Quantum Aspects of Massive Gravity II: Non-Pauli-Fierz Theory

We investigate the non-Pauli-Fierz(nPF) theory, a linearized massive gravity with a generic graviton mass term, which has been ignored due to a ghost in its spectrum and the resultant loss of unitarity. We first show that it is possible to use the Lee-Wick mechanism, a unitarization through the decay of a ghost, in order to handle the sixth mode ghost of nPF, and then check for the quantum consistency. Once proven to be consistent, nPF could become a viable candidate for a large distance modification of gravity, because it naturally solves the intrinsic problems that most dark energy/modified gravity models suffer from: It smoothly converges to general relativity at short distances, and the small graviton mass necessary to modify gravity at large scales can be stable under the radiative corrections from the minimal gravity-to-matter coupling.Comment: 1+16pp, accepted for JHE

Learning Contextualized Document Representations for Healthcare Answer Retrieval

We present Contextual Discourse Vectors (CDV), a distributed document representation for efficient answer retrieval from long healthcare documents. Our approach is based on structured query tuples of entities and aspects from free text and medical taxonomies. Our model leverages a dual encoder architecture with hierarchical LSTM layers and multi-task training to encode the position of clinical entities and aspects alongside the document discourse. We use our continuous representations to resolve queries with short latency using approximate nearest neighbor search on sentence level. We apply the CDV model for retrieving coherent answer passages from nine English public health resources from the Web, addressing both patients and medical professionals. Because there is no end-to-end training data available for all application scenarios, we train our model with self-supervised data from Wikipedia. We show that our generalized model significantly outperforms several state-of-the-art baselines for healthcare passage ranking and is able to adapt to heterogeneous domains without additional fine-tuning.Comment: The Web Conference 2020 (WWW '20

Heterogeneity in Expectations, Risk Tolerance, and Household Stock Shares: The Attenuation Puzzle

This article jointly estimates the relationship between stock share and expectations and risk preferences. The survey allows individual-level, quantitative estimates of risk tolerance and of the perceived mean, and variance of stock returns. These estimates have economically and statistically significant association for the distribution of stock shares with relative magnitudes in proportion with the predictions of theories. Incorporating survey measurement error in the estimation model increases the estimated associations 2-fold, but they are still substantially attenuated being only about 5% of what benchmark finance theories predict. Because of the careful attention in the estimation to measurement error, the attenuation likely arises from economic behavior rather than errors in variables

A High Voltage Aqueous Zinc???Organic Hybrid Flow Battery

Water-soluble redox-active organic molecules have attracted extensive attention as electrical energy storage alternatives to redox-active metals that are low in abundance and high in cost. Here an aqueous zinc???organic hybrid redox flow battery (RFB) is reported with a positive electrolyte comprising a functionalized 1,4-hydroquinone bearing four (dimethylamino)methyl groups dissolved in sulfuric acid. By utilizing a three-electrolyte, two-membrane configuration this acidic positive electrolyte is effectively paired with an alkaline negative electrolyte comprising a Zn/[Zn(OH) 4 ] 2??? redox couple and a hybrid RFB is operated at a high operating voltage of 2.0 V. It is shown that the electrochemical reversibility and kinetics of the organic redox species can be enhanced by an electrocatalyst, leading to a cyclic voltammetry peak separation as low as 35 mV and enabling an enhanced rate capability

Ni single atoms on carbon nitride for visible-light-promoted full heterogeneous dual catalysis

Visible-light-driven organic transformations are of great interest in synthesizing valuable fine chemicals under mild conditions. The merger of heterogeneous photocatalysts and transition metal catalysts has recently drawn much attention due to its versatility for organic transformations. However, these semi-heterogenous systems suffered several drawbacks, such as transition metal agglomeration on the heterogeneous surface, hindering further applications. Here, we introduce heterogeneous single Ni atoms supported on carbon nitride (NiSAC/CN) for visible-light-driven C-N functionalization with a broad substrate scope. Compared to a semi-heterogeneous system, high activity and stability were observed due to metal-support interactions. Furthermore, through systematic experimental mechanistic studies, we demonstrate that the stabilized single Ni atoms on CN effectively change their redox states, leading to a complete photoredox cycle for C-N coupling. © 2022 The Royal Society of Chemistry.11Nsciescopu