Logical Reasoning is a novel approach to deal with challenging Machine Reading Comprehension tasks by utilizing the ability to construct logical structures in natural language.However, previous promising studies struggle with the accuracy of logical unit division and the consistency of model prediction on equivalent semantics.In this paper, we propose ThinkStruct, a new method that leverages a transformer network enhanced with the information of Rhetorical Structure (RS) relations for logical reasoning.Specifically, our method uses Rhetorical Structure Theory (RST) to split natural language text into Elementary Discourse Units (EDUs) and identify the relationship among these units.Node information is then fed into the fully connected transformer network, which is enhanced with logical relationships among the extracted units via adjacency matrix.Subsequently, the features of the transformer network are integrated before being passed into the answer prediction module.In addition, we employ a contrastive learning module for improving its understanding of the relationship between Elementary Discourse Units.Our experiments on the LogiQA and Reclor datasets demonstrate that our results outperform other state-of-the-art models.E1: If a mechanical aerator is installed in a fish pool, E2: the water in the pool can be properly aerated. E3:

Spam is a problem that refuses to go away. An immense amount of time and money is currently devoted to hiding spam, but not enough is devoted to effectively preventing it. CAPTCHAs are a prevalent spam prevention mechanism, but are getting harder for humans to solve and easier for programs to "break". CAPTCHAs also cannot prevent spam from hijacked accounts since they are mostly used during account creation. Proof-of-work approaches are gaining popularity, but current implementations are not effective enough and cannot be used by generic web applications. We present MetaCAPTCHA, an application-agnostic spam prevention service for web applications. MetaCAPTCHA dynamically issues CAPTCHAs and proof-of-work "puzzles" while ensuring that more malicious users solve "harder" puzzles. In order to support its operation, MetaCAPTCHA implements a novel secure protocol -- for authenticating web sites and validating proof-of-work solutions -- that allows for seamless integration across a variety of web applications.