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:

Lipid composition of Chlorella vulgaris (Trebouxiophyceae) as a function of different cadmium and phosphate concentrations. Fatty acids are the fundamental structural components of membrane lipids, and the degree of saturation of the long hydrocarbon chains in microalgae contributes to regulation of growth, biomass production and reproduction of aquatic consumers. This research aimed at evaluating the effects of cadmium (2×10(-8); 10(-7) mol L(-1) Cd) on lipid class and fatty acid composition of the microalga Chlorella vulgaris under varying phosphate (PO(4)(3-)) concentrations (6.0×10(-7) to 2.3×10(-4) mol L(-1)). Under PO(4)(3-) limitation and Cd stress, the storage lipid class triacylglycerol (TAG) was the most accumulated among the lipid classes. Fatty acid composition revealed that the degree of saturation increased with increasing Cd stress and PO(4)(3-) limitation. Decreasing PO(4)(3-) and increasing Cd concentrations resulted in higher saturated fatty acid (SAFA) and monounsaturated FA (MUFA) concentrations. Total polyunsaturated FA (PUFA) and ω3 PUFA, and PUFA:SAFA ratios were higher in the control (2.3×10(-4) mol L(-1) PO(4)(3-)) cells than in either PO(4)(3-) limitation or Cd stress, or in the combination of both stresses. Contrasting with all the other PUFAs, 18:2n - 6 increased as PO(4)(3-) limitation increased. A significant positive relationship of PUFAs, acetone mobile polar lipids (AMPL) and phospholipids (PL) with phosphate concentration in the culture media was obtained, while TAG concentrations had a positive association with total MUFA and SAFA. Total SAFA, 14:0, 18:1n - 9 and 18:2n - 6 were positively correlated with Cd and negatively with PO(4)(3-) concentrations. The microalga responded to combined PO(4)(3-) limitation and Cd exposure by increasing its total lipid production and significantly altering its lipid composition. The FA 18:2n - 6 may be considered a stress biomarker for PO(4)(3-) limitation and Cd stress in C. vulgaris.
{"Chemical": ["hydrocarbon", "cadmium", "MUFA", "\u03c93 PUFA", "Cd", "acetone", "phosphate", "triacylglycerol", "Fatty acid", "fatty acid", "polyunsaturated FA", "TAG", "SAFA", "PO(4)(3-)", "monounsaturated FA", "PUFAs", "Fatty acids", "saturated fatty acid", "PUFA"]}