On Masked Pre-training and the Marginal Likelihood

Masked pre-training removes random input dimensions and learns a model that can predict the missing values. Empirical results indicate that this intuitive form of self-supervised learning yields models that generalize very well to new domains. A theoretical understanding is, however, lacking. This paper shows that masked pre-training with a suitable cumulative scoring function corresponds to maximizing the model's marginal likelihood, which is de facto the Bayesian model selection measure of generalization. Beyond shedding light on the success of masked pre-training, this insight also suggests that Bayesian models can be trained with appropriately designed self-supervision. Empirically, we confirm the developed theory and explore the main learning principles of masked pre-training in large language models

Combining Fine- and Coarse-Grained Classifiers for Diabetic Retinopathy Detection

Visual artefacts of early diabetic retinopathy in retinal fundus images are usually small in size, inconspicuous, and scattered all over retina. Detecting diabetic retinopathy requires physicians to look at the whole image and fixate on some specific regions to locate potential biomarkers of the disease. Therefore, getting inspiration from ophthalmologist, we propose to combine coarse-grained classifiers that detect discriminating features from the whole images, with a recent breed of fine-grained classifiers that discover and pay particular attention to pathologically significant regions. To evaluate the performance of this proposed ensemble, we used publicly available EyePACS and Messidor datasets. Extensive experimentation for binary, ternary and quaternary classification shows that this ensemble largely outperforms individual image classifiers as well as most of the published works in most training setups for diabetic retinopathy detection. Furthermore, the performance of fine-grained classifiers is found notably superior than coarse-grained image classifiers encouraging the development of task-oriented fine-grained classifiers modelled after specialist ophthalmologists.Comment: Pages 12, Figures

Los avances tecnológicos y la ciencia del lenguaje

La ciencia moderna nace de la conjunción entre postulados teóricos y el desarrollo de una infraestructura tecnológica que permite observar los hechos de manera adecuada, realizar experimentos y verificar las hipótesis. Desde Galileo, ciencia y tecnología han avanzado conjuntamente. En el mundo occidental, la ciencia ha evolucionado desde pro-puestas puramente especulativas (basadas en postulados apriorísticos) hasta el uso de métodos experimentales y estadísticos para explicar mejor nuestras observaciones. La tecnología se hermana con la ciencia facilitando al investigador una aproximación adecuada a los hechos que pretende explicar. Así, Galileo, para observar los cuerpos celestes, mejoró el utillaje óptico, lo que le permitió un acercamiento más preciso al objeto de estudio y, en consecuencia, unos fundamentos más sólidos para su propuesta teórica. De modo similar, actualmente el desarrollo tecnológico digital ha posibilitado la extracción masiva de datos y el análisis estadístico de éstos para verificar las hipótesis de partida: la lingüística no ha podido dar el paso desde la pura especulación hacia el análisis estadístico de los hechos hasta la aparición de las tecnologías digitales

Amaranthus palmeri a New Invasive Weed in Spain with Herbicide Resistant Biotypes

Amaranthus palmeri is the most prominent invasive weed in agricultural land from North America, partly due to its propensity to evolve resistance to multiple herbicide sites of action. In the last two decades, reports of this species have increased throughout the American continent and occasionally in other continents. In 2007, A. palmeri populations were found in three localities in northeastern Spain, and they are still present today. To determine whether these three populations resulted from a common or independent introduction events¿and when and from where they could have occurred¿research was carried out aiming to characterize the resistance profile and mechanisms to 5-enolpyruvylshikimate-3-phosphate synthase-and acetolactate synthase (ALS)-inhibiting herbicides and to analyze the relationship between these three populations using inter simple sequence repeat DNA fingerprinting. Dose-response trials confirmed that the three populations were susceptible to glyphosate but resistant to nicosulfuron-methyl. Resistance to ALS inhibitors was due to several amino acid substitutions in positions Pro197, Trp574 and Ser653. Moreover, the substitutions Ser653Ile and Pro197Thr are described for the first time in this species. At field-labeled rates, all populations were fully controlled with alternative herbicides with other sites of action. Amaranthus palmeri individuals were clustered in three groups based on unweighted pair group method with arithmetic mean analysis, which corresponded to the three sampled populations, with a 67% of genetic relationship among them. Considering this high genetic variability and the different positions and amino acid substations found between populations, it was hypothesized that different colonization events occurred from the American continent probably prior to the introduction of glyphosate resistant crops. Prevention from new introductions is warranted because new herbicide resistance traits could arrive, complicating the management of this invasive weed species, while managing or eradicating the already established populations.This work was funded by Spanish Government through the project AGL2017-83325-C4-2-R (AEI/FEDER/UE). Joel Torra acknowledges support from the Spanish Ministry of Science, Innovation and Universities (grant Ramon y Cajal RYC2018-023866-I)

