(Transition metals) may be incorporated into (silica matrices).Logical formLearned from2 sentences. Chlorides of erbium may be copolymerised with silica.Logical formLearned from2 sentences. Boron may be incorporated into (gelling silica systems).Logical formLearned from2 sentences. Sites can be on a surface of (silica optics).Logical formLearned from2 sentences. A (silica by-product) can be marketable.Logical formLearned from2 sentences. A technology can be for extracting silica.Logical formLearned from2 sentences. Silica can be a material.Logical formLearned from2 sentences. An alloy can be constituted-of-or-filled-with silica.Logical formLearned from2 sentences. Bits can be constituted-of-or-filled-with silica.Logical formLearned from2 sentences. Silica can be above a permissible (exposure limit).Logical formLearned from2 sentences. Employees may be overexposed to (silica dust).Logical formLearned from2 sentences. A (silica overexposure) can be alleged.Logical formLearned from2 sentences. A (quartz silica) can be crystalline.Logical formLearned from2 sentences. A silica can be available through a site.Logical formLearned from2 sentences. An overexposure can be to silica.Logical formLearned from2 sentences.