In the field of microbial biomineralization, much of the scientific attention is focused on processes carried out by prokaryotes, in particular bacteria, even though fungi are also known to be involved in biogeochemical cycles in numerous ways. They are traditionally recognized as key players in organic matter recycling, as nutrient suppliers via mineral weathering, as well as large producers o...

Coccolithophore contributions to the global marine carbon cycle are regulated by the calcite content of their scales (coccoliths) and the relative cellular levels of photosynthesis and calcification rates. All three of these factors vary between coccolithophore species and with response to the growth environment. Here, water samples were collected in the northern basin of the South China Sea (S...

Synchronized transitions in the polymorph mineralogy of the major reef-building and sediment-producing calcareous marine organisms and abiotic CaCO3 precipitates (ooids, marine cements) throughout Phanerozoic time are believed to have been caused by tectonically induced variations in the Mg/Ca ratio of seawater (molar Mg/Ca>2=“aragonite seas”, <2=“calcite seas”). Here, I assess the geological e...

It is widely accepted that Vikings used sun-compasses to derive true directions from the cast shadow of a gnomon. It has been hypothesized that when a cast shadow was not formed, Viking navigators relied on crude skylight polarimetry with the aid of dichroic or birefringent crystals, called "sunstones." We demonstrate here that a simple tool, that we call "shadow-stick," could have allowed orie...

Abstract The Southern Permian basin in central Europe contains a number of important high-grade sediment-hosted Cu deposits. Laterally extensive stratabound and Zn-Pb sulfide mineralized rocks are located at major stratigraphic redox boundary, where coarse-grained continental sandstones the uppermost Rotliegend Group overlain by carbonaceous mudstones (T1) limestones (Ca1) Zechstein Formation. ...

This paper describes a modeling-control paradigm to control the hippocampal output (CA1 response) for the development of hippocampal prostheses. In order to bypass a damaged hippocampal region (e.g., CA3), downstream hippocampal signal (e.g., CA1 responses) needs to be reinstated based on the upstream hippocampal signal (e.g., dentate gyrus responses) via appropriate stimulations to the downstr...

this study investigates the influence of some chemical additives such as methanol, ethanol, sodium oleat, chloroform and sodium hexametaphosphate (shmp) on the dry fine grinding of calcite (x50= 33 µm) using a stirred media mill. the experiments were carried out by a batch operation, and the change in colour properties (ry, whiteness and yellowness) of calcite powder. the results showed that th...

A comparison of the physical-chemical properties of precipitated calcium carbonate (PCC), prepared by batch and semicontinuous processes, is presented. In both processes, PCC, was synthesized by carbonation of slaked lime. In the batch process the experiments were performed by varying the initial mass concentration and temperature, and the semicontinuous process was conducted by varying the ini...

Fluid-inclusion measurements and textural relationships demonstrate that coarse-grained quartz and calcite from the upper part of The Geysers thermal system formed during the transition from liquid-dominated conditions to the modern vapor-dominated regime. The most diagnostic characteristics of these transition assemblages are: 1) evidence of quartz dissolution; 2) contemporaneous trapping of h...