimates is made.