Subtle structural details of siliceous zeolites are probed by using two-bond scalar (J) coupling constants to characterize covalently bonded 29Si-O-29Si site pairs and local framework order. Solid-state two-dimensional (2D) 29Si{29Si} NMR measurements and first-principles calculations of 2J(29Si-O-29Si) couplings shed insights on both the local structures of siliceous zeolites Sigma-2 and ZSM-1...

Objectives It has been known for centuries that crystalline silica induces silicosis. However, there are different entities of crystalline silica. Siliceous earth is a worldwide unique blend of amorphous and cryptocrystalline silica and lamellar kaolinite. This retrospective cohort study is the first that investigated the silicosis risk of siliceous earth. Methods The cohort consists of employe...

Electrostatic potential (EP), electric field (EF), and electric field gradient (EFG) values are calculated in periodic models of magnesium substituted phillipsite (MgPHI) zeolite forms using periodic DFT (PDFT) hybrid B3LYP level with fourteen different basis sets. Relative root mean square differences between the EP, EF, or EFG values estimated between different basis sets are evaluated in sev...

hydrothermal alteration processes are extensively took place on volcanic and pyroclstics of takestan area. existence of abundant, deep fracturing and subvolcanic intrusions are enhanced extend hydrothermal alteration zones. the following alteration zones are determined: propylitic, argillic, advanced argillic and sillicic. there are outcropped and widespread in different size and limit. formati...

Anaerobic methanotrophic archaea (ANME) play a significant role in global carbon cycles. These organisms consume more than 90% of ocean-derived methane and influence the landscape of the seafloor by stimulating the formation of carbonates. ANME frequently form cell consortia with sulfate-reducing bacteria (SRB) of the family Deltaproteobacteria. We investigated the mechanistic link between ANME...

Subtle structural details of siliceous zeolites are probed by using two-bond scalar (J) coupling constants to characterize covalently bonded Si–O–Si site pairs and local framework order. Solid-state two-dimensional (2D) Si{Si} NMR measurements and first-principles calculations of J(Si–O–Si) couplings shed insights on both the local structures of siliceous zeolites Sigma-2 and ZSM-12, as well as...

The opoka is a carbonate-siliceous marine sedimentary rock, forming thick succession of Upper Cretaceous age in Poland and other regions Europe. This rock has been studied for over 150 years, but only the use modern analytical techniques enables formulation its mineralogical definition, which identifiesthe distinct features allows it to be distinguished from rocks (e.g. chalk, gaize). Parallel ...