Validation of a Retrospective Computing Model for Mortality Risk in the Intensive Care Unit.

Objective: To compare the predictive performance of Epic Systems Corporation's proprietary intensive care unit (ICU) mortality risk model (IMRM) with that of the Acute Physiology and Chronic Health Evaluation (APACHE) IV score.

Methods: This is a retrospective cohort study of patients treated from January 1, 2008, through January 1, 2018. This single-center study was performed at Mayo Clinic (Rochester, MN), a tertiary care teaching and referral center.

Crystal nucleation and near-epitaxial growth in nacre.

Nacre is the iridescent inner lining of many mollusk shells, with a unique lamellar structure at the sub-micron scale, and remarkable resistance to fracture. Despite extensive studies, nacre formation mechanisms remain incompletely understood. Here we present 20-nm, 2°-resolution polarization-dependent imaging contrast (PIC) images of shells from 15 mollusk species, mapping nacre tablets and their orientation patterns.

Phase transitions in biogenic amorphous calcium carbonate.

Crystalline biominerals do not resemble faceted crystals. Current explanations for this property involve formation via amorphous phases. Using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), here we examine forming spicules in embryos of Strongylocentrotus purpuratus sea urchins, and observe a sequence of three mineral phases: hydrated amorphous calcium carbonate (ACC · H(2)O) → dehydrated amorphous calcium carbonate (ACC) → calcite.

Mollusk shell nacre ultrastructure correlates with environmental temperature and pressure.

Nacre, or mother-of-pearl, the tough, iridescent biomineral lining the inner side of some mollusk shells, has alternating biogenic aragonite (calcium carbonate, CaCO(3)) tablet layers and organic sheets. Nacre has been common in the shells of mollusks since the Ordovician (450 million years ago) and is abundant and well-preserved in the fossil record, e.g.

Mechanism of calcite co-orientation in the sea urchin tooth.

Sea urchin teeth are remarkable and complex calcite structures, continuously growing at the forming end and self-sharpening at the mature grinding tip. The calcite (CaCO(3)) crystals of tooth components, plates, fibers, and a high-Mg polycrystalline matrix, have highly co-oriented crystallographic axes. This ability to co-orient calcite in a mineralized structure is shared by all echinoderms.