An Introduction to Proximal Causal Learning

A standard assumption for causal inference from observational data is that one has measured a sufficiently rich set of covariates to ensure that within covariate strata, subjects are exchangeable across observed treatment values. Skepticism about the exchangeability assumption in observational studies is often warranted because it hinges on investigators' ability to accurately measure covariates capturing all potential sources of confounding. Realistically, confounding mechanisms can rarely if ever, be learned with certainty from measured covariates. One can therefore only ever hope that covariate measurements are at best proxies of true underlying confounding mechanisms operating in an observational study, thus invalidating causal claims made on basis of standard exchangeability conditions. Causal learning from proxies is a challenging inverse problem which has to date remained unresolved. In this paper, we introduce a formal potential outcome framework for proximal causal learning, which while explicitly acknowledging covariate measurements as imperfect proxies of confounding mechanisms, offers an opportunity to learn about causal effects in settings where exchangeability on the basis of measured covariates fails. Sufficient conditions for nonparametric identification are given, leading to the proximal g-formula and corresponding proximal g-computation algorithm for estimation. These may be viewed as generalizations of Robins' foundational g-formula and g-computation algorithm, which account explicitly for bias due to unmeasured confounding. Both point treatment and time-varying treatment settings are considered, and an application of proximal g-computation of causal effects is given for illustration.

The Fragmented Frame 1

The aesthetic of the fragment is examined in detailed analyses of the Hitchcockian frame. The frame is both the formal composition underpinning mise en scène and the opening into the infinite play of fragmented images within visual, aural, and narrative form. The frame is a site of formal “expressivity,” “abstraction,” “topographic representation,” and “schematization.” The fragmented frame is revealed in the modernist experimentation of form through color, line, and shape in North by Northwest, the topographic frame in The Birds, and the canting of the visual frame in Shadow of a Doubt. The chapter concludes that the representational image forming the diegesis is overwhelmed in Hitchcock’s experimental works by the formal potential of abstract shape and pattern.

Photography

This bibliography reflects the multifaceted relationship between Latina/os and various photographic traditions. As individuals and groups placed in front of the camera lens, Latino/as have often found themselves stigmatized, marginalized, or criminalized. Photographs taken by reformers, the police, and documentarians since the late 19th century, for instance, have often generated harmful or homogenizing visions of the US Latina/o population that frame them as racially different or otherwise problematic. Since the early decades of the 20th century, however, Latino/a photographers have produced bodies of work that challenge these limited visions to craft new images of identity, community, and history. Some of these individuals have harnessed the capacity of photography to fulfill an evidentiary or realist function as either social documentation, a political organizing tool, or a challenge to exclusionary mainstream media coverage. Others have explored the aesthetic and formal potential of photography by engaging in conceptual art practices, crafting speculative reimaginings of history, using it as an extension of performance, integrating it into other media, or mobilizing it as a complex mechanism of community- or self-representation. This bibliography covers the major works of scholarship that have attended to these key photographic tendencies and the places where they overlap, considering works that discuss Latina/os both in front of and behind the lens. Also included here are key exhibition catalogues and photographic essays that provide a representative sampling of visual tendencies or traditions mobilized by practicing Latina/o photographers, with particular attention to regional and ethnic diversity.

Tuning the formal potential of ferrocyanide over a 2.1 V range

Coordination of tris(pentafluorophenyl)borane to hexacyanoferrate shifts the formal potential by over 2.1 V while maintaining electrochemical reversibility.

Laminar ceilings? Shell construction in the work of some masters of modern architecture

This contribution explores the constructive and formal potential of the laminar structures in the work of three prominent figures of Modern Architecture. Unlike the most memorable constructions of this type, the roof structures here considered are not the main and only protagonist element of the building. Conversely in these cases they have been designed as parts of the building more inconspicuous and integrated. The study excludes therefore the most important realizations and also more known, made by authors as Maillart, Candela, Isler, Torroja, Saarinen, Niemeyer, etc. which have been widely treated in the specialized literature. The paper is focused in architects as Le Corbusier, Alvar Aalto and Louis Kahn, for whom the study of their approach to the laminar seems not to have been made adequately as a whole till now. Are important too, the considerations resulting from the comparative analysis, shedding some light on the idiosyncratic way in which this type of structures was adopted by each architect.ResumenEn este artículo se explora el empleo realizado por tres figuras destacadas de la arquitectura moderna de la potencialidad formal y constructiva de las estructuras laminares. A diferencia de como ocurrió en la mayoría de las construcciones memorables de este tipo, la estructura de cubierta no es necesariamente el gran y único elemento protagonista, proyectándose más bien por el contrario, como partes del edificio más discretas e integradas. Se excluyen, por tanto, las realizaciones más importantes, pero también más conocidas, de autores como Maillart, Candela, Isler, Torroja, Saarinen, etc. ya ampliamente tratadas en la literatura dedicada al tema. Contrariamente, en este trabajo se centra la atención en arquitectos como Le Corbusier, Alvar Aalto, Louis Kahn, cuya aproximación menos evidente a lo laminar entendemos que no ha sido en conjunto suficientemente tratada hasta ahora. Son importantes también las conclusiones derivadas de los análisis comparativos, las cuales arrojan alguna luz sobre las particulares formas en que se adoptó este tipode estructuras por cada arquitecto.

Designing strategies to tune reduction potential of organic molecules for sustainable high capacity battery application

The framework of density functional theory has been applied to predict the formal potential of 137 molecules and identify promising candidates for the application as the organic electrode of rechargeable batteries.

Sensory Properties of Polysulfone Hydrogel for Electro-Analytical Profiling of Vanadium and Selenium in Aqueous Solutions

Hydrogels have been a topic of extensive research because of their unique bulk and surface properties. They play a vital role in development of controlled release drug delivery systems. Polysulfone hydrogels are hydrophilic porous materials, which provide the advantage of biocompatibility and effective orientation of biomolecule in the design of the novel biosensors [1-2]. Polysulfone hydrogels may be prepared as water swellable powders or drop cast as thin films on screen printed carbon electrodes (SPCE). Polysulfone hydrogels produce electroactive thin films, characterized by 2 well resolved redox peaks, with a formal potential of 0.0867 V and diffusion coefficient in aqueous medium of 9.06e-9 Cm2/s. In this paper we report on the initial speciation studies and analytical performance of Selenium and Vanadium at the hydrogel electrodes, as evaluated by using cyclic voltammetry in a range of -0.7 V to +0.0 V versus Ag/AgCl. The morphology, adsorption and thin film integrity was evaluated using High resolution scanning electron microscopy (HR-SEM), UV-Vis and Raman spectroscopy.