You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Rare-variant genome-wide association studies: a new frontier in genetic analysis of complex traits. Genome-wide association studies have, in the last few years, identified thousands of common genetic variants associated with common complex traits and diseases, implicating many genes not previously known to be involved in the biology of those traits. However, these variants have so far explained little of the population variance in trait values or disease susceptibility. As large-scale genome sequencing efforts have revealed the extent of genetic variation at the low end of the frequency range in human populations, the effects of rare variants have been proposed as an explanation of the 'missing genetic variance.' Improved technologies for genotyping rare variants, including inexpensive whole-genome and whole-exome sequencing and rare-variant genotyping chips, coupled with novel analytical methods, are making genome-wide scans for the effects of rare variants possible, and seem likely to usher in a new era in the genetic analysis of complex traits.
{"Chemical": []}