Toda la ciudad era un paisaje. Naturaleza, arquitectura y pintura en la obra de Wang Shu

Según Wang Shu, su arquitectura produce una experiencia análoga a la que ofrece la contemplación de la pintura tradicional china. Esta se diferencia del arte occidental en que no trata de expresar la sensibilidad visual de su autor a través de la descripción de la luz, el espacio y los objetos. No define los temas a través del color sino perfilándolos con líneas oscuras y unas pocas tonalidades. El pintor no trabaja del natural; normalmente es, también, filósofo y poeta, además de dominar muchas otras disciplinas técnicas y humanísticas; vive aislado en los parajes elegidos antes de pintarlos, para captar el funcionamiento estructural del mundo natural del que forma parte y compartir después, a través de su arte, ese conocimiento. Provocar ese mismo tipo de vivencias es también para Wang Shu el principal propósito de su arquitectura

Predictive phytotoxic value of water-soluble allelochemicals in plant extracts for choosing a cover crop or mulch for specific weed control

Cover crops and mulches have become an alternative for soil management in vineyards due to the agronomic, environmental, and economic advantages, especially the possibility of weed control. Implicitly to this objective lies the idea of assessing the potential herbicide effect of the allelochemicals released by different cover crop and mulch species. With this objective, the present work evaluated the phytotoxic effects of 12 aqueous extracts of selected species with potential use as a cover crop or mulch: a Bromus species mixture (B. hordeaceus L. and B. rubens L.), Festuca arundinacea Schreb., Hordeum murinum L., H. vulgare L., Vulpia ciliata Dumort.,  Medicago rugosa Desr., M. sativa L., Trifolium subterraneum L., T. incarnatum L., Phacelia tanacetifolia Benth., Sinapis alba L., and Pinus sylvestris L.,on the germination and early growth of three troublesome weeds (Conyza bonariensis (L.) Cronquist, Aster squamatus (Spreng.) Hieron, and Bassia scoparia (L.) A. J.). The different in vitro bioassays showed that aqueous extracts of some species significantly inhibited or reduced germination and root and shoot growth of the target weed species in a dose-response manner. Germination of A. squamatus and C. bonariensis was reduced by 100-80% by the different extracts applied at 50% concentration, and completely blocked at 100% concentration, except for M rugosa extract to which both species showed less sensitivity. Root elongation of A. squamatus was absolutely inhibited under every extract and concentration, whereas C. bonariensis root growth showed only some tolerance to the crude extracts of F. arundinaceaand P. sylvestris. Bassia scoparia was relatively tolerant to the aqueous plant extracts, except for T. subterraneum crude extract, which reduced total germination by 80%; otherwise, B. scoparia showed higher general sensitivity of shoot growth than the other two weed species. The chemical profiles of phenolic compounds of the aqueous extracts were obtained and identified by HPLC-DAD, the phenolic profiles of H. murinum, V. ciliata, and M. rugosa being reported in this work for the first time. Using stepwise regression, the influence of certain phenolic compounds from the aqueous extracts on the germination and early growth of weeds was predicted. Among other significant compounds, the flavonoid naringenin identified in T. subterraneumaqueous extract at 8.09 µg·mL-1 was predicted to underlie its specific phytotoxicity on B. scoparia germination. These results support the use of cover crops and mulches in weed management and can help to select the most suitable species to adopt according to the target weed species. Highlights • The phytotoxic nature of the aqueous extracts of twelve conventional and novel cover crops and mulch species was demonstrated on three troublesome weed species in vineyards. • Phenolic acids and flavonoids of the twelve aqueous extracts were identified and quantified by HPLC-DAD, and, by regression analysis, some allelochemicals were postulated as responsible for the phytotoxic effects. • The water-soluble phenolic profiles of three potential cover crops, namely Hordeum murinum, Vulpia ciliata, and Medicago rugosa, are reported for the first time. • In vitro germination and early root growth of Conyza bonariensis and Aster squamatus were almost entirely restricted by any of the twelve plants' aqueous extracts and presumably by the joint action of their particular allelopathic compounds. • Bassia scoparia germination was relatively much less sensitive to the extracts, except for Trifolium subterraneum, for which the flavonoid naringenin was predicted to underlie its specific phytotoxicity

