There are many methods for explaining why a machine learning model produces a given output in response to a given input. The relative merits of these methods are often debated using theoretical ...arguments and illustrative examples. This paper provides a large-scale empirical test of four widely used explanation methods by comparing how well their algorithmically generated denial reasons align with lender-provided denial reasons using a dataset of home mortgage applications. On a held-out sample of 10,000 denied applications, Shapley additive explanations (SHAP) correspond most closely with lender-provided reasons. SHAP is also the most computationally efficient. As a second contribution, this paper presents a method for computing integrated gradient explanations that can be used for non-differentiable models such as XGBoost.
Evaluating the importance and the strength of empirical evidence requires asking three questions: First, what are the practical implications of the findings? Second, how precise are the estimates? ...Confidence intervals provide an intuitive way to communicate precision. Although nontechnical audiences often misinterpret confidence intervals (CIs), I argue that the result is less dangerous than the misunderstandings that arise from hypothesis tests. Third, is the model correctly specified? The validity of point estimates and CIs depends on the soundness of the underlying model.
A central current debate in community ecology concerns the relative importance of deterministic versus stochastic processes underlying community structure. However, the concept of stochasticity ...presents several profound philosophical, theoretical and empirical challenges, which we address here. The philosophical argument that nothing in nature is truly stochastic can be met with the following operational concept of neutral stochasticity in community ecology: change in the composition of a community (i.e. community dynamics) is neutrally stochastic to the degree that individual demographic events – birth, death, immigration, emigration – which cause such changes occur at random with respect to species identities. Empirical methods for identifying the stochastic component of community dynamics or structure include null models and multivariate statistics on observational species-by-site data (with or without environmental or trait data), and experimental manipulations of 'stochastic' species colonization order or relative densities and frequencies of competing species. We identify the fundamental limitations of each method with respect to its ability to allow inferences about stochastic community processes. Critical future needs include greater precision in articulating the link between results and ecological inferences, a comprehensive theoretical assessment of the interpretation of statistical analyses of observational data, and experiments focusing on community size and on natural variation in species colonization order.
La productividad literaria de García Lorca fue casi constante durante el período 1916-1936. Sin embargo, en la primera mitad de 1929 encontramos un hiato curioso, cuando no escribió casi nada nuevo. ...Este estudio procura documentar los meses de enero a junio de 1929 y explorar la evidencia relativa a esta pausa insólita. Se ha escrito bastante acerca de la depresión en que Lorca cayó durante el verano de 1928, pero mucho menos sobre su continuación en 1929. Al ensamblar las diversas fuentes podemos entender la espiral descendente en que se encontraba Lorca y cómo surgió el proyecto de visitar Estados Unidos.
Rafael Cansinos Assens desempeñó un papel clave en la fundación y el lanzamiento del movimiento ultraísta, y durante sus primeros años de existencia lo apoyó con entusiasmo. Sin embargo, gradualmente ...se desilusionó y se distanció del grupo, llegando a escribir la novela satírica El movimiento V.P. en 1921. En sus escritos periodísticos posteriores, de 1922 a 1929, vuelve sobre el tema del ultraísmo con frecuencia, y aquí manifiesta actitudes dispares, con algunas notas de nostalgia, pero principalmente la neutralidad de un historiador objetivo o la negatividad de un crítico adverso. El análisis de este corpus demuestra que no existe ninguna correlación cronológica entre la actitud adoptada y la fecha de la columna, lo que deja al lector con la impresión de una profunda ambivalencia en la perspectiva de Cansinos. Además, se nota que intenta reivindicar su propia actuación dentro del movimiento al insistir en los logros posteriores del «ultraísmo argentino».
Human gut microbes exhibit a spectrum of cooperative and antagonistic interactions with their host and also with other microbes. The major
host-targeting virulence factor, Bacteroides fragilis toxin ...(BFT), is produced as an inactive protoxin by enterotoxigenic B. fragilis strains. BFT is processed by the conserved bacterial cysteine protease fragipain (Fpn), which is also encoded in B. fragilis strains that lack BFT. In this report, we identify a secreted antibacterial protein (fragipain-activated bacteriocin 1 Fab1) and its cognate immunity protein (resistance to fragipain-activated bacteriocin 1 RFab1) in enterotoxigenic and nontoxigenic strains of B. fragilis. Although BFT and Fab1 share no sequence identity, Fpn also activates the Fab1 protoxin, resulting in its secretion and antibacterial activity. These findings highlight commonalities between host- and bacterium-targeting toxins in intestinal bacteria and suggest that antibacterial antagonism may promote the conservation of pathways that activate host-targeting virulence factors.
The human intestine harbors a highly complex microbial community; interpersonal variation in this community can impact pathogen susceptibility, metabolism, and other aspects of health. Here, we identified and characterized a commensal-targeting antibacterial protein encoded in the gut microbiome. Notably, a shared pathway activates this antibacterial toxin and a host-targeting toxin. These findings highlight unexpected commonalities between host- and bacterium-targeting toxins in intestinal bacteria.
Multiple human diseases ensue from a hereditary or acquired deficiency of iron-transporting protein function that diminishes transmembrane iron flux in distinct sites and directions. Because other ...iron-transport proteins remain active, labile iron gradients build up across the corresponding protein-deficient membranes. Here we report that a small-molecule natural product, hinokitiol, can harness such gradients to restore iron transport into, within, and/or out of cells. The same compound promotes gut iron absorption in DMT1-deficient rats and ferroportin-deficient mice, as well as hemoglobinization in DMT1- and mitoferrin-deficient zebrafish. These findings illuminate a general mechanistic framework for small molecule–mediated site- and direction-selective restoration of iron transport. They also suggest that small molecules that partially mimic the function of missing protein transporters of iron, and possibly other ions, may have potential in treating human diseases.
Electron beams with helical wavefronts carrying orbital angular momentum are expected to provide new capabilities for electron microscopy and other applications. We used nanofabricated diffraction ...holograms in an electron microscope to produce multiple electron vortex beams with well-defined topological charge. Beams carrying quantized amounts of orbital angular momentum (up to 100Planck's over 2pi) per electron were observed. We describe how the electrons can exhibit such orbital motion in free space in the absence of any confining potential or external field, and discuss how these beams can be applied to improved electron microscopy of magnetic and biological specimens.
Emerging infectious diseases (EIDs) pose threats to conservation and public health. Here, we apply the definition of EIDs used in the medical and veterinary fields to botany and highlight a series of ...emerging plant diseases. We include EIDs of cultivated and wild plants, some of which are of significant conservation concern. The underlying cause of most plant EIDs is the anthropogenic introduction of parasites, although severe weather events are also important drivers of disease emergence. Much is known about crop plant EIDs, but there is little information about wild-plant EIDs, suggesting that their impact on conservation is underestimated. We conclude with recommendations for improving strategies for the surveillance and control of plant EIDs.
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