Forschendes Lernen. Konzeptuelle Grundlagen und Potenziale digitaler Medien

Im folgenden Artikel wird dargelegt, was unter dem Konzept des forschenden Lernens zu verstehen ist und welche Einsatzmöglichkeiten sich für das forschende Lernen im Kontext Universität ergeben. Dabei werden speziell diejenigen Merkmale theoretisch herausgearbeitet, die aus Lehrendenperspektive Anknüpfungspunkte für einen prozessbegleitenden Medieneinsatz bieten. Exemplarisch wird eine Lehrveranstaltung angeführt, die auf Fallebene zeigt, wie ein forschungsorientiertes Seminar um digitale Medien angereichert werden kann und welche Chancen und Grenzen sich bei der selbstgesteuerten Verwendung digitaler Medienangebote ergeben. Die Evaluation des Seminars zeigt, dass die Studierenden einen großen Lernzuwachs erleben, jedoch teilweise durch die Offenheit des Lernens überfordert sind. Diese und andere Gründe führen dazu, dass die von Lehrenden vorgeschlagenen Medienangebote selten bis kaum genutzt werden. Zudem sehen Lernende die Qualität virtuell distribuierter Inhalte kritisch, was sich auf die Akzeptanz und die Nutzung der vorhandenen digitalen Medienangebote auswirkt. (DIPF/Orig.

Evaluación del proceso de fatiga de mezclas asfálticas mediante un nuevo procedimiento cíclico de barrido de deformaciones: EBADE

This paper presents a new experimental procedure to characterize fatigue behaviour of asphalt mixtures, called EBADE procedure. It has been developed at the Road Research Laboratory based in the Technical University of Catalonia (UPC-Barcelona Tech). The procedure consists of applying cyclic tension-compression loads in a displacement-controlled uniaxial test at different strain levels. By doing so it is possible to obtain two key strain values in the characterization of asphalt mixtures fatigue behaviour. Those are the strain level at which the mixture does not undergo fatigue (endurance limit) and the strain level at which critical fatigue failure takes place. In addition, EBADE procedure allows one to emulate the fatigue process a pavement goes through when it has to sustain thermal stresses. In this paper the EBADE procedure is detailed, and the main results and conclusions obtained in the experimental study carried out in order to evaluate its sensitivity are exposed. En este artículo se presenta un nuevo procedimiento experimental, de rápida ejecución, para caracterizar la respuesta al fallo por fatiga de las mezclas asfálticas, el procedimiento EBADE. Su desarrollo se ha realizado en el Laboratorio de Caminos de la Universidad Politécnica de Cataluña, y su metodología consiste en aplicar a probetas prismáticas de mezcla asfáltica series de ciclos de carga de tensión-compresión a distintos niveles de deformación, los cuales aumentan gradualmente hasta producir el fallo por fatiga de la mezcla. Este procedimiento permite caracterizar las mezclas asfálticas por medio de la obtención de los dos niveles de deformación relacionados directamente con el comportamiento a fatiga de las mezclas: el nivel de deformación debajo del cual la mezcla asfáltica no sufre deterioro y el nivel de deformación en el que tiene lugar la rápida propagación del fallo por fatiga. A su vez, el procedimiento EBADE permite simular el proceso de fatiga de las mezclas asfálticas cuando estas están bajo estados tensionales producto de las variaciones térmicas. En este trabajo de investigación se da a conocer, tanto la metodología del procedimiento EBADE, como los resultados y principales conclusiones del estudio experimental llevado a cabo para demostrar la sensibilidad y ventajas del procedimiento propuesto.Postprint (published version